Ok I have just been wondering and think I came across maybe a good idea.
With a SD car and a bigger cam you run into some problems tuning unless you have enough vacuum,forcing you to run a cam with a 110 lsa or more.
And even still the vacuum at idle jumps around alot between rich and lean ,unless you have all surrounding VE with the same value
which may not yield you best drivability.
Here is my thoughts as opposed to using a map sensor which works from 0-5 volts,use the TPS which also works from 0-5 volts correct?
So therefor you VE would be RPM vs. TPS which no matter how you look at it is directly related to engine vacuum.
Now I know that you would lose the fine correction for barometric pressure and altitude,But for people especially as myself running in forced open loop, because I am giving car what it wants .not what the 02 wants.
I feel this would give you much more smooth stable running with a larger cam and would alow you to run a much larger cam with less LSA.
What do ytou guys think?

 

I believe they call that Alpha-N. Where all the fueling is done by throttle position.

My Holley Commander is capable of Alpha-N. Basically the manual says don't use it unless you have a real beast because fueling is rather course. This may not be true for all Alpha-N systems tho.

I've never used it before, so maybe someone with more experience will have more to say...

 

Yes it can be made to work. Add an offset to the TPS value so that at idle it matches the idle MAP reading. Then scale that TPS value so that it tracks the MAP as the throttle is moved.

Blend with MAP according to RPM (to decay out the TPS portion as RPM goes up) and use that instead of MAP.

RBob.

 

Thans for reply guys.
But am I correct? I mean would this make for smoother operation with a large cam?

 

Carring 4.1s is about cheating in getting this to work.

Healthy enough motor isn't going to see alot of load with the 4.1s. Comparityively speaking.

Are you trying to run closed loop?.
Generally open loop, and like you mention similiar numbers in the adjacent steps get s decent idle.

In BruceWorld, the trick is getting as much accurate infor as possible to the ecm to calculate things. With your TPS instead of MAP you can beat what the actual load is that the ecm sees vs what the actual load is. As you get into the higher gears and aero loadings, thing get worse.

Might consider different hosing to the sensor, ie longer, and softer to dampen the MAP signal generated.

 

If you are speaking of gear ration,im running 3.73's.

No I am not tyring to run closed loop,it seems my engine likes to run much leaner than what the 02 thinks is stoich. Causing my headers to glow..
Any thought on how to fix that problem?

Actually the car runs and drives well in open loop,just figured I may be on to something with the TPS .
Got to admit,it was a pretty good idea I think.

 

Yes, 373s, my fingers got ahead of me.

Your EGTs are way out of hand for the headers to glow. That typically is like at 1,800dF. You need to add fuel and/or move the timing. What for idle timing are you running?.

It's worth trying.

 

Well Timing started out at 20 then I moved it up to 28 to try and help the problem.
As far as fueling goes,I keep getting told that to rich or to little timing causes that problem from fuel burning in the header.
So I force the car in open loop ,decrease fuel by 15% up to
1300 rpm on the VE.
It seems to have helped the problem a lot, but scares me because
because the 02 reads 4 mv most of the time at idle.
My cutout just burned wires to WB so im not sure what that says.

Thanks for helping.

 

Try backing the timing back to like 20-22 and try again.
Are you running high IAC counts at idle?.

You might me in some default region, and running in an odd state.

 

Does running too rich make the headers glow? I thought it only did that when a lean condition occurs?

 

Generally rich does because you are actually burning your fuel in the header. as is the same with to little timing.
Little backward from what you would think, huh?