[Millsy]

16B LWB, 235's with extractors, is there any real gains to be had by getting a system fitted, if it's only noise then bugger it.
Recomedations/advice.
Thanks Millsy

[Joe]

You will get some more power if ya get a 2 inch system fitted and if ya don't like noise get them to fit a quieter muffler
Nice vit btw, don't think i've seen a silver SE vit before

[lil monster]

There will be an improvement in performance, due to the rate at which exhaust gasses can escape though the larger pipe, If u don't like sound try a tri flo muffler, I no with mine I wanted nosie so it was done with a high flow muffler into a hot dog and then a dump pipe.

[Millsy]

Cool, thanks guys, will go with the quieter one after I get some quotes.

[Fatzook]

At best, you will see a 5% increase in power. realisticly, the only gains will be 'seat of the pants' type.

[lil monster]

I no mine, cat back 2.25 inch onto a 3 inch dump pipe, cost 300 so that's like a ball park price, I live in south Australia not sure where u are

[Veggiesoup]

I put a turbo charade muffler on mine it gave it a real nice note and backfire/gargle on decel

[atari4x4]

pretty sure millsy is after stealth

after 17yrs of loud cars i'll be doing the same with my new blagon especially being an auto... last thing i want is it to drone & bellow.

+1 on never seeing a silver SE estate, look great

[christover1]

Engines need a certain amount of back pressure to work best.
Too big an exhaust could rob power.
A decent exhaust shop should be able to advise whats best for your needs.

I have extractors/headers and a 2" pipe and power seems ok to me.
Can't comment on noise, I am a bit deaf.

[Buddies72]

christover1 wrote:

Engines need a certain amount of back pressure to work best.
Too big an exhaust could rob power.
A decent exhaust shop should be able to advise whats best for your needs.

I have extractors/headers and a 2" pipe and power seems ok to me.
Can't comment on noise, I am a bit deaf.

My system is the same, with a 2nd hand Pajero Cat to match up with the 2" & muffler, was $400 from the extractors back.

Noise is minimal, but the engine really picked up torque in mid-range, which is where you want it when wheeling.

[sideways]

Fatzook wrote:

At best, you will see a 5% increase in power. realisticly, the only gains will be 'seat of the pants' type.

You'd have to be VERY in tune with you car to feel a 5% difference IMO. I think most people would struggle to feel a 10% difference.

IMO when people talk about how much of a power increase their exhaust has given them, it's either a sort of placebo effect or just that it sounds faster.

[Fatzook]

Agreed.

I noticed a slight difference when I fitted extractors and mandrel system to my SV. But I chalked that up to removing the clogged up old cat and muffler. I reckon it may have recovered 5% of the 15% power its lost over its 220K lifespan

[Mike57]

I agree with Fatzook and others. I have not yet seen any real evidence that changes to exhaust do anything at all to improve power or torque and the only Dyno curves I have seen show the Jimny was worse off after fitting after market extractors and exhaust. When I find some hard evidence that a bigger exhaust does anything other than make more noise I will be spending the money.

Not that extractors and a properly designed factory set up is not a good thing. My Calais puts out 200kW and has plenty of low end torque with a factory designed twin exhaust system with extractors. Does not make any noise but plenty of grunt. What I have my doubts about is improving on what the factory design engineers have come up with.

I know I have had this discussion before on this forum but I am still looking for the evidence. Unfortunately the average Zook owner does not spend the money on before and after Dyno measurements.

[jdk81]

These days there is a lot of effort put into designing factory exhaust systems, for best power and efficiency.
Manufacturers arent stupid, if there is a simple cheap way to gain ponies, they would be using it. If 5% gain from $100 worth of extractors, theyd fit it.

It would stand to reason there would be considerable gains, doing extractors and what not on older cars where they didnt have the technology to simulate the fluid flow through the system. Things were packaged to fit and be cheap.
However, it is still probably mixed results. I doubt they are tuned, and in the event they are tuned, what rpm and load the extractors are tuned for.

Think of how many guys sit on computers calculating this stuff for the intake, head, cylinders and exhaust.
I dont know how much experience your local muffler shop guy has, unless its a big company where the designs are done in house with lots of testing and the product is costing a signifcant amount of money, id say your buying fabgineering.

Do they have their place? sure,
When doing an engine conv, when the stock stuff cracks, when you need to replace most of the system, etc.
IMO most gains would be because of removed a blocked cat etc

Boring part...
How the amount of exhaust flow differs under load.
The flow characteristics differ under load.. consider 4000rpm no load, vs 4000rpm @ max power
4000rpm no load, would still use little fuel (throttle is not fully open), whilst 4000rpm at wot will be max power at max consumption (assumption).
There will be significantly more air and fuel going into the engine, thus more exhaust and heat going out.
pv/t = pv/t

Under rpm, pretty easy, using intake air only etc.
engine size x rpm... at 1.6@1000 rpm = 1.6*1000*0.8(pumping losses)/2(only combusts every 2 cycles)= 640 lpm
1.6@4000 rpm = 2560 lpm.

