turbo question

Submitted: Wednesday, Mar 22, 2006 at 15:13
ThreadID: 32034 Views:2263 Replies:6 FollowUps:6
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I'm no expert which is why I'm asking this question! If I open up my exhaust system (2.5" for example) is there much point if the turbo vent stays the same size? The turbo would still be the bottle neck wouldn't it?
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Reply By: Turbo Diesel - Wednesday, Mar 22, 2006 at 15:26

Wednesday, Mar 22, 2006 at 15:26
Gossy you answered your own question!
AnswerID: 162233

Reply By: Gossy - Wednesday, Mar 22, 2006 at 15:47

Wednesday, Mar 22, 2006 at 15:47
that's my point. Why spend $400 upgrading an exhause system then?
AnswerID: 162239

Follow Up By: Rosco - Qld - Wednesday, Mar 22, 2006 at 16:04

Wednesday, Mar 22, 2006 at 16:04
Zackery!

Any pipe dia > turbo outlet dia = $$ down drain.

Cheers
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FollowupID: 416935

Reply By: Darian (SA) - Wednesday, Mar 22, 2006 at 15:55

Wednesday, Mar 22, 2006 at 15:55
Hmmm - a debate on gaseous dynamics - stand clear for an avalanche of science Gossy ! My humble thought would be that as the gas cools down the exhaust could actually be proportionally reduced towards the rear, without ill-effect... which means that while that would be silly, your hypothesis must be correct !
AnswerID: 162241

Follow Up By: Rigor - Wednesday, Mar 22, 2006 at 16:07

Wednesday, Mar 22, 2006 at 16:07
Spot on Darian , the best results are by upping the size at the turbo , the further back you go the less increase in performance is noted.
I agree a straight through muffler will help to a degree but useless if upstream is not free flowing. As I have aged I like less the constant drone of an exhaust "note" when it is not really needed.

Cheers Dave L.
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FollowupID: 416936

Reply By: Leroy - Wednesday, Mar 22, 2006 at 16:07

Wednesday, Mar 22, 2006 at 16:07
What size is your turbo outlet? Often the size of the turbo outlet is larger than the exhaust diameter. Also your exhaust may have a restrictive dump pipe and catalytic converter. I was also informed a 3" would be even less restictive but depending on the flange size on the cat depended on if you could go up to this size. The less restricive the exhaust the easier for the turbo to spin up. If it's restrictive then the turbo fights against this and doesn't spin up as quickly. There's a post on Outerlimits in the 4x4 tech section with an exhaust guy there answering questions. I did a post but ended up giving him a call as well for more information.

Leroy
AnswerID: 162246

Follow Up By: Member - Roachie (SA) - Wednesday, Mar 22, 2006 at 16:32

Wednesday, Mar 22, 2006 at 16:32
Somebody mentioned in a post on this topic in the last few days that when they removed the dump pipe from their turbo (I think it was a 4.2 Patrol), they could quite clearly see that the opening in the dump pipe was significantly smaller than the outlet on the turbo.

Therefore, by adding a new dump pipe and free flowing exhaust, you ARE (in relation to that particular vehicle anyway) aiding the flow of gas and the result IS noticeable.
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FollowupID: 416941

Follow Up By: Gossy - Wednesday, Mar 22, 2006 at 16:32

Wednesday, Mar 22, 2006 at 16:32
no idea on the size of the exhaust. It's a Patrol GQ 2.8td.
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FollowupID: 416943

Follow Up By: Member - JohnR (Vic)&Moses - Wednesday, Mar 22, 2006 at 22:18

Wednesday, Mar 22, 2006 at 22:18
Yeh Roachie. Mine was 1.7" diameter through the dump pipe as I measured it off a 1.5" washer. That is one hell of a restrriction but I would still upgrade the pipes through though it may be a point of conjecture if 2.75" or 3.0" is the best size. Seeing it will probably get bent or flattened somewhere why not allow lower restriction?

On my 4.2 intercooled I had a 16% better 0-100 kph time which gives an incidication of better torque,power and flexibility right through the range.
Cheers,
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John

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FollowupID: 417070

Reply By: DamoHJ61 - Wednesday, Mar 22, 2006 at 22:22

Wednesday, Mar 22, 2006 at 22:22
Hi Gossy, I just had a 3" system fitted to my 12HT, the difference it made was quite noticeable. It did have a standard system on it and I would imagine that it would have been quite restrictive, opening it up has provided a quicker boost effect resulting in improved performance.
I would highly recommend it!
AnswerID: 162365

Follow Up By: TUF80 - Wednesday, Mar 22, 2006 at 22:49

Wednesday, Mar 22, 2006 at 22:49
HI DAMOHJ61 WASNT YOUR OUTLET PIPE VERY RESTRICTIVE ONLY BEING 1 1/2" DIA . IT WOULD HAVE MADE A MAJOR INCREASE IN POWER.ESPECIALLY DOWN LOW
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FollowupID: 417082

Reply By: Member - TPM (SA) - Thursday, Mar 23, 2006 at 18:32

Thursday, Mar 23, 2006 at 18:32
If it didnt do anything the pipe would be really small from the factory. Look at sports cars they all run bigger exhausts because its proven for horsepower gains.
AnswerID: 162526

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