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Carburated power


AFCrain

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Power comes from an ideal mixture being ignited at the correct time. What the mixture comes from, or what ignites the mixture is irrelevant. The stock SU carbs are not a limiting factor to power that can be had out of a mostly stock engine. I say pay attention to the small things, check your distributor is in perfect mechanical order, set to the ideal timing for your engine. Then sync and adjust the carbs. It's virtually free.

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oh, and to rebut the WEB comments:

My engine started as a 225,000 mile engine from a 1980 280ZX 2+2 which was never molested.

I do not have the book he talks about, I started on SU's in 1979 when I had to learn the hard way about tuning SU's on a single draw-through Corvair Crown Turbo Setup sitting backwards in the seat watching needle positions and listening for detonation with a piece of surgical rubber duct taped along the back of the car to the seat where I was sitting.

 

That he's offended by my statement that 147 is 'middle of the pack'---well can't help that. In decades of watching L20A, L24, L26, and L28's run on the dyno, depending on what engine it would be, that is about right. It's sad that 'estimates' are fostered...that's not good. It dynos what it dynos...if you modified it further, dyno it again, and report the results don't 'estimate'---at least that's the way I do it. You're only as good as your last dyno run. "Estimates" are for benchracers and are useless as an example or comparison point. That he states that he got the results for only the cost of the book was exactly my point---why he chose to be offended rather than see we were agreeing on the point that you don't have to CHANGE ANYTHING to gain considerable horsepower is beyond me, perhaps he wanted to be offended. Don't know, don't care. Personally I feel it's a little sad that we agreed and he's pissed off about it and goes into the puffery he did (don't know me, don't know what I done, etc :rolleyes: oh brother! Whatever...)

 

Norm the 12 Second SU Dude has no 'estimates' other than conversions of his 1/4 mile times. Devoid of dynos or timeslips, any estimation of gain is useless. The Butt Dyno is a notoriously imprecise instrument!

 

In the end incremental gains documented by verifiable empirical methodologies is what you are after, not some nebulous "Butt Dyno Measurement." Know where you currently are: if you have an L26 and aren't making at LEAST 120-30 to the rear wheels you are down on power from where you should be with a stock system properly tuned. Same for an L28 at 140-50. That WEB got 145 from an L24, that's a good number, never said it wasn't. It's about where it should be for a tuned engine. (What does WEB think of the guy with a freshly built 'performance' L24 that he just paid $5000 for with triple 40DCOE's and that spins 124HP on the same dyno he is running on at 147???? I posit that he has THE EXACT SAME THOUGHT AS ME WHEN HE SEES IT! And yes, this is ANOTHER example from my archives...)

 

But if you are running 100HP on an L28---or even an L26 consider STRONGLY the possibility that you have some T's to cross, and some I's to dot BEFORE you go spending money on 'another magic bullet' to up your horsepower.

 

And that was the point all along!

Edited by Tony D
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Power comes from an ideal mixture being ignited at the correct time. What the mixture comes from, or what ignites the mixture is irrelevant. The stock SU carbs are not a limiting factor to power that can be had out of a mostly stock engine. I say pay attention to the small things, check your distributor is in perfect mechanical order, set to the ideal timing for your engine. Then sync and adjust the carbs. It's virtually free.

 

 

Agreed! Now we have THREE people weighed in on the thread saying the exact same thing. Don't hate me, just see what is being said!

 

"Free" has ALWAYS had the most 'bang for the buck'!!! :P

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Power comes from an ideal mixture being ignited at the correct time. What the mixture comes from, or what ignites the mixture is irrelevant.

 

This is not true and severely downplays many other factors in engine performance. Power is directly related to volumetric efficiency. Even if the mixture is "ideal" and is ignited at MBT timing, you will be down on power compared to a cylinder that is filled more. Cylinder filling is heavily dependent on intake (and exhaust) tract design, meaning that "what (where?) the mixture comes from" is very much relevant.

 

The reason I said that I'll take a good set of triples over any other carb setup is because of the increase in volumetric efficiency and mixture uniformity inherent in the triples. Hence, Tony mentions that properly tuned, triples will make more power.

 

However, with the mention of the "best bang for the buck," obviously a proper tune is number one.

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Agreed! Now we have THREE people weighed in on the thread saying the exact same thing. Don't hate me, just see what is being said!

 

"Free" has ALWAYS had the most 'bang for the buck'!!!

 

I have never once negated the fact that competent tuning was going to be a step one guarantee. I also see that my "best bang for the buck" comment is still being taken out of context. I completely understand what you are saying, Tony. As much as it makes wince to say it, you are and have been correct throughout this post, although a few things written have raised my eyebrow, you still are correct.

