Newbie seeking advice - what is the best L engine/head combo

[JMortensen]

Was looking at How to Modify and I noticed a couple things:

 

The FIA L series heads have a big quench area and a heart shaped chamber. Stupid Nissan. How could they let themselves get sucked into this decades old quench "fad". You'd think they'd know that quench doesn't matter on the L series; everyone knows that's just for V8's.

 

Also, Devendorf's IMSA GTU L28 used, get this, 140mm rods. Looks like he used 133mm rods in his GTO turbo car. Looks like he was going for that bogus rod ratio of 1.8. What a dumbass. Too bad Dan wasn't there to keep him from falling into that whole rod ratio trap.

 

Too bad I can't back up my points with any "proof".

[DAW]

You can lead a horse to water...turns out there are horses that you can't even lead to water. DAW

[z-ya]

What would lead me to water would be proof that a P head is superior to an N head in an L6 application. So, when you guys finish building your engines, get them on the dyno, and post the results. If the results show that the P series head produces significantly more HP than a similar L6 with an N series head, then I will bow to the almighty P design. I gues this would be the only way to really settle this.

 

I have a P79 and N47 on the shelf, so I could combine those to make a P79 that I could swap onto my N47/F54 race car the next time I need to tear it down. But that would kind of go against why I used the N47 in the first place: a budget L6 with good performance.

 

Best Regards

 

Pete

[Dan Baldwin]

Jon, DAW,

 

Show us what YOU'VE done. You guys have NO IDEA what you're talking about.

 

I can't believe I have to repeat my basic points YET AGAIN. I should really shut up, as the more sophisticated forum members can clearly see the evidence and draw logical conclusions on their own. But you guys CONTINUE to actively mislead unsuspecting netizens down your misguided path of placing FAR too much emphasis on things you have NO REAL UNDERSTANDING of.

 

Regarding "quench":

To illustrate P-head superiority due to "quench", you have to provide evidence for at least TWO points:

1) That "quench" is absolutely critical to make power

2) That the P-heads inherently have or impart "quench", and that the N-heads inherently do not.

You've provided indirect evidence for point #1, and I won't argue on a subject I know very little (probably just about as much as you) about. But you've provided no real evidence for point #2.

 

If we assume for the moment that point #1 is true, I say that results indicate that "quench" can be had with the N-series heads, based on SOLID IRREFUTABLE EVIDENCE:

A) 11:1 CR pump gas 255rwhp 3.1 liter

10:1 CR stock cam, totally stock head, pump gas 164 rwhp 2.8 liter

C) 13.5:1 CR race gas 287rwhp 3.0 liter

D) 11.2:1 CR pump gas 2.9 liter 240Z running 12.8x @ 107.x in the 1/4 (this engine *did* have detonation issues at 11.6:1 on pump gas, I must admit!)

 

What conclusions do you draw from this evidence, regarding "quench"?

I myself am not too worried about it, and only draw the conclusion that you can indeed run high compression ratios and make GOOD power with the N-series heads.

 

But you continue to argue as if your SUPPOSITIONS on the subject are more important than real-world results! You are WRONG.

 

jmortensen, mocking me :

You'd think they'd know that quench doesn't matter on the L series; everyone knows that's just for V8's.

 

I NEVER SAID THIS. That was NEVER my argument. If we're going to have a civilized discussion you have GOT to quit misrepresenting/mischaracterizing what I've said.

 

 

 

Regarding rod/stroke ratio:

 

jmort again:

Devendorf's IMSA GTU L28 used, get this, 140mm rods. Looks like he used 133mm rods in his GTO turbo car. Looks like he was going for that bogus rod ratio of 1.8. What a dumbass. Too bad Dan wasn't there to keep him from falling into that whole rod ratio trap.

 

DAMN, you continue to ACTIVELY ignore my point! I'll agree in a second that, theoretically, longer r/s ratio should be better due to slightly higher redline potential, reduced parasitic losses from piston side load. In the real world, there will always be a point of diminishing returns, though. Also, there IS improved rod/crank angle to be had with SHORTER r/s ratios.

 

MY POINT on this issue is that the ACTUAL performance benefits of going from ~1.6 to ~1.8 r/s are most likely NEGLIGIBLE, and CERTAINLY not worth experimenting with trying to fit a taller, heavier, higher-c.g. LD28 block into a Z. In Formula 1, I believe they're over 2:1, r/s. BUT, they can design from a clean sheet of paper, and they'd kill their mothers for another 50rpm up top! I am not too concerned about tens of rpm up top, and besides L6 redline is reportedly more a function of crank harmonics than absolute piston acceleration.

