Vortech supercharged '98 4.6 cobra problems
09-15-2008, 05:00 PM
#1
Thread Starter
Join Date: Sep 2008
Location: ct
Posts: 5
Vortech supercharged '98 4.6 cobra problems
I just installed a vortech supercharger kit on this 98 mustang cobra (4.6 4v.) The kit came with a t-rex pump. Fuel pressure was only getting to 55 psi in full boost when it should be ~120psi (claimed by vortech) and was fluttering badly.
The stock fuel pump uses a venturi to suck fuel into the surge tank, so if it cant keep pressure on the inline pump (sucking on it) it will not have the necessary pressure to make the venturi work and the surge tank gets sucked dry. The gas tank is 3/4 full too.
We changed the stock fuel pump to a new one. Now we are getting to a solid 80psi of fuel pressure in boost. Its still 40psi low from what vortech says it should run. Strange thing is with the engine off and pumps running we can get the fuel pressure over 100psi with air pressure on the FMU. Both fuel pumps have a relay on them to the battery thats 1 foot away in the trunk, each read 13.8 volts when running.
The trex is only rated to 85 psi. I believe the stock pump/surge tank is the issue.
Power seems to be maybe 350hp. It pulls ok untill about 5000 rpm and gets very flat. Ive tuned a lot of turbo cars, im pretty much positive its lean. No wideband in the car to confirm this.
Vortech is fairly clueless about why the fuel pressure is low. They are offering to test the FMU and the trex pump. Not looking to wait 2 weeks to hear both are ok. Youd think they would have a better idea whats going on.
Anyone had issues with the surge tank/stock pump and an inline pump not making ~500hp worth of fuel flow?
I built a turbo escort zx2 that had this exact surge tank setup. I spent hours modding the surge tank so it would work with a walbro 255lph pump and the venturi surge tank headache. The walbro didnt have the flow to deal with the venturi and the engines flow needs. I ended up hacking big windows in that surge tank eliminated the venturi and the walbro pump could finally make enough flow for the engine.
Any ideas or BTDT are much appreciated!!!
The stock fuel pump uses a venturi to suck fuel into the surge tank, so if it cant keep pressure on the inline pump (sucking on it) it will not have the necessary pressure to make the venturi work and the surge tank gets sucked dry. The gas tank is 3/4 full too.
We changed the stock fuel pump to a new one. Now we are getting to a solid 80psi of fuel pressure in boost. Its still 40psi low from what vortech says it should run. Strange thing is with the engine off and pumps running we can get the fuel pressure over 100psi with air pressure on the FMU. Both fuel pumps have a relay on them to the battery thats 1 foot away in the trunk, each read 13.8 volts when running.
The trex is only rated to 85 psi. I believe the stock pump/surge tank is the issue.
Power seems to be maybe 350hp. It pulls ok untill about 5000 rpm and gets very flat. Ive tuned a lot of turbo cars, im pretty much positive its lean. No wideband in the car to confirm this.
Vortech is fairly clueless about why the fuel pressure is low. They are offering to test the FMU and the trex pump. Not looking to wait 2 weeks to hear both are ok. Youd think they would have a better idea whats going on.
Anyone had issues with the surge tank/stock pump and an inline pump not making ~500hp worth of fuel flow?
I built a turbo escort zx2 that had this exact surge tank setup. I spent hours modding the surge tank so it would work with a walbro 255lph pump and the venturi surge tank headache. The walbro didnt have the flow to deal with the venturi and the engines flow needs. I ended up hacking big windows in that surge tank eliminated the venturi and the walbro pump could finally make enough flow for the engine.
Any ideas or BTDT are much appreciated!!!
09-15-2008, 08:13 PM
#2
3rd Gear Member
Join Date: Aug 2008
Location: Oklahoma
Posts: 912
I just installed a vortech supercharger kit on this 98 mustang cobra (4.6 4v.) The kit came with a t-rex pump. Fuel pressure was only getting to 55 psi in full boost when it should be ~120psi (claimed by vortech) and was fluttering badly.
