GTM Performance Engineering: MHI Twin Turbo Official Release

Originally Posted by Wattles

The car is running strong at 550+ WHP.

I got the car back and have been driving around with tons of power. Did my first oil change at 1k miles. The engine is strong. I can burn the tires at 60 on the freeway.

The stage four transmission shifts like a dream. Hard shifts at full throttle and softer with regular driving. I feel like it can handle the power that the engine puts out now. The stock Trans with valve body upgrade always felt like it was slipping in higher gears (3rd - 5th). I was afraid the stage four would hit like-a-truck in 1st to second transition, but it really is firm, but smooth.

The engine rebuild (stage 1 GTM long block) seems to have added roughly 100whp and runs super-strong. The drivability is really nice.

I am really hopeful that I am going to get 10s of thousands of trouble free miles out of the new setup.

One or two minor issues (which I think are bein worked out in the production setup).
1) the driver's side air return (from the Tial blow off valves) is rubbing slightly on the wheel well at full throttle (max power). This is annoying, but seems to be fairly cosmetic/annoying. I think the only fix for this is a redesign/shortening of the pipe.
2) I have developed a whistle/whine at boost. This sounds like a full ballon being pulled tight while letting air out (the sound your kids love to make with a ballon as they let air out). I'm not noticing loss of boost, but I fear a fitting or line to/from the boost controller has a leak.
I'll have to do a line pressure check.

All in all I am prety happy with the power (having upgraded to the Garett turbos) and (unfortunately) having to build the engine.

Takeaways:
When all is said and done,
- the engine is super powerful.
- The craftsmanship is amazing,
- the drivability is superb,
- the car is a blast to drive,
- the project always seems "almost complete" (If I can solve the rubbing and whistle it will be show ready - it's hard to take someone for a ride and have to explain noises )
- expect MANY delays and at least double your original budget
- your car will forever be a project car (have a backup)
- the stage 4 transmission is quite good
- wives have about 1/4 the patience you have