View Full Version : MPG seems to average pretty ok for what we have.

11-28-2010, 08:32 AM
Right now i am running a st85 with a 165tranny. it seems i am going about 60mph at almost 3k rpm. i want to know, if anyone happens to know what is 65mph @ what rpm's for a st205 tranny. i was told that the 205 tranny is best overall. Strong, better gear ratios, better shifting, and you can max out higher speeds out of it. So i want to know what rpm i will b at going 65-70 on the 205 tranny.
Also is it really just straight bolt on to this motor? No fabs at all?

11-29-2010, 12:57 AM
I don't know about RPM at speed for the 205 but it's a bolt in. You have to reuse the speedo gear drive from your old transmission but other than that you're good to go. You're right about it being a better tranny. It's got the better syncros. I'd like to get one for my 185.

11-29-2010, 06:46 PM
if you're running origional tire size, (205/60/14) with the 165 tranny then at 65MPH your engine should be approx 2900RPM
With the same setup with the ST185 tranny, your engine speed will be the same in 3rd 4th 5th and the final drive are the same
With the ST185RC tranny, 2700
with the ST205 tranny, 2900 as the final drive and 5th are the same as the ST165. the reason the 205 has a taller top end is because the tire diameter is larger than the 165 (23.69" vs 24.46)

The ST205 tranny will bolt right up, but if you're looking for a taller 5th, your only option is the ST185RC tranny

Here are all the gear ratios for the GT4 boxes.

11-30-2010, 04:11 PM
I hadnt really tried to get good mpg yet till first road trip last weekend. Hypermiling with my 94 Celica GT, even in town i can get near 400 mi on a tank. Compared to that my all trac seemed HORRIBLE. Ofcourse I love the boost so much is why. But on the trip I layed off the boost. And she got over 300 mi on a tank I was really happy.

12-01-2010, 04:45 AM
i havent looked into it but are there taller/bigger gears we can put in the 185 tranny? i want it geared for top speed, because i do alot of freeway driving, and having my rpms lower than ~3k would be nice...
and from what im seeing, a bigger diameter on the rim and tire drops your rpms a bit? i see how that could make sense.

12-02-2010, 07:12 PM
The Lower the rpm's at high speed, the higher engine load and less mpg's. Our engines aren't torque monsters so they need that higher cruising rpm. My 08 sequoia at 70mph is like around 1900rpm but it is a 5.8L torque monster and with a 6speed tranny it averages 21mpg on long trips but like 13-14 around town :(

12-03-2010, 12:51 AM
The Lower the rpm's at high speed, the higher engine load and less mpg's. Our engines aren't torque monsters so they need that higher cruising rpm.

I don't follow this line of reasoning at all. Not to mention the 3sgte IS a relatively balanced engine in terms of torque to HP ratio (not that I think that has anything to do with it). The gearing of the transmission is what primarily determines what RPM you are at with any given speed, not how much torque the engine produces (at normal freeway speeds, I'm of course assuming any car and transmission we are talking about are not trying to go 200+). A taller cruising gear (to cruise at lower RPM) should certainly improve high speed cruising MPG, although as has been mentioned, the cheapest way to get more fuel economy out of a 3sgte is to not boost much.