JWT Tunes: what's the difference in the tune between 9:1 and 9.5:1 pistons?

[MarkEmark]

I recently purchased a JWT ECU 50 lb/Cobra MAFS program (got it for $330, a damn good deal) mostly because I never see these programs being sold at a reasonable price for an OBD II manual transmission 240sx, so I wanted to jump on it even though I won't be installing it for at least another month or so. And if I sent my current JWT out for a re-tune, I wouldn't be able to have my car for like 6 weeks...Anyway, I completely forgot that my new engine has 9:1 wiseco's in it, not the 9.5:1 stock pistons which this program was made for.

So here's my question: I know JWT takes into account the compression ratio when they're tuning their ECU's, tuning the ECUs for use with lower CRs more aggressively than the ones for use with higher CRS. But WHAT exactly do they do differently? Do they just make the timing a little bit more aggressive (in which case all I need to do is advance my timing at the distributor), or do they also make the fuel maps more aggressive? What about both?

I just don't want to end up with an even MORE notoriously conservative tune than I need to have. If all that they do is make the timing a little more aggressive that doesn't bother me....

Does anyone know for certain?

[turbo90]

I'd guess the timing is a just little steeper, but yes off boost drivability will suck even more than normal (no experience, just smarts). perhaps with 17psi you will want a ton of retard? try to find a scan tool and see what it's doing during cruise/boost/smoking mustangs ect??Is the only way to fix this (advance timing) to have it sent back to jwt??

[klattr1]

i'll tell you this, I have a few friends that have datalogged the timing for the 50lb/cobra mafs stock compression program and have gotten 14 deg. timing WOT around 1 bar.

on my old 72lb/cobra mafs program (8.5:1) as well as several other people, it would yield 14-15 deg timing WOT around 1 bar.

so whats the difference? not much at all.

how did i fix that? put in a lil race gas and bump the base 3-4 deg.

[WDRacing]

There shouldn't be a difference sine you guys were running the same amount of boost. The timing should be the same all the way accross the board on his tunes assuming hte only difference is injector sizes. The fuel mapping will be all different, but timing will stay consistant with load.

14-15 degree's at WOT on 1-Bar is a good place to start IMO.

[MarkEmark]

I spoke with a technician (but not an engineer) at JWT and he said that there's really not much of a difference at all between the 9.5:1 and the 9:1 tune, but that there WOULD be a differrence between the 9.5:1 and the 8.5:1 tune. He said the only difference that there would be between the 9.5 and the 9 tune is that the 9.5 would have a little bit more aggressive timing but that can all be fixed by advancing it at the distributor....

[rn240sx]

I recently purchased a JWT ECU 50 lb/Cobra MAFS program (got it for $330, a damn good deal) mostly because I never see these programs being sold at a reasonable price for an OBD II manual transmission 240sx, so I wanted to jump on it even though I won't be installing it for at least another month or so. And if I sent my current JWT out for a re-tune, I wouldn't be able to have my car for like 6 weeks...Anyway, I completely forgot that my new engine has 9:1 wiseco's in it, not the 9.5:1 stock pistons which this program was made for.

So here's my question: I know JWT takes into account the compression ratio when they're tuning their ECU's, tuning the ECUs for use with lower CRs more aggressively than the ones for use with higher CRS. But WHAT exactly do they do differently? Do they just make the timing a little bit more aggressive (in which case all I need to do is advance my timing at the distributor), or do they also make the fuel maps more aggressive? What about both?

I just don't want to end up with an even MORE notoriously conservative tune than I need to have. If all that they do is make the timing a little more aggressive that doesn't bother me....

Does anyone know for certain?

jim wolf does NOT tune the ecu for compression...!!! call them and ask and you'll see, been there done that..