Annular boosters on a Tunnel Ram

[TT5.9mag]

I think @Rat Bastid has his dyno up and running. Maybe we could convince him to do some MAB testing on the next engine he loads up.

 

[MomsDuster]

What would one consider to be a safe AFR limit under light acceleration say from a dead stop to 40 mph.

 

[TT5.9mag]

What would one consider to be a safe AFR limit under light acceleration say from a dead stop to 40 mph.

Has a lot to do with the combination. If you’re on the edge of detonation a little richer can help but it should start out fairly close to stoichiometric at idle and get gradually leaner under “light” acceleration. So 14.3-14.8 idle, 14.5-15.0 light accel, and go pretty rich as load and rpm increase. 12.6-13.2 or so at wot full load.

 

[Mattax]

What would one consider to be a safe AFR limit under light acceleration say from a dead stop to 40 mph.

With something hot rodded or even old school factory performance cam etc, the AFR load illustration from Larew provides a pretty good idea. I've reposted it here (FABO) but you can
also look at some of the other graphics Tuner posted (one is from Chrysler) here.

racingfuelsystems-Desired Carburetor AFR Characteristics At Different % Load

The clue here is rich idle, lean cruise, leaner (leanest, actually) part-throttle acceleration and rich WOT. The leanest is at mid-load, half-thrott

www.tapatalk.com

 

[Mattax]

Has a lot to do with the combination. If you’re on the edge of detonation a little richer can help but it should start out fairly close to stoichiometric at idle and get gradually leaner under “light” acceleration. So 14.3-14.8 idle, 14.5-15.0 light accel, and go pretty rich as load and rpm increase. 12.6-13.2 or so at wot full load.

I'd say a lot of these cars will not tolerate such lean mixes under part throttle due to cam and fuel distribution.

Also non-emissions idles will be in the 13s.

With hotted up engines, the cam overlap, high idle rpms, etc hard to say what a WBO2 will readout. Seen it jump a half an AFR between in gear and out of gear, and so forth.

That's why more than once I've posted that tune for the goal, and most of those don't need a WBO2.
One thing logged WBO2 is really nice for is seeing if the AFR is stable or drifts at the top end.

 

[TT5.9mag]

I guess I should have clarified and started that post with, “in a perfect world…….” But @Mattax is correct, intake manifold design and cam timing events will make a huge difference in what the engine will tolerate

 

[Mattax]

I guess I should have clarified and started that post with, “in a perfect world…….” But @Mattax is correct, intake manifold design and cam timing events will make a huge difference in what the engine will tolerate

Well it was an open question so you gave the answer from what you are most familiar with, which I think is a little broader and more modern.

 

[Mattax]

As delivered, this Holley 650 vac secondary kept the AFR pretty flat at the top end.
But notice that reducing the jets enough the MABs are just at the point of needing to be reduced a little to match.

Here's how much was gained by changing jets.
70,74 to 66, 72
View attachment 1715473374

This was done on a dyno which of course cost money.
But one advantage over buying a WBO2 logger is easier learning curve and installation.

 

[Mattax]

This is not a stellar example, but provides an idea.
approx 230 @ 50 cam in a 340 with around 9:1

The black line marks when the car is neither accelerating nor decelerating.
Above that are the AFRs with very light acceleration, less than .03 G

Below is the matching aceleration in G's.

 

[Mattax]

Same engine, a couple logs showing slowly increasing rpm with small throttle opening.

Here's a situation where showing TPS would have been nice.