Japanese N/A L6 400hp, how they do it, pictures I've found, etc. Not 56k safe

[jc052685]

How depressing.

 

Link = right click on photo >>> properties >>> url for photo >>> cut off unwanted bits >>> ???? >>> win: http://www.as-watanabe.com under the "works" tab.

 

Was coming to post the link lol

 

 

http://www.as-watanabe.com/

[Tony D]

I got some 'hybridz' based link like someone posted them on the board then linked them. Odd. It seems to be working now from either source.

 

Give me SOME credit! I'm "Mr. Stolen Website Lurker" of the first degree when it comes to posted photos. I cringe when I see someone washed them like a lot of mine are: downloaded and then uploaded and show as 'hybrid' links only!

[Tony D]

Well, something else just got put on the 'to do list' for the visit in February...

[josh817]

Lol I lurk around all the time... Firefox lets you view page info and page source, for your creep/stalker needs.

 

I tend to download and then upload images so I don't hotlink images and eat their bandwidth up every time someone views the thread.

[neotech84]

Some very interesting videos!

 

shows head stamp! around 2:40

 

 

 

 

 

Other cool

 

edit: Don't post a quick message right befor you get off work......... they usually don't make sence.

Edited November 6, 2010 by neotech84

[Tony D]

CRAP! It has been confirmed, I was about 20 minutes from CS Wantanabe. It's right around the corner from the Factory where I visit every three months.

 

Okamura-San has drawn the proper conclusion from my inquiring e-mail:

"this goes on visit list for next arrival?"

[MONZTER]

just because it says N-42 doesnt mean it is stock. A lot can be done with a welder and a die grinder. Only the builders of these beautiful engines will know the real secrets, we can only try until we master it ourselves

[JohnH]

"Lol this again.

 

To say the least, the little cone nozzle thing was actually just a baffle to quiet the car down since apparently they drive them around a little too. For the cranks, mill 6mm off the back flywheel flange (don't mill where the pilot bearing goes... please) and then drill and tap the flywheel bolt threads deeper. I would also put 2 more dowels so you have a total of 3 on the back. The front of the crank snout is modified to use 1 big key instead of 3 small keys. I believe this keeps them from walloping out. You can see in the picture of the crank they show it. At first I was like what the hell are they trying to show and then I read more about it. I'm not sure how they go about putting one huge key in the crank though... Is it just a steel piece that they tap in?"

 

After reviewing this thread again to see if there was anything new added, I was doing a search on the net for Japan based S30 products. I came across this link that says it all regarding "exhaust nozzels".

 

http://www.rhdjapan.com/nissan/s30-fairlady-z/silencers-ecvs

 

As stated in this thread either in obvious print or between the lines, the 400hp n/a power Japan biulders are making is based on a stroker with good $$$$ head work, matching cam & induction system. No secret - except for the finesse craftsman details. There is absolutely no reason anyone outside of Japan cannot replicate this without some $$$$, patience & R&D on their own. The Brad Frissele race car is reported to produce 400HP & that is on GTU engine specs.

[zredbaron]

EDIT - post removed; it wasn't a complete post. Was supposed to click on Preview.

Edited February 12, 2011 by zredbaron

[zredbaron]

First of all, wow, this is a wonderful thread Josh, thank you for the tremendous time and thought you've put into this, and to all who have contributed. I've come a long way over the years thanks to HybridZ, but I'm still learning, and like many of us have an insatiable thirst for maximum performance, both theoretically and practically.

 

That said, I'm just stumbling on this thread now, and my big-picture conclusion with the mythical JDM 400hp dragsters is that they're more hype than hope. I don't doubt that they may edge more ultimate hp out than our own L6s, but agree our road racing and autocross engines are built for area under the curve. I would have to see their engine on the dyno right after I saw an established engine on the same dyno, same day in order to believe 400hp with gasoline @ 12:1. It's too good! That would be nearly 130 hp/L! The Ferrari Enzo produces 110 hp/L with similar fuel/compression at 7800rpm. I just don't see the VE of 2 valves per cylinder with carbs and premium gas going against an Enzo's VE. Need to see that one in person, or hear from those who have.

 

I agree with others that have defended the reasons development goes in certain directions or doesn't. ZR8ED, had some great VE comments, concur. Ultimately I would never want a JDM motor for a bunch of reasons, but this isn't about that. Yet.

 

For shared knowledge purposes, I'd like to point out how similar my Jim Thompson / Sunbelt head is to some of the JDM head info you compiled. We agree power is made in the head, so let's start there. To my knowledge Jim no longer does L6s but works on BMWs. Sunbelt no longer exists, but merged with Kinetic Motorsports. I feel no moral obligation against sharing my head's information; I bought the head, I bought the cam. I'm allowed to share what I know about it if I want to, maybe other members with fancy heads from shops other than Sunbelt feel the same way...

 

Disclaimer: I'm someone who got incredibly lucky and fell in line about seven years ago behind JohnC, who paid for serious R&D for his N42. I'm not an engine builder, however I do have some data about the E31 head Jim built for me. Also, I know there are other L6s builders out there, and I nothing of how they build heads or cams. Just sharing the one I own. And a lot of hot air.