 

But even after all that is said and done, it is the personal experience that I am asking about. TB injection on a 4bbl intake, blow through turbo/holly or simply tuning the SU's that are on there. I'm asking about personal experiences from people who have done these modifications. OR in your case where the PO of your prior vehicle thought that throwing a pair of fuzzy dice on the mirror would knock a second off it's track time, but you realized that the engine was obviously lacking and decided to go back to it's stock form. Kudos to your brain!

 

I am not and never have been looking for a magic bullet, just different possibilities if tuning alone doesn't make me happy with the engine's performance. Let me add another before you look too far into it. I realize that other upgrades, modifications and work will have to be done for an engine to properly perform if it is given a magic bullet make over.

 

Thank you to those who have shared!

 

@Leon~ What type of head work have you done and what kinds of gains have you seen using triples?

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No head work or cam change of any kind. All I did was swap out old, worn SUs for 40DCOE triples that I had. Of course it pulls a hell of a lot better! I don't have dyno results but I will post video comparing the SUs to the triples just for kicks. I did get to drive it before it was put in the garage for a suspension rebuild and not only did they pull well, but the sound was amazing! I plan to dyno test in the future.

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I've been leaning towards the the triple 40s as well, but I know a guy with a set of dual webbers that he's looking to get rid of. They'd need an obvious rebuild, but he's practically throwing them at me. What engine are do you have?

 

Otherwise stock L24 with E88 head and less restrictive exhaust.

 

EDIT:

 

Weber DGV duals aren't worth the trouble. Either stay with round tops or go to triples.

Edited by Leon
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No head work or cam change of any kind. All I did was swap out old, worn SUs for 40DCOE triples that I had. Of course it pulls a hell of a lot better! I don't have dyno results but I will post video comparing the SUs to the triples just for kicks. ... I plan to dyno test in the future.

 

I'll add that everyone who was in my car when the triples were on it (INCLUDING MYSELF) thought it made a LOT more power, and pulled hard as hell. FAR harder than after I put the EFI back on---until I went back to the dyno and was frankly SHOCKED at the difference.

 

The car was so smooth and quiet, it was making an honest 70hp more than when the 40's were on it.

 

As I said, estimates are useless, and the Butt-Dyno is a notoriously innacurate meter to gauge anything. At the minimum acceleration tests over a set distance (say 1st and 2nd gear WOT pulls even...after mods/tuning a decrease in time means 'net gain' an increase in time means 'net loss'.)

 

Until I experienced it for myself, firsthand, I would have NEVER thought those triples were making LESS power than what I retrofitted. Never, never, ever! It just did not FEEL faster after the mods. But the 1/4 mile times, and dyno (along with G-Tech actually) convinced me otherwise.

 

Beware the Butt Dyno!

 

 

I've done all of them, and apparently the scope of what was originally asked has changed along the way. If you are now considering 'blow through' why not 'blow through triples'---233 when tuned properly, double what you likely have in there now. But a PITA to set up and unless you get the stuff cheap... :rolleyes:

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Well I've been at work all day and it seems I have missed a lot of dialogue. Tony D you are not the Amazing Kreskin you must be Carnack The Magnificent, you have to be because again you claim to know my state of mind by simply reading some little black letters on a white background. Let's all give him a big hand. Lets see( according to you) I'm offended, pissed,and went off in a puffery, wow! a puffery! the simple truth is when I am posting a reply you can't possibly know if I am laughing my ass off, bored to tears, grinding my teeth to nubs, or boxing baby brother with the left hand. It's true you don't know me.... simply a statement of fact, We have never met.... another factual statement, you don't know me or my vehicle at all.... what's to be offended about? Oh yea it's because you stated my H.P. was middle of the pack, wrong again. The #s were used to make a point ( you know a before and after comparison) they could be half that big deal,it still makes the same point. As I said before so be it, it is what it is. I've been reading your posts since I joined the board and agree with 99.9999% of them! But you know what...I never thought it to be unfortunate... as you do, seems you are the one offended. Tuning a car should be a given,any car guy will know that, even a young man that likes to work on the race car with dear ole dad. What I find odd is for someone to make a statement that bolt ons don't work.... you did make that statement i saw it , it was those little black letters on that white background, what about a cold air kit? oops bolt on , doesn't work, maybe a free flowing exhaust sys. oops bolt on doesn't work, ok how about a cool can oops bolt on , doesn't work, lets try triples oops bolt on , doesn't work, I got it... a high lift cam oops bolt on/in ,doesn't work.If they did not work everyone would be in completely stock cars. Who was it that posted that your not going to get any gains with S.U.s on a stock motor. I beg to differ,please re-read my post. Tony D maybe you can comment on this observation... even with the air flow improvements my A.F.R. goes 10.8-11.2 at full throttle? Can it be that they are still restricting my stock motor. I,ll bet that it is,and to your point it needs to be tuned, but it wasn't ,still got my 20-25 % Which means i;m leaving some H.P. on the table, not much but some. stock S.U.s are very restrictive but one CAN get good improvements with them with a little elbow grease.

