tvs and 10 to 1 compression

[skipper630]

What kind of performance loss should I expect to see when going from 11 to 1 stock pistons to 10 to 1 Manley forged pistons? I don't have a good apples to apples comparison but my car doesn't rip like it did before.

What parameters are changed in regards to tuning for 10 to 1? I purchased a new tune from a different tuner for the 10 to 1 but I am curious if I could try one of my older 11 to 1 tunes without causing damage.

I have a 2011 Coyote with Roush TVS, JLT CAI, 47mm injectors, and 82mm pulley. 91 octane is all that is available at the pumps in my area.

Thanks in advance.

 

[Scott8583]

Your going the wrong way! These little cube motors need compression. I'd say your going to need at least a 79mm pulley to make up for the torque loss. Assuming your on aftermarket pistons, you actually need more boost then that (+ bigger injectors). A 82mm would have been fine on a stock 11:1 motor.

 

[Mach828]

Yep. Lower compression, less pressure in the cylinder, less power. You need to get it back by running more timing or throwing more boost at it.

Might also be that the new tune is more conservative. If your old tune was safe, and all you did was change the compression ratio, you can run the old tune.

 

[Gpcalero]

If you are running the same pulley as before then you will have lost power as your effective overall compression with the boost is now less. Lowering your compression ratio isn't really a bad thing. You are able to push more boost to make up for the compression loss and have easier tuning/get away with more on the fuel you use.

Now that your motor is built, I would install a 72mm pulley, invest in ID1000's (you'll need the bigger injectors), and install a return style fuel system or a BAP at least. With that setup you should 'rip' even more than it did before.

I wouldn't mess around with putting the old tune on it however.

 

[skipper630]

Thanks for the input. I will try a couple of older tunes that I have and think about/save $ for the other changes as a winter project.

 

[beefcake]

we ran 9:1 for years on "fuel" and ran 9.0's consistently

10:1 is what we have been running with e85