 

Some basic things I've gathered were:

-N42 base head

-welded chambers to 36cc

-46/38 valves

-HUGE ports that don't do anything for you until you're high up the the RPM range

-intake ports must see at least 220 CFM for this sort of power

-exhaust must see at least 150 CFM

 

HEAD:

-early E31 in style of JohnC's N42

-37cc chambers

-44mm/35mm valves

-pictures of ports below, very different around valve guides

-208/134cfm in/ex @ .565" lift (recently tested, no details on bench)

-202/145cfm in/ex @ .525" lift (according to Sunbelt as shipped, Flow Prow bench) Also according to Sunbelt: "200cfm on a Flow Prow bench is 225cfm on a Super Flow bench." I know nothing!

 

These pics are from 2004 when I received the head from Sunbelt. Note how different the combustion chamber shape is (E31 head) with similar cc numbers. Also note how different his valve guide approach is.

 

 

 

I also add that this cam is designed with a single set of springs (outer only) whose length is between that of typical inner and outer springs. This cam is profiled specifically for these springs and uses 25% less seat pressure. Or so I'm told. So that's a variable.

 

Also note the texture isn't shiny. It's my understanding that polished actually increases surface friction, and a slightly textured surface has less drag (head loss) along the surface of the ports (dimpled golf ball effect). I'm surprised the JDM heads are so shiny. (Seems to me the old SSS / Nissan Competition valves were "swirled" for this very reason.)

 

Okay so obviously the main difference thus far is port profile, texture, valve size, valve guides and peak flow numbers. And seat pressure. Lol. Isn't that just about everything except the cam!?

 

The cams these guys run are a lower lift than the big typical Schneider cams, they run about .530"-ish of valve lift[i just received an email from someone saying that the lift is "huge" so I think this .530" lift is too small. It is however the cam size that the Australian guy was running]. Their duration, at least the cam for this guy, was only 241º @ .050" for exhaust and 251º @ .050" for intake. This is the smaller cam that the dude had purchased, because his car came with a monster Japanese cam. I would think there would be a little more duration to bump that power band into 7-9000 RPM range, and they run LOTS of overlap. That's why I think the Kameari exhaust pieces are something special, because these guys are running tons of overlap, I think that tells us that they are relying on the scavenging effect.

 

.530" lift isn't necessarily so small if your entire engine is tuned for it... JohnC had .534" lift, Dan Baldwin had .550" lift in respective posts in 2004. Both Sunbelt-built, both powerhouse NA L6s. It isn't size that always counts, it's what you do with it. Or so I hear! Definitely not true with my tires!

 

Contrarily, I had .525" lift in a head built by Jim, and I only put down 195 whp at the time. Street performance intake and exhaust, street compression, poor fuel, etc. Rebuilt in '08 to 12:1, race cam, maxed-out 40 DCOEs, and race fuel and put down 264 whp. Still more out there. Same head all along.

 

Tune, tune, tune. For *your* head, for *how* the car will be used.

 

 

my 2nd Sunbelt cam:

.565" gross lift (Arbitrary? Nope! More on lift vs. flow below.)

seat duration is 326º/315º

.050" duration is 290º/275º

lobe separation angle 104º

Torque from 3500-7000

Power above 4000 (up to 7700, outer spring advertised maximum).

Asymmetrical lobe, 104º separation. Note that the exhaust lobes are more asymmetrical than the intake. Has nothing to do with minimizing overlap; it's just to sound cool. (Haha!)

 

I really hope this doesn't upset anyone. There's so much more to cams than basic specs. Any attempt to replicate would be a fail as far as I know.

 

 

 

I say 2nd cam because the head originally was originally delivered with a cam with .525" lift and 290º/275º total seat duration. Hmm.

 

I also very recently had my head flow tested. Different numbers than what Sunbelt provided (more on that in a bit). Here's a graph from the numbers I have this go-around:

 

 

Note that for Jim's port/polish, there is a diminishing lift performance between .550" and .600". Again, no coincidence, .565" lift peaks the flow chart. I'm not saying Jim Thompson is the only one who has built a head/cam this well tuned, but I am saying that it's been done on this side of the pond. Just not with their oversize++ valves and somewhat radical headers.

 

I would LOVE to know more about Dave Rebello's heads. I'd love to see pics of the ports, cfm numbers vs. lift, cam selection, etc. Suspension knowledge isn't proprietary, why does engine-building have to be? People are still going to go to well-recognized shops and order race motors to be built.

 

EXHAUST.

 

I honestly don't see how exhaust can come anywhere near supersonic speeds, no matter what kind of nozzle you create.

 

But damn, look at those headers! Haha! I mean look at the damn things, they look like a waterpark ride! Our race primaries are mandrel and equal length too, so what? When I saw the octopus headers my first thought is that they appear to have fairly equal angular-distanced primaries, too. (Total degrees of bending each pipe does, at the same radius even.) This allows about as equal / laminar flow as one could hope to achieve comparatively between six primaries. I'd like to have equal angular distance in my own headers, even if just for my own warm fuzzy, but I really don't see it making much difference except for WOT at higher RPMs.

