2003 GU TD4.2 - looking for more Grunt

Submitted: Friday, Feb 02, 2007 at 16:42
ThreadID: 41902 Views:2930 Replies:8 FollowUps:8
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Hi All,

I have a 2003 GU TD4.2 and I am looking for more power - particularly from low revs.

Have done nothing to engine to date & from reading forums & archives, I beleive that the best place to start is a 3inch exhaust, including the dump pipe (whatever that is!) and a seriously good tune.

Am I way off track for a first engine mod?

Having opened up the exhaust, should I be looking to open up the air intake at the same time?

Recommendations for people in Melbourne who can do the fitting & tuning?

What should I be expecting to pay?

Closer to Sandringham the better, but a quality job is more important than a short drive!

Thanks & Regards

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Reply By: MEMBER - Darian (SA) - Friday, Feb 02, 2007 at 16:52

Friday, Feb 02, 2007 at 16:52
Roachie is at the front counter with a customer - he'll be here shortly :-0)
AnswerID: 219284

Reply By: MickO13 - Friday, Feb 02, 2007 at 17:01

Friday, Feb 02, 2007 at 17:01
Have a look here also. You'll find it a lot more specific to your vehicle and the amount of knowledge is amazing.


Cheers. Mick
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trip would doubtless be attended with much hardship.''
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AnswerID: 219287

Reply By: Truckster (Vic) - Friday, Feb 02, 2007 at 17:51

Friday, Feb 02, 2007 at 17:51
Whats your budget?

First place to call is Andy at DieselTech in Lillydale.. .bit of a journey, but worth it.

second would be Aaron at ATOC (check club maggo).. Bit of a journey but worth it.

Both will cost you round $1400-1600 for exhaust, pump mods, and a tune. AAron gives a good club discount :)

You can spend $5500 and get a ball bearing turbo, new manifold, the works from OnTrack and you can get around 180kw at the wheels.. Hes done quite a few now...

AnswerID: 219297

Follow Up By: Trevor R (QLD) - Friday, Feb 02, 2007 at 20:23

Friday, Feb 02, 2007 at 20:23
Those figures make the Chev option a no contest at that price don't you think?

Are they doing this for race comp trucks or daily drivers? and what k's would they (and you) expect from something running that finely tuned?

Interested on your opinion.
FollowupID: 479859

Follow Up By: Truckster (Vic) - Friday, Feb 02, 2007 at 22:28

Friday, Feb 02, 2007 at 22:28
Most are for comp trucks, OBC, Winch Challenge, Cliffhanger etc.... But he has done a few touring rigs..

If I had the coin, I'd book it in ASAP.

Any powerup will decrease the life of an engine to some extent,

I would think that this mod would - A lot would depend on how you drive it, if you use the 180kw all day yes it will wear out faster than stock... but if you drive it like normal, it wont be anywhere near as bad. But most that are interested in this mod, wouldnt be worried about klms, but HP.

FollowupID: 479889

Follow Up By: Pezza (Bris) - Saturday, Feb 03, 2007 at 11:10

Saturday, Feb 03, 2007 at 11:10
"Any powerup will decrease the life of an engine to some extent"

You mean you're only gonna get 600,000k's instead of 750,000 !! Bugger :-))))

FollowupID: 479961

Reply By: Member - Teabag (Queanbeyan) - Friday, Feb 02, 2007 at 18:24

Friday, Feb 02, 2007 at 18:24
I already had the 3in Exhaust and Dump which did make a difference though we are always looking for more. I had mine tuned today at Queanbeyan Diesel Services. What they found was boost was already between 9.5 and 10 PSi though timing was out, has the mechanic put it quite retarded in timing.....After getting the timing right and a test drive it now holds at least 10km better on hills, so I'm pretty happy with that.
The easiest mod is the 3in Mandrel Bent Exhaust with 3in Dump pipe and a good tune. You will be surprised at the difference. If you want more then your possibly looking at putting in a Boost Control Vv and getting the boost up to 12psi though this can present other problems such as higher EGT and can decrease the life of the engine. Or you can get a Turbo upgrade which will make it even better.....Good luck....
AnswerID: 219305

Reply By: Trevor R (QLD) - Friday, Feb 02, 2007 at 18:42

Friday, Feb 02, 2007 at 18:42
Truckster has provided good local info on guys down your way, you could also try MTQ (outlets in a lot of major cities so I imagine one down your way). The modification these guys do will change where max torque and power is on song till a bit later in the rev range but it is still a good outcome in my opinion but you may want different to me??

Starting with your exhaust mod is a good idea as any other mods will include the exhaust swap anyway so go for this and see if that is enough for you.

Happy motoring.
AnswerID: 219310

Follow Up By: Truckster (Vic) - Friday, Feb 02, 2007 at 22:29

Friday, Feb 02, 2007 at 22:29
Yup, MTQ are in Dandenong off Greens Road..

So are AXT in Dande, and Alan at Outback Accessories in Seaford is a Denco Agent.

