Ford Fiesta ST
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#18228 - 26/08/05 06:20 PM Modification vs MPG?
Mase Offline
Fiesta Mad

Registered: 15/08/05
Posts: 384
Loc: Leeds
Maybe people who have modified the intake or exhaust on their s could help me here!

(science bit )
If you improve the intake and exhaust the engine finds it easier to bring in fresh air and push out the exhaust, leaving more power available, therefore increasing the bhp. This (I think) is achieved through burning no more fuel? But I have always been under the impression that increasing horsepower would lead to a decrease in mpg.
So what difference does improving the exhaust and intake have on your fuel consumption?

(and if my science bit is wrong can anybody correct me!)

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#18229 - 26/08/05 10:24 PM Re: Modification vs MPG? [Re: Mase]
Nick02 Offline


Registered: 19/02/05
Posts: 2608
Loc: Switzerland
Not sure about the exhaust side effects on consumption but on the intake side it will increase fuel consumtion as if it gets more air it will automatically be fed more fuel so as to maintain the optimum fuel/air mixture. Hence also the performance gains.

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#18230 - 26/08/05 11:35 PM Re: Modification vs MPG? [Re: Nick02]
PinkRinse Offline
Fiesta Maniac

Registered: 02/01/05
Posts: 6067
Loc: Shoreham-by-Sea, W. Sussex, UK
So getting something like an induction kit will increase the fuel comsumption?
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#18231 - 27/08/05 12:19 AM Re: Modification vs MPG? [Re: Nick02]
Mase Offline
Fiesta Mad

Registered: 15/08/05
Posts: 384
Loc: Leeds
Quote:

...on the intake side it will increase fuel consumtion as if it gets more air it will automatically be fed more fuel so as to maintain the optimum fuel/air mixture




But the way I was thinking it worked was that a new intake would just be less restrictive, so the engine wouldn't lose as much power having to suck the air in, not that anymore air is actually getting to the cylinder.

I would have agreed with you that increases in bhp would need more fuel, now a mate of mine has tried to explain as above and I'm just in two minds and confused!

Any automotive engineers around?!

Or anyone with any mods got some consumption figures?

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#18232 - 27/08/05 08:07 AM Re: Modification vs MPG? [Re: Mase]
Parksey Offline
Fiesta Nutter

Registered: 23/02/05
Posts: 1061
Loc: Winchester
I'd second how Nick has put it, an induction kit will allow more/denser air into the engine, the ECU will then add more fuel so the mix is right and that's where your (albeit small) power gain will come from. So yes, if you fit an induction kit then you will see an increase in fuel consumption. An exhaust shouldn't have any immediate effect on fuel consumption though.
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#18233 - 27/08/05 08:51 AM Re: Modification vs MPG? [Re: Parksey]
PeterDGM Offline
Fiesta Mad

Registered: 19/03/05
Posts: 293
Loc: Pau,Girona Spain.
But more BHP less need to floor it all the time,you may work lower down the rev range and actually save some fuel?
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#18234 - 27/08/05 10:04 AM Re: Modification vs MPG? [Re: PeterDGM]
Parksey Offline
Fiesta Nutter

Registered: 23/02/05
Posts: 1061
Loc: Winchester
Fair comment Peter, but then I think with more bhp, coupled with the noise of a replacement induction kit and exhaust, I'd be inclined to drive the car harder, more of the time, thus using even more fuel!
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#18235 - 27/08/05 01:48 PM Re: Modification vs MPG? [Re: Parksey]
PeterDGM Offline
Fiesta Mad

Registered: 19/03/05
Posts: 293
Loc: Pau,Girona Spain.
Parksey i,m 100%behind you on that mate,give me more BHP and I,ll use every last hair on that horse.I try after every fill up I say to myself at little less Fitipaldi and a little more Mr Molehusband (remember him?).No chance theres a vortex under the accelerator peddle that just sucks my foot to the floor.
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#18236 - 27/08/05 03:05 PM Re: Modification vs MPG? [Re: PeterDGM]
Chris Offline
Fiesta Nutter

Registered: 21/03/05
Posts: 3092
Loc: Isle of Wight
Yeah i'd love to hear of anyone who has done the modifications and what kind of mpg they are getting now?
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#18237 - 27/08/05 05:15 PM Re: Modification vs MPG? [Re: Chris]
Parksey Offline
Fiesta Nutter

Registered: 23/02/05
Posts: 1061
Loc: Winchester
Reginald Molehusband... Wasn't he from some sort of TV ad. Can't remember what for though.
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#18238 - 27/08/05 05:19 PM Re: Modification vs MPG? [Re: Parksey]
ChrisCumbria Offline

Driving as Daily

Registered: 26/06/05
Posts: 23772
Loc: Whitehaven, Cumbria
Reginald Molehusband was from a public information film about parking. Theres an (audio-only I'm afraid) link here.

http://tv.cream.org/specialassignments/themes/ads/regmole.mp3
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#18239 - 27/08/05 05:38 PM Re: Modification vs MPG? [Re: ChrisCumbria]
Parksey Offline
Fiesta Nutter

Registered: 23/02/05
Posts: 1061
Loc: Winchester
The name's familiar but I don't really remember it. Think it must have been a little before my time! (sorry Peter...)
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#18240 - 27/08/05 05:41 PM Re: Modification vs MPG? [Re: Parksey]
ChrisCumbria Offline

Driving as Daily

Registered: 26/06/05
Posts: 23772
Loc: Whitehaven, Cumbria
I had heard the name before but coudn't remember much about it. It must be before my time as well, as according to the site where I found that clip Reg was driving an Austin 1100 in that film!
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#18241 - 27/08/05 08:30 PM Re: Modification vs MPG? [Re: Parksey]
blueisthecolour Offline
Fiesta Fan

Registered: 09/08/05
Posts: 245
Loc: Leicester
Quote:

The name's familiar but I don't really remember it. Think it must have been a little before my time! (sorry Peter...)



A little before YOUR time! I've got a good 10 years on you, still not a clue.
In carrot crunching land more BHP = less MPG, there, hows that for the science bit??


Edited by blueisthecolour (27/08/05 09:13 PM)

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#18242 - 28/08/05 08:43 AM Re: Modification vs MPG? [Re: blueisthecolour]
PeterDGM Offline
Fiesta Mad

Registered: 19/03/05
Posts: 293
Loc: Pau,Girona Spain.
I feel really ,really ancient now.But I was a kid at the time.He existed in the time before the roads were jam packed,cars were just becoming popular/affordable and drivers did,t know how ,(probably because there was no need )to reverse into a parking space.If you watched it today you,d pee yourself laughing.And yes it was an Austin 1100 top car for the times.
Bye just off to kick start my zimmer.
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