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9.2:1 vs 8.1:1 compression ratio

03-28-2006, 12:43 PM
:banghead: hi im in the process of purchsing internals for my d16a sohc vtec. im trying to determine what would be better to run 9.2:1 or 8.1:1 for my turbo. im going to be running eagle h beam rods. i understand higher compression builds up more power but can lead to engine damage and handles less boost. and vise versa for low compression. but how much boost do i have to run to get the same hp as runing 9.2:1 with a 8.1:1. and how much safer is it to run higher boost vs high compresssion. also i will be upgrading to alchol injection this should help with any detination:smokin:

03-28-2006, 04:27 PM
The only people I know who go as low as 8:1 compression are people who plan on making a lot of power and boosting a lot (30-40psi with a big turbo), take that as you will. With a good engine management system and a good tune, 9.2:1 compression pistons will be more than low enough to have reliability to it. With the Eagle rods, I'm also assuming you're not looking for a ton of power; so I'd definently go with the 9.2:1. Also if you're using the turbo in your signature, higher compression will work best as well.

I know these aren't the ratios you're asking about, but here's a good idea of the power differences between both setups: http://forums.evans-tuning.com/viewtopic.php?t=1612 (possibly a 15whp difference).

03-28-2006, 11:06 PM
i vote 9.2

03-29-2006, 02:29 AM
thanx for the info, i am now going to go with 9.2:1 with about 10psi:evillol: . this should be safe and should still have some pep.but i am also sad to say,:frown: my motor finally went with 18,002 turbo mile @ 218002. but it still ran enough to get me back home no towing required. :)

03-29-2006, 12:49 PM
if you are building with forged internals i would run 15 psi with a bigger turbo

03-31-2006, 08:29 AM
what kind of power are you looking to make?? I would go w/ the 9.2 reguardless, but im just wondering. You were asking about DSM injectors and those are going to poop out on you around 300whp. If you're using an AFC system to tune it, you're never going to get 250whp out of those injectors. What are you using to tune, what are your goals and what is your budget?

I'm curious!

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