200+ WHP NA build

[Gollum]

...I see people quoting manufacturer's engine specs (some of which are known to be generous)...

 

For claims of 80+ ft/lbs of torque per liter, I feel it should be pointed out that F1 engines are only slightly more efficient than that.

 

Manufacture specs are regulated and the few times that there have been cars that don't live up to ratings there's costly recalls for the manufacture. Some examples are the early RX8's, and the early DOHC Cobras. In both cases the manufacture took back cars and rebuilt engines, and then later fixed issues or changes the rating in subsequent years. By contrast though, there's no laws or regulations mandating that manufactures can't underrate their performance. The new 2011 Mustang GT's with the Coyote V8 are an example, where even the very low dynos are showing figures that show that Ford probably underrated the engine a good 3-5% at least. Some of the dynos that are known to be "pretty number" dynos can show nearly at the wheels what should be at the crank, which definitely starts to indicate that something is up. Same thing happened with the 03-04 cobras, but it wasn't as impressive I think because it was a supercharged engine and Ford was just being cautious with their previous flops.

 

Point being - it's more common for there to be underrated engines than overrated engines from every shred of evidence I've experienced and seen.

 

And on the second point you brought up. F1 engines by what HP they're supposedly running, at the RPM limit they have, they're making AT LEAST 100lbs per liter at peak HP and that's with a bunch of regulations that restrict power. If you believe what has been said that they're capable of over 1,000hp if there weren't restrictions then assuming the RPM stays close (which might not be true) then that would put torque at over 116lbs per liter!

 

All that said, I do believe that things vary dyno to dyno and comparing figures against each other can be taken way too seriously and is best left to just the realm of speculation. But that said some of the people that have posted have actually had their engines on ENGINE DYNOS which are incredibly accurate.

 

I'm sure tony could chime in here, but just looking at what RPM some L engines we know operate at, and calculating what HP the engine is actually putting down via performance numbers, it's amazing what torque has to be created in order to get those numbers. It's certainly not F1 numbers, but it's certainly more than most NA production engines.

[Gollum]

I also just found this great article on the subject of torque per liter. Even there they state that 90lbs per liter isn't impossible

 

http://www.pumaracing.co.uk/POWER2.htm

 

What I think can also get us really screwed up on this topic, is that for a race car having less torque overall can be desired if it's giving you substantially more torque at higher RPM. It's not hard to get really high torque per liter at lower RPM if you create a system that's well matched for that RPM.

 

The reality though, is that many people get crazy and put parts on their engine that don't match the flow of the system. It's like how you can put too large exhaust on your car and loose considerable torque. This isn't because you have to give up torque for increase high RPM flow. It's amazing how many times I've seen guys with crush bent 3" exhaust on a sub 2.5 liter engine. In most cases if they switched to a smaller diameter MANDREL bent exhaust they'd pick up Torque AND HP.

 

A low volume/diameter port can make just as much torque as a large volume/diameter port, it will just have to be in a different RPM range.

 

We can build a stump puller Ford 351W that makes 75lbs per liter at 2500 RPM. In order to get the same engine to make that torque at 5500 it'd take totally different heads, intake, exhaust, cam, etc.

[zredbaron]

Tony, in my opinion your PM belongs in this thread. I don't think anyone minds the back-and-forth banter, as we're all still reading! Your comments helped me confirm and understand why I've reached my conclusions. I didn't learn anything new per se, but it's great to have my somewhat fuzzy conclusions confirmed with similar examples and hear a different phrasing of "why." I think your explanation would be very beneficial for silent readers that are on the fence regarding their budget size for head work and cam selection. ~2500 thread views, after all.

 

I honestly don't know what's more impressive:

• That the [NA] L6, such a rudimentary OHC engine by modern engine standards, is capable of producing such impressive hp/L or ft-lbs/L.
• That engine builders can modify such a basic 2-valve/cyl engine to acheive such an end. Both are truly remarkable!

I go back and forth as to which is the bigger wow factor. Doesn't really matter, but it's part of my addiction to the L6.

 

For the record, this is not a reply to toot my own horn, but rather to emphasize the impact of high-end head work and it's alignment of a *properly* designed cam (vice a catalog cam). And the potential to hear some comments on the matter from people who know far more than I.

