View Full Version : VE table tuning on the street vs on a variable-load dyno


kyle97
11-20-2006, 04:06 PM
I had a frustrating argument with a professional tuner today reguarding using a mustang dyno to tune VE tables (Using EFILive w/ LC-1 to do AutoVE).

I have been trying to do a SD tune on the street, but getting 50+ samples in all of the different cells is somewhat difficult. I'm really close (+-2 % in most cases) I know plenty others have done it before, and i know i could nail it down eventually -- in reality im probably just being too anal about it. However, i have heard (some post on here) that you can use a variable-load dyno to get lots of samples in all of the cells. I wanted to try this idea out as it seems alot safer, easier, and faster than trying to hit all the cells on the street.

There is a mode the mustang dyno can operate in that will apply whatever load necessary to keep the engine at a given rpm. If you set the rpm to 3000, you will be able to accelerate the car on the dyno up to 3000 rpm, and then the dyno will impose a load to maintain that rpm. You could go 10%, 50%, WOT, whatever, but the rpm will not rise/fall. That seems perfect to me for VE tuning. For any given rpm, you could set the dyno to load up at that rpm, and then apply varying amounts of throttle to hit all of the MAP cells for that RPM.

Has anyone done this and can attest to whether or not it works? The tuner i was talking to said that the engine loading would be different on the street and therefore this wouldnt work.

brad8266
11-20-2006, 04:39 PM
I am sure it would not be 100% accurate compared to the street, although it seems like it would work very well. I have always used the street to tune for 2 reasons:
1-Dyno time is too damn expensive, escpecially when you want an in-depth tune.
2-The street is the realest it gets.

Vents
11-20-2006, 04:39 PM
i would tend to agree with the dyno op.

it seems VERY apparent that on the dyno's i've used/seen they tend to be a point or more off on WOT AFR. not good. aside from that, you mentioned that +/- 2% was something that you were being too "anal" about. if this is the case, you really wont be happy with the results of this new idea once it comes time to running it on the street.

BTW you can pretty much get close enough (+/- 5%) with your same SD method just correcting the onesy twosey's once cell at a time. or, get nuts and make your own correction algorythim. ;D

SSpdDmon
11-20-2006, 04:46 PM
I haven't done it, but it seems fairly straight forward to me. The dyno applies a resistance to the rollers by using a brake or something along those lines. The way I would hit different cells is set the cruise (or use my right foot) to hold the car at 1200, 1600, 2000, etc. RPMs. Keep the car at those RPMs and increase the resistance until the MAP kPa's read where I want them. So if I'm holding it at 1600 RPM, increase resistance so MAP reads 40kPa, 45kPa, 50kPa, etc. The idea is to get in the center of the VE cell as the PCM interpolates between cells. Even after this though, you won't have "0" fuel trims all of the time. The resolution in the PCM, variability in weather conditions, and what not makes that virtually impossible. But, that's how I'd go about it.

kyle97
11-20-2006, 04:49 PM
I agree on the cost thing, thats definately keeping me away. The thing i cant get is -- how is tuning the VE table for a given load cell different on the street vs on the dyno? I mean, I could jack up the car, put the parking brake on and log data and accomplish the same thing right? It seems like a load is a load as far as the engine is concerned. And each VE cell corresponds to a certain load, regardless of the source.

I thought the foundation of SD engine management is that the engine has a certain VE for a given RPM and MAP. It seems like the loading source should not matter if VE is truly a function of MAP and RPM.


At a certain point i will have to give up on getting everything "perfect" but i guess im just not there yet :)

Country Boy
11-20-2006, 05:09 PM
I did all mine on the street. It was a PITA and took some time, but its about dead on. The street is where I drive and the street is where Ill tune it.

brad8266
11-20-2006, 06:59 PM
I did all mine on the street. It was a PITA and took some time, but its about dead on. The street is where I drive and the street is where Ill tune it.
:werd:

Black02SS
11-20-2006, 07:04 PM
I use the street for 99% of my tunes. The dyno is nice to find where it peaks and to see the power you are putting down. If it is tuned WOT on the dyno, then we go back to the street at then end to fine tune the AFR.

black_z
11-20-2006, 08:32 PM
I tune VE on the street and WOT on a mustang dyno.

rmitchell242
11-20-2006, 09:15 PM
another problem with tuning ve on the dyno is that the airflow is not the same on the dyno as it is while traveling xxxmph on the street.

Bink
11-20-2006, 09:17 PM
On the dyno you will only have a narrow window of LTITs and STITs (unless you frquently stop and let it idle) and this does effect both your AFR and resultant VE values. Nothing is perfect. :D

gametech
11-21-2006, 12:16 AM
Load bearing dynos are great for getting your tune close without the hassle of wrecks and police. The street or track is, however, where the final adjustments must be done.

Doc
11-21-2006, 07:33 AM
Not a whole lot of real world data here in this thread. First off, there is nothing wrong with street tuning. It will take you more time for safety reasons. My real world tests on a DynoJet with a Road Runner have proven to be interesting. The Dyno I was using did not have the load control feature- no problem, I just used the dyno's brake and my right foot to hold the car in the cells I needed. Very fast for collecting a lot of data and watching the PCM react to the changes made in real time. All this and no worries about cops, and little kids running out in the street. Realistcally I understand not everbody has access to a dyno or RR for that matter, I just wanted to throw in some real data to the original posters question. As far as LTFT affecting tuning on the dyno...I turn off all modifiers while tuning the VE table.

Bink
11-21-2006, 05:54 PM
Not a whole lot of real world data here in this thread. First off, there is nothing wrong with street tuning. It will take you more time for safety reasons. My real world tests on a DynoJet with a Road Runner have proven to be interesting. The Dyno I was using did not have the load control feature- no problem, I just used the dyno's brake and my right foot to hold the car in the cells I needed. Very fast for collecting a lot of data and watching the PCM react to the changes made in real time. All this and no worries about cops, and little kids running out in the street. Realistcally I understand not everbody has access to a dyno or RR for that matter, I just wanted to throw in some real data to the original posters question. As far as LTFT affecting tuning on the dyno...I turn off all modifiers while tuning the VE table.

Do you disable "Idle Learn" , LTITS and STITs??

ty_ty13
11-21-2006, 09:37 PM
Not a whole lot of real world data here in this thread. First off, there is nothing wrong with street tuning. It will take you more time for safety reasons. My real world tests on a DynoJet with a Road Runner have proven to be interesting. The Dyno I was using did not have the load control feature- no problem, I just used the dyno's brake and my right foot to hold the car in the cells I needed. Very fast for collecting a lot of data and watching the PCM react to the changes made in real time. All this and no worries about cops, and little kids running out in the street. Realistcally I understand not everbody has access to a dyno or RR for that matter, I just wanted to throw in some real data to the original posters question. As far as LTFT affecting tuning on the dyno...I turn off all modifiers while tuning the VE table.


i've done my tuning on the street so far with the RR... it makes every thing very simple... but now i understand why people have to use dynos.. when running about 55 and cracking the throttle in high gear (A3 tranny) can lead to high speeds very fast..... although my drivabilty was almost created instantly with the RR.....

i have never tuned anything before and cant imagine tunning with out my nifty RR...

Doc
11-22-2006, 10:25 AM
Do you disable "Idle Learn" , LTITS and STITs??

All modifiers, Idle, Fuel Trims, DCFO, MAF, etc. anything that gets in the way.