Patrol ZD30 what is better 2.5" or 3" exhaust?

Submitted: Thursday, May 17, 2007 at 17:55


I know, I know, it has been posted before, and I have done a search, but most responses are for the 4.2L.
I am after people who actually done the change and I like to know if there is any inprovement in performance enough to justify the cost.
I rang a few exhaust workshops and I can't get a straight answer, one is praising the 2.5" and another the 3" then you got straight trough without muffler or with muffler without cat, to be honest I am totally confused.
I also like to know if there is a exhaust specialist in western Sydney who knows what he is talking about re the 3l patrol.
Thanks for your reply.
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Reply By: On Patrol (Aust.) - Thursday, May 17, 2007 at 19:08

Thursday, May 17, 2007 at 19:08
In West Sydney, talk to Total Care 4WD 7 Hills

He has just removed my Cat converter and put in a straight through pipe with instant results in performance & fuel consumption.

This makes me think that my Cat Conv was on the way out, Jason suggested that the conversion really does make a difference.

Try talking to him. Jason. No bull shyte, just good advice.

Total Care 4wd
Un 1/ 13 Bearing Rd Seven Hills 2147
(02) 9838 9779
AnswerID: 240597

Follow Up By: Member - Troll 81 (QLD) - Thursday, May 17, 2007 at 20:17

Thursday, May 17, 2007 at 20:17

What do you mean? are you saying you don't have any cats? If that is the case be very carefull it's a $4000 fine if you get caught
FollowupID: 501537

Follow Up By: Wayne-o - Thursday, May 17, 2007 at 20:20

Thursday, May 17, 2007 at 20:20
me got no cats....
none on the stock system....none on the new system.....
but yes big fines...
FollowupID: 501539

Follow Up By: On Patrol (Aust.) - Thursday, May 17, 2007 at 20:44

Thursday, May 17, 2007 at 20:44
Assured that in NSW at least, that no catalytic converter is not illegal on a diesel motor????

Can anyone prove me wrong???

I hope not, as it's done now.
FollowupID: 501548

Follow Up By: gompy - Thursday, May 17, 2007 at 20:46

Thursday, May 17, 2007 at 20:46

What size did you put in, no muffler? lot of noise? how much did it cost you?
FollowupID: 501551

Follow Up By: Member - Troll 81 (QLD) - Thursday, May 17, 2007 at 21:02

Thursday, May 17, 2007 at 21:02
not sure about diesel but I know for petrol it is in QLD
FollowupID: 501556

Follow Up By: On Patrol (Aust.) - Friday, May 18, 2007 at 05:59

Friday, May 18, 2007 at 05:59
I only removed the Cat. Conv. to reduce the risk of brackdown for my Cape trip.
The system is otherwise std. the straight through pipe cat replacement was around $100-110?

Thats all folks, I've gone fishin. back in 6 weeks.
FollowupID: 501610

Follow Up By: On Patrol (Aust.) - Friday, May 18, 2007 at 16:48

Friday, May 18, 2007 at 16:48
I must apologise to you all and say that the pipe is NOT a straight through as I was first told, rather a modified hi flow unit.

Sorry if I inadvertently miss guided you all.

FollowupID: 501715

Reply By: Wayne-o - Thursday, May 17, 2007 at 20:17

Thursday, May 17, 2007 at 20:17
fitted 3" to the 4.2iTD, instant much better
beaudesert system. $1000
i fitted it myself, bit of skin off the knuckles but its worth it!
AnswerID: 240614

Reply By: Leroy - Thursday, May 17, 2007 at 20:52

Thursday, May 17, 2007 at 20:52
There was an exhaust guy on the outler limits forum and I called him up to have a chat. He recomended a 3" system with a hi flow cat and you didn't necessarily need a muffler. It was mandrel bent and cost around $1100 but that was becasue of the custom made hi flo cat. He has done them but hadn't recieved feed back on performance and I never got around to calling him back as I ended up with a DTronic. He's located in Croydon. I don't know for sure but if the vehicle had a cat then it has to retain it unlike the 4.2 that has no cat to begin with and he was keen and recommended to keep the vehicle legal.

