Hank Cohn

I have seen several dyno sheets in the past, but am unable to find any of them using the search function. I am trying to find out what is a normal air fuel ratio for a normally aspirated Varioram 993. My car is under 14.0 to 1 until 5500 rpm where it goes to 14.2 to 1. Is this similar to your results?

Thanks in advance,

Hank

Don Magee

First the disclaimer--I am no expert on this. But, that sounds too lean at high RPMs. On my car, it was around 12.7 to 1 at high RPM. I was told mineAround 14.7 to 1 at idle is about right, but for max power and cooler engine temps it should be around 12.5 or 13 to 1 at high RPMs. Steve W, of course, is the man on this topic, as well as many others.

Steve Weiner-Rennsport Systems

Hi Hank:

Lots of variables here and throttle position is the biggie when talking about A/F ratios.

Depending on load, it will vary from 16:1 to 13.5:1 in stock chips.

I like to see 13.2:1 at full load, WOT.

Don Magee

Steve, thanks for the assist.

Hank Cohn

Don and Steve:

Thanks for the help. I actually found several of the posted dyno sheets by searching for "dyno results."

You guys are right, of course, about making safe maximum power around 13.2. I was just curious what the air/fuel ratio graph of a stock engine with a stock chip looked like.

Steve, as you are aware, I am still fighting my over-lean problem. I think we are close to a solution. I'll keep you posted.

Hank

George A

Hank,

I've got some Dynojet files of my car if you want them. Email me and I'll send them to you. You can use the Dynojet RunViewer to look at what ever you want.

George

Hank Cohn

George:

Thank you. I may take you up on that later today. My car is at the dyno now and I should have all the information about my car for comparison later this afternoon.

Thanks again,

Hank

George A

No problem. I've got several dyno runs, mine ('96 993 varioram), a '99 996, an early 80's 911 with an Euro engine, and too many BMW runs to mention.

George

Chris W. - '96 Targa

FYI, I believe 14.7:1 is the ideal stoichiometric Air/Fuel ratio for gasoline combustion. Usually a bit richer (numerically lower first number) to get optimal power, at the [slight] expense in economy.



-Chris

Hank Cohn

George:

Thanks again for your kind offer. My problem is solved. It turned out to be an injector issue. Now, A/F ratio is much more normal as are the HP and Torque curves.

Thanks again,

Hank

Steve Weiner-Rennsport Systems

Hank:

Good to hear that you found the problem and fixed it. How many miles were on those injectors?

FlyYellow

Hank, please tell us more about the problem you had, the symptoms and how you diagnosed it....

cheers,
boris