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Increase in GTR Compression Ratio?

Sneaker

By Sneaker,
in Engines & Forced Induction

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Sneaker Enthusiast

Sneaker

Posted
Posted

I am considering uping the compression ratio on my GTR in the hunt for more accross the board grunt. I am not after peak power figures, I just want a more overall drivable package.

I am in the process of doing extensive exhaust mods and eventually be running a max boost of 1BAR boost with a retune. This alone should give about 300kW. By upping the c/r I shouldn't have to change turbos, injectors or computer whilst increasing torque accross the board.

I was thinking of about 8.7:1 to about 9.0:1. I realise that my maximum boost I can run will be lower but I want to keep the standard turbos, and only run 1BAR anyway.

What do you guys think? I know it goes against traditional thinking of lowering c/r to up the boost, but I think this will be a better result for my driving requirements.

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Gav Mentor

Gav

Posted
Posted

I can see your reasoning, but will of course be more prone to detonation if the ignition map is left unchanged.

I guess alot has to do with what ECU are you using, how well it's tuned and other factors such as consistent fuel quality and charge air temp.

666DAN Grand Master

666DAN

Posted
Posted

High-compression is your friend, off-boost response is a lot friendlier and the turbo (in your case turbos) spool very quickly.

Tuning *may* be a tad more difficult, but I'd say at 9:1 you'll have no trouble...there are lots of GTS-t running more than 1 Bar and they've got 9:1 from factory.

Sydneykid Grand Master

Sydneykid

Posted
Posted
I am considering uping the compression ratio on my GTR in the hunt for more accross the board grunt. I am not after peak power figures, I just want a more overall drivable package.  

I am in the process of doing extensive exhaust mods and eventually be running a max boost of 1BAR boost with a retune. This alone should give about 300kW. By upping the c/r I shouldn't have to change turbos, injectors or computer whilst increasing torque accross the board.

I was thinking of about 8.7:1 to about 9.0:1. I realise that my maximum boost I can run will be lower but I want to keep the standard turbos, and only run 1BAR anyway.

What do you guys think? I know it goes against traditional thinking of lowering c/r to up the boost, but I think this will be a better result for my driving requirements.

We run 9 to 1 in lots of RB engines, but they are built to have that compression ratio via piston slection, block deck height and combustion chamber volume. So the real question is, how do you intend to increase the compression ratio?:P

Sneaker Enthusiast

Sneaker

Posted
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Posted

Any change in compression would always mean a retune. If I kept the 1BAR boost pressure, i would hang on to the standard computer as they are pretty good, and I am not running larger turbos, injectors, air flow metres, etc...

I would probably change the pistons if I was looking at going as far as 9.0:1+. But could a lower compression of say 8.7:1 or 8.8:1 be achieved with a thinner metal head gasket?

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