 

 

Practical real-world results TRUMP the theoretical ramblings of non-experts every single time. You guys don't have JACK.

 

NOW BOW DOWN AND WORSHIP ME

[JMortensen]

2) That the P-heads inherently have or impart "quench", and that the N-heads inherently do not.

You've provided indirect evidence for point #1, and I won't argue on a subject I know very little (probably just about as much as you) about. But you've provided no real evidence for point #2.

 

Dan--READ the links. They tell you EXACTLY what factors need to be in place to have quench. You DON'T have it.

 

OK Dan, this is all I can do to actively prove my point to you. This is my last shot at delivering you from what I can only describe as beligerent ignorance.

 

My current build:

 

Stock 2.8 bottom end with flat tops no overbore (notched the block, removed the casting, balanced, but that's it)

12 lb flywheel

euro damper

E31 head, ported and polished by me, 280 valves

490/280 cam

44 mikunis on Cannon manifold

MSD running through ZX dizzy

 

The closest I've come to a dyno was a G-Tech test, because I've never had money lying around that I didn't want to use to buy something to make the car faster. The clutch was slipping BAD, as I was still running the stock clutch at the time. I had a buddy in the car, so the weight of the car was 2660 lbs. ET 15.5. Trap speed 108.

 

According to this calculator: http://www.speedworldmotorplex.com/calc.htm

 

I'm putting down 266 hp, 11 MORE horsies than you!!! Now most people say that the Gtech is a little high on its trap speed, couple mph anyway. Lets drop it down to 104. Now I'm putting out 234 at the wheel. Since you have a 10% displacement advantage if you knock your number down it would be 229.5. So I'm STILL putting out more than you per liter.

 

I'm not saying that I totally believe these numbers. If I were to estimate my rwhp I'd say 225. But I've got a total of about $1700 in my motor. How much do you have Dan???

 

If you want to tell everyone how to build an $8K (guessing) motor that puts out 82hp/liter fine. I'm not telling them not to. I'm just saying that there might be a small advantage in the quenchy head. There might also be a small advantage in the rod ratio. I'm sure I have a small advantage in the way that I notched the block to match the unshrouded head, and the way I blended the seats into the chamber. If I told someone such as yourself about the number of hours I spent doing those things (it was over 40 easy), you'd probably have told me it was a total waste of time. But IMO it is not. Every little bit counts.

 

The only track proof I have is I know that I was within 2 seconds of Mike Eckhaus's best time at Buttonwillow when my motor was in a really bad state of tune and it was 105* on the day I was there, and he's supposed to have crazy hp. More than you.

 

I think you let that one dyno sheet and all the compliments you got from it go to your head. Your motor is impressive. Don't get me wrong. But since you've built it you've become the self appointed authority on rod ratio and quench, NEITHER OF WHICH YOU'VE USED.

 

I didn't want to use my "evidence" because I know it is half-assed. But my 1/2 assed evidence shows that there just might be another way to build an L series engine.

 

EDIT--FORGOT TO MENTION, GTECH AND TRACK RESULTS WERE WITH MY PREVIOUS LOWER COMPRESSION ENGINE. WENT FROM 8.5:1 TO 11:1, I HAVE YET TO GET ANY PROOF OF THE INCREASE IN POWER I CAN FEEL ON THE BUTT DYNO.

[Guest bastaad525]

 

 

Welp, bottom line for me is a) there never will be any 100% proof one way or the other, which head is better... no one will bother to really go to the trouble to test it at the level it needs to be tested to confirm, and even if someone dynos a setup with each head, it would doubtlessly just spark more debate... is it really doesn't matter, most people will just go with what they have available to them, or what they can afford... Those who can freely choose know enough to make their own decisions on what they choose to believe c) I'm never going to build another N/A motor so what difference does all this make to me anyways And for that matter I will always advise any person that if they are gonna spend the money to build an N/A motor they could spend just as much and come back with a turbo motor that will outperform whatever N/A motor they were going to build.

 

 

I apologize for opening or contributing to the opening of this eternal can of worms.

