big exhaust on gq shorty

[matto]

Question? I have a 4.2 diesel shorty has anyone put extractors or an exhaust system on theirs? was there any power increase? does it sound cool?

[Daisy]

4.2 diesel engines - ive heard people say that extractors have given the car bugger all power increase... and you're better off savin up for a turbo setup as its only a quarter of the cost of the exhaust.. so may as well keep on saving...

to give you an idea.. a GU factory turbo setup is a straight bolt up to a GQ with some mods to water and oil lines, and they can be had cheap.

THEN fit a nice fat 3 inch pipe behind it

[mickyd555]

sounds cool, very loud if ya get a good muffler. dont expect more than about 2% power increase. but fuel economy is a little bit better. but you do lose a little bit of compression braking.

[matto]

the reason i ask about the power increase is because i can get the whole system extractors and all fitted for $550 or just a bigger pipe for $220 i'm really after just the sound and to reduce the size of the muffler if have one at all.

[coke]

mickey,

how the hell did you work out that it gave you a 2% power increase? I mean, lets assume you got a good one and it made 75kw on the dyno. Plus 2% is 76.5kw. That could be had with change in air intake temp.

I am assuming that you are guessing when youu say that then...

I have a mate that fitted a 2.5" straight thru system with extractors onto his 94GQ, and it went a fair bit better than stock, with better economy too. Only issue was it droned at 80-110. I couldn't stand it personally.

I have a 3" system straight thru on my GQ with turbo. It made a fair difference to the seat of the pants o-meter and gives a great note. Original system was 2.25 on my car.

Andrew

[mickyd555]

mickey,

how the hell did you work out that it gave you a 2% power increase? I mean, lets assume you got a good one and it made 75kw on the dyno. Plus 2% is 76.5kw. That could be had with change in air intake temp.

I am assuming that you are guessing when youu say that then...

I have a mate that fitted a 2.5" straight thru system with extractors onto his 94GQ, and it went a fair bit better than stock, with better economy too. Only issue was it droned at 80-110. I couldn't stand it personally.

I have a 3" system straight thru on my GQ with turbo. It made a fair difference to the seat of the pants o-meter and gives a great note. Original system was 2.25 on my car.

Andrew

i didnt work it out, i was simply saying expect f***k all power increase. it may be as much as 10 or 15 % i dont really know. but it certainly doesnt turn ya truck into a speedway demon....... i am happy with my extractors, and thanks to a little deal i did they cost me SFA. if ya gonna get them make sure there mandrel bent extractors and a mandrel bent custom exhaust would be good too. on my ute, the way the exhaust pipe was run it is preety well straight with minimal restriction, but i dont know how youd go on a shorty.......you have to see it to understand what i mean, ill see if i can get some pics

[matto]

Coke do you think its worth the extra money for the extractors?

[mickyd555]

Coke do you think its worth the extra money for the extractors?

see my post above about the mandrel bender

[matto]

mickey,
If you dont mind me asking where did you go and what price are we talking about

[mickyd555]

mickey,
If you dont mind me asking where did you go and what price are we talking about

mine was done at a midas outlet, the price they quoted me was about $700.00, for mandrel bent genie extractors and a 2.5" exhaust with a "sports" muffler. but i would rather a turbo with a 3" exhaust

[coke]

The extractors I mentioned were on my mates car. I would get them if that is the direction that I was heading (non-turbo) but I would put a hotdog in the system to shut it up a bit.

Agree with micky about the mandrels. I have a full mandrel system and it does make a difference. Even get mandrel bends if you are getting a 2.5" system. The small extra cost (maybe $100) is worth it. gases flow much better...

Andrew

[siklux]

i put on a set of extractors and 2.5 mandrel exhaust with one straight through muffler on my GQ swb, it sounded great, not too droney and made a marginal increase in power, but it could have been the tuff noise making is feel faster, it was a bees dick faster really. id just go the 2.5 system withone staight through muffler, and spend the other few hundred on some else, UHF,towards a locker, whatever. but its up to you of coarse

[GutSquisher Media]

Most engine builders would say the power increase would equate to about 1/2 a gear.

I use a program called Engine Analyser Pro and by changing the factory manifold with free flow headers with 2â€

[coke]

not much but when you are talking about a motor that produces 85Kw adding 3% is better than nothing.

I may be the only one here, but I don't necesarily agree with that. Dollar for kw value, you are far better putting a turbo on the car.

Outlaying $600 plus for 2kw is a waste. You would gain more than that by changing your gearbox and diff oil for some expensive gear (redline or similar) and regreasing everything with a good hitemp grease. I have seen oil changes with $100/4lt oil add up to 10kw atw in a WRX. You would be amazed what a good lube will do.

Oh, and also fit those wind deflectors to your front windows, and headlight covers. TIC

Andrew

[GutSquisher Media]

coke wake up and smell the roses, have you thought that he hasn’t got the $2500 to $3000 to send on a turbo.

Were not all as rich as you and some people need to think about what they can afford to spend.

[viperguy]

set ur motor up for straight gas, leave ur standard exhaust manifold unless cracked and get a 2 1/2 inch free flowing one muffler system. i have this but i have extractors too. get good tune done to suit straight gas and u will have a very healthy patrol..

if extractors and exhaust give 10% increase, the extractors will be worth only about 2 of that 10, with the exhaust being the rest. use the 350-400 u save to get a straight gas mixer and u will be more happier with the performance gains

[rOd]

set ur motor up for straight gas, leave ur standard exhaust manifold unless cracked and get a 2 1/2 inch free flowing one muffler system. i have this but i have extractors too. get good tune done to suit straight gas and u will have a very healthy patrol..

The lack off LPG availability in small towns makes straight gas a bit of a worry for me personally. Even if I rarely ever use petrol, its kind of an emergency fuel really.