 

I'm sure tony could chime in here, but just looking at what RPM some L engines we know operate at, and calculating what HP the engine is actually putting down via performance numbers, it's amazing what torque has to be created in order to get those numbers. It's certainly not F1 numbers, but it's certainly more than most NA production engines.

 

I feel very strongly that I haven't realized my engine's potential (not even close). I'm of course also wary of that being my personal fantasy since my "numbers" are already stout, having been burned with this same fantasy of bigger numbers in my previous engine builds. Preface aside, I'm quite encouraged by my current output since from what I know, it's still severely restricted.

 

Tale of the Tape:

• 2008 dyno: 265whp @ 6000, 250 ft-lbs @ 5000. (DynoJet.)
• 232/153cfm in/ex (w/o plug?) and 209/134 cfm in/ex with plug installed (anyone know why the 'w/o plug' would be useful? i.e. why do I have this data to begin with?)
• Intake: 40mm DCOEs with 36mm venturis. The Weber book indicates about 44mm venturis (not to be confused with Mikuni 44 bodies of course) would be appropriate for the engine "to breathe sufficiently" to my springs' soft limit of 7600. This of course doesn't necessarily mean it's what I would choose, I need low-rpm driveability, too. (Enter fuel injection!)
• Exhaust: Monza headers from 1999 (from Victoria British / Black Dragon), 2.5" kinked pipe going back to an open muffler
• Electromotive ignition
• 12.5:1, VP 109 race fuel

Per Liter:

• At the wheels: 85.4 hp/L and 80.7 ft-lbs/L
• Theoretical crank (using 15% drivetrain loss): 100.5 hp/L and 94.9 ft-lbs/L

The point of this, is that my intake and exhaust were "streetable" and the rest of the motor is a no-holds-barred autox race motor (12.5:1 is the only compromise; chosen for longevity). The only things I didn't do is polish the rockers and coat the friction parts (not sold on the latter). Even with significant restrictions, the VE of the head seems to take control and presumably maxes out the potential of the intake/exhaust, whichever is the weaker link. Both reduce the potential, but no doubt one is maxed out and the other is not. Looking at my A/F graph and the weber chart, I'd say it's the carbs hands-down.

 

Bottom line: if you don't build everything to work together from the start, you end up chasing around choke points and rebuilding unnecessarily. That's obviously what I've done and am still doing. Don't be like me!

 

[End contribution, begin requests for knowledge.]

 

The thing that I'm wondering now that I have proper race headers / merge collector, is how my torque curve will shift. I'm predicting the bell shape will shift downward in the RPM range (I don't have the largest primaries available since I plan to use the entire RPM range), but that the curve will also shift up and grow wider / more flat. [EDIT - The "shift left" prediction is based on me leaving the restrictive intake on the car; I predict it will go both directions once I go ITBs, but perhaps that's fantasy? Low rpm due to scavenging, high rpm due to feeding more air? Peak hp will no doubt shift above 6000 at that point?] It feels *so* much more full at lower rpms / mid throttle, but the pull's transition is deceivingly smooth and my butt dyno recognizes its limitations / the illusions of sound.

 

To me, the race exhaust has "unlocked" the remaining potential of the head, but it of course won't be realized until I go to ITBs with proper diameters (or proper carbs, which I won't be doing). I'm also curious if the exhaust scavenging will help the A/F ratio or exacerbate it. I predict both, at different RPM ranges. [EDIT - Nevermind, that was retarded. I think it can only help.] Very curious, indeed! Dyno is probably 9 months out since I'm bouncing around for the next six months.

 

I'm mostly encouraged at having a flat A/F line with inputs for throttle position, vacuum, etc. The power under the curve is obviously what I'm going for with autocross. That said, more power is always appealing! (Intoxicating, in the words of JohnC.)

Edited September 22, 2011 by zredbaron

[Leon]

It's like how you can put too large exhaust on your car and loose considerable torque. This isn't because you have to give up torque for increase high RPM flow. It's amazing how many times I've seen guys with crush bent 3" exhaust on a sub 2.5 liter engine. In most cases if they switched to a smaller diameter MANDREL bent exhaust they'd pick up Torque AND HP.

 

Not true. Not sure if you're familiar with the sticky in the exhaust sub-forum: exhaust tube sizing

 

My apologies for the digression, but the myths must be corrected...

