IMRC Settings - GT versus GT350

[06300CSRT8]

Not sure I understand this difference, can someone help explain? In the GT350 tune for Optimum Power section, the Hi threshold is set to "Open" AND Low Threshold to "Open" which is not the same as a base GT tune.

In general all driving modes have low rpm set to Closed and hi rpm set to open. The GT stock tune has Optimum performance the opposite, with low rpm set to open and hi rpm set to closed. GT350 has all the same except for Optimum performance which just has both as open.

Stock Tune 2015 PP Manual GT.hpt

FHVJ127 - 2016 Mustang Shelby GT350.hpt

[murfie]

The Cam angles should progress through MP 14-20 with some blending of 24/25 as RPMS climb from 2500-3500. At 3500 to 4250 it should go from mostly or all 25 to split with 24. Above 4500 it should use 20 and 21. The IMRC would need to be open to do this so I would say it uses the best drivability mode not the OP for IMRC above 2500. The OP cam angles tables start at 2500 so maybe this is a way to use the lower MPs in the fuel economy mode between 1500-2500 for cam angles until then as MP 6 and 8 would have cam angles better for emissions and be closer to OP values, if rotating from the lower values of mp 0-2, than the higher 14-17 which it starts at in the lower RPMs. The Gt350 is said to respond very well to VCT tuning in stock form.

[06300CSRT8]

Not sure I follow, I understand why the IMRC needs to be open as you described all the moving through the various MPs, but at no time do I see a reason for the IMRC to be open in any moment the car is in optimal performance mode. The load required to get into OP mode would certainly mean the IMRC should be closed in any of those circumstances. Seems like the GT350 is setup in a way (not obvious to me) that it NEVER uses OP during WOT, whereas the base GT does. That would explain why the GT350 responds so well, seems like setting the IMRC to closed, tweak the load points to ensure it gets to OP quickly, then tweak the OP VCT settings (that to me appear to not be used at all in the stock GT350).

Either way, for my purposes, I am installing a GT350 intake manifold and cobra jet cold air kit and trying to build myself a base tune, this was one of the first things that troubled me. I will leave the base GT settings for now, see how it responds.

[Plimmer]

The IMRC is vacuum operated and the ECM controls the solenoids that bleed off vacuum. That is important to know, because no matter what the tune says about IMRC open or closed, it can only be closed when it sees vacuum.

I found that a lot of my GT350 TB surging was caused by the IMRC opening, then the TB closing, then causing more vacuum, then IMRC closing, then TB opening to allow more air, then IMRC opening, and basically a surging cycle. By logging the TB and IMRC open/closed state you'll be able to figure out the correct IMRC settings

[R8Bill]

I had so many issues trying to get rid of surging, torque and tb error I gave up and stuck with the stock TB and used an adapter on my gt350 intake. Disabling Clipping did help but no matter what I did to the torque tables, Eff Area and Predicted Throttle it never went away. There were many posts on HP forum about how to fix surging but never had any luck 100%. Since then I have removed the IMRC's from the intake to get ready for FI but was thinking of giving it another shot before I do. Can anyone share throttle body setting values for a GT350 intake and TB on a GT auto that actually work without errors?

[06300CSRT8]

^^^ This was my exact fear and is why I have not yet installed the intake/throttle body combo yet. I have a few copies of some tunes provided by the person I purchased the setup from, but from what I understand it still had some surging with the tune I was given.

I have read a few threads by some of the "gurus" on here and they have stated they got it working perfectly by using torque error to adjust the predicted throttle tables but seems a bit like voodoo to me, I don't really comprehend entirely.

It would be awesome if someone with a Power Pack 3 from Ford posted up a scan.