A/F differences between Dyno tuned and street tuned?

[Country Boy]

What kinds of differences has anyone seen from the dyno to the street or vise versa.

[EC_Tune]

~5 HP NA
~5-25 HP FI

Without a measuring stick you don't really know what your engine likes and where. However I always like to run them on the street after the dyno as some vehicles get away with more timing on the dyno than on the street. AFR usually remains very close street-to-dyno.

[MNR-0]

I have found that on some occasions the AFR difference is as wide as 0.3-0.5. But generally a dyno AFR is richer than a street AFR. From my experience anyway.

[Country Boy]

Interesting... Ive always heard/ read that the AFR will vary drastically if tuned on the street and then taken to the dyno because of the air mving around the car and the true load.

[eficalibrator]

Interesting... Ive always heard/ read that the AFR will vary drastically if tuned on the street and then taken to the dyno because of the air mving around the car and the true load.

There are plenty of dynos out there that can give the same (or more) loading compared to the street. Eddy current dynos are quickly becoming the norm for tuning for a good reason. Beyond that, it's up to the tuner/operator to make sure things are done right.

Properly tuned, there really shouldn't be any drastic difference in AFR between either tune if measured in the same location under the same load. The engine wants what it wants, and there's more than one way to find that.

[Country Boy]

Im meaning on a dynojet where there is no actual load.

What Im getting at is 3 of the cars I tuned went to a dyno day this weekend and all were tuned on the street with my wideband to a 12.8 AFR at WOT. On the dyno they were very erratic and the AFR went into the 11s and even 10s.

[blucreek]

Did they use a "Dynojet" wideband setup on the Dyno, aka- Sniffing through the tailpipe vs. in stream readings on the street.
My exp. with Dynojet setup on the Dyno, is the DJ WB usually read a little leaner and erratic until WOT while sniffing.
But take the same car on the Dyno without changing any of the tune, we inserted the DJ sensor instream and the AF would fall .2 - .4 or so.
Placement of sensor is key.
Also you have to remember unless the DJ sensor is new, and the complete system is clean(DJ Air Pump) readings can be skewed.

chris

[Alvin]

I have a 224xlc which is a loading eddy current equipped dyno jet.

I can run the car inertia only or load the car however I like. I can make it feel like your trying to pull a boat down tthe track if I wanted to. Since getting this new dyno I can say that I have not had 1 GM car change AFR with load vs. no load. I have seen fords change AFR.

I suspected that the AFR was changing on the track also however that seems to be completely wrong.

The loading dyno is still especially useful to slow the cars down to capture good data and load turbos. I'm very happy I purchased it.

I'll be the biggest difference you guys are seeing is in the wide band. I do not trust LC1's at all and i'll bet your varience is because of the LC1

[Country Boy]

So tuning on a dyno and then driving on the street resulted in no change to the AFR? Interesting. I may just switch my tuning to a dyno then.

The dyno had a rigged AFR meter. It was a 1.5" piece of pipe with a O2 welded in the top of it and part of the pipe stuck in the tail pipe. I know its not accurate.

I was mainly concerned with the AFR changing from tuning on the street and they dynoing the car and vise versa. I do my tuning with a LM1.

[Alvin]

I can load the cars down on my dyno to make them feel like they are pulling a trailor up a mountain if I wanted... Its very interesting that the AFR doesn't change. You'll even see same characteristic curve..

[WS6FirebirdTA00]

I have several logs from dyno runs on different dynos (unloaded) and logs on the street right after with air temperatures matching, I have seen about 0.5:1 difference on some occasions. This is also on LM1, Autometer, AEM, and another one I can't remember the name of lol