Max Rpm

[Fingers]

The crank shaft pos sensor can be cocked a little messing with readings big time, also. Correct?

Well,.... no. The ECM does not care. It uses the Crank Position Sensor to time the pulse, cocked or not. My Rig notes the injection event relative to the CKP signal also. So they should match up, and do for the majority of the time. Only since I have been playing in the 3000+ area has any difference between the two been big enough to stand out. If the CKP is mis-positioned, the error from the sensors alignment would always be constant. but only relative to the actual crank position.

FWIW, I have seen an engine with the CKP out as much as 6*, but most are within +/- 1* when they come from the factory. When you start swapping cranks, reluctors, front engine covers and so on, you can introduce a significant error. But on a stock engine, the factory has shimmed them fairly close.

 

[WolfLMM]

But there is a constant error? I'm about to do a motor build and want to make sure I am as "prepared" as possible.

 

[IOWA LLY]

But there is a constant error? I'm about to do a motor build and want to make sure I am as "prepared" as possible.

Use the front cover that came with the motor if possible.

 

[JoshH]

Use the front cover that came with the motor if possible.

Would it be more important to use the front cover with the block or the crank and reluctor wheel?

 

[Fingers]

Actually, the crank matched to the front cover. Provided you left the CKP alone.

Regardless, any misalignment of the CKP is easy to tune out. For instance, even if it is 5* off, you simply adjust all your timing tables 5*. Not a huge deal IMO.

Knowing which way it is off is another matter.

 

[IOWA LLY]

Actually, the crank matched to the front cover. Provided you left the CKP alone.

Regardless, any misalignment of the CKP is easy to tune out. For instance, even if it is 5* off, you simply adjust all your timing tables 5*. Not a huge deal IMO.

Knowing which way it is off is another matter.

How would you go about determining which way, and how much you are off?

 

[RENODMAX]

Why is nobody taking TCM into account for spinning big RPMs in auto trucks?

 

[Fingers]

I am well within a degree on my engine. I indexed the crank myself when I keyed it, then verified the alignment both on the stand and with the pressure monitor. The engine I took out of the truck is one that is almost 3* off. Untouched stock. I often suspected it had a loose reluctor, but never checked.

The trailing edge of the 25th tooth past the gap is TCD. You can power up the CKP sensor with 12 volts and then watch the pulses on a voltmeter as you turn the crank if you have the engine on the stand. In the truck, with ignition on, you can monitor the CKP signal, but knowing where the real TDC is, is difficult without pulling an injector.

Or, you can hook up a chamber pressure monitor.

 

[Fingers]

Why is nobody taking TCM into account for spinning big RPMs in auto trucks?

I can't think of any control function the TCM does that would be impacted by higher RPMs. That is, until you exceed the speed sensors, but their accuracy isn't critical.

 

[RENODMAX]

As in how do you get the Allison TCM to shit at 5k. I dont believe it will. I think you need a different TCM

 

[Fingers]

Why wouldn't it?

 

[Brayden]

I've manual shifted JNeals truck at 5300rpms on the street.. accidentally..

Stock valvetrain too..