Racing Fuel Systems

Anyone tune around stoich....with petrol, ethanol, or methanol?

If you mean full-power mixture, no... I keep my (WOT) AFR around 12.5, maybe 13 at leanest.
Now for cruise, 15:1 works fine and I could probably go even leaner

...

FA car. no electronics. so i run a go pro on the gauges.

this at the stripe. fastest pass of the season. not sure exactly where i was on this side of the flame, as this gauge only reads to lambda of 1.22. #1 egt did not even crack 1200*

When we are tuning stuff on the dyno I don’t tune around the AFR. I watch AFR but also watch egt’s and plugs and find best power. From there the afr is just a number to me as we are looking for best power.

I have tested the same engine but with two different intakes. One had really good wet flow characteristics and the other was poor. The each made peak power with a full point difference of AFR from the other. This was with the same carb as well.

Paul

Was the peak power the same hp for both intakes?

It would have been interesting to see the AFR for individual cylinders. Sounds like good wet flow is important

Nowhere near. One was a single plane and the other a dual. It was on a 500” BBC. The airspeed was very high for the dual plane so I suspect the fuel was having a hard time making the turns. I was shocked how much more jet it wanted.

Paul

Question: if you have to jet it richer, where does the extra fuel (while making less hp) go? Eventually unburnt in the exhaust?

Excellent question! Fuel drops out of suspension onto to manifold/port walls due to lower air speed?

Darrin Morgan has a few YouTube videos where he talks in depth about de-atomization in the intake tract. So much is counter intuitive as what shapes look and may well flow the best tend to be conducive to fuel sticking to walls, floors and roofs.