[Gollum]

Don't apologize. It was a worthwhile read and I seem to remember read some of that before... My bad. To be fair, now that I think about it, most of the improvements I've seen in going to smaller diameter pipe were probably as much due to bend quality and radius as much as diameter. Meaning a 3" pipe with crappy tight radius crush bent curves can have severe restriction/friction while a smaller system with smoother bends can actually have LESS restriction.

 

I think though that you would agree though, leon, that my statement holds true when talking about headers. There is such a thing as going too large or two small on your primaries.

 

My point though more than anything else is that there is such a think as mismatching your induction and exhaust systems in BOTH size directions, not just one or the other. If you want to maximize torque in a particular range, you'll need to make sure everything from your throttle body (and before actually) down to the muffler are optimized for that flow and velocity. Something that comes to mind is that you don't just tune intake runner length, but also diameter. It's why design parameters are so important.

 

Something that's kind of bothered me about some of the assumptions that have made in the attitude of "this is what production cars do so that's what I'll expect" seem rather ignorant to time tested experience that I've had myself and seen time and time again by others. You can take a completely stock longblock and gain TONS of power (including torque) by removing OEM restrictions in the system. An OEM doesn't design everything with raw performance in mind. A good example is the NA VG30E dyno that's on Jason's site:

 

 

 

STOCK longblock (chassis dyno) plus upgraded intake pre-throttle body, and exhaust (engine back), and fuel system.

 

The stock VG30E should have 160 BHP, so that first graph of 130 might suggest that either the dyno is reading low, or that there was power lost from the upgrades maybe? Either way, something is certainly a tiny bit low on that dyno but it's within the ballpark of what would be expected.

 

But then you see what happens with cam timing adjustments. WOW. Not only is he now putting down more HP to the wheels than the engine was rated at BHP, but he picked up enough torque that if assuming even an absurdly low 12% drivetrain loss that's a good 68lbs per liter, if we assume a more realistic 15% that equates to 71lbs per liter. And that's a completely stock VG30E which is a 2V head!

[Leon]

Don't apologize. It was a worthwhile read and I seem to remember read some of that before... My bad. To be fair, now that I think about it, most of the improvements I've seen in going to smaller diameter pipe were probably as much due to bend quality and radius as much as diameter. Meaning a 3" pipe with crappy tight radius crush bent curves can have severe restriction/friction while a smaller system with smoother bends can actually have LESS restriction.

 

I think though that you would agree though, leon, that my statement holds true when talking about headers. There is such a thing as going too large or two small on your primaries.

 

I can't agree to that statement because it is incomplete. Headers and collectors do a different job than the exhaust pipe out back, and the dynamics of their interactions with the cylinders are often misunderstood.

 

Keeping pipe length constant, smaller diameter primaries will be more effective at a lower rpm and larger primaries at higher rpm. In the way that people like to talk about header primaries, I would say there is no such thing as going too big. People like to say X inch primaries are way too big for a certain engine, but how would they know if pipe length doesn't even enter the discussion? It's a well thought-out combination of pipe length and diameter which makes a tuned exhaust header/collector, and the tuned rpm range is dependent on both.

 

A properly designed exhaust system will take into consideration multiple parameters, including a diameter which keeps pumping losses at a minimum, is physically able to be routed appropriately within the engine bay while minimizing bends, and a length which tunes to a certain speed range given the chosen diameter.

 

 

My point though more than anything else is that there is such a think as mismatching your induction and exhaust systems in BOTH size directions, not just one or the other. If you want to maximize torque in a particular range, you'll need to make sure everything from your throttle body (and before actually) down to the muffler are optimized for that flow and velocity. Something that comes to mind is that you don't just tune intake runner length, but also diameter. It's why design parameters are so important.

 

If you want a peaky engine, then the above applies. Good engine designers will flatten out an engine's powerband by matching the induction and exhaust systems to different rpm ranges.

 

As mention, intake length and diameter come into play in resonance tuning, exactly like exhaust tuning.

 

 

This reminds me, I'm working on a spreadsheet that predicts tuned rpm (intake and exhaust) depending on your engine setup. I will verify it through dyno testing first before trusting it one bit, but if it's close then it can be used to predict tuned lengths of any engine setup. We'll see...

[zbloke]

Good engine designers will flatten out an engine's powerband by matching the induction and exhaust systems to different rpm ranges.

