I know that when you supercharge a car it will cost you some mpg. And I am not exactly concerned with mpg, but I am only getting about 10.5 mpg in town, so I am wondering what kind of mpg some of you other guys are getting? And no I do not drag race from each stop sign or anything like that. I only drive about 25-30mph usually. Oh and the car has the stock 3:55 gears. I am asking because the car has a cold run issue as it is, that I think might be in the tune, but with my mpg only being 10.5 when I was told that they should be around 15 makes me wonder if something else might be wrong. Any inputs would be helpful...

 

i have the stage 3 kit. i average 14 t0 17in the cityand i still get on it as much as i want. there has to be something wrong call brenspeed and talk with them. what kind of hp where you making when they dynod?

 

10.5 is way too low.

 

Well Graygt07, the problem is I have emailed Brenspeed and have not gotten a response back. And my car has been having a cold start/run issue that they cannot figure out. If I try to start the car and just throw it in first and drive away, the car sputters and spits and holds back for a second and then it will go. Mind you this is with me going like 10-20 mph and not punching it. I am thinking that the two may be related. And as far as HP numbers, that is another problem all together. There is no dyno within 4 hours of me so I have no idea and can't find out until July. So as this exact second I am not very happy with the kit. Hopefully if I get all the kinks worked out it will be fine, but right now I am a tad bit angry.

 

Was the kit installed properly?

 

Crazystylin, as far as I can tell the kit was installed right. Ihad a shop install it for me.Once I started having the issue I went over the install with a fine tooth comb and except for finding a couple of screws that were not torqued to the exact spec I do not see anything wrong with the install.

 

Sounds to me like you have a serious vacuum leak lurking under the hood, or your tune is excessively rich, which I doubt because Brent's tunes are usually spot on.

 

Well, when I start the car and idle is up for about 30 seconds the vacuum reads about 15 degrees. But as soon as the idle comes down my vacuum is sitting at 20 degrees. Which as far as I know is pretty good. I was thinking maybe my intake had a leak but since my vacuum is sitting at 20 hot or cold I would have to say that is out. But then again maybe my vacuum is supposed to be at like 25 and I do have a major leak... According to Brent and Dave 20 degrees is about right though.

 

There was a thread a few weeks ago discussing the 'cold stumble' issue. Seems like a number of us have this first thing in the morning on a cold day. You might want to do a search for it.

Regardless, 10.5 city is just wrong. I've got the Stage III set up with 4.10s, drive through the city to work everyday, and average about 13.5. 22 on the hwy.

The tune should be fine so now it's time to go look for other things. Yeah, it could be a vacuum leak but it could also be an ignition problem (bad plug, gap not set right, intermittent COP, ...). How does the car run otherwise?

 

2007GT/CS, the problem with the "cold stumble" is that it happens even when it is 85 degrees outside. So mine is when the car is cold period. It is not affected by outside temperature except that it lasts longer when it is cold outside. As far as the coils go I have MSD coils on the car already. I have had them on since about 2 weeksbefore I got the kit installed and it ran fine. And as far as the plugs I tried putting in the stock plugs (I know wrong heat range) but I wanted to see if it affected my stumble. And it did the same thing. I have Autolite HT0s, so if the gap is wrong Autolite did it, although I guess anything is possible. The car seems to run fine, minus the way it acts when I first start it. I had a belt issue a few weeks back (squealing like I had gotten something on it), but I changed the belt and that issue has not come back. About the only thing I have really noticed is that if I am driving in say 1st gear and I am sitting at about 1800-2200, if I stomp it, it is like there isminimal power the boost comes up but it takes a minute for the car to go and when it does go it doesn't even spin the tires, and I have stock rubber. I would have thought that with all that power I should rip the tires off.