[Che]

I got some RPM extractors that came with the car when I bought it, and now I have the coin it's time to install them. While i'm at it I'm gonna overhaul the entire exhaust system at the same time and get rid of the cat converter, which I no longer need.


Just wondering if I should go a 1.5 inch system, 1.75 or 2 inch system? What's the pro's and cons of each size?

After doing a little investivating i'm thinking of going a smaller diameter as it'll be better suited to the lower RPM ranges I mainly use - a bump up in the bottom end torque would be much more useful to me than top end power gains.

I was planning for a 2 inch system, but I don't see the point now as it'll rob torque from the sub 3000 RPM range, and gain performance in a rev range that I barely ever use.


So now i'm scratching my head a little... Anyone else gone smaller diameter over a larger exhaust size?

[86slowsierra]

most ppl go for a 2".
anything is better than nothing.

[Che]

How far are people willing to rev out their Sierra's? My past cars have all been V8's or diesels, so I find it unnatural to wind an engine out to the far side of the RPM guage

[shep]

i rev mine until it wont rev any harder. i have seen mad kennys taco go past
the numbers and it is the sweetest running sierra that i have seen.

[shep]

i dont go past 6500 on purpose any way.

[atari4x4]

shep wrote:

i rev mine until it wont rev any harder.

mine loves to rev, 5000rpm & upwards... it also does have a rev limiter @6500 or somewhere around there

[Reubs]

My G13 powered Zuk regularly and happily maintains 4200RPM (about 125kph) in long trips and it has 180,000km on it since a rebuild 4 1/2 years ago.

My G16 powered Zuk once sat between 5000 and 5600RPM for about 45 minutes about 18 months ago. It'll be replaced soon because of a cracked block but it has only been a problem in the last 6 months. I also do stupid things like 80/h whilst in low range.

Point is the G series engines love to rev...

Oh and as for exhaust - I went from 1 3/4 to 2", and should've stayed 1 3/4". The 2" seems to sap torque.

[Jccck]

I went from a 1 1/2" to a 2" on my Sierra, has a 4K Corolla engine
No cat, standard exhaust header, straight-through muffler

It gained a little torque in the low-end, around 1.5-2.5k which i was really impressed with

[alien]

yup - 1.5" for 1.3L, 2" for 1.6L...

and KEEP YOUR CAT CONVERTER!!!!!! Its illegal to run without it and the fines are HUGE.

I run 2" pipe and a 2" cat, so its not restricting flow, and its still doing its job.

[MacDaddy]

1.5in is very close to stock exhaust... so you may as well stay stock if your thinking of going that small... it would just be a waste putting extractors on...

If you got a 1.3L, i would go 1 3/4in, its a good in the middle range, and you will get improved torque over a wider range of RPM's...

If you have a 1.6L, definitely go 2in, had it done on my 89 Vit, got a BIG improvement over 3000RPM...

Not quite sure why you want torque at low RPM's though... the Zook engine is made for high RPM, thats where they excel, they can sit on 4000 to 5000 RPM all day... its not a diesel engine is it ?...

[alien]

You'd be surprised MacBear - offroad i hardly rev mine above 3000rpm... the 1.6EFI puts out enough torque with my extractor/exhaust setup that i just dont need to rev it - and when i do occasionally rev it its only for wheelspeed instead of changing gears - if the option is there to change gears ill sooner do that =)

[Che]

alien wrote:

yup - 1.5" for 1.3L, 2" for 1.6L...

and KEEP YOUR CAT CONVERTER!!!!!! Its illegal to run without it and the fines are HUGE.

Not a worry for me mate - it's one of the perks of running straight LPG

[dm90]

does this also apply to a jimny.

1.3L = 1.5" ?? i was thinking about extractors and exhaust but was gonna go for a 2" system.

my jimny likes to rev also, going up big sand dunes it would be around 6000 RPM, but on the road i like to keep it at or below 4000

[Moph]

I've got a 1.75" exhaust + extractors + cat + muffler + resonator on my 1.3 and find it just about perfect. Little bit of throaty growl at idle, quiet at speed, breathes a bit easier at the top end. Running 31 STTs with 6.5s and stock diffs it still sits happily on 110kph on the flat with a little in reserve in 5th. Think 2" would have been more noise with no gains. Definitely noticed an improvement over the stock system, but then my cat was completely clogged when I had the exhaust replaced...

[ZookiMonsta]

I run 1 3/4 and 2 from the muffler (hotdog) back. Sounds good,
goes hard, and revs like a zook.

