DLin05

I found these while lookin around for new parts....theyre pistons from Esprit Tuning. http://www.streetsports.com/Tune/350Z/Esprit.htm#aero
Supposedly they raise compression ratio to 11.5:1 and cost 2750. Anyone with more information on this? Any addition thoughts, how much hp gain would this be?

krinkov

Uh, you know JE/SRP will custom cut any piston from billet for $250/ea.
http://www.jepistons.com/index.asp

joeshow750

I don't shop for pistons too often, but that seems pretty expensive. In fact, everything on their site seems pretty expensive. However, I am curious to see a dyno run with these pistons. This may be a perfect mod for those that wish to stay NA.

ares

iTrader: (2)

yes, also a perfect mod for those that enjoy running race fuel 24/7.

11.5:1

93 octane aint gonna handle that. and these of course would be totally useless for those going FI, for those that werent sure.

krinkov

Actually, bigger cams lower your dynamic compression, this is why when you use bigger cams you run pistons with a higher static compression to bring you back up, so depending on what kind of cam is used this compression may be just fine on premium gas, just dont try to pass a smog test

2k3silver350z

my old rsx handled 11:1 pretty well and it also handled the type-r pistons plus the spoon headgasket pretty well also on 93 octane. compression should have been around 11.5-8:1. never had one problem and the motor is still running strong.

krinkov

your RSX had a couple things going for it, variable cam timing and VTEC(multiple cam profiles) a high compression car detonates as it gets up in the RPMs and under load, on a VTEC engine the cam profile changes at high RPM, thereby lowering the dynamic compression ratio at the loads that would otherwise cause detonation on another car without VTEC with that compression ratio. The 350Z has the variable cam timing, but all this does is change the advance/retard of the single cam profile, this does alow a bit higher compression but nowhere near VTEC

BigBadBuford

I don't think 11.5:1 compression would give you any problems. With modern combustion chamber design and aluminum heads they are a lot more detonation resistant than older cars w/ iron heads. Plus, the motor has a knock sensor so if you do get some detonation the ECU will retard timing to compensate.
For the price of the pistons, I don't think they are worth it at all. Pistons themselves won't give you too much power. The extra compression might give you around 5% more power. If they are lighter than stock that would save some stress on the rods. If you are building a street motor I wouldn't even bother if you are going NA. If I was going turbo I would just get a set of custom JE's.

Jason

Celica GT-S has 11.5:1 compression and handles that on 91 octane just fine.

krinkov

toyota V V T-i has multiple cam profiles as well, so same goes for wht I said about VTEC

S12 driver

At such high CR, would alcohol injection help to eliminate detonation?

krinkov

yes, it would this is actually not as bad as it sounds, we hooked up an efective alcohol inection setup on my buddies 24psi Eclipse a few years ago, bascially a Walbro fuel pump running from the windshield wiper tank that was set off with a MSD RPM switch, still has the car and it works great. I think Jackson racing actually makes a kit for this but its around $500+ whereas this one was made for well under 100. Thing is, I might consider this on a FI car, but on an NA car its best to just start off with the right compression pistons for the gas you intend to run. As I said, JE will custom cut pistons for half the price of these guys so its not like your only choice is 11.5/1 anyhow.

2k3silver350z

VTEC, I-VTEC and VVTI do not make that much of a difference in dynamic compression. as i said my engine was running at around 11.8:1 compression ratio and i never had a problem. the cam timing could not take out more than .1-.2 compression. you are paranoid. 11.5:1 will be fine on 93 octane gas.

krinkov

my paranoia has nothing to do with this bro! but yes, changing the cam profiles has a HUGE effect on the dynamic compression since longer duration cams(IE, the big vtec lobe) have a large overlap area, this is the amount of time the intake and exhaust valves are open at the same time at the end of the exhaust stroke/beginning of the intake stroke, this is where you lose compression. Since at high RPM, the amount of time the the intake valve stays open gets proportionatly shorter, this loss of compression is more than made up for by being able to keep the intake valve open longer. If you dont belive me about the compression diference try to run your car with the vtec engaged at idle(running big lobe) the car will lope or just die thats how big the compression difference is.

Beside, I NEVER said you couldnt run 11.5/1 on 93 octane , that was Ares, I just started in with this whole compression thing. As a matter of fact, your chances are even better since the Z is designed for 91 octane(all we get out here )

