GU Exhaust

Submitted: Thursday, Jan 19, 2006 at 23:01
ThreadID: 29897 Views:2759 Replies:10 FollowUps:12
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Has anyone fitted a 3"exhaust to a GU Patrol 4.2 T . is there a noticable increase in performance and what was the cost? Can you recommend an exhaust place in Melb Thanks Stan
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Reply By: Member - Trevor R (QLD) - Thursday, Jan 19, 2006 at 23:06

Thursday, Jan 19, 2006 at 23:06
Big difference Stan. Mine cost about $700 off memory (5 yrs ago) but money well spent. From Brissy so can't help with the second part of your question.
Careful though as you may not want to stop at the exhaust mod and it gets REALLY expensive after this hahaha.
Cheers Trevor.
AnswerID: 149738

Follow Up By: STAN - Thursday, Jan 19, 2006 at 23:15

Thursday, Jan 19, 2006 at 23:15
Thanks Trevor Thats about the figure I had in mind. Then there is the LPG conversion[ if the minister for finance agrees] Cheers Stan
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Follow Up By: Member - Trevor R (QLD) - Thursday, Jan 19, 2006 at 23:27

Thursday, Jan 19, 2006 at 23:27
Stan..... LPG conversion to a diesel?, tell me more.
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Follow Up By: Member - Pezza (QLD) - Friday, Jan 20, 2006 at 07:58

Friday, Jan 20, 2006 at 07:58
I'll bring the latest copy of 4wd monthly with me next week, they installed a kit into the troopy, gives power increase results, and a big write-up, you can read all about it.

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Follow Up By: Member - JohnR (Vic)&Moses - Friday, Jan 20, 2006 at 21:06

Friday, Jan 20, 2006 at 21:06
On the gas conversion front. I am aware of a tanker fleet that has had some complete tanker conversions to gas and no diesel at all. There have been some costly repairs I believe. I am glad it wasn't a fleet close to me ;-)

It does sound interesting to put in gas to a diesel to give the boost on hills and the like even for mechanical pumps like Nissan 4.2s to give better burning and a cleaner exhaust - and for Roachie to drop his engine temperatures too I imagine. Head winds with that Ultimate and over the 100 kph in South Aussie.
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Reply By: Member - JohnR (Vic)&Moses - Thursday, Jan 19, 2006 at 23:25

Thursday, Jan 19, 2006 at 23:25
Stan I guess you are talking about the 4.2 diesel and you will find a few comments over the last few months about them. You can take short cuts and fit the exhaust from the dump pipe, but you will be better off doing straight from the turbo - including the dump pipe - a 90 degree bend that is very restrictive out of the back of the Nissan turbo. You will find it is partly blanking off the exhaust port there.

I found a 16% lower 0 -> 100kph time after fitting it with Moses as heavy, I thought that was good. Beaudesert Exhaust Systems advertise in the 4by mags.
AnswerID: 149739

Reply By: STAN - Thursday, Jan 19, 2006 at 23:44

Thursday, Jan 19, 2006 at 23:44
Thanks John that was good info.
Trevor You can inject LPG into the inlet manifold of a Diesel . and get a 20% increase in HP TORQUE AND ECONOMY it is claimed to get a 98%burn with lower EGT The conversion is computer contolled It has a 30l LPG tank which should last for the main and aux tanks of dist. If you should run out of Lpg it just reverts back to the same old diesel. Cost about $3900 Cheers Stan
AnswerID: 149743

Follow Up By: Grungle - Friday, Jan 20, 2006 at 10:21

Friday, Jan 20, 2006 at 10:21
The price varies wildly depending on where you are. Up here in gods country there is a mob in Brisbane that do it for $3000 and a mob on the Sunshine Coast that do it for $2000. The latter is with a 36L tank. LPG is used at a rate of a 1 part LPG to 3 parts diesel so that 30 litres of LPG will service around 90 litres of diesel. You can switch it on or off but who would want to with the gains you get in fuel economy and power.

You can also import your own kit (minus tank) from the states and have a qualified gas fitter install it for you. Product is called the Powershot 2000 and costs around $1000 Aussie

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Reply By: Member - Pezza (QLD) - Friday, Jan 20, 2006 at 08:02

Friday, Jan 20, 2006 at 08:02
G'day Stan,
Have a look at post 29460 for more info.

