i have a d17a2 and its boosted on 6.5lbs k-pro precision turbo im gonna build a bottom end and all the pistons i find are all over the place in terms of compression ratio what end of the spectrum should i go and what is better in terms of pros and cons with a 8.8:1 or a 10.0:1 ratios

 

You should be looking in to effective compression ratio, what cams are you using? Also octane of gasoline you'll be using?

 

ill be running stage 2 crower turbo cam , 93o , stock is 9.0:1 , if i get 8.8:1 how will this effect the motor in the end is it more or less power , can i run a higher boost with it or buy the 10:1 and run lower boost

 

10:1

/thread

 

10:1 is the new 9:1
There's really no reason to go lower than 10:1

 

You can also just raise the compression a bit . With flat face valves . I'm pretty sure decking the block and resurfacing the head will at least bring you to stock. Not 100% sure but I'm pretty sure someone will chime in. Myself I just bought some 10.6:1 comp pistons for my girlfriend build.

 

If you have 8.8 cr, you will be able to tun more boost, but your car will run like it has no soul or purpose in life until you hit boost rpms. 10:1 cr you can use less boost, and make the same amount of hp as the low compression, but you cant run the same psi as a low compression motor. Your car will run like a champ with high compression before boost! And itll have a nice smooth transition going into boost rpms. But with high cp and boost, your tuner has less room for error.

 

This is basically what I've always been told.

1. Higher compression performs better outside of boost.
2. Higher compression takes less boost to make the same power
3. Higher compression is less forgiving for the tuner

With that said, I still run 10.2:1 or whatever the factory compression of the B16A was.

 

idk why people still run "turbo" cams. it seems to me that they are always outperformed by a mild n/a cam. anyhow go with the higher of the 2 compression ratios. anywhere around 10:1 is fine especially if u do have an aftermarket cam

 

I am at a tad bit over 11:1. My next build will be the same way.

 

Because very few "turbo cams" were specifically made for B-series. Depending upon the turbocharger and its use for application, a good "turbo cam" can do quite well over a mild NA cam without having to do any work on the cam gears (which most NA users are used to anyway.)

Trust me, I was more of an NA camshaft person myself. Then I got specifically developed Turbocamshafts, and won't look back.

 

i got the crower stage 2 cam for the d17a2 em2 , i like the cam it makes real good power and vtec power is smooth and you can tell vtech kicks in , this is mostly a daily for me but with what i got in it i want at least 300hp at the wheel if i hit 275 and it holds ill be happy

 

Co-sign!
I'm looking into build a new motor with 10.5.1 but I wouldn't mind 10.1
My current gsr has cp 9.1 which work great but from the new discovery 10.1 or 10.5 is more tasty!

 

 

I'm pretty sure decking the block and resurfacing the head will at least bring you to stock.

 

Turbo cams when designed correctly for the application do very well. High compresssion does very well too. Im running 10.7 pistons and after decking etc im about 11:1 running GSC turbo camsin a B series. Putting down 707/444 at 19 pounds of boost with a precision 6266 Running ethanol

 

Wow! That's a lot of power for that amount of boost. I can imagine what it'll make if you start boosting in the 30psi range.

 

it wouldn't make anymore power, the 6266 compressor wheel is tapped out at that point, he might be able to squeeze 715-720 but that is that absolute at the choke point limit of the compressor wheel

 

Actually wantboost the 62 wheel will make more power. It's the 6262 combo that is tapped out around 750 due to the smaller turbine wheel. It's not Going to gain power much past 25 psi but it will make around 800. I'm not stuck on the dyno numbers as it won't go back on the dyno even once we turn up the boost but mph and vehicle weight the car is currently
At 741whp. The third pass I made the boost went up to 24-25 pounds and it picked up quite a bit in acceleration.

The engine is going to max out the turbo earlier though because it's apparently running super efficient. My buddy just made 607 at 30 pounds with the same turbo just smaller turbine housing which if he swapped to the .82 would pick up 20-30whp

 

The 66 wheel is what's making you have WAY more power. The 62 wheel is the smaller of the two. You're efficient, because you're using a larger exhaust wheel in a smaller volute... I've utilized this formula a lot.