[Mike57]

I just introduced myself in the new members thread a few minutes ago and this is my first real post.

I know that exhaust systems have been covered a lot in the past and my search brought up 50 pages of posts about exhausts but I have not found the info that I am after. I have a few questions that I am hoping someone can give me some advice on.

I have a 2009 VVt Jimny and would like to squeeze a little better performance and hopefully slightly better fuel economy out of it after fitting the 215/15 mud terrains both have suffered a little. I figure the place to start is with a better exhaust system.

I have got one quote for $1,200 which seems high. Now the $1,200 included ceramic coated 4:2:1 extractors, flow through cat convertor, 2" pipes a sports muffler plus a resonator.

My questions are:
1. How important is it to have ceramic coated ecxtractors
2. Has anyone managed to fit the mufler somewhere other than the back end of the car possibly freeing up space underneath for an extra fuel tank
3. I saw a post from Zukenutter a while ago where he suggested just fitting extractors to the standard exhaust as a first step to maintain the back pressure. I am curious about whether a full flo through exhaust will actually reduce torque due to lowering back pressure
4. What experience do other members have with respect to power, torque and fuel economy after an exhaust upgrade.
5. What should I expect to pay

Thanks for any info that can be offered.

Mike

[woo603]

Hey Mike,

I can try answer your questions as i had ceramic coated extractors on an old car
1) they look cooler but they idea behind them is that they don't radiate as much heat(in theory leading to a cooler engine bay) don't really know by how much or by what percentage but that is what they sales line is.

2) no idea
3)see here http://www.max-boost.co.uk/max-boost/ex ... xhaust.htm
4) cant talk for a jimny but my old car pick up was a little better and sound was great with a full tuned system. Didn't notice to much with economy.
5) do the ring around get as many quotes as you can then try and bargain, being from Melbourne you have access to A LOT of performance shops that will help you/inform you of the right way to go.

Hope this helps

[Mike57]

Thanks for the info especially the link. This is quite a complex subject. It seems like you can drop low end torque if you are not careful. I guess the trick is to ask lots of questions from the exhaust shops. I can see a whole lot more research coming up before I make the inverstment.

[jimny_timmy]

Hey mike, I just got my exhaust done with 2" system plus extractors... Used the factory cat and all upitcost me around $600... I also asked a few guys about moving the muffler to do exactly as you mentioned, one guy said he could put a smaller muffler under the passenger side, but it would be effin loud! Genie wildcat extractors should be around the$330 markand then the exhaust system aroundthe same depending onwhetheryou go full sports etc.

As for power/fuel consumption gains/losses... If anything I think I gained a little torque, although I have no proof of this, It definitely handles the beach driving a he'll of alot better... I added about 150kgs of weight atthe same time as getting it done through adding a bulbar, winch and storage system, so I can't really give you an idea of consumption, but I'm still getting about the same economy as before the system and the weight addition


Hope this helps a little and welcome to AZ mate!

[Mike57]

Thanks for the welcome and the extra info.

I have added a little less weight than you have so far but I have added a little over 1.0 L/100km to the fuel consumption. We went on a few test runs up the hume freeway before and after so we had a direct comparison. Some of that is a virtual gain just from having bigger tyres that is about half of it or 0.5 l/100km according to my calcs. I think much of the rest of it is due to the increased rolling resistance of the mud terrains. I have not been able to find any exact figures for the difference in rolling resistance but I think it is significant. Since we did long runs at an even speed I don't think the extra weight would have had a lot of influence, that would affect stop start city driving a lot though.

The issue I have found is that it really lacks torque at the low end going up hills with the bigger tyres. Although I did not go overboard it has made a difference so I was looking at the exhaust to get some of that back like I mentioned earlier.

The other possibility is to chip it but that opens up a whole lot of other issues and is an even more complex area.

Cheers

[jimny_timmy]

You'll find with an exhaust system that it will help you hold speed a little better on hills, but at the end of the day it's a zook mate lol. We all have the same problem and there's very little we can do about it!

[Mike57]

Yep but its still the most fun to drive of any car I have ever owned.

[jimny_timmy]

Hell yes!

