High flow exhaust better fuel economy?

[Crampy]

Boost actuated exhaust cutout.
http://www.youtube.com/watch?v=m5gaAuGNk5M
Cool idea. Makes good power increase.

Now is that legal in NZ? I would think not, but can anyone ellaborate?

[edwagon]

Turbo engines are easy to keep quiet - the exhaust wheel does alot of the 'muffling', so the exhaust has a pretty easy job!

on an Aristo/soarer etc, I stick with the twin pipes, and run 3" off the turbos, through an 18" coby resonator behind the gearbox and then into twin 2.5" pipes, and then out through 2.5" 'straight through' oval mufflers - get the biggest you can fit behind the bumper. You can run fancy tips to get the look you want.

The big oval mufflers have plenty of glass packing around them and so absorb alot of noise while not restricting flow - and the coby just helps take the edge off. Make sure you get 'straight through' tho - the chambered mufflers are more for n/a and are too restrictive imho

on a jz, this style of exhaust has a nice, deep tone, and is very civilised noise wise - def louder than stock (stock = silent), but only minimally, and very smooth and nice sounding.

I didn't find that it made my 2jz overboost at all, even with 3" straight off the dump - boost did rise, but not like the horror stories that you see on some forums. Mine wasn't vvti tho, so maybe that was the difference....

[offensive]

my tezza has nastey exaust noise too
TRD exaust, has converter and another silencer, still has cackely rattley noise

goddam 3s

[Adamal]

You pretty much need to make the exhaust depending on flow characteristics etc.
Theres also the pulsing/scavanging effect. If you have an exhaust too big, its not going to work properly. Too small, its going to take the engine to push it, sapping a bit of power out of it.

[FLAWLES]

dont know why i havent seen this thread before

on my jz im runng my old vvti 1jzge tanabee system, which is 2.5' straight through, no cat, and two resonators, i did have the muffler to suit but due to some young fool rear ending me i now have a xforce cheapo muffler ( and i tell you what its lasted well )

my systme is loud when i have my foot up it ( imagine hell opening up and demon spwan screaming through the gates of hell ) its amazing the sound will rival any v8

but at idle and 100km/h its fine, my wee nipper loves it

i doo need to start looking at upgrading it soon due to the power increase but for now it will last

fuel eco, i can honestly say i havnt noticed mine change a hell of a lot................i do how ever get where im going faster

[Crampy]

I must say I do like the idea of having twin mufflers. It would suit the look of the car better, as it comes stock with two.

I'l have a look into getting an exhaust down the track, it good to get these ideas first though.

I can't say I entirely agree that mufflers need to be straight through though. Properly designed turbo flow baffled/chambered mufflers still flow very well.

I do agree with needing big body mufflers. The fart cannon has no size to it, so will never soak up the sound as good as a big body oval muffler.

[edwagon]

I must say I do like the idea of having twin mufflers. It would suit the look of the car better, as it comes stock with two.

I can't say I entirely agree that mufflers need to be straight through though. Properly designed turbo flow baffled/chambered mufflers still flow very well.

I do agree with needing big body mufflers. The fart cannon has no size to it, so will never soak up the sound as good as a big body oval muffler.

Most guys running turbo jzs just run a single 3" for ease/cost, but I like the factory twin look - and it gives you two mufflers to soak up the noise as well as generous exhaust area.

I like the straight thru style mufflers and have had great success - Im lead to believe that the chambered/baffled mufflers (like factory style or lukey etc) are more for na cars, and are ok on v8s etc, but steer clear of them for turbos. Thats just what Ive been advised tho (by an exhaust wholesaler who was selling me stuff....)

Please yourself - just go with whatever the installer recommends - that way you have a comeback if the system sounds/performs poorly.

[Crampy]

Yeah, that's true. I might go and have a chat at Al's Mufflers. The dude there is good and doesn't seem to be full of $hit like some people I've seen (midas, pitstop, etc). Not saying those places are necessairly bad, just sometimes you get a tool that doens't really know what they're on about.

