Prior to installing my GSC s2 cams and injectors back in the end of September, I was averaging around 23 MPG, and since, I have been averaging between 16 and 17 mpg. The Evo is my daily driver, and it is really frustrating. My tuner originally said there is something off about the tune, and to bring it back in. But when I brought it in, he said that's about what the Evo should be getting for driving around town, but my driving habits have not changed. Didn't make much sense to me.

Has anyone else noticed a significant change in gas mileage after installing cams? The reason I believe it is the cams is because on start up it is a pretty rough idle (as expected) but if I release the clutch too fast (even in neutral) the car will stall due to the slight pressure from the flywheel. And with the clutch pedal out, the vacuum will sit right around 10 pounds, where before the install, vacuum was always at 20. I'm guessing the car is dumping more fuel to keep the car running with the roughness of the cams? This is all speculation, and I'm not too sure or knowledgeable on the subject. Any help would be greatly appreciated.

 

Any input?

 

I believe it's the injectors not the cams. IT doesn't sound like they are setup right. I installed mine with the stock turbo and didn't have a change in mpg.

 

My idle is very rough on cold starts. I usually get 20-23 mpg mixed driving. I think its ur injectors. On a road trip i was able to get 26 mpg, but my turbo is huge. In town I get like 15mpg with all the traffic light idling.

 

Sounds normal to me. I get about 12-13mpg but thats on e85 with HKS 272s. Before E85 I was getting about 17mpg on 93 pump gas with HKS272. GSC S2 Im assuming will get worse mpg but I still need to install mine to find out. The more power you make the more fuel you will use. Want to play you have to pay.

 

It is not the cams, I would have to go out on a limb here and say it is the tune. I didn't see any decrease when I went to Kelford 272s and 1200cc injectors. Your car shouldn't stall either.

 

I blame it on the tune and/or injectors.
Which ones are in your car?

My fuel mileage actually increased with S1's, FIC 850's, and a tune.

 

I also do believe it is tune/fuel injectors too. What Clutch/flywheel are you running? Stall out seems weird if you are not running really light flywheel.

 

Tune all day. My friend got his evo tune and gets better miles now.

 

What size injectors?
If they're way too big then needed you're just dumping fuel like crazy and do you have any other mods?
Shouldn't really need Injectors if you have just cams.

 

should get better gas mileage after the tune theoretically speaking

 

Oh, 17-21 InHg is what most vehicles ideally run.
Do you have an A/F gauge as well?

 

Yeah I agree it def sounds like the tune. The injector scales may be off.

Vacuum will decrease a bit with aftermarket cams but not that much. With cams, after my idle settles vac is around 17-18 InHg. Mixed driving I avg about 21-22mpg.

Do you have a log to post?

 

Sounds like you may need to check your tune or for vac leaks. I am running S1's and get around 21 city and around 24 highway when i drive easy. Before my retune my MPG sucked and i was lucky to get 20 with mixed driving.

 

^ +1 boost leak. You run richer when you have boost leaks.