Anyone know approximately how much H.P. I'll lose with Low Comp Pistons?

[sjs]

So let me understand this correctly then.
Since I was forced to use JE pistons in my rebuild, they came with new wrist pins already?

Most likely yes. They typically come with the pistons, and the rods are modified to accept them. Since the pistons are custom I suppose they could be made to fit the original pins, but that would seem highly unusual.

 

[Turbo NSX]

Paul, IMO I do not understand why you are not taking advantage of your situation and go with the full engine build. There are people that are waiting in line to have Gerry work on their car. Do you think that if you build your motor to stock and then later go with FI that you will get your car back in to see Gerry without waiting on a list a mile long. You also would have wasted all that motor on a stock rebuild.

Buckle down, save your pennies, do the full build, how could you possibly regret it. Not to mention you will have a few months to save while the motor is being built.

 

[Black&Tan97Tnewportbeach]

Yeah Man - sell some guitars, the dog, a few couches, a few pints of blood . . it will all be worth it . . get a fuckin nuclear-war proof pro-sleeve GJ Especiale

 

[paulviriyapan]

Well guys, at this point the money just doesn't matter to me. The rebuild is gonna be at least $7k, and then you throw in a new clutch, waterpump, misc. crap that you need to fix on the way...either way it ain't cheap. All the $$ to modify beyond the rebuild it is basically nickel and dime stuff when you consider that the main bulk of the cost is for labor to dissassemble/reassemble, machine it, and balance it. The darton sleeves are an additional $1800 (not a big deal-I've blown more on stupider things) and the low comp pistons are the same price as the regular pistons.

What I really CARE about is the performance, and my concern is that if I put in the low compression pistons it's gonna make LESS horespower than stock compression when running N/A.

I was thinking about it, and I am doubtful that I will go the turbocharging route in the future. I have no doubt that Gerry's is the best and most reliable kit out there, but I was thinking that this car is my daily driver and there is alot more maintenance and things that could potentially go wrong with F/I. As my DAILY DRIVER, I was thinking I should leave well enough alone. As such, the stock compression would make more horsepower as I would not be turboing it.

Is there more horsepower or other advantage to be made by building the engine? I really don't know, and hope someone could clue me in here. What I really care about is performance from my car, and the money issue is secondary to this. Basically what I want to know is what are the advantages to low comp pistons and having it sleeved? From what I understand, low comp pistons will give me LESS power, and the sleeves wouldn't do anything to increase performance.

The only thing that I would potentially do in the future is run Nitrous on it. From reading this forum it seems that the stock internals are sufficient to run a 100 shot without problem. If I had the engine built, would I then be able to run massive crazy shots of Nitrous (oh, say a 200 shot?) If so, I'm soooo there. Someone please help me out here. Are there any other advantages?

P.S. I already sold my guitar collection a while ago--actually to fund my purchase of a Porsche 911--which subsequently caught on fire. Had to let go of the marshall 1/2 stack and a Gibson Reissue Firebird. Now I'm down to a '74 Les Paul Custom--made the same year I was born.

 

[Black&Tan97Tnewportbeach]

Yeah with the full build you could safely do the 2-stage nitrous like 100 shot stage one, 150 shot stage two . . or something similar I am not that familiar with nitrous setups but you could ask that BadCarma guy he seems to know about it really well . . also talk to Gerry's customer Rob in MD, he has the full build and runs Bell Turbos and a big nitrous shot . .

 

[len3.8]

At this point, I'd pay for your car, so I can get mine in there.
Seriously, maybe you should talk to the person with your engine and make a decision, based on that, I would then decide what to do, Now we are off into the 200 shot tangent. I don't know if you were seious are not, but you have a lot of variables that YOU need to consider. As Turbo has said, there are others waiting, and you are holding up the flow

I can see your dilemma, I have contemplated a similar situation over the last few months. I can appreciate you wanting to take your time and get an informed decision. I would as well. You basically said the Turbo is out, Build it for the nitrous and get on with it.....

Sorry if this sounds self serving..... because well it's meant to be.
Sorry Paul, I'm kinda behind you in the flow somewhere.
Meant in good sport.

 

[NetViper]

If you are just doing an engine rebuild, isn't it cheaper to just get a used motor from ecocar or something?

 

[Yellow Rose]

If you are just doing an engine rebuild, isn't it cheaper to just get a used motor from ecocar or something?

Dave - think for a moment......we are talking about high HP engines; therefore, stock used engines for this application are worthless.