[banga]

only time I have notice gains in exhausts was on my old liberty
when I got the whole exhaust dome from the headers back I think the biggest improvement
Was from the high flow cat that was fitted. When I fitted extractors to tje vit no change just sounds good

[sideways]

What jdk81 said, 2 stage exhaust manifolds are close enough to the extractors design, extractors give you much more freedom with your primaries though. Pretty much everyone just gets a new exhaust for the sound anyway, "more power" is just an excuse.

Anyone who thinks a car manufacturer is stupid is ignorant themselves, though I do think the day they designed the LJs steering was bring your bong to work day.

Having said that, I'm hoping to get some gains (and of course, a nicer sound!) by fitting extractors and replacing the first muffler with a 1 3/4" glass pack hot dog, stock system from there on. Though the primary reason is that my manifold needs new studs, I already have the extractors and the hot dog is much less venerable to damage (it's made of much thicker material and has curved edges so it wont get battered/flatened as easily as my now quite flat stock first muffler).

[JrZook]

jdk81 wrote:

Under rpm, pretty easy, using intake air only etc.
engine size x rpm... at 1.6@1000 rpm = 1.6*1000*0.8(pumping losses)/2(only combusts every 2 cycles)= 640 lpm
1.6@4000 rpm = 2560 lpm.

Pumping losses is actually volumetric efficiency which would probs max out at 80% for a 2V head thus your calc would be about right for a 1.6@4000RPM which is around its max torque (max VE). Idle even at WOT VE would probs be maybe ~35% max therefore it would pump only ~280lpm.

Space and cost considerations fall heavily in factory manufacturing processes thus compromises are made. The guy on the computer with heaps of design experience will optimize the system based on all factors with maximum performance not necessarily at the top of the list.

[Gwagensteve]

christover1 wrote:

Engines need a certain amount of back pressure to work best.
Too big an exhaust could rob power.

Why does this internet myth still exist?

How much backpressure do you think this exhaust provides?



No engine has ever, ever needed a "certain amount of back pressure" to work best.

I think this myth has come about from from three things.

Noticing that engines run poorly if the exhaust is broken.

Noticing that engines run poorly if they take the exhaust manifold off.

The cause is that without exhaust runners, the engines don't scavenge. Don't confuse scavenging with backpressure, they aren't the same thing.

Also, a stock engine that has a carb tuned for a compromised stock exhaust won't run properly with the exhaust removed. That's doesn't mean that a engine "needs" backpressure, only that it's tuned "down" to the stock exhaust.

A 2 stroke engine simply won't work with any back pressure, and the more you improve the scavenging, the better they perform. That's basically the same as a 4 stroke engine (except a 4 stroke can function with back pressure, just not as well as with less)

Have a good look at that pro stock dodge engine. Note that there's a little "crimp" at the extractor collector. That's there to provide scavenging. That's what the collector of extractors does.

Downstream of the collector of an extractor, there's no advantage in "adding" backpressure. That's actually why it's called an "extractor" - it extracts the gas from the engine through getting each pulse to "pull" the pulse after it along. Once you get to the collector, that doesn't happen any more, and all you need is to get the gas into the atmosphere.

Steve.

[christover1]

So a rephrasing is:
Stock engine needs exhaust fitted,
or retuning is needed for exhaust changes or removal.

[Gwagensteve]

That's a pretty fair representation.

It's also very dependant on the quality of the stock manifold. A stock 1.3 sierra has a fairly poorly designed manifold, but a G16B has a very well designed manifold.

Adding a massively free-flowing exhaust to a stock 1.3 might very well make it run dangerously lean, but also consider the camshaft makes a huge difference to how much air the engine can swallow. More camshaft will require more exhaust (and inlet) flow.

Like everything it's a balance, but saying "engines need back pressure" is an oversimplification that's a pervasive myth.

Steve.

[jdk81]

I think pressure waves for scavenging is misconstrued as backpressure.

Generally a tuned extractor system will be tuned for a certain use where the waves are timed right to assist in scavenging. Unfortunately this doesnt work ideally through the whole rev range.
You are generally stuck choosing between smooth power, or total power.
If you want to put extractors etc on you need to tune for it. And you may find the new power delivery to be not as useable as it was before (or vice versa). Bolt up and drive away, may sound better, but it will move the power delivery curve and may inhibit it until you tune for it.

More info on pressure waves (often referred to as backpressure)
Yamaha pioneered exup valves, these exup valves open and close at the 4-1 collector creating its own artificial atmosphere. Effectively what they can do, is have the pressure waves for scavenging being timed right throughout most of the lower rev range.
The exup valve is closed at 2000 rpm, fully open at 6000rpm and bike redlines at 12-13000rpm.
This makes the torque curve much more useable and friendly. On a light bike with stupid power from factory, making it friendly power on tap is nice.

From experience, putting a slip-on exhaust (instead of the factory) the exhaust dynamics changed so much that the bike was down on power throughout the rev range.
Ideally if you were to remove the exup, and install a full system, you would need to install a new ecu/chip and tune. You are now sacrificing the bike being more useable for raw power. More suitable for a race track, not so much normal riding.