The stock fuel pump uses a venturi to suck fuel into the surge tank, so if it cant keep pressure on the inline pump (sucking on it) it will not have the necessary pressure to make the venturi work and the surge tank gets sucked dry. The gas tank is 3/4 full too.
We changed the stock fuel pump to a new one. Now we are getting to a solid 80psi of fuel pressure in boost. Its still 40psi low from what vortech says it should run. Strange thing is with the engine off and pumps running we can get the fuel pressure over 100psi with air pressure on the FMU. Both fuel pumps have a relay on them to the battery thats 1 foot away in the trunk, each read 13.8 volts when running.
The trex is only rated to 85 psi. I believe the stock pump/surge tank is the issue.
Power seems to be maybe 350hp. It pulls ok untill about 5000 rpm and gets very flat. Ive tuned a lot of turbo cars, im pretty much positive its lean. No wideband in the car to confirm this.
Vortech is fairly clueless about why the fuel pressure is low. They are offering to test the FMU and the trex pump. Not looking to wait 2 weeks to hear both are ok. Youd think they would have a better idea whats going on.
Anyone had issues with the surge tank/stock pump and an inline pump not making ~500hp worth of fuel flow?
I built a turbo escort zx2 that had this exact surge tank setup. I spent hours modding the surge tank so it would work with a walbro 255lph pump and the venturi surge tank headache. The walbro didnt have the flow to deal with the venturi and the engines flow needs. I ended up hacking big windows in that surge tank eliminated the venturi and the walbro pump could finally make enough flow for the engine.
Any ideas or BTDT are much appreciated!!!
The stock fuel pump uses a venturi to suck fuel into the surge tank, so if it cant keep pressure on the inline pump (sucking on it) it will not have the necessary pressure to make the venturi work and the surge tank gets sucked dry. The gas tank is 3/4 full too.
We changed the stock fuel pump to a new one. Now we are getting to a solid 80psi of fuel pressure in boost. Its still 40psi low from what vortech says it should run. Strange thing is with the engine off and pumps running we can get the fuel pressure over 100psi with air pressure on the FMU. Both fuel pumps have a relay on them to the battery thats 1 foot away in the trunk, each read 13.8 volts when running.
The trex is only rated to 85 psi. I believe the stock pump/surge tank is the issue.
Power seems to be maybe 350hp. It pulls ok untill about 5000 rpm and gets very flat. Ive tuned a lot of turbo cars, im pretty much positive its lean. No wideband in the car to confirm this.
Vortech is fairly clueless about why the fuel pressure is low. They are offering to test the FMU and the trex pump. Not looking to wait 2 weeks to hear both are ok. Youd think they would have a better idea whats going on.
Anyone had issues with the surge tank/stock pump and an inline pump not making ~500hp worth of fuel flow?
I built a turbo escort zx2 that had this exact surge tank setup. I spent hours modding the surge tank so it would work with a walbro 255lph pump and the venturi surge tank headache. The walbro didnt have the flow to deal with the venturi and the engines flow needs. I ended up hacking big windows in that surge tank eliminated the venturi and the walbro pump could finally make enough flow for the engine.
Any ideas or BTDT are much appreciated!!!
09-16-2008, 11:18 AM
#3
Thread Starter
Join Date: Sep 2008
Location: ct
Posts: 5
Yeah. First thing i did was go blow donuts across the street when i started it. 
Never said i was beating on it... Me saying power feels about 350 meant its way low for where it should be. Ive gradually gotten into more and more boost untill it flattened out. Once i felt the flat spot i stopped driving it. Its a customers car. Because of vortech's partially halfassed kit and lack of help on why their kit just wont make fuel pressure his bill got high pretty quick. I'd like for him to get a wideband but i cant keep throwing add ons on his bill. Buying a kit from a reputable company you'd think it would work how it should if installed right, no?
