I recently posted hp #'s (342) on my truck. I also stated that I was running out of fuel at 4900 rpm's with 32lb injectors! So I ordered 42's ( I know their big) and now it's all I can do to drive the truck--detonation everywhere. Now granted, I haven't had the new chip burned yet, but wouldn't it seem that the motor would be running richer than leaner??? I have even tried hooking up the FMU (both 6:1 and 8:1 disks)with the Superchip as well as pulling out my current Superchip to see how it would run on the stock program. Regardless of what I do, it PINGS! It seems that everytime I have gone with bigger injectors the detonation gets worse. For example, when the supercharger was first put on (this was the only mod) I got slight detonation at the 1-2 upshift. I installed the 30's, and I noticed more detonation at the 1-2 upshift and slight detonation during normal driving. Now that I have 42's, I have to be real careful--detonation occurs with the slightest throttle response. Seems to me for my particluar application, the MAF and larger injectors have caused me nothing but grief! Could someone please tell me why I am running so lean?

Ron



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1999 Roush EC flareside, 4x2,Wedgewood Blue, 5.4, 4R100, Vortech
Supercharger producing 9psi, 4:10LS, PROM 80mm mass air meter, 30lb injectors, Superchip flipchip, Caltrac traction bars, 6 disc cd changer, Ford bedmat, ram-air hood.

 

This may not be the reasons why you are detonating, but these comments may jog you brain on what might actually be happening.
(I am brainstorming, trying to come up with any reason why this may be happening, so some may be far-fetched)

1) is your fuel pump adequate for the job? Is it going bad? Is it clogged somewhere? the biggest injectors in the world will not help if it can't be supplied with the fule it needs.

2) have you tried octane boosters to see if it would help? You may be getting plenty of gas, just not the right octane requirement (you may need better than 92 octane - though kindof doubtful)
also how many miles are on you truck? if it is a lot it may be part of the problem (as a truck gets more and more miles on it, its octane requirements go up.

3) are there any differences with the stock vs aftermarket injectors with regards to "impedance"? Injectors are sometimes classified as hi - or low impedance. If I recall correctly stock injectors are high impedance and some of the bigger aftermarkets are low impedance (could be wrong though).

If this is the case, maybe the computer is unable to "fire" these injectors correctly. As far as I know injectors are either "on" or "off" with the computer telling them how long to be "on" or "off" but maybe in this case, if there is a diff with "impedance" maybe they are only partially coming on.

4)Without a "chip" designed for your setup, the current settings may not be taking full advantage of the larger injectors.

Recommendation:
1) check the simple thing first. Throw some octane booster in your tank to see if it is a "lean" condition or an octane requirement issue.
2) check the fuel system - change the fuel filter, check to see if your pump is adquate for the job
at least then you will know for sure that these items are ok.

 

lutwiller,

Have you checked the fuel pressure at the fuel rail? If it is low you could install even larger injectors and still run out of fuel. The regulator may be damaged. Is there a trouble shooter included with the FMU? Is it working properly?

Check the plugs for fouling, hot spots, etc...

EGR all *******ed up, coming on too early or too strong, or even not enough.

MAF sensor not working properly, dirty.

Regards

Jean Marc Chartier

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00 F-150 XLT SC Flairside 4x4 4.6 w/5spd 3.55LSD
Warn XD9000i, skid plates, Draw tite class III,
Rancho RSX Reflex shocks,
BFG 285/75 R16 MTs,
Borla Cat Back, Headman Headers,
Modified Air Cleaner Outlet Tube
and air box, Ported Throttle body,
Shortened MAF sensor tower,
K&N air filter,
Superchips

 

Hi Ron,

Since we're doing the tuning on this for you, I would suggest that you give us a call, as it's been obvious with the A/F #'s you've got for the last 3 programs (12.8:1 @ WOT) that the truck is just not getting enough fuel. When it didn't respond to increased fuel injector pulse width, that's when we asked you to get the A/F numbers, and *that* told the story.

As others have mentioned, this could well be due to needing a larger capacity fuel pump to replace the factory in-tank pump, that is something that should be done anyway in any supercharged application. And it could be that these injectors are off in their calibration, as different brands of injectors do have different resistance values, etc.

What I would suggest is that you touch base with us, and let's go over every aspect of the fuel delivery system, including which injectors you have right now (the 42#'s) and their part numbers.

I would agree that on the surface at least, all else being equal, it is logical to expect to see more fuel delivery rather than less from the larger injectors; this tells us that either the injectors aren't delivering their rated capacity, or their rated capacity is at a higher fuel rail pressure than the stock units, or that the fuel delivery system isn't up to snuff elsewhere, like the factory fuel pump, which is a definite possibility at your power levels. Remember, that fuel pump was designed to supply the needs of that engine when stock.

This is a fuel-delivery issue, not an octane issue, so please, no octane boosters as they shorten the life of spark plugs and O2 sensors due to the pink & purple residues they leave behind, let's just take it by the numbers so to speak, and diagnose this properly.

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Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com
Performance Products F150Online Superchip ordering system: F150Online Superchip Ordering System
First National F-150 Online Rally Event Organizer

[This message has been edited by Superchips_Distributor (edited 02-18-2001).]

 

Hi Guys, Thanks for your input! After I wrote the post, I tried something. When we put the 42's on we also obviously put a newly calibrated MAF (for 42's) on as well.

So I pulled the new MAF off and installed the MAF calibrated for the 30's. I figured that if I was lean, I needed to fool the engine. Well, it worked. Detonation has dropped off dramatically. This of course is not permanent. However, it will allow me to drive conservatively until the problem is fixed.

Evidentally, my current programming is only allowing so much fuel regardless of injector size and increasing the calibration of the MAF is only making matters worse.

My problem now is putting the MAF calibrated to the 42's back on and getting the air/fuel numbers for Mike. I mean I already know it's going to be lean. I guess I will just have to make a pull until the condition gets to severe.

Thanks again for the help. What a great forum!!

Ron

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1999 Roush EC flareside, 4x2,Wedgewood Blue, 5.4, 4R100, Vortech
Supercharger producing 9psi, 4:10LS, PROM 80mm mass air meter, 30lb injectors, Superchip flipchip, Caltrac traction bars, 6 disc cd changer, Ford bedmat, ram-air hood.