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Need LS2 help for Lands End Right Now!

3K views 30 replies 13 participants last post by  SuperRanger 
#1 ·
We need some Turn Key LS2 help for the race this weekend on Bill Kunz Torchmate Jeep. We practiced at 4700 feet and loaded up. Unloaded at 6800 and it won't run. Runs ok with no load, not drivable with a load. Idles ok but needs to be featured to bring rpm up. We are Ford guys. Help!
 
#14 ·
Doesnt sound like an IAC if it wont run above idle. Check your connectors on your crank sensor and cam. Crank sensor tucked up behind the starter. Any idea what your fuel pressure is? All the coils firing? Those marine computers run fat at altitude , but should not be giving you the problems you are discribing.
Too bad TurnKey likes that damn MEFI crap.
Yep, I run the MAF and 2 o2's. Had it at 9000 to 11,500 last weekend and it still rips!
 
#16 ·
If your runing SD and going that high try truning the motor off for a little while at that alttuide then restart. I should then run fine. I have heard of problems with SD and high alt. That my fix it was the PCM will relearn the alt via the MAP sensor. But adding a MAF might help fix the problem as well.
 
#19 ·
Partially correct. What may cause these problems is starting quickly after ignition power on and not giving the MAP sensor and PCM a chance to reset to a new baseline. In this case, turn it off. Then ignition on for 30 seconds before starting. If the MAP sensor is working fine, that gives the PCM a chance to learn the altitude.

And the MEFI PCM does not have the ability (or the need) to use a MAF input signal. It's designed to run SD only. By nature of adding a MAF, you are no longer running SD.
 
#18 ·
Glad to hear you guys got it running. It's possible there could be an issue with the tune (although I doubt it), but definitely not a problem with the MEFI PCM. Since it sounds like it was fixed and you can't pinpoint how, I suspect a loose connector on a sensor (possibly the MAP).

To everyone blaming the MEFI PCM. I run a MEFI PCM, it was dyno tuned in Atlanta at 980' Altitude and it ran fine in Colorado Springs at 6,000' altitude.

THE MEFI PCM takes a barometric pressure reading upon ignition power on, before the engine is started. So the PCM knows a baseline reading. Once running, the sensor reads "Absolute Pressure" which is the difference or net between baro and vacuum in the Intake. There is also a table where fueling compensation adjustments can be made based on altitude.

My setup is not the exact one TurnKey uses, but it is the exact same PCM. Since TurnKey locks their calibration in the PCM, I can't say for sure if they use this table or not.

Since most SD tunes don't run in closed loop, there is no reason to run an O2 sensor. If the tune is done correctly, it is not needed.

Mine has the ability to run closed loop with the input of a NTK wideband O2 controller, but I don't use it.
 
#21 ·
Yea, I hear it is so bad, they have to pay somebody to run it. :flipoff2:


On a serious note, careful who you choose to take tuning advice from. If you screw up and run too rich, no biggie. It just runs like shit.

Screw up and run too lean, :nuke: .

and that's all I got to say about that!
 
#23 ·
If MJ doesn't mind me cluttering his bitterness and sarcasm with tech,

MEFI-4 Inputs
CS - Crank Sensor (a.k.a. Crank Trigger) – crank angle (i.e. where each cylinder is in its 4-stroke cycle) & RPM.
CTS – Coolant Temperature Sensor - engine temperature.
O2 - Oxygen Sensors – air/fuel ratio via exhaust O2 content.
IAT – Inlet Air Temperature Sensor – temp of air entering intake manifold (and therefore the air's density).
TPS – Throttle Position Sensor - throttle blade position (opening).
IAC – Idle Air Control Valve - the IAC supplies metered air at idle, its sensor reports the solenoid plunger position.
MAP – Manifold Air Pressure Sensor - intake manifold pressure (vacuum) and therefore engine load and altitude.
CPS – Camshaft Position Sensor - rotational position of camshaft and therefore valve/stroke timing.
KS – Knock Sensor - engine knock or ping, used to retard timing and prevent pre-ignition.

Thats for the Turn Key MEFI-4.

MEFI-4 in gerneral can also accept a fule-pressure sensor input (though it's not used by TK) which may help if you have continued problems due to altitude changes - although you shouldn't - Doc's description is bang on.

The outputs from the MEFI-4 ECM are:

MEFI-4 Outputs:
EST Signal (Electronic Spark Timing) - to fire the coils / spark plugs.

Injector Driver - to fire fuel injectors.

IAC Stepper Motor Control - Maintains perfect idle speed with the IAC stepper motor.

Fuel Pump Relay - Intelligent control of the fuel pump based on fuel pressure and engine status e.g. shut down fuel pump and therefore engine on overtemp, low oil pressure, engine overspeed, etc.

Check Engine Lamp - ECM turns on warning lamp when it detects a problem condition. It also stores a "diagnostic trouble code" or DTC which can be read by a scanner.

Tachometer Signal - to drive the tachometer.


My TK LS2 also uses two fromt (narrow band) O2 sensors.

The Turn Key LS2 with MEFI-4 goes into closed-loop feeback mode when the engine reaches approximatly 122°F
 
#26 ·
I'm not knockin the OEM PCM at all and HP Tuners is a great product.

Really there are advantages and disadvantages to each combination. Everyone should run what they are most comfortable with.

The age old debate of MAF/closed loop vs. speed density rages on. Speed density is not for everyone and every situation. Some hardcore drag racers and road racers swear by it, some like the constant adjustment to a/f ratio that a MAF based system with O2s gives you.

The only real point I want to make is that a MEFI system and SD tune can run fine at different altitudes and mine is an example of that.

The more I've thought about it, the more I think the problem they had was likely MAP sensor related since MAP is the primary feedback to the PCM of engine load in an SD tune. Either didn't get time to adjust to new baseline altitude (as I mentioned as a possibility above), or bad/intermittent connection from the plug, or possiblt a bad MAP sensor giving intermittant and/or inconsistent readings.

anyway, does anybody have any results from today yet?
 
#27 ·
I agree totally. Having tried the SD route myself I just didn't like it. Maybe I didn't spend enough time smoothing it out but personally I prefer running the MAF. I don't think there's any wright or wrong answer as far as SD or MAF, both will work and just comes down to what you like and what fits your setup best. I'll bet your right on the MAP, either bad connection or it didn't have time to adjust first time out the trailer.
 
#29 · (Edited)
The OEM PCM has speed density in it already. A good reason to tune for it and then primarily run a MAF. Redundancy. The advantage to running speed density is about a 10 hp+ increase on a stock engine and less sensors to fail, but does require proper in depth tuning.

As for speed density in an OEM pcm, it is in there.
Why?
It is in place in case of a MAF failure. When the MAF hits a certain frequency or not ( I did see it in my LS1 edit programming) it sets and runs off the speed density cell in the pcm.

I have multiple MAF flash programs that I run for my Corvette. An E-85, wet Nitrous, and the evil, yearly emissions test. :shaking: All programs tuned on a dyno.
 
#31 ·
Thanks for the tech guys. It was a real pain. You can not move race vehicles at CHCA races so we were unable to test. There is also a curfew for noise. We got lucky and got a pass to slowly run down the road as darkness fell. It seemed to be running right and we were out of time and light. As it turns out on race day, there was zero bottom end but good high end. Bill raced it but left something on the table as it was not running 100%. He missed qualifying for KOH by 3 seconds in 5.5 miles.

We still don't have the solution but will look through the info. I have always respected Turn Key stuff but am a little puzzled by the lack of sensors on this system. I don't think that was what was hampering us though. I think I will stick with Ford:smokin:
 
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