dazdavies

iTrader: (22)

After managing to hole Number 3 piston at the weekend I am wanting some help with piston choice.

Do I spend silly money on a set of RCMS Omegas or Will something like JE pistons or Wiseco Do.

If I get JE or Wiseco from the states I can almost get a set of four for the price of 1 Omega from RCMS.

Looking at running circa 450 - 500bhp on these (eventually)

So My real question is I know the Omegas are good but what are would any of you go for
JE Pistons or Wiseco

Cheers

Daz

john banks

What are the present pistons and how did you hole one of them? Boost/turbo/power/torque? Intercooler? Octane? Plugs? Detonation? AFR? Overheated on a heavy boost/top speed run/track?

dazdavies

iTrader: (22)

Hi John Thanks for the reply.

The engine is an STI Ver 5 engine that was rebuilt with new crank, eagle rods but I decided to keep the STI Forged pistons.

The car has had a fair bit done to it. and runs a VF34 at 1.5bar with Ecutek remap done by Andy Forrest. Full Decat and GT headers.

Power is circa 360bhp. I still have the top mount on and the car has done 18,000 reasonably hard miles like this.

The car is always run on Optimax and I think this has happened as a result of running lean on a spirited play with on 05 STI yestreday.

I think the 440cc injectors reached there peak as the car has been performing extremely well of late.

Going to Look at a forged 2.5 short motor too after talking to mark at lateral

Aztec Performance Ltd

iTrader: (234)

What TMIC did you have?

p1mark

Blimey, i feel bad about saying to you the other day your pistons were still the weak point

I have used JE a lot in bike racing engines. They used to vary a lot in diameter and wieghts between each supplied piston, and when i chopped some up the crown thickness was varying by up to 2MM. Dont use them now and normally go with Wiseco or Cosworth (ouch)

I have no experience of them on scoob engines though.

banny sti

iTrader: (68)

iirc daz has a standard tmic

dazdavies

iTrader: (22)

Banny is right Standard UK Top Mount.

Dont worry mark I hold you fully responsible for the piston curse you cast. The bill will be in the post shortly
On a serious note I always knew they were the weak point but I dont think the fact that using standard 440s and the standard top mount when running 1.5/6 bar all the way to the red in 5th help the situation either.



Funny that my mate has built loads of bikes and he swears by JE he has a 175bhp 125 ft/lb Spondon based on a Bandit 1200 and that is a pure evil machine. That had JE in so I am torn although I am steering towards the Wiseco's it has to be said.

I'm thinking of an all steel 2.5 Monster now ?
Got a great price an a 2.5 short motor with pistons and I can use my current rods too.

Daz

p1mark

I never had a failure with JE's, its just that NA race bike tuning is as much about blueprinting as it is about tuning, and i was fed up with having to machine stock out of the inside of them to get them balanced.

Wiseco and cosworth 5 mins with a mini die grinder and they were spot on. just a slight quality control thing i think.

john banks

Thanks for the info. The STI OEM pistons are actually quite strong, so something has possibly got too hot and resulted in pre-ignition, especially suspect this if it is a hole in the crown of the piston? When rebuilt you need to go through all the possible components that could have resulted in failure - airflow meter, knock sensor, fuel pump & regulator, spark plug, injectors etc. Were you monitoring knock or AFR?

dazdavies

iTrader: (22)

The rebuild is going to be done properly I'm going to document it all in projects too. I have not been keen on the fueling set up for a while.

Going to go with Parallel rails with SX reg and some bigger injectors.
The Maf is ok as I change this as a service item these days.
As for knock and AFR no I wasnt monitoring it but I shall be doing so. Via the Apexi Power FC I have sat in my drawer.

I just think the 440's were maxed out. It was a cold day lots of boost and I was just too hard on it.
I had a slight loss of power and throttled off but had some smoke out of the exhaust. I'll have a look at the weekend when I get the engine out and strip it.
I am pretty certain I'm going for a 2.5 Forged Short motor and running RCMS GT35 garrett/IHI hybrid turbo with ported shroud and a P20 exhaust housing.
Didnt you have some issues with head gaskets on your 2.5 John?
What are your thoughts on this as I wish to run circa 450/450?

Cheers

Daz

john banks

PowerFC can flash the CEL if the injectors are maxxed or knock threshold breached.

If RCMS are doing it just go with their advice. I had headgasket issues, but the heads had been on and off a few engines. If you are doing a built engine I would go to the effort of a correctly sized rotated Garrett for maximum power band. Comparing my old Ion P450 (IHI P20 hybrid) and the rotated GT30R showed the latter spooling up very similarly but blowing a fair bit harder. You can get a short, straight 100mm inlet pipe drawing cold air in there, external wastegate, wheels in their proper housings as Garrett intended etc and more flexibility for mixing and matching cores, wheels, housings etc. I would suggest you consider a GT30R-12 with 0.63 AR exhaust housing, I had 0.82 AR and it was a bit laggy for road use. There was a nice post on NASIOC with datalogs that showed a nice difference in spool and comments on transient response between the two housings. For a stock EJ257 I still think the TD05H-20G is best running about 380-390 BHP and 400 lbft, and arguably the nicest road car by far, depending on your preferences.

dazdavies

iTrader: (22)

Thanks John,

Although some of the parts will be sourced from RCMS I am going to do the rebuild myself. I built the current engine just wish i'd gone with pistons at the time too.

Been thinking of a twisted GT30R for sometime and will now have to do a price comparison between that and the RCMS Garret IHI Hybrid.

Does anyone know if Andy does a kit for a twisted GT30R including uppipe and downpipe and wastegate?