Ed Maher

OK, the title is a little misleading. I don't mean why bother, i mean why relocate a sensor when bypassing through an appropriate resistor is infinitely cheaper and equally (if not more) effective.
What i've done is use a double throw switch. One side of it leaves the stock sensor connected, allowing EGR and cruising efficency. On the other side i'm bypassing through 19.7k of resistance, making my car think it's 10' in the plenum.
So far it seems to be helping a little. I believe i was getting a little knock before, but with the cold switch i haven't noticed it any more.
Of course, all this won't matter in a month when i'm burning my own chips, but for now it's a cool little band aid.
So my question to the rest of you is, why waste money on a MAT sensor to relocate when a cheap resistor will accomplish your same goal? Is it just because you're afraid of custom EFI modding and like giving TPIS your money, or am i missing some advantage to haveing a relocated MAT reading a dubious ambient temperature.
...ed

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Ed Maher - Moderator @ The Carb Board
92 Z28 Convertible - Quasar blue / Tan top
LB9 4L60 GU2 G80 - stock, soon to be sleeper

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

Grim Reaper

A 19K resistor will make the engine think it is around 10*F and make the engine run WAY TOO RICH.

From what I can see in the SD TPI hack, the ecm uses the "delta" (the difference between the incoming air and the coolant temperature) as a factor to compute the pulse width. To the ecm, the engine assumes it has been started and enrichens it.

If you need a LOT of fuel, it's one way to accomplish it. But if your engine is not starved for fuel, you'll loose power.

By any chance, do you have a scan tool? If you do, do a WOT run with the stock MAT and then do it with the resistor. You'll notice about a 20% (if not more) increase in the pulse width.

Definitely get into prom burning and forget these "cludge" tricks.

Ed Maher

Yeah, i know it's kludgy, but you should see the disarray i work with.
No, i don't have access to a scan tool (yet.) I think that's just below the burning equipment on my list of things to do. Could be ordered as soon as next week if i ever get this damn thing inspected.
Perhaps i'll get off my lazy *** and at least throw my DVM on the O2 and get a rough idea of where i'm at. I do believe i was lean to start with, i'd occasionally hear a little knock, esp. at the top of gears. I also want to get a FP guage on this thing soon to make sure my F pump is keeping up. Tricking it into running rich was a kludgy work-around to see if it was truly an immediate problem.
btw, i've also got a double throw swicth on my knock sensor. One side bypasses through 3.9k, the other side is desensitizing. Funny thing is, i haven't had any knock since i put these in. Now you're probably thinking i'm driving frankenstein's monster. I needed the KS bypass/desens cuz i kept getting a 43 while warming up, idling!! Needless to say, i think my KS is failing and sticking when cold. However as long as i keep audible knock under control i'm happy. And having a dash like a 747 is cool too.
...ed

Grim Reaper

I am finding the stock GM eprom is quite rich, and I suspect it is by design (less warranty hassles).

I hear on the "knock" (pun intended). I am finding that this is another area for improvement on the GM eprom. I am finding the stock eprom brings on the advance a bit quick, but amazinly, it maxes at 29.2*. I have slow down the rate the advance kicks in, but increased the total advance to 34*.

Even though I have DRAMATICALLY leaned my eprom, increased the maxium advance; my actual incidences of knock (all inaudible) have decreased. This has really helped my car pull on the top end. There is definitely a SOTP difference which I plan to quantify shortly after I've done some additional changes/testing.

The other thing, is that I am now able to use a lower grade of gas...and my gas mileage has increased. My total savings is around 20% (10% due to better mileage and 10% due to a lesser grade of gas). Pays for all this equipment really fast.

8Mike9

Hey Ed, I see you're in Manassas now...working at Dominion by any chance?