I have a 07 5.4 that I decided to put a blower on. Rebuilt the engine, forged rods and pistons, 20 over. I put a whipple supercharger on it, and we just cant seem to get it right. It made 370 on a mustang dyno on its first run, but stumbles just about everywhere. We have changed everything I can think of, injectors are 47#, fuel pump up to a 340, new cop's. I did put a 3" pulley on it from the beginning and my boost gauge reads 9# at wot. Wot is about the only place its decent. I've got so much money in this thing its ridiculous, and I can't even drive it.

 

Whats the combo of the engine? Cams, compression, what rods, pistons ect, ect? who built the engine? Have you done a compression and leak down test? Any blow-by?

 

^^^
All great questions..
Definitely gonna need as much info as you can type to help you resolve this..

Did you happen to run the motor with the stock intake manifold prior to bolting on the blower? If yes, Did it run fine then?

Have you done anything to the stock exhaust system or put a wideband 02 in to be able to read the AFR?

Have you made sure there are no vacuum leaks at the fuel pressure regulator? Also, has the FPDM been checked for corrosion?

Who did your engine tuning? Have you contacted your tuner to see if it has anything to do with the calibration??

 

Sorry if this sounds elementary but my neighbor had simply changed the pully on his lightning and the truck began to fall on its face. The solution was a smaller gap on the spark plugs, the factory ones werent firing properly under the higher boost levels. Its just easy and cheap to check.

 

Thats called spark blowout. Primarily takes places at WOT. When spark plug gap is to large combustion pressure can actually blow out the spark.

Recommended gap is .030-.032 for a boosted motor. I run .035. No blow out and that provides the max power.

 

Op I'm guessing you have some tune issues. Maf transfer function is a great place to start. Need all the details on your truck that you can provide.

 

We built it so I could run the blower with more boost, so the blower went straight on the fresh rebuild. Compression is just a hair over 9:1 and we put stock cams back in because its a daily driver, flowmaster cat back and didn't change any of the o2 sensors. I'm using a local tuner, here in tampa. Its been there several times, and he uses diablo. It is a crew cab 4x4 so I know i'm going to loose more than usual from the drivetrain along with the 12.5 in wide 33" tires. Even with that the numbers seemed a little low. We have checked for vacuum leaks and found one but it didn't change much, just cleaned up the idle a little. We went with the gap recommended by whipple for 12#, because I've got the 3" pulley. But since I'm only getting it up to 9# should I rethink the gap? I think the aeromotive 340 fuel pump should be enough, i'm not wot often.

 

We kept the 88mm Maf that came with the whipple. We put a mic on the 03 cobra maf that everyone says is 95 and its really only about 90, so it didn't seem reasonable that that would make that much of a difference.

 

Did you guys follow the install manual from whipple when you bolted it in the blower?
What thermostat are you running?
The 160 degree stat that whipple recommends?? It could be too cold.. Try a 180 or run the stock 195 if your running the 160. Where was the vac leak you found?

Have you done a test on the bypass valve to make sure there it is functioning properly?........(Pull vacuum line off on diaphragm, hold open the valve with you finger at the rod, put your thumb on the vacuum diaphragm port and release the valve.. If it closes all the way then you have a vac leak at the diaphragm..)

The 88mm MAF is too small for 9lbs.. Your MAF needs the bigger 95mm housing to slow the air charge down to allow it to get a good reading..

Have you confirmed that your inner cooler/pump/and heat exchanger are circulating? Any engine codes???

I bet its in the tune, but if you are running the 88mm MAF that will have some affect on this condition..


Stock 88mm MAF right, 95mm left..

 

Have you pulled plugs to inspect them for burn condition?