WGA, throttle body and DSP

[Todd@VanIsland]

I recently bought a DSP and am about to use it on my '04 SRT-4. But before I had it, I had switched to an AGP WGA. It worked fine, held boost well around 15-16 psi, but caused alot of "fluttering" during mid-throttle boost (not during full throttle boost). Note I do have a CAI, Borla exhaust and Stage 1 PCM. I then got "convinced" to buy an MPX 62 mm throttle body -- when I put it on, while the throttle response was much faster, it essentially caused the disappearance of all mid- and high-range power. It's as if the PCM is saying there's too much air and cutting back the fuel. IS THIS WHAT'S HAPPENING??

So now that I have the DSP, should I put the stock WGA back on (Diablosport seems to recommend that). Can I keep the 62 mm throttle body on if I do a custom tune with the DSP, or should I put the stock TB back on too??

All advice much appreciated!!

[enginjoe]

Get rid of the throttle body no matter what. You don't need anything that big until you are making well over 500whp. A bore'd out stock TB is just fine (55mm btw) once you are making real power. This is what I'm using.

Get a stock or stage 2 WGA for the DSP.

[tunerlover3]

Get a stock, stage 2, or FM wga.

If you have the TB you might as well use it. No the PCM will not "pull back fuel" with a bigger TB. If you are losing upper end power its probably a boost leak.

[Todd@VanIsland]

OK, I'll go back to the stock WGA. Will the DSP tuner allow me to get 18-20 psi peak boost and hold 15 psi boost with the stock WGA? I'll check for leaks on the 62 mm TB, but I could go back to the stock TB too.

[tunerlover3]

Yes you can spike much more then that if you wanted. The 93 octane tune usually hits around 20.

[Todd@VanIsland]

OK tunerlover -- one more question. I've put the stock WGA back on and good to know it'll give me decent boost pressure with the 90 oct. tune. But I left the 62mm TB on and boost is about 2 psi max. So is this a boost leak or should I ditch it and put the stock TB on. Thanks!

[tunerlover3]

You have another issue not related to the TB.

Double check your vacuum lines.

[Todd@VanIsland]

OK, I'll check the vacuum lines and let you know what I find. I have a suspicion I've messed something up when I put the stock WGA back on.

[Zenkat]

Quote: Originally Posted by Todd@VanIsland

OK, I'll check the vacuum lines and let you know what I find. I have a suspicion I've messed something up when I put the stock WGA back on.

If you were running an AGP you probably had a line from the WGA to the turbo. This is called 'off' PCM boost. What you need is to go back ON PCM boost. Put all the stock vacuum lines back on the car where they normally go.

I'm assuming this is what happened when you said you can only boost 2 psi. Let us know how it goes, and if you have questions about proper vacuum line placement.

[TRPKelly]

Quote: Originally Posted by Zenkat

If you were running an AGP you probably had a line from the WGA to the turbo. This is called 'off' PCM boost. What you need is to go back ON PCM boost. Put all the stock vacuum lines back on the car where they normally go.

I'm assuming this is what happened when you said you can only boost 2 psi. Let us know how it goes, and if you have questions about proper vacuum line placement.

i had this exact same issue when i switched from the AGP back to stock (i completly recommend btw), and that was the exact fix i had to do. if still using the stock vaccumn lines, check the green line, thats what was rerouted on mine, with the wastegate line run to the turbo. me and a buddy just moved those two lines back to stock location, its right on the sticker on the hood, and everyrthing worked great after that. solid boost through the whole rpm range, no power loss, no hesitation, no flutter

SAMSUNG-SGH-I997 using AutoGuide.C

[tunerlover3]

Good to hear.

[Todd@VanIsland]

thanks alot TRPKelly and Zenkat. I had forgotten to hook up the original 2 vacuum lines (green and balck tubes) coming off the #2 solenoid. So just to be clear, the green line should go to the turbo and the black one to the wastegate?

These 2 lines were'nt needed with the AGP WGA -- I just had a line going directly from the turbo to the WG.

I'll let you all know how things work when I finish the DSP dyno tune.

[Zenkat]

Quote: Originally Posted by Todd@VanIsland

thanks alot TRPKelly and Zenkat. I had forgotten to hook up the original 2 vacuum lines (green and balck tubes) coming off the #2 solenoid. So just to be clear, the green line should go to the turbo and the black one to the wastegate?

These 2 lines were'nt needed with the AGP WGA -- I just had a line going directly from the turbo to the WG.

I'll let you all know how things work when I finish the DSP dyno tune.

You got it. Just make sure theyre on the proper spot on the solenoid. Black line in middle, green close to wires.

[Todd@VanIsland]

thanks Zenkat. I'll be sure to get that order on the #2 solenoid. Doing the DSP and dyno tune next week -- will be interesting to see the dyno results.

From your SRT photo, it looks like you have wider wheels (mine are stock), which allows you to put on wider rubber. What size wheels do you have?

Thanks!

[Zenkat]

Quote: Originally Posted by Todd@VanIsland

thanks Zenkat. I'll be sure to get that order on the #2 solenoid. Doing the DSP and dyno tune next week -- will be interesting to see the dyno results.

From your SRT photo, it looks like you have wider wheels (mine are stock), which allows you to put on wider rubber. What size wheels do you have?

Thanks!

Just 17x7 with 225 tires. The wheel offset makes them flush with the body, which looks awesome.