Only getting 10 psi with VMP 2.5 pulley and 90mm idler...any ideas why?

[ridge68]

I recently installed the VMP 2.5 stock look pulley and 90mm idler package on my 2012 GT500, along with one step colder Motorcraft plugs that VMP lists on their site. I already had installed a Steeda 113mm cold air kit, Corsa Extreme mufflers that I kept from my 11 GT/CS, along with a Steeda tune. I received an updated tune for the 2.5 pulley, also from Steeda. The car is relatively low mileage, around 10k. Why am I only seeing 10 psi on the boost gauge? From what I read, I should be seeing 12-14psi...any ideas? Your thoughts would be greatly appreciated!!!

 

[zporta]

factory gauge?

if so they are not super accurate.

 

[ridge68]

Yea...factory gauge. Never really thought of that. Only had the car since December 30th of last year, unfortunately I really couldn't get into the throttle fully when it was completely stock because it was so cold and unusually snowy this winter in Virginia. I don't think I was able to get a full boost run while it was stock for reference because of the weather...damn...I was too busy trying to keep it on the road to look at the gauge if you know what I mean
I was thinking maybe some belt slippage, I used to have an auxiliary pulley on my 03 Terminator to increase belt wrap around the blower pulley. I went with the VMP setup with the 90mm idler instead of getting an auxiliary pulley for belt wrap. Justin at VMP says in his forums the auxiliary pulley isn't necessary...didn't make a difference...but I'm wondering...

 

[54First]

The 90mm idler is all you need. Get a mechanical boost gauge before you start to worry. And I cautiously suggest, though some will disagree, that a tune calibrated incorrectly can also cause the PCM to calculate your boost incorrectly.

Steve

 

[me32]

The 90mm idler is all you need. Get a mechanical boost gauge before you start to worry. And I cautiously suggest, though some will disagree, that a tune calibrated incorrectly can also cause the PCM to calculate your boost incorrectly.

Steve

ditto, I would check with a mechanical gauge 1st

 

[ridge68]

I would think Steeda is a reputable tuner...haven't read anything bad about them. The car runs great...no issues. I plan on visiting the VMP mobile dyno when it comes to MIR in May...hopefully that will answer some questions.

 

[zporta]

how does it feel by judging by you butt dyno?

 

[1320 Junkie]

The 90mm idler is all you need. Get a mechanical boost gauge before you start to worry. And I cautiously suggest, though some will disagree, that a tune calibrated incorrectly can also cause the PCM to calculate your boost incorrectly.

Steve

↑ 1000% accurate

 

[VNMOUS1]

Stock "boost" is inferred via feedback from the maf. If your maf curve has been shifted (and it will if you change cai) your "boost" will not read the same as with the stock curve. Makes no difference who tunes it, and it has nothing to do with the calibration being done correctly.

 

[1320 Junkie]

Stock "boost" is inferred via feedback from the maf. If your maf curve has been shifted (and it will if you change cai) your "boost" will not read the same as with the stock curve. Makes no difference who tunes it, and it has nothing to do with the calibration being done correctly.

Your not explaining it correctly. The calibration aka Maf flow curve has EVERYTHING to do with who tuned it. Those fields are modified by Steeda according to the ops original post he has a tune in the car from them so if they didnt input the proper maf curve (aka a true 26"in/hg flow bench 36 point curve) and just scaled it with a "ball park figure" his boost reading will be off. Ive seen this multiple times from big name tuners and im honestly shocked they get away with it..albeit the car runs like crap..but runs.

Op...i would get a digital Boost gauge from a top end manufacturer so u know its a quality piece. The stock boost gauge is inaccurate and basically a guesstimate. I recommend autometers digital series..or aeroforce

 

[ridge68]

My "butt dyno" has been inconclusive so far...even though we're getting some warmer weather now, traction can still be a problem even in 3rd gear. Yesterday I was able to WOT in 3rd getting on I-95 without wheelspin, it pulls pretty good...but being a HP junkie like almost everyone else on this website,(lol)... after observing only 10 psi on the gauge on numerous occasions, I want to make sure I'm not missing out on some HP from some oversight. Didn't want to go the gauge pod route yet with just a few bolt-ons...maybe if or when I get a TVS...
I know that part of the traction problem is tire related...275/35/20 Cooper RS3's on Roush 20 X 9.5 Hyper Black wheels all the way around. I bought some 305/35/20 Nitto 555r's from Discount Tire Direct when they had the $100 off coupon code...found 2 matching Roush wheels for a great price also. Wasn't planning on spending $1K on a drag radial set-up, just sort of happened...lol...hope the wife understands. Think I did pretty good price wise. I know I could have had a cheaper 15-18" set-up, but I'm kinda anal about aesthectics...wanted matching wheels.
Hope the wife is at work when the AFCO dual fan H/E comes...lol

 

[ridge68]

Hmmm...will definitely visit the VMP mobile dyno at MIR...

 

[DGladhill]

Weather has been poopy around here lately, supposed be hitting 80 on Sunday though!

 

[VNMOUS1]

Jay, this has been debated, cussed and discussed ad nauseum. Your post began with pointed language that benefits no one.

