TD5 Exhaust - How Big?

[that_kid]

Hi all,

Ive done a bit of looking around the forum and used the search function with many combinations but havent found a concise answer.

what i was wanting to know is weather to go a 2.5" or 3" system.

Im having a straight through made up from the turbo back n was just interested to see what other think is the way to go.

Its not chipped yet n just runs the standard cooler.

Will there be any real dif between the two sizes? apart from the obvious 1/2" :P

[Redback]

The standard system is 2.75", so 3" is the go

[Aaron40]

Hi That_kid,

I am getting mine done tomorrow, done a lot of reading and ringing around and have opted for a 2.5 system in mild steel and budget had a lot to do with my choice... cat gone, muffler replaced with a high flow item. I will let you know the outcome tomorrow! This is something I read off the Alive tuning site that do a lot of Td5 tuning ..:D

"Why dont we make 'Big Bore' systems? A 3 inch bore system would not be appropriate for modern land rover diesels, since the turbo outlets are only 2 1/4 inches in diameter. Age old (Proven) tuning theory states that the optimal turbo down pipe should be 10% larger in diameter than the turbo outlet casting. This is precisely why land rover chose 2 1/2", as it's a perfect match to the turbo. Using 2 1/2" pipe maintains a rapid flow of exhaust gasses to get them out quickly! Using 3" pipe would reduce the velocity of exhaust gasses, their fore retaining excess heat at the turbo, and exhaust manifold. Another factor is the reduction of back pressure you'd get from a 3" exhaust, as the wide open space of the exhaust takes more gas to fill it, and hence push out the tailpipe. The result could potentially cause turbo over speed, which can seriously decrease the life span of your turbo!"

Take care,

Aaron.

[that_kid]

The standard system is 2.75", so 3" is the go






"Why dont we make 'Big Bore' systems? A 3 inch bore system would not be appropriate for modern land rover diesels, since the turbo outlets are only 2 1/4 inches in diameter. Age old (Proven) tuning theory states that the optimal turbo down pipe should be 10% larger in diameter than the turbo outlet casting. This is precisely why land rover chose 2 1/2", as it's a perfect match to the turbo. Using 2 1/2" pipe maintains a rapid flow of exhaust gasses to get them out quickly! Using 3" pipe would reduce the velocity of exhaust gasses, their fore retaining excess heat at the turbo, and exhaust manifold. Another factor is the reduction of back pressure you'd get from a 3" exhaust, as the wide open space of the exhaust takes more gas to fill it, and hence push out the tailpipe. The result could potentially cause turbo over speed, which can seriously decrease the life span of your turbo!"

.

interesting, but still conflicting.

will be interested to see how u go aaron

[isuzurover]

There have been a few threads about this. e.g.

http://www.aulro.com/afvb/90-110-130-defender-county/97186-exhaust-options-300-tdi-4.html

[Aaron40]

Thanks Isuzu rover.... was very informative thread and got a bit complicated...was interesting however was directed at the larger turbo... don't think I would do the bigger turbo considering the cost except if I killed the standard, then the 2.5" system would need to be replaced with a 3":)

[isuzurover]

Thanks Isuzu rover.... was very informative thread and got a bit complicated...was interesting however was directed at the larger turbo... don't think I would do the bigger turbo considering the cost except if I killed the standard, then the 2.5" system would need to be replaced with a 3":)

Regardless of the size of your turbo, the laws of physics remain the same.

Plenty of turbo/exhaust experts have experience with petrols but not diesels.

[Aaron40]

I had a lot of trouble with that subject at school so I will have to take others advise! Thanks again for the info..;)

[Tombie]

Careful!!!

Well known Landrover modification specialists B.A.S and TD5 Alive both advise that the MAXIMUM for a TD5 is 2.75" (Factory is 2.5").

TD5 Alive also advises that if you fit a 3" exhaust with their upgraded turbo they WILL NOT honour warranty.

3" allows the turbo to overspeed on spool up damaging the turbo and causing overboost under hard throttle.

An issue I was unable to resolve in Lara with the original 3" dump pipe.

So either stay 2.5" and fit a straight through muffler / no muffler or go no larger than 2.75" (mandrel bent)

My current recommendation is stay factory size and just improve mufflers/flow. Vortex mufflers do a great job, but any improvement to the system (straight pipe, de-cat etc) will give benefits.

The factory pipe is Stainless, so worth keeping...

[Redback]

Careful!!!

Well known Landrover modification specialists B.A.S and TD5 Alive both advise that the MAXIMUM for a TD5 is 2.75" (Factory is 2.5").

TD5 Alive also advises that if you fit a 3" exhaust with their upgraded turbo they WILL NOT honour warranty.

3" allows the turbo to overspeed on spool up damaging the turbo and causing overboost under hard throttle.

An issue I was unable to resolve in Lara with the original 3" dump pipe.

So either stay 2.5" and fit a straight through muffler / no muffler or go no larger than 2.75" (mandrel bent)

My current recommendation is stay factory size and just improve mufflers/flow. Vortex mufflers do a great job, but any improvement to the system (straight pipe, de-cat etc) will give benefits.

The factory pipe is Stainless, so worth keeping...

Mike just an inquirey, Phil said he measured the turbo end of the exhaust (standard)and said it was 70mm, I've fitted a 75mm mandel bend to mine, is this OK(worried now:() back to the rear axle, it's standard from there on.

Baz.

[disco_thrasher]

how loud is it with a straight thru system no muffler no resonator is it rediculis or a good rumble

[Tombie]

how loud is it with a straight thru system no muffler no resonator is it rediculis or a good rumble

Just a rumble....

[isuzurover]

Mike just an inquirey, Phil said he measured the turbo end of the exhaust (standard)and said it was 70mm, I've fitted a 75mm mandel bend to mine, is this OK(worried now:() back to the rear axle, it's standard from there on.

Baz.

The overall pressure drop across your exhaust won't have changed much if you have only replaced 2/3 of it with 0.25" larger pipe.

[Tombie]

Mike just an inquirey, Phil said he measured the turbo end of the exhaust (standard)and said it was 70mm, I've fitted a 75mm mandel bend to mine, is this OK(worried now:() back to the rear axle, it's standard from there on.

Baz.

Should be ok, if you experience constant overboosting under hard throttle - regardless of settings then you may need to look into it...

But otherwise, just continue as is... Lara has a 3" with Vortex, a little twitchy on overboost if booted hard.... Just needed to be careful.

The turbo outlet necks down pretty quickly.

Isuzurover he's 3/8" over turbo outlet and 1/2" over diameter till the diff...
Then down to 2.5" (stock)

[isuzurover]

Should be ok, if you experience constant overboosting under hard throttle - regardless of settings then you may need to look into it...

But otherwise, just continue as is... Lara has a 3" with Vortex, a little twitchy on overboost if booted hard.... Just needed to be careful.

The turbo outlet necks down pretty quickly.

Isuzurover he's 3/8" over turbo outlet and 1/2" over diameter till the diff...
Then down to 2.5" (stock)

To go from a 2.5" to a 3" exhaust, we are talking about a 30% reduction in gas velocity, and a corresponding reduction in pressure drop (back pressure).

The TD5 is fitted to 90, 110, 130 and discos. If they all have 2.5" exhausts (of varying lengths), there would probably be a 30% difference in back pressure between a 90 and 130 exhaust (if not more).

I would be surprised if they are set up so close to the limit that a reduction in DP of that order can overspeed the turbo...