We decided to put a walbro in the old surge tank with windows in it. He will just have to keep at least 1/3rd tank of gas if he wants to beat on it.
Never said i was beating on it... Me saying power feels about 350 meant its way low for where it should be. Ive gradually gotten into more and more boost untill it flattened out. Once i felt the flat spot i stopped driving it. Its a customers car. Because of vortech's partially halfassed kit and lack of help on why their kit just wont make fuel pressure his bill got high pretty quick. I'd like for him to get a wideband but i cant keep throwing add ons on his bill. Buying a kit from a reputable company you'd think it would work how it should if installed right, no?
We decided to put a walbro in the old surge tank with windows in it. He will just have to keep at least 1/3rd tank of gas if he wants to beat on it.
09-16-2008, 11:23 AM
#4
3rd Gear Member
Join Date: Aug 2008
Location: Oklahoma
Posts: 912
Yeah. First thing i did was go blow donuts across the street when i started it.
Never said i was beating on it... Me saying power feels about 350 meant its way low for where it should be. Ive gradually gotten into more and more boost untill it flattened out. Once i felt the flat spot i stopped driving it. Its a customers car. Because of vortech's partially halfassed kit and lack of help on why their kit just wont make fuel pressure his bill got high pretty quick. I'd like for him to get a wideband but i cant keep throwing add ons on his bill. Buying a kit from a reputable company you'd think it would work how it should if installed right, no?
We decided to put a walbro in the old surge tank with windows in it. He will just have to keep at least 1/3rd tank of gas if he wants to beat on it.
Never said i was beating on it... Me saying power feels about 350 meant its way low for where it should be. Ive gradually gotten into more and more boost untill it flattened out. Once i felt the flat spot i stopped driving it. Its a customers car. Because of vortech's partially halfassed kit and lack of help on why their kit just wont make fuel pressure his bill got high pretty quick. I'd like for him to get a wideband but i cant keep throwing add ons on his bill. Buying a kit from a reputable company you'd think it would work how it should if installed right, no?
We decided to put a walbro in the old surge tank with windows in it. He will just have to keep at least 1/3rd tank of gas if he wants to beat on it.
09-16-2008, 04:30 PM
#5
Thread Starter
Join Date: Sep 2008
Location: ct
Posts: 5
Talked to vortech again. They said mid 80's for fuel pressure. How did 3 of 4 techs not know this? All said the FMU was a 8:1 regulator on top of stock fuel pressure so 120psi was expected...
I put a walbro 255lph in tank and bypassed the venturi junk. I cut windows in the surge tank to let the fuel in. Fuel pressure is up at idle a couple psi and up 5 psi in boost. It gained maybe 30-40 hp from this but its still breaking up pretty bad.
Not sure what you mean by a non returnless pump, do you mean the ones they use with PWM to make fuel pressure? It has a fuel pressure regulator and a return line. It works fine with the walbro in tank, fuel pressure is where it should be.
Taking it to the dyno in a couple days to see whats going on.
I put a walbro 255lph in tank and bypassed the venturi junk. I cut windows in the surge tank to let the fuel in. Fuel pressure is up at idle a couple psi and up 5 psi in boost. It gained maybe 30-40 hp from this but its still breaking up pretty bad.
Not sure what you mean by a non returnless pump, do you mean the ones they use with PWM to make fuel pressure? It has a fuel pressure regulator and a return line. It works fine with the walbro in tank, fuel pressure is where it should be.
Taking it to the dyno in a couple days to see whats going on.
09-16-2008, 04:46 PM
#6
3rd Gear Member
Join Date: Aug 2008
Location: Oklahoma
Posts: 912
Talked to vortech again. They said mid 80's for fuel pressure. How did 3 of 4 techs not know this? All said the FMU was a 8:1 regulator on top of stock fuel pressure so 120psi was expected...
