How To Properly Set P/I-R Trimmer
 

When tuning my HFS-4 board, I've been trying to research and understand the dynamic impact of my specific DI vehicle (2011 VW GTI) along with my hardware upgrades (small turbo upgrade, etc) and tuning software choice.

After choosing the correct jet sizes, I feel confident in my Gain / Threshold settings along with TRIG set to MPS. The one setting that has me really confused is P/I-R. How are other turbo/forced induction direct injection users choosing their P/I-R settings?

I assume the P/I-R setting should be dependent on the specific tuning software a user may have. Should I be capturing fuel trim logs and boost logs with my ODB VagCom reader then use the data to compile a proper P/I-R setting? Would anyone be able to tell me what data points could lead to the best P/I-R setting? Is there a way to read out the software on the HFS-4 board to lead to a better P/I-R setting choice?

Definition from the HFS-4 User Manual:
- P/I-R: Alter the flow relative to boost or fuel. For 100% boost controlled, set the trimmer fully counter-clockwise. Vice versa for fuel. Trimmer at mid point is 50% pressure and 50% IDC.

Thank you in advance for any advice or help you may be able to offer.

Re: How To Properly Set P/I-R Trimmer
 

The PI-R is an additional option for improving the effectiveness of the wmi delivery. if you have a small turbo that is operating beyond it high efficiency range, you might like to bias the Pi-R towards the P. It will help cooling the charge air better.

Re: How To Properly Set P/I-R Trimmer
 

Richard, thank you so much for your support and help. This is very valuable information. I did upgrade my GTI's turbo to the next OEM size up (same as the Golf R) and am running it at the top end of it's efficiency range.

Do you think a 60% IDC / 40% Boost setting on the P/I-R trimmer is a good setting?

Re: How To Properly Set P/I-R Trimmer
 

The 60%-70% IDC is good

Re: How To Properly Set P/I-R Trimmer
 

Thanks Richard, as per the HFS-4 User Manual it says for 100% boost controlled, set the P/I-R trimmer fully counter-clockwise. Vice versa for fuel.

Since I have a smaller turbo operating in the higher end of it's efficiency range, you recommended the I set the P/I-R trimmer counter-clockwise towards the P to help cooling the charge air better which is more boost biased.

I think I meant to say do you think a 60% boost (P) / 40% IDC (I-R) setting on the P/I-R trimmer is a good setting?

Re: How To Properly Set P/I-R Trimmer
 

Sorry. no thinking well today. 60% Boost 40% IDC

Re: How To Properly Set P/I-R Trimmer
 

Thank you Richard, I don't think well all week ha. I knew that's what you meant. So far the system is dialed in almost perfectly, can't wait to increase the flow rates to see how the car performs.