Some quick thoughts on engines and FI
07-26-2006, 07:46 AM
#1
Some quick thoughts on engines and FI
I have been looking at the big money being spent on engines for the FI community, at the same time I have been reading Maximum Boost by Corky Bell. My thoughts are based on a "street" car, daily driver type, not a dyno monster, drag racer, or track car. A higher than stock performance Z designed to be reliable using FI, performing well for, again, street use. I am looking at my options for the future as far as engine goes, and where I want to put my money. If I wanted a drag car, I think it would be much cheaper to sell the Z and buy a car that was more suited for that purpose, with cheaper and more abundant parts toward that goal. I really am looking for the best overall performance I can get from the VQ without spending some crazy amount of money on the engine, ending up with a slower than stock engine when not boosting, with huge injectors that don't idle right, etc.
Anyway, here are some things I have read, and my comments.
Mr. Bell first refers to compression ratio. He states a good stock engine should be able to handle 5 psi of boost. True in my experience.
Compression ratio should be determined by boost pressure desired and intercooler efficiency (based on using pump gas).
His rule: a turbo engine should never be reduced to a low compression slug.
This makes sense to me. I do not boost every time I hit the throttle. All things being equal, if I lower the compression and do not change other factors (cams, etc,) I will actually have a poorer performing engine when not boosting (less power, throttle responce, fuel eff. etc).
Preparing the cylinder head: Mr. Bell states that a good street turbo engine is quite comfortable with stock heads. Racing of course is another matter.
He seems to recommend that ensuring a quality head without imperfections is the best prep for street turbos.
He talks alot about pistons, but gives this bottom line: Unless circumstances are highly unusual, street cars with stock redlines will prove more sucessful with cast pistons. In particular, he refers to the higher tolerances (piston to cyl wall) required for forged pistons, and how damage during warm up more or less equals the damage seen in overloaded cast pistons. He did give the caveat that some good designed forged pistons have solved the clearance problem, and the key is knowing what you have. I see this as an excellent point - where do we stand in pistons avail for the VQ? Is clearance a problem? Which pistons have this problem, which don't?
His rule: Do not rush to the forged piston store every time a turbo engine needs preparation.
He says balance the engine, or you are not serious. Makes sense to me.
Camshafts: Turbo cams are different than atmo cams.
His rule: it is hard to find a turbo cam that works better than a stock cam.
Makes sense to me again. NISMO cams designed for atmo engine would not have the caracteristics desired in a turbo cam, correct me if I am wrong.
As far as bearings, con rods, he states this should be based on RPMs, if you keep the RPMs within stock range, the stock items are fine. But earlier in the chapter he stated that research on the engine will show any known weaknesses. I think I am safe here in saying that the VQ con rods and ring lands on the pistons are cause for concern with us FI guys. My gut feeling is that money spent on stronger than stock rods, and a piston that has ring lands thicker than stock, will serve the street turbo well without too much cash expended. Your expert thoughts on this please.
He sums the chapter up with ideal compression ratio:
No such thing.
Lower compression: higher boost with no detonation (the engine killer)
Higher compression: greater fuel eff. and non-boosted response (harder to supress detonation).
He states for all practical purposes, use the stock compression ratio - serious intercooling makes this possible. Makes sense to me again.
Head gaskets: Mr. Bell states that special head gaskets and O-rings are often cures to the wrong problem - poor excuses for not dealing properly with detonation. If detonation is the problem, cure it, and a stock head gasket will usually perform well. Again, makes sense to me.
Water injection: He basically calls it a big no-no. Now, he does not refer to water-methanol injection, but water injection, so I do not know if he is refering to both here. Again, he says it is a poor excuse band aid for not doing the job right. Help me here: does he mean water-methanol, or just water? I have been looking at this for a "safety factor", but I just wonder if he is not right - if you don't have detonation, you don't need this. Again, is water-meth inject just a cure for a bad tune???