 

I have yet to read an in-depth explanation of *why* 3-2-1 has better scavenging/torque than a 6-1. While the 6-1 might theoretically out-flow a 3-2-1 (less friction / head loss), the 3-2-1 will out-scavenge the 6-1. The only in-the-weeds thought I have is that in the 3-2-1 design, only 3 cyls are shared for a given collector. As the pressure wave reaches the merge point of these primaries, it sees a junction; an big pipe turn going the same direction down a 2.5" pipe AND two sharp u-turns backwards up the other two primaries toward the head. As the wave propagates past the merge point, low pressure is felt behind it, which is felt upstream toward the two exhaust valves via the other two primaries. This low pressure is shared by the two primaries. In the 6-1 design, this low pressure is shared by 5 primaries. 5 primaries, 4 strokes, you do the math... sometimes two valves are open vice one. It can't possibly scavenge as well in my mind. (I totally admit that I'd have to track out the 4-stroke cycle for all 6 cyls for verify the 3-2-1 setup never feels a pulse with two exhaust valves open. Not going to think that hard.)

 

Torque, not power, is affected most by scavenging, right? Then that's it. Drag racing doesn't care about torque as much as power. Ultimate peak flow potential. An octopus header is a work of art for WOT only. Road racing cares about torque. Autocross does even more. The street even more.

 

These Stahl header photos are courtesy JohnC. I believe in this pic they are 1 3/4" primaries (equiv of 45mm) for road racing applications. They run 45-48mm out there, we run ~42-45mm here for autocross / road racing respectively. Again, trend respective to how the motor is used.

 

 

 

Note the three dimensional reverse-coning on the left collector. Looks similar to cyclone shapes on some household vacuums. Not to be confused with cyclones, this air isn't spinning, but note the gradual coning / venturi effect. Very nice.

 

 

 

 

 

You can see these deliver two 2.5" collectors. I don't have it in hand yet, but JohnC is sending me a custom merge collector that sounds pretty damn cool (there's still one more merge with a 3-2-1 design of course). If I recall correctly, I wanna say it's a 20-degree merge angle (pretty steep!) where both 2.5" collectors merge to a single 2.5" pipe. At this point in time a pressure wave will scavenge the other collector tube, alternating strokes. Smooth. Then I think JohnC said it will even nozzle slightly (to narrower than 2.5") then expand to 3". He was very specific that this will be exactly 36"-38" or whatever it was from the exhaust valve. No idea why it was so specific, but I would theorize that it's the distance that draw torque out the most and was discovered experimentally. Perhaps he'll chime in.

 

From this point on (i.e. the middle of a 3" pipe), the 6-1 comes back strong. It's an exhaust race! Haha. No, seriously.

 

[in terms of transmitting a change in throttle position to the drivetrain, the 3-2-1 wins. In terms of ultimate WOT flow, the 6-1 wins.]

 

"And they're off!"

 

In the lead we have 3-2-1 that just seems to have been sucked away at tremendous speed by the previous stroke! It's hit a sharp bottle neck at this "merge collector" and now it's home-free with nothing but 6' of 3" mandrel pipe! 6-1 is way behind, BUT at this point from the exhaust valve both are traveling at the same speed (both are in 3" diameter pipe, similar displacement, similar head flow). The pulsing motor's exhaust is less dense (less time allowed for flow), therefore at steady state WOT, once both motors are up to speed, THEN AND ONLY THEN does the 6-1 design win the race. It has fluid density. The exhaust is traveling at the same speed as the 3-2-1 at this point, and it nears the muffler then it accelerates out.

 

I have a theory for their velocity nozzle muffler, but I admit it doesn't quite feel complete. The revolver-style merge collector induces a rotation to the exhaust, right? Slightly cyclonic? Whirlpools flow faster than pulsing bubbles. Watch your bathtub empty itself and you'll see a whirlpool. They're whirl-pooling their exhaust, and this effect only takes place at steady state WOT... any transitions in throttle input will disrupt the flow enough to temporarily cause the flow through that funnel to be turbulent and run like crap. This ONLY would be applicable to a cyclonic exhaust flow, which would only be created from a 6-1 header with a revolver style collector. Again, I'm thinking this results in piss poor driveability / throttle response.

 

One might argue that the exhaust is going one-way (whereas with a whirlpool, water and air are trading places), and that a whirlpool would therefore be fruitless. However, it's pulsing don't forget, so the air in front of and behind the pressure waves do funny things, especially when narrow, and just might be happiest to swirl and not fight. Like the air and fluid in this picture.

 

 

Idiot check: what does Formula 1 do? Not a swirl!