Everything I said in my post is correct;

1. Factory boost is inferred.
2. The MAF is a critical component of that inferred sum (there are others as well)
3. Regardless of who makes that shift in the curve it will have an effect on the inferred boost. ("It makes no difference who...")
4. That doesn't mean it's done correctly or incorrectly. It's simply shifted and it changes the inferred data. May be wrong, may be correct. Depends on who tuned it.


The OEM method of arriving at a mass air transfer function and the aftermarket method differ 180*. There is no right nor wrong, just different.

In a perfect world, every aftermarket manufacturer would have the luxury (and resources) for lab time, take those numbers and enter them into the transfer function. I don't know if that's the case with all the cars you tune but it is overwhelmingly not the case within the industry and why even OEM calibrators use adjustment of the xfer function as a tool in aftermarket applications. (reference http://www.calibratedsuccess.com/Basic.htm)

If the mega-dollar OEM method was the ONLY safe, effective method there would be a lot of calibrators, tuning software companies and much of the aftermarket out of business. Fortunately, that's not the case.

Your last paragraph is helpful to the group and, not that it matters, but I agree wholeheartedly.

Regards-

bj

Your not explaining it correctly. The calibration aka Maf flow curve has EVERYTHING to do with who tuned it. Those fields are modified by Steeda according to the ops original post he has a tune in the car from them so if they didnt input the proper maf curve (aka a true 26"in/hg flow bench 36 point curve) and just scaled it with a "ball park figure" his boost reading will be off. Ive seen this multiple times from big name tuners and im honestly shocked they get away with it..albeit the car runs like crap..but runs.

Op...i would get a digital Boost gauge from a top end manufacturer so u know its a quality piece. The stock boost gauge is inaccurate and basically a guesstimate. I recommend autometers digital series..or aeroforce

 

[ridge68]

So...the jist I'm getting is that the Steeda tune could be the culprit? I just find it hard to believe that the factory gauge could be that far off. I always thought that pulley(s) size was the only determining factor...that's why I suspected some slippage. I am certainly open to trying a different tune...

 

[1320 Junkie]

Jay, this has been debated, cussed and discussed ad nauseum. Your post began with pointed language that benefits no one.

Everything I said in my post is correct;

1. Factory boost is inferred.
2. The MAF is a critical component of that inferred sum (there are others as well)
3. Regardless of who makes that shift in the curve it will have an effect on the inferred boost. ("It makes no difference who...")
4. That doesn't mean it's done correctly or incorrectly. It's simply shifted and it changes the inferred data. May be wrong, may be correct. Depends on who tuned it.


The OEM method of arriving at a mass air transfer function and the aftermarket method differ 180*. There is no right nor wrong, just different.

In a perfect world, every aftermarket manufacturer would have the luxury (and resources) for lab time, take those numbers and enter them into the transfer function. I don't know if that's the case with all the cars you tune but it is overwhelmingly not the case within the industry and why even OEM calibrators use adjustment of the xfer function as a tool in aftermarket applications. (reference http://www.calibratedsuccess.com/Basic.htm)

If the mega-dollar OEM method was the ONLY safe, effective method there would be a lot of calibrators, tuning software companies and much of the aftermarket out of business. Fortunately, that's not the case.

Your last paragraph is helpful to the group and, not that it matters, but I agree wholeheartedly.

Regards-

bj

$300 is what it costs to get a 36 point flow sheet done and flowed in your maf housing (mine was done filter attached as well)....ask me how I know. If thats out of reach then this hobby isn't for them. Personally I do shit the right way...thats how ford gets their maf data so thats how I get mine...no guessing needed. My car runs perfectly and shows proper parameters as it should.

 

[VNMOUS1]

So...the jist I'm getting is that the Steeda tune could be the culprit? I just find it hard to believe that the factory gauge could be that far off. I always thought that pulley(s) size was the only determining factor...that's why I suspected some slippage. I am certainly open to trying a different tune...

Let us know if we can be of assistance.

http://vmptuning.com/vmp-custom-tunes/gt500tune/

Regards-

bj

 

[1320 Junkie]

So...the jist I'm getting is that the Steeda tune could be the culprit? I just find it hard to believe that the factory gauge could be that far off. I always thought that pulley(s) size was the only determining factor...that's why I suspected some slippage. I am certainly open to trying a different tune...

Absolutely...Justin is a good tuner. If he is close then go to VMP.

 

[Tob]

I don't know if that's the case with all the cars you tune but it is overwhelmingly not the case within the industry and why even OEM calibrators use adjustment of the xfer function as a tool in aftermarket applications. (reference http://www.calibratedsuccess.com/Basic.htm)

Exactly what I was thinking.

...there is indeed more than one valid calibration method. However, both methods (if they're done right) should come to the SAME solution. That's right, you should end up with the same MAF transfer function whether it was derived on a certified flow bench or if it was solved for in the vehicle as long as the other assumptions were properly addressed. If you get the "right" MAF curve either way, load is by definition correct, and so is the torque model (all else being correct). On a modified car, you will still need to do plenty of ETC control calibration, but all of that cannot even start until you have confidence in your MAF reading and load calculation.

I've lost count of how many engines I have tuned either way. The trick is to follow the rules and make sure you are aware of your "knowns" in either case.

Brilliant mind he has.

 

[VNMOUS1]

Exactly what I was thinking.



Brilliant mind he has.

Kinda how I see it as well Tob.

bj