[BigRay]

Since cutting the rear muffler off of my G13bb Jimny and putting in a straight pipe (the torque improvement is amazing, and the sound) on engine braking the engine produces a loud fart, and sounds like a very loud Kenworth. Just wondering if extractors or a larger diameter exhaust system may help...

[pezz]

sounds like you need more restriction, not less..

[BigRay]

Hmmm, good idea but don't really want to go backwards as before removing the muffler I had serious engine bay temp problems, couldn't open the bonnet until the thing cooled down. Now runs nice and cool!

[Gwagensteve]

You have other problems if "cutting the muffler off" made the car run significantly cooler. Likewise, it should not make no discernible difference to torque.

Anyway, you need to replace the straight pipe with a muffler or resonator. I imagine it sounds terrible.

Steve.

[BigRay]

I love the sound, it has a nice growl to it, it's just the farting under engine braking that can sometimes be an issue. Torque improvement is amazing, I no longer have to shift at 4200rpm and can now shift at 3000 rpm, it happily cruises at 60km/h in 4th gear now aswell. No complaining and bogging in 1st and 2nd now also. I think the exhaust isn't flowing efficiently now though which is why extractors might help.

[Chop]

What size tyres are you running?

[BigRay]

Completely stock at the moment - 205/75 15

[Gwagensteve]

All due respect BigRay, but you're throwing a whole bunch of exhaust theory around, and your contradicting yourself. I'm not sure you really understand what's going on in your exhaust.

Pretty much all the restriction in your exhaust will be upstream of the catalytic converter. What happens another 1500mm downstream is going to have a very minimal effect. Years and years of dyno tests on countless cars have proven this, even with turbo cars with significantly increased power and therefore exhaust flow.

But in any case, if you are happy with the increased performance that's great. However, you're going to need to experiment with different resonators or mufflers to get the tone you want without the excessive noise on overrun.

You could invest in extractors and a replacement exhaust, but it's not going to change much- less muffler equals more noise.

Steve.

[royce]

youve probably got a leak further up

[BigRay]

I understand where you are coming from. Although, no matter where it is, cat or muffler (unless straight through), is going to cause exhaust restriction. I have simply removed a very tired and clogged up muffler and am now experiencing the benefits of an exhaust system with less back pressure and the performance improvements that come with it. Just wanted some opinions on how to make it a bit quieter.

[leafs4lyf]

BigRay wrote:

I understand where you are coming from. Although, no matter where it is, cat or muffler (unless straight through), is going to cause exhaust restriction. I have simply removed a very tired and clogged up muffler and am now experiencing the benefits of an exhaust system with less back pressure and the performance improvements that come with it. Just wanted some opinions on how to make it a bit quieter.

Gwagensteve wrote:

Anyway, you need to replace the straight pipe with a muffler or resonator.
Steve.

[BigRay]

Yeah I figured that!

[BigRay]

royce wrote:

youve probably got a leak further up

Thanks mate, makes sense to me, I'll check!

[zooky08]

Nearly every Jimmy has a hot engine bay and a hot bonnet. It's normal for the Jimmy's.

[Marko_SJ]

I'd put in a resi or hi sports muffler mate.

Must drone like mad.

Edit: look into hi flow cats too.

[Jezza86]

how bad is your engine breaking?

[BigRay]

Thanks I'll look into it


My engine braking is different to that, hard to explain!

Thanks for the replies!

[BigRay]

Jezza86 wrote:

how bad is your engine breaking?

What exhaust system are you running?

[alien]

royce wrote:

youve probably got a leak further up

I agree with this... mine's got a cracked weld on the engine side of where the exhaust meets the muffler and on engine braking it sounds woeful. I'm dying to get it welded back up but haven't had the time. I've also had a weld crack on the other side of the muffler and it made similar sounds but no where near as loud.

if you're worried about cost, many exhaust shops have a bin of mufflers they've taken off other vehicles who put sports systems etc on which are in perfectly good condition with hardly any mileage on them. If you're nice to them they may let you dig through this bin to find something that will work on your jimny.

The improvement you've noticed may be due to the fact that your muffler is 15years old and was buggered?

[BigRay]

Thanks mate! I agree with you too. But at the same time I'm not sure. If I lightly put my foot on the accelerator the farting goes. When stationary, if I blip the throttle, as the revs come back down is sounds as if it's sucking from the pipe, when engine braking it is very loud.

[alien]

Mines exactly the same with the crack in it.

[BigRay]

Well that's my next job, looking for a crack

[BigRay]

It was never noticeable before the exhaust modification

[Gwagensteve]

FFS you have no muffler. It's not a mystery.

Steve.

[BigRay]

Ok Steve.

[jimny_timmy]

I'm with Steve... You took the muffler off... It makes noise...

[31zook]

Gwagensteve wrote:

FFS... It's not a mystery.

Steve.

This is how I imagine steve reads most of the board.

[jimny_timmy]

[BigRay]

Gwagensteve wrote:

You have other problems if "cutting the muffler off" made the car run significantly cooler. Likewise, it should not make no discernible difference to torque.

Steve.

Turns there were other problems, got a new exhaust system today (high flow-straight through), turns out the cat was completely worn out and causing restriction, got even more torque now and the engine runs even cooler again!

[Skippy]

31zook wrote:

Gwagensteve wrote:

FFS... It's not a mystery.

Steve.

This is how I imagine steve reads most of the board.

Maybe if some of the simpletons on here listened to what Steve said for a change instead of arguing with him all the time, shit would get fixed faster / better!!