Power gains advice?

[Louis Nitschke]

My VR4 has been running 200kw at the wheels for a few years now with standard internals/ cams on E85 running round 20psi. A compression test the other day showed around 95-100psi across all cylinders on WOT, not exactly great.
At the moment I'm saving to put in a mechanical diff and 4 bolt shafts, and in light of this compression test after that I figured I might as well give the motor a rebuild, it has done 170k clicks after all.
Im thinking of aiming for 250ish kw at the wheels on E85, and at least 200kw on 98RON with, wait for it, a standard motor.
Can anyone give me some advice on if this is possible? What are 6 bolt 4G63s like at making this sort of power. Would bringing the engines compression back to standard allow more power to be made? The car has most other things sorted for bigger power:
-ECM Link
-910cc injectors
-walbro in tank
-3" turbo back with cat and muffler
- big 16G
-jap spec intercooler
-ARP head studs
-multilayer metal headgasket
would it be possible to even get 220kw maybe on completely stock internals with E85? Or will I need more exhaust/turbo flow?
My initial plan (if the bores don't require machining, otherwise this plan is going out the window) is new set of wiseco rings, race bearings, ARP mains and rod bolts, everything else internally left standard. Might also go for wideband O2 sensor for extra tuning ability. Has anyone been done this path before, obviously id rather not fork out for forged stuff yet if i can avoid it. Also interested in seeing how much a stock 6 bolt will make, as SR20 internals with the right mods will hold near 300kw.

 

[4piknup]

You should do a wet compression test with oil on the bores, not in the piston crown and same amount of oil each time. or a leakdown test to see how much of the low compression is rings.
Your only chasing 10% more so id say up the boost, once you are happy. I think the stateside guys say that the 7 bolts will handle 500hp, I think thats 250rwkw. A 6bolt wouldnt be 10% weaker, would it.

 

[brisvr4]

Mine has done about 270000 on totally stock internals and makes considerably more than 250kw at the wheels.
Its enough for 132mph traps in the 1/4.
Mind you mine still has about 145psi across the board too.
It's all in the tune and fuel. Safe = keep it alive!

 

[CLuTZ]

You should be able to run 25psi before the turbo is out of it's efficiency range. Unless the wastegate has been ported or you're running an external gate you will probably get boost creep- especially if you are running a 3" dump pipe.

What Walbro do you have? If it's just a 255l/hr I would re-wire it to be on the safe side. Also, what cooler piping are you running? Still running the factory inlets and outlets on your intercooler?

I would think you would need cams to get to 250kw. While you're there i'd find some EVO 7-8 valve springs to put in (I paid $100 for a set, delivered) and replace the lifters and valve stem seals too.

 

[Louis Nitschke]

Mine has done about 270000 on totally stock internals and makes considerably more than 250kw at the wheels.
Its enough for 132mph traps in the 1/4.
Mind you mine still has about 145psi across the board too.
It's all in the tune and fuel. Safe = keep it alive!

Sounds promising, so there may be hope! What engine mods do you have, and what drivetrain have you got to handle that power? One thing I'm keen to do is some 1/4 mile action as well

You should do a wet compression test with oil on the bores, not in the piston crown and same amount of oil each time. or a leakdown test to see how much of the low compression is rings.
Your only chasing 10% more so id say up the boost, once you are happy. I think the stateside guys say that the 7 bolts will handle 500hp, I think thats 250rwkw. A 6bolt wouldnt be 10% weaker, would it.

Ill have to look at doing one next time I'm at my dads, car is stored there at the moment.

You should be able to run 25psi before the turbo is out of it's efficiency range. Unless the wastegate has been ported or you're running an external gate you will probably get boost creep- especially if you are running a 3" dump pipe.

What Walbro do you have? If it's just a 255l/hr I would re-wire it to be on the safe side. Also, what cooler piping are you running? Still running the factory inlets and outlets on your intercooler?

I would think you would need cams to get to 250kw. While you're there i'd find some EVO 7-8 valve springs to put in (I paid $100 for a set, delivered) and replace the lifters and valve stem seals too.

The most I've seen that turbo run is 28psi (boost controller screwed up its settings) and by hell that car boogied! Fairly sure its a 255l, what do you mean by rewire it? Yeah intercooler and piping is stock size, converted to mild steel though. Are 7-8 springs stronger? The head has had a rebuild before.

 

[4piknup]

Boost creep on e85 is what gets the usa guys the 1/4 records for stock frame turbos.

But they are funny. I had a ride in a r35 skyline and the yanks say they are real nice to drive at 1000awhp

 

[CLuTZ]

Fairly sure its a 255l, what do you mean by rewire it? Yeah intercooler and piping is stock size, converted to mild steel though. Are 7-8 springs stronger? The head has had a rebuild before.

More flow from your pump. Doing a re-wire means you will see a constant 12-13volts at the pump rather than 10-11volts. There's plenty of write ups and kits available online.

I would look at upgrading your intercooler and cold side piping at least. I'm impressed you're making 200kw with the factory intercooler to be honest!

The EVO valve springs and retainers are a lot lighter than the factory stuff. They are a good upgrade that won't break the bank.

 

[EV0300]

But they are funny. I had a ride in a r35 skyline and the yanks say they are real nice to drive at 1000awhp

https://www.youtube.com/watch?v=pcHumlKI5EE

must be really nice to drive at 2000awhp then

 

[evo-gsr]

That AMS R35 is a weapon ! Sounds soooo good.