I've noticed a decrease in mileage by about 20-25% after I installed a HAI and a 17% supercharger.

Those are the only mods I have and I don't know if this is normal or not?

Any input?

Thanks.

 

More often than not, this is a symptom of "HRF"...Heavy Right Foot. You might consider lifting the right foot off the 'go pedal' or alternatively (not proven in a lab) a lighter shoe and sock. Good luck!

 

Given the same throttle position, RPM, and load on car (slope of road), a car with more boost (such as your 17% pulley does) is going to use more gas. Here's the reason. You're making more boost! When you make more boost the ECU will increase the amount of fuel going to the engine in an attempt to keep the A/F ratios correct.

However, some will argue the point that with more power you won't have to press on the gas pedal as hard, and therefore you can get better fuel economy. There's a few people out there that have experience this.

For me. When I get more mods, I get more aggressive with my driving style, and I am in the same boat as you are. Getting worse gas mileage.

Want to save more gas? Get a boost gauge, and attempt to never let the engine see boost. It's a tricky thing to do. Give it a try.

 

I agree thta it's probably the HRF problem. Of course, the trade off is good or bad depending on what your mileage was before the mods. I never knew (I started modding with 12 miles on the car...) so never had to worry about the comparison. Actually though, my mileage is proportional to how many WOT runs I do, so I *can* control it--so can you! But what's the fun in that, eh?
Gas is still cheap in the US.

 

thanks for the replies,

I'll try a tank of gas going easy and see how much difference that makes.

 

I agree with the HRF in most cases. I'd still look to see if there is anyting else that may be the culprit.
I'm at aboout 40HP more than stock and my average MPG is about 1 1/2 MPG less than it was 4 years ago.

 

right -on . i'm better than previous. i'd suggest a header and exhaust to get the free horsepower your car already makes.; then watch the mileage climb back up .

 

im not quite sure if this is the problem, but when i had a HAI in my other car i notice a significant increase in MPG, but when i switched to a CAI i saw an increase.

 

Increase and increase?

please clarify,

Thanks

 

got me there man.

 

I noticed a decrease in mileage too, after adding the pulley. I had my Unichip remapped and put it into the S. Since then, I consistently get around 30 mpg...even when fooling around.

 

Gas mileage was one of my criteria about mods, so right after having my performance mods done (at about 4k miles, 15%, CAI, cat-back exhaust, cold plugs) I started checking the gas. In before and immediately after tests -- before I re-learned how to drive -- when keeping it under 70mph on the freeway, I improved my gas mileage by 3 to 5 mpg. Now that's a small margin, so some of it could also be wind, road or other differences. But there was a general, but small increase in mpg for me.

That said, I tend to ask more from the car now that it has more hp. Screeching the tires in 1st, 2nd and sometimes even 3rd is far too easy and far too much fun to resist. Feathering the throttle at a stop, doing WOT runs, seeing >100mph or taking it up to redline is something I NEVER did before I had mods, nor did I dream I ever would. The world changes with a relatively small amount of added hp, and as a result, so does gas mileage.

The problem with having more is using it.



Best,

-- Don

 

haha sorry i meant a decrease when i had my HAI and an increase with my CAI

 

And -where- can you do this, Don? I've never gone 100mph or higher in my MINI. The race track here is too short and I can only get to about 80mph. The same is true on the dragstrip. I often wonder how I'm ever going to experience triple-digit speeds in my car?

Also, I've never been able to chirp the tires in my car--and I'm pretty sure it has more HP than about 99% of all MINIs ever made...
cheers,

 

Hi Phil,

Hmmm, well, I could tell you where, but that would be publicly admitting that there is such a place and that I've been there at >100mph, at least a half dozen times, and that in certain times the average speed for traffic there is between 95mph and 110mph...

If there was such a place, I'd venture a guess that it was on a major north-south inland highway near one of the southern-most major cities of Southern California.

And, btw, I'd also venture a guess that my MCS could do that >100mph with a full load of 4 adults plus a full boot, going mildly uphill. I'm guessing that yours could too.

Hmmm, chirping tires has been a way of life since my mods were installed. After he modded and test drove my MCS, Steve of Steve's Auto Clinic (North Hills, California) told me he didn't know how I'd keep from chirping all the time while shifting into 2nd...

He was right, I had to re-learn how to drive to prevent it. Of course chirping in 1st is even harder to avoid, especially when starting from a dead stop and worse, when driving over painted traffic or crosswalk lines. And yes, I have even accidentally chirped while shifting into 3rd a couple of times.

Btw, I'm using the standard all weather run-flats and S-Lites... And tire tread is very good.

I do try not to chirp, in fact I try to avoid most obnoxious noises with my MCS. But it is difficult to avoid chirping much of the time.

Best,

-- Don

 

So, now I have to go west, young man...
I think my tires might be working against chirps--they are pretty grippy.
Maybe I'll see you out there!
cheers, phil