Sniper308

Still kicking around whether to go with one from Supernatural Performance.

Russ

Five Oh Brian

Around 2,000 to 2,200 rpm's - roughly the same as the 05-08 GT's. I went to a bigger stall converter (rated at 3,800 rpm's, but now flashing to 4,300 rpm's due to some mods) and I am so happy with the increased performance - at the track and as a daily driver!

Sniper308

Other than when your foot is mashing the pedal... any decrease in mileage?

Russ

Five Oh Brian

Hey, Russ, my car is EPA rated to get 15 mpg city and 22 mpg highway. If I drive responsibly and keep from flashing the converter I can easily get about 15-16 mpg around town (although I'm a lead foot, love the converter, and get about 13 mpg having run).

On the highway, I get about 27 mpg on long cruises with no elevation changes. On highways with lots of rolling hills, it drops to about 24 mpg (stall speed rises going uphills when there's a load on the engine). Either way, I'm getting better highway mileage than the EPA rated my car for and it performs much better than stock!

Key to getting good fuel economy with an aftermarket stall converter is buying one that features a lock-up in 4th and 5th gear (just like the factory unit). Without a lock-up feature, you'll save money upfront when buying the converter, but it will always run loose which causes wasted fuel and excess heat in the transmission. I made sure the converter I bought had a lock-up feature before buying it. In fact, it offers twice the clutch surface area versus a stock converter and the manufacturer (Fuddle Racing, in my case) claims it can actually hold the lock-up even at wide open throttle (a stock converter can't do that). So, way better performance and marginally better fuel economy. Win-win!!!

Sniper308

I got the 2800-3000 one from Supernatural Racing. Didn't know to ask about this "lock" feature, mind probably doesn't have it. Nuts. What happens in fourth and fifth gears without the lock?

Russ

Five Oh Brian

Without the lock-up feature, the converter will always be "loose" and thus the engine will rev higher than necessary (hurting fuel economy and generating excess heat in the transmission). It's like slipping a clutch in a stick-shift car.

I checked Supernatural Performance's website, and they mention that their converters (including the 2800-300 rpm) feature a carbon fiber clutch lining, so it sounds like they are lock-up style converters (the clutch is what engages lock-up mode).

Sniper308

Wow, thanks for that information. I feel better now.

Russ