200+ WHP NA build

[Gollum]

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.

 

Actually you're very correct regarding BMEP. It's a much "truer" measurement for efficiency than torque is. Maybe since our OP wants to talk hard numbers, maybe he should tell us what BMEP he's shooting for.

 

Regarding stroke and torque relation, I can agree to a point. I think it has an effect but not like people seem to think. What you loose in leverage you gain in flow potential for the given displacement, and if you increase the flow for a given displacement then BMEP will go up and subsiquently torque as well.

 

I know this might not be "scientific" enough for most people, but using a semi-accurate program we all know, dyno2003, I just built a motor to compare this will. I've got the valve size set to "auto" so that as I change things around the valve size would be approximately the same ratio to the bore and as valve size changes so will estimated head flow. So in this example we don't have a static head and flow numbers, which isn't "real world". I say that as a precursor to isolate the stroke/torque discussion. In the real world stroke is good because our head is static generally, and we get more displacement, torque, and power generally by doing so.

 

That said, peak Torque at 4" bore and 3.5" stoke (351 ci) is 451 at 4500rpm (79 lbs per liter, this isn't a mild motor).

 

Switching nothing but bore to 4.32" and stroke to 3.5" (351ci) the torque peak is 467 at 5500rpm (81 lbs per liter).

 

I know many people bag on this program, and I admit it's not the most advanced program out there. But it's also generally recognized that when used properly it can produce accurate information, showing that it's math formulas are fairly solid. I've replicated many dyno graphs fairly accurately by accurately entering data, but I can also see that it's just a tool in my box, not a law to live by. So people, please realize I'm just saying all this to bring up a point, which is that peak torque numbers have a lot more going into them than just displacement, or stroke, or both. I've seen people blindly say that stroke is the main factor in torque (which I don't believe is what Leon is saying) and I've seen people say that displacement is the only factor in torque (which is not what I'm saying either). Though both of those play a crucial role, there's many things that make up a good 10-20% of your torque figures.

 

 

For reference, the motor example given had a 10:1CR, 800cfm rated induction system, sequential fire injection, large tube open headers, cam with .614 valve lift and 286 duration and 110 lobe seperation. I believe a similarly built 351 would be close in numbers, and I've seen it done. Reason we don't see many actually put out 450+ torque and 470+hp like this simulation did I believe is largely due to lower compression and poor intake design with a carburetor that's not great at flowing evenly to each cylinder. This simulation is assuming that each cylinder is getting exactly the same air and fuel, which doesn't happen without very well designed induction and fuel systems. By comparison these numbers perfectly line up with what a LS1 should make with a similar cam, which is basically what this motor would be. The biggest difference would be the exhaust at that point which is about 25HP difference according to dyno2003. That said we have people ON THIS VERY FORUM putting 400+ to the wheels in LS1 motors... some even still get 30mpg on the highway, those bastards.

[Blakt Out]

Guys:

 

I'm actually about to start building another 240Z, and I'm reading around now doing research on here. I think I'm going to go with a streetable, ITB L24 with 215-230WHP as a goal. Like the OP, I very much appreciate that higher rev range. I think that many of you might be missing the point of the higher revs... at least MY point with it.

 

I have been blessed with the job of test driving Porsches and writing about them (Excellence Magazine - World's Largest Porsche Mag). Testing numerous different 911s in solid 3 day sessions on rural roads (attacking the roads cannot be overstated), I've come to appreciate the higher revving cars (ala 2011 GT3-RS) because you can stay in 2nd gear (still on throttle) into the braking zone of the next tight turn instead of having to grab 3rd for a blip of the throttle before braking and downshifting. When figuring in shifting and such, the car that can stay on the power longer and without having to shift is faster. So this is what I'm researching. Yes, I'm reading all that I can on here, but since my desires seem to be on point with that of the OP, please feel free to tell me what you'd suggest as far as heads, CR, cam, etc.

 

Thanks!

 

Jared Cullop

www.jaredcullop.com

[JMortensen]

I have been blessed with the job of test driving Porsches and writing about them (Excellence Magazine - World's Largest Porsche Mag). Testing numerous different 911s in solid 3 day sessions on rural roads (attacking the roads cannot be overstated), I've come to appreciate the higher revving cars (ala 2011 GT3-RS) because you can stay in 2nd gear (still on throttle) into the braking zone of the next tight turn instead of having to grab 3rd for a blip of the throttle before braking and downshifting. When figuring in shifting and such, the car that can stay on the power longer and without having to shift is faster. So this is what I'm researching. Yes, I'm reading all that I can on here, but since my desires seem to be on point with that of the OP, please feel free to tell me what you'd suggest as far as heads, CR, cam, etc.

