This is topic Car bucking and jumping after supercharger install in forum Tech Talk at Northern California Ford Owners  .


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Posted by von89stang (Member # 7162) on :
 
Just put a Paxton supercharer (6psi) on my 87 speed density mustang 5.0. Also added a 12:1 fmu and a 190lph fuel pump. After I installed everything the car still ran perfect accept when under boost it started bucking and cutting out. Wondering if anyone knows what might be the problem. Thanks
 
Posted by 79 cobra (Member # 10137) on :
 
u need 2 convert it 2 mass air
 
Posted by von89stang (Member # 7162) on :
 
I want to keep this one speed density. And I have seen supercharged speed density ones before and they ran good. So I need suggestions for my setup not mass air setups.
 
Posted by Secnd2nun64 (Member # 1431) on :
 
Maybe the fuel injectors are clogged causing it to lean out. Maybe too much timing. You need to check your air fuel ratios to figure out whats going on.

Could also have a weak spark. You should look into getting a MSD box with the BTM.

[ October 03, 2010, 09:01 PM: Message edited by: Secnd2nun64 ]
 
Posted by von89stang (Member # 7162) on :
 
Thanks for the info man. I think I found the problem. I need a one way check valve for my map sensor.
 
Posted by copcar (Member # 10113) on :
 
quote:
Originally posted by von89stang:
Just put a Paxton supercharer (6psi) on my 87 speed density mustang 5.0. Also added a 12:1 fmu and a 190lph fuel pump. After I installed everything the car still ran perfect accept when under boost it started bucking and cutting out. Wondering if anyone knows what might be the problem. Thanks
If you have a 12:1 FMU and a 190 pump, what your engine is doing is lean surging. The pump can not handle that much of a pressure spike. You are dead heading it and your fuel mass is very low. Upgrade to a 255 or, if you plan on keeping the FMU you need to add a Trex inline. Let me explain. As fuel pressure increases, flow decreases. A 12:1 FMU is delivering 12 lbs of pressure for every one pound of boost (the stock FPR is 1:1) for s total of 13:1 fuel pressure increase. At 6lbs of boost, assuming your fuel system could handle it, (it can't) you would have a spike of 118 psi of fuel pressure (40psi+(6psi x 13:1 fuel pressure, return flow restriction, due to FMU) Your pump is not rated over 65 psi. In fact the flow at 65 psi is not much more than a stock pump at 40 psi.

[ October 04, 2010, 03:05 AM: Message edited by: copcar ]
 
Posted by Mach 5oh (Member # 9497) on :
 
That guy is smart.
 
Posted by RAP66 (Member # 3360) on :
 
Adding to what copcar posted

what did you gap your plugs to??

it's possible that your blowing them out.
 
Posted by 68dustin (Member # 5388) on :
 
what plugs are you running? im running my 302 with 8lbs of boost with autolights 3924 gapped at 25. When i first started i was having bad blow out problems

[ October 05, 2010, 11:30 AM: Message edited by: 68dustin ]
 
Posted by JohnB (Member # 969) on :
 
Layman's Terms: you need a bigger fuel pump.
 
Posted by Duncan Motors (Member # 7045) on :
 
all the basic superchargers at a stock 6 pounds in bolt on kits dont include a higher fuel pump. i know it should have a bigger one, but there doesnt seem to be a wide problem in that area till much higher boost levels.
 
Posted by von89stang (Member # 7162) on :
 
so i should throw a 255lph in it?
 
Posted by von89stang (Member # 7162) on :
 
autolite 24 i beleive and there at like 40 gap
 
Posted by Blind (Member # 3052) on :
 
quote:
Originally posted by von89stang:
so i should throw a 255lph in it?
I would first try a boost a pump.
 
Posted by von89stang (Member # 7162) on :
 
what is a boost a pump?
 
Posted by von89stang (Member # 7162) on :
 
i just saw what a boost a pump is and it is like double the price of a 255lph fuel pump.
 
Posted by von89stang (Member # 7162) on :
 
i just saw what a boost a pump is and it is like double the price of a 255lph fuel pump.
 
Posted by Blind (Member # 3052) on :
 
quote:
Originally posted by von89stang:
i just saw what a boost a pump is and it is like double the price of a 255lph fuel pump.
they're used to take the load off the intank pump, and they operate at a much higher pressure rating, this one from my buddy's shop for example is rated 300lph at 72.5psi

http://highflowfuel.com/i-4791020-bosch-044-300lph-inline-pump.html

[ October 06, 2010, 08:47 PM: Message edited by: Blind ]
 
Posted by copcar (Member # 10113) on :
 
That is not a "Boost-A-Pump." That is an inline pusher pump, like the T-rex I suggested in my earlier post. The "Boost-A-Pump" is a product marketed by Kenne Bell For the returnless setups which ramps up the voltage to the intank pump to meet the demands of a supercharged setup.

http://www.kennebell.net/accessories/boostapump/boostapump.htm
 
Posted by 50Reasons (Member # 6452) on :
 
Your lacking volume not pressure with the t-Rex you will get the volume of fuel needed and I do think you need a smaller gap then 40 in your plugs
 
Posted by copcar (Member # 10113) on :
 
Just to add to that, most setups run a .035 gap on the plugs but in a low boost situation .040 is about as wide as I would recommend. Your Spark plugs seem to be the least of your issues at this point however they are worth regapping.
 
Posted by RRRCobraSC281 (Member # 7086) on :
 
98 Cobra running .040 gap with T-rex 6# blower had issues with blowing out spark.

T-rex or get the larger fuel pump and shorten the gap.

Since it's the weekend, I guess all you can do is shorten the gap. See if it helps.

Robert
 
Posted by BOOSTED92GT (Member # 8650) on :
 
i having a similiar problem. anyone know where i can buy the fittings that clip into the fuel filter and go to a barb? i have a fuel pump already, but i dont want to cut lines up..
 
Posted by von89stang (Member # 7162) on :
 
What gap should I go with?
 
Posted by RAP66 (Member # 3360) on :
 
According to Bob Kurgan gap to .025 and you should be good.
 
Posted by 94 BLK 5.0 (Member # 9580) on :
 
BRO SOUNDS LIKE You NEED A TUNE
 
Posted by von89stang (Member # 7162) on :
 
I bet I do lol. Thanks for the info guys.
 




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