NA 3.1L=>head & camshaft questions. No shortcuts, max

[JMortensen]

So I looked again and it's hard to tell from your video. Are you spinning the inside tire, or both, or can you tell? If you're spinning the inside tire, then the Quaife is a problem. If you're spinning both, then you just need more tire back there, or some other method of getting more traction out of the tires you have.

[zredbaron]

shifting this discussion to its own thread:

http://forums.hybridz.org/showthread.php?p=956374#post956374

[zredbaron]

went to the dyno today.

 

You're better off going with an N42 or a P90 head and using custom pistons to get the comrpession you need (at least 12 to 1). I don't know anyone using an E31 head and getting more then about 275hp.

 

I would argue that the 3.0L Jim built me is the "best", but I'm hardly an unbiased source. Dan Baldwin, Mike Eckhuas, and a few others have some pretty powerful NA L6 engines. You'll need to be pushing over 300hp at the crank and over 260 at the wheels to compete...

 

well john, i'm still running the e31 that jim thompson built for me, and i put down 264hp to the wheels today (dynojet). if your 275 hp statement from yesteryear was talking about from the crank, then i'm pretty damn pleased.

 

hell, i'm damn pleased regardless!

 

this was a 67hp and 64 ft-lb gain from the engine rebuild (forged pistons, race cam, 12:1 compression). this works out to about 34% gain in both hp and ft-lbs for about $5000. you warned me. NA costs $$$.

 

there's still a fair amount of power out there still. my exhaust is still street performance level (msa headers with an open muffler and non-mandrel bent 2.5" pipe). stahl headers and 3" mandrel one day.

 

but more so than that, today i think i finally lost my stubborn attachment to the webers. i have an overwhelmingly complete set of jets, but i can't even come close to getting the a/f ratio reasonably flat. not even close! graphs below.

 

that and according to the weber book my 40dcoes (specifically the 36mm chokes) can't feed what my engine is trying to burn. add that to the tuneablility and driveability equations, and i fell out of love with webers. i still love the nostalgia factor, but... well, that's about it. hah.

 

here are the graphs:

 

A/F RATIO:

 

as you can see its all over the place. the weber sticky has many of us noting this insanely rich dead spot, but not one person has piped in with a cause or solution. so that's cool. i assure you i experimented with mains, idles, air correctors and even got into the weeds with emulsion tubes. this was the best i could do...

 

oh, i even added a MAP (manifold absolute pressure) sensor to add some advance based on load (lack thereof, actually), but no. still falls flat on its face unless you know how to work the pedal.

 

[EDIT -- large chokes. large chokes produce bettter peak hp but poor driveablity. this MUST be what we're seeing here...]

 

 

 

TORQUE:

 

and of course this has its effect on the torque. the pedal has to be feathered until above this dead spot (which is now shifted 1k higher thanks to race gas for some reason). this feathering is shown as the relative dip in torque climb as the rpms climb from 3k to 4k. WOT caused the engine to fall flat on its face and sputter and surge in an embarrassing manner.

 

 

 

 

POWER:

 

here's the final power curve, with a feathered throttle input again producing a dip in the climb from 3-4k. (WOT starting at low rpm confused the computer... it thought the user was shifting because of the surge in power/torque).

 

 

 

 

but again, in the end i'm pleased. it sounds and feels very full.

 

here's a video of one of the better dyno runs:

 

 

lastly, thanks again to all of the experience shared on this thread. it's truly been an eye-opener for me, and based on the number of random "great thread!" comments, your knowledge has been shared with quite a few enthusiasts!

[josh817]

Wow, you did well!

[JMortensen]

Verrrrrrrrrrrrrrrrrrrrrrrrrrrry nice.

[Guest Widebodys30]

NICE car.

AWESOME(and fun I bet!) vids!

 

One thing I noticed in your statements on AvGas, and it's composition.

 

1) Aviation engines are almost ALWAYS LOW compression(under 8-1). These engines are built with HUGE safety margins. Imagine basically a big block VW or corvair motor, trundling along @ 2,500-3,000 rpm's or so, as cruise is usually @ 70% throttle. To give you an idea of size, my ashtray made from a Lycoming piston, halved at the wrist pin is @ 5 inch bore. Usually the only high C/R aviation motors you ever see are race/competition aircraft motors.

2) LEAD. Lower lead content than 20 years ago, but enough of it that a small leak will leave a grey spot! Remember, average AC age is dang near 35-40 years old or so now, if memory serves. And it is NOT uncommon to see 40's and 50's vintage AC with the original power plants. The correct name for AvGas is actually 100LL AvGas. LL meaning...right. Low Lead. The production for aviation applications is so small, that ONE refinery can produce the entire world's supply for an ENTIRE year in ONE day. That's how they can still produce gas with lead content.

