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Discussion Starter · #1 ·
Hey guys ive been looking into alot of different setups on different cars and seem to see some running high compression. My question is is there an advantage running on higher compression on our motors vs a stock tt compression? Just looking for some views and input... advantages/disadvantages??
Now im no expert but wouldnt running higher compression make the same power gains running lower boost than a stock compression with higher boost or have i totaly got it wrong here? :scratch:
 

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Higher comp engines are better to drive off boost, and helps setups which would be kind of laggy.

It's not something really tried in the UK, however more US guys are running higher comp's, and it seems to be common on BIG turbo setup blocks as well...
 

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You have it right, but it will only work until you hit the engine's detonation resistance limits...which depend on the design of the head and combustion chamber along with timing. The higher the CR the more torque you will make at lower boost levels, but remember the higher CR the higher octane fuel you will have to use at all times.

The convenience of lower compression/higher boost is if you are in a bind stranded in the boonies and can only find 89 or 87 octane fuel, you can just keep the boost down or not even hit boost, and be alright. If you have a higher CR, you would have to really baby the motor regardless of boost...depending on how high your CR is.
 

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Discussion Starter · #4 ·
some very helpful info here, thanks. Over here we dont see much less than 95 octane so it shouldnt realy be an issue fueling but i can see it being a bit more thirsty and subject to higher stresses, even so i think id consider it just to see what sort of difference it realy makes. Im assuming off boost it should drive like an NA?
 

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keep in mind the different octane ratings too... i've read that it's common for europena pump gas octane to reflect RON, unlike here in the US where pump gas octane is R+M/2 (the average octane rating between RON and MON), so that effectively your 95 may be equivalent to our 91 or so... just what i've read.

higher SCR's generally require a more detonation resistant fuel... in fact, most seem to consider them 'race gas only'.

craig
 

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a big factor is your turbo setup and how well everything is matched.

i have had both and they drive a bit differently. with a high CP turboed motor you will feel the motor pull hard right off of vac. with hardly any boost. its really fun to drive as all your power in your lower rpm range. but, it will leave you wanting more once the wastegate opens.

with the low CP setup of course you have some lag involved, but it also hits all at once just at a higher PSI/RPM usually.

it all depends on what kinda driving/setup you are looking for. i think a high CP motor with twins on it would be sick.

if look up numbers though. your going to be able to make more power on a low comp. motor.
 
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