 

[MiamieNeSeX]

I have no doubt that Gerry's is the best and most reliable kit out there,

How did you come up with that? As we all know Jerrys car runs hard, how many of his systems are out there running? It definatly puts out some serious HP .
Armando

 

[paulviriyapan]

Sorry if this sounds self serving..... because well it's meant to be. Sorry Paul, I'm kinda behind you in the flow somewhere.

Well then Len, maybe you should have thought about your proximity to Gerry Johnson before you decided to live in Missouri....If you lived in California, you'd have Ahnold as your governor AND your car would be done by now. HAHAHAHA!

In all seriousness, there is really nothing that can be done at this point. The car has been with Gerry since the end part of November. He was so behind he couldn't get to pulling the engine for a few weeks. Right now we're waiting for the pistons to arrive from JE, and there's nothing that can be done until that happens. So basically the car is just sort of sitting their passively...with nothing being done to it until the parts arrive. Your real culprit is none other than MR. BLACK&TAN97NEWPORTBEACH for whom Mr. Johnson is still trying to figure out how to make the Tec3 ECU mindmeld with the OBDII.

In regards to buying the used engine, it was about the same, maybe MARGINALLY cheaper to buy an engine from a yard. (Keep in mind some places were asking $8k for a used engine.) However, I was really against that. The previous owner of that engine obviously did something to the car that caused it to end up in a wrecking yard. I have no verification that the engine actually has the mileage the yard claims, and even if it does, there's no telling whether those 30-40,000 miles were hard driven, I-didn't-change-the-oil miles. This way, I know where the engine has been, what has been done to it, and (since Gerry is involved) that it is DONE RIGHT.

BTW, the cost of the rebuild isn't as expensive as it should be because we are using the JE pistons. If you ever priced NSX engine parts, you would freak out. The pistons are nearly $6k per set ($900 per piston), the crankshaft is $2800, new cylinder heads (didn't need that) are $5k a set, and a complete new engine from Acura is $30k.

 

[paulviriyapan]

Posted by MiamieNeSeX:

How did you come up with that?

Geez, given the other thread containing a heated debate about blown engines...I really don't want to get into that. All I can say is that given what I know about Gerry's Kit, and what I know about Gerry, I would have absolutely no worries about my engine blowing on his kit. The only other F/I kit I would feel comfortable with is the Comptech kit, which I also think is safe. Gerry's kit makes a hell of alot more power that CT and that's why I think it's the best.

 

[MiamieNeSeX]

Posted by MiamieNeSeX:

Geez, given the other thread containing a heated debate about blown engines...I really don't want to get into that. All I can say is that given what I know about Gerry's Kit, and what I know about Gerry, I would have absolutely no worries about my engine blowing on his kit. The only other F/I kit I would feel comfortable with is the Comptech kit, which I also think is safe. Gerry's kit makes a hell of alot more power that CT and that's why I think it's the best.

I did not try and sell GJ system short, but with only a handful of cars with the system installed I dont know if you can say its a proven system.Not to say that it dosent perform excellent.


Armando

 

[KGP]

Right now we're waiting for the pistons to arrive from JE..

Sounds like you already made your choice, no?

 

[len3.8]

How did you come up with that? As we all know Jerrys car runs hard, how many of his systems are out there running? It definatly puts out some serious HP .
Armando

He could be basing it purely on what's available for Turbo kits and not Superchargers. The supercharger systems have been discussed in great detail all over this forum, in the past as well as currently. If I were going to buy a Turbo, would I look to the Bell system, out of business for the most part, NSXMod--- trash, Cybernation- never materialized, Gerry has cars with it on them.
FactorX putting them on as we speak. In his pool to pick from, his statement does have some weight.

 

[MiamieNeSeX]

He could be basing it purely on what's available for Turbo kits and not Superchargers. The supercharger systems have been discussed in great detail all over this forum, in the past as well as currently. If I were going to buy a Turbo, would I look to the Bell system, out of business for the most part, NSXMod--- trash, Cybernation- never materialized, Gerry has cars with it on them.
FactorX putting them on as we speak. In his pool to pick from, his statement does have some weight.

I agree that there isnt alot available if you go the Turbo route(but this is true of all FI for the nsx), but just because there is little choose from (and GJ definatly sounds like the best) still not enough hours and different owners to be called proven IMO. PS: I think few FI kits can say that by the way.

Armando

 

[len3.8]

I agree that there isnt alot available if you go the Turbo route(but this is true of all FI for the nsx), but just because there is little choose from (and GJ definatly sounds like the best) still not enough hours and different owners to be called proven IMO. PS: I think few FI kits can say that by the way.

