[SuziBlu]

zook, all I get is opinions, I have plenty dyno results showing different sizes do this or that, what I was after is not, FFS 2" will do, but someone to explain why this or that, JR started, made quite a bit of sense, but hasn't replied.

An opinion is just that, my opinion is different from yours, does not mean im right or rong, neither are you right or rong, its an opinion.

Have a read of this, it shows absolute, that a 2.5" is best, not only for outright power gain, but a far greater (usable) rev range.

http://www.isuzuperformance.com/bills/d ... mparo.html

Like I say, also have stuff that shows 1 5/8 is the ducks guts.

So I came here, asking for some sort of clarification, all I get is, 2" thats cool, an you saying im not listening.

Thats got me fucked.

[31zook]

31zook* wrong* wrong* and*

[atari4x4]

i guess 2" is a happy medium, not too big & not too small. you're not all ways going to be at WOT & i'd say the the DOHC head on that link would flow a bit compared to the 8 valve head on the zook.

[Matthew]

That's test isn't exactly comparing apples with apples, the 2.25 system has a three chamber muffler and the 2.5 has a straight through.

[Marko_SJ]

sideways wrote:

Yeah, except the Clubby runs twin pipes.

With a greater capacity on each side and possibly better volumetric efficiency. I didn't think I'd have to point this out, sorry.

Without knowing what Suziblu is doing, I reckon two inch with high flow cat, good extractors and a straight through muffler.
Why over complicate it and make it too loud and droney?

Edit: Have you looked into why 2.5 or 1 5/8th or whatever may be the ducks guts or why it may be shit?

It depends on your application, if you are running WOT the entire time wider may be better, provided you push the required amount through, however, if you are not, your engine may perform worse.

Basically you know for a given amount of air to get though a certain sized tube you have two scenarios:

1. small tube, air will flow faster and shift the same volume, too much air and too small a tube and you will 'choke' it.

2. big tube, the same amount of air will flow through slower. If you have a small amount of air going through, my understanding is that it will 'back up' and not "extract" fast enough. This will obviously lead to a power loss compared to the optimal diamieter tube, and has also led to the popular "back pressure" myth, where people believe that engines need back pressure to function properly.


We would hate to see you spend money on performance parts and then lose some of your potential gains (your hard work and your money) just because old mate at the exhaust shop reckons it suits him better to make you a 2.5 inch system.

PS fellas, If my theory is wrong feel free to correct me its what I learned searching the net ages ago, and is my understanding, not copied from wikipedia or some other encyclopedia.

[atari4x4]

Matthew wrote:

That's test isn't exactly comparing apples with apples, the 2.25 system has a three chamber muffler and the 2.5 has a straight through.

picks & chooses which bits suits his research.

[MacDaddy]

Ok, it appears the info and opinions arnt enough, so here is some of my real world experience with exhaust upgrades...

When i had my 1988 8V 1.6L Carby Vitara, i had MPH Extractors, 2in system with hiflo cat, and mild baffled muffler, it was a big improvement, but, under 3000rpm, it was some what sluggish, so i adapted my driving style to keep the revs up...

On my 2001 24V 2.5L EFI Grand Vitara, i firstly had a 2in system with hiflo cat, and straight thru noisy muffler, and it was again, a noticeable improvement in engine performance, but, again, it was a bit sluggish under 3000rpm, and again, i adapted my driving style to keep the revs up... after driving it for a while, i did notice that at about 5500rpm, it seemed to feel a bit restricted, like it had more to go, but couldnt... so back to exhaust shop, this time, i had a 2.25in system put on, hiflo cat, and straight thru noisy muffler, this slightly bigger pipe made a big difference, once i hit 3200rpm, its like a small turbo boost, and i get that power right thru till the rev limiter, at 6500rpm...

