Here's a little tip that I have found while working with my car, the PFC, the Datalogit, and a wideband...

If you have a dual stage boost controller where you can program two boost levels and switch back and forth between them.... Be aware that your AFR will likely change by a bit depending on what you have your controller set for.

Let me explain.

On my car, I have a Profec B set for 10 and 15 PSI. Let's say I run at the 10 PSI setting, and then floor it at wide open throttle, measure the AFRs, and get them where I want them at say 11.5:1. Now, later on, I bump the controller to the 15 PSI setting and now I drive at PART THROTTLE in order to "hold" only 10 PSI. My AFR will be a bit richer (I find by around 0.2-0.4 points on my car).

So the flip side of this is... if you tune at the "high" setting, then you later reset your controller to hold less max boost... you may run a bit lean.

This is being caused by the fact that when you're at the 10 PSI setting, you can hold the throttle wide open and still only get 10 PSI. When you are at the 15 PSI setting trying to get only 10, you need to hold back and not open the throttle that last bit... you're strangling the engine a bit.

Anyhow, feel free to comment... I'd like to see if others have seen this on their cars.

I guess the short version is, "if you run a two stage boost controller, tune each setting at WOT individually".

Brian

 

Probably due to the difference in TPS voltage.

Who tunes at partial throttle anyway except for idle and cruise?

 

Hehe, I do... I like to toy with people that are racing with me, so they think they're winning... then I mash it all the way!

 

I tune for partial throttle too....and on/off light throttle....
Because during turn and corners, you need those to be very very smooth.....

 

thanks for the tip. i have an unrelated question though. do you have the spec 2, and if so what are the %'s that you entered for those two settings?. thanks.

 

Instead of partial throttle, I do full throttle in 4th gear from 2k, 3k, 4k, and 5k from 0 to 12PSI boost. Then I set the AFRs so that this transition from 0PSI to 12PSI (rows 10 - 17)goes from 14.7 to 11.5 uniformally. I run 11.5 for 12PSI for summer and about 11.7 for winter. This 11.5 - 11.7 difference is controlled by the AIR TEMP vs INJ map

My fuel for P10 - P17 is much richer than what the PFC comes with in this area. Befor it was still in the 14s even at row P15.

Now my transistion is stronger and smoother.

 

Interesting. I had inquired about a similar scenereo when I was dyno tuning my car. My theory was that the AFRs would change because I have an open wastegate. So when I'm running at the boost setpoint, I'm getting a lot of exhaust dumped straight out versus through a slightly more restrictive exhaust, which by my reasoning should affect AFRs on a MAP-controlled car. Of course they just said "don't worry about it."

If I could ever get my AEM UEGO working, I wouldn't worry about it.....

 

How do you control the boost from 0 to 12psi boost? Would not it build boost to 12psi automatically when you set it to 12psi. And the least we can set it to is still building 7psi the least.

 

Boost is set to only 12psi.
We are making mutliple runs from different starting rpms from vacuum to 12psi with a floored throttle. This causes the PFC to tranverse mutiple areas of the map. From lower to higher columns.

The AFRs from this area allows you to tune this transition area.
My vacuum cruise area is tuned for about 15 to 16FAFR. That from P4 to P9.

P10 (0 boost) is set for about 14.7AFR.
P17 (12 boost) is set for 11.5AFR.

Between P10 and P17, AFRs linearly increase from 14.7 to 11.5.

 

how do u tune for partial throttle and on off throttle. my car seems to stumble and break up?

 

I tune the off areas like Chuck described. Plus we typically look at the actual values in the rows and columns to make sure that the values change in a logical manner, meaning the fuel delivery increases for increasing boost and increasing rpm up to torque peak etc. I've been surprised what a few tuning sessions did to the rest of my map and have had to do a bunch of cleanup work later to rid the map of rich/lean spots that may be a problem later at slightly higher or lower boost.

For tuning the partial throttle boost areas I prefer to use the boost controller to tune the center of each P row at and above spring pressure. For lower boost values on a track car I think Brian has a good idea. Tuning by spoolup transition is ok for the low and mid rpms but for a track car you may need to tune transition at every rpm column; some corners you hold 7000 rpm thru the corner then mat it at the apex. I have never datalogged transition from vacuum to full boost at 7000 rpm!