Armando

I guess we would have to qualify the word proven. How would we do it? Are we going to base it on mileage? Are we basing it on HP/TQ produced? Are we basing it on service intervals? Are we basing it on tuning? So many variables. If we lump all of them together SC's and Turbo's, who's would compile the best factoring in all categories? Most likely Comptech, they have a lot of units out there... However, some peope have said it was way too conservative for what you get. But you still can't argue with the fact that they have a lot of cars out there with many miles on them. GruppeM, I have never really heard anything bad about that Supercharger, nor have I heard much about it. BBSC, there are cars out there, and with some current #'s and tuning being placed over the boards (THANK YOU ALL BY THE WAY) by the owners that have them, they seem to be going in the right direction now. Bell system (?) Some people have them and they are having problems with no one to turn to. Some of them are resulting to hybrid systems. FactorX is installing as we have heard, their car was witnessed at Xpo..... Gerry's system is on more than a few cars... He has posted his dyno's before and stated his numbers like everyone else. Well almost everyone.
He has a car with what would be considered high miles, many of them hard on his system...... Based on the info we have all been given you are correct, Few FI's can be called proven. If I were gambling , it would be a judgment call, big HP or small HP.
Big HP I would go with the system that gave be the best performance and has been used frequently... Small HP well Comptech is on my car now..... I guess we still in the begining stages of FI, peopleare figuring them out, this board has sped up the process.

Based on DYNO #'s, Based on Mileage, Reliability (what we know now) What else should we consider.
I am rambling I know, but I hope I made some sense..
WB posted some decent #'s after further tuning of his Car.

 

[Arata]

Forged pistons are not necessarily lighter and are often heavier (more dense) than cast. They could be lighter by making them thinner and with smaller skirts (not easy on the NSX) if that were a design goal, but it isn't always the case. (In fact, I personally haven't seen it in other engines I've worked on) They are much stronger of course, which is why the extra weight can be tolerated at high RPM.

You must be buying the wrong forged pistons.
The whloe idea of a forged piston is that by the forging process it is stronger than a cast piston, the additional strenght allows less material having a higher strenght, less material is less weight. There are some drawbacks to a forged piston, but weight is not one of them.
The newest high performance HONDA motorcycles engines come stock with forged pistons, you may see the same in the high performance HONDA automotive engines.

 

[sjs]

You must be buying the wrong forged pistons.
The whloe idea of a forged piston is that by the forging process it is stronger than a cast piston, the additional strenght allows less material having a higher strenght, less material is less weight. There are some drawbacks to a forged piston, but weight is not one of them.
The newest high performance HONDA motorcycles engines come stock with forged pistons, you may see the same in the high performance HONDA automotive engines.

Well, I’ve been using pistons from Cosworth, Venolia, and Aires (not Airas). Admittedly most of what I’ve used are not the newest low expansion alloys, but compared to the stock cast pistons in old Datsuns and engines of that era, the forged replacements are heavier. I will concede that with the exception of my turbo Z they have all been domed high-compression pistons and even with the dome undercut they have somewhat more material than stock, but I don’t think that alone accounts for the difference. Perhaps someone with more metallurgical expertise than me can help us out here, but my take on it has always been that forged parts aren’t necessarily lighter in absolute terms, but are far stronger per unit of weight and volume. I believe that a forged item is inherently more dense (molecules more tightly packed) than a cast equivalent, so I think it is a common misconception that forged is synonymous with light. We do agree on the fact that a forged item is “stronger“ of course, but you seem to assume that they take advantage of that fact to make it thinner and therefore save weight compared to stock, placing the emphasis on weight. Perhaps that’s true in the case of some cars where the stock pistons are tanks (like a low-tech low reving V8 being built for higher revs), but small displacement high reving engines (including the 1969 Datsun L16) have remarkably light pistons. Pick up a stock NSX piston and you’ll know what I mean. From my observations the forged pistons, especially ones intended for very high compression & revs or forced induction, are not thinner at all. But they are much stronger as well as more resistant to things like detonation. In other words, they accept a little added weight for a lot more strength.

Certainly someone out here can weigh a stock and forged piston for the NSX. I’ve got some stock ones laying around and could weigh one on the rod, or press it off if necessary. I’ve also got a variety of forged L-series Datsun pistons but no stock ones without tearing down an old block.

 

[NA1 #2853]

well i just picked up a spare nsx block, as i plan to build that one up, while i am driving on my current one.

I plan on measuring and weighing everything because i have beat me head into this computer screen trying to search for information like this and no one has hard numbers.

I was looking for;

- Stock NSX Piston Weight
- Stock NSX Rod Weight
- Stock NSX Crank Weight

I want to compare those weights to;

- JE, Arias, or other Pistons
- Crower Maxi-light, Carrillo, or Other Rods

Anywho, i'll post the info on my homepage when they get measured.

