what is the biggest comp ratio you would go on a 4G63 vr4 engine on a smaller turbo?

[Dasithkg]

hi,

I've seen pistons 0n 7.8:1 and 8.1:1 and 9.1:1 for 4G63, could it go any higher with out damaging anything 0n a fully built motor with a stock smaller turbo?


Cheerz,
Dasith

 

[BMGTZ]

hi,

I've seen pistons 0n 7.8:1 and 8.1:1 and 9.1:1 for 4G63, could it go any higher with out damaging anything 0n a fully built motor with a stock smaller turbo?


Cheerz,
Dasith

my 2 cents ......if utilising a quality after markey ecu. just about any comp ratio withing reason can have a suitable tune.....power out puts will vary but it depend what you intended use for the engine is. As a rule of thumb....higher comp ratio will have better response and pull off the bottom of the rev range.

having said this....I am builging my stoker enginge at 9:1. I am only going to use a FP68HTA so dont expect huge horse power from it. but I do want loads of torque in the lower revs.....2000/3500

 

[JC evo1]

Keep it around 8.5 - 9:1 if you intend to run on PULP. Sure you could go higher but it restricts the amount of boost you can run, psi makes more power than small SCR changes.

 

[Dasithkg]

what if we introduce E85 and 272 cams to the equation? what would happen then?

E85 would allow higher compression and longer duration cams would reduce the dynamic compression right?

 

[CLuTZ]

Who are you getting to tune your car once it's done? That's the most important question

 

[Dasithkg]

just trying to educate myseft mate! I find it Much better to ask questions and do alot of research than just do whatever i see 0n the net!

 

[blackvr]

Our gravel rally Gp A VR4 with a 34 mm restrictor is running 8.5 : 1 cr at the moment on E85, stock management and an ECMLink chip. I am seeing around 190kw at wheels at a peak 23 psi on a TD05 16G.

The problem is I cant introduce any form of knock , no matter what timing I screw into it ( the torque just drops !) . So for the coming season I am assembling a new bottom end with NA pistons .. approx 10.0:1 CR.
It will knock a little I am expecting, but that should be remedied from pulling some spark advance out. I am now expecting it go from a torque monster into a torque Godzilla , with very good response from no revs. This is exactly what a rally engine needs ! I will keep you posted on the tuning results in the next few weeks...

Mike

 

[JayRome]

Our gravel rally Gp A VR4 with a 34 mm restrictor is running 8.5 : 1 cr at the moment on E85, stock management and an ECMLink chip. I am seeing around 190kw at wheels at a peak 23 psi on a TD05 16G.

The problem is I cant introduce any form of knock , no matter what timing I screw into it ( the torque just drops !) . So for the coming season I am assembling a new bottom end with NA pistons .. approx 10.0:1 CR.
It will knock a little I am expecting, but that should be remedied from pulling some spark advance out. I am now expecting it go from a torque monster into a torque Godzilla , with very good response from no revs. This is exactly what a rally engine needs ! I will keep you posted on the tuning results in the next few weeks...

Mike

your basically building what my set up currently is, minus the restrictor. on 14psi on my na the torque is crazy on fwd...

 

[bazeng]

Jay, time to go e85 mate!

 

[Dasithkg]

Our gravel rally Gp A VR4 with a 34 mm restrictor is running 8.5 : 1 cr at the moment on E85, stock management and an ECMLink chip. I am seeing around 190kw at wheels at a peak 23 psi on a TD05 16G.

The problem is I cant introduce any form of knock , no matter what timing I screw into it ( the torque just drops !) . So for the coming season I am assembling a new bottom end with NA pistons .. approx 10.0:1 CR.
It will knock a little I am expecting, but that should be remedied from pulling some spark advance out. I am now expecting it go from a torque monster into a torque Godzilla , with very good response from no revs. This is exactly what a rally engine needs ! I will keep you posted on the tuning results in the next few weeks...

Mike

thanx and looking forward to tuning results.....

 

[JayRome]

Jay, time to go e85 mate!

um i can not disclose whats about to happen in the next month... but i may be joining you on the E85 front.... but there are not many out lets near me which is the problem...

 

[VR-4Squid]

Our gravel rally Gp A VR4 with a 34 mm restrictor is running 8.5 : 1 cr at the moment on E85, stock management and an ECMLink chip. I am seeing around 190kw at wheels at a peak 23 psi on a TD05 16G.

Mike

Wonder what it would do without the restrictor...

I'm 7.8:1 comp, 98 octane, 264º cams, stock ecu with an s-afc and making 190kW at wheels on 15psi with a 16g. I've got a boost spike in the midrange though (peaks at 18psi) so it makes above 170kw from 4500rpm to 6500rpm.

 

[CLuTZ]

um i can not disclose whats about to happen in the next month... but i may be joining you on the E85 front.... but there are not many out lets near me which is the problem...

Caltex on the corner of Barry Rd (lol) and Hume Hwy have it bro

 

[JayRome]

Caltex on the corner of Barry Rd (lol) and Hume Hwy have it bro

yer Tim told me today too..... lol..