[shep]

my swb has a 50mm system with pacemaker headers, commodore sized turbo
muffler, no cat and it is bladdy loud and when ya back off at lots of revs a blue flame spits out.
seriously worth it.

[eldo]

Mine has a two inch system, annoyingly loud, sounds like a Gemini. I would go a 1 & 3/4 system

[Che]

A flamethrowing exhaust would be just the ticket!!! I want one, I want one now!! Perfect for the arsehole tailgater.

[Jccck]

che_guitarra wrote:

A flamethrowing exhaust would be just the ticket!!! I want one, I want one now!! Perfect for the arsehole tailgater.

Mine can do that, haha

Drive along at about 50, turn the car off in neutral.. Keep your foot flat to the carpet for 5-10 seconds, turn it on with your foot still flat!

Booooom, with a foot long flame
I don't think it's good for the car however

[MacDaddy]

dm90 wrote:

does this also apply to a jimny.

1.3L = 1.5" ?? i was thinking about extractors and exhaust but was gonna go for a 2" system.

my jimny likes to rev also, going up big sand dunes it would be around 6000 RPM, but on the road i like to keep it at or below 4000

Ooooo... nope the Jimny has a performance engine... and if your Jimny likes high RPM, i would be very tempted to go 2in !

1.5in would strangle it... i would get at a very min 1 3/4...but maybe 1 7/8 would be good... but because of the Jimny G13BB engine... i would go bigger to 2in...

[steak_knife]

Jccck wrote:

che_guitarra wrote:

A flamethrowing exhaust would be just the ticket!!! I want one, I want one now!! Perfect for the arsehole tailgater.

Mine can do that, haha

Drive along at about 50, turn the car off in neutral.. Keep your foot flat to the carpet for 5-10 seconds, turn it on with your foot still flat!

Booooom, with a foot long flame
I don't think it's good for the car however

Your 100% correct.

[shep]

steknig wrote:

Jccck wrote:

che_guitarra wrote:

A flamethrowing exhaust would be just the ticket!!! I want one, I want one now!! Perfect for the arsehole tailgater.

Mine can do that, haha

Drive along at about 50, turn the car off in neutral.. Keep your foot flat to the carpet for 5-10 seconds, turn it on with your foot still flat!

Booooom, with a foot long flame
I don't think it's good for the car however

Your 100% correct.

yeah key bangers are best done in other peoples cars.

[Gwagensteve]

I think the collector size on the extractors is a clue to the ideal exhaust size. I think for most suzuki extractors it's 2".

It's funny how the myth of small diameter exhaust building torque never really goes away. It's partially true for stock "log" manifolds (and I say partially true because manufacturers are quite good at making cat manifolds that flow these days - have a look at the G16A exhaust - by using twin engine pipes, suzuki effectively created a tuned length extractor stock- shame the manifolds crack), but for tuned-length extractors (and turbos) it's false. The optimum backpressure for exhaust scavenging has already been achieved at the extractors collector. (That's why they are called "extractors". Downstream of the collector, no amount of additional backpressure is an advantage.

If you have a 2" exhaust that's too noisy it's not because the pipe is too big, it's because you don't have enough muffler.

I've built loud and quiet exhausts - I built a system for a G13BB engined Sierra with mandrel bent extractors, 2" all the way with a 3" tailpipe and it's just amazingly quiet - it has a triple flow muffler in it and two hot dogs to take out resonance. It's half as loud as legally permitted. At idle, the loudest sound is the injectors ticking.

I'd normally recommend a triple flow muffler and one 12" hot dog (with a cat) Th car will have a nice note under full throttle, but won't drone or resonate.

My own 660 car runs a cat, and triple flow muffler, but it's 2.25" and is very short- dumping behind the cab. It's too loud - not helped by the fact the 660 is always on boost so it sounds like it's working hard.

Steve.

[MacDaddy]

Gwagensteve wrote:

I think the collector size on the extractors is a clue to the ideal exhaust size. I think for most suzuki extractors it's 2".

It's funny how the myth of small diameter exhaust building torque never really goes away. It's partially true for stock "log" manifolds (and I say partially true because manufacturers are quite good at making cat manifolds that flow these days - have a look at the G16A exhaust - by using twin engine pipes, suzuki effectively created a tuned length extractor stock- shame the manifolds crack), but for tuned-length extractors (and turbos) it's false. The optimum backpressure for exhaust scavenging has already been achieved at the extractors collector. (That's why they are called "extractors". Downstream of the collector, no amount of additional backpressure is an advantage.

