Hi Folks, I have an interesting tuning issue I can't seem to figure out. I am trying to tune my car for the best possible mileage under cruise conditions. I target about 15:1 AFR. I can achieve this except under an extremely high vacuum cruise. My problem is that I cannot pull enough fuel out to get to the targeted 15:1 AFR. I have reduced my TOG and IOT as far as possible and adjusted the specific VE cells to the max of -50 but the leanest I could get is 13:05 AFR. My below VE table is temporary and was used just to test different setups. Notice my lowest kPA header value is 33 and the MAP value in the log dips to 28.2 and below.

I use a 3-Bar sensor which cannot go below 32.5. Is my issue just a limitation of the 3-Bar sensor?

if its registering 28 then the map sensor is reading it. Log your Injector pulsewith and check it against ur VE table and see if they are showing correct.

Looks like my desired PW is going well below my Minimum Injector Turn On Time of 1.3. It's actually as low as .39ms which is impossible to acheive. No wonder I was not able to take out any more fuel.

So is the answer that I cannot tune for stoich in area's where I have high vacuum but not in deceleration?

Are you running sequential? Can you run a smaller injector? If you are not running sequential switching to it would effectively double your pulsewidths allowing you more leeway in those areas while not taking anything away in the top end. Other than that either a smaller injector if capable or staged injection would be your only option.

Blaine

I'm running a wasted spark config for now. I have plans to switch to sequential but haven't gotten around to building the cam sensor. Thanks for the response.

Looks like everybody else beat me to it...
You did see the cam trigger setup that I made from an old distributor, right?

I did. I was just hoping I didn't have to go to sequential to tune this part of my VE. Sheesh.. BIG injectors will be an even bigger pain.. : )