 

 

After their graceful merge collector, they aren't swirling -- they're in the weeds fishing for aero crap (I would argue that hot gases will only piss off their wings -- but aero is another discussion!) Back to the point, they're doing aero stuff, NOT spiraling their exhaust and funneling it out some magical orifice. Neither is NHRA. That's all the common sense check I need... a magic exhaust tip will not make my car go faster. If it would, you would see spiraled headers on Top Fuel dragsters that look like Dyson vacuums! That kind of thinking (tips will make me go fast!) is what gives JDM / RICE a bad name in the first place.

 

And no Josh, that wasn't aimed at your theory. Basically I'm suggesting we have a comparable level of tuned exhaust performance they have across the pond; they are tailoring to peak flow/power and we are tailoring to scavenge for usable torque.

 

Whew! Man, that's about as much hot air as I've ever typed. By all means, please put me in my place if I'm out to lunch!

 

Found this video. Shows how much of a pig it is down low, as predicted, but god, does it that motor sound MAD! It's the red motor in the red S30 we've seen a few times in these JDM threads.

 

 

INTAKE:

Not much discussion, rightfully so. Pick the right intake to match the flow / usage of your head, tune it on the dyno, the end.

 

BOTTOM LINE, they are too far in the land of diminishing returns for my wallet. No one would dispute that our autocross and road race motors' area under the curve would have a tremendous advantage over the JDM dragster, which is how we use them. Put their motor in our cars for our events and we'd get beat for a lack of driveability! Reverse is also true of course, we would lose at the drag strip.

 

Note that the Kameari $6500 head claims 320hp, not 400. That looks like it has the potential to actually be a get-what-you-pay-for item, unlike the hardware. I'd like to know what Kameari claims that head, the one pictured, actually flows when delivered.

 

Okay fine, this thread is about the engine, not its use. They only use their best ~3000rpm power band at WOT and that *is* their purpose. Fine. On dyno day add up the *area* under each engine's best 3000rpm band and compare them (peak too, why not). I would claim that percentage-wise, on the same dyno on the same day, there would maybe be not more than 5% better numbers on the JDM best vs. our best, whatever L6 that would be. That's my claim, maybe that's me being an American and defending our ways, but it's also my honest assessment with what I think I know at the moment. One of us would have to skip the pond to find out. Hats off to them for their peak hp achievement, though! And God, I loved the sound in the video of the red Z on track!

 

Most people aren't willing to pay twice as much for a proven part in the search for that last bit of power. But hey, some people have too much money to spend. Luckily most of them go for "Porsh's."

 

For the rest of us, I agree Tony D, send the money to a shop like Rebello and wait for a crate. Best option I see at the moment.

 

Anyways, I'm rambling at this point and have probably embarrassed myself enough. I like my autocross motor, it's awesome. The end.

Edited February 13, 2011 by zredbaron

[Tony D]

Slovers is getting 218CFM on a stock intake valve...

I forget the exhaust number, but 165 seems to come to mind, and that was either on a stock or small oversized valve there.

 

Rebello was making similar numbers on stock valves. JeffP was kind of stupefied that he improved the numbers to what he has in his bigger-valved head on stock valves.

 

As Burton Brown in the #7770 Bonneville Car shows, the Rebello will make enough HP to punch a stock-bodied Z through the air to a point where the aerodynamic forces undisputably prove the 400 HP Claim. (That was the Red 240 on the salt I posted earlier in this thread.) And that doesn't take into account it's happening at 4400 ft elevation!!!

 

Proprietary stuff is the man's bread and butter. I know for a fact one engine builder in particular is really interested in what JeffP has on his head now.

 

When you can punch 400HP out on an Engine Dyno (say at 5500 rpms held for 5 minutes to check cooling performance)and have consistent oil temperatures, and consistent water temperatures, with no front to back difference on the temperature probes you start to realize, it's not making the power that is the key, you can do that with a turbo easily.

 

It's keeping the engine cool and consistently cool during the whole time of high-specific output. You keep it cool, it doesn't detonate.

[josh817]

Words of wise men, I say!

 

I feel like such a goof when this thread gets bumped back up because some if not a lot of the initial hypothesizing I posted wasn't true and I feel like a boob. The nozzle thing, I think I addressed later on in the thread (if anyone survived all the reading), it's only used as a silencer. Some of those guys drove their cars to the track, for instance the baby blue Z, so he used a nozzle.

 

I initialy thought the cyclone thing was worth something, then thought it was a bust, and from what you've said now I see it's worth something again! I found the explanation very interesting actually!

 

I have some input on port design however I'm not at home so I don't have any of my pictures. I will say however that carb porting and fuel injection porting is different, which I never knew until discussed in this thread:

http://forums.hybridz.org/index.php/topic/95308-bsr-gtu-e31-head-images/page__p__896640__fromsearch__1#entry896640

 

Further reading can be had from this link which discusses induction theory and how to calculate plenum size and runner length. As you were talking about the exhaust and pressure waves, and you worded it like it was a race, got the gears turning. Now I'm curious if you can use the same runner length formula but for your exhaust.

