i know this has been covered in the past i have searched and i havent been able 2 come to any reasonable conclusion as to what is safe. i have basic mods, cams, fmic, pipe set, intake, turbo back exhaust, mbc.

i want to order a full gt35r kit or 3071r/50 trimm something along the line of that but i dont want to have to get any internals changed, what is safe and at what boost?

i mean will it be safe to run a big turbo say gt35r at 22psi running safely on the stock block just as its fine running 22psi on stock turbo??? or does it not work that way?

because obviously even at low boost such as 22psi a 35r will make say 450awhp??? is that safe. so then once i do have my motor and head built i can turn boost upto say 30psi and get much higher numbers such as 600awhp?
that way saves me from buying two turbo kits.

i am currently running ecutek but with new turbo will change to either power fc, aem or autronics.

i will be running on 98 unleaded (uk) no alky, meth or nos.

any advice or opinions would be muchly appriciated

thanks

 

Boost levels are not comparable between turbos - they all flow different CFM, so 22psi on a GT35 is far far more air, more fuel required, more stress on the engine, etc than a stock turbo.

Boost levels are not what you worry about - that is not the limitation. It's the actual power level you reach. On the stock motor, we can go to 500-550whp before we start to worry, but that's on the edge of safety at 550 and beyond. It would be a waste to pay all the money for a GT35 only to run 22psi, though, because it's made to run 30psi and beyond.

I'm assuming your 98 in the UK is equivalent to our 93, which means you won't be able to run much boost at all and therefore have a very laggy and minimally powerful big turbo. If you want big power all the time with decent spoolup, you need to run race gas 24/7 or meth/alky. Being averse to these when getting a big turbo is sort of oxymoronic (no, that's not an insult).

 

ok i see what u mean, im thinking of going for manley rods and wiesco pistons on stock crank, how would a gt35r running say 30psi be with a built 2 litre block? street drive ok? what about my gearbox and transfer case would i need to change/alter these?

 

Why don't want to run mentahol???You could have failsave,what wrong??Boost it to 30~33psi and ready to recive a 520+whp dynosheet.For the gearbox and TC question,you could use stock one if you don't launch.Chirs(903whp) still use the stock trans with Exedy Clutch.

 

You think our motors can handle 500whp and be reliable for daily drivers?

 

Why not? check the sig .

 

Strictly speaking, this is not correct. A GT35R (or any other bigger-than-stock turbo) will not be able to squeeze more air into the stock IC piping at the same boost level. The only reason a larger turbo will push more air is because it does not heat up the incoming air as much as a smaller turbo will (less RPM required on the big turbo to push the same mass of air), resulting in cooler air intake temps. Cooler air = more mass, but the difference, while noticeable, is not that big.

As far as a choice of turbo for an Evo with a stock block and stock valvetrain, here's how I look at it:

- reliability? ... IMO you throw that out of the window when you start to mod
- stock valvetrain = limit of ~7800 RPM
- stock bottom end = limit of ~500whp

Given those limitations, you now need to ask yourself with how much turbo lag you are willing to live with. The three turbos you mentioned (3071/50trim/35r) all will make similar peak HP numbers on pump gas, but use very different torque curves to get that number.

The 3071 and 50trim can give you full spool as early as 3600 RPM in 3rd gear (largely dependent on your engine VE; e.g. cams, cam timing, intake manifold, IC, IC piping, etc.). The 3071 will fall off earlier in the upper RPMs than the 50 trim, but with the stock redline it's barely noticeable. With either turbo you will have a useable powerband of ~ 4200 RPM.

The 35R might give you full spool by about 4200 RPM in third gear, again depending on the VE of your engine. On pump gas it will fall off slightly less in the upper RPM than the 50 trim. Usable powerband on a stock block with the 35r is ~3600 RPM.

For a street car I would go with an AMS spec 50 trim. I ran a 3071 on my AMS turbo kit for a while and ended up switching to the 50 trim because I was not 100% satisfied with the 3071. On my car the 50 trim has turned out to be better in all aspects vs. the 3071 - spools earlier, better topend power, no surge.

Personally I don't think I could live with the bigger lag of the 35r...

l8r)

 

From a purely boost pressure point of view, generally speaking the two areas of concern in terms of excessive boost pressure are:

1. Head lift
2. Piston ring failure
3. Cylinder wall failure

#2 and #3 isn't so much of an issue on the EVO. #2 I would say up to 40psi is ok (although this is just a guess, we don't run 40psi on stock pistons/rings), and #3 probably a bit more due to the closed block.

#1 is a problem on the 4G63, you can minimize this problem with a good head gasket and ARP head studs.

But as many have already said in this thread, boost pressure does not directly equal power.

The 35R and the 3071 is two totally different animals. If you're staying with the 3071, your stock block is fine, if you're going to run the GT35R on anything less than a dedicated DRAG / C16 gas car, I'd go with a 2.3 stroker. We have a fully built 2.3 stroker in stock, forged piston, forged rods, balanced crank, etc. With a 35R I'd invest in some serious headwork as well.

Hope that helps,

Gary
Gruppe-S

 

Lol