I recently got nitrous on my car and tried it at the track but it keeps bumping the limiter just a bit. I was wondering do I just lower the shift mph or is there more to tuning the trans when adding nitrous?

I'm hoping its just a shift point adjustment because I'd love to see what this car can do on the spray.

Thanks

 

Try dropping the WOT shift speed(s) down by a couple of mph on the shift(s) where it occurs.
Please note that you need to change the shift speeds in the 100% TPS column of the part throttle shift speed tables too, to match the new shift speeds in the WOT table, to avoid any conflict between the two tables. I had to do this the other day myself, based on Chuck COW's instructions (thanks Chuck!) when I couldnt get my car to shift properly by just tinkering with the WOT tables.
Please also note that with nitrous, you're inputting a lot more torque than off the spray, so you may need to up the shift pressures and tighten up the shift times, as well as bump the max line pressures up. These transmissions are very complex and sensitive to lots changes you make in even the ECM tune, even MAF scaling, which is why they can fail easily with even the best of internal upgrades.
If you don't already have a tuner on hand, I would urge you to find one that has specific experience with the tuning the 6L80, and get him to retune it for the nitrous.
On the other hand, if you're only using a small shot of nitrous (125hp or less) and if it was already tuned and it's only nudging the limiter slightly on the spray, you should be okay with just tweaking the shift speeds. Good luck and let us know how it goes.

 

Thanks for the info! The part throttle thing might be my problem because it seemed to just kiss the limiter if I ran it with my na tune or dropped it a few mph. The trans is already tuned by century/subfloor so the tune should be fine. I have a dual plate setup 1stage has a 75 shot and the other a 150, I don't run them together. I'm hoping the 150 isn't too much.

 

Okay. Well, hell, if you have subfloor tuning it, then you can't ask for anything better than that!
I would definitely take whatever advice he gives you on it.
You should be fine with a 150 shot, IMHO.

 

looks like the part throttle thing was my problem. I took it out while ago and it shifted perfect, thanks for the help. I had a 6 mph difference between the two so i guess that would cause some confusion in the computer haha. Now i need to get to the track again!

 

Excellent! Glad to hear you got it fixed. Now carry that beatch to the track and let 'er eat!

 

Dont change any shift speed. Find a different tuner. All speed setting can be the same on motor on spray when the tune is right, speeds are not the problem and will only blanket the issue. Also 6l80e love to sprayed through the shift and the only way I would recommend doing it.

 

I had to change my partial throttle 100% shift speeds because those and my WOT had different shift points which seemed to confuse the computer. After adjusting those it seemed to work great on my street pulls but when I went to the track it started bumping the limiter again. Some say it could be the converter not liking it and some say it could be a clutch pack going out. I made another post showing a screen shot of one of my scans, it acts kinda odd on the 2-3 shift.

I'll most likely be getting in touch with you this summer after the spring season of work. I'm looking at changing my setup a little before I start tuning on it too much.

why would you recommend spraying through the shift vs not? It seems like that would put a lot more stress on the shift/clutch packs.

 

I tune for a living so I will PM you why lol.

 

Why PM? I would like to learn a thing or two........

 

 

I think he is trying to avoid this thread going off subject.

I.e. He says not to change the shift speed and why and then another tuner doesn't agree etc and then the thread turns bad and no more useful info can be gained.

 

Ya thats about how it goes! Everyone has a different strategy of going about tuning but imo some of them are better than others!