Its not only the diameter of the pipe, but the length of the pipe to take into consideration, if i understand what you have said previously, you have a very short run of pipe, if you change this to 2.5in, i think you will loose all the gains of the cam, because it will feel gutless at low RPM's, and shift all your power to high RPM's, look at racing/drag cars, short run of big pipe, because they are at WOT all the time, and it works for the motor sport application, on a street car/daily driver, not so much, you will end up with a thirsty, gutless at low RPM, vehicle... when people say 2in is the max they would go, its from real world experience... just because your exhaust guy say 2.5in will work, and is cheaper, doesnt mean shite if it makes your car run poorly in the real world... but... if you want to find out for yourself, then sure, fit 2.5in... i will stick by my opinion/suggestion that 2in is the max pipe size you want to go... end of rant...

[JrZook]

SuziBlu wrote:

JR started, made quite a bit of sense, but hasn't replied.

Mmmmmmmmmhuh??

Thought I did finish using a stock common 3RZ example motor which has A) Alot more cubes than yours have B) A lot more power than yours will have.... Guess work has been taken out for you using factory examples to get an idea of the pipe sizing you require that have been proven to support X Hp.

But hey you have your mind set on the 2.5" so go for it.

[SuziBlu]

I do not have my mind set on a 2.5" system, that is why I asked in the first place. Lots of conflicting data out there.

Gus, I used the link to show that some say 2.5" is the go, not saying, here, im right your rong.

Spoz I should add a link to show 1 5/8ths is the go, but couldn't be bothered. You'd just poke shit at me somehow again.

I have read some of David Visards stuff, and he makes a lot of sense, explains it in laymans terms.

MacDaddy I do have a very short system, but am going to take it out back, much longer, many more bends, thats why I thought 2.5", make up for the extra length and bends.

Visard gives lots of formulas, and I can understand 2" as opposed to smaller, or bigger. According to Visards formua, with a straight pipe, a 2" ID system is good for 164hp, then factor in the loss from bends and muffling.

Thats all I wanted, formulated answers, not opinions or theory's.

I have spent a lot of time and money on this engine set up, and for the sake of a few dollars more, I wanted to "understand" why this or that is the go, and get it correct.

[Fatzook]

SuziBlu wrote:

According to Visards formua, with a straight pipe, a 2" ID system is good for 164hp, then factor in the loss from bends and muffling.

Fatzook wrote:

http://www.mk5cortinaestate.co.uk/calculator5.php

2" mandrel bent pipe will flow enough to make 125fwkw. (or 163HP) You will have NOTHING like this sort of power.

2" is plenty!

To put it in perspective, I'll be running custom headers into 2.5" mandrel system back to the cab, then into 2.25" tail and rear muffler for 200fwkw 2.0L supercharged motor.

The link to a calculator, and me telling you as much, 30 posts ago.

[SuziBlu]

Yea I saw that, but it only gave an answer, not a reason, visard gave the reason.

I like to understand things before I commit, some things, like electricity, I have to just accept, some things, I will study till it hurts so as to understand.

Sorry to have bothered everyone.

[Fatzook]

Sometimes its safe to assume that people far smarter than you or I know what they are talking about. I know that volumetric efficiency can be calculated, and that internal friction creates turbulent gas flows, and throttle possition changes the dynamic flow rates etc etc... But at the end of the day, tuning your exhaust to this extent will nett no measurable gains, as you are working with such a small, inefficient motor to begin with.

It sounds like you have stumbled accross information that you can trust, and have landed on the same result as most of the uneducated opinions that have been offered here.

So now you can get on with the job of making your exhaust and report back with your findings. I for one am keen to see the results.

[SuziBlu]

Pete, at play she is very thirsty, around 25 liters per hundred kilometers, more at WOT. So I assume that she throws a lot of gas out.

When the system is fully functional, unless I take her over 1,000 kilometers to a Dyno for a really good tune, I expect even less fuel milage.

I do trust people here, is why I ask, but an understanding goes a long way in my mind.

[MacDaddy]

SuziBlu wrote:

Yea I saw that, but it only gave an answer, not a reason, visard gave the reason.

I like to understand things before I commit, some things, like electricity, I have to just accept, some things, I will study till it hurts so as to understand.

Sorry to have bothered everyone.

