Thread: PUMA Hi Flow Exhaust.

Hey Drover,

I hate it when nobody replies to my posts

I had the same idea shortly after I bought my Defender, removed muffler first. No change, sounded the same and no performance change for 2 weeks. I then removed the cat and upgraded to 3" mandrel. Louder, not good loud! No performance increase and after a month noticed that it was using more fuel. Fit hiflow muffler in original position, sounded better but that was it. Stage three; fit stock exhaust and cat, suprise! I'm sure it gained half a horse power, quite and fuel consumption returned. I know this wasn't what you wanted to hear but there is the chance that every engine/EMS reacts slightly differently to such mods.

Kind Regards, Tristan

Thanks Tristan,

I have spoke to Pete from Bell Auto services in the UK and been advised not to go with a 3". Apparently the 3" pipe reduces exhaust gas velocity, causes lag, reduces the effectiveness of the turbo and allows heat to build up as the exhaust is not moving away fast enough.

The standard size 2 1/2 " is recommended and if you wanted too, you could remove centre muffler and add a "DeCat" pipe.

There is a mathematical calculation to do with the size of the turbo outlet and optimum exhaust pipe size being 10% larger.

The turbo outlet is 2 ¼” optimal turbo down pipe should 10% larger so the 2 ½” is a perfect match, a larger pipe reduces gas flow and retains heat in the turbo and exhaust manifold.

A 3” pipe would also reduce backpressure as it would take a lot more exhaust gas to fill it and to push it out the tail pipe. Potentially, causing turbo over speed, which apparently is not good thing.

It all sounds good and seems to make sense.

Cheers

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

Hey Steve,

I am just trying to recall in some order what i have been advised over the last few days.

I was heading down the path of a 3'" - Hi-Flow cat etc..

Now my thought have changed......always eager to listen and learn

Cheers

Hopefully one of the TD gurus will chime in.
I dont doubt that 3" gains nothing but noise on the new defender!
Theory and practise dont always align - when this happens many people (experts even) make up stuff that sounds convincing!

The test fo the ideas purported above would be to go for a blatt around the block or better yet on a dyno with the dump removed altogether!

S

Read 08Benders reply. Pat

Hey Drover - might be worth sending a PM to Tombie2 as he has some experience with exhausts (as I recall from some older posts).

I think his opinion is not to go big with exhausts - doesn't help at all.

Cheers
David

Well, that got a few responses Grover

I suggest you stick with what Henry gave you! Anything else is dollars down the drain on a TDCi. I know there are companies selling lots of trick parts including software but when it comes to developed small capacity diesel the only way to get power is more fuel. If you can live with the 90kw then you have a great little package that should last years, otherwise look at an auto conversion (just a thought)

Please don't hate me