What would you do first tune on a Dyno or the Street?

[Mr Hemi Head]

I recently street tuned the GTS with Roe S/C(5lb), W/M, Bellanger headers and was able to get the A/F in the 11.5 range from 2K to 4.5K rpm. This was done in 3rd gear tuning with a Wideband Commander and VEC2 software.

Several weeks later dynoed to check A/F to 5.7K rpms and get a HP reading. The A/F was 10:1 in 4the gear pulling in the same RPM range during street tuning. What would cause such a drastic difference? Could temp and humidity cause this? The dyno room was at 27%, outdoor humidity was closer to 47%. Could the gear used be a factor?

The rwhp was 510, torque 537.The DynoJet was the model with the smaller drums that read slighly lower. Rick

 

[Bob D]

I would tune on the street. If you tune to a perfect A/F on the dyno you will be too lean on the street because there's hardly any load on the dyno. You won't get max dyno numbers but your A/F will be safe.

 

[Russ M]

Dyno always first.

Once you get your numbers in a safe happy place then you can do minor adjustments for street driving.

The drum on say a dyno jet is 5000lb's I believe, that is more load than on the street. Unless you are doing hi speed testing.

 

[Mr Hemi Head]

I would tune on the street. If you tune to a perfect A/F on the dyno you will be too lean on the street because there's hardly any load on the dyno. You won't get max dyno numbers but your A/F will be safe.

We see many Dyno graphs posted here where the A/F is a flat 12:1. So this is not realistic? Are they detuned later to prevent detonation?

 

[plumcrazy]

what does sean say to do ? ? ?

 

[Mr Hemi Head]

Re: What would you do first, tune on a Dyno or the Street?

what does sean say to do ? ? ?

Sean said closed track tuning is best however there are few tracks LOL in this area to do that safely. On this forum most go with dyno tuning, I thought I would try that.

 

[Jack B]

Re: What would you do first, tune on a Dyno or the Street?

The viper pcm has a not so funny quirk somewhere around 85 degrees air temp. It almost seems that there is a factory error programmed into the wot map. As the temp gets lower the car will start to run richer (due to less dense air) but, the pcm seems to add additional fuel (which makes no sense) thus, causing the car to get a whole bunch richer. Some people have been adding a resistor to the IAT sensor so that the PCM doesn't see any temp change.

 

[Schulmann]

Re: What would you do first, tune on a Dyno or the Street?

Mr Hemi Head,

Read this post on the WBC.

There might me a little difference between the Street AFR and the Dyno AFR. However I am talking about a little difference.


I have made a very disturbing discovery on WBC. It is NOT ACCURATE. It looks like a cheap toy from China. I am in contact with DynoJet to get some explanation on this. Over this week-end I replaced the oxygen sensor and moved it to a different location. I haven't had time to test it.

WBC is unable to measure AFR below 12.0 accurately over a long period.

WBC uses the Bosch 258 007 206 sensor which is virtually unknow.

Other tools like LM-1 use the Bosch 258 007 057 sensor which is higher quality and should last longer.


I did all my tests on the street ...