 

Does this mean you could tune your intake to give you bottom end power and your exhaust to give top end power?

[Leon]

Does this mean you could tune your intake to give you bottom end power and your exhaust to give top end power?

 

Yes.

 

However, the results of combining intake and exhaust tuning are not linear. If under certain configurations an intake design gives an additional 5hp and the exhaust another 5hp, does not mean that combining the two will give you 10hp. The systems interact with one-another and the results of certain combinations can be surprising good (or bad). It takes design work and experimentation to get it right.

Edited September 22, 2011 by Leon

[Gollum]

Thank you very much for not only clearing that up for me, but explaining it in such a way that most of us should be able to grasp.

 

On the topic of intake tuning, I remember seeing a "intake dyno" of sorts in a book a read a little bit ago, "how to tune and modify engine management systems". It was merely to show the effect of tuning to different harmonics on an engine. I wish more info had been given, but it was intriguing in the sense that while tuning for lower harmonics offered higher benefits at given RPM, the best broad range power was gained by tuning to the 3rd harmonic if I recall correctly. Without diameter and taper data it's a bit of a broad stroke, but still interesting to think about.

[zredbaron]

Tony D's PM, posted with his encouragement:

 

 

For me, the lightbulb turned on when I had the head off for this year's round of upgrades (undynoed). I had the head flow-tested and was very surprised to learn that my peak flow numbers *exactly* coincided with the lift numbers on my 2nd Sunbelt cam! It was almost as if the cam was profiled for the flow characteristics of Sunbelt's head work, weird!

 

This is EXACTLY what I told Scott B to discuss with Ron at Isky when he was having Slover's port his head. He was making 218cfm flow on the intake at some specific lift, and curiously that is what Ron capped his lift at.... And given the engineering requirements of TDC and BDC, piston acceleration, etc... It's all been well tested and documented. I simply can't fathom why guys buy a camshaft off the shelf when if they have head flow numbers, bore and stroke information, they can simply call Isky and get a cam that will make KILLER HP without anything else being done to the bottom end. The guy doesn't get it. Scott was really impressed at the power he got, far beyond what he expected. And his budget fell short as the head and cam was setup for 44 Mikunis. I said it would make 20HP more for the 200HP REAR WHEEL number, it was at the SAME power peak that Scott has---of course it will make MORE and a higher rpm...but Scott was making 182 at something like 6250 or some odd number. If the Mikunis added 3-500 rpms to the powerband, I would expect 200 at 6250, and something like 225-235 at 65-6700. All WELL below 7500 rpms. Without forged slugs, and with torque so strong at 3000 he has to watch it because the back end gets squirrely and stays that way till almost 5000 when torque/horsepower cross and taper off (hp rises)...

 

Indeed, it's all about matching. Truthfully he could have spent a LOT more for a Schneider Cam, forged pistons, and like you said "a list of parts from MSA" and ended up with less drivability, less power, and likely would have STILL been happy---but also perpetuated the myths surrounding 'loss of bottom end' etc etc etc...

 

This is the difference between people who have DONE and people who read a lot and then make a plan without LISTENING to real world experience. No matter WHAT an engineer's calculations say, when it goes onto the test floor and does something different---YOU CHANGE THE SETUP! (At least a good engineer does. Of course, the Germans will blame the guy running the test, and the guy who did the setup...but that is another story altogether!)

[Daemione]

Tale of the Tape:

• 2008 dyno: 265whp @ 6000, 250 ft-lbs @ 5000. (DynoJet.)
• 232/153cfm in/ex (w/o plug?) and 209/134 cfm in/ex with plug installed (anyone know why the 'w/o plug' would be useful? i.e. why do I have this data to begin with?)
• Intake: 40mm DCOEs with 36mm venturis. The Weber book indicates about 44mm venturis (not to be confused with Mikuni 44 bodies of course) would be appropriate for the engine "to breathe sufficiently" to my springs' soft limit of 7600. This of course doesn't necessarily mean it's what I would choose, I need low-rpm driveability, too. (Enter fuel injection!)
• Exhaust: Monza headers from 1999 (from Victoria British / Black Dragon), 2.5" kinked pipe going back to an open muffler
• Electromotive ignition
• 12.5:1, VP 109 race fuel

Per Liter:

• At the wheels: 85.4 hp/L and 80.7 ft-lbs/L
• Theoretical crank (using 15% drivetrain loss): 100.5 hp/L and 94.9 ft-lbs/L

It must be a blast to drive . . . and a very nice tq/l figure. But I'm guessing that a 12.5:1 compression race fuel engine is outside the boundaries of what the OP is looking at in his calculations. So I'm not sure it proves an exception to the streetable ~65 tq/l idea. But maybe 70 is a more realistic goal for a daily driver? :shrug: So hard to compare when all dynos are different.