3) LEAN conditions. These engines are MADE for it, aside from having a lever to manually adjust the A/F ratio! Ever been in an open cockpit AC? Aside from HUGE fun(you think Z's are cool? lol Try a 6G+ freestyle roller coaster!!) Air is MIGHTY cold and gets thin fast above 2,800-3,000 ft. Feels like stepping out of your house during winter naked, or something. You can feel the boundary layer. And, that's @ a LOW altitude, let alone 10,000 ft.

 

But yes. Formulated for a completely different purpose than Race fuel.

 

[blackwidow]

Wow, nice work beginning to end. I probably will be starting an n/a engine build myself here pretty soon but only looking for a nice streetable 220whp.

 

1. I am amazed at the drop off on that cam pic.

 

2. You asked about coatings, if you havent already found it by now look up WPC treatments for your next go around. The benifits to dollar ratio is very nice, and can be used on anything from engine bearings to ring and pinions in diffs.

 

3. Itb's = better power curve and all the good things on a track that come with it. http://extrudabody.com/ Kevin is a pretty good guy and don't forget you can reclaim some of the cost by selling the triples.

 

4. Me = jealous of your car at the moment. Very nice.

[wondersparrow]

This is a great thread. I've referred to it a few times during my build. Last time I had my track car out, I kind of boiled the gas in my carbs and had a small fire Not fun. So, being on a budget, I cleaned up my headers, painted them, wrapped em, and painted them again with some thermotec stuff designed for wrap. I am also in the middle of trying to make a nice big stainless heatshield (which will have a thermo blanket riveted on). The problem is, I can'f figure out the best way to attach it. The picture below shows mark somehow bolting it to the header, but I cant tell how....

 

Any thoughts?

 

[zredbaron]

the heat shield in this pic was an aluminum plate, crudely cut and bent into shape. the header side has layers of chalk asbestos boards (yes, asbestos!). evidently asbestos has a wondrous resistance to heat transfer and won't catch on fire) screwed into the aluminum plate.

 

fastening the plate to the header wasn't exactly graceful, either.

 

i'm not sure what you call it, but i can describe it: a long, threaded bar (pole/stick?) of metal that i bent and wrapped around the header. threw a couple nuts on it and tightened them, cinching on the header. you can find the threaded bar in home depot for about $5 right next to where you would find angle iron and skinny metal and wooden poles/sticks. some of the skinny round metal poles are threaded and fit a standard nuts like 3/8" or whatever it was.

 

the green strap-like looking piece in the middle was a hangar wire wrapped around the headers to prevent the plate from flapping.

[JMortensen]

All-thread is the name of the stick of threaded metal.

[wondersparrow]

Ah, so you just made some hooks and then tightened them on? I was thinking it was some sort of pipe hangar or something. I spent at least an hour last night staring at my heat shield trying to figure out the best way to fasten it on.

[wondersparrow]

Well, got it all back together today. I used a couple of small (1-5/8") exhaust clamps to secure the shield. Its fairly thick stainless, so I don't think that flapping will be an issue this way. Also adjusted the timing so that its running ~34 deg advance total. Looks like it will do the trick, though i am sure it is a much bigger pain to install than the J-bolts.

 

Thanks for your help guys

 

 

Ugh, that engine bay needs a little work.

 

 

Just a quick shot of one of the u-bolts coming through the shield.

[Daeron]

wondersparrow, I think it looks freakin amazing, even if it could use some elbow grease. I saw it and started grinning immediately.

[Bart Hoedemaker]

Put an air filter box on it, all that dirt, works like a sandblaster inside your engine.

[zxtman]

 

 

 

Use some good sized flat washers so you don't tear the reflective heat barrier while tightening down on the nuts.

[wondersparrow]

There are some washers under there, they could be bigger. I'll take care of that next time its off. Good call.

 

As for the filters, I have socks for the horns. The way the strut tower support is welded in there, not much else fits. Unfortunately, those aren't weber air horns, so even the foam socks don't fit quite right.

 

I ran it last night for a bit to cure the paint and the wrap. Though it never really got much over 180º (last time it was out, it got up to ~230º at idle, ~180º on the track) I feel the head gasket is suspect. I topped off the rad before starting it and after about 20 minutes it started to vent a little out the breather by the cap. I may have just overfilled it. I'll have to do a compression/leakdown asap to double check. The wrap and shield must have done the trick though, the carbs were cool to the touch the whole time.

 

Update:

I ran the compression test, and I kindof found what I expected. 1-6 : 160, 145, 140, 160, 140, 115. I added some oil to cylinder 6 and retested it. Got 130. I figured the engine was going to be a little tired as I am not the first person to put it on the track. The cooling system overpressure seems to have gone away, but its hard to test without really loading the engine. I am going to check on valve lash and see if there are improvements to be made there.

 

Question, how much does the oil system breathe normally? As my engine warms up, I can see a small stream of smoke coming from my catch tank breather (no egr). Its not a lot, and I think it may be farily normal.

