High speed cruising A/F ratio's...

[Travis Moore]

Did ALOT of high speed cruising this weekend, 110 indicated for many miles at a time. AF ratio was in the 14.5 range, which is perfect for a turbo car under vaccum, but on the sled i am running about half to 5/8 throttle and right around 7psi of boost to maintain 110(was more concerned about keeping it on the trail then staring at gauges). Normally i would be very concerned with a 14.5 a/f ratio for a extended period under boost, but i ran about 40-50 miles of trails this weekend and checked the compression, and it was still perfect. If it was going to hurt the motor, it would of this weekend! This is at 11.5 boost, strait AVGAS, and a Bender stage 2 kit with 600 PITOT(in the charge tube) jet. Just wondering what you guys think..

 

[Ted Jannetty]

You must have gotten great fuel economy at that speed.

14.5 at 1/2 throttle is fine, you were crusing, so there is not much load on engine, as long as it goes progessively richer as you increase throttle your good.

Even though your gauge is reading 7 1/2 lbs boost in the manifold your still controlling volume in to the cylinder with the throttle blades.

YOUR GOOD.

 

[Travis Moore]

The fuel milage was indeed great. The first day out, i burned about 7 gallons of fuel for about 90 miles of high speed(100+) cruising.

 

[Skydog]

(((Even though your gauge is reading 7 1/2 lbs boost in the manifold your still controlling volume in to the cylinder with the throttle blades)))

AHH yes never thought of that! Thank you

 

[ken_climb]

speed.

14.5 at 1/2 throttle is fine, you were crusing, so there is not much load on engine, as long as it goes progessively richer as you increase throttle your good.


YOUR GOOD.

I don't get this a/f stuff!???? your saying 14.5 is safe at 1/2 throttle but not at wide open?? I seen on another thread where you said 12.5 is as lean as you would go but why does my manuel for my new wideband say that 14.7 is optimal fuel ratio for a gasoline engine??????.CONFUSED!!

 

[ptt]

Ken I can't speak for Ted.
How I see this is:
Wide open= 12.4-12.6 (through out the run)
Mid- cruising (trail) 13.5-14.5 (your not on the hammer)
From a dead pull right up to top speed: 12.4-12.6 is what I look for.

14.7 is the standard used though out the auto industry.
We are not in the auto industry, we are in the HORSEPOWER INDUSTRY!
GO HAMMER THEM KEN!

 

[ptt]

Ken what A/F did you buy?

 

[Skydog]

Ted you think there is much HP for 11.2 to 12.0?
What have you seen on blown cars? A buddy has a in house dyno and he says only a few more hp.
My sled does not feel any faster at 12.0 vs 11.0

Skydog

 

[4strokes are better than2]

my manual says 11-12 at wot for turbo or sc applications 13-14 idle

 

[Ted Jannetty]

speed.

14.5 at 1/2 throttle is fine, you were crusing, so there is not much load on engine, as long as it goes progessively richer as you increase throttle your good.


YOUR GOOD.

I don't get this a/f stuff!???? your saying 14.5 is safe at 1/2 throttle but not at wide open?? I seen on another thread where you said 12.5 is as lean as you would go but why does my manuel for my new wideband say that 14.7 is optimal fuel ratio for a gasoline engine??????.CONFUSED!!

I also wrote A/F in relation to throttle or what I call Load if you go back and re read my post on tuning with boost.

Idle and light throttle can be 14.5, and as load or throttle increases the A/F should taper down to 12.0 at WOT.

To clarify this is under acceleration.

Now when you get up to speed and cruise your load on the engine is reduced so you can run much leaner A/F like 14.5 at cruise.

IN fact the best fuel economy occurs at about 15.5 A/F, which is fine at light loads.

As much as this is not the automotive industry, it is still a 4 stroke engine and the requirements are the same.

 

[Ted Jannetty]

Ted you think there is much HP for 11.2 to 12.0?
What have you seen on blown cars? A buddy has a in house dyno and he says only a few more hp.
My sled does not feel any faster at 12.0 vs 11.0

Skydog

Yes I do, it is not a lot but you can be too rich which causes other problems, Plug fouling, ring wash, oil dilution, accelerated wear, carbon build up that can lead to detonation.

11.8 to 12.0 is your target at WOT full load.

 

[ken_climb]

Thanks..its slowly starting to sink in! i baught the innovative stand alone wideband with digital gauge.

 

[Skydog]

Thank you again TED!