A couple hundred rpm on a less powerful motor is probably a worse compromise than a taller gear on a more powerful engine. The functional rpm limit of an L series doesn't change very much from L24 to L28 or stroker. I would suggest you go for the bigger motor and gear it to where you want it.

[Blakt Out]

Wow. OK. Good advice (sounds like it). I was imagining we were talking about 8k with an L24, maybe 6800 with an L28, and 6300 with a 3.1-3.3L. Bad assumption? If it's really a few hundred rpm, I totally agree and need to change my searching (and find a block).

[JMortensen]

Yes, that is a bad assumption. You can read on harmonic dampers and look at cars with broken cranks and try and decide where you want your rpm limit. I wouldn't hesitate to turn any of them to 7K, and I would hesitate to turn any of them too much higher, but you can take a look and see what kind of risks you're willing to take, and what kind of rebuild intervals you would like to have. The subject has been discussed many times before. Search for things like rod/stroke ratio, valvetrain stability, crank harmonics, etc.

[duragg]

Got a few months of driving my hopped up NA motor now and I gotta say its a blast.

10.3CR on an F54 block / N42 head with a little tidy-up, Total Seal rings, Triples, modest cam (grrr).

 

It growls and pops and snarls something wicked. Really something you live with.

 

Feels like twice the power of the L24 that it replaced.

Wheelspin is now a problem - versus a surprise.

 

34mm Chokes in the DCOE and by about 6500rpm its ready for a shift.

Having the 1983 style 5 speed is SO much better than my earlier 5 speed with its better ratios.

 

Someday maybe a different cam and slightly bigger carbs but for what? Just to make a bit more power at 7000rpm?

The midrange is really strong still (willing to give up some of that).

Wideband makes tuning a snap.

 

I do run a mix of 100LL and 91 pump gas for safety and so I can run lots of timing.

[zredbaron]

It growls and pops and snarls something wicked. Really something you live with.

 

I disagree. If I can get my race motor to sing and decel without any popping, then anyone's motor can too. [EDIT - Assuming the ports are reasonably consistent and all is in good working order, of course.] I'll be uploading a recent tuning session onto the Weber sticky soon to make this very point. We (Weber users) tend to forgive ill tunes and write them off as the limitations of carburetion when in fact its the limit of the tuner and/or their arsenal of jets. I accepted a poor tune for years, until I finally figured out how to properly tune my own carbs. Strong ignition and quality fuel can make all the difference in the world.

 

Where I feel the carbs cannot compete with FI / ITBs is that odd rpm range around 3000-4000 rpm (depending on motor). And of course driveability since a good FI setup accounts for both throttle position and vacuum.

 

WOT, my Webers have served me quite well...

Edited October 3, 2011 by zredbaron

[duragg]

I disagree. If I can get my race motor to sing and decel without any popping, then anyone's motor can too. [EDIT - Assuming the ports are reasonably consistent and all is in good working order, of course.] I'll be uploading a recent tuning session onto the Weber sticky soon to make this very point. We (Weber users) tend to forgive ill tunes and write them off as the limitations of carburetion when in fact its the limit of the tuner and/or their arsenal of jets. I accepted a poor tune for years, until I finally figured out how to properly tune my own carbs. Strong ignition and quality fuel can make all the difference in the world.

 

Where I feel the carbs cannot compete with FI / ITBs is that odd rpm range around 3000-4000 rpm (depending on motor). And of course driveability since a good FI setup accounts for both throttle position and vacuum.

 

WOT, my Webers have served me quite well...

 

Sorry to hear your motor does not growl or snarl... mine does, with virtually perfect 12.5AFR throughout.

But my tune probably sucks...

[zredbaron]

Sorry to hear your motor does not growl or snarl... mine does, with virtually perfect 12.5AFR throughout.

But my tune probably sucks...

 

I fixated on your use of the word "pop" which I interpret as excess fuel igniting as it passes through headers at temperature. Growl and snarl are of course subjective.

 

If you're happy, that's what matters!

[duragg]

Love the motor.

Hate the cam. I got talked into a "reasonable" cam which wasn't my desire and I didn't know better.

