Magnum Powers
Registered User
Hi Guys!
As some you know I’ve been developing a supercharger kit for the Ford modular engine. The first kit fits the Mustang 99-04 GT and is being sold under the Tork Tech Inc banner. The kit is just now hitting the market and you can review my latest venture at www.torktech.com.
In the process of developing this kit I came across an issue I think the Supercoupe community should consider. The 4.6L 2-valve engine has rather sickly connecting rods that can’t take more then about 400 foot pounds torque without breaking so we adjusted pulley sizes so the standard kit would produce a torque and hp number that would leave a stock engine intact. We ended up running 10-psi boost making about 400 torque and 400 hp with the standard kit that uses a Focus SVT fuel pump that is rated for 255 lph.
Now comes the interesting part. The Focus pump at 5800 rpms was nearly maxed out at 95% duty cycle, making 400 hp at 10-psi boost!
I am not sure of the exact number without doing some research but I am sure there are well over 100 Supercoupes out there with the MPx running 25% overdrive, some are upgrading to the 30% kit as well making 18-psi boost or more. A few years back we made 390 rwhp with the MPIII running 15% overdrive up here in the Northwest and we also saw about 15 hp for ever 5% increase in overdrive. So, I figure if all things are well and in order there are a lot of SC’s that should be running around 420 rwhp with the MPx or at least wanting to do so.
And this brings me to my concern: If a 255lph pump is max’ed out delivering enough fuel to support 400 hp at 10-psi boost it must not be able to supply enough fuel to support 400-420 hp at 18-psi!
So, I am thinking at high rpms the fuel pressure across the injectors must be dropping. The tuner of course would compensate for this by increasing the fuel injector duty cycle to keep the a/f ratio correct however the injector would be supplying the fuel at a reduced pressure causing the spray pattern to be less then ideal.
Now, if the fuel pressure is indeed low the fuel pressure regulator will have closed the return hose back to the fuel tank completely. Now when the car starts to accelerate there will be an additional pressure drop in the fuel line due to G forces that will reduce the fuel pressure even more. So, if the car was tuned on a dyno to the proper a/f ratio when going down the track the car will run lean. FYI, I burned a hole as big as my thumb in one of my Lightning’s Probe pistons due to loss of fuel due to acceleration, in that case there was not enough gas in the tank.
I can’t say this is a “real” problem or just a potensial one however it is an issue that someone could investigate and report on. BTW, there are a lot of Mustang speed shops that will not release a supercharged 400hp Mustang GT out of their shop without a 03-04 Cobra dual fuel pump fuel tank, something to think about…..
Cheers,
Charles
Also, thanks for your support: Magnum Powers’ Supercoupe sales have been quite good this year, thanks so very much!!!
As some you know I’ve been developing a supercharger kit for the Ford modular engine. The first kit fits the Mustang 99-04 GT and is being sold under the Tork Tech Inc banner. The kit is just now hitting the market and you can review my latest venture at www.torktech.com.
In the process of developing this kit I came across an issue I think the Supercoupe community should consider. The 4.6L 2-valve engine has rather sickly connecting rods that can’t take more then about 400 foot pounds torque without breaking so we adjusted pulley sizes so the standard kit would produce a torque and hp number that would leave a stock engine intact. We ended up running 10-psi boost making about 400 torque and 400 hp with the standard kit that uses a Focus SVT fuel pump that is rated for 255 lph.
Now comes the interesting part. The Focus pump at 5800 rpms was nearly maxed out at 95% duty cycle, making 400 hp at 10-psi boost!
I am not sure of the exact number without doing some research but I am sure there are well over 100 Supercoupes out there with the MPx running 25% overdrive, some are upgrading to the 30% kit as well making 18-psi boost or more. A few years back we made 390 rwhp with the MPIII running 15% overdrive up here in the Northwest and we also saw about 15 hp for ever 5% increase in overdrive. So, I figure if all things are well and in order there are a lot of SC’s that should be running around 420 rwhp with the MPx or at least wanting to do so.
And this brings me to my concern: If a 255lph pump is max’ed out delivering enough fuel to support 400 hp at 10-psi boost it must not be able to supply enough fuel to support 400-420 hp at 18-psi!
So, I am thinking at high rpms the fuel pressure across the injectors must be dropping. The tuner of course would compensate for this by increasing the fuel injector duty cycle to keep the a/f ratio correct however the injector would be supplying the fuel at a reduced pressure causing the spray pattern to be less then ideal.
Now, if the fuel pressure is indeed low the fuel pressure regulator will have closed the return hose back to the fuel tank completely. Now when the car starts to accelerate there will be an additional pressure drop in the fuel line due to G forces that will reduce the fuel pressure even more. So, if the car was tuned on a dyno to the proper a/f ratio when going down the track the car will run lean. FYI, I burned a hole as big as my thumb in one of my Lightning’s Probe pistons due to loss of fuel due to acceleration, in that case there was not enough gas in the tank.
I can’t say this is a “real” problem or just a potensial one however it is an issue that someone could investigate and report on. BTW, there are a lot of Mustang speed shops that will not release a supercharged 400hp Mustang GT out of their shop without a 03-04 Cobra dual fuel pump fuel tank, something to think about…..
Cheers,
Charles
Also, thanks for your support: Magnum Powers’ Supercoupe sales have been quite good this year, thanks so very much!!!