I will try to explain the whole deal so you gurus can give me some ideas on what went wrong...

Last Saturday i went to Etown for the second time ever, wanting to get the car into the 11s...

The first time ever i managed a 12.14 @ 114.23 mph on pump and 23psi boost and the stock clutch on my 4th pass ever...Track temps were in the 50s...

This Saturday track temps were close to 80 degrees... This time i decided to use some racegas and up the boost a little bit just to see how the car will do... When i arrived at the track i had the fuel light on so i pumped 3 gallons of 116 octane... ( i dont know if it affected the car badly in the end...)

First pass disappointing... a did a decent launch 1.73 60ft but the car did 12.24 with 112.9 mph less and i was spiking 26psi!!!! I freaked out... 3psi more boost and lower traps? something must be wrong!!! I didn't log this pass...my stupitidy!!!

Second pass! i setup my laptop, go to the starting line. The 2step at 5800rpm, i launch i get 1.71 60ft and the pass was 12.19 @ 112!!! STILL LOW TRAPS with 26psi spike!!! I check the log i see ZERO knock, and nothing strange... However i noticed my afrs were in the 10s (plx m300)... Me and my friend started thinking that the car due to higher temps is dumping more fuel and it holds it back....

NOTE: I HAVE A 93 octane TUNE, which is perfect for 93 octane and 22-24psi spikes on the road and the car pulls like a tugboat!!!

Third pass: I say f... it... use more boost! 28psi spike, i bog the car of the line even with the 5800 2step 1.99 60ft and a disappointing 12.69. Afrs still in the 10s...

hmmm, something is not right i say... and i take the trip back home...

tonight i am looking my logs and i compare them with my 12.14 pass logs... So i see the next significant defferences:

1. AccelEnrich is 100 on my old pass (93 octane) and on this pass were 200!

2. fuel trim low is 100 in both runs

3. fuel trim medium is 100 in the 12.14 old run and 101.5 on the racegas run!

4. fuel trim high is 107.8 in the old pass and now it was 144.5 !!!

5. knocksums were zeros everywhere in both runs

From what i understand, for some reason the car was dumping fuel like crazy as normally i see low 11 afrs and now it was running in the 10s...

What the deal with the fuel trims?

Is it possible that the ambient tempratures affected the car so much to create much problem?

Can someone explain what it might went wrong with the whole fueling deal?

I know that using a 93 octane map with racegas and more boost is not the ideal thing to do, but i definitely want expecting to run even lower traps than when used the 93 octane!

Any suggestions?

P.S. definitely i will have my tuner make me a racegas map for the strip....

 

I bet your map is ultra rich in 280, 300 load. (meaning not tuned for high boost)
Arent trims for closed loop only?

 

When you run a higher octane fuel your AFR will richen. Fuel trims only matter when in closed loop.

 

BTW the low and high fuel trims are switched for some odd reason in evoscan. So your high trim (which should be low trim) is off. The trim is for idle.

 

This is it most likely.

When you changed your boost, you were changing the parts of the map that you hit. You probably were getting lower timing too because of it.


Eric

 

two things were happing

First off you were running in untuned areas of your maps, when you jacked up the boost.

Second off, and most importantly, you were running race gas, which you were not tuned for.

Race gas burns slower than pump gas(93), which raises the detonation threshold of the fuel. Your ignitoin timing was optimized for 93 octane..... Because race gas burns slower, the slower flame front propogation requires a advance in ignition timing to take full advantage of the fuels detonaiton resisitance. So, if you were still running ignition timing thats optimized for 93, it's going to be really really retarded while running on race gas. When you retard ignition timing, your AFRs go rich. The more you retard ignition timing...the richer the AFR will go. It's reverse if you advance ignition timing.

The reason why we run high octane fuels( 100+) is to be able to advance ignition timing, lean AFR and run more boost safely. If you did not do these things, you likely lossed power, raised EGT's and became slower.

Couple that with you running in untuned areas of your maps, which will only make matters worse if those areas of the maps were not tuned properly for 93 octane.

CJ

 

fuel trims only effect closed loop feedback.

CJ

 

Thanks all guys for the answers....

iTune, thanks a lot mate! awsome technical explanation! You have been really helpful!

well i assumed that the car wouldn't run optimal with the racegas but i didn't expect it to run so much worse than the 93 octane gas!

Next time the car will go at the track with a nice drag map, again on 116 octane (C16 or similar) and see what we can do!

 

Yeah, get some c16......or whatever you can get at the track and do some street tuning using it. You will want to advance ignition timing and lean AFR a bit (11.8-12.0:1) Then, progressivly raise boost to your desired boost level, tuning the maps as you go up.

Watch out though, the leaded gas will foul out your o2Ss.

CJ

 

You need to create 2nd map for race gas race gas+more boost=retune.

 

i know that mate but i don't really care...

when they go bad i will change them.

i wouldn't even mind changing them every year!

The satisfaction of the racegas, boost and good track times is priceless...!!!

 

In addition to iTunes points...

What are your intake temps between the 50* day an this 80* day? The open filters can heat soak easily. Temp compensation can come into play and richen your afrs.

 

On the 50 degree day my intake temps were starting around 106-108 degrees on the 2step and dropping to 67.7 degrees in 4th gear...

On the 80 degrees on last saturday intake temps were starting at 126-130 degrees and dropping to 80 degrees in 4th gear...

i just love my Turbo-XS intercooler!!! and i believe that if a had a more open front bumper like the 8's or an aftermarket one so the intercooler isn't covered by the bumper and crash beam its performance would be even greater...

In addition sunday i re-installed my apexi induction box which protects the filter from engine temps. Now i am also working on a ram air tube if i find a passage from the bumper or maybe i will get the Evodave's front light intake

 

126-130 degrees is for sure enough to have the temp compensation richen your AFR a bunch. Did your AFR's at WOT go back to normal after the track, say, while at hwy speed where the filter can get fresh, cooler air?

The intake temp is measured at the MAF, before the intercooler on our cars, so even if your FMIC is doing a good job of dropping the actual intake charge post turbo, the ECU is still correcting based on MAF temps

 

so what's the solution when tuning on a dyno to simulate more real world approach? tuning with the hood closed?