[mustang95 5.0]

going to put in a new 4.3 long rod stroker motor starting to save up, supersix has motors that can be built to produce 280-390 hp n/a, i have been hearing that if you wanna run a turbo setup down the road you should get a motor with lower compression to prevent engine knock. im just a little confused, i thought these strokers were built no matter what the compression to handle additional power with ease because they were fully built? I would like to get a motor with as much hp n/a and then go for a turbo kit perferably from tma, but what compression ratio would be the best for a turbo setup down the road or does it even matter?

[9986paulk]

yeah, compression still matters even if it is built. it would be more likely to knock with higher compression, which can and will destroy any motor over time, built or not. If im not mistaken, I think ~8.5:1 would be better. I think stock is 9.5. You could even stick with a stockish CR and run enough boost that would make great power.

[JTs03v6]

9.5 or less with fi imo.
I would contact tom and speak with him about your future plans.

[stephen]

If you add a turbocharger that in effect increases compression ratio. e.g. if you run 10 psi of boost then you have a larger effective compression ratio of (14.7 +10)/14.7 =1.68. If you have an 8.5:1 compression ratio that translates to ~14.3 compression ratio with the boast, which requires a very high octane gasoline or methanol as a fuel. This is just to give you an idea. You should check with people who have actually run turbochargers to see what their experience is.

[mustang95 5.0]

Originally Posted by 9986paulk yeah, compression still matters even if it is built. it would be more likely to knock with higher compression, which can and will destroy any motor over time, built or not. If im not mistaken, I think ~8.5:1 would be better. I think stock is 9.5. You could even stick with a stockish CR and run enough boost that would make great power.

So before getting the motor i should make sure the compression ratio is between 8:5:1 and 9.5 to be on the safe side running f/i

[mustang95 5.0]

Originally Posted by JTs03v6 9.5 or less with fi imo. I would contact tom and speak with him about your future plans.

Ya i plan on talking to Tom and a couple of other places to get a feel for what is the best CR t go with for f/i

[mustang95 5.0]

Originally Posted by stephen If you add a turbocharger that in effect increases compression ratio. e.g. if you run 10 psi of boost then you have a larger effective compression ratio of (14.7 +10)/14.7 =1.68. If you have an 8.5:1 compression ratio that translates to ~14.3 compression ratio with the boast, which requires a very high octane gasoline or methanol as a fuel. This is just to give you an idea. You should check with people who have actually run turbochargers to see what their experience is.

thanks very informative, trying to wrap my head around the mechanics of f/i been working on cars for a while, nothing to drastic replace and fix starting to dip my hands into some modding now, but f/i and compression have to figure it out, i figure this is the best place to ask alot of helpful and knowledgible people on these forms.