6.0 LQ4 not reving past 4800.

[6.0S10]

Here you go doc. One log file.

[mowton]

Does the speedo work correctly? The tire size says 9.5 and the VSS sensor data is like twice what it should be....like if the tires were say 18, then the sensor data would be moe in line? Did you change them deliberately. In sert the correct tire height in the Gear/Tire Wizard (in Edit) and see if that corrects it.

Ed M

[6.0S10]

Here's what I learned yesterday. I did a full throttle run. It went past 4800 on up to 5200. The only way it went smoothly past 4800, was to slowly progress the throttle as rpm increased, eventually to WOT. Return to normal rpm, did a WOT and it acted stupid again.

I haven't changed the tire size or gear settings, it was part of the original tune. Gears are 3.73 and the tires are 32".

The speedometer is 3mph slower than the scanner, and the scanner is 11mph faster than the actual speed. GPS and used my other truck to check.

[6.0S10]

So something everyone should do including my self. NEVER SKIMP ON PARTS!!!!!!

My issue has been solved on the 4800rpm limit. It wasn't actually a limit as it was a problem. After hours and hours of data logging and watching the replay of the data logs, I noticed that the MAF signal would just drop off like a closed throttle. Everything else was working, signals were right on que from various sensors and programming wasn't far off. I made no changes to the engine structurally. Only changes to the platform were necessity like, headers and intake duct work. After finding wiring problems from the harness builder, those were corrected and changes were starting to be noticed. Still shouldn't be a complete engine top end plane like I was having. I removed the complete front clip, almost required to do on a 4WD S10 to do any lower work, removed headers and checked exhaust system for leaks, pinched fuel lines, fuel regulator problems and anything you could think of from here on out.

When putting it all back together and contemplating on its sale price, I noticed one small detail. I realized there was nothing wrong with my engine. But the thing that was causing my nightmare was one of the most ignorant thing to have ever done in the first place.

It all started like this,

I put and LS1 in it the first time, nightmare on getting it tuned because the intake air temperatures were ridiculous. The throttle body mounted air cleaner was drawing the hot air straight from the radiator. THIS IS A SHOW ONLY PIECE!!! NOT FOR ANY PERFORMANCE!!
So I moved it to a different location in the engine bay, into factory air box location. I reused the filter unit, but used silicone hose for intake duct. This setup worked fine, temps dropped and tuning went smoothly.

Now I swapped motors simply because the LS1 didn't have the consistent low end torque to haul my toys or my tractor and any heavy hauling I needed to do. So I opted for an excellent deal on a low mileage LQ4. Less than $1k deliver thru eBay. I made several change to my set up in the process of the swap. ALL, and I do mean ALL my changes were 100% perfect for the application.

The one change I didn't make, was the intake duct system. This is where the serpent showed its head. The silicone hose has been the problem all this time. Under full throttle the hose was collapsing. I thought the 3" diameter would do the trick, but when the temps rise it was heating the hose making it softer, thus in the end was collapsing under the vacuum of WOT. I finally noticed this as I was reving the engine after I removed the intake system. I had my and a little to close to the TB and when I cracked the throttle, well it sucked my hand right on to the front of it.

I knew right then where and what the problem was.

Solution:

I took a factory air box and modified it to fit in the remaining factory location, alternator on Corvette drive is in the way, and cut larger holes in the radiator support. Then fastened it to the support, being able to use the factory style filter, for serviceability, and forced cooler air from head wind of travel. I then run 3.5" aluminium turbo tube from the box lid to the TB. I also learned that ALL MAF perform the absolute best with a straight line of flow. Not mounted next to any elbows or reducers. This detail is imperative for optimum signals and tune ability.

I have to give credit to DynoSpeed Racing in Memphis, TN for their advice on the MAF location and helping me at all. A lot of people start to help and then walk away or just in it for the money.

Dyno day is Monday at DynoSpeed for some fine tuning. Since the corrections have been made, I have been able to get my LTFT to within 1% and my STFT to within 3%. I need their wide band setup to do WOT tuning and get some numbers on paper.

Thanks to everyone for the blind help. I know how difficult it can be to do any type of mail order or blind tuning.

[6.0S10]

Photos of my setup.

[6.0S10]

Not bad for a first time tune. My tune is the blue line, dyno shop is the green line. 300.86hp and 335.15tq at the ground. Next is a set of AFR heads and a supercharger. Thanks everybody for the help.

[5FDP]

Now I wouldn't tell you how to spend your money but buying those heads would be a waste of money.

Just buy a set of 243/799's and have them worked and you will be in the same ball park as a set of AFR heads. With the power output this motor makes you aren't spending the money right. You will never be able to use a set of AFR to the max and be disappointed. $2,300+ for a set of heads is crazy talk to me, spend that money on something else that will make this engine more powerful or reliable.