[B_giB]

I have heard nothing but good reports on Al's muffs.

Pitstop Wairau was good when Lance was there.

[Crampy]

I have heard nothing but good reports on Al's muffs.

Pitstop Wairau was good when Lance was there.

I've had a bit of work done there already and will no doubt go back. Good work.

[frost]

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

on my 745 is does,
if i push sport mode, the butterfly on the second muffler opens and the noise is great
but if i keep the butterfly open all day i chug the gas fast, however this could also be a ecu fueling thing due to "sport mode" mapping.

[ChaosAD]

The straight through mufflers that are shaped like a standard muffler are the way to go, they flow more and have more damping material than the stainless cannon mufflers.

Obviously if you do anything to improve the breathing of the engine your going to use more fuel

[Adamal]

Obviously if you do anything to improve the breathing of the engine your going to use more fuel

Hmm... Not necessarily. If you make it easier for your engine to breath, you're improving the efficiency.

If you remove a form of restriction, less force is required by the engine to push the exhaust out.

Its a very similar concept to rally cars using intake restrictors to restrict the HP.

[MAGN1T]

Obviously if you do anything to improve the breathing of the engine your going to use more fuel

Not really, it depends on the computer.

If you've got speed density then changing almost anything has the potential to change the AFR because the VE changes.
If it uses an AFM then there's no reason why the AFR or fuel economy will change.
If it's tuned properly a modded motor won't use any more fuel than a stock motor under normal road conditions.

Steve

[Crampy]

Obviously if you do anything to improve the breathing of the engine your going to use more fuel

Hmm... Not necessarily. If you make it easier for your engine to breath, you're improving the efficiency.

If you remove a form of restriction, less force is required by the engine to push the exhaust out.

Its a very similar concept to rally cars using intake restrictors to restrict the HP.

Yeah I was hoping that would be the case. Dunno if it'll work in practice for my car though.
I'd say a 12 year old catalytic converter isn't going to be the flashest for flow.

[Crampy]

Fuelling will increase with performance gaining mods, eg breathing mods, boost increase etc. As the motor is making more power.

But at 100km/h the engine is on bugger all load, so I wanted to know if the fuel economy would be better as the car now breathes more effeciently, compared to a stock exhaust. Or is this not really the case, as a stock exhaust will be able to flow fine at those lower loads?

[Quint]

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?

2.5" straight through, 2" dump pipes collecting off both turbos, 1ggte. Put a new muffler on and its pretty much silent at idle.

My truck with standard exhaust is louder.

[mjrstar]

I have just de-fartcannoned my car. It had a fairly small silencer in it when i brought it, i have also gone from 2 1/2 inch to 3 inch.

The new exhaust is quieter although slightly deeper. It all comes down to ensuring you have a decent quality resinator and well made rear muffler to match. (and no 5 inch tips)

The car is slightly quieter than before and has gained a bit of low end boost response and like pulling passed 7000rpm now.

My old Mivec Diamante had the flapper by-pass in the exhaust, i guess it's of some use or they wouldn't bother doing it.

[Crampy]

I have just de-fartcannoned my car. It had a fairly small silencer in it when i brought it, i have also gone from 2 1/2 inch to 3 inch.

The new exhaust is quieter although slightly deeper. It all comes down to ensuring you have a decent quality resinator and well made rear muffler to match. (and no 5 inch tips)

The car is slightly quieter than before and has gained a bit of low end boost response and like pulling passed 7000rpm now.

My old Mivec Diamante had the flapper by-pass in the exhaust, i guess it's of some use or they wouldn't bother doing it.

That's good to know. It looks like I can get away with a 3inch system for my Aristo, provided the mufflers are good.
Like this system on Ryan's car: viewtopic.php?t=72619&start=20

[mjrstar]

^^ very nice system at a good price (i asked Ryan about this a while ago)

I went cheap an brought a 2nd hand cat back exhaust for 300 and made my own front pipe. Although i didn't realise 3'' flexi's cost more by weight than gold!!!


(click on them for bigger pics)