Setting TR Fuel Mixture

A few pics from today setting the idle Fuel Mixture on an 88 TR.

It's also advisable/neccesary to use 2 Manifold Vacum Gauges T'ed in...and the air set the same side to side. For some reason the pics of the gauges failed to come out properly..I'll update tommorow.

Regards, JRV

JRV: Interesting thread!

Are you adjusting the vacuum first, then doing the CO reading? If so, do you find that you have to re-adjust the vacuum?........and vica versa?

I notice that you are using the exhaust gas taps, to check the CO........I recall there are 2 on each side, each serving 3 cylinders. When I pulled the engine, several of my taps where either broken, or cracked, at the pre-cat, where they insert into. By the readings, yours where obviously intact. Are you testing BOTH ports on each side?

It appears that the car has a standard exhaust. I assume that you used the ports (as opposed to the rear muffler tips), because of mixing, in the exhaust, of the gases........hence, not accurate readings. If one had a Tubi, then one could test from the rear muffler tips.......right?

This is very interesting. I assume other Ferrari Kjet settings are similar. Wonder if anyone has a chart correlating CO to A/F ratios? That would be a handy little chart to have. On V-8s I have watched in amazement as Kjet will keep AF flat line right at 14.2 from 3K - 7.7K

It would also be interesting to see the correlation between A/F, CO, and duty cycle.

>>be interesting to see the correlation between A/F, CO, and duty cycle.<<

The Bosch FI Manuels state that duty cycle will be 50% when the mixture is stoiometric (14-1).

Hi JRV,

How much adjustment is required (i.e. 1/4 turn, etc.) to the mixture screw in a case like this?

Carl

Hi Carl,

actually very little turning of the screw is required..I don't remember making a mental note but likely in the 1/2 - 3/4 range would take it from 3% to 1%...

Basically one just turns the screw some amount ...1/2 turn say...then plug the hole and wait for everything to settlr in..and observe the gas readings...blip the throttle and observe...it probably takes 3-5 minutes of observation to be sure the numbers stabilize and continue to hold within a narrow range.

How is your setting &amp; testing coming along?

Regards, JRV