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Discussion Starter #1
I'm contemplating to upgrade my pistons and conrods during the spring (after getting a new ECU) and was wondering on the effects that it could have. After having spoken to Ralliart Germany (we can do the work, but won't start the car unless it's a Motec. Thanks a lot!), I wonder what would need to be changed on the ECU map after having fitted wider pistons and new conrods. I suppose the fuelling would have to be altered a little because of the different size of the combustion chamber, maybe even the timing. But shouldn't the car at least run? To be fair that's what Ralliart Germany said, that the car would probably run, but not smoothly. I'm a bit disappointed that these professionals say they won't be able to adjust the GEMS, although I think that the changes would have to be minor and I think the interface should be similar to the Motec.
 
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Discussion Starter #2
If the compression ratio is the same on the new pistons it will run fine with the ignition timings unaltered.

As for fuelling - closed loop - no problems.
Open loop - either 1.18% increase in injector opening times or a 2.31% increase in base fuel pressure would cancel out the increase in bore diameter.

The fuel pressure would be a very easy fix using an adjustable fuel pressure regulator.
B and amp;M command flow AFPR kit for the US Mitsubishi Eclipse might fit.
 
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Discussion Starter #3
Why go oversized? I didn't. I am pretty sure that the Extreme S doesn't either (and neither did the RS450) - both of which use the same Omega pistons that I have. These are not noisy (no piston slap) and in 2000 track miles I have not used a drop of oil! Extremely good.

Why do you want to change the pistons? Presumably it is to go above 1.6 bar. I really don't think there is much point going over about 1.55 bar on the standard turbo. Yes, you can get a bit more power, but the reality is that the standard turbo chokes the car. Peak power before rebuild was 360bhp at 6800 rpm. Now it is 380 at 6100 rpm. It is STILL 360bhp at 6800rpm. You see, what has happened is the midrange has increased, but the peak hasn't given me a new, false, lower peak. With a new turbo, that won't happen (and I will look forward to 400|PLS| bhp). If you aren't going for a new turbo, all you can do is tune for torque in the midrange - rally style. Above 1.6 bar the gains are really small on the standard car. You need a different ECU just to be able to map boost higher in the midrange, but the power curve becomes stranger and stranger. The nicest power curve is at 1.55 bar, where the turbo is still reasonably efficient.

Lightspeed can probably give us a nice techy explanation as to what the turbo is doing here.

From my experience, as a road car, I would:

Set the boost to 1.55 bar
Use standard remapped ECU
Gasflow the head
Fit new cams, springs, valves etc.
Fit new head gasket
FIt water injection
Fit PE downpipe, de-cat and 3 exhaust all the way
Fit cold air intake, turbo elbow, closed air box etc.
Fit boost controller

You should see 360bhp and 340 lb/ft at least, and very reliable too. Now I know you have most of these already...

Just interested really to see where you are going with the car... :)
 
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Discussion Starter #4
blade
since you seem to be in the know what is the internals off the extreme models ? are they standard with con rod bolts done or is there more to it ?

thanks in advance

sam
 
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Discussion Starter #5
The Extreme S and 'ol RS450 both have Omega pistons, which I believe are 85mm, and also Arrow conrods. This is from an Extreme 7 S owner and an RS450 owner, both of whom were intimately involved with Ralliart developing the cars, so had good knowledge. I have the same pistons and rods I believe, though without removing them and comparing, I can't be sure!
 
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Discussion Starter #6
blade

You think the car will run fine with std internals at 1,55 bars? Are you talking peak or held? I am confused as to whether you need to change the rods for 350 bhp approx. Ralliart say yes, others no. I am not sure as to how much of it is true / safety measure and how much of it is to make a sale. I guess it is just to be safe...
 
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Discussion Starter #7
thanks blade, but is there an extreme and an extreme S ? or are they both the same car ? if there is does the normal extreme also use uprated internals ?
 
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Discussion Starter #8
Blade,

I've got PE set up as listed in your post, but have not got headwork done or cams changed, My car always makes 360|PLS|bhp and 340|PLS|lb.ft at PE. Mervyn and amp; Dave always scratch their heads cos it makes more than their own car. I boost 1.64 max and 1.4 at 7Krpm.

How much would the headwork and cam change give me - or would I need to get a bigger turbo. Internals std except for ARP rodbolts.
 
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Discussion Starter #9
Claudius - the RS engine came with uprated bolts, so I guess that means it is needed.

Sam - There is both an Extreme and an Extreme S - the S has the uprated internals and runs higher boost.

Evo Too - Yeh, my engine did the same as yours, and Merv scratched his head at that too! Some engines are better than others, boosting max at 1.64. The headwork will give you maybe 20bhp more, but may loose you abit of torque. Perhaps on yours you may see 370bhp, 330lbft - tricky to say. I wouldn't bother with cams - you will loose bottom end. They really work best with a new turbo as you are shifting the power band higher.

If you go bigger turbo, you really need to change the internals. Your setup is good and safe for the road.
 
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Discussion Starter #10
Mind you, you could fit less aggressive cams -and verniers. It really depends on how you want your engine. Probably best to leave them with more thought.

Be interesting to see what headwork on its own does - didn't measure that unfortunately, although I am not running much higher boost now (1.75 bar peak) and the figures are quite abit higher than before. Have some graphs, will scan and post them soon.
 
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Discussion Starter #11
The reason why I'm thinking about 85.5 instead of 85 is that if I get the block honed, I might as well go for bigger pistons. I know it doesn't really make sense to do it without a bigger turbo, but in my next steps I want to tune in a way which leaves my options open for the future. Well, I might go for cams first, but the (GEMS, I think) ECU will definetely be my next step, provided my car passes the German MOT which it is finally being prepared for these days. There's about a 50/50 chance that the car will pass easily, if not it could become very expensive and time consuming.
 
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Discussion Starter #13
MichaelK...I though you were going to do the engine work your self?? Just get a kit from Tomei which are great at tuning engines for road cars....ie more torque at lower revs. They also include ECUs so you have less things to worry about...and its a hell of a lot simpler!
 
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