I was just on my way home, and stopped to get some food. When I got back in the truck, I drove a few miles in traffic, and noticed that my engine started making a pretty loud noise. It sounded like an old carbarated v8... but it's a vortech supercharged 5.4 It was not ticking or knocking at idle, or low rpm, but when I accelerated, it got pretty loud, and louder with more gas. I pretty much idled it home, and hooked up my predator tuner, to read any codes. I got the Knock sensor bank 2 code... and I checked the drivability in the data logging, and my LONG TERM FUEL TRIM 2 was reading at negative 2% and the LONG TERM FUEL TRIM 1 was at about 17%, so I'm not sure what they mean, but are they supposed to be different? What should I do? Is this a fuel system problem, or can I retard the timing a few degrees with the tuner? I still have the stock injectors, and Vortech FMU, and I am supposed to have my guy install the 42 injectors and lightning MAF, this weekend. HELP!!!! ADVISE PLEASE!!! -rob

 

Post in the chip section. If you got the tuner from Troyer, he might give you an answer.
I have thoughts but won't advance them unless you can't get an answer any other way.

 

I already posted over there.. and no responce yet. I did not get my tuner from MT, as it is a Diablosport Predator tuner. I restored the stock tune to my truck, and it made no difference. Let me know Blue. Thanks -Rob

 

17% is a lot of fuel for a long term trim. Fuel trims are basically a measurement of how much fuel the PCM is adding to try to bring things back to as close to a stoichometric mixture as it can. Typically, short term trims should be switching lean to rich close to 0% (short term trims are what make the upstream O2s switch) and they allow up to 20% on the long term trims, but anything more than 10% correction on the long terms, I want to know why. The short term trims can compensate so much, but eventually long term fuel trims will step in and adjust accordingly so the short terms can go back to switching around 0%.

For whatever reason, you're running lean on bank 1 (hence the 17% + long term trim, the PCM got tired of short term trims trying to make things right, so long term came in and jacked fuel up). You've got a lot of variables thrown in with the blower, stock fuel system, and FMU. With the blower, you're pushing a lot more air into the engine than it was originally intended to handle, and the PCM is trying to adjust to that. Someone better versed in tuning supercharged applications can give you better info than I can. FWIW, what were your short term fuel trims reading? Were the upstream O2s switching? And what were the downstreams reading?

ETA - Your long term trim on bank 1 is probably a result of the knock sensor reading. The KS was probably seeing a lot of ignition knock and richened things up until it went away.

Edit again - If it were mine, I'd back the timing off a few degrees, get a full tank of the best fuel I could find (93 oct or better), clear the keep alive memory (I dunno if your tuner can do this; if not, disconnect the battery and flip the headlight switch on for five minutes or so), and take it for a highway run to reset the fuel trims.

 

It could be a bad injector causing all your problems. With all those mods, you're going to need a custom program from diablo. I wouldn't run stock out of the box program with all those changes. Call diablo, er your local dealer, and tell them what you have. They'll design a program based on your truck and its mods and you can either download it, or get it downloaded at the local diablo dealer. I have done the smae thing with my Nav. Problem with mine is that everythinng has to be 100% custom, as no one has ever done it before. WIth yours, they'll have a base and can turn it out faster!

 

This is exactly why I didnot want to try to answer.
There are to many unknowns with his setup.
How much boost?
What is the FMU ratio?
How long has the blower been on?
What gas is being used?
Did it ever run correct etc.

 

It ran perfect for the last few months. It's running about 10 psi. The FMU is straight out of the Vortech box. I have a new set of 42 injectors and a lightning maf, and they should be getting in this weekend, with a fresh dyno tune. Now I just have to figure out how to get the truck to the shop. Also, I recently added an autometer a/f guage. I tapped the signal wire into the o2 sensors black signal wire. Is there any way that this could be sending a bad signal, and causing this problem?

 

I still can't suggest what the problem might be from what you give.
Sounding like a carbed engine in not helpful.

The A/F gauge you are using is really of limited value and only can indicate what direction the fuel ratio is taking.
A wide band gauge is the only full time way to see how rich/lean the fuel is going.

Next, you can't use an FMU with 42 lb injectors (way too rich).
You may need a larger fuel pump with the bigger injectors and remove the FMU..
The reason is the larger injectors will fuel the engine at the rated fuel pressure without using an FMU.
The fuel volume needs to be increased with a larger pump. An FMU doesnot do this. As an FMU increases the fuel pressure, the pump's volume goes down in an inverse relationship.
My position is to sort the problem out and leave your blower fuel system as it is, but doing a tune. I know there is firm school of thought that FMU control is old and considered much less than fitting in todays world but it works fine for general use applications. Most blower vendors can't offer there units to the general public with out offering/using an FMU for quick installation that every one wants to do.
Here is the standard way to figure injector size using a BSFC # of .55 for blower application..
42 x .8 / .55 = 61 hp per inj. x 8 = 488 hp.
If you have the 3 valve motor then this size injector may be fine but possiblely on the large side if 'not' a 3 valve motor or a 4.6L.

I offer these comments because you combined two areas in your thread, a problem and re-tuning the engine.
Just to be sure you know what else there 'may' have to be included with the changes.
As a start on figuring out the problem, I would remove the blower belt so the engine can be run without it and begin fault locating until or unless this implicates the blower as contributing to the problem.

Lastly, I run a Kenne Bell on FMU for the last 3 years so that insight has been brough to you as well as a couple centrifigal systems with larger injectors and no FMU, as reference for experience.
Please excuse me if i have assumed to little of your position.
Good luck.

 

I understand what youre saying. I know that I am supposed to remove that FMU, if I plan on upgrading the injectors and MAF. I have a Vortech T-rex fuel pump to help out with the pushing, and even a few lighting pumps laying around.
As it turns out, my problem was a little more complicated than I expected. That noise was not pinging or detonation even. It was the subtle sound of the piston slamming into that soft aluminum head.
Luckily for me, my friend has a brand new engine out of a lightning that he has had sitting around since 02, the year my truck is. He builds trucks. We have a big expensive project ahead of us... or he does. I'm just cutting the check. I will try and help him out, as I would like to see everything torn down. Such is life.
-Rob

 

Ok Rob, sounds like your under control.
Thanks for the reply and good luck.