-Ray

 

[sjs]

I have previously posted the weight of the stock bare block, rod + piston, crank, heads, etc. I have not separated a rod and piston for their individual weights, so I'll be interested in what you find.

 

[Arata]

We do agree on the fact that a forged item is “stronger“ of course, but you seem to assume that they take advantage of that fact to make it thinner and therefore save weight compared to stock, placing the emphasis on weight.

I do not assume it I know it for a fact.
The reason a forged piston is stronger is not oly because the structure is more dense, but also because the grain structure is aligned.
Metal has a grian structure, just like wood, and just like wood this grain can give it great strength. Try spiliting a piece of wood against the grain it has great strenght, with the grain little strenght, with a cast piston you have little to no grain structure, with a forged piston, that is the whole point, to have a structure.
If you think the piston manufactures do not take advantage of this, you are completly out of touch. You are using a 1969 Datsun piston as your example, try looking at some pistons made in the last 10 years, FOREGED PISTONS are LIGHTER.

 

[KGP]

I do not assume it I know it for a fact.

If you think the piston manufactures do not take advantage of this, you are completly out of touch.

Quite absolute statements you make here, and you surely could be right. However, since you know for a fact, why don't you give us the facts. Until then it's heresay - no disrespect intended. What's the OEM weight, and what's the weight of whatever forged pistons you refer to for the NSX? After all, we are talking about NSX pistons when we get down to it, right?

 

[Arata]

As it is Sat, I cannot get those weights, I will be happy to call JE on Monday and get them if you do not want to.

For now I will give another example.
The NSX pistons are 90MM and 93MM, 3.0 and 3.2 motors.
Here is a piston from a Honda RC51 this is a V twin with 100 MM pistons 10200 RPM rev limit.
Four valves per cylinder DOHC.
The stock piston is 410 grams, this is a cast piston. The JE forged piston is 370 grams. the JE is a higher compression ratio.

Keep in mind the aftermarket forged pistons are made from blanks that may different pistons are made from so they tend to have extra material so they can be used in many applications, when you see an OEM forged piston, it is a dedicated forging so the weight is even less. Oh and of course the OEM castings are also a dedicated casting so their weight is usally at its minimum.
And the aftermarket forgings are still lighter than stock.

From the JE catalog "With over 300 individual forgings to choose from, JE is able to achieve specific compression ratio requirements while reducing overall weight"

Even JE thinks they can make lighter pistons.

 

[Arata]

As it is Sat, I cannot get those weights, I will be happy to call JE on Monday and get them if you do not want to.

For now I will give another example.
The NSX pistons are 90MM and 93MM, 3.0 and 3.2 motors.
Here is a piston from a Honda RC51 this is a V twin with 100 MM pistons 10200 RPM rev limit.
Four valves per cylinder DOHC.
The stock piston is 410 grams, this is a cast piston. The JE forged piston is 370 grams. the JE is a higher compression ratio.

Keep in mind the aftermarket forged pistons are made from blanks that may different pistons are made from so they tend to have extra material so they can be used in many applications, when you see an OEM forged piston, it is a dedicated forging so the weight is even less. Oh and of course the OEM castings are also a dedicated casting so their weight is usally at its minimum.
And the aftermarket forgings are still lighter than stock.

From the JE catalog "With over 300 individual forgings to choose from, JE is able to achieve specific compression ratio requirements while reducing overall weight"

Even JE thinks they can make lighter pistons.

Let me add another example
A Kawasaaki ZX636 piston, this is a Stock cast piston 68MM 150.03 grams

Kawasaki ZX600RR, this is like a type R version of the 636 except it is only 600 CC instead of 636CC it uses a 67 MM piston that is a factory forged piston. 137.34 grams

And last some JE pistons I had made for the 636 motor, same dome shape same compression, except that they are 2 MM larger at 70 MM they weight 144.05 grams. still lighter than the stock cast pistons.

 

[KGP]

Arata, I don't doubt that you are not knowledgable. Your background in Bike Racing engines tells me that. But, when you make some specific claims, leaving no room for error, you need to be able to back up your claim. Quite a few of your posts refer to bike engines, which is fine as long as there is a correlation. As to the JE catalog claim of: "With over 300 individual forgings to choose from, JE is able to achieve specific compression ratio requirements while reducing overall weight" - that's just fine if they made that statement with NSX OEM pistons in mind. As to caling JE, suite yourself. I really could care less but others might want to know. The pistons I ordered are Wiseco's.

And by the way, I don't think there are many on the forum who think sjs is "completly out of touch."