Exhuast Questions for Dr Exhaust

[francesco]

Hi All,

not sure if many of you have noticed but there is a guy on outerlimits who seems to know his stuff about exhausts and has a super thread going.

I thought it would be a good optortunity for us to get a fresh opinion about exhaust options for our 4bys. I for sure am sick and tired of getting told a differnt story every time a speak to an exhaust shop....

So, post your questions in this thread, then I will compile them and post it in his thread on behalf of club isuzu.....hows that sound.

Lets aim to have the questions ready within 3 days...


Cheers Francesco

;D

[Witchdoctor]

Just get the longest you can get for the money you have ;D, do not get a plastic one as it will melt . Best material would be paper but just watch water crossing Frank as this will be a real problem you could get water in the turbo(not good) ;D.

For some serious advise the pro's say on 3.1 deisel 2.75mm is a great match. Under that is a bit restrictive, over that is just a waste of money or no real gain for the $'s spent. If you are chasing every inch of Horsepower or racing the truck go the larger.

Hope this helps

dave

[adam]

Have read that thread you are talking about.

Someone else posted about 4jb1's in there & he said if you want 14psi then u gotta go to 3" to get maximum power, I imagine this is the same for the 3.1's.

He said the turbo/turbo manifold provides backpressure for low down torque, so you don't need any 'backpressure' so to speak.

Anything past the turbo you want to get the gas out as quick as possible, therefore 3" is worthwhile.

Mandrell's are definetly better then press bent, but for the price, and the performance gained I don't think you will notice the difference.

I am just going to get a 2.5" system made up, as I have read it's harder to squeeze a 3" system under there, and AFAIK, the outlet off the back of the turbo is 2.5" - so there is probably SFA gains to be had by fitting a 3", unless you are going to run a larger turbo later.

[Jimmu]

There is a significant difference in minimum pipe diameter between press and mandrel. If you are spending the money to replace the exhaust spend the extra $100 and get it Mandrel.

Jimmy.

[francesco]

I found a guy who will do 3inch mandrel from turbo back for $600, he is in Wynnum area and he did Roothys extractors. Its welded.

I have already posted the questions to the guy on outerlimits, waiting for reply.

[Jimmu]

Just make sure that when they say from the turbo back they include the dump pipe. Many shops refer to from the end of the dump pipe as 'from the turbo back'

I would speak to Exotic Exhausts if you are in Brisbane. They are used by some of the top performance guys and are artists with a welder. They have already done my dump pipe so know what it is about. They wont be the cheapest but they reasonable and will do an excellent job.

Exotic Exhaust
Phone:[phone]
Location: 29 Jijaws Street Sumner Park

Rob Bliss did Bruces. He also did the system for my SS Commodore a few years back and did a good job.

Bliss Rob Exhausts
Phone: [phone]
Location: 264 Robinson Road Geebung

Jimmy

[francesco]

Yep...that included dump pipe...it was for the whole thing....he said that he could make it run straight down the right side too....

[adam]

Rob Bliss quoted $480 for a mild steel 2.5" system, I would say that is press bent, however it does include the dump pipe.

[francesco]

2.5 press including dump should cost about $300

[Bruce]

When I had my 2.5 press bent done in Rocky cost me $180 with muffler.

[adam]

true, so rob bliss is a pretty exe quote then, anyone had one done recently?

[francesco]

Adam bear in mind that Bruce got his done in Rocky....I think the average price in Brisbane is about $300 but no less than $270ish....if you going to pay $480 you might as well go mandral

[Jules]

Got mine done at Rob Bliss - $325, 2.5" pressed. Goes like hell, however, not really happy as I had to spend full weekend removing silver paint overspray. You'd think they'd paint it before installing!

1990 Mu

[adam]

did that include the dump pipe jules?

[Jules]

adam said:

did that include the dump pipe jules?

Adam, good question! Should explain this is my first diesel and first turbo car. What am I looking for? I looked up/down/through wheel arch. I can only see the new exhaust connected directly to the casting attached to the turbo.

Are you talking about a wastegate pipe? There isn't one, it appears that the turbo has an integral wastegate feeding directly into the exhaust. I think!