I wanted a stupid cam and now I need to go back and get one...

[Tony D]

Wow. OK. Good advice (sounds like it). I was imagining we were talking about 8k with an L24, maybe 6800 with an L28, and 6300 with a 3.1-3.3L. Bad assumption? If it's really a few hundred rpm, I totally agree and need to change my searching (and find a block).

 

 

Oh Christ!

 

Try THESE numbers for 'runs and doesn't blow apart guidelines' (and we haven't actually floated a damn valve yet):

 

12,500 for an L20A

9750 for an L28

8700 for a VO7 Stroked L29

 

And in EVERY case above, we stopped because either the tachometer didn't log higher or we were plenty past the power peak that we've determined further increase would be pointless other than to know we just need a bigger cam or more boost to make even more power at the higher rpms.

 

8K with an L24 isn't even getting STARTED as far a 'maximum allowable RPM's'! (Do a little linear interpolation between displacements...) You're selling yourself WAAAAY short with THAT assumption for SURE!

 

And guess what? An L20A running 9750 rpms IS NOT going to give a comparable proportional HP as the L28 running 9750 (or for that matter the L28 turning 8250...even if you take the L20A to 12,500 trying to make up porportional RPMs through some theoretical increase in RPMS to compensate for displacement....)

 

If you have forged pistons...you have (from what I've seen) really no practical upper RPM Limit.

If you have cast pistons, your upper limit is around 7000 rpms. Run them at 8K and you are going to get an engine that "Sounds like icecubes in a blender" at idle before not to long--if not worse.

 

The cam determines how and where you will make the power. The pistons will determine if you can run to that point or not. Arguments for larger cams that provide more 'power under the curve' being used in Cast-Piston engines do have a valid argument for their employment. BUT if the engine revs so willingly with that big cam in there, I've not seen ONE person who doesn't try to see when it stops pulling. And the engine goes 'boom'...either spectacularly, or 'ice cubes in a blender' kind of way.

 

Almost 100% of the Internet Commentary about 'RPM Limitations of the Datsun L-Series Engine' is pure, unadulterated BULLSHITE! There is no other way to put it. It's bad information. I've personally seen this myself. On the dyno, on the track, on two continents.

 

You don't need forged pistons OR 7500 to get 200 N/A horsepower out of an L28. Likely not out of an L24. If you need a couple of hundred rpms at a particular track, you gear for it. If you are in serious competition, 7500 IS NOT a limit on a built-up L Series Engine. The much-vaunted Crank Harmonics issue is a holdover from the early L24 noncounterweighted cranks. While a harmonic DOES indeed exist there, it is easily squelched sufficiently with a proper damper, and the knowledge that ANY harmonic is adequately worked THROUGH by not DWELLING on the precise speed where the crank resonates. Pass through it and you're up there quite high before the crank hits a second critical speed. And yes, they can operate there all day long, though parts do take a pounding.

 

Which brings us full circle that you don't NEED High RPMS to get most horsepower goals. 320 at the rear wheels on a 0.040" overbored L28 is achievable (in our case) at 8250 RPMs in a dedicated race vehicle. Rebello is making far more than that at far lower RPMs with his Stroker 3.0's for similar competition.

 

Can we kill the maximum RPM myth here and now? PUH-LEEZE?!?!?!?

 

As for Weber Service---I will agree. At WOT you will see great power from them. In our case, it was simple economics that the cost of 55 DCOE's with their special manifold were cost-comparable with a set of 45mm ITB's. It came down to 'what will be more versatile long-term?' The 45mm ITB's work great on our 2 Liter. They work great on the 2.8. If we had sold our 45's to get the 55's (which was the plan) we would have had to go out and buy another set of DEDICATED carburettors for the small engine. Our power production was smooth and the dyno chart looked like someone drew a fashionable eyebrow with a felt pen when running the Webers. I'm sure with 55's the curve would have been similar in format (nice even curve) rather than the somewhat digital jerky interpolation with the EFI. But comparing 45mm Carbs to 45mm ITB's the EFI gave 17 more HP at the Carbs power peak of 7500, and 40 more HP at an elevated RPM range of 8250. Nothing else changed, direct swap from Weber 45's to ITB's and Electramotive TEC2. No different cam, nothing. It made more power everywhere. Even with the 'strange dip' in the Dyno Curves we are still trying to figure out lo these 6 years later, and present in two different EFI systems...the EFI is still making more than the carbs did at those points...and even more elsewhere. We liked our Webers, it was just too damned expensive for a set of carbs that couldn't be used on ANYTHING else.

