I put a CAI in a few days ago and have lost 1-2 miles per gallon since then. I have filed up twice and both are a netting me a loss. Anyone have any ideas why?

Here is the graph. The latest fill up does not show but is in the 23.1 range.

 

Throwing aside the inherent difficulty in stabilizing driving habits, anything that permits more air to the engine will allow the engine to burn more fuel, and consequently, lower your gas mileage (holding efficiency of the engine constant).

- Matt

 

Well usually CAI add power, which means the engine shouldnt have to work harder, so it hsould net you a small increase in MPG. More than likely your loss is due to the fact that you are giving it more gas to hear that supercharger scream or to hear is suck.

Jack

 

There's an easy answer as to why your power gain comes with a fuel economy loss; it's your right foot! Once you get used to your newfound fun you can then retrain yourself to get back in better efficiency habits and get your fuel economy stabilized again.

 

Foot of Density! I believe it is the culprit.

 

How do you think the engine is making more power? More air gets in + more fuel being burned = more power.

Foot could be irrelevant. Could be a contributing factor in this situation, but if that could be isolated, you'd still be getting less gas mileage.

- Matt

 

I was a lead foot before the CAI. I don't think I am working her any harder.

 

nothin quite like a nice colorful squiggly line graph

 

Wow, a graph of gas consumption.
Well, it only goes south from here.
add pulley=minus 1 gallon
add lighter wheels/tires=minus another gallon
add a header= 1 more
...raspy exhaust...head...valves,cam....infinitum
The faster you mod,the faster you go,the faster you visit the petrolmart.
I'm gettin' 20.somethin' mpg.......oh well!

 

www.mymilemarker.com via twitter.com

Works great, can even tell which vehicle your TXTing in on. Sweet if you ask me.

 

How do lighter wheels lower mileage? Anyway, I noticed the same sort of thing when I installed my intake. It has since come back up to normal levels.

The thing about the intake is that you aren't really adding more air unless you have your foot in it. The supercharger is in bypass when cruising so it should simply be bypassing what little more air there is. Now if you drive hard, there will be more air coming into the engine, meaning more fuel gets injected. After watching my boost gauge, boost seems to come on sooner with an intake than the stock system.

 

Doesn't engine management "adapt." Example, many cars monitor engine characteristics and if... lower octane gas is used, lowers performance.

Would the inverse hold true - better ignition, better movement through the powerband - more delivery of fuel?

 

Cooler air will result in lower fuel economy than warmer air. A lot of the "100mpg Carburetor" designs worked by superheating the intake air to maximize fuel atomization. Not good for power or long term engine durability (detonation) but it does work.
That being said, a cold air intake should only be a very small decrease in fuel economy. From what I can tell, with my CIA and 15% pulley install, I've only had a small decrease in fuel economy under most conditions.

 

JohnJohn,

If you are up for the experiment... Put the stock intake back in for a few tanks and see if the MPG comes back up ...

One other aspect here is the ECU is "learning" all the time about the right fuel trim use with feedback from the O2 sensors.. Because of that, you might want to reset the ECU (disconnecting the battery for more than 10 mins) when you change the intake. I think this helps minimize the effect of the ECU learning from the previous intake.. But I might not have this quite right...

Has the weather started to warm up? Warmer air is less dense and makes less power?
Are you still making the same boost pressure?
Are yor tires inflated correctly?

Just my thoghts,
BBCooper

 

Tires are good/consistent
I did reset the ECU via the battery and the odo reset system after the install
Not sure how to test the boost pressure(only have stock gauges)

Here is some more info. I bought the unit used. Originally came from Las Vegas. Lower altitude. I did have it in for service at the dealer once, but I can't verify if the dealer reset the ECU. That was back begining of Feb on the chart. Could it be that the ECU was used to more air(lower altitude), then when I reset it for the first time at 5280ft it is still getting use to that?