AnswerID: 149776

Reply By: desert - Friday, Jan 20, 2006 at 08:30

Friday, Jan 20, 2006 at 08:30
Certainly, changing the entire exhauat system will give you are noticable lift in performance and decrease in fuel consumption. A 2.5" diameter mandrel system is all you need, with a 2.5" "turbo" type muffler and do away with the resonator if you so desire. This is for a standard 4.2T, with no mods to either fuel settings or waste-gate control.
If you have had mods done to the fuel or turbo, then you will also benefit from the larger dump-pipe at the back of the turbo.
A 3" exhaust is NOT worth the extra expense or weight penalty over the 2.5 UNLESS YOU ARE RUNNING GREATER THAN 12psi boost.
I have done all of these mods in steps and have recorded the comparitive results against each one, and the above is how it all washes up.
Try Pascoe Exhaust in Gaffney St.Coburg, they did all the fabrication work for mine and the 3" system worked out at $500 fitted.
AnswerID: 149783

Follow Up By: Member - JohnR (Vic)&Moses - Friday, Jan 20, 2006 at 17:02

Friday, Jan 20, 2006 at 17:02
desert if you had seen the really crappy Nissan dump pipe from the turbo I think you would have rethought your advice. I have one hanging on the wall of the garage and it is really restrictive. I have heard of people that don't replace the dump pipe to show little benefit from the replacement of the original exhaust.
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Follow Up By: desert - Friday, Jan 20, 2006 at 18:32

Friday, Jan 20, 2006 at 18:32
Quite the opposite, JohnR. The biggest percentage difference in horsepower was changing the exhaust to the 2.5. Then I changed the dump pipe, which is as you say, quite restrictive, then I went to the 3" pipes. The old dump pipe internal diameter is about 1.9 inch dia and new one is 2.25" dia. However, due to my modified fuel spool in the boost compensator, the turbo now actually cavitates and I put this down to the relative small wheels pushing gases into a large phlenum, ie the dump pipe. The next logical step is to change the turbine wheels for larger ones, a mod that MTQ specialise in.
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Follow Up By: Member - JohnR (Vic)&Moses - Friday, Jan 20, 2006 at 19:00

Friday, Jan 20, 2006 at 19:00
Interesting you say "about 1.9 inch dia" I actully measured it two ways to 1.7 inch diameter but also with a protrusion for the heat shield, though that doesn't reduce it much. I agree with the thought of using the 8mm increase in diameter of the compressor wheel if you want to go that way and increase your fuel supply.

I must say when I saw the Nissan OE dump pipe I was shocked at the restriction.

How much did you modify your fuel spool. Was it just by turning? Did you use an exhaust gas analyser, a dyno or a drive around?
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Follow Up By: Member - Roachie (SA) - Saturday, Jan 21, 2006 at 12:32

Saturday, Jan 21, 2006 at 12:32
I'm so sure that the next logical step (as stated by desert, above) is to get the MTQ upgrade done. I spent about the same $$$ and got a whole new, significantly larger Schwitzer turbo fitted by Denco Diesel (their agent, Berri Diesel service in the Riverland area of SA actually did the instal).
This was after I'd had the 3" mandrel bent system and a Glen Binskin dump pipe fitted a couple of years earlier.
The differnce with the new exhaust was mostly noticeable down low in the rev range, with more initial power at take off and when slogging through sand etc.
The new turbo fitted a couple of months ago, gives better power and engine response right through the rev range.
However, I tend to agree with something Truckster said on one of these posts (about 3" mandrel exhausts systems) a few weeks ago......we are not driving high performance vehicles like race cars etc.....and you'd probably get just as good result by fitting a 3" capstan-bent system. The slight decrease in diameter of the tubing at the bends would be of little consequence. In fact, when I was getting the bigger turbo fitted, they were a bit acdc about the 3" system; they normally only instal 2.5" systems on their turbos and reckon 3" is overkill.
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Follow Up By: Member - JohnR (Vic)&Moses - Saturday, Jan 21, 2006 at 23:43