Edited October 3, 2011 by Tony D

[Tony D]

Oh, and a comment on the venturi sizing stated in the Weber Example above for an L28...

 

It's stated 'bigger carbs' may make more power. Change your venturi from a 34 to a 36. A 34 is NOT a 'top end' venturi...this goes to the other comment about poor tuning I suppose. A 34 venturi in a 45 DCOE is a mild street setup, and not for max power. Then again, running a 12.4 AFR everywhere isn't exactly how you get maximum power either. But it will give you pops, growls, and snarls if that's your thing! (Hint: Try pulling fuel after peak torque to around 13.8 AFR instead...you're WAY richer than you need to be on the top if you are serious about getting power at higher RPMS...maybe that's why it's feels all-in so early!)

 

If you are talking about bigger carbs being 50's...you need to maximize airflow through what you got first.

 

If you are talking about bigger carbs being 45's...you aren't set up for power, period. The carbs are the limiting factor, not your cam! AIRFLOW makes power, and small venturis and small throttle plates just won't cut it. I ran 44PHH Mikunis with 32mm Chokes on my L20A in Japan, and the power would come up high and pull like crazy with a surprisingly small camshaft profile.

 

Many people would be shocked to see how 'small' our cam profiles are for the above power examples. I've seen people on here with street engines that have cams with more aggressive specifications than what we are running in competition, AND making considerably less horsepower.

Edited October 3, 2011 by Tony D

[duragg]

Cam timing.

Please explain in general?

 

I just realized today we setup my new cam at #3 position (so I didn't lose too much midrange?).

But the midrange is way too strong and by 6500rpm (at 13.3AFR ish) the peak is gone.

 

What change might be expected in general going from #3 to #1?

 

PS- Having a strong street motor isn't all bad. Running around on the street pounding up to 8300+ sure seems like you would be getting some unwanted attention, but sure sounds fun.

 

This mild-build L28+.040 is a pretty cheap and fun street setup.

Will get to the dyno soon for grins, althogh my stock R180 is starting to make some noises already...

[Leon]

Going from the #3 hole to the #1 hole on a stock cam sprocket will retard the cam. Retarding the cam opens and closes the valves later, shifting the torque (and subsequently power) peak to the right (higher rpm). You have 4 degrees of adjustment per hole, so a fully adjustable timing sprocket will let you dial it in further.

[johnc]

In the SCCA ITS racing world it was somewhat common to hold full throttle between 7,000 and 7,300 rpm for 5 or 6 seconds at a time on each lap due to the transmission limitations in the SCCA rule book. That's with cast pistons and a stock damper. Cranks do break from that use especially if the damper is old - I've seen it and I've seen a damper pop off the front of the crank, go through the hood of a car, and into the windshield of the third car in the line racing for turn 1. That's where a lot of these crank harmonic rumors came from. There are also the fools who used to remove the damper completely and replace it with an aluminum under drive pulley set. Still very common in the BMW world and you see posts weekly on Bimmer Forums from people wondering why their crank snapped between 3 and 4.

[Tony D]

Proper Dampers are required on the snout, and that works in conjunction with flywheel/package weight as well.

 

But like John C says: stock engines insomuch as cast pistons and stock (crappy) dampner!

[ZIPPY]

I've got a mostly stock 260Z that is a typical "sunny day" car - but lately its been upstaged by my new daily driver - an RSX type S. Fortunately I just dropped my daughter off at college for her last year, so come spring I'll finally have a few bucks to sink into the Z. My goals are more subjective than logical:

• Feel faster than my RSX.
• Run triples. I know I'll probably get tired of tuning carbs and swap to ITBs or something, but I've lusted after Webers (or Mikunis, Dels, etc) for a long time.
• tHave a usable redline north of 7K RPM. I know its more efficient to make power at lower RPMs but I want to hear an exhaust note that makes me feel like I'm Paul Newman at Limerock.
• A smooth idle and linear throttle response.
• Run on 93 octane.

The RSX weighs about the same as an S30 and according to the internet puts down around 165-170 whp, so I'm thinking I want about 200-210 whp, or approx. 250 crank hp. I've been searching the internet and doing back-of-the-envelope estimates to figure out how to do that. What I'm leaning towards is (roughly) 88.5mm bore L28, stock L28 crank and rods, high-silicon forged flattops, 10:1 CR, quench head, 45mm triples, mild cam (aprox .490 lift, 270 duration). Mild cleanup port on the head - unshroud the valves - but don't go too big on the port to keep velocity up.