I put a walbro 255lph in tank and bypassed the venturi junk. I cut windows in the surge tank to let the fuel in. Fuel pressure is up at idle a couple psi and up 5 psi in boost. It gained maybe 30-40 hp from this but its still breaking up pretty bad.
Not sure what you mean by a non returnless pump, do you mean the ones they use with PWM to make fuel pressure? It has a fuel pressure regulator and a return line. It works fine with the walbro in tank, fuel pressure is where it should be.
Taking it to the dyno in a couple days to see whats going on.
I put a walbro 255lph in tank and bypassed the venturi junk. I cut windows in the surge tank to let the fuel in. Fuel pressure is up at idle a couple psi and up 5 psi in boost. It gained maybe 30-40 hp from this but its still breaking up pretty bad.
Not sure what you mean by a non returnless pump, do you mean the ones they use with PWM to make fuel pressure? It has a fuel pressure regulator and a return line. It works fine with the walbro in tank, fuel pressure is where it should be.
Taking it to the dyno in a couple days to see whats going on.
09-16-2008, 05:16 PM
#7
Underboss
Join Date: Jan 2006
Location: Helaware
Posts: 20,273
I am almost certain this applies to the 98 Cobra also
https://mustangforums.com/forum/show...92&postcount=8
https://mustangforums.com/forum/show...92&postcount=8
09-17-2008, 12:50 PM
#8
Thread Starter
Join Date: Sep 2008
Location: ct
Posts: 5
Yeah, I know about keeping the tank on the full side to keep it alive. Customer will definitely be told about this. Does the 97 & earlier tank have baffles or something to help fuel starvation?
Last time i talked to vortech they asked if we closed the plug gaps down to .032, they were at .052 Doing that solved all the problems. I logged the rpm, O2 voltage and maf signal through the obd-ii port. All looks good now. Power feels where it should be too. Oh and fuel pressure does go to 120psi or more in full boost. Ridiculous!
I dont believe the stock pump with the surge tank/venturi would keep the t-rex inline pump fed well enough once this thing needed all the fuel. I did notice an improvement switching to the walbro before it could even get into full boost.
Thanks everyone for your input.
Last time i talked to vortech they asked if we closed the plug gaps down to .032, they were at .052 Doing that solved all the problems. I logged the rpm, O2 voltage and maf signal through the obd-ii port. All looks good now. Power feels where it should be too. Oh and fuel pressure does go to 120psi or more in full boost. Ridiculous!
I dont believe the stock pump with the surge tank/venturi would keep the t-rex inline pump fed well enough once this thing needed all the fuel. I did notice an improvement switching to the walbro before it could even get into full boost.
Thanks everyone for your input.
09-17-2008, 01:36 PM
#10
3rd Gear Member
Join Date: Aug 2008
Location: Oklahoma
Posts: 912
Yeah, I know about keeping the tank on the full side to keep it alive. Customer will definitely be told about this. Does the 97 & earlier tank have baffles or something to help fuel starvation?
Last time i talked to vortech they asked if we closed the plug gaps down to .032, they were at .052 Doing that solved all the problems. I logged the rpm, O2 voltage and maf signal through the obd-ii port. All looks good now. Power feels where it should be too. Oh and fuel pressure does go to 120psi or more in full boost. Ridiculous!
I dont believe the stock pump with the surge tank/venturi would keep the t-rex inline pump fed well enough once this thing needed all the fuel. I did notice an improvement switching to the walbro before it could even get into full boost.
Thanks everyone for your input.
Last time i talked to vortech they asked if we closed the plug gaps down to .032, they were at .052 Doing that solved all the problems. I logged the rpm, O2 voltage and maf signal through the obd-ii port. All looks good now. Power feels where it should be too. Oh and fuel pressure does go to 120psi or more in full boost. Ridiculous!
I dont believe the stock pump with the surge tank/venturi would keep the t-rex inline pump fed well enough once this thing needed all the fuel. I did notice an improvement switching to the walbro before it could even get into full boost.
Thanks everyone for your input.