I have just bought this truck and have not had the pleasure of working with a supercharged engine/computer before. I use to build circle track race engines but... No computer or charger in them, so any help would be greatly appreciated. This truck has the twin screw supercharger, a Kenne Bell chip, a Kenne Bell Boost-a-pump, a FMU and 24# injectors. When under load the fuel pressure jumps to 60psi and falls flat on its face. It should be an 8psi boost system but have yet to see anything over 2psi of boost. I am looking into taking out the FMU and Kenne Bell chip and installing the XCAL2 but my question is about the injectors. Do I need 36# or 40# injectors or can I get the 24# injectors to work?

 

your running out of fuel pump I bet... you need 42lb injectors, and id ditch that fmu.

 

The other thing I think I forgot to say was that when it falls flat... It blows black smoke out the back like as if it is loading up. I will definately get rid of the FMU. Is there any injector brands to stay away from? I am looking at 42# Venom injectors... any good? Thanks for the help!

 

What you have is a standard kit setup that works fine when there are no issues.
The fuel pressure is supposed to go up with boost on about a 10 psi to 1 blower psi rate..
However 60 psi and 2 pounds boost doesnt match up because an FMU with a 10 to 1 ratio boost means with 60 psi, your boost should be way more than 2 psi to cause the fuel pressure to go that high.
Either your boost gage is reading wrong, the belt is slipping, there is a leak or there is some other issue to sort out.
The black smoke is an over rich condition.
Maybe the original installation and owner had a problem you need to find, then it will run right.
I have been running the same type system on a 5L for more than 4 years without any issues on speed density yet.
Your not running out of fuel I can assure you, with a pump booster in the setup, going to 60 psi and running rich..
If you choose to go the reprogram route, larger injectors are needed as well as the mass air meter recalibrated to match along with a program change.
The pump booster will be fine with a new setup and will be needed if you don't replace the pump with a larger capacity unit.
IMO, unless you are bent on changing the whole system and the cost, straighening out what you have, will work good because the setup has been engineered to work as a kit install and go without dyno tuning.
The chip has also been optimized if it is a KB.
Lastly, KB errors on the safe side by being somewhat over rich with fuel and conservative with the tune, for obvious reasons.
I don't condem either way of handling a blower setup (FMU or reprogram) but will stand by an FMU as reasonable for the user who wants to install a setup and drive away with lots of power he puchused the blower kit for.
After all, the kits made available would not be sold in such a volume as a bolt on if it had to ALWAYS be dynoed, injectors changed, air meter recalibrated and PCM reprogrammed.
Just so you hear another experienced point of view to base your decision on.
Investigate Kenne Bell's website for tech info and the kit you have on your motor, for starters.
Good luck with it..

 

So the FMU is a part of the "kit" and not just a "Fix all" for another problem? Should the FMU stay in the system or should I take it out since it has the boost-a-pump in there? Do you run the FMU in your set up Bluegrass? Thanks for the help and I will start looking for the problem now. Thanks again....

 

I would think that if you check Kenne-Bell's site, they will certainly suggest at an 8# boost level to have 42# injectors, as 42# were standard on the 5.4 Lightning engines. To get the 24# injectors to work running their blower on this size engine requires a lot higher fuel pressure than what may be best and brings about other problems such as injector duty cyle, etc.

 

Awesome. So the Lightnings came with 42# injectors as a "standard" size. That helps out a lot. Would a set of Lightning injectors fit and fix my issues you think?

 

get a 90mm MAF, 255 lph intank fuel pump 42# injectors and a god tune

sounds like your fmu is set wrong and is making you go way too rich when you get into the boost. your truck needs to be tuned for the 24# injectors anyway since it came with 19#ers stock

I am running an FMU on my 2001 F-150 but I can't wait for a tune

 

The FMU and boost-a-pump is part of the kit. The 24# injectors might have been part of the kit too. Pull the plugs ans see what they indicate. It would guess that you are too rich at the top end judging from the black smoke. The boost-a-pump should adjustable. What is yours set to? I would recommend a wide band A/F gauge.

JMC

 

boost-a- pump is not adjustable I looked. Going to pull truck in the shop tonight and I will check plugs and post results of what I find.... Thank you

 

Did not have a lot of time to look but here is what I found last night... Boost-a-pump is definately not adjustable, but is hard wired right into the harness. Could not see any vac lines that were off or damaged. The belts are nice and tight around the horn. Found a part number on the injectors and it is #1536, which I have not found a match to anywhere on the internet to know what that injector is. The thing that throws me is that it starts right up and runs so good as long as you do not go to the boost side of the gauge. Looked at the Kenne Bell web site but could not find this problem on there. Going to try and give them a call today and see what I can find out but I am still looking for help in figuring out what this issue may be... Thank you

 

I just installed a Boost a Pump, and it is definetly adjustable. It has a rheostat for the adjustment, and a boost controlled switch on a vac line. Maybe one of these is missing, or incorrectly installed, which could be part of the problem with not running well in boost? Call KB tech and review with them

 

Might be it.... Vac line is not hooked up to boost-a-pump it is just crimped over. I will try to hook up adjustment and vac lines and see what I get then. Thanks

 

Isn't that neat! Just crimp it off and not use the booster!?&$
Ah don't need no stinkin pump booster, just run wit out one!!!!!
Beats me how people can just do those things and expect not to have problems.
My pump booster is also adjustable and boost driven for proportional control.
Makes no sense not to have control over these items for tuning purposes. It's to important.
Boost retard ignition contol works the same way on a regualar ignition system.

 

Maybe the previous owner hooked it up to a inconsistent vacuum/boost source and decided to crimp it to try and eliminate the problem. The best advice would be to go over the complete system to make sure it is installed correctly and then trouble shoot. Otherwise you could chase the symptoms only to discover that it was not properly installed.

JMC