My car was tuned by steve Kahn with injectors 550/1300 because i thought that would be all i need at the time... It's tuned for 15psi runing single turbo...

In 3rd-4th gear i hit about 83% or less at 15psi
however in 1st i hit 100% easy

If i put in 850cc in the primary position, will i have to do anything with the fuel maps at all or will it accomodate and know what the hell it's doing? I know i'll have to change the injector size but will that be all?

Thanks.

 

Even though the PFC is suppose to interpret the changes and make adjustments for them, it is never 100% correct. Boost will be the closest but I would still re-AFR for safety.
Idle will be off the most and will definitely need retuning.

There are many threads about 850s.

 

Thanks Bud.

 

Sounds like your map is out of whack. If you reach 15 psi at 7,000 rpms in 1st or 4th gear the fuel delivered (or duty cycles) at that instant should be the same. The fuel delivered is dependent on the value of that (7,000 : 15psi) n:p cell of your fuel maps and any factor introduced by the PIM setting.

However the path to that cell is different from 1st to 4th gear. When you floor it in first gear, the turbo has less time to spool and at earlier rpms your boost level will be lower than flooring it in fourth, depending on how big your turbo is, it may not even reach 15 psi by 7,000 rpms Are you certain you are even reaching 15 psi in 1st? I suspect your map is pig rich in some p rows below 15 psi for n columns around 3,000 and up.

I have enclosed an illustration of how the path (boost curve) through the fuel cells differs between second and fourth gears. For some odd reason blue looks like purple. You’ll notice, the higher the gear the steeper the boost curve.

You could also use the map trace function on the Commander to see the boost curve change from gear to gear. The map trace will indicate which cells you are traveling through

You really need to check the fuel with a wideband for those low boost areas of your map. However, without verifying your AFRs with a wideband, you can perform a magnitude check by looking at each row of your base fuel map (recalculated) and comparing each cell with cell in the row immediately above it. The lower cell of the 2 rows should have a higher value.

You may also want to check to see if the PIM values have changed.

 

Dave you know i'm not good with the whole PFC tunning etc... The map I still have on this car is the same from the day Steve Kahn tuned it when you came by with your FD.

I never really paid attention to the first gear duty cycle because it always went too quickly. However yesterday i redlined it in 1st gear and had to stop after it so that's when i noticed it hit 100%... The boost probably wasn't exactly at 1.03 or so... i don't remember, it could be .93 or something. Which is around 13psi. I have the AF61r as you remember. It still worries me that it would hit 100% at all. I don't have the damn wideband so that's why i didn't mess with it since then. I'm affraid to lean it out at all without knowing the right AFR's.

That's why i asked the question if i just put 850's without messing with the cells would i be fine... I guess not. I still have your pics about modifying the primary rail to make them fit etc.

Amel

 

I just didn't want to see you throw in the 850s, since I don't think that will solve your problem. Whether you decide to install the 850s or not you are going to have to verify/tune your AFRs via a wideband.

Another method to determine if the lower boost cells are richer than the 15psi boost level is to perform some wot runs in 3rd at the wastegate spring level, then at 1 psi more, then 2 psi more... up until you reach 15psi...observe your duty cycles or record peak duty cycles at each boost level.

pm me if you want/need any assistance

 

Amel,
Inj Duty cycle is directly proportional to the rpm and boost. It is very possible that you exceeded the rpm range in 1st. (i.e. 8300rpm in 1st and 100% duty cycle) and when you were reading it in 3rd or 4th, it was at 7000 or 7500rpm.

If your 1st and 4th gear rpm is the same, there is no reason for the inj duty cycle to be any different at the same boost level.

 

You know, it is possible that i did hit around 8k... I'll do some more testing..

Thanks Steve.

 

Assuming you have a PFC, you can set the commander to display boost and RPM and then have it record or hold the highest setting. It is too difficult to read both boost and rpm otherwise.