[smiffkid]

i payed 350 for extractors 2 inch pipe and a muffler on mine, and a hotdog instead of a cat, sounds good and works well

[Fatzook]

smiffkid wrote:

i payed 350 for extractors 2 inch pipe and a muffler on mine, and a hotdog instead of a cat, sounds good and works well

You are an idiot for posting that on a public forum.

Mike,
Not sure what the factory pipe size is on a jimny ( maybe 1.75"?) But if you want a performance gain without the loss of low rpm torque and excessive noise, you can always get a mandrel bent system made in the same size as OEM exhaust tube. The idea is to gain flow by eliminating the 'crushed' press bends that all factory systems have. You can then fit a more compact muffler and not be in fear of it being really loud.

I just went through this with my Vitara. I fitted extractors, a new cat, and made the system from 2" ( same as standard) stainless steel with mandrel bends to maintain gas flow through the bends. I fitted a offset, non-chambered muffler ( essentially straight through ) and a resonator. End result is a small but noticable gain in power/ torque, with a nice sporty note, but without the volume! And as a bonus it does not seem to 'drone' on the highway either.

My 2 cents.

[Mike57]

I will definitely be keeping the cat but the idea of mandrel bends is useful. I am pretty sure the original has crushed bends as you say. What I have been quoted so far is pretty much the same as what Fatzook has except I will need to check on the bends and do some shopping around.

[Fatzook]

A mandrel bent system will be dearer than the normal press bent system.

Another thing to note with press bent systems is that the flow of the system is only as good as the most restrictive part. So if you upgrade to a 2" press bent system, and there is a 70 or 80 degree bend in there to get up over the rear diff housing, you can almost guarantee that the cross sectional flow of the pipe through that bend will be reduced to that of your OEM system.... or worse. And having the pipe open out to a larger diamter after the crushed bend actually creates a sort of resonance chamber. This some times makes the system drone.

[royce]

Fatzook wrote:

A mandrel bent system will be dearer than the normal press bent system.

Another thing to note with press bent systems is that the flow of the system is only as good as the most restrictive part. So if you upgrade to a 2" press bent system, and there is a 70 or 80 degree bend in there to get up over the rear diff housing, you can almost guarantee that the cross sectional flow of the pipe through that bend will be reduced to that of your OEM system.... or worse. And having the pipe open out to a larger diamter after the crushed bend actually creates a sort of resonance chamber. This some times makes the system drone.

Youll also find the actual change in the tube shape from the crushing will do really stupid things to interrupt the flow that work out to be worse than an equiv piece of smaller tube of smaller diameter.

If you have a budget ignore the extractors as the stock manifold is probably pretty good and will also be a lot quieter and pay attention to quality well designed mufflers

[barrybanks]

some information here for you on exhaust upgrades

www.jimny-crew.com/jimny-on-the-dyno.html

www.jimny-crew.com/exhaust-upgrade-dyno-results.html

my mechanics opinion is that without additional performance work on the head, extractors alone won't make any gains

cheers

[Fatzook]

barrybanks wrote:

my mechanics opinion is that without additional performance work on the head, extractors alone won't make any gains

cheers

Its felt in the seat of the pants , but you are right to a point. Most modern NEW cars will have manifolds that flow well enough.

[dave91]

Fatzook wrote:

smiffkid wrote:

i payed 350 for extractors 2 inch pipe and a muffler on mine, and a hotdog instead of a cat, sounds good and works well

You are an idiot for posting that on a public forum.

Why's that? What's a hot dog?

[Mike57]

Barry, that was very useful info and supports the comment from Royce to leave the stock manifold on. Don't know how you found this one I have done heaps of searches and not stumbled on it. Many thanks.

[Fatzook]

dave91 wrote:

Fatzook wrote:

smiffkid wrote:

i payed 350 for extractors 2 inch pipe and a muffler on mine, and a hotdog instead of a cat, sounds good and works well

You are an idiot for posting that on a public forum.

Why's that? What's a hot dog?

A hotdog is just a resonator.

But he is an idiot because he has openly admitted to removing an emmissions control device ( catalytic converter) from a vehicle that is legally required to have one. Fines of up to $250,000.00 for doing so.