Edited August 6, 2009 by wondersparrow
added comp test results

[Dan Baldwin]

 

here are the graphs:

 

A/F RATIO:

 

as you can see its all over the place. the weber sticky has many of us noting this insanely rich dead spot, but not one person has piped in with a cause or solution. so that's cool. i assure you i experimented with mains, idles, air correctors and even got into the weeds with emulsion tubes. this was the best i could do...

 

Every biggish-cammed highish-hp carbed L6 build I've seen does that, it's due to reduced V.E. and multiple carburetion in that rpm range. I.e., air comes through venturi once, gets fuel, then some air gets pushed back through the venturi due to late intake valve closing and picks up more fuel, then gets drawn through again, picking up still more fuel, at the next cycle. With fuel injection you could improve the A/F ratio, but you'd still have a big torque dip there, as it simply doesn't breath well at that rpm. What works great at 6500+rpm doesn't necessarily work all that great at 3800rpm...

Edited December 11, 2010 by Dan Baldwin

[zredbaron]

Every biggish-cammed highish-hp carbed L6 build I've seen does that, it's due to reduced V.E. and multiple carburetion in that rpm range... With fuel injection you could improve the A/F ratio, but you'd still have a big torque dip there, as it simply doesn't breath well at that rpm.

 

Thanks Dan. Makes sense to me! Going to stick with that theory until I make the jump to ITBs.

 

Speaking of engine upgrades, I've got the engine out of the car again. Had a coolant leak (700 miles after rebuild in 2008), so I returned the whole block to the machine shop for investigation. I haven't seen it in person yet, but they found the coolant was leaking between cyls #1 and #2 and had to weld the head. Currently waiting for the head to return from another shop that has a flow bench set up for inline 6 cyl heads. (I wanted the numbers for future ITB diameter selection.)

 

To the point, although I'm leaving the intake alone for this rebuild, I'm upgrading to the Stahl headers while its all apart. As previously discussed on this thread, two 2.5" collectors will merge into a 3" outlet, but Stahl offers a variety of runner diameters: 1 3/8", 1 1/2", 1 5/8", and 1 3/4".

 

Any suggestions? Yes, the engine aspires maximum NA hp attainable, but let's face it, the car is a dedicated autocrosser at this point and drivability / low end torque are factors. I also want to keep in mind that fuel injection *is coming* and intake flow capability will match that of the head. I'd hate the exhaust to be a choke point down the road. Also, how do racers feel about header coatings? I'd love to hear everyone's thoughts!

[zredbaron]

Reporting back on my findings: 1 5/8" header primaries are the consensus.

 

1 3/4" primaries are for road race motors -- for autox, drop the diameter 1/8" to gain some low[er] rpm torque at a slight cost of high rpm power. Encountered stern warnings that 1 1/2" primaries would severely restrict a ~300 hp (flywheel) motor's power output (my outgoing headers are rusty Monzas from 1999 - 1.5"?). JohnC was also able to set me up with a header merge collector, which evidently should also help mid-range torque a bit as well.

 

In a related note, after reviewing Dan's recent comments on the A/F mix ratio, I wonder if I might be able to improve my A/F curve with a proper exhaust. I'm not expecting a cure of course, but I can't help but suspect a measurable improvement to the A/F dyno plot might result. Better flow out means less dirty gases remaining behind and therefore increased combustion as well, or so I'm thinking anyways. Hoping to slightly flatten the rich and lean peaks that will likely still occur.

 

I'll be sure to post the dyno plots when the time comes. It will be interesting to note the exhaust improvement's effect on all three curves. Another year or two later of course, fuel injection. (Hey, this thread started 7 years ago, after all!)

 

[ EDIT -- There will be one other improvement on the dyno plot (unfortunately for the AFR theory, but fortunately for performance). Remember the radical cam that was put in the motor in 2008? I've finally tracked down the springs the cam was profiled for (the outer springs only design, limited to 7700 rpm). Had to order the springs from Jim Wolf Racing, in case anyone ever has to track down outer springs for a Sunbelt/Jim Thompson cam, haha. Anyways, the proper pairing of springs to cams is of course crucial (probably even more so for aggressive cams), making the total of 2 dyno variables: exhaust AND springs. ]

 

Also, my flywheel and clutch are toast. Going with the ArizonaZ 6-puck sprung disc setup. Seems to be a fair price for the quality, should be a good weight for autocross, too.

Edited January 28, 2011 by zredbaron

[zredbaron]

I was thinking about starting a separate build thread for this year's engine upgrades, but I thought twice about it since this thread might be more appropriate.

 

Now that this thread has been removed from the L6 stickies list and now a "FAQs-->Powertrain-->L6" thread relocated by the Admins, I thought I would pose the question to the Admins / readers since HybridZ is a forum after all:

 

Should I continue to post my race engine upgrades and related dyno findings on this "FAQ" thread or start a separate build thread?

 

My thoughts are that in this case it's nice to see in one thread how all aspects of the engine are tied in through the head, and how chasing around the new choke point relates to output of the motor on the dyno.

 

Thoughts? If I get no replies I'll probably post the pics and data here...

Edited May 8, 2011 by zredbaron