I'm currently running 8.5-9#. I am using the biggest pulley I got with the P600b. I have a smaller one(12# maybe??). I was wondering how much of a tune change would be necessary to put it on.

I've been thinking that I could make more average power using a smaller pulley but shifting sooner so as to not go past 9#. I haven't done any calculations on whether or not I will. Just been curious about whether or not I could drop some ets.

What do you guys think?

 

I don't know much about forced induction but we've tuned a couple turbo LS1 cars. I am assuming you have had a tune with the 8.5-9# and that you are still using a MAF. You should be fine as long as your MAF does not max out. I don't have the calculation handy to figure out what our MAFs should theoretically flow, so I can't tell you if your MAF will max.

What you should do is take it back to the dyno with the 12# pulley on it, get your air-fuel readings making the first pull to about 4000RPM. Do the 2nd pull to about 5500RPM if your first pull looks safe. If the Air fuel still looks good up to 5500, do a full pull for your last run and make sure your air fuel doesn't start to go lean up top. You may be out $80 and some gas money, but that's a heck of alot cheaper than a new bottom end.
Another factor is your spark...you may need another degree or two of spark retard to keep from detonating (if spark is already tuned conservatively, you'll be fine.)

 

Thanks for the input. I probably won't do it since I've been pushing my luck with this car already. I was just thinking one day and theorizing. Never know though, I might try it out.

Thanks again, Mike.