relate to HP increase?

My around town mileage went from a steady 26, (using OBC), to a steady 28, after installing MyMini touring exhaust and ITG foam filter. This is a 7.7% increase in mileage under the same driving conditions, same gas, etc, and over enough miles, (600), to make the average an accurate representation of mileage after the changes.

I calculated a HP increase based on the mileage increase but I don't think it's right, (too much of an increase). Since the amount of HP required to move my MINI stayed the same, I assume the increase in mileage is due to a power increase, which results in a slighty lower throttle position for a given speed.

The big plus is that the car does feel like it has more power and it's much smoother when accelerating just off idle, not even a slight shake or stumble.

If you're still running your stock exhaust, do your MINI a favor and get an aftermarket system. You'll be glad you did.

 

I have a MyMini sport exhaust w/resonator and the MyMini cold air intake and I've found the same thing more power better gas mileage. Just like the human body the better that you take in and exhale (intake-exhaust) oxygen the easy er it is to perform a given task. Talk about having your cake and eating it to.As far as how it MPG % relates to HP increase I have no idea. But great questions. Maybe some of tec. experts can jump on this one.

 

I did a Typhoon intake first, then a Magnaflow cat-back months later. I saw a slight increase in mileage, smoother throttle response and more zip above 4500 rpms with the intake. I saw no increase in mileage with the exhaust but a noticable increase in power, even at lower rpms. There may actually be an increase in mpg from the exhaust mod, cancelled out by the harder driving to more completely enjoy the power and sound.

The stock exhaust seems to breathe pretty well, and I'd assume the cat-converter is the bottleneck in the system, so it doesn't suprise me that anything from the cat back would not significantly improve air flow. Just a subjective opinion - I don't got no fancy technology facts to back it up!

 

I have a Milltek exhaust and a K&N intake. But my mileage actually decreased. But than, I live at 5,000 rpm . I just love that banshee like howl.

 

at least not directly. You've gotten an increase in efficiency, which in theory can relate to an increase in total available power. But the driving you're probably doing isn't at red-line, and if you're seeing MPG increases, then you're not doing what most of us do, which hammer the throttle to feel the increase in power!

So if you really want to know the power delta, you need to measure it directly...

But for a very rough, probably not too usefull estimate, take your old MPG and the new MPG and that percentage of increase can be thought of as your efficiency increase (for this to work, driving style etc would have to be exactly the same). Then take the old HP, and see the percentage increase in HP that MIGHT be there. I think this won't work worth beans, but it is an answer to your question.

There are lots of reasons this estimation technique will have problems.
System ressonance. Some things like exhausts and intakes have RPM ranges where they're better and worse.
Timing retard. If the motor detects the onset of knock, it pulls back the timing. Look at a bunch of dyno charts that have been posted. That kink up around 6000 RPMs is the timing retard kicking in. It's worst at peak HP.
Changes in driving style. With better performance, you're not putting your foot in it as much. Hence the better MPG. IF you do put your foot in it as much, you might have had better performance at same or worse MPG.

Matt

 

Yep, that's what I did that I said seemed like too much, a little over 8 HP. I can see that it might not be accurate for various reasons, but it seemed logical.

As for driving style, same as before the changes, except a few more speedy takeoffs to hear the exhaust, so if anything the driving style variable would have caused a drop in mileage.

However, an 8 HP increase from a new exhaust and drop-in filter, at least in peak horsepower, seems unlikely.

MINI runs much smoother though, and power has increased some.

 

8 HP seems LOW! Anyway, you've got a few more ponies on tap, and a different sound, so live and enjoy!

Matt

 

I've already dropped in an ITG foam filter, and the Milltek exhaust came today so it'll go on this weekend. I'll see if my overall mileage increases. I'm at 27.0 since new (about 2800 miles), generally all around-town commuting and errand running.

I'm not expecting much more in horsepower, what I'm expecting is better throttle response, better exhaust note, stronger pull at slightly lower revs. More MPG would be a plus.

I'm not driven to get a specialized air intake, although the ITG one looks nice.

 

I have an '06 Cooper with My mini touring exhaust and ItG filter. Not "hammering" it but not babying it either, with a lot of stop/go jammed fwy. commute mixed with short trips around town, and 70 to 80 mph fwy - after about 6 tanks of gas measured mpg (not by computer) my mileage is a steady 29 to 31.5 mpg. Feels stronger than before, but nothing earthshaking.

 

If you have the OBC, what does it say your mileage is? I've never checked my mileage manually. I figure the OBC, while it might not be spot-on, is at least as consistent as I would be with a manual calculation, and trying to be sure I don't overflow my gas tank while trying to, "top it off".

 

Don't have OBC - from what I've read on these forums, when people check their mileage manually the computer is a bit optimistic - they're actually getting one or two mpg less than indicated.

 

so far just using the real time computer readout my mileage has dropped with an ITG dropin filter and the Milltek exhaust, but I imagine it's because I can't keep my foot out of it because of all the nice noise. I've also seen the overall (since new) mileage drop from 27.0 to 26.7 in about a half-a-tankfull's driving. This is not good. When I fill it I'll try to keep my foot out of it and see what I get after about a half-tank of 'normal' driving. I tell you though, the stock header is ridiculously restrictive.

Has anyone replaced a header and been yelled at by the dealer when in for service ? I know cat-back is ok, I'm sure I'd be pushing it changing out the header, but that stock one needs to go.