4.6 DOHC Cutting out - Mustang Boards


Power Adders Technical discussions for forced induction with nitrous and blowers.

Reply
 
 
 
Thread Tools Search this Thread
  #1  
Old 05-04-2012, 08:28 AM
Junior Member
Thread Starter
 
Join Date: May 2012
Location: Houma, Louisana
Posts: 2
Default 4.6 DOHC Cutting out

I have a 97 Cobra 4.6 with Paxton supercharger, it was dynoed @ 486 rwhp @6000
It is very strong, but it wants to cut out and backfire when I get into the throttle. The problem starts @4500 on up. I have changed the fuel filter and fuel pump, same issue. The problem seems to get less as the engine warms up. I'm running 10lbs of boost @ 30 psi fuel pr. Any suggestions would be appreciated.
Reply With Quote
  #2  
Old 05-04-2012, 01:38 PM
Junior Member
 
Join Date: Apr 2012
Posts: 1
Default

what gap do you have on the spark plugs? you may need to close it up. Not to uncommon to get spark blow out on a boosted car. our turbo car has the plugs closed up to .028. The fuel press also seems low to me what size inj. are you running and what are the AF ratios?
Reply With Quote
  #3  
Old 05-04-2012, 03:13 PM
Senior Member
 
Join Date: Nov 2004
Location: Pinole, Ca
Posts: 3,842
Default

For 10lbs you want to run a .032-.035 gap. Either NGK TR6 plugs or BR7EF plugs will work just fine.

Why only 6k? They should be pulling the car to 6700-6800 rpms? Maybe add a smaller pulley so you can use the entire range of RPMs.

If the car is backfiring that is detonation and needs to be corrected in the dyno tune. If you continue to beat on the car the stock rods will break or you will melt a piston for sure.

Give us the mods you have that support the superchager. IE fuel pump, inline fuel pump, injectors, MAF, intercooled, aftercooled, powerpipe, blower pulley size. Stock long block or has it been forged?
Reply With Quote
  #4  
Old 05-04-2012, 05:52 PM
TUFF 4.6's Avatar
"Just Add Foot"
 
Join Date: Dec 2007
Location: Richmond Va.
Posts: 2,250
Default

As said above more details please, did this just start or has it been ongoing? and yeah 30 lbs seems way low on a boosted motor.

PS make sure you have an aligator stuck in the air intake
Reply With Quote
  #5  
Old 05-07-2012, 07:57 AM
Junior Member
Thread Starter
 
Join Date: May 2012
Location: Houma, Louisana
Posts: 2
Default

Some of the mods are: Forged pistons 8.5:1, H beam rods, adj fuel reg, hd main bolts, long tube headers, BBK Cats, 42 lb injs, 255 lph fuel pump, NGK TR6 plugs, 90mm Mass air meter, BBK 62mm throttle body. This is a car I just bought, so I don't know if this just started or is on going. I tried a new fuel pump with no difference. The engine has a surge @idle, not real bad but noticeable. I have a dyno scheduled for the 21st of this month. The car has been sitting around for the last 8 years. They only put 3000 miles since the upgrades whiche were done in 04.
Reply With Quote
  #6  
Old 05-07-2012, 10:23 AM
Senior Member
 
Join Date: Nov 2004
Location: Pinole, Ca
Posts: 3,842
Default

That motor will make a lot of power once its properly tuned!

Not sure if those 42# injectors will keep up. I've seen some people get them to work in the 550 range but 500-520 is about the max to keep the duty cycle in the 80% range.

Also, your fuel system will be labored as well. Check out SVTP and read up in the blower bistro for fuel system upgrades on 98 cobra's. You have a return style system, which is great, but I think you need more pump to handle the power that this motor and blower is capable of.

Since the car is making 10#'s at 6k I will take a stab that it has a pulley that will make about 15#'s at 6700-6800 rpms. If it makes that kind of boost your car should be in the 540-550 range in horsepower.
Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
idle problems and cutting out my87gthaha 5.0L Tech 3 07-01-2012 08:10 AM
2001 navigator dohc longblock or part out the12fast4u Mustang Classifieds 5 12-29-2010 06:57 AM
cutting out tryinghard V6 Tech Forums 2 07-22-2006 03:25 AM
Mustang Keeps Cutting Out ProShifterGT 5.0L Tech 3 05-24-2005 01:04 PM
Car Keeps Cutting Out ProShifterGT General Tech Forum 10 05-24-2005 12:59 PM


Tags
46, 80, 97, backfire, builds, clicking, cobra, cuts, dohc, engines, fuel, low, mustang, pounds, power, pressure, surge

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -7. The time now is 12:53 PM.