1997 Sunfire 4 spd automatic repair & modding
 

http://ecomodder.com/forum/emgarage-...575cb2c060.jpg

So, time to start bumping the mileage up on another car. This time around the lucky contestant is a 1997 Pontiac Sunfire. It has the 2.2L mated to a pretty inefficient 4 speed automatic transmission. While the manual guys with the same engine are getting mid 30s to 40s for mpg, the automatic guys seem to have trouble besting 30 from what the garage here says.


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For the past few months, my fiancee has been driving the car. However, she is going on a trip later this month and will be taking the Prius. So, I figure now is a good time to get her acquainted with the car before the long trip. Thus, I now have the Sunfire. She has been doing pretty good considering the ridiculous cold winter we have had, and the fact that her commute has lots of stoplights. She is a great ecodriver in training and takes well to new tips and tricks. :thumbup: She will probably keep the Prius from this point onward as she has the longer commute between the two of us, and that'll save us the most on cashola.

So, I am starting to lay out some plans for the Sunfire. Of course, I'll probably run one tank through it to get a baseline of my commute and my driving with it. The only "mod" currently is 40 psi in the tires. I don't even have a SG in it (yet).

Today is my first day with the car besides the occasional trip here and there. The first thing I looked out for was when the torque converter locked up. I know from fueleconomy.gov that it does have a locking converter. Finding it wasn't too difficult, but the non-aggressive programming was disappointing to learn. I found that the torque converter locks up at just over 45 mph, and it kicks out at about 42-43 mph. Thankfully, about 5 out of the 7 miles of my commute is at 45 mph, so it will be locked up most of the way. However, I do have to make sure I get up to about 46 mph to engage it. Once it is engaged, there is a sizable drop in rpms from about 2000 down to 1600 at 45 mph.

So, we will see where this goes. :) As always, I'm open to suggestions.

Suggestion: sell inefficient, old school automatic. Buy manual.

Sorry... probably not what you meant. :D

Haha, it has come to mind... :) I don't know how much she wants to hold on to it. Its her car and she has always wanted a Pontiac.

Well, Pontiac Builds Excitement! (TM) I should know.

Trade ya?

While the torque converter does lock up for the majority of the trip (cruising), it does not lock up at all during acceleration.

I am looking into Orange4boy's thread on freezing the slushbox, aka locking the torque converter on demand. It seems like a relatively easy modification, and I already found the wiring schematics for the automatic transmission. I just have to do some testing to see how they work.

http://ecomodder.com/forum/attachmen...1&d=1397075509

I assume that's the "TCC solenoid"?

My girlfriend has the same engine/transmission in her 1999 Sunfire sedan. It's just awful with that 3 speed. I had to drive it to work for a week (500 miles) and the best I could do driving 60 MPH was 26 MPG. She is lucky to get 24 MPG doing mixed driving.

I'm not sure how effective aero mods will be in such a short and slower commute, but thats where I would start (unless I had the option to sell the car and buy another one!). You've already pumped up the tires. Maybe try some engine on P&G in neutral?

Yeah, the TCC solenoid is the one I need to figure out how to control.

Thanks for the heads up cbaber. I'm still hoping I can eek out low 30s out of it, but that isn't too encouraging... In any case, challenge accepted! :D

Put in a non electronic 4 speed auto trans from a v6, 4T60. It will cruse round 1800 rpm at 65 mph with the right ratios..while your at it get a low stall speed converter.

GM Transmission Info

http://www.gmforum.com/howto/transmi...60e/4T60-E.pdf

Or just but a manual trans car.