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2.5" Dump pipe for 4JB1T

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2.5" Dump pipe for 4JB1T

Postby lucasks82 » Sat Apr 04, 2015 8:25 pm

I own a 91 Rodeo 2.8L with the 4JB1T engine, it goes great and never misses a beat but I would like the turbo to spool up a bit faster and get the benefits of a little more low down power and torque and hopefully increased fuel efficiency.

I have found out on this forum that a 2.5" straight through exhaust is the way to go but my problem is I cant find a 2.5" dump pipe to suit my engine and turbo. On ebay and an online store you can get one for the 98 model and onwards but not the earlier models :x

Would anybody have a used one they do not need any more?

Should I ask around at the wreckers?

Does anybody know who can fabricate one?

Any help or advice would be much appreciated :D
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Re: 2.5" Dump pipe for 4JB1T

Postby geeves » Sun Apr 05, 2015 6:19 am

Dump pipe is good for the last few horsepower but a big bore without the dump pipe still gives quite usable improvement as does a high flow air filter and snorkel.
If the 98 one you saw quotes your engine it should work but be aware there are 2 different oil filter settups on that engine so you might have to play with that to fit
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: 2.5" Dump pipe for 4JB1T

Postby lucasks82 » Sun Apr 05, 2015 10:17 am

Thanks Geeves, I have some more questions

1. What do you mean by "big bore" do you mean a big exhaust? I do want to get a 2.5" exhaust.

2. I have a unifilter - is that "high flow"

3. So a snorkel will help? I have seen them on ebay, are the cheap ones ok?

4. So with the oil filter, can I change its orientation to make the dump pipe fit? Mine is upright, is it different with the 98 model?

Thanks for your help
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Re: 2.5" Dump pipe for 4JB1T

Postby geeves » Sun Apr 05, 2015 1:27 pm

standard exhaust is 2 inch anything bigger is big bore
Unifilter is good as long as its cleaned correctly
Snorkels help some cars more than others. You always get cold air which is good but also replace a fair bit of the intake plumbing and on some cars thats a huge improvement
Changing the oil filter location means changing the housing it connects to. Is your filter on a slant or straight up and down? Which filter is it
I dont know when Holden started putting the later belt drive engine in the Rodeo or when they changed to the 4jh1
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: 2.5" Dump pipe for 4JB1T

Postby isuzurob » Sun Apr 05, 2015 3:01 pm

91-97 4jb1 engines in rodeo were the same a 4jb1 mu so oil filter points upwards, 97-01 4jb1 the oil filter faces down like the 3.1 4jg2 mu/bighorn, end of 01 they went to 4jh1 with top mount intercooler, as above can change oil filter housing and piping, or get a cutstom system made for you truck, they normally fit alot better
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Re: 2.5" Dump pipe for 4JB1T

Postby lucasks82 » Sun Apr 05, 2015 5:02 pm

ok thanks for the info.

are the cheap snorkels ok or should I fork out for a decent one? What brands do you suggest?

the filter is straight up and down. Its a Z178A oil filter

my car has the 4JB1T engine.
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Re: 2.5" Dump pipe for 4JB1T

Postby geeves » Sun Apr 05, 2015 6:30 pm

there isnt much technical difference between comercial snorkels but the likes of airflow and safari have spent more research dollars on making them easy to fit right and mounts etc. Typical story with the cheapys is "Once I got the thing in it was fine"
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: 2.5" Dump pipe for 4JB1T

Postby Downhillnz » Mon Apr 06, 2015 5:54 am

In regards to the dump pipe. I would suggest going to a 3.1 oil filter set up. I wish I had before I made my first dump pipe.
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Re: 2.5" Dump pipe for 4JB1T

Postby lucasks82 » Mon Apr 06, 2015 6:04 am

Is that off a 3.1L Jackaroo?

How does that help?
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Re: 2.5" Dump pipe for 4JB1T

Postby geeves » Mon Apr 06, 2015 6:28 am

The angled filter allows more room and better angles. Also with the straight up and down version you are already limited in room to do filter changes and the dump pipe will take half of that
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: 2.5" Dump pipe for 4JB1T

Postby lucasks82 » Mon Apr 06, 2015 6:50 am

Do I modify my existing oil filter setup? How?

Or do I source the angled oil filter setup? From what model?
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Re: 2.5" Dump pipe for 4JB1T

Postby isuzurob » Mon Apr 06, 2015 7:17 am

as my post above, you need the filter housing and pipe work off a 98 on 4jb1 out of a rodeo or one off a 3.1 bighorn/jackaroo, the filter pionts down towards the front diff
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Re: 2.5" Dump pipe for 4JB1T

Postby lucasks82 » Mon Apr 06, 2015 7:31 am

ok thanks. I will try to source the filter housing and pipe work you mention so I can fit the 2.5" dump pipe.

Cheers for your help, I hope I have some luck and can find the gear
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Re: 2.5" Dump pipe for 4JB1T

Postby nb422 » Mon Apr 06, 2015 2:38 pm

lucasks82 wrote:are the cheap snorkels ok or should I fork out for a decent one? What brands do you suggest?.

Pay the extra for a quality one, or if you want to go all out get a custom stainless one. I bought a cheap snorkel and regretted it immediately, very weak and poor fitting
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Re: 2.5" Dump pipe for 4JB1T

Postby lucasks82 » Mon Apr 06, 2015 7:00 pm

thanks.

I have actually seen safari snorkels on ebay for my truck for only $350 so that would be the go for me I reckon
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Re: 2.5" Dump pipe for 4JB1T

Postby geeves » Mon Apr 06, 2015 7:46 pm

An x member here that no longer goes 4wding had changed to Vitaras He sold one vitara to a young guy that rolled it. He then bought the snorkel off the wreck and refitted it to his new truck. Snorkel had a few stone marks in it but was fine. That was a safari snorkel
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: 2.5" Dump pipe for 4JB1T

Postby lucasks82 » Mon Apr 06, 2015 8:02 pm

that sounds like a tough snorkel. safari is at the top of my list.


Also I have found a guy about 100km away who has a 98 rodeo for parts and he says the oil filter points east west - down the front of the engine. Does that sound right?

I thought in the 98 they are vertical and facing straight down, is that right?
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Re: 2.5" Dump pipe for 4JB1T

Postby isuzurob » Tue Apr 07, 2015 4:46 pm

97 rodeo the filter points down on a 45 degree angle in a north south position, it sits just above the front diff head
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Re: 2.5" Dump pipe for 4JB1T

Postby geeves » Tue Apr 07, 2015 6:03 pm

what about the v6 or 2.6 petrol engine? Neither are any use in this case though
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: 2.5" Dump pipe for 4JB1T

Postby lucasks82 » Wed Apr 08, 2015 7:49 pm

I have been to a local exhaust shop and he suggested just doing a 2.5" exhaust from the existing 2" dump pipe.

Is that a good idea?

I mean wont it constrict the air flow right from the turbo and negate some of the benefits of having a big bore straight through exhaust?
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