What brought me to this is that when I hear of blown engines on a FI car, too often I also hear the extreme - some massive overkill engine build at literally 5 times the cost of a stock engine. Isn't there a middle ground for engine building here, that provides all the benefits of the stock engine compression ratio with some safety factor? In most cases, the engine isn't blown because the stock engine is a POS, it's blown because of bad tune (or engine management momentary failure), other modifications that the kit wasn't tuned for, etc. Paying $10K to make the engine handle a bad tune seems crazy to me. Why not fix the source of the problem? Again, I am not refering to those who are going for the maximum hp goals, etc, but the daily driver FI guy.
I like stock idle rpm, I like stock throttle responce when not boosting, I can't get proper traction at 9 psi so I really don't have a need for more boost or rwhp for that matter. Is anyone rebuilding VQs that make sense for a street car, based on these principles I have vomited here? The experts and professionals are more than welcome to comment on these thoughts, and point out the "wrong" or confirm the "right."
Anyway, here are some things I have read, and my comments.
Mr. Bell first refers to compression ratio. He states a good stock engine should be able to handle 5 psi of boost. True in my experience.
Compression ratio should be determined by boost pressure desired and intercooler efficiency (based on using pump gas).
His rule: a turbo engine should never be reduced to a low compression slug.
This makes sense to me. I do not boost every time I hit the throttle. All things being equal, if I lower the compression and do not change other factors (cams, etc,) I will actually have a poorer performing engine when not boosting (less power, throttle responce, fuel eff. etc).
Preparing the cylinder head: Mr. Bell states that a good street turbo engine is quite comfortable with stock heads. Racing of course is another matter.
He seems to recommend that ensuring a quality head without imperfections is the best prep for street turbos.
He talks alot about pistons, but gives this bottom line: Unless circumstances are highly unusual, street cars with stock redlines will prove more sucessful with cast pistons. In particular, he refers to the higher tolerances (piston to cyl wall) required for forged pistons, and how damage during warm up more or less equals the damage seen in overloaded cast pistons. He did give the caveat that some good designed forged pistons have solved the clearance problem, and the key is knowing what you have. I see this as an excellent point - where do we stand in pistons avail for the VQ? Is clearance a problem? Which pistons have this problem, which don't?
His rule: Do not rush to the forged piston store every time a turbo engine needs preparation.
He says balance the engine, or you are not serious. Makes sense to me.
Camshafts: Turbo cams are different than atmo cams.
His rule: it is hard to find a turbo cam that works better than a stock cam.
Makes sense to me again. NISMO cams designed for atmo engine would not have the caracteristics desired in a turbo cam, correct me if I am wrong.
As far as bearings, con rods, he states this should be based on RPMs, if you keep the RPMs within stock range, the stock items are fine. But earlier in the chapter he stated that research on the engine will show any known weaknesses. I think I am safe here in saying that the VQ con rods and ring lands on the pistons are cause for concern with us FI guys. My gut feeling is that money spent on stronger than stock rods, and a piston that has ring lands thicker than stock, will serve the street turbo well without too much cash expended. Your expert thoughts on this please.
He sums the chapter up with ideal compression ratio:
No such thing.
Lower compression: higher boost with no detonation (the engine killer)
Higher compression: greater fuel eff. and non-boosted response (harder to supress detonation).
He states for all practical purposes, use the stock compression ratio - serious intercooling makes this possible. Makes sense to me again.
Head gaskets: Mr. Bell states that special head gaskets and O-rings are often cures to the wrong problem - poor excuses for not dealing properly with detonation. If detonation is the problem, cure it, and a stock head gasket will usually perform well. Again, makes sense to me.
Water injection: He basically calls it a big no-no. Now, he does not refer to water-methanol injection, but water injection, so I do not know if he is refering to both here. Again, he says it is a poor excuse band aid for not doing the job right. Help me here: does he mean water-methanol, or just water? I have been looking at this for a "safety factor", but I just wonder if he is not right - if you don't have detonation, you don't need this. Again, is water-meth inject just a cure for a bad tune???