 

Hey at least we kept it (mostly) civil ... what a GOOD HybridZ debate should be... no need for Mod intervention here no siree!

[JMortensen]

Hey at least we kept it (mostly) civil ... what a GOOD HybridZ debate should be... no need for Mod intervention here no siree!

 

Well I've actually lightened up. Yesterday I was taking it too personally. Today I laughed when Dan said BOW DOWN BEFORE ME. I guess maybe my sarcasm wasn't evident in my last post.

[Dan Baldwin]

 

Dan--READ the links. They tell you EXACTLY what factors need to be in place to have quench. You DON'T have it.

 

Let us suppose for a moment that you, God of Quench, are right, that quench is a binary type of property, you either have it or you don't, and that my engine does not have it. Consider: 215-220 rwlb-ft from 4700-6100rpm, and 255rwhp @ 6500, from a 11:1 CR 3.1 liter engine running on pump gas, tuned by ME, a RANK amateur. *If all the above is true*, I can only conclude that quench can't be all that important, PARTICULARLY for people asking about what they can do practically, easily, and cheaply to get some extree ponies (see original post).

 

[note: if you get the subtlety of the above paragraph, you will recognize that it is not necessarily an argument against quench ]

 

Looks to me like, with a stock gasket, your L28 flat-top/E31 CR *should* be ~least 10.2:1, or are you saying the GTech results were with dished pistons?

anyway:

 

2660 lbs. ET 15.5. Trap speed 108.

 

Woohoo! I guess the clutch WAS slipping! I think GTech sez they typically read 3mph high, =>240 at the wheels. ASSUMING Gtech accuracy, AND assuming that is a good rwhp estimate.

 

Looks impressive, particularly if it was with a 8.5:1 motor.

 

I'm not saying that I totally believe these numbers.

Me neither!

 

If I were to estimate my rwhp I'd say 225. But I've got a total of about $1700 in my motor. How much do you have Dan???

 

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Original build was ~$1700, then $1500 for the head modification and cam setup, $600 for carbs, that got me to 235rwhp. Rebuild last year was VERY expensive, mainly because I had the money and the engine was in Virginia, so I just paid $$$$ to have an experienced GT-2 L6 engine builder do EVERYTHING, including machining valve reliefs in the pistons and multiple mock-ups of the assembly to ensure clearance while maximizing CR.

 

No doubt had I had the skeelz, shop space, equipment, and the time, I coulda saved a BUNDLE!

 

If you want to tell everyone how to build an $8K (guessing) motor that puts out 82hp/liter fine.

 

FWIW, my motor could be built for WAY under $8k. I'm perfectly willing to tell what I've done, but I've never tried to say that's the only way.

 

I'm not telling them not to. I'm just saying that there might be a small advantage in the quenchy head.

 

And *I'm* saying that in most cases (this post included) *I* think they're better off just plopping an unmodded N42 or N47 on a flattop bottom end. Most of these people don't have machine shops in their basements. Your advice is going to send them to the local speed shop (with only an *inkling* of an idea what they *think* they want), which is as likely as not going to butcher what was a decent cylinder head, while charging them outrageously. All for VERY little gain if any at all (depending on the shop, could be a BIG loss of both power and $$$).

 

There might also be a small advantage in the rod ratio.

 

Agreed, there might be. I just don't think it's worth monkeying around with an LD28 block.

 

If I told someone such as yourself about the number of hours I spent doing those things (it was over 40 easy), you'd probably have told me it was a total waste of time.

 

No, but I might ask what you think your time is worth! I also have to question your methods a little, as you apparently don't dyno to see what you've lost or gained, and where. That said, I don't think your doing your own work and putting in the hours is any more wrong than my decision to pay those who already have TONS of experience with the L6 to do most of the work for me.

 

The only track proof I have is I know that I was within 2 seconds of Mike Eckhaus's best time at Buttonwillow when my motor was in a really bad state of tune and it was 105* on the day I was there, and he's supposed to have crazy hp. More than you.

 

I'll take the GTech results (with a grain of salt, of course!), but the above sentence can't be construed as any sort of evidence of engine performance, IN THE SLIGHTEST. First of all, 2 seconds is like an eternity, there's no telling what your motor being "in a really bad state of tune" REALLY means, he is " SUPPOSEDto have crazy hp"?! Not to mention the HUGE contribution of driver skill and car setup. There's just NO WAY to take your paragraph and make ANY kind of quantitative estimation of your hp relative to whatever "crazy hp" is!

