QUESTION FOR PAXTON GUYS

[bigmike32172]

i picked up a 255gph fuel pump from cody at A.R.T and i noticed on the dyno that the fuel pressure drops from 55psi to 44psi after 4500 rpm. i am only using the in the tank fuel pump without using the 2 pumps that come with the paxton. i am also using the vec2 in place of the split second, and 60# injectors.
the pump obviously seems too small, so what pump should i use?

 

[2002_Viper_GTS_ACR]

Why didnt you just use the 2 that paxton supplies? They work great, and you dont need to go in the tank to install them ??

Jon

PS. if pressure is dropping that low, I bet you are also running way lean not good.

 

[johnk]

i picked up a 255gph fuel pump from cody at A.R.T and i noticed on the dyno that the fuel pressure drops from 55psi to 44psi after 4500 rpm. i am only using the in the tank fuel pump without using the 2 pumps that come with the paxton. i am also using the vec2 in place of the split second, and 60# injectors.
the pump obviously seems too small, so what pump should i use?

Uuhmmm,.

My stock Paxton installation does 85psi at ~3k rpm and hit the limit at 99.9 psi at about 5050 rpm. I'm too new to Vipers to address the duty cycle of the injectors, but 40-50 psi would scare me.. Good luck...

 

[bigmike32172]

hmmmm, i am a little confused. i was told by many if you run the vec2 to scrap the fuel pumps that paxton gives you and run a bigger fuel pump in the tank.

 

[Viper X]

Hey Mike,

I've been round and round with this. Not sure about the VEC II with a Paxton, I really don't have any expericne with it. The split second box is actually program-able and a very good piece in the right hands. I run an AEM with two external 400 LPH Bosch pumps and one internal high volume Walbro that keeps the fuel module full, but my car is a darkside Paxton car - over 1000 hp on pump gas.

I would need more info on your engine to help, but I would suggest you use the stock Paxton set up if your car is stock with only a Paxton. I think the two Paxton supplemental pumps are 250 LPH each, so you are not getting enough fuel. This is fairly obvious by your comments on fuel pressure. My fuel pressure is set at 67 psi, vacuum modulated down to 55 at idle. Under boost my Aeromotive fuel pressure regulator increases fuel pressure on a 1:1 ratio with boost, so at 10 psi, my fuel pressure it back up to 65.

Fuel volume is also important and again I would guess that the two pumps that come with the Paxton supply more volume too.

You didn't mention your Air/Fuel ratio's. What are they doing with increases in engine speed?

Be very careful with this or you could be rebuilding your engine.

Good luck,

Dan

 

[bigmike32172]

the A/F was hanging around 11/1 throughout the dyno. i'm thinking i got a bad dyno shop, although they are great with charging me money!

 

[big-n-italian]

the A/F was hanging around 11/1 throughout the dyno. i'm thinking i got a bad dyno shop, although they are great with charging me money!

hey, i had my car at one of those shops too!

you should have told me you were dynoing your car here in PEORIA, we would have gone out for beers!

 

[bigmike32172]

the A/F was hanging around 11/1 throughout the dyno. i'm thinking i got a bad dyno shop, although they are great with charging me money!

hey, i had my car at one of those shops too!

you should have told me you were dynoing your car here in PEORIA, we would have gone out for beers!

LOL! i guess there are quite a few of these shops around the country, where the owner of the shop buys a dyno and dumb people like us automatically think they know how to dial a car in properly.

 

[plumcrazy]

im pretty sure scraping the paxton pumps is a good thing regardless of what you use to tune it.

id talk to some of the VEC2 guys around here to find out more...

 

[bigmike32172]

ok, after talking with mike at paxton and dave at roe, they all told me to give dave weaver a call at A.R.T, which i did and he told me i was right about not using the split second box or booster pumps with the paxton. he did tell me that i should switch out the fuel line in the tank to a 3/8" line, i guess that is where the fuel is getting choked up.