mixture adjustment via head temp resistance Options

[ape914]

Just wondering if anyone has made up some data points on how a change of resistance in the head temp circuit effects the mixture?

I know of some one long ago that had installed an additional head temp resistor in line. They wired a variable resistor (potentiometer) all the way up to the dash so they could add enrichment on the fly. They had no airfuel meter so it was all seat of the pants.

I am considering that a a possible fine tunning method on a D-jet 914. With an aftermarket cam, big bore pistons and non-stock compression ratio, I think there might be some room to add enrichment across the range.

what I am thinking is to add an airfuel ratio meter, or go by head or exhaust temp as a guide, and adjust the mixture via this method and watch the gauges to try to find an optimal setting.

Has anyone already tried this?

How does head temp reistance effect the mixture? is it uniform across the rpm and load range? or does it only effect certain running conditions?

Just begining the thought process on this, and dont want to re-invent the wheel if it has already been tried.

By running a parallel reisistance, one could also lean out the mixture.


I know some folks will tune the Pressure sensor (MPS) to change mixture, but I am thinking this is one more tunning tool maybe,and with a variable resistor wired to the dash, it can be changed on the fly, unlike MPS adjustments.

[brant]

my understanding (but go read all of the brad anderson stuff)

the CHT is designed to only enrich while the motor is cold for the first 10 or so minutes...

yes you can "trick" it into thinking the motor is always cold so that it effectively "always" has the "choke" turned on....

its probably across the board
but its a gross enrichment and not really good for the fine tuning of an engine management

You'd be much better off tuning the MPS and doing things the right way
the MPS adjustment allows you to tune multiple settings... ie: you can tune WOT with the MPS and also tune partial load (2 settings, unlike a megasquirt with 2 million settings)

the other part of your problem is the cam
the Djet system operates on vacuum
a big cam has high overlap
during the overlap periods there is a pulsation feeding back into the plenum
it screws up your vacuum signal

you really need to use a mild cam with DJet
the raby djet cam is supposed to be the best beyond all others.