 

you've become the self appointed authority on rod ratio and quench,

 

Not at all, I *KNOW* I'm not an authority. I just don't think you guys are either!

 

I didn't want to use my "evidence" because I know it is half-assed. But my 1/2 assed evidence

 

Sheesh, I can understand your reluctance now that I've seen it! The last bit, anyway. I'd call the Buttonwillow "evidence" 1/100th assed! GTech evidence, maybe 2/3-assed. Maybe... Won't get into "butt dyno" reliability, but going from 8.5 => 11:1 should be worth quite a bit.

 

shows that there just might be another way to build an L series engine.

 

I've never disputed this. My point remains that for just about all intents and purposes, if you wanna build a strong NA L6 the EASY way, flat-top bottom end + N42 or N47 head is pretty much the way to go. And if you wanna build a stroker, the basic LD28 crank, L28 block L24 rod, KA24 piston combination is easy and works pretty damn well, too.

 

Now get to a fricking dyno, it ain't THAT expensive.

[JMortensen]

Let us suppose for a moment that you, God of Quench, are right, that quench is a binary type of property, you either have it or you don't, and that my engine does not have it.

Thank you for getting the title right. 'Bout time you showed some respect.

 

First of all, 2 seconds is like an eternity, there's no telling what your motor being "in a really bad state of tune" REALLY means, he is " SUPPOSEDto have crazy hp"?! Not to mention the HUGE contribution of driver skill and car setup. There's just NO WAY to take your paragraph and make ANY kind of quantitative estimation of your hp relative to whatever "crazy hp" is!

 

Yeah, that is a pretty crappy comparison, but it's all I've got.

 

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You missed my point. My point was that I have a grand total of about $1700 in the machine work on my engine. If you include the ancillaries I've probably got $2500 total in mine.

 

No, but I might ask what you think your time is worth! I also have to question your methods a little, as you apparently don't dyno to see what you've lost or gained, and where.

 

I did it because it was fun. You're right, I haven't dynoed, so I can't see where improvements were made. I can only say with some assurance from my ass that there were improvements.

 

Now get to a fricking dyno, it ain't THAT expensive.

 

Cars on jack stands and will be for a while yet, and even if it wasn't, there are so many other things I want to buy before I spend time on a dyno that I can't see wasting the money on it. I'm spending some real $$$ on my car for the first time in 4 years, and I'm running very overbudget already trying to get a number of projects done.

 

If and when it gets to the dyno, you'll be the first to know.

 

EDIT--Gtech stuff was with the dished .020 over pistons on the first motor.

[Dan Baldwin]

Hey, WAIT a minute! I already let you pretty much get away scott-free with STEALING John's and Norm's astounding results from my side of the argument, although they use N42 heads. No way I'ma let you throw in your results with an E31 and say that's any kind of evidence of P-head superiority! NO WAY!!!!!

 

Speakin' of which, if an N42 can be made to have the supposed "quench" characteristics you describe by machining it down the same amount you HAVE to machine the P90 down for an na ANYWAY, then I REALLY don't see how you can argue, from your quench premise, P-head superiority over N-heads in the first place!

 

I've had all I can STANDS and I can't STANDS any more!

Where's me spinach?!

 

DAYUM I'm a sucker...

[JMortensen]

I used my E31 because it has a bunch of quench. Not a perfect correlation, but it was also just a way to show to anyone who reads this that you don't need the dogmatic F54/240/KA24/HKS/N42 to make hp. It was more a response to your BOW DOWN AND WORSHIP ME thing. The BOW DOWN thing is my problem with your argument. It is always "well I made x by following the formula" or "why WASTE time and money on an impractical experiment that will have no real benefit" and you really don't know that these things have no benefit, nor that they are impractical. For instance, how hard would it be to lower an LD block an inch in the chassis. I think I could get that done in fairly short order.

 

Speakin' of which, if an N42 can be made to have the supposed "quench" characteristics you describe by machining it down the same amount you HAVE to machine the P90 down for an na ANYWAY, then I REALLY don't see how you can argue, from your quench premise, P-head superiority over N-heads in the first place!

 

This is what I said:

But for the average guy who wants to slap a head on a block with flat tops, run pump gas, and get the best result, I don't think you can beat the P90 shaved .080.