 

I'm the first to admit, I don't have any hands on experience building up an L6 - but I'm frankly very surprised at the claims of amazing torque efficiency people are managing to get. Figures that exceed the most advanced engines in the world right now, from a 40 year old engine design. I think some skepticism is both understandable and healthy.

[Daemione]

Point being - it's more common for there to be underrated engines than overrated engines from every shred of evidence I've experienced and seen.

I agree, definitely more common to have an underrated engine. But even from a company that rigorously adheres to what their engines actually produce, they're still quoting flywheel horsepower, under more or less ideal circumstances. So not comparable to the #'s in question - torque at the wheels.

 

And on the second point you brought up. F1 engines by what HP they're supposedly running, at the RPM limit they have, they're making AT LEAST 100lbs per liter at peak HP and that's with a bunch of regulations that restrict power. If you believe what has been said that they're capable of over 1,000hp if there weren't restrictions then assuming the RPM stays close (which might not be true) then that would put torque at over 116lbs per liter!

I'm only a casual F1 enthusiast . . . but my understanding is that the "restrictions" placed on their engine design only serve to make it a better comparison for a street engine. e.g. they're limited to a certain engine layout, number of valves, maximum bore size, maximum rpm, etc. Exact numbers for how much those engines produce are understandably difficult (impossible) to find, but every source I find right away lists 20X ft/lbs. of torque as about what they're capable of . . . translating to no more than 87 tq/l. Flywheel? I'm not sure. Maybe the rev-happy oversquare configuration they favor sacrifices a ton of torque, but in looking at torque numbers from hugely oversquare bike engines, I'd be surprised if that were the case.

[johnc]

My engine was about 91 ft.lbs./L which is nothing for a race engine. Hell, my 2000 F350 with the 6.8L V10 gets 73 ft.lbs./L. I have a more fundamental question about where this thread went. Who cares about ft. lbs. per liter? What ever happened to the more common measure of horsepower per liter? Why are off on this obtuse measure of performance? Are we building diesel engines?

[Daemione]

My engine was about 91 ft.lbs./L which is nothing for a race engine. Hell, my 2000 F350 with the 6.8L V10 gets 73 ft.lbs./L. I have a more fundamental question about where this thread went. Who cares about ft. lbs. per liter? What ever happened to the more common measure of horsepower per liter? Why are off on this obtuse measure of performance? Are we building diesel engines?

Again - how long is your ruler? Manufacturer's spec? Engine dyno? At the crank? Flywheel? Just trying to compare apples to apples.

 

And obtuse? If anything, hp is the obtuse/abstract measurement. For a street car, if we're not going past 7k rpms, stock gearing options are really the only option. And unless we're planning on (much) higher redlines and major changes in gearing, a big hp number is useless. After all, if we move a torque peak up from 3k to 5k rpms, we'll probably have a lot more hp . . . but will it be faster? Nope. The general argument has evolved (devolved?) into whether we can really expect to see massive gains in torque efficiency. The way I see it, HP is just a number - one that's value is dependent on several variables. If we're not going to be changing those variables to take advantage, then what's the point of paying attention to the figure? :shrug:

[Leon]

My engine was about 91 ft.lbs./L which is nothing for a race engine. Hell, my 2000 F350 with the 6.8L V10 gets 73 ft.lbs./L. I have a more fundamental question about where this thread went. Who cares about ft. lbs. per liter? What ever happened to the more common measure of horsepower per liter? Why are off on this obtuse measure of performance? Are we building diesel engines?

 

Torque produced relates directly to engine efficiency (volumetric, combustion, etc). It's a measure of how effectively the engine uses the provided potential energy. Horsepower is a derivation proportional to torque and engine speed. Torque is the purer number, if you will...

