Safe air/fuel ratio at WOT on the dyno?

[Turbo6TA]

I am going to the dyno this weekend ...

Just wondering what air/fuel ratio is pretty much safe when running the stock timing, 16 psi boost and pump gas and pretty much a stock motor.

I have tuned with about 790 mv on the O2 sensor, but I think a fuel/air ratio measured on the dyno would be a much better tune.

Is 12.0 to 1 a little too rich at the top of the gear with full boost?

What do most of you tune for while using Premium pump gas on the street (with NO water or alky injection)?

Thanks for an input

Ron,

 

[Louie L.]

In my experience you dont want anything lower than 11.8-11.5.
The trade off in power If any is not worth the risks of damage.

 

[onefastgn]

opps

 

[azgn]

what Louie said......leaner af may work on a dyno, but it sure won't at the strip/street

 

[2QUIK6]

Originally posted by Louie L.
In my experience you dont want anything lower than 11.8-11.5.
The trade off in power If any is not worth the risks of damage.

Isn't going lower actually getting richer and higher would be getting leaner?

 

[Turbo6TA]

12.0 -1 too lean on the dyno

For some reason, I could not post to my original thread ...

So, your saying that I don't want to be any leaner than about 11.5 -1 to 11.8 -1

12.0 -1 would then just be a little too lean to be safe in a boosted motor.

It's interesting that in a non-boosted car, max power is made right at 13.0 -1 air/fuel ratio (of course this would be way to lean on a boosted motor)

 

[GNVYUS 1]

Most of the time people say that 12.0 is lean on the dyno due to street load leaning you out even more when you get off the dyno.

 

[Turbo6TA]

Thanks much!

 

[Turbo6TA]

I gather that he means anything leaner than about 11.5 to 11.8 -1 is just too lean on the dyno.

I did a search here and it looks like an AFR of about 11.5 -1 is just about right on the rollers as long as it's not detonating.

Thanks to all that helped me with the info.

Ron,

 

[bruce]

Originally posted by Turbo6TA
I am going to the dyno this weekend ...

Just wondering what air/fuel ratio is pretty much safe when running the stock timing, 16 psi boost and pump gas and pretty much a stock motor.

I have tuned with about 790 mv on the O2 sensor, but I think a fuel/air ratio measured on the dyno would be a much better tune.

When your rely on someone else's Wideband, there's always the chance that it's off. Tune for best power, Not to get a *magic AFR*. Then when your done, add a few percent more fuel.

 

[Ormand]

Yes, what Bruce said. Every engine is a little different, and every A/F meter will read a little different, too. There is a possibility of getting "rich" knock, which is just as bad as the lean kind, so start out safe, then turn up the boost, add fuel if needed, watch the knock sensor!

 

[Louie L.]

Yes you guys are correct as i was. He asked for a specific number. If using 12.1 as a reference start , well thats just too lean.

 

[mybuick]

another way is to look for .800's on the o2 reading at full throttle

 

[Louie L.]

You could do that if you had a reference point to start with. .800 on the Scanmaster or Direct scan does no equate to any specific A/F unless you can reference them to each other some how. On top of that no 2 cars are alike.

 

[bruce]

Originally posted by mybuick
another way is to look for .800's on the o2 reading at full throttle

When compared to a WB, I've seen .81 read 12.3, and 11.8.

I wouldn't rely on that as being accurate.

While using the oem O2 as a rough indicator was accepted at one time, with the advent of econo WB's, there's just no reason to risk a motor over misleading AFRs, IMO.

 

[2QUIK6]

On the dyno, my car had an AF of around 11.5-12. It started off with an A/F around 10.0 and after cutting some fuel until I started seeing knock got it to 11.5-12.
My O2s during all the dyno pulls stayed around .840-.850mv. I was thinking something was screwy since the A/F was up to 12 at some points. While on the dyno, cutting fuel effected the A/F but not the O2s.

Anyway, I left it, and then with the same exact tune, driving back home from the dyno at WOT the O2s were down to .790-.800mv.

So as mentioned above, the additional load of the car in real life driving does help lean it out from what is read on the dyno tuning.
I wonder now if my A/F is even higher now than 12.0 on the street than what it was on the dyno?? Still no more than a degree of knock.

 

[V6POWER]

Do Mustang brand dynos factor in the load on the street? I know they read less hp/torque than the other dynos.

 

[2QUIK6]

Originally posted by Look Quick
Do Mustang brand dynos factor in the load on the street? I know they read less hp/torque than the other dynos.

I don't think any of them "factor in the load because every car weighs different, I'm sure they all use a set weight/resistance on the roller. As far as hp/torque being less, it all depends on which "standard" is used, such as SAE, they should all be close to the same...there are other "filter" they can use on the software to "smooth" out the curves etc...but generally SAE numbers are just a tad lower than the uncorrected numbers.

 

[Dan K]

I've set up a couple of friends cars with my Innovate WB, and found it to be really close to the a/f ratio on the dyno.
Not sure how much I believe the "load" factor.
Then again, I guess it could have been the difference from my wideband to the one being used on the dyno?

 

[703crewchief]

Dyno's Can factor in load!!!!

Almost all brands of chassis dynos can factor in load. This includes weight and wind resistance, but most shops do not spring for the optional Eddy-Current generators as they up the cost considerably for a dyno. Mustang Dynos with the EC can actually simulate a full quarter mile run from launch to high gear and are extremely accurate. But to answer the question of the original post, off the dyno we see the A/F go .2 to .5 leaner than on the dyno. If you find a dyno with actual load simulation then your A/F will be the same as on the dyno,street, or track.