 

Hmm... I could go on with more questions to see if we can narrow dwon the variables... But given the magnitude of the change - 1-2 mpg - I am wondering if this is a "real" issue... Perhaps give your MINI a few more fill ups & data points and see where it goes.. Looking closer at your chart, what does a data point represent? a full tank fillup of 12 gallons? If so that looks like you fill up 13 times in 5 weeks.. That is some serious driving. Assuming about 250 miles per tank... that is 3250 miles!!! Wow that's Motoring

Looking at my MPG records - yes I track them too . They show on average a 1.0 MPG increase after my CAI was installed. This is comparing the average of 40 fill ups before and 40 fill ups after the install. So maybe more data, is all that is needed... For the record, 40 fill ups for me is about 15 months worth of driving...

Reading your post above. What are you referring to as the "unit" - the CAI or the MINI itself? If it is the CAI, that should not be an issue.. If "the unit" is the MINI, it could take the ECU some time to adjust. From your MPG recording, I would assume that your MINI has only been at the "high" altitude for just over a month?? so it still might be adapting..

I am still curious if your weather is warming up there yet? Something like a 10 - 15 degree change?? That might be enough the change the air density enough to notice in MPG calculations..

Lastly, how many miles on your MINI total?? Perhaps the CAI install just exposed a "weaker" element and it is now showing up in your MPG measurements? Maybe plugs, wires, coil are showing some age?? Hard to tell with out being there looking at your MINI.. So I may be off track here..

Maybe that helps,
BBCooper

 

With the mods in my signature last fill up I got 29 mpg...which is pretty normal. 60% freeway 40% city and spirited driving.

 

MCS has 30,000 miles on it. I bought it at 25,000 Feb 1st. I agree it's a lot of Motoring.

I was referring to the unit...as the Cooper, it being from Las Vegas. However it's been in the Denver area for about 8 months prior to my purchase. I'm not sure if the ECU was reset prior to the CAI install. I did it after.

With other CAIs I have installed on other vehicles I have seen and increase in mileage.

I wonder if it may be the design of this particular CAI. It uses the stock way of getting air into the box. Just basically mounts a larger cone style filter inside the bottom of the old box. Here is some pictures. This would mean the air its getting is the same temp, just more of it.

 

Raise your hand if you voted for lead foot.

I filled up today 26.11mpg. I think this tank better represented my driving style in the past.

Thanks.

 

Didn't notice in any of your posts if your CAI is just an add-on cone or a complete system that blocks the hot air from the engine compartment. Injesting hot underhood air will have a detrimental effect on your mileage.
-skip-

 

Skip, here is a link to the pics of my CAI. Should block all the hot air.

http://www.5280driver.com/2008/03/12...ntake-install/

 

the graph you posted the delta is small compared to the variance.

And there's more BS in this thread than in the dirt of a hog farm! Sorry, but that's just the facts....

Matt

 

Sorry Matt I've only had the Cooper since Feb 1st, so that's all the data there is.

What's BS and What's fact? Thanks.

 

the car runs via a system called "speed density". It measure the density of the air charge in the intake (pressure and temp) and looks at the speed of the engine to figure out how much fuel to squirt and what timing to use. (This is the basic description....). If you add an air intake that allows more air into the system, you will only use more fuel when you're asking for more power. Otherwise the throttle body will just open a bit less, and the air density in the intake will be the same, the fuel injected will be the same, the timing will be the same, and the power generated and the gas mileage will be the same. While the CAI has the potential to let more air in, actual gas consumption will only really change when you ask for the system to deliver more than you had asked for it to do before the intake mod. Really, the posts that say this is from increase pedal effort, or just measurement noise, are more on the money. Just keep plotting data, and the person who had the dip and return to the same mileage probably is forshadowing what you will experience.

The information on adaption is somewhat suspect as well. Long term trims don't take that many miles to set, short term trims are nearly instant, and the only other values are initialization values that require some SW tools to tell the car to relearn the numbers.

But despite the presence of information describing what the car really does, there is TONS of information that perpetuates about what people think it does. Such is the nature of internet forums.

Matt

 

ahh

Is this theory true then?

If I place a 1/4 gallon of gas in the tank, start the car and let it idle. Then start a stopwatch. It should take the same amount of time to run out of gas no matter what kind of intake is on the car(stock of CAI)?

While driving with a CAI installed does the TB plate open less...relative to the TB with a stock airbox?