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2015 Mustang GT - Low Load, MAP, and Torque at WOT (No idea why)

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2015 Mustang GT
Gen 3 Shortblock, Gen 2 Heads, Stage 3 N/A Comp Cams (full vct)
Stock TB, Stock CAI, Stock injectors, Ported 2018 Manifold with IMRC, Headers
(Put stock cai & stock injectors to help diagnose issue)

Just started my adventure into tuning and me and some guys at Mustang6g noticed my load was really low at wot (~0.75). I put on the stock cai and injectors and still had the same results.

The only consistent fix we have found is raising (auF0372) Baro Min Pressure to 30 inHg to match the Baro Max Pressure. This will push my load back up to my manually calculated load at high .8s to just hitting .9. 

With the low load there is some other things that change. All the torque requested/demanded is down, map (from tp model, max, and from desired) are all lower (but not the standard map you log), and effective throttle area is lower.

Logs aren't showing any TB issues and I don't see it showing me any limits its hitting or where/how its having an issue.

I am attaching the tune (with the baro min change) and logs with HPT and PCMTec (I am not familiar with the pcm tec logger yet). If the log says "Working" it has the baro min patch to fix the load.

Any help would be greatly appreciated. This car has been tuned before by several tuners. Lund managed to get it right but I've had one really struggle and the other did okay. Lund never mentioned this issue to me and the load numbers I've seen in their logs look fine.

Stuart 91 S2 (stock cai-inj).tec S2 Load Test2 ManifoldVolume.zip HPT S2 Test 5 ManiVolume.zip

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Speed density being incorrectly calculated will result in the load being incorrectly calculated. The fact you have changed your camshafts means the VE has now changed and you are no longer getting the same VE (hence lower load). The speed density needs to be recalculated to account for this. Have you adjusted this? Barometric pressure and others will also need to be adjusted as the car will no longer be idling at the same kpa.

This is not a trivial task to do correctly however there are some tutorials and tuning guides available for earlier models of vehicles which may assist you.

I have seen people simply fudge the MAF curve to fudge this, however this is not the correct method as your VE changes non linearly across RPM and throttle (inferred load). Eg you are getting blowthrow/reversion at low rpm (eg lower cylinder air mass hence lower load), however this assists cylinder filling at high rpm (eg higher load).

This is one course I found online, I would also recommend anything you can find by Greg Banish or La Sota (if he ever did a camshaft tuning course). These are likely to be for the 11-14 vehicles however the principles are the same.


Alternatively Lund have tuned many vehicles with camshafts and understand the principles behind what is required, they absolutely would be able to do a tune for you, however they will lock the tune so this won't help you with learning to do it yourself.

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  • 3 weeks later...

Tuning your speed density tables is not terribly hard, but very time consuming. You should do SD tables, boarderline spark, and torque tuning individually for each mapped point. You need to lock in to an individual mapped point. This means your cams and IMRC are fixed at that mapped point that you are tuning. You need a MAP sensor and you need to log Calculated manifold pressure. use a speed density calculator from HPTuners and adjust the table based off the difference between actual MAP and Calc MAP.  When you hit a limit and it wont increase the VE table then increase the Aircharge Multi table. You will have a little trial and error but will quickly learn how to adjust the tables. I use to use a histogram that give you a % you can multiply by, but it never worked as well as it sounds like. Now I just make manual changes and blend the changes in. This will take a lot of time with aftermarket cams, but your car will drive awesome when you are done. If what I said is not making sense and you still want to tune it yourself go to Evans Tuning Academy, he does a fantastic job teaching you to tune. I have bought and read all the books available for tuning the coyote and no one has it as figured out as well as him. Good luck.

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