[Gollum]

While I've been on the toque bandwagon before, it's always been because of one thing - POWER CURVE! People seem to really misunderstand torque and how it truly relates to engine performance. Even here we have Daemione guessing that F1 is possibly sacrificing torque for power. The only appropriate phrase that comes to mind is "complete bollocks".

 

People in the racing world will usually NEVER give up torque in the end. People might think that because race motors can be gutless when out of their optimum range, and people can say "well it's not torquey, but it's fast" which again is a pile of POO. Race engines have LOADS of torque they just shoot for it to be as high of a RPM as possible. You can't have a completely flat torque curve everywhere, which is part of why a F1 motor idles at 3,000. Does it make as much torque at 4,000 as other 3 liter motors? Probably not. But I bet it makes more torque than most other 3 liters when it reaches it's torque peak.

 

The only reason I've ever seen people actually give up torque figures, is for a BROADER torque peak in order to give them a BROADER HP curve. In this sense they're actually going for more "average usable torque" or "average usable power".

 

In the end, JohnC is right. But Leon is right too. Torque for the most part has no real value. HP is what moves a car and is ultimately important in most of our goals. We're not trying to move a 10 ton truck with a 20 liter diesel. We're moving a sub 2500 pound car in as spritely manner as possible. To do this we don't just want a ton of torque in a small range, nor do we want HP that is a fancy number but doesn't seem to do much. What we really want is a good POWER RANGE. And that's where I think torque can have it's place in this discussion.

 

I think we've pretty much shown that 200hp is possible sub 7,000rpm with pump friendly compression. But the real impressive side of this discussion is that it's so easy to obliterate the 200hp goals if you're willing to run a semi-race compression setup, that I think it could be interesting to know how soon you could reach 200hp in the RPM range with a more street minded setup. I bet it could be done at under 5,250 and done right could have a fairly flat HP curve from 5,000-6500 (on 2.8 liters). Now that could be a killer street engine. Even if you fell short and only had 180RWHP for over a 1,500rpm range that'd make for a killer performing car, well capable of getting a Z into the 13's which isn't a slow street car.

 

Just takes a well flowing head with minimal port enlargement combined with the right cam, intake and exhaust to all work as a system, then the system to tune it all.

[zredbaron]

It must be a blast to drive . . . and a very nice tq/l figure. But I'm guessing that a 12.5:1 compression race fuel engine is outside the boundaries of what the OP is looking at in his calculations. So I'm not sure it proves an exception to the streetable ~65 tq/l idea. But maybe 70 is a more realistic goal for a daily driver? :shrug: So hard to compare when all dynos are different.

 

It's a realistic goal for a daily driver, just probably more expensive than most daily drivers are willing to spend. My yester-year numbers support that 200hp is attainable for a street motor on pump gas (well below 7000 rpm). For a 3.1L, anyway. The peak numbers were there, but the curves aren't particularly flat. Felt far more flat as a driver than my race motor does, though.

 

So, further VE data points below. Always a 3.1L with Electromotive ignition, always with the same 40 DCOEs and street headers.

 

In 2003, crappy head job with a moderate street cam, pump gas. 10.5:1 or so? (E31+stroker) Flowmaster muffler (ugh, what was I thinking...?):

• 157 whp @ 5250, 176 ft-lbs @ 4500 (DynoJet).
• Per liter: 51 hp/L, 57 ft-lbs/L
• Theoretical at crank (again, 15%): 185 hp / 207 ft-lbs
• Theoretical per liter: 60 hp/L, 67 ft-lbs/L
• This motor was quick, but it wasn't fast. The torque was fun, though.
• 

In 2004, Sunbelt head with restricted cam, AvGas (bad idea IMO) (same compression as above motor). Magnaflow muffler (perfect sound in my book):

• 197 whp @ 6250, 186 ft-lbs @ 4750 (DynoJet).
• Per liter: 64 hp/L, 60 ft-lbs/L
• Theoretical at crank: 232 hp / 219 ft-lbs
• Theoretical per liter: 75 hp/L, 71 ft-lbs/L
• This motor was pretty fast on the street, and sounded great (loved the muffler). Enough power/torque to get squirrelly on street tires if I drove like a jackass.
• 

 

These motors were in my daily driver. The dyno numbers were with the AvGas, I later re-tuned it for 93 octane and it actually ran better. (I didn't understand how octane works at the time and blindly put it in the car thinking it would make more power. It ran better on 93 octane partly because of how octane works and partly because AvGas is inappropriate for performance cars that vary RPMs -- slow flame front propagation.)

