PUMA Hi Flow Exhaust.

Hey Tristan,

Thanks for your input.

I do have a couple of bits on the way from the UK. I have recently bought an Off Road van and just a little extra towing power would be nice. Not trying to make a rocket by any means.

I got a couple of quotes on upgrades and prices were above $4k, seemed a bit over the top.

I have done a little bit of research and it is a steep learning curve.

The exhaust system up grade know seems to be a waste of time and money, while the re-map and intercooler appear to be the best value for money.

Time will tell I guess.......

Dougal and John know a hell of a lot more about this than I do, so this is pretty rudimentary.

Apparently turbo overspeed can happen, but you really have to push the turbine well outside it's normal operating envelope

From Garrett.

◊ The Choke Line is the right hand boundary of the compressor map. For Garrett maps, the choke line is typically defined by the point where the efficiency drops below 58%. In addition to the rapid drop of compressor efficiency past this point, the turbo speed will also be approaching or exceeding the allowable limit. If your actual or predicted operation is beyond this limit, a larger compressor is necessary.
◊ Turbo Speed Lines are lines of constant turbo speed. Turbo speed for points between these lines can be estimated by interpolation. As turbo speed increases, the pressure ratio increases and/or mass flow increases. As indicated above in the choke line description, the turbo speed lines are very close together at the far right edge of the map. Once a compressor is operating past the choke limit, turbo speed increases very quickly and a turbo over-speed condition is very likely.


http://www.turbobygarrett.com/turbob...3_enlarges.gif

Now whether that is possible with a small factory VNT :confused:
I'm guessing you'd need to substantially up the fuel map and install a short 3" pipe to see that happen, but I really don't know for certain

I'm with Steve, I reckon the rest of the reasons given against a big pipe are bollocks, except that I don't doubt for a second that a Tdci engine won't see any gains over the factory exhaust unless huge changes are made elsewhere too.
Most modern cars are very good in terms of inlet and exhaust optimisation, you really need to up the HP/torque potential to need a more efficient exhaust.






Anyway, FWIW I built a 3" system for my TDi years ago.
Yes, it's two generations older than the current engine, but it's still a direct injected turbo diesel and the stock system is pretty good. 60mm tube, all mandrel bends, straight through perforated tube main muffler and resonator.

Was it overkill ?

Yes. 2,3/4" would have been overkill too (but much more exxy) and 2.5" wasn't a whole lot bigger than stock. (but in hindsight probably the 'right' size)
I'm an ex-racer and in my mind back pressure was bad for a turbo.
F1's and Champ Cars used a short stub, so i was after minimal back pressure too :D

The first noticeable thing was a drop in EGT's at maximum fuel/load on my test hill. (stock pump settings)
This was repeatable over a number of weeks, and by the same amount each time, to the tune of 25*.

The second thing was an immediate lengthening of the torque/rev range.
Prior to the new exhaust 3rd gear peaked at around 70km/h, it just wouldn't rev past that. With the new system I could hit the governor in third, although it wasn't pleasant, (don't ask how fast) and 90km/h was and still is pretty easy, although it achieves nothing over changing at 80km/h and using the torque in 4th, it can be handy in some situations.
It'll also achieve an 18.04 second 0-100km/h time with 33.3" Mt's and weighing at close to 3 tonne (had it over a weighbridge a few months back) so not too shabby for an asthmatic Tdi with close to 300,000km on it.

The exhaust build was over 5 years ago and the turbo is still spinning, it hasn't flown to bits yet (touch wood)

Anyway, the point of all that was;

1. the bigger exhaust reduced backpressure and gave an improvement in response and pressure operating range on that engine.
2. the reduced backpressure also resulted in reduced EGT's which means reduced heat in the manifold/turbo housing. This gives more scope for increased fuel=more power within a safe operating range.

The downside ? (other than the aggro of doing it myself :wallbash:)

Too bloody loud.
It's hard to make quiet unless you introduce a chambered muffler. The minimal main muffler and decently sized resonator I have aren't enough.

Drover, on another vehicle I fitted a 2.75 inch exhaust and a chip to a 3lt 2006 diesel.
No dyno to prove any results, just what I felt

The exhaust removed the cat converter and had a hi flow muffler. The car held speed better on inclines but thats about it. It was louder, much louder though the manufacturer couldn't believe it when I told him it sounded a bit like a bombed patrol.

The chip gave excellent bang for the buck. It did blow more smoke but if you drove it sensibly you got more response with out a great change in economy. If you wanted to drive it a bit racy it drank fuel like it had a hole in the tank, but yes it did get up and go.

For my money I would consider a chip, or map if I was towing, but keep the cash in my pocket when it comes to bigger exhausts.

It sounds like you have come to that conclusion anyway:BigThumb:

Thanks Rick130, excellent advice.

Sam65

Quote:

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Originally Posted by roverrescue

Where is Dougal or John (Bush65) or Rick when you need em.
Im not doubting that Bell Auto have found no benefit in a 3in exhaust.

BUT - it aint not nothing to do with the mubble and jumble reasons you have written!!!!

-For the same volume and initial velocity a larger diameter pipe cannot decrease velocity of a gas (bends and non laminer flow etc can)

-A turbo diesel has no need for back pressure

-A turbo diesel only needs to get hot gasses from exhuast ports to the turbine... after that all bets are off!

Discuss ;)

Steve

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Out of curiosity...

Given this situation where the pipe is the same layout (bends, muffler, etc), doesn't a larger diameter pipe decrease velocity because the gas expands thus losing pressure and speed? Is it because it doesn't matter what happens after the turbo spits it out?
Why is there no need for back pressure?

Quote:

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Originally Posted by firsttimedefender

Out of curiosity...

Given this situation where the pipe is the same layout (bends, muffler, etc), doesn't a larger diameter pipe decrease velocity because the gas expands thus losing pressure and speed? Is it because it doesn't matter what happens after the turbo spits it out?
Why is there no need for back pressure?

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Larger diameter = lower velocity = Less pressure - which is GOOD for a turbo. Any back pressure reduces performance. You want high pressure before a turbine and low pressure after, for maximum performance.

DeltaP = V^2/D

Anyone who thinks you need to keep exhaust gas velocity high on a turbo diesel does not understand fluid mechanics.

Quote:

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Originally Posted by isuzurover

Larger diameter = lower velocity = Less pressure - which is GOOD for a turbo. Any back pressure reduces performance. You want high pressure before a turbine and low pressure after, for maximum performance.

DeltaP = V^2/D

Anyone who thinks you need to keep exhaust gas velocity high on a turbo diesel does not understand fluid mechanics.

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I understand fluid mechanics
B=Beer
B2=Bourbon
JW=Scotch
H2o=Water
W=Wine
Turbine=Party

B+JW=Headache
B2+JW=great Night
B2>H2ox2W+1B=100% Turbine Idiot

I recommend high pressure B2>H2o before Turbine and low pressure H2o>W after Turbine

See your not the only one who is highly educated.

:) :) :)

maybe the tractor drags are a good example they all run tailpipes straight off the turbos, no exhust system to speak of.