 

Correct me if I'm wrong, but if you shaved an N42 you wouldn't be able to run pump gas. Right? So in order to get a significant amount of quench out of the N42, you'd need to run race gas.

 

The other advantage to the P head that I haven't been able to verify is the height of the intake ports. We didn't even get into this yet, and I almost don't want to, but supposedly the intake ports are located higher on the P90 which makes for a longer short side radius. I'm sure I don't have to explain the benefits of that to you.

[Dan Baldwin]

just a way to show to anyone who reads this that you don't need the dogmatic F54/240/KA24/HKS/N42 to make hp.

 

And I never suggested that.

 

It was more a response to your BOW DOWN AND WORSHIP ME thing. The BOW DOWN thing is my problem with your argument.

 

BOW DOWN BEFORE ME. BOW or receive my WRATH.

 

It is always "well I made x by following the formula" or "why WASTE time and money on an impractical experiment that will have no real benefit" and you really don't know that these things have no benefit,

 

(for the million and ONEth time) I totally agree that I don't know. Point is, YOU don't know that they DO provide any benefit.

 

nor that they are impractical. For instance, how hard would it be to lower an LD block an inch in the chassis. I think I could get that done in fairly short order.,

 

You think YOU could get done in fairly short order. To a lot of people that task would be a major undertaking. But the LD28 block idea is offered up as if it's the only logical way to go. Then when fitment is brought up, we get "oh yeah, well ANYbody can put a cowl induction hood on, or cut the hood and use the Nissan hood vent thingie, no big deal" (paraphrasing here). Man, if I had built up an LD28 block based on the advice I've seen here, and then run into having to butcher the hood or use a different hood entirely, or lower the engine, I'd be fricking FURIOUS.

 

Correct me if I'm wrong, but if you shaved an N42 you wouldn't be able to run pump gas. Right? So in order to get a significant amount of quench out of the N42, you'd need to run race gas.

Norm is, I believe, at 11.2:1 with 2 Felpro head gaskets, and with 2mm filed off the top of his L28 pistons (done in situ!). I THINK that's his setup. Speakin' of which, how does THAT have "quench" (2 felpro gaskets = close to .100", tops of pistons approximately even with block deck)?

 

Anyway, I'm not really meaning to suggest anyone do this.

 

 

The other advantage to the P head that I haven't been able to verify is the height of the intake ports. We didn't even get into this yet, and I almost don't want to, but supposedly the intake ports are located higher on the P90 which makes for a longer short side radius. I'm sure I don't have to explain the benefits of that to you.

 

Ah more theoretical benefits! I can see why you *almost* didn't want to bring it up

 

I can understand how a LOT of things are SUPPOSED to be good for power, but until it's proven out... I mean, you can't just LOOK at a port shape and KNOW how it flows, hotrodding history is crammed with stories of overporting (even some STOCK heads). I'm sure there's flow-bench data out there for the different L6 heads, so we probably have that, but ultimately it's gotta be real world results whether those ports are better.

 

Theory is only ONE side of science. Theory without the support of experimental results remains, well, THEORY.

 

Just because a head LOOKS higher performance doesn't make it so.

 

That's the crux of my problem with people suggesting that the N42/N47 are detonation-prone crap and the P79/p90 are the ONLY way to go.

 

I KNOW I don't know, you don't realize that YOU don't know either. That's the fundamental difference between our positions.

 

The only valid way to develop and tune for performance is to QUANTIFY PERFORMANCE (engine dyno, chassis dyno, 1/4-mile runs, by whatever valid repeatable method), make a modification, QUANTIFY PERFORMANCE, modify, QUANTIFY, modify, QUANTIFY. That is SCIENCE. This will tell you what you're REALLY accomplishing. Saying "this should be better so it is better" is just conjecture, and shouldn't be presented as a demonstrated proven FACT.

[JMortensen]

Norm is, I believe, at 11.2:1 with 2 Felpro head gaskets, and with 2mm filed off the top of his L28 pistons (done in situ!). I THINK that's his setup. Speakin' of which, how does THAT have "quench" (2 felpro gaskets = close to .100", tops of pistons approximately even with block deck)?

 

I don't know much about Norm's setup. I certainly haven't paid as much attention to what he's doing as I have to what you've been doing. I ***thought*** he was running 280 rods and pistons on a stroker crank. That would leave you with a LOT of positive deck height, and I ***thought*** he had to mill down the pistons and run the 2mm gasket to get to the point where he would have quench. I could be wrong.