 

From my tires and also my butt dyno's perspective, 65-70 ft-lbs/L was enough for the street (both motors). And although torque may be a metric of the engine, I agree that it's relationship with RPM does matter, because well, the 2003 motor was pretty weak in comparison and the acceleration just wasn't enough. The 2004 motor didn't ever leave me feeling like I lacked for power, therefore 75 hp/L was a hot street motor in my opinion. I autocrossed for a couple seasons with this motor and had more than I could put down on street tires. (I'm talking about the theoretical crankshaft numbers of course, because that's what I thought was being mentioned.)

 

It's cheaper to get good headers (better than MSA or Monza ), proper sized carbs (new), and Electromotive ignition (combined) than it was to build a Sunbelt / similarly prepared head. (Even after JohnC paid for all the R&D, specifically.) NA costs $...

 

[EDIT - Seems to me Rebello can produce significantly beyond these numbers via SU carbs / pump gas. Probably the cheapest/easiest/fastest route out there, not that I've ever heard a price. I'm surprised he doesn't seem to have any competition...?]

 

FWIW...

Edited September 24, 2011 by zredbaron

[Leon]

It's bedtime, but I'll put in a few words. Applications like F1 do sacrifice torque, it's not complete bollocks. In order to rev so high (~20,000 rpm), the stroke must be kept very short, thus the mechanical advantage on the crank is less. This equals less torque, but those engines spin so fast that the torque pulses to the crank are happening at a very high rate (more power). Really, when I see discussions like this there's always talk about torque does this, power does that, blah blah blah. Torque and power are related to each other by rpm. Whether you talk about torque or power, both of these things get a car moving.

 

What we should really be talking about is BMEP - brake mean effective pressure. This is a true measure of the effectiveness of an engine no matter the displacement and allows for a valid comparison. It shows how much potential (cylinder pressure) is being extracted out of an engine.

[Daemione]

What we should really be talking about is BMEP - brake mean effective pressure. This is a true measure of the effectiveness of an engine no matter the displacement and allows for a valid comparison. It shows how much potential (cylinder pressure) is being extracted out of an engine.

Maybe I'm missing something - but isn't BMEP just another way of calculating what we're already talking about? BMEP = 150.8 x TORQUE / DISPLACEMENT

 

 

Now, this is obviously a tangent . . . but definitely relevant to the overall engine approach for the best performance. Intake: Most of this discussion has used carbs as an example, but I, for one, am not excited about the idea of swapping carbs onto my fuel injected car (antiquated as the EFI system may be). I've read a lot on how the stock EFI manifold is the bottleneck in the system, but haven't found much on the most cost effective solution to the problem. Porting the stock manifold is of limited efficacy, and there's the lonewolf manifold, which gets pretty mixed reviews - and as far as I can tell isn't ideal for a NA application. Seems to me that there's a void in the market - a piece that supports some headwork and a bigger cam, but avoids the cost & pitfalls of designing your own, or the complexity & tuning requirements of ITBs. Bonus points if it makes an upgrade to Megasquirt mechanically simpler (throttle body & cable included?).

 

Anything I'm missing that's out there?

[Daemione]

So, further VE data points below. Always a 3.1L with Electromotive ignition, always with the same 40 DCOEs and street headers.

Awesome - thanks for all the data points . . . interesting stuff. Maybe it's just me, but I get the sense that a lot of info on this board has a "been there, done that" attitude, and information like this is becoming more and more difficult to find. e.g. every search I do simply brings up 100 threads telling me to search. Not to mention the 15 second "flood control" time out that makes finding specifics EXTREMELY tedious.

 

[EDIT - Seems to me Rebello can produce significantly beyond these numbers via SU carbs / pump gas. Probably the cheapest/easiest/fastest route out there, not that I've ever heard a price. I'm surprised he doesn't seem to have any competition...?]

I'd love to see some ballpark prices on a Rebello setup. I'm still at least a year away from this kind of work on my car, so nowhere near the point where I'm going to waste their time by calling them up. But I'm curious to know what to expect from a comprehensive build-up outfit like that.