Hey,
I race in a road racing club, where the category rules do not permit me to raise boost above 1.2bar. I have seen other cars that have installed higher compression pistons and stronger rods to make more power without raising boost. My question is, what brand pistons and of what compression should I purchase, also what brand of rods do you recomend? Also, I am running a RalliArt sports ECU and would like to know if it would be able to handle the engine's timing and fue demands with higher compression. I was told that raising compression is just like raising boost so I imagine that the ECU should work fine. I have also already installed an HKS EVC to prevent boost spikes over 1.2 from getting me disqualified. Also remember I live in PR, so if I got a stand alone ECU if it was anything but a HALTECH there would be no one but myself to tune it, and I don't have enough know how. Anyway, any suggestions are greatly appreciated... Thanks in advance for your help.
BTW, I have already purchased, but not installed a set of HKS 262 cams, HKS adjustable cam sprokets, HKS head gasket, stiffer valve springs, and a set of ARP connecting rod bolts.

Sincerely,
Julian Gutierrez

 

The parts you have sound good and will make a difference and believe me finding someone good to map your ECU is not only a problem in Puerto Rico! I don't know what compressions you should go for but makes of pistons are: Omega (UK) JE (US, www.jepistons.com) and conrods are Arrow (UK) and there are a lot of others that don't come to my mind right now. Omega and Arrow have standard products for the Evo, with different compressions. You said rightly that after you change the compression you'll have to alter timing etc. so you will really need a remappable ECU. Also think about a bigger intercooler and automatic waterspray to raise power without raising boost. There will only be marginal increases through those measures but they will come in handy when you add a new turbo. Now, a new turbo will be the ultimate increase in power without raising boost due to higher flowrates.

 

If you're limited to 1.2 bar then don't go for a bigger turbo as the standard one will flow enough air for ~380hp and you'll loose mid range with a bigger turbo. At the same outlet pressure any 2 turbos will flow the same mass flow of air as the restriction to flow is in the engine not the turbo (provided you haven't exceeded what the turbo is capable of).

Fitting a thinner head gasket or skimming the head is the easy way to increase compression ratio. Just watch out for valve clearance. I didn't think about it on a Manta that I had taken 0.6mm off the head and fitted a long duration cam on and bent a valve. May not be so much of a problem with a 4 valve head but worth checking. New pistons are expensive and may not really be required.

Are you allowed water injection or very high octane fuel? If not then with the high ambient tempertaure in PR you may struggle to get much improvement from raising the CR (the ecu will detect knock and back off timing).

I would certainly recommend a programmable ECU. Go for one that can be setup by yourself. Evo link or GEMS are the obvious ones. This would allow you to setup the ecu properly for your engine and you could then tweak it for the conditions at each race.

 

Errr, Oli, the standard one will flow enough for 380 bhp but not at 1,2 bar, that'll be closer to 1,6. Bigger turbos will flow more at the same pressure, just ask Lightspeed. You just have to visualize a pipe, the pressure is at what rate the air comes out of it. Now if you increase the diameter with the same energy put into generating pressure you'll have the same flow, but with less pressure. Now if you increase the diameter and keep the same pressure, you'll have a larger amount of airflow. That's what bigger turbos do and that's why really big turbos can put out around 400bhp at 1,2 bar in an Evo.

 

And Claudius, you'll find that the pistons and conrods that Jun and Tomei use are not made by them but someone like JE and Omega. In fact I'm quite sure Jun use Omega.

 

Hmmmm, Mk you're right (how it hurts to have to say that)......having given this some more thought there may be some benefit to a larger turbo. Must remember to get brain in gear before web dumping.

The reason is as follows:-

Basically the boost in the inlet manifold is controlled via the ECU by the waste gate which controls turbo speed, in this case to deliver 1.2bar. If say a larger compressor (inlet) wheel is fitted the waste gate will sit further open to limit the speed at which the turbo spins. This will reduce back pressure and allow the engine to flow more air (=more power) at the same boost. A larger impeller (exhaust) wheel will again allow the waste gate to open further reducing backpressure.

However against this the larger turbo will have increased lag, reduce mid range torque (as it takes more exhaust gas to spin up properly) and may suffer from surge.

Claudius, i like the look of the Jun 2.2l kit. cunning those Jun chaps to get 6 pistons into 4 cylinders

Julian, as Claudius says tell us the rules, we'll be able to advise you on how to spend all your hard earned cash

 

It's all good, as you say here in America, oli !
Well spotted with the cylinders also, I think you check your sources Claude, hehehehe

 

Okay guys, sorry for the lack of info. on my rules.
I am allowed to modify the turbo without changing the stock housing. I can change the exhaust manifold. The HKS gasket I bought is the 1mm one. I can bore larger cylinders but not increase stroke. I can port and polish the head, engine management is open. The Tomei rod set looks great!!.... Anyway, thanks for ypur help.

Julian Gutierrez

 

Do you already have titanium internals for your turbo? If that's the case I think that's as far as you can go then, cause I don't think there's a rebuilding set for the Evo turbos, but I might be wrong. Port and polish the head, get larger bore pistons (85,5mm) and an exhaust manifold. These mods won't bring very big gains, but coupled with a new ECU you could be looking at anything from 10-40bhp gains depending on how your engine is set up at the moment. This is estimate is on the assumption that you have already changed the intake, have aluminium piping for the turbo/intercooler and a new exhaust without cat.

 

I assume the turbo on my car is the Titanium ball-bearing one since mine is an RS model that is suposed to come with that one. I am running a straight through exhaust from the turbo exiting out the right side of the car in front of the rear wheel. I mean 3 inch down-pipe, and 3 inch exhaust without cat. Right now since my engine already has 2 seasons of racing I am planning a complete rebuild. I am considering high compression forged pistons, stronger rods, maybe porting the head, balancing the whole crankshaft assembly. The thing is that I want to run this setup with the factory ecu, relying on the boost controler to prevent the 1.2 spike I told you about. Do you think the ECU is up to the task. Any way, thanks for the sugestions.

Julian Gutierrez

 

Hey Claudius,

Could you give me an email address or web site to contact Bozz Speed.

Thanks,
Julian