pmr's make a mess

[CSIPSD]

You are correct the PCM relies on the CPS to tell it where the crank is - so if you dial in the timing tables with the Black CPS then dial in the timing tables with a Blue CPS - your tables for the blue CPS with just be +4 degrees of timing using your made up numbers for this argument - the actual injection event taking place in the engine should be identical if the timing was truly dialed in in both instances.

FWIW - I didn't think you were being a smart ass - but I don't care if the CPS is magenta - if the timing table is dialed in via live tuning with that color and its maintained that way it doesn't matter.

How do you know what the acual timing is? Without a scope or something like that?

 

[Hotrodtractor]

How do you know what the acual timing is? Without a scope or something like that?

How do you know what the actual timing is after a live tuning session?

FWIW - a scope using just the CPS signal and the injector signal will not give you "actual" timing - but it can get you in the ballpark. The signal output of a CPS signals the computer that the engine is say at Top Dead Center (TDC) - we know that that signal location relative to the actual TDC is different between the black and the blue CPS - the blue CPS retards the signal going to the PCM relative to the black CPS. Agreed so far?

To have your truck "live-tuned" is going to dial the truck in spot on right? So we go out and we do this with a black CPS and the world is grand. Agreed?

Now we toss in the blue CPS - and the timing has been retarded because of it correct?

Now we live tune the truck with the blue CPS to get the truck dialed right in spot on again. To get the truck dialed right i spot on you need to have the combustion events occur at the same time as you did with the black CPS - so this new tune just has to add timing to compensate for the retarded signal.

If we scope the truck with the blue CPS you will see more timing on the scope - but that doesn't mean that you actually have more timing in the motor. The only way to truly know the timing of what is going on in the combustion chamber is to KNOW where the actual events are occurring in the combustion chamber.

 

[TrailerHauler]

Good info, in short the way i'm understanding that is, it doesn't matter which cps your getting a signal from when your dialing in the combustion event with live tuning. And the only difference when live tuning with with a different cps is your baseline, or starting point from which you'll alter the timing to dial in the engine.

 

[Chvyrkr]

Joe, doesn't her 38r and your old setup on the truck have 1.15 exhaust housings?

If so, then that helps explain they those 2 setups have withstood. (tuning aside).

I personally wouldn't run a 38r with the wg 1.0 housing because of the retarded amount of backpressure. 1.15, maybe.

My PMR engine ran a 1.0 for close to 30k, no issues there.

Now that's interesting on several levels. For some reason I've always thought it advanced the timing. Quit using it in fact. Still have a brand new one in the box somewhere. I'm curious to find out more details on what it actually does.

I was always under the impression that nobody really knew exactly what the blue CPS did, advance, retard, etc.

How do you know what the actual timing is after a live tuning session?

FWIW - a scope using just the CPS signal and the injector signal will not give you "actual" timing - but it can get you in the ballpark. The signal output of a CPS signals the computer that the engine is say at Top Dead Center (TDC) - we know that that signal location relative to the actual TDC is different between the black and the blue CPS - the blue CPS retards the signal going to the PCM relative to the black CPS. Agreed so far?

To have your truck "live-tuned" is going to dial the truck in spot on right? So we go out and we do this with a black CPS and the world is grand. Agreed?

Now we toss in the blue CPS - and the timing has been retarded because of it correct?

Now we live tune the truck with the blue CPS to get the truck dialed right in spot on again. To get the truck dialed right i spot on you need to have the combustion events occur at the same time as you did with the black CPS - so this new tune just has to add timing to compensate for the retarded signal.

If we scope the truck with the blue CPS you will see more timing on the scope - but that doesn't mean that you actually have more timing in the motor. The only way to truly know the timing of what is going on in the combustion chamber is to KNOW where the actual events are occurring in the combustion chamber.

To further clarify, when we tuned my 02 at Beans it got strapped to a dyno. Jonathan added a degree or so at a time until power leveled off, and pulled the timing back to peak power. He asked me if I wanted it backed off any further, but since the approx timing value was only 1 or 2 degree's past stock, I opted to leave it.

Now, if I swapped CPS's, and thought my timing was off, I could take the truck back down, and readdress the timing curve.

And the effective timing, when tuned that way, would be the same after both the first and second events. Goes bang at the same time.

 

[Big Bore]

In any event, since most tuning is based off the stock CPS, it seems counter productive to pay more for the blue one and confuse the issue by taking the baseline for timing in some unknown direction, either advanced or retarded.

 

[Chvyrkr]

Agreed.

 

[Dieselfever]

My thinking my be all wrong but if you have a scope on a truck watching the CPS and injector to see what timing is electronically then The timing should be the same for both Sensors electronically (in the same program). It's the sensor actually looking at the wheel is where the change in timing comes.

So then you scope the CPS signal and get a cylinder pressure transducer in there now, keep the same program switch from one cam sensor to the other and the timing change will be apparent then but the cam signal and electrical timing still jive together with both.

Same principle as how a 10k mod works, No?


-Michael