AnswerID: 240633

Reply By: Member - Bucky (VIC) - Friday, May 18, 2007 at 04:58

Friday, May 18, 2007 at 04:58
Had my Navara opened up with a 2 1/2 " exhaust, into a straight thru hot-dog muffler, and dumped on the ground, beside the spare tyre.


Instant power difference, not so much on the economy, ( bummer )

Cost $ 220

Originally wanted a 3" but Exhaust bloke ( also a mate ) talked me out of it,, something about back presure and turbos ( " 6 cylinder diesel's need 3" ,, 4 cylinder diesel's need 2 1/2" ," ,,was his quote to me )

Great for towing, our camper, no need to try to hard, it just does it easier, and I have ben over the leadfoot thing for 20 years now ( well almost )
There is still a little hoon there I am sure , ( somewhere )

Hope this helps
AnswerID: 240683

Reply By: Member - Bruce and Anne - Friday, May 18, 2007 at 07:27

Friday, May 18, 2007 at 07:27
Firstly my two MUs have 3 inch mandrel bent systems, probably 12% to 15% improvement in power, nothing in economy (foot closer to the floor haha).
Now in the Marine industry boats have huge exhausts, cause they have the room, but an example: a Yanmar 4 cylinder turbo diesel of 3.45 litres water to air intercooler produces 230 hp/171 kw, not bad for a motor of that size and they have been around for some time, but the answer maybe the 6 inch exhaust coming out of the turbo and then 8 inch after that.
Cheers Bruce.
Cheers Bruce
D.Max and Jayco Outback

My Profile  My Blog  Send Message

AnswerID: 240688

Reply By: GU3.0 - Friday, May 18, 2007 at 10:47

Friday, May 18, 2007 at 10:47
I had a 2 3/4 mandrel bent exhaust made and fitted by Beaudesert Exhausts. The original cat pipe was removed and a 2 3/4 pipe was fitted inside. The resonator was removed along with the massive factory exhaust. It now has one smaller exhaust. Was advised that for a 3.0 4 cylinder 2 3/4 was more then engouugh. Very happy with the performance. I think the exhaust made more of a difference then the chip.

AnswerID: 240724

Follow Up By: gompy - Friday, May 18, 2007 at 14:20

Friday, May 18, 2007 at 14:20
Hi Andrew,
How much did you pay for that system? did you install it yourself?
I have a DPchip fitted and I am not impressed with the performance, maybe in combination with an bigger exhaust it will improve.
FollowupID: 501692

Reply By: GU3.0 - Friday, May 18, 2007 at 17:48

Friday, May 18, 2007 at 17:48
I paid $860 for the exhaust (fitted) I also have a rapid chip, and with both chip and exhaust my patrol produced 130hp at the wheels on the dyno. I think that to really appreciate the HP difference you have to get both chip and exhaust done. However having said that..... i noticed a better gain from the exhaust. The exhaust alone increased low down torque and i was able to hold 4th gear in soft sand as opposed to ringing the vehicles neck in third.
I also noticed that i was able to drive around corners and round abouts in third as opposed to having to go back to 2nd. I know doing this is probably not the best for the gear box however.... it gives you some indication of power gains from the exhaust system alone. Make sure you get the cat re piped or purchase a high flow version. The pipe inside the original cat is the most restrictive part of the entire system on the 3.0 GU.

I am selling my GU at the moment as i have purchased a ute. If my vehicle does not sell within the next week or so i will be selling the exhaust and chip if annnybody is interested. (i wil need to exchange the system for an original set up)
AnswerID: 240832

Follow Up By: gompy - Friday, May 18, 2007 at 18:15

Friday, May 18, 2007 at 18:15
Hi Andrew,
I am interested in your exhaust, if you not too far away.
FollowupID: 501734