What brought me to this is that when I hear of blown engines on a FI car, too often I also hear the extreme - some massive overkill engine build at literally 5 times the cost of a stock engine. Isn't there a middle ground for engine building here, that provides all the benefits of the stock engine compression ratio with some safety factor? In most cases, the engine isn't blown because the stock engine is a POS, it's blown because of bad tune (or engine management momentary failure), other modifications that the kit wasn't tuned for, etc. Paying $10K to make the engine handle a bad tune seems crazy to me. Why not fix the source of the problem? Again, I am not refering to those who are going for the maximum hp goals, etc, but the daily driver FI guy.
I like stock idle rpm, I like stock throttle responce when not boosting, I can't get proper traction at 9 psi so I really don't have a need for more boost or rwhp for that matter. Is anyone rebuilding VQs that make sense for a street car, based on these principles I have vomited here? The experts and professionals are more than welcome to comment on these thoughts, and point out the "wrong" or confirm the "right."
07-26-2006, 09:01 AM
#4
If your going to spend the $$$ on labor for upgrading internals, you should do forged-not cast pistons. I have this book and while VERY informative its now a little out of date. I doubt you'd find 1 person on here that would tear down a motor and throw a cast piston in with a larger ringland-as far as I know nobody makes lower compression cast pistons.
To answer your Q regarding building a motor that isnt out of this world-yes you can build a motor and not go crazy. You can do a basic piston of your desired compression, and Eagle rods. That will be enough for roughly 600whp. Not many people really need Araias ED pistons or $1200 Pauter rods, but the thought here is "why not go all the way so I dont have to pull my motor apart again later?" I agree with this, but Ill never down an Eagle rod-like others do. For your goals, you can do a very basic short block and be more than fine with stock cams and more boost. Around $3000 for a basic short block. The big part of your build would be the labor and tuning of your new set-up, which will cost more than your block.
To answer your Q regarding building a motor that isnt out of this world-yes you can build a motor and not go crazy. You can do a basic piston of your desired compression, and Eagle rods. That will be enough for roughly 600whp. Not many people really need Araias ED pistons or $1200 Pauter rods, but the thought here is "why not go all the way so I dont have to pull my motor apart again later?" I agree with this, but Ill never down an Eagle rod-like others do. For your goals, you can do a very basic short block and be more than fine with stock cams and more boost. Around $3000 for a basic short block. The big part of your build would be the labor and tuning of your new set-up, which will cost more than your block.
07-26-2006, 10:00 AM
#5
Originally Posted by Alberto
If your going to spend the $$$ on labor for upgrading internals, you should do forged-not cast pistons. I have this book and while VERY informative its now a little out of date.
Slightly lower compression or the same as stock.
(This is to meet my goal of the same engine response when not boosting as the stock non boosting Z)
Up to double size ringlands. (Safety)
No piston to wall clearance problems that cause excessive wear. (Same or better durability as compared to cast pistons)
Good price.
Originally Posted by Alberto
I doubt you'd find 1 person on here that would tear down a motor and throw a cast piston in with a larger ringland-as far as I know nobody makes lower compression cast pistons.
In other words, not really looking for lower compression - kind of my point.
Originally Posted by Alberto
To answer your Q regarding building a motor that isnt out of this world-yes you can build a motor and not go crazy. You can do a basic piston of your desired compression, and Eagle rods. That will be enough for roughly 600whp. Not many people really need Araias ED pistons or $1200 Pauter rods, but the thought here is "why not go all the way so I dont have to pull my motor apart again later?"
Originally Posted by Alberto
I agree with this, but Ill never down an Eagle rod-like others do. For your goals, you can do a very basic short block and be more than fine with stock cams and more boost. Around $3000 for a basic short block. The big part of your build would be the labor and tuning of your new set-up, which will cost more than your block.
Those who have TT with lower compression pistons 8.6:1 - what is the response like? Do you like the responsivness of the engine when you are not boosting? Or am I making an issue where there is none. Seems to me that we are trading compression for more boost - where is the advantage? Lower compression, less detonation, lower performance, need for more boost, higher boost, more risk of detonation. Chasing the tail? Or am I just missing something here?
Thanks for the input.
07-26-2006, 10:12 AM
#6
Originally Posted by gringott
But at the goals I specified, granting a good tune, isn't the extra money on these parts just safety for a BAD tune? If you are not detonating, you don't need the overkill. These few bucks here and there add up to $10,000 engines. Fine for a race car, but a little high for a DD IMO.
