Blower By-pass mod

[LFacemire Jr]

can some one please explain what the blower by-pass mod is and how well it works?:cbra:

[dwtalso]

Occasionally, under load, with pressure above 8 psi (like after a pulley swap), the PCM will dump boost and it takes moment to recover. The mod prevents this from happening.

[MadMax]

I have owned three Turbo charged cars in my life before buying the Supercharged Cobra. I had a 1990 300ZX modified to 14 lbs. of boost (420hp) then later on I had a 1995 300ZX with duplicate mods 14 lbs. (420hp) and lastly I modified my wife's 2002 Subaru WRX to (280hp) with 14 lbs. of boost. All of them ran safely on 93 octane pump gas with no injector swaps or anything like that. But...and this is a BIG BUT....I always left the boost bypass system alone because it's like a failsafe for your motor. The engineers put it there for a reason....so you wouldn't overboost your motor. If you go down that path brother, I hope you've done everything you can to keep your motor tight. I'm not going near the boost bypass circuit on my Cobra, even when I swap to a smaller blower pulley later. It's like someone pouring a bucket of water down your throat. You can only drink so much then the rest has to go somewhere!!

[LFacemire Jr]

But with a PHP nose cover and 6#pully totalling near 14lbs. I wonder what the factory is set at? and is there somewhere inbetween that could still be safe on the engine? I am new to blower motors so if I sound like Iam thinking backwards I may be.:huh:

[roger]

Originally posted by LFacemire Jr
But with a PHP nose cover and 6#pully totalling near 14lbs. I wonder what the factory is set at? and is there somewhere inbetween that could still be safe on the engine? I am new to blower motors so if I sound like Iam thinking backwards I may be.:huh:

When you dyno are you going to get an air/fuel reading? I'd be curious to see that with your 6# pulley.

[MadMax]

LFacemire Jr, The pulley swap ia a supposed safe mod as long as you don't go for too much boost. I've already ordered my Paul's High Performance complete front blower snout with #5 lbs. boost adder pulley already installed. The reason I'm taking a leap of faith is because of an article in the November issue ( I Think) of 5.0 and Super Fords magazine. In the article they took a bone stock 2003 Cobra and contracted JDM Engineering to replace the stock large diameter Cobra pulley with a discarded upper pulley from a Lightning Pickup. The diameter of the Lightning pulley is 2.93 inches. The only other modification was they yanked out the stock air filter element and left it open with no filter. With this set up the boost went from 8.5 lbs. to 14.5 lbs. : which pegged the in-dash gauge. When you increase boost, you have to watch out for your fuel/air ratio so that it doesn't get too lean. All the Turbo cars I mentioned in my above post had very rich fuel settings to compensate for the 14 lbs. of boost on our cheesy 93 octane gas we use. This is why a lot of guys go with a Diablo chip mod to their stock engine control computer to keep the fuel curve nice and rich as to not fry any valves or scorch pistons. BUT...listen to this...the guys in the Ford magazine article hooked up a professional Horiba Air / Fuel meter to the Cobra after they swapped to the small pulley and the fuel curve was still plenty rich even with the stock fuel injectors. So basically what all this implies to the Mustang enthusiast is that if you swap to a smaller pulley on your Cobra, as long as you don't exceed 14 lbs. total boost you should be O.K. running 93 octane. Oh , by the way, on 10-inch slicks the car ran 11.6 at 119 mph in 1/4 mile AND was putting out over 500hp at the flywheel !!! Cool huh?

[JTFX6552]

I don't know what was up with the MM&FF car, but mine was way lean with the "L" pulley and no chip. Dyno curves are on my website listed in the signature.

JT