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Trying to get this thing tuned now. Advice please.
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Author:  Sam Powell [ Sun Jul 30, 2006 7:23 pm ]
Post subject:  Trying to get this thing tuned now. Advice please.
I have two immediate problems: The computer timing is about 30 degrees slower than the actual timing. You are supposed to lock out the timing map with a timing figure of your choice, and then time the distributor so that the timing mark comes up to agree with the locked in figure. When I set the computer to 0 degrees, and retard the timing as far as possible with this damned slotted timing adjustment, it still reads about 30 degrees advanced. I have to play with things until I can get the timing at 0 when the computer says it should be zero. They say to start out with the timing set at about 30 degrees advanced, and this then in fact works out about right with the computer. Somehow zero then becomes zero. It would be so much easier with the clamp type hold down.
The other issue is the TPS. When the throttle is closed, it reads 4.1 volts, and when it is WOT it reads .57 volts. This must be wrong. Accel uses the standard GM TPS. Does it not go up in value as the throttle is opened. You Mega Squirt guys out there, can you tell me which wires I need to reverse to get this thing reading correctly? I guess I could figure it out, but it is much more fun to bug you. Thanks.
Sam
Author:  sandy in BC [ Sun Jul 30, 2006 8:33 pm ]
Post subject: 
TPS :You should be .2 volts to 1 volt at closed throttle and 4 to 5 volts at WOT.

I suspect something dyslexic has happen to your TPS wiring

Grey wire is reference(should be 5 v , blue is signal (.o2 to 5v) and black is ground.

(note: this is GM info,,,,,no MS)
Author:  Pierre [ Sun Jul 30, 2006 9:26 pm ]
Post subject: 
Sam, reverse the +5v and ground at the sensor. The third wire is in the right spot if it varies in any direction.

Are you running the MS now or accel? If its the accel it may expect this "reverse" tps behavior. Check throttle % variable to make sure not just tps voltage.

You may be off a tooth or two on the distributor. Megasquirt has a single variable you can set that arbitrarily offsets the entire map to make up for a misadjusted distributor or pickup iirc.
Author:  Sam Powell [ Mon Jul 31, 2006 5:03 am ]
Post subject: 
Thanks Pierre, and Sandy. You can offset the signal by a factor they call "crank offset degrees" in the calibration screen, but the manual does not explain how this affects timing. In other words if I put 20 degrees in, does this advance the actual timing or retard it. I know I cn try it, and see, but my laptop battery expired, and so did I, so I went to bed. As for the TPS, the manual does not state, once again, which way the voltage should vary,they just give the range of the variance. I suspect that it expects exactly what the MS expects, which is what GM intended, since the accel is intended to swap into GM vehicles with no modifications. All the sensors are GM. I have to work this morning, so will think about it, and have a note into Rance about the TPS and the timing issue. I'll see what he says. Thanks again. I wil print out this page and stick it in my binder as a reference on the TPS wiring. It is stuff like this that Accel's manual needs.
Sam
PS, anyone familiar with the movie Office Space should get a smile out of the TPS thing. It was TPS reports that the goofy boss was always asking about. :)
Author:  LUCKY13 [ Mon Jul 31, 2006 11:58 am ]
Post subject: 
The voltage should go from low to high as you move the throttle, the statment obove about reversing the wires should cure this.

The crank offset should get you strighten out on the timing problem. If I understand right that is what it is for, to get the ECM & your dist on the same page so to speak. Just like when the guys with crank triggers have to set the degree to match what there crank trigger is at when the engine is at TDC.

Hope this helps.
Author:  Pierre [ Mon Jul 31, 2006 4:03 pm ]
Post subject: 
Sam check out the megamanual at http://www.megamanual.com/v22manual/mtabcon.htm it has all the bits about tps etc in the inital assembly/testing section.

For the timing issue - I say zero out the timing map and play with the distributor until its close to 0, then use the offset in the program to finetune.
Author:  GunPilot [ Thu Aug 03, 2006 10:47 am ]
Post subject: 
Quote:
PS, anyone familiar with the movie Office Space should get a smile out of the TPS thing. It was TPS reports that the goofy boss was always asking about. :)
Did you get the memo?
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