 

BOW DOWN BEFORE ME. BOW or receive my WRATH.

 

I'll take the wrath I suppose.

 

(for the million and ONEth time) I totally agree that I don't know. Point is, YOU don't know that they DO provide any benefit.

 

I don't know how you figure out what to do on your Z. Maybe you just ask someone who knows better than you do, and do exactly what they tell you. Nothing wrong with that other than you're limited by the person you're asking. It sounds to me like DAW has access to all kinds of L parts. When I built my current engine I could have used any block, any crank, any L24/L26/L28 rods, and any head except the Max N47. I chose what I chose because I listened to an "expert" and dumped a pile of money into an E31. If I had it to do over again, I wouldn't have anything like the build that I've got now, and I'm as sure as I can be without spending another $1500 to prove my point that I would be pumping out more hp.

 

Maybe I'm some kind of psychic or something, but I can see a head and a block and rods and crank and I can get an idea of what it's going to do BEFORE I actually build it. Similarly, when I go to the fridge I seem to "know" what I want to put on a sandwich, and when I make it: BLAMMO!!! Good sandwich!!! And I knew it was going to be good BEFORE I bit into it

 

But the LD28 block idea is offered up as if it's the only logical way to go.

 

I'll re-read the post in question, but I don't remember it being stated that emphatically. I recall it provided the LD block as a relatively easy way to get past the deck height limitation.

 

I KNOW I don't know, you don't realize that YOU don't know either. That's the fundamental difference between our positions.

 

You know that you don't know. That is true. But the part you don't say is that you write off anything that hasn't been on a dyno chart that YOU'VE seen. You also fail to note that you BROWBEAT anyone who tries to disagree with you.

 

On the other hand I can apply reasoning to the questions that I seek answers to. Unlike an engineer, I can speculate and USUALLY come out right. I know that other similar situations have borne out the benefits of quench and rod ratio, and that those things should translate on an L series being that it is a gasoline powered piston engine. Nissan made their only aftermarket L-series performance head (non-crossflow anyway) with quench in mind. I have the ability to relate that knowledge to my own build. But I had a good idea that the quench area was going to matter even before realizing that about the FIA head. How did I know this? You hit the nail on the head before. Because I understand the theory behind quench, I could tell just by looking at them. I thought the rod ratio thing might also play out. I had been given the advice to fit the longest rod I could into my engine when I built it by my engine builder, but due to financial constraints was unable to use anything other than the L28 rods. When I found out Devendorf used them, I felt that the point was "proven". Why would a nationally competitive racer use them if there wasn't anything to it? BTW, the book says nothing about him using an LD28 block. I think he used an L28 block and crank, 140mm rods and custom pistons. And I think that would be a badass setup despite the fact that I've never tried it and haven't seen his dyno chart. Did you see that Kameari chain tensioner setup? I had a hard on for that thing 5 seconds after seeing it the first time. I am SURE that it would make a dyno recognizable difference in power, even though I haven't tried it.

 

I'm not claiming omniscience. I'm claiming the ability to see a good idea somewhere else and apply it to what I'm doing. And so far I've been fairly successful with that. From the Gtech comparison I'm fairing pretty well with my budget build vs your high dollar build.

 

EDIT-- I upped my compression ratio even though I have never seen a dyno sheet with the same L series engine with dished then flat top pistons. I just "knew" it would work!

[JMortensen]

shouldn't be presented as a demonstrated proven FACT.

 

You know what you're right Dan. My theories about rod ratio and quench are just theories. There's a hell of a lot of support to back them up in general terms, but they can never be absolutely proven as fact in every possible circumstance.

 

Kinda like these theories: theory of evolution, gravitational theory, atomic theory, germ theory, quantum theory, etc. None of those are absolutely proven either. I never worry about gravity either. I always "know" it will be there for me.

[Dan Baldwin]

Nothing like those theories, which can be considered "proven" much more so than phead superiority. By observations and EXPERIMENTAL DATA.

 

Norm's setup is LD28 crank, L28 rods, L28 pistons shaved 2mm (putting 'em right back down at deck level), and 2 head gaskets. Or was that 2mm gasket (I don't think so, he'd NEVER spend that kinda money if he didn't absolutely have to!).

