MILD THUNDER

iTrader: (3)

They way I see it, whatever the engine, whatever the combination, its all about preventing failure. If an engine can run at 12:1 and not fail, then thats good. If another engine needs 10.5:1 to not fail, then thats good as well.

My goal is not to speculate on GM on what they did wrong, nor mercury racing, or what they did right. I aim my posts at the average do it yourselfer, like myself. For the guy building a home built supercharged marine engine. Some of these topics, can be beneficial to them. While the 1075 lives at the air fuel ratio it does, it is certainly not the target for the guy running a 177 blower on a 502 with a carb and no knock protection, no intercooler, poor fuel distribution, etc. Many guys over the years have burnt pistons, valves etc, due to lean conditions before widebands were available. They thought the plugs looked fine, so it had to be something else causing it. Next thing they are running 28* timing, to keep it together, which really was a band aid to the tune.

mike tkach

iTrader: (3)

one thing that has not been mentioned yet is the heat soaking of the innercooler and the combustion chaimber. in a v btm boat with throttles at wot for longer runs.an engine may be fine at 3 minutes of wot but what about 10 or 15 minutes?

Keith Atlanta

So if they are running so rich how the heck do they get a claimed 29MPG highway?

phughes69

because the highway EPA cycles include a lot of light throttle cruise speeds

SB

iTrader: (1)

Crusie is not 50-60% throttle with very heavy load, like a lot of boats are.

I'll take a stab at it, but it probably only takes 35-45hp for a Vette to cruise at 65mph. So,,,,very light throttle, very high vacuum, very little oxygen/fuel in that combustion chamber....ie:very low cylinder pressure.

mike tkach

iTrader: (3)

we are talking about wot a/f ratio.

Keith Atlanta

Right, but early on he said starting at 4000 RPM the AFR was 10.7. Does it drop to an AFR of 13 at cruise speed if it isnt under stress?

airjunky

iTrader: (2)

If its in closed loop at 11 to 1 i may have to see what they are using for primary o2s on those

mike tkach

iTrader: (3)

i,m pretty sure those ratio,s are at wot,yes if you are crusing at 4000 rpm and not at wot i think the a/f ratio will go much leaner.

BUP

iTrader: (9)

I would wonder what the AFR's are for the Vette to pass emissions for CA & Carb testing. There is no way being street legal in CA running in the 10's AFR.