Complete re-tune needed for pulley change??

[Batmanntexas]

So I just swapped from a 3.625" pulley to a 3.00" pulley on my Whipple. That was the only change. I don't really have a lot of tuning experience, so my question is do I need to re-tune the entire car, or can I just tweak the MAF/Frequency curve to compensate for the additional airflow?

According to some math I did, dropping the pulley down 5/8" resulted in about a 20% increase in blower speed. Does that equate to the same air mass increase of 20%?

I started it up with the current tune file, and it was idling fairly lean (15-16 afr), so I shut it down.

I have initially made a 10% increase across the board for the MAF/Frequency curve, but haven't flashed it yet.

Both tune files are attached for reference. Thanks for the assistance!

-Scott
2012 Camaro SS - Whipple CR tune 7.hpt
2012 Camaro SS - Whipple CR tune 7-3inch_pulley.hpt

[5FDP]

Let it run longer than a few minutes if it was lean/rich directly after a flash, see if it corrects itself and the fuel trims aren't all over the place as things settle back in line.

What exactly the tune will need it hard to say, you will have to do some logs to see if you need to add/remove any fuel.

A full revamp won't be required, just where you are in boost because the BBV is still going to do it's job like before.

[Batmanntexas]

@5FDP - appreciate the response. I haven't flashed it yet, as I wanted to see if I was at least thinking somewhat straight. I will flash the modded file tomorrow and collect some data logs. I'll report back on my progress.

-Scott

[Batmanntexas]

Alright, so after flashing the new tune, I drove it around for awhile to collect some data. I logged it for about an hour. Seems to drive fairly normal, however I did notice some issues in the log file. I have attached 3 exports from the log file.

From the log file, I can see that DEN/CYL is now at 2.0+g/cyl at boost, however, the main spark tables stop at 1.34g/cyl. Do I scale the spark table to go to 2.1 to accommodate the new values? I also noticed that I have maxed out the MAF card, as it flat-lined at 655.35g/s. Do I scale that as well?

Would I be better off to just scale the entire tune by a factor of .5?

Appreciate any feedback.
Export1.hpl
Export2.hpl
Export3.hpl
Export4.hpl
2012 Camaro SS - Whipple CR tune 7-3inch_pulley.hpt

[5FDP]

That channel stops reading at that value, you are still under the MAF hz limit and you can still use dynamic airflow.

You can make the timing table go to 2.00 if you want, then interpolate down.

Lots of knock in those logs too.

[Batmanntexas]

Yep, I noticed all of the knock as well. THe timing has been pulled down some.

I have emailed HPT Support about a custom OS that would include a change to the spark tabled to make them mirror the VVE table. I would like to keep the current resolution of the spark table, just have it go all the way up to 2.1 instead of 1.34. We'll see what they come back with.

Currently out of town for work, so I can't do anymore logs until I return on Friday, and flash in the updated tune file. More to follow.....

-Scott

[pannetron]

When I tried smaller pulleys on my e-force supercharged LS, I noticed that the AFR went a little richer with smaller pulleys. My guess is that the MAF was reporting more air ingested but not all of that air was actually making it into the cylinders.

[sgod1100]

cruising areas probably won't change too much due to the bypass valve is being used and the narrowband sensors will likely make up for the small changes. On my ctsv i went from a 2.55" to 2.35" pulley (not as drastic of a change as you) and the cruising areas were virtually the same. Now once in P.E. mode (i.e. open loop) thats where you will probably have to adjust the maf curve as there is no feedback from any type of o2 sensor to account for the additional air being shoved in