Perhaps, if you had stated this right from the start, this thread would have gone in a more desirable direction... but having said that, you still got some very good info and links to good info... but even with all the good info, real world practicalities, can be somewhat different, as even with all the info/equations etc, having the exhaust system in front of you and working, can yield varying results to all those facts and figures... so we offer our own best opinions/suggestions based on real exhaust experience...

You didnt bother me, i like to talk about exhaust systems, as it furthers my understanding of them and how they work, on paper, and in peoples experience with them...

[shakes]

Suzi - have you driven a similar car with an exhaust slightly to big or to small for the motor?

[Matthew]

Time to end this thread.

Just get 1.626, a 2.0 and 2.5". Dyno them all, and sell off the poor performers.

Thread closed

[atari4x4]

but use a more free flowing muffler on the 2.5" so you can fudge the results.

[droverdave]

double post

[droverdave]

first off i thing comparing differnet engines, horsepower, and exhaust size is a very uninteligent thing to do. You cannot compare different engines like that, they are completely different.

torque at specific rpms is probably a better thing to do, but even then still your not comparing apples and apples.

For one the suzuki/4wd intake track is so complicated that you are most likely losing a fair chunk of performance at high rpms through pressure drop across your intake system. and secondly newer engines make more torque/horsepower for the given amount of petrol, purely based on the fact that they are a better design and are more efficient.

Ok. There is no BEST exhaust.

Here is my take on the whole exhaust situation.

There can only be a best exhaust AT A SPECIFIC RPM!! read that again.

Now talking about only the pipe itself.

My understanding is that exhausts are tuned in order for the gases at the second half of the exhaust, are used to "suck" the gases in the first half (and out of the engine on exhaust stroke). if you can maximise this effect, you can suck the exhuast out of the combustion chamber better, now with modern engines there is an overlap between the intake and the exhaust ports. so this sucking at this time is actually used to suck out exhuast as well as suck a bit of intake charge in as well.

if this doesnt make sense, go and review cam timing and the 4 stroke engine. as the piston gets towards the top of its exhaust stroke the exhuast valve is starting to close, but the intake valve is starting to open at the same time. at this point the exhuast is "sucking" the exhuast out of the cylinder, also sucks the intake charge into chamber at the same time. what you get is bonus intake charge = more power.

now back to exhaust pipe size, if we think about a 1.3L @ 1000rpm @ full throttle. that is 500 x 1.3L x 0.85 = 552Litre/min. (assume 85% volumetric efficiency)

(note: this will be higheras it is now hotter as it comes out, but since exhuast temperature is quite varied, i will ignore this)

if you assume 1.3L @ 7000rpm @ full throttle = 3867L/min

huge differnece in volume of air.

now 550L/min of air has got to get from one end of your suzuki to the other at 1000rpm, and 7 seconds later, you are asking the same exhuast to handle 3800L/min of air. can you see why the exhaust can only be designed for specific rpm band?

So the trade off is between pressure drop in the pipe, with good flow to be able to "suck" the exhaust through, as well as a bit of intake charge.

however, in standard engines, the cam lobe overlap is rather quite small. this allows for very good driveability at low rpms. how ever the amount of time that this overlap occurs at say 1000rpm is very different to say 7000rpm.

thus engines with a small amount of cam over lap (exhaust and intake scavenging), are really good at low rpms, but tend to die off at high rpms.

now back to the exhuast size.

you need to pick where you want the exhaust to have its effect.

g13a exhaust being nice and small, and the camshaft being very small overlap, they go well at lowish rpms. my g13a loves between about 2000-4000rpm, but after 4000 it just makes more noise and doesnt go much faster.

so the exhaust is doing a good job at scavenging at the low rpms, but at the higher rpms i reckon that the exhaust is being choked (ie too much pressure drop across it, from too much flow) and it stops making goo power in the higher rpms. it woudl be nice to put a pressure gauge in the exhaust manifold, that would tell you alot i think.

there are so variables here if you wanted to caluclate it, these include.