If you have a 2" exhaust that's too noisy it's not because the pipe is too big, it's because you don't have enough muffler.

I've built loud and quiet exhausts - I built a system for a G13BB engined Sierra with mandrel bent extractors, 2" all the way with a 3" tailpipe and it's just amazingly quiet - it has a triple flow muffler in it and two hot dogs to take out resonance. It's half as loud as legally permitted. At idle, the loudest sound is the injectors ticking.

I'd normally recommend a triple flow muffler and one 12" hot dog (with a cat) Th car will have a nice note under full throttle, but won't drone or resonate.

My own 660 car runs a cat, and triple flow muffler, but it's 2.25" and is very short- dumping behind the cab. It's too loud - not helped by the fact the 660 is always on boost so it sounds like it's working hard.

Steve.

X 1000

[Che]

I've seen Sierra extractors available on Ebay alone with both 2 and 2.25 inch collector measurements. The set of extractors I have at home measure 1.75 inch... seems like too great a range of variation for them all to be optimal design for the same 1.3L engine.

So how to distinguish between extractor brands designed for performance, and those bung together with the surplus bits of pipe in the back the shop without any proper testing?


Maybe i'm not understanding this concept properly, but surely 1/2 an inch in variation in collector sizes (assumuing a matching exhaust size) will lead to massively different performance outcomes?

[ball]

che_guitarra wrote:

I've seen Sierra extractors available on Ebay alone with both 2 and 2.25 inch collector measurements. The set of extractors I have at home measure 1.75 inch... seems like too great a range of variation for them all to be optimal design for the same 1.3L engine.

So how to distinguish between extractor brands designed for performance, and those bung together with the surplus bits of pipe in the back the shop without any proper testing?


Maybe i'm not understanding this concept properly, but surely 1/2 an inch in variation in collector sizes (assumuing a matching exhaust size) will lead to massively different performance outcomes?

Optimal design for what purpose,

what you need for low down power isn't the same as what is needed to get power higher up in the rev range.

What you want to achieve with your engine might be different to what others want.

[MacDaddy]

ball wrote:

che_guitarra wrote:

I've seen Sierra extractors available on Ebay alone with both 2 and 2.25 inch collector measurements. The set of extractors I have at home measure 1.75 inch... seems like too great a range of variation for them all to be optimal design for the same 1.3L engine.

So how to distinguish between extractor brands designed for performance, and those bung together with the surplus bits of pipe in the back the shop without any proper testing?


Maybe i'm not understanding this concept properly, but surely 1/2 an inch in variation in collector sizes (assumuing a matching exhaust size) will lead to massively different performance outcomes?

Optimal design for what purpose,

what you need for low down power isn't the same as what is needed to get power higher up in the rev range.

What you want to achieve with your engine might be different to what others want.

Yep i agree...
From what i understand, in a generalization -
A smaller 1.5in will give you more torque at lower RPM's...
A medium 1.75in will give you some torque at low, med and high rpm...
And a big 2in will give you alot of torque at high RPM...
But if you go to big, like 2.5in, you get a low exhaust pressure and you loose the scavenging effect, and loose engine torque and performance....

Correct me if i am wrong...

[Zook_Fan]

shep wrote:

i rev mine until it wont rev any harder. i have seen mad kennys taco go past
the numbers and it is the sweetest running sierra that i have seen.

yeah mine went past the guage while playing in sand once or twice on the stock exhuast. now it has extractors with a 2 inch outlet, into a cat with a 1 3/4 outlet to the muffler with 2inch in and outlet then the pipe out the back is 2inch. it sounds alright, not overly loud but it has stopped all the rattles of broken mounts from the stock exhaust so in my eyes its the best thing ever.

[ball]

MacBear wrote:

Yep i agree...
From what i understand, in a generalization -
A smaller 1.5in will give you more torque at lower RPM's...
A medium 1.75in will give you some torque at low, med and high rpm...
And a big 2in will give you alot of torque at high RPM...
But if you go to big, like 2.5in, you get a low exhaust pressure and you loose the scavenging effect, and loose engine torque and performance....

Correct me if i am wrong...

The big thing people forget or don't realise is that all the parts from the air filter to the tail pipe have to complement each other.

It is no good putting an exhaust on that has been designed for maximum economy OR maximum power when the rest of the engine isn't optimised for it.

Just mixing and fitting parts at random never really works as well as a correctly designed system.

[foonji]

I don't know a thing about this and won't claim to, but I find it funny how everyone has a different approach on the topic and some to extremes of the other.