[shrubby]

After installing a supercharger I feel like the car's shift points are not quite right. I seem to get more lag between automatic gear shifts. My installer who supplied the tune did not modify anything related to gear shifts as far as I can tell. I compared the current tune to a stock tune and there were no differences with regards to transmission settings.

I am very new to using an HP tuner to make adjustments and wondered a couple of things.

First, a little background on what I'd like to correct. When putting just enough pressure on the accelerator to maintain a constant speed and then encountering a hill or another car that needs to be passed, the transmission tends to keep the car in the same gear for too long before downshifting, making the car feel 'bogged down' until it finally switches gear. If I give it a little more gas, the shift is nearly instantaneous but then I'm going faster than I want or needed to. The amount of lag seems to correspond to which driving mode I'm in with Tour being the worst offender.

1) What is the best approach to take to correct this behavior?
2) Is this something that someone just learning how to use a HP tuner should try to tackle?

I've read some posts where it was advised to modify the shift points and I've looked through the tables but am still not sure if this is the correct solution.

Any advice would be great, the behavior is really annoying and the guy that tuned it won't be back until a week after SEMA and besides, I want to learn the tuner myself.

[TSloper]

If you have your dyno torque curve I can give you the proper shift points. I created a Matlab script to calculate them for each gear based on the TQ curve.

If you have the actual Dynojet file (assuming Dynojet was used) it will calculate them in about 3 seconds.

Tim

[shrubby]

Originally Posted by TSloper

If you have your dyno torque curve I can give you the proper shift points. I created a Matlab script to calculate them for each gear based on the TQ curve.

If you have the actual Dynojet file (assuming Dynojet was used) it will calculate them in about 3 seconds.

Tim

Thank you, appreciate the offer.
I do have them. Unfortunately it appears I only have the one from before the heaaders were installed. The other runs don't appear to be on the drive. Will that work? The difference was about 35 HP. I can also go get a copy from the shop tomorrow...

I PM'd you a link. Thanks again.
Chris

[TSloper]

Calculated A8 Shift Points
==========================

1st: 6400 RPM [40 MPH] [5633 ft/lbs -> 4448 ft/lbs]
2nd: 6400 RPM [62 MPH] [3669 ft/lbs -> 3133 ft/lbs]
3rd: 6400 RPM [89 MPH] [2570 ft/lbs -> 2411 ft/lbs]
4th: 6400 RPM [109 MPH] [2088 ft/lbs -> 1869 ft/lbs]
5th: 6400 RPM [145 MPH] [1569 ft/lbs -> 1460 ft/lbs]
6th: 6400 RPM [184 MPH] [1235 ft/lbs -> 1185 ft/lbs]
7th: 6400 RPM [217 MPH] [1050 ft/lbs -> 951 ft/lbs]

Tim

[shrubby]

Thanks Tim - when I get home tonight I'll give it a shot

[PRAY]

HPT must have different tables. I am assuming your shift points are calculated in tq? My shift points are represented by mph and rpm. mph being lower for shift lead. I think I am confused by what you posted or it just doesn't correlate because of the program I am using.

[TSloper]

Let me take a look at EFI Live to see how it differs from HP Tuners.

[TSloper]

Nope same data... EFI Live just doesn't break it out the same in terms of graphical layout. The numbers posted are the new shift points calculated from the Dynojet torque curve (converted to axle torque in the Matlab script).

The table shows the new RPM that should be set in the WOT RPM table. If the RPM were lower than the stock RPM you would also need to make sure the MPH table is drop accordingly as well.

[PRAY]

Okay, I got what you are saying now. I had a concern that the OP would put in both the RPM and MPH you listed. Not just leave the MPH where it was and only adjust the RPM.

I did notice at the track the other day that my commanded RPM changes were not really implemented by the computer. Especially not 1st gear. I have a feeling that both the MPH and RPM will have to be adjusted some to keep the same split/lead time from the MPH table to trigger at the correct RPM. I will have to test it.

On the street it is much worse in first. It isn't even coming close to the commanded shift RPM. I had to use the launch control in Comp Mode to not just blaze the tires. It was shifting at 6,200ish at the track with me commanding 6,600. 6,600 was just a last ditch effort to get it to shift higher at the track in D so I could take advantage of the advantages offered in D over Manual shifting. On the street is shifts 1st at 5,500ish as usual.

[sub_ETCS_ret]

Did you update the shift points? Just curious.

[shrubby]

Originally Posted by sub_ETCS_ret

Did you update the shift points? Just curious.

Not yet. I am still trying to learn the HP tuner and wasn't sure exactly how to apply these. I've been researching and I think I have something to try tonight when I get home. I'll update when I do.

[sub_ETCS_ret]

Originally Posted by shrubby

Not yet. I am still trying to learn the HP tuner and wasn't sure exactly how to apply these. I've been researching and I think I have something to try tonight when I get home. I'll update when I do.

Interested in hearing how it goes. Did you get the standard or pro version of HP Tuners?

[shrubby]

Originally Posted by TSloper

Attachment 828714


Calculated A8 Shift Points
==========================

1st: 6400 RPM [40 MPH] [5633 ft/lbs -> 4448 ft/lbs]
2nd: 6400 RPM [62 MPH] [3669 ft/lbs -> 3133 ft/lbs]
3rd: 6400 RPM [89 MPH] [2570 ft/lbs -> 2411 ft/lbs]
4th: 6400 RPM [109 MPH] [2088 ft/lbs -> 1869 ft/lbs]
5th: 6400 RPM [145 MPH] [1569 ft/lbs -> 1460 ft/lbs]
6th: 6400 RPM [184 MPH] [1235 ft/lbs -> 1185 ft/lbs]
7th: 6400 RPM [217 MPH] [1050 ft/lbs -> 951 ft/lbs]

Tim

Question, under full throttle RPM (if I am looking in the right place, still trying to learn the tuner) Do I just need to update 'Normal'?

[TSloper]

Normal is used for Ice/Snow and Touring.

B tables are used for Sport and Track.

I just update all 3.