 

Bigger rod ratio has been shown in some cases to improve performance *slightly*. In OTHER cases, SHORTER r/s ratios have been shown to improve performance *slightly*. Such performance differences *could* be as much a function of how "happy" the cam is with the piston speed near bdc and tdc. IOW, it *could* be that a cam developed for a 1.6 r/s ratio doesn't work as well with a 1.8 r/s ratio and vice versa, and that might have as much to do with actual performance gain or loss.

 

There is FOR SURE reduced side load and associated piston thrust with greater r/s. Also reduced peak piston acceleration. There is improved angularity/leverage through max cylinder pressure with shorter r/s. 1.60 is definitely the LOW end of what's normally seen. Would I try 140mm rods if I could fit 'em in the L28? Sure. It's mainly the LD28 block I'm railing against there. From what I've read and my own calculations, I don't believe the difference between 1.60 and 1.80 to be huge, but sure, if I could practically do it I'd have used 140mm rods.

 

I'm an engineer (big surprise I know), and I too speculate and USUALLY come out right. But there's just WAY too much subtle invisible stuff going on with combustion chamber design to KNOW just by LOOKING. Looking at a Golf II and a 928, my intuition would tell me the 928 is more aerodynamic. But it's NOT.

 

Regarding the Kameari chain tensioner setup, I too had temporary wood. BUT having thought about it, I don't know if it's such a great idea. Consider that you ALWAYS see curved guides for chains. They prevent the chain from TWANGING like a GEEtahr string. I bet with the Kameari setup you have to apply a TON of tension to prevent serious TWANGAGE. Stock setup doesn't require much tension, as the chain pretty much can't move laterally due to the guide on one side. I'll stick with stock for now...

 

KEE-rist don't go on about how I'm spending $millions vs. your budget build. If I wanted to be an engine builder that's what I would be. Truth is, my setup isn't all that inherently high-dollar anyway, I've just paid proven qualified labor to do a lot of the work. Note: the headwork was done by a shop that has DEVELOPED L6 engines. As in build, dyno, tune, dyno, mod, dyno, tune, dyno, mod, dyno, etc.

 

Upping compression as much as possible before getting detonation is a known and well-proven power-builder. So is upping displacement. Upping r/s ratio to maximize performance is a DIFFERENT proposition. You won't get any indication you've gone too far, like with compression ratio. That said, I don't know if you CAN go too far within an L28 block, but I hope you see my point. If you could go with 280mm rods practically, do you think performance would improve? I think it would be reduced. Look at cylinder pressure vs crank angle, vs rod/crank throw angle.

 

ENOUGH, good night!

[JMortensen]

Norm's setup is LD28 crank, L28 rods, L28 pistons shaved 2mm (putting 'em right back down at deck level), and 2 head gaskets. Or was that 2mm gasket (I don't think so, he'd NEVER spend that kinda money if he didn't absolutely have to!).

 

OK, so the L28 has a positive deck height of .030mm. The LD28 crank has an increased stroke of 4mm. Norm cut his pistons down 2mm. He could be using 2 Failure Prone gaskets at 1mm each or 2 regular gaskets at 1.2mm each.. That means that he should be at .4mm clearance (.016") with the head, or the pistons should just touch the head. I had this wrong before. Please help me figure out if I've screwed it up a second time. Regardless, doesn't seem right...

 

It's mainly the LD28 block I'm railing against there. From what I've read and my own calculations, I don't believe the difference between 1.60 and 1.80 to be huge, but sure, if I could practically do it I'd have used 140mm rods.

 

So we actually agree... man if I ever meet you in person we gotta go for a beer and talk about the time we agreed.

 

KEE-rist don't go on about how I'm spending $millions vs. your budget build.

 

Come on man! If YOU'RE going to determine the parameters of what is acceptable proof, at least let me gloat over my ONE instance of "proving you possibly wrong" or at least "less right".

 

Upping compression as much as possible before getting detonation is a known and well-proven power-builder. So is upping displacement. Upping r/s ratio to maximize performance is a DIFFERENT proposition. You won't get any indication you've gone too far, like with compression ratio. That said, I don't know if you CAN go too far within an L28 block, but I hope you see my point. If you could go with 280mm rods practically, do you think performance would improve? I think it would be reduced. Look at cylinder pressure vs crank angle, vs rod/crank throw angle.

