Just trying to start shit

I know what I run/think

Do you?

I need more info. Is this question for a naturaly aspirated engine with typical atmospheric preasure? Gna he, gna ha, gna hr.

Sure... sounds good...aircooled of course

Anything from 13.7-18.0 on my street NA motors. Usually 11.5-18.0 on street turbo motors.

Wow! mine never varies that much...unless you're counting decelleration. Then I can see 99:1

We're talking aircooled right? That's a tad lean in my book.

I run really lean at part throttle and cruise. Say 50mph at 2500rpm in fourth I will read 15.7-17.0 depending on Throttle position and engine load.

Sorry not air cooled, but I would run it that lean if it was aircooled.

I'm going to dinner, I'll splain more later.

I never measured an aircooled engine in real time.

Why not run the engine as lean as you van get it under cruising and light load situations, You will never hurt the engine. I usually set all fuel below 600mbar very lean. I also tend to run a lot of timing down low as well. Helps light off lean mixtures.

Some interesting reading here some dismiss these as not applicable to automotive engines, however the laws of thermodynamics dont care whether the engine is a type 4 or a lycoming, or a 911

another interesting article

nuther


We run our turbo engines at around 12:1 making power, and lean them out at part throttle. And the ratio we end up with that makes the most power looks remarkably like the pratt&whitney and lycoming graphs

I run the "whatever makes my car not backfire or carbs pop" a/f mixture.

I still haven't found it either.

that would be a lean mixture

Are you saying lean as in that would be too lean?

I think he's saying that when you hear popping and backfiring on overrun, your car is running lean. That's what I've always been told.
Samson

13.7 at part throttle and 12.5 at WOT running Djet. If it varies off that much it runs like shit.

I have to side with Tim and Geoff and disagree with Brett. Although running lean on a watercooled works fine and many new cars do run lean for emissions and mileage, it can spell death to an aircooled.

I run in the low 12's at WOT and the low 13's at part throttle. This doesn't mean I haven't tried a leaner mix because I have. As I have approached 14:1 I see the
head temps go up 50 degrees to about 350 and the oil temps by almost the same.
I tried 15:1 for about 10 seconds and very quickly stopped that, as I like my seats where they are.
Between WOT and part throttle I rarely see more than a one point difference with my SDS PEFI system.

I have also played a lot with my timing, I always end up back at 28 degrees of total advance. Although I have found that by retarding my timing (I have programable ignition) back to 24 degrees after 4800rpm gave me some extra power with no ill effects.
More advance again made my temps go up.

Tim the aircraft engines don't suprize me...the T1, T4 and 911 engines are basiclly based on aircraft designs.

Running between 12.5:1 and 13.5:1 gives me head temps of 300F and oil temps around 180 and I'm quite happy with that. BTW this was constant on a long 10 hour (stopping for lunch, etc,) cruise, at speeds of 80 to 90mph. Shorter trips gave the same result.

This is with a VDO head and oil temp gauges and a WMS wide band meter.

It will be interesting to see how a nickies engine changes my results.

Is that poping noise like when one revs the engine up and down shifts a little early and you hear that poping like its coming out the exhaust? I had a Chevette which did that alot although it had a head gasket leak.


VVVVRRRooommm pop pop pop.

Its BRETT, how hard is that to get right when it is written above.

There is no need to waste fule like that. Take the engine and warm it up and go out on the highway. With an EGT sensor check your EGTs at you fuel air ratio of 13:1. Then drop the ratio to 16:1 and bump the timing up maybe 5 degrees. Watch your EGTs drop. Retarded timing creates heat in the exhaust. I run up to 47degrees of total timing at crusing speeds below 600mbar. I am also running around 230psi on a compression gauge on this motor. You can't raise EGTs by leaning an engine out. If there is not enough fuel to burn then you can't have a hotter flame. (this only applies to a NA motor)

I have run as much as 50 degrees of total timing on some engines at light throttle. You have to tune timing on a dyno by watching your torque curve.

Oil temps must get to a minimum of 212 degrees otherwise you will wear an engine out faster. One of the problems with T4s is poor head design and low compression ratios. The lower the compression ratio the more unburned fuel you can have in the exhaust system. More compression usually lowers EGTs, all things being equal.

The problem with carbs is ignition control. You can't lean a carbed engine out and get the right amount of timing in the light throttle range. That is one reason why carbed engines have to run a little richer at part throttle.

14:1 or so cruising make 26 29 MPG heads 300 oil 180 195
12.5:1 WOT and I don't care about MPG Head 345 oil well depnds on how long I hold it. Last week at the track the oil stopped climbing around 250 260

Ditto...

13.8 to 14.5...325 on head temp...oil will climb to around 250..

2.7 l. nickies...

Herb can get away with it because off the nickies. I'll know this first hand in about 3 weeks.



Sorry I ment Brett

Let me know when you try this on a aircooled...Watercooled engines are not comparable in tuning to aircooleds.

Do it, dyno it and post it! On an aircooled...Oh and then put a couple of 1000 miles on it. Other than that talk is cheap, and without proof it's just bad advice.

Waiting...

Find me an aircooled dinosaur to play with again and I will let you know the results. The rest of the world uses water because it is better in all aspects.

I really have no desire to go backwards.

I am running 9 to 1 compression and oil temps are in the 190-210 range. above 14 to 1 and it really does run like shit, without much power. I am using 28 degrees of advance and a LM-1 meter.

I love threads like this..

We map our EFI systems to make power under load ( go figure )

Much of the part throttle/ low load maps are lean..

The "lean will kill aircooled quick" line is a myth. Note that the Pratt & Whitney graphs alluded to earlier are for air-cooled flat-four pushrod engines. The highest CHT is just rich of 14.7:1. On either side of that, CHT falls, and it falls faster on the lean side.

Whether an engine will run well lean is primarily a matter of combustion chamber design, not air v. water cooled. Honda designed and built a motorcycle engine some time ago to run super lean, and it was air-cooled.

If you define "lean" as "leaner than max power", then this statement is true. If you mean "leaner than stoichoimetric", then it's false.

on my 1st Megasquirt install on my 1.8 I drove around for about a week with it at 17:1

I didn't have an O2 sensor/reader at the time, I knew it was down on power and pinged under load.....

put it on a dyno to get the air/fuel numbers and to tune it...went from a mighty 40hp to 80hp with a few clicks of the keyboard

too hot ...

I agree...do you guys find your power crisp at the start of the run and a bit down on power by the end? That's heat-soak.

Both Joe and Herb I'd try going down one point on the A/F ( in joe's case one size bigger main jet) and see what happens to your oil and head temps.

Yea 1 size bigger main jet... That'll slow it down for sure. Actually went one size bigger on the air jet and made more power. Temps were still good.
Ya'll got to remember 250 on the oil was after all freaking day running on the track. car never sat for more than 20 minutes most of the time it was like 5 or 10 minutes before my codriver took off for more hot laps.
We are talking WOT for 90% of the course. Not your average DE. rather open lapping day as many as you can fit in. Burned 3/4 tank of gas and took new Hoosiers to 1/32" left. and we all know what I did to the brakes.