Boost - Losing 5 lbs

Hey all , the other week I had a couple of issues with my car (2012 gt500 )- mainly losing a lot of boost ( boost was down to 10lbs ) and a burning smell coming from under the car . Well , the burning smell turned out to be my right rear brake ( fixed ) .
Boost and car not running well - found 2 vacuum leaks - 1 at the guage / 1 at the T by the S/C, fixed them - tested my e85 , and found it to be more like e68 (problem up here in NY from what I'm hearing ).
Running the VMP Gen 2R , Id 1050's , VMP boost a pump , Kooks longtubes , Afco dual fan H/E , which I noticed seems to be kicking on sooner than usual - even on a cool morning .... - Pump is working - intercoolant fluid circulating when the H/E kicks on ...
Found a station selling real e85 ( tested ) , put the e70 tune in my car ( did compression check - all 8 cyl @ 151-153 lbs ) ,all the plugs looked the same/ok . Put new NGK's in .
Ran the junk fuel out - filled up with the good e85 - put the e85 tune back in . Drove the car a couple of times (easily ) , then hit it a few times my next time out and the boost goes right up to 15lbs and stops ( Ford Racing vacuum guage - not factory - but both read 15lbs .
No abnormal noises coming from anywhere .
My tuner had me at 20lbs on the e85 ( looked at the dyno sheets ) .
Checked again for any vacuum leaks , to no avail .
Can't figure out why I'm losing 5lbs of boost - maybe something with the tune ?

Belt slip?

Yeah , thought the same thing, but checked that - saw no evidence of it - wear / fraying / belt dust , etc .

I would suggest hooking up a electric boost gauge that uses a map sensor. Way more accurate then the factory or manual gauge. At least you'll know without a doubt what your boost is. I was running a autometer manual boost gauge and switched it to a electric gauge. Come to find out I was running more boost then I thought.

I'll look into that - thx

Deff use a real boost gauge.
Really only things that can cause loss of boost I can think of is severe belt slip, vac leak, bypass valve actuation.

Thx - how could I check the bypass valve ?

speedy2012 said:

Thx - how could I check the bypass valve ?

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You want to make sure it's fully closing lso no boost is lost / bypasses. Ony Whipple I can manually move the actuator back and forth to make sure it's not sticking. First up is a real boost gauge. You may not even have a problem.

Any recommendations for a guage ?

Autometer vacuum/boost stepper motor gauge. I run the Elite series, which has some nice playback features.

Maybe your throttle body is not opening fully? If you can datalog, capture pedal position (accelerator input), ETC throttle angle commanded (by PCM), and ETC throttle position (actual) PIDS. Disable traction control; at WOT with pedal position at 100%, ETC throttle angle commanded and position should be similar values and both slightly above 80 degrees.

Gonna have the car dynoed next week . I guess whatever is wrong will surface then . Never thought about the t/b - thanks for the input !

Make sure that E85 tune loaded properly. The E70 tune would have less boost so make sure the computer isn't still reading the other tune.

I took out the e 70 tune , put the stock tune in ( didn't drive it , obviously ) unloaded the stock tune and put in the e85 tune .
Funny thing is , looking at the dyno sheet , it was making 19 - 20 lbs - towards the RPM range - with the E70 tune - weird .

speedy2012 said:

how could I check the bypass valve ?

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Read posts #19 and 22 in this thread: https://www.svtperformance.com/threads/2012-tvs-swap-s.1185814/

Additionally, with a stock long block, manifold vacuum should be ~ 20 In.Hg with engine at warm idle if you can monitor vacuum on your Ford Racing guage.

@speedy2012 , any update after dyno session?

OP = I've been running E85 for 10yrs in my 08, E70-85, same tune, boost doesn't change with the fuel, maybe a little with the weather, cooler temps can give a small increase in boost, that's about it.

GNBRETT said:

Make sure that E85 tune loaded properly. The E70 tune would have less boost so make sure the computer isn't still reading the other tune.

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can you elaborate on how the difference in tune would adjust the amount of boost?

I have a few different tunes and they all have different boost levels associated with them. My 93 tune has far less boost than my E85 and I have a C16 tune but thats pretty close to my E85 tune. Thru my AMS 2000.

stkjock said:

OP = I've been running E85 for 10yrs in my 08, E70-85, same tune, boost doesn't change with the fuel, maybe a little with the weather, cooler temps can give a small increase in boost, that's about it.




can you elaborate on how the difference in tune would adjust the amount of boost?

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GNBRETT said:

I have a few different tunes and they all have different boost levels associated with them. My 93 tune has far less boost than my E85 and I have a C16 tune but thats pretty close to my E85 tune. Thru my AMS 2000.

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Brett - based on your avatar, your use of a AMS ECM and your signiture- I take it you have an electronic boost controller for your turbo set up?

if my conclusion is correct, than you are talking apples and watermelons with respect to the Shelby platform, the levels of boost on the platform are mechanically determined and not controlled by the tune, so there's no way that his tune is causing any boost change. The tune can certainly affect power with the levels of spark and fuel, however, you're comment is inaccurate above.

Different tunes will have different boost levels. So u think ur gonna run the same boost level at 93 octane that u are with an E85 tune? Run the same boost with a blower with an 93 octane tune that u do with ur E85 tune and let us know how it works out.

The AMS is no different than any other boost controller except it has settings u can program for different tunes just as one would swap pulleys for different tunes.

Or maybe u think the guy on 93 octane just throws in E85 with no pulley or tune change and lets it rip? Is that what u really believe? And my last setup was a TVS and yea when I threw in E85 I had to change the tune and swap pulleys to be efficient and ran MORE boost!

stkjock said:

Brett - based on your avatar, your use of a AMS ECM and your signiture- I take it you have an electronic boost controller for your turbo set up?

if my conclusion is correct, than you are talking apples and watermelons with respect to the Shelby platform, the levels of boost on the platform are mechanically determined and not controlled by the tune, so there's no way that his tune is causing any boost change. The tune can certainly affect power with the levels of spark and fuel, however, you're comment is inaccurate above.

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