07-26-2006, 10:23 AM
#7
Alberto: only you can say, but I would guess that multipule drag strip runs trying to wring the best times possible etc might indicate that you put a little more stress on the engine than many others might. It is very possible to blow a stock VQ by beating the crap out of it on the strip and off. No offense to you. Again, I am talking about a DD boosted vehicle, not a car taken to the track once a week or driven all out all the time.
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07-26-2006, 10:34 AM
#8
No offense taken
FWIW-I only ran the set-up boosted on 2 seperate days, and the car was only driven on weekends, and was not always beat up. Im a little lost now, are you looking for opinions on a motor build to suit your needs (fairl conservative) or you just wanted thoughts on what CB said?
FWIW-I only ran the set-up boosted on 2 seperate days, and the car was only driven on weekends, and was not always beat up. Im a little lost now, are you looking for opinions on a motor build to suit your needs (fairl conservative) or you just wanted thoughts on what CB said?
07-26-2006, 10:53 AM
#9
Both - I have been thinking about this for some time, and reading his book confirmed some things I thought - and added more questions. I also think that we, the daily drivers, are distracted sometimes by those who are going for the maximum all out performance. Just my opinion - I can't see sinking over $10 into an engine build alone for my car. It just would not happen, and what I am asking here - overall, isn't the best DD overall performance per dollar spent keeping the stock or close compression ratios and realistic hp requirements? Again, I see the tail chasing - lower compes, need better fuel, need cams, need head porting, need this need that. All with diminishing returns and performance gains. In fact, if I did throw a rod right now, today, I would most likely just throw in another long block - slightly used or new. Cheaper in the long run, but a bit of a gamble, as in what happened to you. There is no way to know how strong unless you build, and even that is no guarantee.
And I am also thowing oot what Mr. Bell said - for input and updating, esp. about the water injection. He seems to like it not at all.
And I am also thowing oot what Mr. Bell said - for input and updating, esp. about the water injection. He seems to like it not at all.
07-26-2006, 11:37 AM
#10
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If I was building the motor for a DD, I'd get Eagle rods, Arias pistons and ARP hardware, and call it a day... should be fine for 500whp, which seems more than enough to spin the tires on the street.
07-26-2006, 12:30 PM
#11
Originally Posted by JeffesonM
If I was building the motor for a DD, I'd get Eagle rods, Arias pistons and ARP hardware, and call it a day... should be fine for 500whp, which seems more than enough to spin the tires on the street.
That is the conclusion I am reaching. Most cost effective.
07-27-2006, 08:16 AM
#12
I haz da turbos
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Same here. My plans are for a daily driver with FI, for the occassional happy times. I think new rods and pistons, arp hardware, and maybe a new headgasket is more than enough to satisfy my needs. That with a very conservative tune, and i cant really see any reason why the engine shouldn't give you many tens of thousands of miles.
07-27-2006, 09:26 AM
#13
Originally Posted by gringott
That is the conclusion I am reaching. Most cost effective.
my good friend is going to build his engine with forged pistons running stock compression, for good off-boost response.. "rally cars do it all the time and beat the hell out of the motor" he says.. and i believe him. i think the stock VQ could run stock boost levels for a very very long time, ON the stock clutch, and would just need minor maintenance (example your car, my car) .. just get good tuning and leave it.
you can tell with the stuff that i bought for my build up, not many people would have done that. it's just i dont think i need a Rancor when a wookie will do.
07-27-2006, 11:12 AM
#14
Cheston: I hear you for sure, don't laugh, but you are my mentor
. I have been following your engine build plans, at the same time trying to educate myself somewhat (or should I say update my knowledge). We seem to me to have the same goals, esp. as you have posted them here. As you may know, I added the NISMO clutch flywheel package when I went TT, and it has served well without any problems at all - except for the noise we all know around 2K RPM. I am seriously considering going back to stock flywheel when I replace the engine. My main concern, really, was after I read the Corky Bell book, which seemed to echo the same thoughts that I had about engine build - good tune (engine management) (stock rev limits), good intercooling and piping, stable boosting, and more robust pistons and rods with a good rebuilt on the engine using stock bearings, ARP fastners, stock cams etc. I may be a fool - but I want to stay with stock compression. I am afraid of getting into the game with huge injectors - fuel systems - cams etc becuase it never seems to end, except for the money. I want to drive my car (in less than three years I have personally put on 54K miles, over 20K boosted). Not phone a shop to see how it is doing.