We can debate the meaning of tuning, personally I don't consider physical grinding/ sanding on S. U.s tuning,or at least that would not come to mind when I hear the word tune. I am sure some do and some don't. Maybe his first post should have been worded better,however since then he has tried to enlighten us on what he meant the post to say, it evolves,restates,corrects,and dare I say it ....it fine tunes.

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I'll respectfully disagree on the but dyno. My but is just fine. It tells me when it's running a little off, i don't know about anyone else but I am quite tuned ( there's that word again) to my Z. Surely I'm not the only one who really drives their car, gets to know its quirks & habits, can feel when it's HONKin, ( thats for any of the older guys) it's one of the main things that tells us something is not quite right. Actually I would be amazed if a car guy that has owned his ride for a good while couldn't tell! Now I'm not going to pretend to be able to tell someone down to the exact H.P. what it is or is not doing. If I could I'm in the wrong business. Maybe Tony D doesn't drive his Z enough. It's not a knock on Tony D.... maybe he has an insensitive ass. Good golly did I just really say that! I'm sorry Tony D that was immature of me, but damn! I just could not resist,

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AFCrain, if you are still considering tyring the S.U.s and buying the book (I got the best deal with Amazon) send me a P.M. and I'll go over with you what I experienced. You already have a good start with the 260 intake if it's the original. Even if you decide not to that book has very good info on all aspects of performance.

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In the process of building my L28-et I plan on slapping on a new carb setup on my L26. I'm not going to go into details about the L28 by I'm looking for input on power gains on carburated L series. Any input on the different setups is welcome, eg: SU's, triple webers, 4 barrel conversions, etc. I'm looking for the biggest bang for my buck while I wait for the real power!! Also, please don't try to dissuade me from doing this. I don't care about the extra costs or how pointless it may be. I simply enjoy working on my car, plus if the L28 blows up down the road this could be a good back up. Thanks in advance for reading and commenting!

 

The original poster is talking about a stockish L26.

 

 

 

The stock SU carbs are not a limiting factor to power that can be had out of a mostly stock engine.

 

My comments are within the context of what the original poster was asking for.

 

This is not true and severely downplays many other factors in engine performance. Power is directly related to volumetric efficiency.

 

Even if the mixture is "ideal" and is ignited at MBT timing, you will be down on power compared to a cylinder that is filled more. Cylinder filling is heavily dependent on intake (and exhaust) tract design, meaning that "what (where?) the mixture comes from" is very much relevant.The reason I said that I'll take a good set of triples over any other carb setup is because of the increase in volumetric efficiency and mixture uniformity inherent in the triples. Hence, Tony mentions that properly tuned, triples will make more power. However, with the mention of the "best bang for the buck," obviously a proper tune is number one.

 

 

You are not going to gain ANY volumetric efficiency by "upgrading" a non limiting factor. Change the cam / cam timing, cylinder head, or exhaust and my comments no longer apply. Yes there are improvements to be had on the Stock SU's, but now we are talking about tuning, not bolt ons. Same rule applies to webers.

 

I like my triples (DCOE 40-18's), they make lots of noise, and run well. I also like the stock SU's. My emotional attachment to a piece of hardware does not change my answer to the original poster as how to best benefit him. For what it's worth, I can't tell the difference between the two on the butt dyno, except: The triples are more responsive at tip in, and make more noise. Initial tip in throttle response has nothing to do with WOT power.

 

I hope that clarifies things.

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"seems you are the one offended."

 

Please, don't transfer your hangups and emotions onto me. I don't know where you get the idea that I'm 'offended', and frankly this is getting old. Your style of 'little printed words' does tell a lot more about you than you think.

 

In THAT respect, yes, perhaps I am Kreskin or Carnak.

 

He's going to what he's going to do. It's sad people get so hung up on being offended that they can't see common ground. At this site, it's especially sad. Perhaps a harbinger of things to come, but I most certainly hope not.

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You are not going to gain ANY volumetric efficiency by "upgrading" a non limiting factor. Change the cam / cam timing, cylinder head, or exhaust and my comments no longer apply. Yes there are improvements to be had on the Stock SU's, but now we are talking about tuning, not bolt ons. Same rule applies to webers.