-intake manifold presure at high rpms, as mentioned, the suzuki/4wd intake track i suspect is quite restrictive, with airboxes, snorkels plenty of bends.
-cam over lap and lift, you want to maximise that exhaust/intake scavenging (at your desired rpm!!!) so if you want more power at high rpms, you need greater overlap.

now what we havent talked about is mufflers.

as mentioned, pressure drop is the trade off here, every time you ask the air to turn a corner, you increase the pressure drop in the exhaust. grab a fluid dynamics text book and you can get actual calculations for this. a triflow muffler (centre in, side out) asks the fluid to turn 3 x 180degree corners. but remember the pressure difference effect is dependant on flow, so this is why an exhaust can work perfectly well, and be beneficial at low rpm (low flow), but be a complete restriction at high rpm (high flow), simliarly an exhaust can be beneficial at high rpm (high flow), but be too big for low flow (low rpm).

Now from actual personal experience, i removed the standard exhaust on my g13a, chucked on a set of extractors, and welded up a 2.25" exhaust with a dodgy rsonator, and a new triflow muffler.

it has definitely made a difference in the higher rpms (>3000rpm), which tells me that the old exhaust was causing too muhc pressure drop at these high flows. im fairly sure i have lost a slightl amount of punch at the lower rpms. (as expected)

(my data for it making a different at high rpms, is that i travel the gateway bridge in brisbane each day to work, old exhuast = struggled to hold 80km/h in 4th, new exhaust = will hold 80km/h in 5th and will even accelerate to 90km/h if asked)

now if i was to put in a cam shaft with higher duration and lift, i would increase this effect, but i would also lose more low rpm go. its a trade off!

however things like freeing up the intake track (difficult on a 4wd), would makea difference across all rpms, as you are increasing the pressure drop across the intake valve, thus you get some more air/fuel in!

as you can probably tell, ive not told you a definitive "this size exhaust is best", because there are just so many variables!!! someone with the same size exhaust pipe, but different design mufflers, will probably have 2 different experiences..

i hope this helps understand a bit more though.

note, i have not even touched on exhaust gas cooling, essentailly as gases get colder, they take up less room, some exhausts even incorporate a smaller section of pipe at the end of the exhaust to try and keep the velocity up at lower flows.

how much differnce does this make on a tiny 1.3L standard engine? prolly stuff all. but its good to try and understand it.

(note, the problem wiht my 2.25" exhuast is the DRROOONNNE!!, im going to change it to 2" and see how it goes.)

[SuziBlu]

I was hoping that I could design, or get made, something that was specific to a 4-6,000rpm range, either side of that would still work ok, but a target rev range, so the scavenging effect was greatest an so, maybe, better power.

[JrZook]

droverdave wrote:

Now from actual personal experience, i removed the standard exhaust on my g13a, chucked on a set of extractors, and welded up a 2.25" exhaust with a dodgy rsonator, and a new triflow muffler.

So how much did the change to a 2.25" pipe alone contribute to the performance increase?? To many variables changed at one to make any reasonable conclusions about pipe size....

[want33s]

atari4x4 wrote:

FFS it's not a race car, 2" will be plenty.

just thought you seemed keen on that supercharger kit & would need to ditch the dcoe's for it

Why couldn't the DCOE's be used on top of the blower with a custom 90 degree manifold?

Not this exact manifold but something similar.

[SuziBlu]

Crikey, that looks nice.

[atari4x4]

sure the could still be used with a heap of dicking around, but whats the point of twin DCOE's when they suggest a single 32/36?

i'm guessing suziblu is going to have to choke down the side draughts & drop jet sizes running twins on a 1600 if it does ever end up being dyno tuned.

[SuziBlu]

The basic tune is already set for a 1.3l, may be a tad on the lean side for a cammed 1.6l

[atari4x4]

they 40's or 45's?

[SuziBlu]

40s, 45 were too big, even the 40s are choked down a bit, so 45s being more expensive was a nono

[atari4x4]

ahhh cool, thought they were 45's for some reason.

[SuziBlu]

I have no idea why, but they will not fit the Maruti without moving the brake master, and it has no booster, on the yellow monster, they will fit perfect and with a brake booster, someone upstairs hates me.