Doing a custum exup install on a gti engine would be quite interesting.

As per the engine steve linked.. that extractor is tuned for raw power, with little concern to useable power... you wouldnt tune your car that way.

Back on topic, just save your $ until it needs to be done, $/ponies is probably similar as fitting a hiclone, or nitrogen in your tyres.

[sideways]

Gwagensteve wrote:

A 2 stroke engine simply won't work with any back pressure

I disagree, obviously then every 2 stroke engine with an exhaust system wouldn't actually work. The correct thing to say is that more back pressure will lower the performance of a 2 stoke engines performance, just as it will with any other engine.

Having said that, some expansion chamber designs utilize back pressure to create a denser medium for the rebounding pressure wave to travel in. Obviously, denser medium = better shock wave performance. Better shockwave performance = better scavenging. Aside from that variation on the design, the less back pressure the better.

Geez it burns my goat when tards say 2 strokes need back pressure.

[sideways]

Gwagensteve wrote:

A 2 stroke engine simply won't work with any back pressure

I disagree, obviously then every 2 stroke engine with an exhaust system wouldn't actually work. The correct thing to say is that more back pressure will lower the performance of a 2 stoke engines performance, just as it will with any other engine.

Having said that, some expansion chamber designs utilize back pressure to create a denser medium for the rebounding pressure wave to travel in. Obviously, denser medium = better shock wave performance. Better shockwave performance = better scavenging. Aside from that variation on the design, the less back pressure the better.

Geez it burns my goat when tards say 2 strokes need back pressure.

[Gwagensteve]

Er, I'm a bit confused at your point there sideways. I would imagine that increasing backpressure would massively reduce the performance of a 2 stroke, whilst a properly tuned expansion chamber will provide almost no backpressure at the exhaust port but very effective scavenging.

I think discussing shockwave performance might be a bit beyond the scope of 4 stroke owners. I do understand the point though.

In any case, I think we're effectively agreeing about the misunderstanding between scavenging and backpressure.

Steve.

[Mike57]

Well I hope Millsy has got the message now?

[Millsy]

Mike57 wrote:

Well I hope Millsy has got the message now?

Fuck me, I got lost in all that, it looks like there is no point throwing money at a system unless needed (damaged).
I was quoted $800 for a 2" system from the extractors back with a Hi Flow Cat and Hotdog......like friggin hell.

[MacDaddy]

Another exhaust thread, what fun...

I have had an aftermarket, sports exhaust put on every car i have owned... and no matter what anyone says, i can feel a difference, while it may only be 5% improvement, it can compensate for/off set the power drain of the alternator when charging... and imo, the car just runs a whole lot better in general, even improves economy...

Yes with a sports system, it gives you a lil less power at lower rpm's, and shifts the engine power to higher rpm's, normally 3000rpm's and above, power feels awesome in high rpm's, but i just adjust my driving style a bit to compensate at low rpm's, its no biggie... as for noise, its personal choice, i like noise, so got a straight thru muffler... i cant see the point of putting a quiet muffler on a sports system, it defeats the purpose, a milder muffler is a better choice, if you dont want to much noise... i highly recommend getting a hi flow cat as part of a new exhaust !

As for pipe size, its a contentious issue, some think the bigger the better, and it usually turns out, the biggest isnt the best, unless its a race/drag car...
From my own experience, i have found -
For a 1.3l = 1 7/8in...
For a 1.6 = 2in...
And for the GV 2.5l, i started at 2in, still felt a bit restricted, went to 2.25in, works really well...

As for costs, it varies, but from shopping around -
Extractors = from $200 to $500
Hi Flo Cat = $300
Hi Flo Muffler = $100
Pipe = $100 to $150...

[Chop]

Don't waste your money on a high flow cat on a 1.6 vitara, its money for nothing. The difference between a new standard cat and highflow cat would not be of any gain on a lower horsepowered cars.

[MacDaddy]

Chop wrote:

Don't waste your money on a high flow cat on a 1.6 vitara, its money for nothing. The difference between a new standard cat and highflow cat would not be of any gain on a lower horsepowered cars.

Hmmm, not sure i agree with that... a stock cat is THE biggest restriction... i got a hiflo cat put on my old 89 1.6 carby vit, it has the lowest power of the 1.6 range, and i felt the difference, the engine just felt like it farted alot freer than before... if you can afford a hiflo cat, then i recommend getting one...

[atari4x4]

MacDaddy wrote:

Chop wrote:

Don't waste your money on a high flow cat on a 1.6 vitara, its money for nothing. The difference between a new standard cat and highflow cat would not be of any gain on a lower horsepowered cars.

Hmmm, not sure i agree with that... a stock cat is THE biggest restriction... i got a hiflo cat put on my old 89 1.6 carby vit, it has the lowest power of the 1.6 range, and i felt the difference, the engine just felt like it farted alot freer than before... if you can afford a hiflo cat, then i recommend getting one...

i'd say the stock cat would have been pretty blocked when removed, did you do back to back testing with a new stock cat & a hi-flow cat to back up your claims or just fit the hi-flow atfer removing the original exhaust?