 

http://www.grapeaperacing.com/tech/inductionsystems.pdf

 

The formula essentially consists of

-speed of sound velocity at a given temp

-pipe diamter

-RPM where you want peak power

-cam duration

-number of pressure wave reflections

 

Everything is there to apply to exhaust. If the magic number for you was somewhere between 36-38" it MAY make sense. The thing I see throwing it off is velocity of the pressure wave since the exhaust is so hot, that value must be very high which makes the lenght very long... The only way to save it is to enter in a higher reflection value, but does the low pressure wave in an exhaust bounce back and forth...? Then again I read nothing in the "plenum" section of the article since my intake won't be running a plenum. Useful info may be in there.

 

Edited from a previous post I had made using the formula:

Cam duration: 300º

Pressure wave velocity: 1300ft/sec

Peak HP: 7000 RPM

Runner diameter: 1.8125"

Tuned to the 3rd wave yields 12.7" length. With a 310º duration it goes to 13.2". The write up says to subtract 20-30º from the total duration so with that said, this really only get's you into the ball park. The same goes for the other variables below.

 

1st and 2nd waves are apparently more prevalent but you need a substantially longer runner. With the same settings as posted above tuned to the 2nd wave the length jumps to 19.5" and the 1st goes to 40".

 

Another way to reduce tuned length is to lower the velocity of the pressure wave which is essentially the velocity of sound. The 1300ft/sec figure is at a 245ºF. If you could get the intake charge to 140º you would have a runner length of 11.7".

 

 

I'll have to reassess my entry when I get home.... AFTER I do my homework. You guys draw too much of my attention.

Edited February 13, 2011 by josh817

[zredbaron]

I initialy thought the cyclone thing was worth something, then thought it was a bust, and from what you've said now I see it's worth something again!

 

And on my end, now that I see how *ridiculously* long my post was (really?), I can't believe how bad we're theorizing this exhaust to death! Now that I re-read it, I wonder if it's just a bunch of hot air... whirlpooling exhaust seems like a bit of a stretch! Haha. I do still think the ultimate WOT volumetric flow rate of the octopus header will be measurably greater, just like it's torque band will be worse than that of a 3-2-1.

 

Also, to set the record straight, I wasn't suggesting proprietary secrets (wherever that line is drawn) be shared, in case it came across that way at all. I don't feel like anything I shared could be duplicated arbitrarily based on a pic and a couple numbers for a cam, and is therefore merely for discussion / comparison purposes.

 

Oh, and the 3-2-1 merge collector details (distance from exhaust valve, etc) should be taken with a large grain of salt since it was based on a single conversation with JohnC on the phone, and I may not be remembering it accurately. I sure as heck didn't design it, the point was that exhaust is as tunable as every other aspect of a car, unfortunately it's one setting only: installed.

 

Again, I'm a paying customer who enjoys learning about what he's doing to his engine, not someone who actually knows what they're talking about.

Edited February 13, 2011 by zredbaron

[zredbaron]

Wanted to update some of my posted head flow data and throw some additional "food for thought" in the mix.

 

I received the official printout from when I had my head flow tested, and it also included flow performance WITHOUT spark plugs installed. The previous (above) chart is how it flows WITH plugs installed. Note that these 'without' numbers bear a striking resemblance to other "all-out" head jobs. Also, I have no idea how deep the plugs were (they weren't my plugs), if they were indexed, etc. etc.

 

Here's the additional data, comparing WITH vs WITHOUT.

 

 

 

The food for thought is this: flow numbers should be taken with a grain of salt, just like dyno numbers. Numbers are somewhat arbitrary unless comparing head improvements on THE SAME BENCH with THE SAME AIR.

 

That is to say, unless specified, we don't know whose numbers have plugs and whose do not. We're also assuming flow pressure is the same (standard?). Pressure DOES NOT equal density, as humidity and temperature are very significant factors, and fluid density and composition will greatly vary airflow characteristics, even if on the same head and same bench.

 

Case in point, as I review my dyno plot, I notice that they turned the SAE correction OFF for the printout. I have the raw data files, so I now know the truth: my 264rwhp was a result of it being a cold day. The SAE corrected was 250rwhp, which is what I'll need to use when I return to the SAME DYNO once I get my car all back together. They obviously wanted me to see the bigger number, so they gave me the raw hp, not correcting for having good air that day (at sea level). I digress. Again.

 

And lastly, the head shop was *extremely* impressed with Jim Thompson's work. (Again, he no longer does L6s, sorry to say.) They were so impressed in fact, that they kept the head and studied it, photographed it, etc. in hopes of duplicating its flow concepts on future race heads (unknown type). They really went on and on about it. I'm sure there are other shops out there that still do this level of work (Rebello).

 

You usually really DO get what you pay for. If you don't curse that the price of your head costs as much / more than most complete V8 crate motors, then you aren't getting a full port job. It takes that many hours of detailed labor to do it right. Again, the power is all in the head. (I'm still not even close to unlocking mine -- race headers this year, ditching the "street carbs" next year.)