[Jules]

By the way, I take back any recommendation for Rob Bliss Exhausts. In trying to answer Adam above, I've looked all over at the exhaust and the workmanship is shocking! The downpipe from the turbo is welded to the rest of the system at maybe a 30degree angle. Looks like they bent the pipe too long then cut it half way along the bend. Being a pressed system, the bent part is reduced diameter and the joint to the downpipe has been MIG'd to fill the gap. And the welding itself isn't very good - it's got a hedgehog sitting on top!

It just proves that a bad 2.5" exhaust is still miles better than the standard system. Now I'm wondering how good would a mandrel 3" system be.

If you use Rob Bliss, INSIST that their apprentice doesn't do it.

[adam]

Can you post some pictures of the above?

And yes a dump pipe refers to the section of exhaust that connects directly to the turbo.

Some dump pipes are built with a secondary pipe & a seperator which blocks off the wastegate and apparantly helps spool the turbo faster, I don't think it's a problem on the factory turbo though, more on hi-po 4 cylinders which are trying to get boost on earlier.

I would be interested to see what the Rob Bliss exhaust looks like, as they were the mob I was going to go with up until you posted the above

[Jules]

I've taken some shots but don't have wepage to upload to. Send me an email: djthomas(at)tpg.com.au and I'll reply with pics

[Jules]

Just thought I'd post the emails - some interesting stuff about Rob Bliss Exhausts

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Sent: Sunday, September 17, 2006 12:17 AM
Subject: Pics of MU Exhaust

G'day mate,
Adam from Club Isuzu forums here - just chasing those pics of the exhaust you mentioned?
Interestingly enough, they quoted me $480 because they reckoned the dump pipe would take just as long as the rest of the exhaust - hence they probably learnt on your car & now charge a lot more for a Mu exhaust system. )
I guess the good news is though, like you said, even a crappily built press bent 2.5" exhaust does wonders over the standard system.
Do you know what your economy was before/after the exhaust ?
Cheers, Adam

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Sent: Sunday, September 17, 2006 6:49 AM
Subject: Re: Pics of MU Exhaust

Adam, pics attached. I'd say fuel economy has improved - I used to fill up after 600km but now it's 630 to 650km. That's not down to an empty tank.
It is much more fun to drive now, feel the turbo starting to kick in earlier at 1700rpm (was 2200rpm) but top end has huge gain - peak revs gone up to 4500rpm or more. It used to struggle past 3500rpm.
Funnily enough, the only reason I found the forum was I needed help to find out what was wrong with the Mu just after I bought it. A work colleague's 3.0D Hilux (non-turbo) was quicker off the lights than mine! I got the exhaust done 18 months ago - wished I'd done it earlier now.
So yes, get that standard exhaust off immediately - anything IS better.
Regards,
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EDIT - Are you able to post the photos here so others can see

[francesco]

My post

Hi Dr exhuast,

Thank you in advance for answering my questions. I have a few questions, hope you dont mind but I am asking these on behalf of Clubisuzu www.clubisuzu.com so I am saving you from about 300 members coming here to ask you the same questions. I will post your reply and Work contact details in our club forum.

We mainly have members who drive Isuzu MU, Wizards, Bighorn. So 2.8 (4JB1T) turbo Diesels and 3.1 (4JG2T) Turbo Desiels. Most run there boost or want to run there boost at about 12psi and some do up to 14 psi.

1) What system do you recommend for each of these vehicles i:e 2.8 and 3.1 turbo diesel.

2) Back Pressure, whats the story, is it a factor or not ?

3) With Mandrel systems, to have a welded sytem or bent system, is there any difference in Performance ? Does it really matter?

4) Please any other interesting things you might like to add for us, perhaps any things you may have discovered while working on these 4x4's


Thank you

francesco


His Reply

Hi you have lots of questions ill try my best to give you some help.

Ok rule of thumb, a 4 cyl normaly asperated engine should need no more then a 2" system or in a few cases where the motor has improvments it may warrant 2.25" .

All the systems i build have straight through mufflers depending on how loud u want relates to the size and amount of mufflers most n/asperated cars ned about 2lb back pressure.

With turbo cars any thing under 7-10 lb boost 2,5" is fine but any more then that 3" is preferable mandrell pipe work is a litter better on a turbo car than press bending again straight through mufflers.

Deisel is almost the same as a turbo almost zero back pressure and larger pipe sizes.

i hope this helps
ross