We are lucky round here plenty to choose from :)
FollowupID: 479890

Follow Up By: Member - JohnR (Vic)&Moses - Saturday, Feb 03, 2007 at 08:02

Saturday, Feb 03, 2007 at 08:02
Trevor, Bruce should argue with you on that because he can buy the services of MTQ elsewhere at a lower price. Acting out of character that he hasn't..... ;-)
FollowupID: 479931

Follow Up By: Truckster (Vic) - Saturday, Feb 03, 2007 at 11:58

Saturday, Feb 03, 2007 at 11:58
You can John. As pointed above, Aaron does the same work as MTQ for 100's cheaper..
FollowupID: 479968

Reply By: raunchy - Friday, Feb 02, 2007 at 22:35

Friday, Feb 02, 2007 at 22:35
HI PGK, am a yota driver, with a chip and 3 inch exhaust on my 4.2 so nothing will compare.... AAnyway have a mate who has a GU 4.2TD 2001, has had all sorts done the the vehicle generally, but very impressed with the MTQ system. A mate with the 4500 80 series petrol, drove the ute and was impressed with the power. Id say spend the money and you will be happy.. MTQ are in Dandenong, Hammond Road from memeory

AnswerID: 219369

Reply By: Member - Roachie (SA) - Friday, Feb 02, 2007 at 23:27

Friday, Feb 02, 2007 at 23:27
The other blokes have already covered off on most of what I would have said with a couple of exceptions:

1). You asked what the dump pipe is........ It is the short, 90 degree, steel pipe that immediately exits the gases from the turbo into the exhaust system. Some places will make you up a new exhaust system that bolts onto the existing dump pipe. Waste of time and money! The dump pipe of the 4.2 Nissan motor is VERY restrictive and chokes the gases. That's why you need the whole system, including a free-flowing straight through exhaust and no need for the catalytic converter.

2). I would suggest you fit a EGT (exhaust gas temperature) gauge. If you get the new exhaust system, there should be a threaded lug in the new dump pipe that you can screw the probe (aka: thermocouple) into. This will provide you with valuable info about if you might be trying to extract too much from your donk. Treat 520oC as a "red line". You'll be surprised how changing down a gear (say when climbing a steep hill), will make the EGT drop, even though the engine is revving a bit more. You can choose from an anologue type meter, or (my preference) the digital readout one from Ian at Thermoguard (he's a sponsor/advertiser on this forum).

3). You mentioned about the intake side of the motor too. Glad you did as this is one area that nobody seems to have really concentrated on or (IMHO) "cracked", as far as I'm concerned. The Nissan air intake system leaves a LOT to be desired. The filter is too small (compare it to even the old 2.7 Prado!!!) and will not/cannot flow enough clean air through in the volumes required for this size motor. My new beast (it is a GU with a Chev 6.5 V8) has a huge Donaldson cleaner. Unfortunately for most owners, it takes up the whole area where most blokes like to mount their 2nd battery. I am lucky that with the dual cab conversion I can have my 2nd battery in the box on the back; which is where 90% of the gear that it runs lives anyway. At the very least you need to fit a snorkel so you get a bit of "ram" effect at speeds over 80k/h to assist force some air into the system. Some people also use free-flowing filters (eg: UniFilter/Finer Filter, K&N etc). I used to use a Unifilter and still believe they are probably okay for bitumen running, but they apparently let more dust particles through than the good old paper element type.

4). If you get the boost tweaked (or a Denco kit fitted like I did on my old 4.2), I would also suggest fitting a boost gauge. Mine used to push up to 15psi maximum boost, but I was always conscious of this and had the gauge there to let me know what I was pumping......I do not believe 15psi should be sustained for long periods of time. Read the boost gauge in conjunction with the EGT gauge and water temp gauge and you'll be sweet.

Hope this helps a bit....good luck and have fun; the 4.2 is a heavy old reliable donk.
AnswerID: 219380

Follow Up By: Member - JohnR (Vic)&Moses - Saturday, Feb 03, 2007 at 00:35

Saturday, Feb 03, 2007 at 00:35
Supporting Roachie's point on the restrictive nature of the dunp pipe. I measured the internal diameter off a 1.5" washer to be approximatley 1.7" for the flow. A 3" dump pibe will let it go far better...........
FollowupID: 479918

Follow Up By: Member - Teabag (Queanbeyan) - Saturday, Feb 03, 2007 at 10:28

Saturday, Feb 03, 2007 at 10:28
Has Roachie has eluded to wrt 15psi Boost, be very very careful and to be honest this sort of boost can and will reduce the longevity of the engine......Anything over 12psi can begin to cause overheating issues......It will all come down to how much extra get up and go that you want.....
FollowupID: 479956

Reply By: kiwicol - Sunday, Feb 04, 2007 at 13:05

Sunday, Feb 04, 2007 at 13:05
if your looking for low down power fit a super charger get rid of the turbo fit extractors 3 inch pipe and you will have more tourge in the lower revs, i have one fitted and at idle is putting out 8psi which a turbo doesnt do untill about 1800 revs grat for towing and the sloww drives through rough terrain they run their own oil are servicable and doent have the heat impact turbos do they pull nearly as hard as a chev diesal conversion only cheaper col
AnswerID: 219647

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