Edited March 6, 2011 by zredbaron

[zredbaron]

addition stahl exhaust pics (AKA porn):

 

these are to compare the arrived Stahl race headers to Monza / MSA performance headers and the aforementioned octopus headers.

 

I was immediately impressed that everything here is hand-made. Even more impressive, the merge collector and headers were made at different shops, but slid together like a glove. Remarkable.

 

 

You can really see how impressive the difference in merge points are between "performance" headers and "race" headers.

 

Also, my Stahl headers are NOT the largest primaries, and my merge collector has a smaller merge diameter than road race engines. This is for torque down low at the cost of high RPM power.

 

Bottom line, the octopus headers are really flipping crazy to look at, but so are these. These are tuned, the octopus headers don't seem to have as much detail in that particular regard. Again, WOT vs. torque band.

[jhm]

Hey Mark-

Nice lookin' header....stainless? Bet you're looking forward to getting that on the motor. Good luck getting it all back together, and please give me a shout if you need a second set of hands.

r/John

[260DET]

Those flow figures at 28" are they zredbaron? Any idea why the big difference with the spark plugs out? Not that I follow why a plugs out test would be done in the first place.

[zredbaron]

Those flow figures at 28" are they zredbaron? Any idea why the big difference with the spark plugs out? Not that I follow why a plugs out test would be done in the first place.

 

 

Big preface: I'm not an engine builder, but rather a guy that's learned the hard way and asked questions along the way.

 

Since this is a mostly theoretical thread, I'll share my education as it applies to head flow. This is common knowledge to engine builders, but there are those that could benefit and I don't mind.

 

The theoretical flow knowledge is the combined result of college and military flight school ( helo pilot - more sub-sonic aero theory than fixed-wing guys). Theoretical knowledge and practical knowledge don't necessarily always agree. Engine experts, please chime in if I'm out to lunch or what not.

 

No, I don't know why they would do it without the plug. Two theories: either a.) they weren't supposed to and the supervisor caught it (and I just so happened to receive both numbers) or b.) same reason a dyno shop would turn SAE correction off -- to have bigger numbers and make the customer happier / shop seem better. Numbers without plugs would obviously be useless for calculating ITB / injector size, etc. The only reason I pointed it out, is because well, you never know what a shop does unless you're looking over their shoulder. Sometimes not even then! Haha.

 

Also, in case anyone was wondering, flow numbers are per cylinder, not the whole head. This really gives you an idea of the performance when a 350 cu. in. V8 is often fed by a 450cfm-750cfm Holley carburetor. If I had one of those feeding my head, the head would still be theoretically *very restricted* (at WOT / full lift) and they are found happily feeding an engine ~twice our displacement. Hence why 40mm DCOEs really only belong on 100% stock L6s, even if the carbs are equipped with maxed out venturis. Head jobs of this caliber also take the time to ensure flow numbers between cylinders are comparable. Standard port/polish jobs don't ever go to a flow bench, so no one ever verifies if the cylinders are even, they're just eyeballed. This is why full race jobs cost so much. It's painstakingly detailed, gnat's-ass work. And an art tempered by theoretical know-how and a lot of R&D and experience.

 

As for the disparity of flow between with/without plugs, if you look at the combustion chamber of an L6 engine, you notice the plug is between both the intake and exhaust valves, and is slightly offset. Plugs protrude into the combustion chamber, and as a fuel/air mixture flows around a valve, it wants to do so symmetrically 360 degrees around the stem. If there is a protrusion on one side, then part of that circulular flow pattern is disrupted.

 

Not a perfect analogy, but for visualization purposes:

 

Imagine a sprinkler flow, but a full 360 degree spread. If you were to stick your finger near the tip, you would get a flow disruption.

 

(If it helps you visualize, think about the instant the valve begins to open -- it will "spray" just like a sprinkler will. As the valve opens, it becomes more like your garden hose nozzle on a "full" setting, only with a TON of lift to the point that it probably looks more like a fire hose)

 

In sprinklers, it the spray looks uneven, and would look even more exaggerated than this:

 

In the case of a sprinkler, the flow is still the same, it just sprays unevenly. This is because it's pressurized, and unless you contain the pressure (ie a shutoff valve closing), it will simply flow in a different direction. This is how a nozzle can spray a jet stream long distance. Same flow, small hole; it has to speed up. This is also known as the venturi principle (not to be confused with a venturi, which speeds up [narrows] THEN slows back down [expands]), which is not just for carbs or merge collectors, but even aircraft wings (known as camber, which is how they produce lift). Obviously camber in this case is unrelated to camber in wheel orientation.

 

In a head, you don't have the same kind of pressure that a water pipe does, all you have is atmospheric pressure that PUSHES ambient (outside) air into the vacant space cause by a piston being pulled downward from top dead center. (Suction is NOT a real force.) Air is PUSHED by the pressure of the air behind it, which is why turbos and superchargers are so effective. They PUSH more air because they are at a higher pressure. This is why they have a gauge for boost, so you can see how much pressure (above ambient) is being utilized to SHOVE air into the head/cylinders.