If I was tight with Techno like you, and lived in Cali, I would have reflashed for sure. But I was quite afraid of reflashes due to temp changes here (100+ summer, 0 or less not unknown in winter) and the inability for a reflash to compensate for temps.
I will follow your build with interest, in particular the pink injectors. Are you planing to modify the fuel delivery at all?
. I have been following your engine build plans, at the same time trying to educate myself somewhat (or should I say update my knowledge). We seem to me to have the same goals, esp. as you have posted them here. As you may know, I added the NISMO clutch flywheel package when I went TT, and it has served well without any problems at all - except for the noise we all know around 2K RPM. I am seriously considering going back to stock flywheel when I replace the engine. My main concern, really, was after I read the Corky Bell book, which seemed to echo the same thoughts that I had about engine build - good tune (engine management) (stock rev limits), good intercooling and piping, stable boosting, and more robust pistons and rods with a good rebuilt on the engine using stock bearings, ARP fastners, stock cams etc. I may be a fool - but I want to stay with stock compression. I am afraid of getting into the game with huge injectors - fuel systems - cams etc becuase it never seems to end, except for the money. I want to drive my car (in less than three years I have personally put on 54K miles, over 20K boosted). Not phone a shop to see how it is doing. If I was tight with Techno like you, and lived in Cali, I would have reflashed for sure. But I was quite afraid of reflashes due to temp changes here (100+ summer, 0 or less not unknown in winter) and the inability for a reflash to compensate for temps.
I will follow your build with interest, in particular the pink injectors. Are you planing to modify the fuel delivery at all?
07-28-2006, 09:18 AM
#15
Originally Posted by gringott
I want to drive my car (in less than three years I have personally put on 54K miles, over 20K boosted). Not phone a shop to see how it is doing. If I was tight with Techno like you, and lived in Cali, I would have reflashed for sure. But I was quite afraid of reflashes due to temp changes here (100+ summer, 0 or less not unknown in winter) and the inability for a reflash to compensate for temps.
I will follow your build with interest, in particular the pink injectors. Are you planing to modify the fuel delivery at all?
07-28-2006, 09:32 AM
#16
Originally Posted by Chebosto
i used to live in the Mojave Desert when they did all the turbo builds. trust me, we all the hot weather testing done. in 110+ F temps, and down to near freezing levels in the winter. my tune is pretty conservative when it comes to timing and afr, true its not the best for peak hp on a dyno, but damn safe to beat the crap out of it like i did and still be ok.. and i intend on ragging on this new engine after the break in.
besides new injectors, i might add Charles (CJ motorsports) Fuel tank mod fix, but no real return line.. maybe modify the fuel rails but until we see what we're lacking, i'm trying to do it a minimally as possible.. no need to spend extra $ when i dont have to.
besides new injectors, i might add Charles (CJ motorsports) Fuel tank mod fix, but no real return line.. maybe modify the fuel rails but until we see what we're lacking, i'm trying to do it a minimally as possible.. no need to spend extra $ when i dont have to.
07-28-2006, 09:52 AM
#17
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Originally Posted by JeffesonM
If I was building the motor for a DD, I'd get Eagle rods, Arias pistons and ARP hardware, and call it a day... should be fine for 500whp, which seems more than enough to spin the tires on the street.
07-28-2006, 10:27 AM
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I wish i was on an unlimited budget.. lol. as far as my wife knows the turbo kit cost includes install, tune, and built motor..lol. and i have no plans of telling her any different..lol...lol...lol... but if i already saved for a certain amount, taking extra time for a few more dollars wont kill me, only if she finds out....lol..lol.. If eagle rods can get the job done, than i would consider them.