High flow exhaust better fuel economy?

[Crampy]

Just something I've been wondering about. Does putting a higher flowing exhaust on a car do anthing to fuel economy (makes it worse or better)?

Anyone with experiences of economy before and after aftermarket exhaust fitting?

It will free up the engine to make more power (if done right), but does it help/hurt economy when cruising?

Just curious, that's all. (and maybe I want a 3 inch exhaust on my Aristo )

[jakesae101]

ive hear lots about better economy after removing the cat depends how restrictive the factory exhaust is

[Crampy]

For example.
I've "heard" of people with rather large fart canon exhausts putting a silencer in to quiet it down, but it made the economy worse.
Is it because it's now flowing less, or just because fart canons and silencers are $hit and can kiss my nut sack (or other more technical references)?

[Crampy]

ive hear lots about better economy after removing the cat depends how restrictive the factory exhaust is

I was thinking about decatting the Aristo, but I need to be careful as it can cause rather nasty boost spikes if going too big with the dump pipe.

[B_giB]

In theory it can improve economy, but thats if you drive nicely.

Most people dont see improvements as the typical person that puts a free flowing exhaust dont drive in an economical manner.

[jakesae101]

For example.
I've "heard" of people with rather large fart canon exhausts putting a silencer in to quiet it down, but it made the economy worse.
Is it because it's now flowing less, or just because fart canons and silencers are $hit and can kiss my nut sack (or other more technical references)?

id rather not kiss your nut sack as thats what my car has had since ive braught it and ive just been to lazy to change it but there are many diffrent opinions on size of pipe and the likes

[Crampy]

For example.
I've "heard" of people with rather large fart canon exhausts putting a silencer in to quiet it down, but it made the economy worse.
Is it because it's now flowing less, or just because fart canons and silencers are $hit and can kiss my nut sack (or other more technical references)?

id rather not kiss your nut sack as thats what my car has had since ive braught it and ive just been to lazy to change it but there are many diffrent opinions on size of pipe and the likes

I just added the nut sack thing in so there was some technical jargon in this thread to keep the mods happy and not move it to general discussion
But seriously, big pipes seems to be the go with turbo cars, but it is not always about performance, especially WOT performance.
I mean how often are we really at WOT (on a street car anyway)?
I'd like to find a happy middle ground. Good performance, but quiet for long trips. I think it comes down to proper mufflers and not fart cannons.

[Crampy]

In theory it can improve economy, but thats if you drive nicely.

Most people dont see improvements as the typical person that puts a free flowing exhaust dont drive in an economical manner.

I try to drive my Aristo in an economical way when doing long trips, as I fail the see the point of fanging it everywhere. The economy is actually quite good (for a big car) when just cruising at 100km/h on the motorway. I was sitting at around 11km per litre on my last trip to Hamilton.
But when I open the taps on it, I don't want the 12 year old catalytic converters (and rest of the exhaust for that matter) choking the hell out of it either.

[Crampy]

Oh and some might be able to tell from my ever so subtle hints. I'm not the biggest fan of fart cannons, as they keep me awake from twats fanging down Hobsonville road all hours of the night/morning.

[Quint]

I hate altezza exhausts, terrible noise imo. (sorry guys and girls that own altezzas with big mufflers!)

Will keep any eye on my economy now that i've freed up the exhaust. Should be better, by how much though.*shrug*

[sergei]

there is no need for fart cannon for good flow. Fart cannons are terrible mufflers.

[Crampy]

there is no need for fart cannon for good flow. Fart cannons are terrible mufflers.

They sure are.
People have suggested Flowmasters in the past, but they're not exactly good either. They are baffled, but people seem to buy them for the sound and not necessarily the flow (read dirty big V8 clowns that like the grumble.)

[Crampy]

I hate altezza exhausts, terrible noise imo. (sorry guys and girls that own altezzas with big mufflers!)

Yep, I have heard a lot of tinny raspy Altezzas and 20V Levins/Truenos for the matter. And lets not even start about the multiple VTECs around with horrible exhausts (or lack of).

[frost]

I hate altezza exhausts, terrible noise imo. (sorry guys and girls that own altezzas with big mufflers!)

Will keep any eye on my economy now that i've freed up the exhaust. Should be better, by how much though.*shrug*

OMG its so true, there is a white altezza down from me and every day it takes off with this disgusting sound, worse then the pineapple can back in the days,
i'd be careful about going to free flow exhausts on some newer cars, in the states the bmw 745 will use alot more fuel if the front half of the exhaust is changed,

[Crampy]

Will keep any eye on my economy now that i've freed up the exhaust. Should be better, by how much though.*shrug*

What's the car/engine and what exhaust have you got now? Just getting ideas going. Is it quiet, or loud but acceptable, or just down right rowdy?


Now take my Aristo for example. Not a lot of mods planned, but with TOM's ecu I'll probably go to 1(ish)bar boost with the stock turbos. I have plans for a intake and a few intercooler ideas buzzing around in my head. So lets say 250wkw isn't out of the question.

What size exhaust is ideal? 2.5, or is that too small? 3inch, with two proper turbo flow mufflers?

[Crampy]

I hate altezza exhausts, terrible noise imo. (sorry guys and girls that own altezzas with big mufflers!)

Will keep any eye on my economy now that i've freed up the exhaust. Should be better, by how much though.*shrug*

OMG its so true, there is a white altezza down from me and every day it takes off with this disgusting sound, worse then the pineapple can back in the days,
i'd be careful about going to free flow exhausts on some newer cars, in the states the bmw 745 will use alot more fuel if the front half of the exhaust is changed,

Really? Do you know why it would it cause it to use more gas by chance? Maybe the stock ECU not being able to handle the change in flow? That's very interesting.

Pity about those Altezzas, as I still really like them. I wanted one years ago.

[Crampy]

I've seen on a few American Aristo/Lexus and Supra sites there are guys using electronic exhaust cutouts. They're sort of like those Varex mufflers, where they have quiet path or free flow path for the exhaust.

They are pretty much a butterfly just after the dump pipe, when closed goes through the exhaust, when open is like running an open dump pipe.
Makes $hit loads of power, but obviously with the associated noise increase. Close it up though and you have a nice quiet cruiser.

Problem being, these are illegal in NZ. Good concept though.

[Guss]

havn't looked lately but when i did the rules were worded such that the exhaust could not be cabin adjustable by the occupants. Electronic control would fit through the loophole ? however venting exhaust ahead of passenger compartment would not.
In saying this some of the newer audi's do have in car adjustable exhaust silencers. how these get WOF's?
I have a butterfly valve in the exhaust of my car, it makes a huge difference both to Db and to kW.

[Crampy]

havn't looked lately but when i did the rules were worded such that the exhaust could not be cabin adjustable by the occupants. Electronic control would fit through the loophole ? however venting exhaust ahead of passenger compartment would not.
In saying this some of the newer audi's do have in car adjustable exhaust silencers. how these get WOF's?
I have a butterfly valve in the exhaust of my car, it makes a huge difference both to Db and to kW.

Yeah i've seen some euros that have valves in the rear mufflers.
Sort of like this: http://www.trademe.co.nz/Trade-Me-Motor ... 381518.htm
and these from an Audi RS4: http://www.trademe.co.nz/Trade-Me-Motor ... 775649.htm

[Crampy]

Also, out of interest, Does having the butterfly closed have any effect on fuel economy?