 

Incorrect. I don't know what you mean by "non limiting factor." Every change in the system will have its effect, no matter how much of an effect it is. Of course you will gain more if you match a cam and an exhaust to your intake, but simply changing the intake will still have a very noticeable effect.

 

Volumetric efficiency will be affected any time the intake is altered geometrically. Using triples compared to other carbs, resonance effects will be stronger with the individual runners and there will be much less restriction, especially when comparing venturi sections with SUs. Therefore, there will be a considerable gain in volumetric efficiency when going to triples. In no way will VE not be affected by a complete change of the induction system.

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Back in the late 80s, Dan Bisone lapped the field in a Improved touring race in his 240z.

 

Pretty sure it passed tech. that time and a rumor was about that it turned 190hp to the wheels.

 

Do you know what he was running? Is there a thread on here about him or a link that could be posted?

 

I like my triples (DCOE 40-18's), they make lots of noise, and run well. I also like the stock SU's. My emotional attachment to a piece of hardware does not change my answer to the original poster as how to best benefit him. For what it's worth, I can't tell the difference between the two on the butt dyno, except: The triples are more responsive at tip in, and make more noise. Initial tip in throttle response has nothing to do with WOT power.

 

Thank you! Even though it wasn't full of tech gibberish(which I do understand...somewhat) I appreciate an honest answer. You shared what you enjoy and gave a reason for it! Even if you couldn't tell much of a difference you still enjoy the triples. I know others have said what they have or would suggest but that's an honest experience.

 

AFCrain, if you are still considering tyring the S.U.s and buying the book (I got the best deal with Amazon) send me a P.M. and I'll go over with you what I experienced. You already have a good start with the 260 intake if it's the original. Even if you decide not to that book has very good info on all aspects of performance.

 

I still haven't entirely decided. I looked into that book and even though it clearly isn't meant for and L series, it also doesn't seem like it carries a lot of info. But thenagain, never judge a book by it's cover. I just bought a slew of books directly related to the Z car. How to Restore Your Datsun Z-Car , How to Rebuild Your Nissan/Datsun OHC Engine: Covers L-Series Engines 4-Cylinder 1968-1978, 6-Cylinder 1970-1984 and How to Modify Your Nissan/Datsun OHC Engine. They came highly recommended so I hope they'll be good. I'm not sure how I missed those up to this point, books are usually the first place I go.

 

I've done all of them, and apparently the scope of what was originally asked has changed along the way. If you are now considering 'blow through' why not 'blow through triples'---233 when tuned properly, double what you likely have in there now. But a PITA to set up and unless you get the stuff cheap...

 

The scope has never changed, I just didn't word it as well as I could've. I'm still open to all options and doing research on the side, but this thread has given me a bit more insight into the personalities of these little cars. While not completely full of usefull information, triples seem to be a crowd favorite, properly tuned SU's are underestimated to the average joe and either route I go down, an aftermarket cam will be quite complimentary to the carbs(as if that wasn't already known). I'll definitly have to look into the blow through triples. Unless it's too much of a PITA... this is still just a goof around motor until I get an L-28 built.

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Well i mounted Yetterbens Tripple carb blow through set up to my dads cars ( 83 280zx with euro L28ET and T04)

 

They are stock 40 MM webbers that could have used a rebuilt i guess.

The problem is finding the HKS surge tank. It is easy(er) in Japan, you want to saty away from cartech systems.. A long story short ... they @#$ compared to the HKS system in a way i cant describe here ;)

Apart from that id say it doesnt add much complexity to the build.

 

Only thing that i find to be a pita is when synchronising them as you need to have to remove the bolted tank and it uses a gazillion m6's bolts.

and you need a wideband to see what is happing, frankly as with tripples a dyno sessions is the best way to go!

 

You need to take into account that you if you go blow through, you are best to stay away from webbers as over 13PSI the brass floats collaps, a Mikuni or Dellorto doesnt have this problem as it has composite floats. so i would go for a set of those.

Also you need a short runner (Mikuni FET) intake as i.e. the cannon manifold for tripples with the tank on might hit your brake booster etc.

 

And if you want bang for the buck .. Yetterben ( search his post) made over 350 RWHP on a NA junkyard l28 with these and a cheap Ebay turbo slapped on!! All for arround US 600 if memory serves me right.

My dad makes 231 to the wheels at ~7,5 PSI but tuning is still off so that might get a few HP higher.

 

So what am i saying here ;) GO FOR IT .. it is so retro cool!! haha

Edited by frank280zx
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