I don't know, Eddy - I know next to nothing about A/C units.

Frank

Yes. Head pressure will rise in an overheat situation. Not sure if I'd trust the high pressure cut-out switch to keep it from damaging the system, though.

Two issues hopefully sorted today:

1) Installed a relay behind the glovebox to complete the A/C circuit. I now have full function of the condenser fan and compressor.... everything works as it should, with full designed protection. <img src="/forums/images/graemlins/kewl.gif" alt="" />

2) The tuning gremlin returned on my trip home from Atlanta. The last 20 miles I couldn't go over 55mph without the engine misfiring and bucking. Once again, AutoTune has been raising the VE table values under load and I noticed the 02 sensor reporting an unstable mixture.

I turned off MegaTune, restarted under an older .msq file to see if it would run correctly...... nope, not this time. Aha! AutoTune was telling me something by trying to call for more fuel. What was the issue? Was I once again having plug wire issues with the Magnecor wires that won't stay on the plugs, causing a misfire and giving the o2 sensor an off mixture? Could it be an exhaust leak before the o2 sensor? Or was there a fuel supply issue?

Yep, #6 was loose. Changed the plug wires to a cheap set of new ones...... better - no bucking, but now surging under increasing load. Manifolds were tight, as were the other exhaust connections. Fuel pressure was ok...... installed a new fuel filter, went for a drive and discovered new-found power with the engine flat-out screaming now. <img src="/forums/images/graemlins/kewl.gif" alt="" />

The ability to monitor the engine through MegaTune is a terrific diagnostic tool. Maybe that will clear up the tuning..... the gas that came out of the filter left a chalky residue when it evaporated.

Eddy, I think that may explain the surging we felt under full power.... just wasn't getting enough gas and not making full power.

Frank

I do not think you should be driving full time with auto tune on. The Wideband will adjust things fine as is and at this time should be narrowed down to 10 to 15% so it will not shut the engine down.
Running the drained fuel, I would consider carrying a spare pump. Just in case.
Have I mentioned I am not a Magnacore fan?

How much longer are you working down ATL way?

When I first started using AutoTune, I had the controller authority set to 50% - then 40% when I had it on the dyno. A couple of weeks ago, I reduced it to 10%, thinking that the closer I get the VE tables to "dead-on", the easier it will be for the wideband to adjust the mixture - and the faster and more accurate the adjustments would be. So, I made a few runs between Atlanta and Columbia at different speeds to get it dialed in. I think I'll now need to make another run to hopefully reduce the high VE values since the fuel issue is fixed (I think).

I don't know if I got a load of bad fuel, or if it's because the truck sat for a long time while the engine work was being done..... I also suspect the VR4 pump keeps the tank stirred up since it's moving a lot more fuel through the system now. A spare pump is not a bad idea - that little sock strainer can't take a lot of debris.... but maybe it passes the chalky stuff ok to the in-line filter.

Magnecor? I've had my last set of those.... they look nice, but don't stay on the plugs - particularly #6. I need to find another brand - maybe OE is best.

I'll be in Atlanta another couple of weeks - then perhaps to New Orleans, Nashville or Knoxville for a while - then maybe back to Atlanta. Grading is underway here...... but a lot of dirt still needs to be moved. I counted 29 heavy highway graders in use last week. <img src="/forums/images/graemlins/scared.gif" alt="" />

Frank

My thought on the pump is the unknown abrasiveness of that dust you found in the filter, long term wear on the pump thoughts.
Sounds like they hire Can do type contractors to get site work done.

As luck would have it, the property was bought from a very large grading contractor who is eager to get the job done. <img src="/forums/images/graemlins/lol.gif" alt="" />

You are probably correct about possible abrasiveness of the chalky residue that clogged the filter. So far though, fuel pressure holds very well against the pump after the engine is shut down.

I'm eager to see how the engine runs on the trip to Atlanta tomorrow.... and if AutoTune will now reduce the VE values above 100kpa.

Frank

Good to know it's running better. I'll have to buy your lunch again one of these days, if you're back in ATL.

I like NGK wires.

Ya know, I thought about fuel starve when I felt it, but was too stupid to say anything, after you got my mind all wrapped up in cam crazy again. Camthink hurts my head for some reason...

Do you have knock sense enabled, and what retard does it throw if it is? That can cause the same surge as the retard reduces power, then the new advance cycle gives it back. Or it could be just the power lean out when it hit the flow limit.

How does the exhaust soot look now?

Thinking about the dust in the filter, that may be normal for unleaded fuel. The old days leaded fuel left a varnish when it dried but todays fuel is dusty. The unleaded race fuel I run has a fair amount of heavy particulate that needs to be strained before going in the car.

Eddy, yes - Knocksense is enabled at 6* IIRC. However, I have an LED on the gauge pod that should light on knock detection and it's never barked at all... so I don't think it's hearing anything. Neither do I. I do have the spark table written to reduce spark lead as boost increases, so there's probably enough retard to cover the issue.

The test drive after changing the filter suggests it was a fuel flow issue..... In "D", the transmission is even holding gears longer now on full throttle acceleration.

It's too early to tell anything about the exhaust, but the engine startes smoother and idles better. I'll know more later today.

Frank