 

This is why Tony D's comment about being at 4000' is significant. At altitude, the pressure is less because the air is thinner. Thinner air, less *resistance* to flow, but most importantly, less oxygen available for combustion. In other words, 400hp at altitude is >400hp at sea level, just like 400hp in the summer is >400hp in the winter. Same car, different air, different performance. This is why dynos have an SAE correction, so that guys in the mountains can attempt to compare numbers to the guys in San Diego. *Attempt to compare.*

 

This is why carburetors must change jets as the weather changes.

 

Unfortunately, it isn't so simple as what altitude you are at / what the [barometric] pressure is. Pressure is literally how heavy the air above the sensor "feels" (imagine a column of air up to infinity). This "weight" or pressure also includes humidity. Humidity is always bad, not just for corrosion, but for oxygen content. H20 displaces O2, and instead of an extra O2 molecule, you might have one or two H20 molecules instead. This not only restricts combustion (less oxygen to ignite with the fuel) but also drastically affects flow characteristics. Aircraft wings HATE humidity, and aircraft engines hate it even more (turbines have thousands of spinning airfoils / tiny wings spinning around 20-50,000 rpm depending on the design). Not to mention water (in liquid form) is incompressible and tries to stick to surfaces and create drag. Bad.

 

"Standard" atmospheric pressure is defined as 25 degrees Celsius at sea level. Again, this is PRESSURE, not air density. Pressure feels the sum of all airborne particles, not just oxygen. This includes water, nitrogen, carbon dioxide, etc. Aviation also uses a term known as "density altitude" that is essentially pressure (ie altitude) corrected for temperature. As temperature goes up, density altitude goes up, but actual density goes down. For example, if you take a balloon and heat it up, it will expand and eventually pop. Inside the balloon pressure goes up and density goes down, but the number of gas molecules inside the balloon is constant.

 

Again, neither pressure altitude nor density altitude tell you anything about humidity content, carbon dioxide, etc. Even *IF* you somehow had the same pressure altitude, same temperature AND same humidity from one town to the next, your carbon dioxide content and other atmospheric gases can't possibly be the same (smog? lots of plants?). You can see why this is so complicated, and now you can see why fuel injection is so important. A computer senses if enough fuel was sent based on *oxygen alone* and simply adjusts it's output for the next stroke (and even does fancy things like adjusting for load, throttle position, temperature, etc). A carb could never compete with that. Ever. Even IF you could tune it perfectly, it would only be for THAT DAY. Hell, that hour.

 

Comparing carbs to fuel injection is like comparing the drivetrain of a GT-R to the drivetrain of a peg-leg manual. No comparison.

 

All this air stuff is why people say dyno numbers are only useful at the same shop on the same day. Plus the machine calibration factors.

 

To the point, in a NA engine, without that extra push found at higher pressures (lower altitudes or boost), every little bit of turbulence matters (inhibits flow), which is why port jobs are so important and therefore ultimately "all power is made in the head." It's more important that the internal turns (horizontal runners turning downward towared the valve, also how it goes "around" the valve) encourage laminar flow (smooth and straight) rather than turbulent flow (disrupted, swirling eddies and what not). *Theoretically,* I do not approve of the JDM port jobs, because they don't encourage laminar flow "around" the valve stem, and because they are polished (again, reference golf balls). The Sunbelt pics I shared show a triangular shape right in front of the valve guide/stem to encourge the fluid to start turning *before* it runs into the stem and therefore minimizes becoming turbulent once encountering the valve guide/stem. Again, I stress theoretically, because the rest of the port is obviously HUGE and therefore may overall flow more despite the turbulence. However, if the flow isn't laminar, then at partial throttle positions, the volumetric efficiency (VE) would drastically be reduced. Again, the JDM heads are for dragsters, which know WOT only. The video of that red S30 sounds nasty and pulls hard, but below ~4.5k, it sounds like an F1 car and just runs like $#!+. Sexy, but not good.

 

Back to the plugs, if a plug is adjacent to the valve stem, the flow is disrupted for approximately one hour of a clock position (1/12). The turbulence around the plug affects the adjacent areas, as well. How much, who knows, but evidently it's about 25cfm. (VERY SIGNIFICANT.)

 

At this level of being "in the weeds" fishing for performance, indexing the plugs becomes an important factor, which is why I commented that I don't know the depth or orientation of the plug. I personally orient my plugs with the open spark facing the exhaust valve. This is for two reasons: it puts the external electrode (ground electrode in NGK v-groove example below) toward the cylinder wall AND less than perpindicular to the intake valve. I want the ground electrode less than perpindicular to the intake valve for two reasons: put the "finger in the sprinkler" in a minimal damage direction but most importantly, to have the center electrode bare and toward the exaust valve. Whew! Now I want the center electrode bare and toward the exhaust valve for maximum flame front propagation, and this propagation is completely uninhibitied toward the exhaust valve, which is where it has to go eventually anyway. Sure, most of the cylinder may not care about that last bit, but the little bit if fuel/air that remains within the vicinity if the spark plug now has nothing in the way between it and the exit. Why not put the ground electrode away from both intake and exhaust valve? It would be *too* close to the cylinder wall, and the flow inhibition and flame front inhibition would likely cause a small dead spot between the electrode and the cylinder wall, especially at higher RPMs when there isn't as much time for the flame front to reach every little nook and cranny for a complete burn. I pick an in-between to balance the pros and cons.

