Gear use on dyno

Hey Andre,

I have a couple of questions for you with regard to dyno tuning.

The first concerns the gear use while on the dyno. In the course you said you used 4th gear to tune the vehicle in steady state. I have no experience tuning on the dyno so please excuse me if I am mistaken, but I find 4th gear for use at 1500rpm-2000rpm quite high a gear to be using. Is this the norm to use 4th gear all the time like this? Does it matter what gear the car is in really?

Will the selected gear affect the ignition tuning side of things?

Also I see you said that you use 1st gear to access areas of the map you could not access particularly the low load areas. What about areas that you just cannot reach even when using first gear? What would you do in a case like this?

My next question is with regard to the 0rpm column, obviously I know the engine can't be run here but we must input something....we can't just leave it blank. What do you suggest here? The same goes for the 500rpm column. What is your suggestion for these two columns? Just copy the values from 1000rpm back across ?

Chris.

4th gear, or whatever gear is closest to 1:1 is normally a pretty good place to run the car. If you use a lower gear, this will result in a higher torque multiplication through the gearbox and on a roller this may cause traction problems. On a dynapack hub dyno wheel spin isn't obviously an issue, but with the larger torque multiplication, you can often find the dyno struggles to control properly if you try running a powerful engine, or one with erratic VE changes in 2nd gear for example.

When it comes to steady state at 1500-2000 rpm, it doesn't really matter specifically what gear you're in - It's the rpm that counts. I use 4th gear almost exclusively and don't have any issues.

1st gear may not allow you to reach some very light load areas of the maps, but the chances are that if you can't get here on the dyno, then you will struggle to drive in this area on the road. This is one reason though that I'm a big advocate of confirming a tune on the road after the car has been on the dyno. It will let you check and confirm the light throttle areas. Also you will find that what you can access on the dyno will depend on the type of dyno. For example a dynapack has almost zero inertia so as soon as you back off the throttle the car will simply slow down. On a rolling road there is a little more inertia that lets the dyno maintain speed even at closed throttle for a short time.

Below the areas you can successfully tune I will follow the general shape of the fuel and ignition tables. I use this technique in the 0-500 rpm columns as well. This area is only really going to be accessed during the cranking and start up phase and the tricky part is that the fuelling here will also be influenced by cranking enrichment tables. It's obviously impossible to accurately tune the engine in these areas but since we can expect that the shape of the engine's VE curve should be relatively smooth and consistent, following the trend we have in the fuel table will have us close enough that we can correct any small deficiency with the cranking tables.

Understood Andre,

Just one more question. When you refer to cranking tables are you referring to warm up enrichment tables? I can't recall hearing you refer to cranking tables in the courses this is why I ask.

If this is an entirely separate table, would you guys consider a webinar in setting this up?

Chris.

Sorry I should have been a little more specific. Not all ECUs will have a cranking enrichment table. In these ECUs you need to adjust the 0 rpm 100 kPa zone, and surrounding sites to achieve good clean starting. If the ECU has a crank enrichment map then that will also affect the starting. Warmup enrichment usually becomes active once the engine is deemed to be running.

There is a lot of information about this in the cold start webinar we did on the Link G4 platform here - https://www.hpacademy.com/previous-webinars/tuning-cold-start/