 

The original r/s ratio of the 240 was 1.8. An L28 with 140mm rods = 1.77. Clearly not going beyond the original very successful design. Compression is a known and well proven power-builder in JUST THE SAME WAY that quench is. That's my only point. It's used pretty much universally in pretty much all heads on gasoline engines that I've seen.

 

Don't let the bed bugs bite...

[Dan Baldwin]

The stroker crank increases popup only 2mm, HALF of 4mm. So if the pistons are shaved 2mm, that puts you right back at stock piston height at TDC.

 

Oh yeah, since Norm uses L28 rods, not L24 rods, his r/s is 1.57, even "worse" than mine. Maybe I take that back about trying the 140mm rods if they fit the L28 block...

Ah, I might or might not, it remains something I'm not terribly concerned about. Like with the head, I'd just use what was available, what could be most easily put together.

 

Compression ratio isn't the same type of property as quench, compression ratio can be CALCULATED. Total cylinder volume at BDC divided by volume at TDC. You have a NUMBER, a quantity that can be compared. I think that "quench" is a more illusive property, it's not like you can absolutely quantify it.

 

I'm also wondering, how hard would it be to get a P90 head L28 or L31 to 11:1 CR? I'm thinking you might have to use custom pistons with reliefs for valve clearance and popups that protrude up into the chamber shape to get there. Which might explain why I never hear of any particularly high-compression P90 engines, I don't think pistons like that for the L-series are exactly readily available. Also, there's got to be a point of diminishing returns, as such a convoluted combustion chamber shape would begin to work against maximizing compression ratio.

 

Just pondering...

[JMortensen]

The stroker crank increases popup only 2mm, HALF of 4mm. So if the pistons are shaved 2mm, that puts you right back at stock piston height at TDC.

 

Thanks, I knew I had that wrong.

 

I'm also wondering, how hard would it be to get a P90 head L28 or L31 to 11:1 CR? I'm thinking you might have to use custom pistons with reliefs for valve clearance and popups that protrude up into the chamber shape to get there. Which might explain why I never hear of any particularly high-compression P90 engines, I don't think pistons like that for the L-series are exactly readily available. Also, there's got to be a point of diminishing returns, as such a convoluted combustion chamber shape would begin to work against maximizing compression ratio.

 

How do you think these 14:1 guys do it? They don't just mill 1/4" off the head you know. Every forged piston that I've seen for an L series was forged with big pop ups for 12:1 or better compression (actually I think they were all ~14:1) and all of them REQUIRED that the piston be machined. I'm sure that is how John Coffey got his quench area. Just machine the piston to match the combustion chamber. Granted, every forged piston I've seen was for a high compression NA L series motor, and I haven't seen that many (only 2 different race engines). I'm sure you can get flat tops or dished pistons too, but it is definitely not unusual or hard to come by domed pistons that are meant to be machined.

 

I think that "quench" is a more illusive property, it's not like you can absolutely quantify it.

 

Maybe you can't easily quantify it or maybe we're just ignorant of the Q scale or something, but it's easy to find engine builders of all types of gas engines using it to their advantage, and they can tell you why it is advantageous.

 

Also, there's got to be a point of diminishing returns, as such a convoluted combustion chamber shape would begin to work against maximizing compression ratio.

 

Actually they use the piston shape to their advantage. Some really funky piston and chamber shapes come out of this. Check out some of the full billet Harley heads. Crazy computer generated CNC milled chambers and pistons designed to optimize the suction on the intake, burn, and the exhaust efficiency.

[Dan Baldwin]

I'm also wondering' date=' how hard would it be to get a P90 head L28 or L31 to 11:1 CR? [/quote']

 

How do you think these 14:1 guys do it? They don't just mill 1/4" off the head you know. Every forged piston that I've seen for an L series was forged with big pop ups for 12:1 or better compression

 

I was thinking more of how you'd get a P90 headed street/track motor with stock pistons up to 11:1. Could be a problem to get more than 10:1 with flat pistons? That might explain why I never hear of them.

[JMortensen]

Well according to http://geocities.com/zgarage2001/head.html the volume of the P79 chamber after the shave is 46cc. The volume of an N42 chamber is 44.6 (Lengine.exe). I would think that you could get damn near the same compression out of either one.

 

Also, the valves in the P90 are .100 shorter (from How to Mod). So you could theoretically mill the P90 .100 instead of .080, and get a little more that way and still be right where you need to be with the rocker geometry.