 

Basically a mild stroker build without the long crank (to give me my 7500 RPM redline without radical porting).

 

Things I couldn't find good answers for:

• Best way to get a 10ish CR with a quench head? Can an MN47 be opened up to 46cc combustion chambers? I'm nervous about the shim-n-shave mode for the P79; all those shims stacked under the cam-towers seems a little scary at 7500 RPM... Maybe go with the Kameari idler gears and adjustable cam gear?
• Is there any benefit to using L24 rods with the L28 crank? I've plotted the piston velocity curves with both rod-lengths and the extra 3mm just doesn't seem to amount to much? Keeping the shorter rods might actually help by creating more intake "vacuum" early in the intake stroke to squeeze a little more flow out of the carbs (45mm seems a little on the small side for a 250 hp motor). Any real world experience here?
• Undoubtedly lots of things i haven't thought of yet... I'm trying to settle on a block and head before I get into more details.

Opinions, ideas, experience welcome.

Don

 

 

Wow that was a lot to read... This thread is just as full of very useful information as well as usless BS bantering. I guess thats one of the joys of forum engineering.

 

Anyway, BS aside I'd like to reply to the original posters question about a 200whp daily driver. You are describing almost to a T my currant engine setup. It is a ZX block (F54 i think), P79 head, cast ITM 87mm flat top pistons, prepped stock rods, schneider cam and SU carbs. And yes I hit 7500rpm reguarly. Infact the last two times at our local parking lot drag strip I had the rev limiter set at 8000rpm and dug into it heavily a couple times. I was shifting out of second at around 7800 - 7900 mostly because my gearing is a little weird (t5 and 3.90). The only chance I had to dyno it was a the MSA Z bash last year. It made 196rwhp at 6200rpm and peak torque was 180 at 5000rpm... Remember this is with SU carbs. The parking lot air temp was like 110 and the carbs were out of sync. Oh yea, and cali 91 octane. In the vid you can hear it pinging some mostly due to there being no cooling fans and the engine was fairly hot, also I think the timing was a little over advanced. I'm pretty sure it makes decently over 200whp properly tuned at the rpm I usually shift at.

 

I will gladly provide more info if it will help you build an engine that meets your goals.

 

Here is a video of the dyno pulls I made. Watch to the end and you will see the dyno sheet.

 

 

 

EDIT - I should add that it is still a 2.8L and was daily driven until I took it apart a couple months ago.

Edited October 31, 2011 by ZIPPY

[Xnke]

Also; as I've stated before in other places, testing DID show significant harmonics in the range between 7000 and 7800RPM with the L crank. The one about 7500RPM I believe is mostly a torsional vibration, due to the long crank. Fully counterweighted or not, it's still there. It was also the biggest spike on the chart. TonyD has posted the fix for this many times, a quality damper, as light a flywheel/clutch assembly as practical, and DON'T dwell in the danger zone! Zing it through that range as quick as possible and don't worry about it.

 

As for practical limits...I wish I'd spent the extra money when I built my engine and loaded it with forged pistons. As it is, I have ITM hypereutectic cast slugs in it, and it will snap the needle off the tach, given a rev from 2.5K. Until it hits the revlimit at 7000RPM, that is. Is it the snappiest rev I've heard? No. But it is a 17lb flywheel and full stock clutch still.

[Tony D]

"I wish I'd spent the extra money when I built my engine and loaded it with forged pistons."

 

I am included in this same regard with my last 'bought' VW overhaul...didn't think I had the money for the counterweighted crank to allow reliable revving over 5K, and the way it runs, I've been sorry now for about 68,000 miles! When this one dies, the CW Crank will go in, and I once again will have an 8500 rpm Turbo T1 Bus!

 

Shifting at 5000 sucks! Especially when you've tasted the fruits on the other side of the fence!

[zredbaron]

As for practical limits...I wish I'd spent the extra money when I built my engine and loaded it with...

 

[As a single man] Of all the vices in life, none have made me more happy [consistently, vice pinnacly] than money spent on engine (and suspension) performance of my S30.

 

It may be "only 13 years" thus far, but it remains emphatically true. For what it's worth...

Edited November 2, 2011 by zredbaron