 

This is in the weeds. My Chevy V8 will not benefit from indexing the plugs, but my race motor on race gas will.

 

 

Also in the weeds, the NGK v-groove design causes the spark to attract toward the outside(s) of the ground electrode, encouraging flame front propagation in both directions (and therefore around the ground electrode as opposed to directly through it. Again, my Chevy will not notice, but my race motor with race gas, will.

 

I for one would appreciate an engine builder confirming the indexing orientation theory. Obviously we know indexing is better than not, but optimal orientation and the why, well, I'd like a confirmation if anyone's got it.

 

For the above reasons, the below type of plug (quad ground) is about the worst idea EVER in terms of flow and flame front propagation. Perhaps a reliable spark in difficult conditions such as extreme cold, but I wouldn't ever put it any of my vehicles.

 

 

And finally, 28" Hg (mercury) is NOT a standard atmosphere.

 

1 atmosphere (sea level @ 25 degrees celcius) = 14.7 psi = 29.92" Hg

 

28" Hg = .94 atmospheres = 13.75 psi

 

28" may or may not be the "standard" test, I have no idea, but it isn't a standard atmosphere, that much I do know.

 

15psi of boost equates to an NA engine just driving around as if they were at approximately 30,600' below sea level! (1" Hg per 1000' thumbrule) Now you know why some view turbos/superchargers as "cheating" and many NA engine aficionados regard NA engines as "pure." This extra boost "only" produces an extra 25-50% horsepower, depending on the engine. In some cases, boost can well more than double the power output, but you really have to get into the weeds on the turbo side of the house to do that.

 

I better stop typing before I get too delirious. Very overdrawn on sleep!

Edited March 8, 2011 by zredbaron

[Tony D]

28" Hg for all intents and purposes is an atmosphere for the purposes of head flow porting.

 

This gets into the argument of 'does the engine create a vacuum, or does atmospheric pressure fill the cylinder'?

 

I'm in the 'atmospheric pressure fills the cylinder' camp, and therefore realize there are some inefficiencies in the intake manifold that will likely add up to 1"Hg somewhere along the line---and that makes 28" a good number to approximate N/A flow.

 

What would be interesting is to see what the ports flow under pressure (real pressure, not pressure differential)...

 

Basically the flow bench makes a region of low pressure by moving air out of the intake tract, other air is pushed in by atmospheric pressure to fill that void, and you measure it's rate of filling... It's become a Standard for 'best case flow simulation' since most carburetted engines operate around 9" Hg restriction at WOT and peak rpm/load. It's nature of the beast for carburettors, they require differential to operate.

 

Now that same engine on EFI can operate at WOT and 2"Hg (or less) which means less pumping losses and more potential flow through the orifice. If you can mate the fuel to it, and get it all burned you will make more power.

 

I'm glossing over this because we went through a couple of bottles of Scotch at the KTV this evening and this is a postscript to the events before I hit the hay...

Hope this is helpful in some manner...

[zredbaron]

This gets into the argument of 'does the engine create a vacuum, or does atmospheric pressure fill the cylinder'?

 

Strictly speaking, both are true, so long as by vacuum one means 'relative' vacuum. The piston creates a relative vacuum (ie pressure differential) which allows/causes atmospheric pressure to fill the cylinder. The only time this statement would be incorrect is if someone says the piston "sucks" or "pulls" in fuel/air. Vacuums do not suck up dirt; ambient air shoves itself into the vacuum because an air pump is creating a vacuum, and it the incoming air collides with dirt (loosened by a revolving brush) and the dirt goes with it, just like a plastic bag gets shoved around by the wind.

 

My 2 cents when this topic comes up over scotch: don't ever let a pretentious person get away with saying "sucks" or "pulls." Short of artificial gravity or an atomic lasso cast via nanobots, you cannot *pull* on an air particle.

 

Sarcasm aside, thanks for the practical knowledge, Tony. Hadn't thought of the flow restrictions ("head loss" is the term, and it's not referring to a head, but rather resistance to flow) encountered in the intake (before the port) and it makes sense to factor that into what pressure differential you choose to approximate atmospheric. Glad to hear my test was "standard" even if my mind has an asterisk wanting to know more about the temperature, humidity, etc.

 

I had no idea that EFI operates on such a drastically less amount of pressure differential at WOT. Makes sense of course (no exaggerated venturi, but rather air horns or tapers), but I didn't think the difference would be so significant. This leads me to wonder why peak hp numbers via EFI vs carbs for the same motor aren't all that different. Makes sense for partial throttle positions (larger pressure differential), but WOT... hmm...

 

[Highland? Islay? Haha.]

Edited March 7, 2011 by zredbaron