[squibby]

I just got quoted $550 fitted for a 2 inch performance system. This included a performance Catylitic convertor. The bloke who quoted says he's done a jimny before, and he ended up adding an extra resonator above and beyond what the stock jimny has because he says it sounds terrible without it. My quote includes this. I can get a performance 4:1 header off ebay for about $200. I'll fit that myself because there's plenty of access to a Jimny headers so it looks easy, so that'll be about $800 all in including fitting and sundries for a full header/performance Cat and 2 inch system. Thats' in Newcastle.

Throw in a K&N filter and a snorkel to help it all breath better and I reckon thats' about the most you can get out of a 1.3 VVT jimny without forced induction. No point messing with cams, it's got variable timing already.

[Santos]

Mandrel bend exhaust are made in two ways.

1) people have the expensive machine and bend it out of one piece
2) people buy a lot of mandrel bends and cut and weld it all together


Upgrading the factory system as fatzook described is on my to do list as the sierra pipe seems to go from 1 3/4" in front of the cat converter down to 1 1/4" from memory by the time it leaves the tailpipe

[JrZook]

Santos wrote:

Mandrel bend exhaust are made in two ways.

1) people have the expensive machine and bend it out of one piece
2) people buy a lot of mandrel bends and cut and weld it all together


Upgrading the factory system as fatzook described is on my to do list as the sierra pipe seems to go from 1 3/4" in front of the cat converter down to 1 1/4" from memory by the time it leaves the tailpipe

There is some reasoning behind this. It all has to do with keeping the gas velocity high without creating excessive backpressure.

When the exhaust exits the the engine I use an estimated max temp of around 550C. With the higher temp the gasses also move at higher velocities thus the pipe should be larger close to the source. Once the gas exits the tailpipe, the temp will have dropped significantly to around ~150C.

Thus if the velocity is kept constant but the temperature is decreasing the pipe size must also decrease to keep the velocity up.

Well that's my understanding of it.

[squibby]

Just a quickie for those who understand exhausts more, because I haven't got a clue. Obviously you reduce back pressure and I guess you make more power. Whats the trade off? surely you must loose out somewhere? I know some cars when fitted with rediculously large exhausts are hard to start.

[Fatzook]

For a non-turbo car, a freer flowing exhaust will usually rob a little low rpm torque. But you gain some higher in the rev range.

As for making them hard to start......never heard that before

[Santos]

good point jrzook, the cooler gas would travel slower in the larger pipe

i think this is one of the theories why to thermalwrap/ceramic coat the exhaust system. By keeping the internal temperatue constant the gas flow stays the same.

Squibby check out all the exhaust articles at autospeed.com.au
they are pretty good and the author does a lot of realworld testing on both petrol and diesel engines.

One of the most interesting things i learnt was diesel engines exhaust gases are considerably cooler than petrol engines and how it effected the exhaust noise when running without a muffler.

[squibby]

Fatzook wrote:

For a non-turbo car, a freer flowing exhaust will usually rob a little low rpm torque. But you gain some higher in the rev range.

As for making them hard to start......never heard that before

Ok, It's true though about the starting. I bought a car once from a wreckers that ran like crap. I knew it had a leaking downpipe. Got the new exhaust on and it ran perfect again. You can go too big, or too free flowing for everyday road use

[JrZook]

squibby wrote:

Just a quickie for those who understand exhausts more, because I haven't got a clue. Obviously you reduce back pressure and I guess you make more power. Whats the trade off? surely you must loose out somewhere? I know some cars when fitted with rediculously large exhausts are hard to start.

The trade off is you reduce the flow velocity and will not get scavenging effects through the head (volumetric efficiency). The idea for a good exhaust system is to have minimal back-pressure but maximize flow velocity.

Of course the flow velocity depends on the engine flow which changes with RPM thus a single fixed exhaust can only target a specific RPM.

[Mike57]

I spoke to one of my mates today, he is a mechanical engineer and worked for GM for a while. His view was that you need some back pressure and without it you will rob all the low end torque and the engine will simply run like a dog. A totally free flowing exhaust like an open pipe would not be a good idea unless the engine was especially set up for it.

His opinion was that the extractors must go from 4 to 2 to 1 pipe to maintain the torque. He also thought that most of the rapid cooling happened between the head and the end of the extractors and that was why it was important to have the 4:2:1 configuration. Just another view I guess.

Oh and he definitely said not to be too worried about the kW - it is the torque which pulls you up the hills and through the sand and not the power output.