bigger exhaust on turbo diesel
Submitted: Monday, Mar 08, 2004 at 13:31
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biscuits
Hello Everyone,
Im thinking about putting a new exhaust on my SD33T patrol - but I dont know how a turbo diesel goes with a bigger exhaust.
I know from experience with petrol turbos that a 3" exhaust generally sees about 2-3 psi increase in peak boost (give or take a bit) - of course the Air Flow Meter picks this up on a EFI car and corrects for it in fuel and (where applic) ignition maps.
So what happens with a diesel - do i need to get it re-timed for the extra 3psi of boost? or do I just run it a bit leaner and not worry? does it somehow compensate?? (i cant see how it would but then im no diesel expert). I just dont want to shorten the life of my engine by leaning it out (400k kms and still going strong).
Oh and are diesels any quieter/louder than a petrol? I am still debating whether to go 2.5 or 3" (thats if i go a bigger exhaust at all in the end). Anyone notice a big difference with a bigger exhaust?
Thanks!
Dave.
Reply By: biscuits - Monday, Mar 08, 2004 at 16:37
Monday, Mar 08, 2004 at 16:37
Thanks for the replies everyone.
I could have sworn that the boost jumped from 6 to 9 psi on my CA18DET engine when I got a 3" exhaust - but then I am running a $10 boost guage so I dont know how accurate that all is! Plus the turbo was an aftermarket install job.
I suppose when I think about it, at the end of the day the wastegate is opened by the actuator which runs off the pressure in the compressor housing - so an exhaust shouldn't have any bearing on boost pressure...
Oh
well, thats good I sorted that out at least. Sounds like a 3" with no muffler is the way to go - at least I can put a muffler or hotdog (resonator) on that if I think its too noisy.
Thanks again,
Dave.
AnswerID:
49541
Follow Up By: Dave from Fraser Coast 4WD Club - Monday, Mar 08, 2004 at 18:18
Monday, Mar 08, 2004 at 18:18
yeah biscuits
the boost level is determined by the wastegate settings, you could run without any exhaust at all and there would be no change in maximum boost.
FollowupID:
311351
Reply By: CMB - Monday, Mar 08, 2004 at 18:48
Monday, Mar 08, 2004 at 18:48
Hi all.
My first post.
The 4.2 TD GU has it's waste
gate set at 8 psi so I guess your SD33T would be about the same (the blowoff valve seems to operate at about 13 psi). As stated by others, the boost will not be altered by a bigger exhaust. The back pressure will and fitting a bigger exhaust (I have 3" mandrel) will reduce this and allow the turbo to spool up quicker at lower revs. Mufflers etc make different noises. Just don't get caught by the Dept of T'port with a louder than standard truck.
Talk to Mannell Motors, Superior Turbo's etc about aneroid valve changes, timing, turbo refits (they machine the insides to take a different rotor) etc to get more power. It makes a HUGE difference to power. Being electronic, you could simply fit one of those power up chip things.
My biggest problem with having the above done is the heat under the hood that kills my dual battery yearly.
Good luck.
Chris.
AnswerID:
49569
Reply By: Member - DOZER- Tuesday, Mar 09, 2004 at 22:31
Tuesday, Mar 09, 2004 at 22:31
Turbos hate backpressure, as they work on pressure differential, the less restriction after the turbo, the faster it can spool up and the faster heat gets out, and the cooler it all runs, but the waistgate will still control max boost, and SOMETIMES, a little more can be squeezed in without overheating things if it runs cooler with std boost. So better response from the pedal and welly, and possibly more from a bit more boost. Dont forget for any engine speed with the larger exhaust, you will be getting more boost than b4 and therefore more power can be made. U can try removing the muffler and fitting a hotdog resinator in its place to get cheaper benefit than whole replacement.
Andrew
AnswerID:
49713