Street Sports

I agree that the Esprit pistons cost more than JE Pistons would. If any of you have looked around our site, you will see that we almost exclusively use SRP or JE pistons when we build engines. I have had problems with them in the past, but I still prefer them over other brands. BUT, it is from this experience that I can also tell you that it's not a simple matter to just have JE make pistons. There is quite a lot of information that you have to provide them in order for them to make a custom set. It is easier to have them make a lower compression piston than a higher compression piston. About 90% of the information they need can be achieved by just sending in one of the pistons you take out. Then it takes 6-8 weeks to have them make the set for you. So the first question is where does the sample piston come from. Is someone going to tear their engine down to take one out? That's a lot of downtime. Second, when going higher compression, a boatload of additional info is needed such as block height, deck clearance at top dead center, thickness of the head gasket you are going to use, camshaft specifications including valve lift at top dead center, gross valve lift, duration, degree of lobe separation, as well as cylinder head information such as combustion chamber size and shape. All of this information is required to determine where and how to place the valve reliefs in the piston dome and how to shape the dome to make the compression that you require. Then after all this is done, you occassionally have to bore the block to make them fit. I am having to do that right now on a 95 Nissan 240SX with a KA24DE engine. You see, although they could make the pistons any size we wanted, we had to go with a 40 over piston in order to get a set of rings that would work. Thankfully, the customer does not mind machining the block to accomodate the big JE slugs. Maybe the bore size of the VQ35 would not present the same problems as the KA24DE does, as I have not looked into it. And I am not trying to convince anyone here that everyone here should run out and buy the Esprit pistons. I am just trying to say that ordering a set of custom pistons is not as easy as you might think. Also remember this, JE pistons are made of an aluminum that is strong, but has a lot of expansion to it. That means you will have some knocking and blowby when the engine is cold which will contaminate the oil fast. I do not have very much information on the Esprit pistons to give, but they may be made of a material that is much more "streetable." If that is so, then they might be a much better "deal" than we all realize. I guess I have a little homework to do on the Esprit pistons now. I didn't mean to confuse anyone, just trying to help everyone make better informed decisions.

Shawn @ Street Sports

krinkov

No confusion here and if that is what they are going for you have every right to sell them for as much as they normally retail. Some parts makers are more expensive than other options and theres no need to make excuses for giving eveybody every option available and let them decide.

That said, I would hope that anyone even considering doing an engine rebuild in the first place would take all fore-mentioned tolerances into consideration before using different pistons, custom cut or aftermarket. As far as the Esprit being a different material, I asume you mean hypereutectic, well this might be a bit better in a long term reliability, but I cant imagine using hypereutectic in a perfomance application since they have serious performance shortcomings.

6-8 weeks is way longer than we ever waited, Talk to Lawrence there, hes the man we used to get our custom Cosworth pistons in 2 weeks. Then again we droped about 20K a year on thier pistons

Street Sports

We are currently only waiting about 4 weeks for the KA24DE piston set.

About the Cosworth pistons you had made. Are you speaking of JE pistons for a Cosworth engine? The reason I ask is that Cosworth has recently approached us regarding making low volume exclusive parts for us. I am just wondering if you have had any experience with their products. The only experience that I have had is JUN pistons. They are designed by JUN, but made by Cosworth. Apparently Cosworth in England has some equipment and/or manufacturing techniques that are unique to them. I am sure that JUN is not the only company using Cosworth's services, just the only one I know of. I have never had any problem with JUN pistons, which tends to make me think that I could do no wrong by taking Cosworth up on their offer.

I wasn't necessarily speaking of hypereutectic pistons. BUT, although it has long been understood that forged pistons are stronger than cast, what is not as clear is how strong hypereutectic alloy pistons really are. Pistons operate at a relatively high temperature, and most engineering materials lose strength at elevated temperatures. The point at which a material deforms permanently under load is called the “yield” point of the material. Any loading below the yield point may deform the material, but it will return to its original shape (called the elastic range). If a piston were loaded continually in the same manner, the only material property of importance would be the yield strength at the operating temperature of the piston. For parts that are loaded cyclically like pistons, the “fatigue strength” of the part at the operating temperature must also be considered, which gives an indication of how many times you can apply a given load to a part before it will begin to fail. These properties were evaluated for hypereutectic pistons by Sealed Power and published in the December 1995 issue of Car Craft along with comparable data for forged pistons. Yield strength and fatigue strength of hypereutectic alloy material was shown to be substantially higher than that of a forged piston at all temperatures. Therefore for comparable piston designs operating at comparable temperatures, the hypereutectic piston is the strongest. Below are the charts given in the article.

Shawn @ Street Sports

krinkov

I had worked for engine builder Dave Vegher of Veloce Motors most of the last 3 years. Typically when we would get a Cosworth enige in , 2 liter or DFV, we would replace all cosworth pistons with JE. I had not heard any specific reason why we used JE piston exclusivly, but the "old man" had his reasons for everything and with his customers, the reasons were never economic. I'll ask him on Monday anyways.

I see what your saying about hypereutectics, my only concern is that this higher operational stregnth(ie, high silicon content) comes at the cost of higher risk of detonation related failures they are notorious for. Sort of like the harder steel that makes the blade sharper also makes it more brittle

You have alot of great info Shawn, I look forward to seeing more of your input on other topics

ImportPartsPro

iTrader: (512)

Actually we have done just that. We are working on custon pistons, rods, valves, valve guides, retainers, and ARP studs. We will do both high and low compression pistons for the guys who want to stay N/A and for the guys who go S/C or turbos.

krinkov

thanks Kyle! Please keep us updated!