Quick question to APR or other tuner.

[Mars2]

To satisfy my curiosity i would like to know how the Fifth injector of the Flexfuel version of the B8.5 interact in the fueling?
Is it just a super cold start devise or is it full time part of fueling?
If it's full time part of the fueling why did Audi not go for bigger DI injector and skip that fifth injector?

Tuner most know from the different map when that fifth injector is spraying?

[skis4hire]

Is it just a super cold start devise

This. I believe Arin from APR has stated this on the forum probably in the one of the APR Tune threads.

[ParadigmTony]

For the record, I know very little about the flex fuel fuel system. However, in most cases this injector is for a few reasons. Cold start, high demand, and full E85. The difference in flow rate between fuels are why they didn't just go with a larger injector if Im not mistaken. I could be completely wrong, but have come across this on a few other occasions.

[hyperunion]

For the record, I know very little about the flex fuel fuel system. However, in most cases this injector is for a few reasons. Cold start, high demand, and full E85. The difference in flow rate between fuels are why they didn't just go with a larger injector if Im not mistaken. I could be completely wrong, but have come across this on a few other occasions.

It's supposedly designed for e85 cold starts... Secretly it might help with keeping valves cleaner due to it being pre valve placement

[adamazing]

I asked Arin this question a while back because I was hoping that 5th injector would help alleviate carbon buildup on the back of the intake valves. Unfortunately the answer was no, because it's only utilized on start-up.

[Townending]

I asked Arin this question a while back because I was hoping that 5th injector would help alleviate carbon buildup on the back of the intake valves. Unfortunately the answer was no, because it's only utilized on start-up.

I think the E85 alone helps. Heres my valves at 57K. The first 35K was ran using 91 gas, the last 22K was using 99% E85. Compared to the other pics posted in the carbon buildup thread, this is very minimal.

Cylinder 1


Cylinder 2


Cylinder 3


Cylinder 4