Reply By: Chaz - Friday, May 18, 2007 at 17:50

Friday, May 18, 2007 at 17:50
If you still intend to run EGR, then 2 3/4” should be more than enough, but if you block the EGR system you can open it out as much as you like, provided you have some boost control installed . EGR needs some restriction in the exhaust, but not too much. The cat is the source of the most restriction and retains a lot of heat, but if it’s removed it will increase turbo spool up and the associated boost spikes. A 2 1/2” flow through system would be next to ideal for a standard car or a chipped car providing a moderate performance improvement. Opening the exhaust up will lower peak torque in the rpm range and lower low rpm EGT’s, but can have a negative affect on boost.
There is a lot more to this than some people realize and the ZD30 is already a sensitive motor, so doing one modification without doing the other can have negative affects. Having said that, they do have plenty of room for improvement.
I use a 2 ¾” dump (no cat) and a 3” flow through system with two 3” resonators that are specifically designed for their applications eg. one for the middle and one for the back. I have no EGR and use a manual boost controller that limits my maximum boost to 18psi at 4000rpm. I don’t use the VNT control solenoid.
Driving around the city, my EGT’s rarely exceed 250C and I still average 11.2L/100.
AnswerID: 240834

Follow Up By: gompy - Friday, May 18, 2007 at 18:33

Friday, May 18, 2007 at 18:33
Hi Chaz,
Thanks for your response, I am still not convinced about the benefits of blocking the EGR, I read somewhere that recirculating the exhaust gas actually reduces the egt, so I don't know what is achieved by blocking it and as you say it is already a sensitive motor, but having said that, I keep an open mind.
First I have some gauges fitted, so I can see what's going on.
FollowupID: 501743

Follow Up By: Chaz - Friday, May 18, 2007 at 20:00

Friday, May 18, 2007 at 20:00
Hi Gompy,
Yes, EGT and boost gauges are a must with the 3.0Di Patrol. EGR helps to lower peak combustion temps which will still have a small affect on EGT’s, but after fitting a larger less restrictive exhaust, they will be better. As I said, one modification usually requires another to compensate and blocking the EGR will require the boost to be lowered, just like fitting a larger exhaust, but not to the same degree. The only people that I know of that had negative effects from blocking EGR, didn’t lower their boost correctly. If you’re not happy about doing the other mods, then it would be best to fit the more conservative 2.5” exhaust. Just my opinion, but it does come from some experience.
My Patrol
FollowupID: 501770

Follow Up By: GU3.0 - Friday, May 18, 2007 at 20:16

Friday, May 18, 2007 at 20:16
Be VERY VERY careful blocking EGR, i say this as i went down this path and did not really know what i was doing. I am not a mechanic and don't fully appreciate the workings of this engine. As a result of my poor understanding and endless pursuit for engine power enhancements i blocked my EGR. After i blocked my EGR the backing plate disintegrated under extreme heat and went through my engine..... Result $7561.00 engine rebuild from Nissan in February of this year.

I realise that there are allot more people out there who know more about this engine then i do, and i am not dismissing there experience........... but i cannot stress to you enough BE VERY CAREFUL what you do with this engine!!!!!! The power increase i gained from blocking the EGR was not worth the hassle. The exhaust and chip mod is about as far as i would go, and netted me more power.

I know Chaz has allot of knowledge Re: this engine, as i have read allot of his posts on BUT if your engine destroys itself from a modification you have made you will be forking out your hard earned. I reside in Brisbane.

FollowupID: 501772

Follow Up By: Chaz - Saturday, May 19, 2007 at 01:16

Saturday, May 19, 2007 at 01:16
I’m sorry to hear that you had a motor go, particularly if it was due to the EGR blocking mod. Your advice is good and people contemplating these mods should be aware of the possible consequences. Once you make changes, you become your own warranty.
Unfortunately, I’ve heard of too many ZD30 Patrols letting go that were dead stock, using the recommended oil and servicing intervals. So rather than waiting for it to happen, I chose to try to prevent it, but if it happens, I’ll have to wear it.
All I’m trying to suggest to Gompy is that if he goes to a 3” system, he should consider some other mods also, but if he doesn’t want to, he should consider the smaller exhaust system.
I would be keen to know what material you used to block your EGR.
FollowupID: 501824

Follow Up By: gompy - Saturday, May 19, 2007 at 18:26

Saturday, May 19, 2007 at 18:26
Hi guys,
Thanks for all the responses, it's a bit clearer now.
I think I go for the 2.5" exhaust, have the gauges fitted and later do the egr just to see the result, it is an easy mod to reverse anyway.
Again, thanks to all of you!
FollowupID: 501924

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