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junah123

Induction Kit - Why Is It Affecting My Mpg

12 posts in this topic

Morning all,

First post here so I'll keep it short.

Basically, I recently bought and fitted a J! automotive induction kit (Link: http://www.j1automotive.co.uk/ourshop/prod_1828433-Fiesta-Mk7-Air-Intake-Kit-16-Litre-202014105.html)

I was advised that this would increase BHP slightly and make the engine sound a bit sportier (Both of which it has done) however, it has decreased the range of my fuel tank by about 50 miles!

I have been driving as careful as possible and was advised my friend (who is a car fanatic) that no air filter should reduce the MPG of the car (Other than the first time you use it when you tend to rev it more so you can hear the effects)

Has anyone else had similar issues? and is there anything I can do short of putting the old one back in?!

Cheers

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If it increases power by adding more air/cleaner air, then surely it would use more fuel in proportion?

But then again I don't even fully understand the mechanics behind internal combustion engines..... :huh::wacko::unsure::blink:

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The problem with induction kits like this is that they bypass the air filter box and therefore the ducts from the front bumper.

This often means that hot air is being sucked in from under the bonnet rather than fresh air through the ducts as before.

Hot air cannot be used as efficiently as nice dense cold air, so this is probably why your MPG has decreased.

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The reason I bought this specific kit was that it has a box that has been created to slot straight in place of the old one without having to bodge anything. The old duct was removed leaving a gap that causes air to flow straight through the grill and in to the new box, so hot air shouldn't be a problem. It's also got a pretty decent heat shield so it remains pretty cold at all times.

Any other ideas? or ideas how I could increase it? (Other than driving economically which I do anyway...most of the time ;) )

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Take the grill off and you'll see the problem with the theory of it taking air up through the grill, big slam panel blocks off half of the grill, so it'll be pulling warm air from the engine in. I'm really against these systems personally, you need your car mapped for the extra air they bring in anyway, they pull in warmer air than the stock box, and the stock boxes are good anyway. The only times I've seen them be better is where the air filter is sat on top of the engine without a feed leading to the outside of the vehicle, for example my Mini has an air filter right on top of the engine, with the intake just in front of the engine, but at the back of the engine bay, so here it was already pulling in hot air.

You'll need to put a cold air feed in, and then you're as restricted in flow as you were with the stock box probably, and you'll soak up some puddles if it's too low.

I always say stick to a panel replacement.

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Just stick the old intake back on if you want your MPG back

because -

1 - the original induction system is very carefully designed to not loose power (it has an efficient cool air intake) and work in sub-zero tempratures to deserts, with long service intervals - it is very difficult to improve on it, exept if you just want to make more noise

2 - the "aftrmarket" system may actually REDUCE power, the extra noise can give an illusion of extra power (placibo effect) the stock system may be designed to boost low end power/ torque, removing this can sometimes make the car feel quicker (eg - hitting the "power band"/ less bottom end making the mid/ top end feel quicker - when it isn't )

3 even if the replacement intake increases power on a cool day, as the car is warming up, it may reduce power on a hot day/ once the car has warmed up - the intake/ air box has to be completely enclosed/ sealed from the hot underbonnet air, heat shields etc are no use. on a hot day you may even get pinking/ detonation

4 when they "test" the aftermarket air filter on a dyno, often, there are loads of big fans, and/or refrigerated/ cooled unit and the bonnet is open so the "power gain" is under those conditions, not "real life" conditions, or its tested with a vented bonnet or bonnet lifters (spacers that fit on the back hinges of bonnets that lift the back forming a vent on things like Cosworths to keep underbonnet temps down)

5 the intake may be a mismatch to a stock engine, if the air (going into the engine) is actually increased, the ECU will increase the fuelling (because the air/ fuel mixture has to be correct for the CAT/ emmisions etc) this extra fuel/ air if it does not put to any usefol work / or is restricted by (eg) the exhaust, may just be wasted (so extra fuel may be injected with no benifit - thus lower efficiency/ MPG) (drawing warmer air/ loss of bottom end power can loose MPG too),as BD has said, a remap or other phisical mods (the engine set up for the mods) my be nessesary an NA engine may need to be revved higher and have extensive modifications (usually expensive) to get significant gains

6

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Basic principle is more air needs more fuel to balance up or you'll end up with a imbalance.

For the same reason you tend to get lower fuel economy in cold weather- cold air is denser so therefore to maintain the correct mix more fuel is needed.

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Basic principle is more air needs more fuel to balance up or you'll end up with a imbalance.

For the same reason you tend to get lower fuel economy in cold weather- cold air is denser so therefore to maintain the correct mix more fuel is needed.

That's basically what I thought would happen, and that's with my very basic knowledge of how an engine works :unsure::oops::iim:

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Foca

Interesting and informative response. I have fitted a K&N panel filter and Mountune inlet hose don't seem to have lost out on MPG still getting 37 so is it just these full replacements that cause the problems?

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Foca

Interesting and informative response. I have fitted a K&N panel filter and Mountune inlet hose don't seem to have lost out on MPG still getting 37 so is it just these full replacements that cause the problems?

You are still using the old box, the panel and inlet just decreases air resistance, but the car is still able to pull air in as it was designed.

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Thanks for the responses guys. As I drive 35,000miles a year I'm starting to reconsider this...

Things were a bit better yesterday, I drove to Nottingham and back (300miles) and my tank usually gives me around 300-320 miles to a tank with the way I drive (Mostly motorway and A road driving) and yesterday it read as high as 380miles to a tank (MPG reading never seems to change though?)

Also, someone mentioned to me that when the car goes in for an MOT I'll have to put the old one back in or else it will fail, is this true?

Cheers

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Thanks for the responses guys. As I drive 35,000miles a year I'm starting to reconsider this...

Things were a bit better yesterday, I drove to Nottingham and back (300miles) and my tank usually gives me around 300-320 miles to a tank with the way I drive (Mostly motorway and A road driving) and yesterday it read as high as 380miles to a tank (MPG reading never seems to change though?)

Also, someone mentioned to me that when the car goes in for an MOT I'll have to put the old one back in or else it will fail, is this true?

Cheers

No, not unless its knocking the fuel/ air mixture out, it has to be stoichometric or it may effect the emmissions or contaminate the catalytic convertor which may cause a fail over time, the MAF sensor should measure the air flow and the ECU adjust the air-fuel mixture untill its stochometric, without (eg, as the air filter gets dirtier/ more restricted over time, it flows less air, this would make the engine run richer but the MAF measures this and reduces the (petrol) fuel untill the fuel/ air ratio is correct (stochometric) )

Theoretically the intake could be modified so much that its flowing so much air that the injectors cannot supply enough petrol and the engine runs lean, (this would mean the AF is not correct/ stochometric so it may burn out the cat/ fail emmisions because its too lean or the ECU detects this and trigger limp home mode )

Its also theoretically possible that the MAF could flow so much air untill it was out of range (over the maximum it was designed for/ or the signal is outside tht which the ECU could measure ) all very unlikely on an engine like this - but this can happen on highly modified cars

or the induction roar really loud and you have a "jobsworth" tester who fails it on exessive noise

They do run these things for a while during an MOT and they have to run them at a certain temp, so if the intake is drawing warm air it could possibly effet emmisions - butb again "burderline" - highly unlikely

So in a nutshell the ECU should adapt to any changes in airflow untill the AFratio is correct and it should not fail on that without resetting the ECU on a modern Ford in my opinion

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