Saturday, Jan 21, 2006 at 23:43
Bill, I guess if you need all the tuned figures you spend thousands on the development otherwise you do as we do and accept a lot of what we hear and see. It then leaves room for sales of Fitch and Hiclones for their followers. :-[

The difference between 2.5", 2.75" or 3" can only be judged if you do all the development. I don't know if I will put on a bigger turbo wheel yet but the Nissan now goes a lot better on hills, at the lights and lugs heaps better and with the larger exhaust ready for any further development rather than judge I need a bigger exhaust because I didn't put a big enough one on the first time. I prefer to spend once. I am not going to spend many thousands on Moses development. Have plenty of other things to do.

It was interesting that the local garage that have heaps of Nissans through were ambivolent about a 3" system as others had said little response. They others had left the original dump pipe as proscribed by desert above. I think the photos below are enough of an eye opener to anyone about the restriction built in. The turbo breathes more easily NOW.
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Reply By: Member - JohnR (Vic)&Moses - Friday, Jan 20, 2006 at 18:51

Friday, Jan 20, 2006 at 18:51
Stan it seems that no one really unerstands how restrictive the Nissan OE dump pipe is so here are a couple of photographs. The first one is of the exhaust end out of the turbo where the gasket marks the turbo actual outlet and the flat area around it where the dump pipe actually blanks it off. The measure across is in mm but for ease of comparison afterwards I will show the effective diameter for the exhausting of gas.
<img src=""

The other picture is of the end out to the exhaust pipe. The outside ring once again is the gasket for the outlet pipe at 3" ready to adapt into the 3" exhaust system. If you look beyond the open end you can see the effective diameter of the pipe is 1 3/4" so not even 2" I measured it with a washer on my finger.
<img src=""
The calculations for area are pi times radius squared
For the original pipe the effective volumertic area is 2.42 inches squared.
With the dump pipe for a 3" Beaudesert system the effective volumetric area is close to 7 square inches but say at 6 square inches as there are some areas that are compressed away from a circle. In any way, the capacity of the dump pipe is at least twice the Nissan OE dump pipe.

In both cases the original gaskets are used in both joins but showing up the poor original restrictive dump pipe.
AnswerID: 149891

Follow Up By: Member - JohnR (Vic)&Moses - Friday, Jan 20, 2006 at 21:01

Friday, Jan 20, 2006 at 21:01
That should be in the old language 2.42 square inches of the outlet of the original equipment dump pipe and over 6 square inches of the 3" fabricated one. The fabricated one has about 2.5 times the capacity to carry exhaust gas. Guess which one can allow the engine to rev better?
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Reply By: gqpat - Saturday, Jan 21, 2006 at 12:11

Saturday, Jan 21, 2006 at 12:11
Hi Stan try USA exhaust in Thomastown speak to Tony Martin does a fantastic job may not be the cheapest but if youy want a good job hes the man .
RE performance exhaust -wouldnt use them as they fit crap have a feel of the mufflers they will use the outer wall is really thin rust out in no time did a job for me years ago wasnt happy..
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Reply By: GOB & denny vic member - Saturday, Jan 21, 2006 at 18:51

Saturday, Jan 21, 2006 at 18:51
goodday stan
where are you in melb
i got trufit in warragul rd cheltenham to do mine have still got to get it redynoed

AnswerID: 150039

Reply By: STAN - Saturday, Jan 21, 2006 at 22:03

Saturday, Jan 21, 2006 at 22:03
Hi Fellas Thanks for the excellent advice. The minister for finance has approved the purchase of the gas conversion and this includes the 3" mandrel exhaust . Getting iit fitted next week Will keep you informed of the results STAN
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Follow Up By: Member - JohnR (Vic)&Moses - Sunday, Jan 22, 2006 at 17:45

Sunday, Jan 22, 2006 at 17:45
Well lobbied Stan. When do we put in for our percentage and to whom?
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Reply By: STAN - Sunday, Jan 22, 2006 at 21:07

Sunday, Jan 22, 2006 at 21:07
SSHH John I am not counting my chickens before they hatch
Funny cattle these women !!! Stan
AnswerID: 150196

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