3" exhaust ideas for 300tdi 110.

[Landy-Novice]

hello all.

i need to start thinking about sorting the poor excuse of an exhaust that is currently attached to my 110.

this i think this is a good opportunity to go with a 3" straight through system in stainless steel for more 'power' and noise. afaik, no off the shelf exhausts will fit (reto fitted 300tdi using LT77 gBox mounts) and don't quite seen to be what im after. (mainly mandrel bends, not center push bends)

not sure it will fit, as it looks like a 3" pipe will be a very tight fit between the gearbox and x-member, so i think i may have to make a new one out of some 100x50x3mm box which will give an extra 2 inches of space. or take a large notch out.

next issue that i cant work out is how to attach it to the turbo.. sounds mad doesn't it?! but i believe the turbo has a 40mm dump pipe/exhaust outlet. and the flange for the downpipe has a 72pcd and it needs to be somewhere around 88pcd to attach a 3" pipe. so do i had to use a reducer 'upsidedown' like this or is there a flange adapter? can anyone post some pics of a the above?

i plan to get all the necessary parts from jetex or exhastpartsuk. unless there is a cheaper place to get all supplies?

many thanks.

[dirtydiesel]

Exhaust supplier questions

http://forums.lr4x4.com/index.php?showtopic=82246

As for the gearbox mounting you could just make a new mounting to get the 3" through,

Or use the stock non cat non flexi front pipe, (thats around 2.63 i think), and a td5 rear section ( this is a little larger again maybe 3") then just join the 2 with a nearly dead straight bit of 3"

[rick]

not sure it will fit, as it looks like a 3" pipe will be a very tight fit between the gearbox and x-member, so i think i may have to make a new one out of some 100x50x3mm box which will give an extra 2 inches of space. or take a large notch out.

next issue that i cant work out is how to attach it to the turbo.. sounds mad doesn't it?! but i believe the turbo has a 40mm dump pipe/exhaust outlet. and the flange for the downpipe has a 72pcd and it needs to be somewhere around 88pcd to attach a 3" pipe. so do i had to use a reducer 'upsidedown' like this or is there a flange adapter? can anyone post some pics of a the above?

i plan to get all the necessary parts from jetex or exhastpartsuk. unless there is a cheaper place to get all supplies?

many thanks.

A 3" pipe goes past the g/box and t/case + cross member with miles of room to spare.

You just follow exacly where the 2.375" one went.

As for the dump, you use a standard three bolt flange flange, thoat the cast dump out to 2.5" ID and get someone to flare up some 2.5" pipe to 3" at a 15* or so taper, I just made a flaring swage out of some 3" bar stock I had lying around, stuck it in a press with some 2.5" exhasut pipe I had and made it up.

Buy a bunch of mandrel bends, a decent muffler and most definitely a resonator and go at it.

Trust me, it will need to be muffled, if you don't install a resonator a new muffler will be created, it's called the cab.

The harmonics when cruising at 100km/h will destroy your brain in 10 seconds flat, and SWMBO could hear me near 8 or so km away from home coming down a mountain side, it's that loud.

Don't let anyone try and tell you a 300Tdi Garrett turbo acts as a muffler.

I'll post some photos up later, they're on the home PC.

[Aragorn]

The turbo DOES act as a silencer, just compare running a TDi with no exhaust, to an NAD with no exhaust and you'll quickly realise this!

But ofcourse it wont silence it enough to make it comfortable to drive daily. It does mean you can probably get away with one decent box, rather than needing two or three.

Otherwise your spot on, recover the flange from an old downpipe, or get one water jet cut, then get a piece of 2.5" pipe stretched out to mate with the 3"

Dirtydiesel: The stock factory TD5 rear section is 63mm.

[Landy-Novice]

i didn't mean to write straight through. i want i long silencer where the center box is.

thanks dan for the link, thats another one saved.

rick, if you could post the photos, that would be awesome.

thanks guys.

[vulcan bomber]

What makes you think you need a 3 inch exhaust? To big an exhaust reduces the exhaust gasses velocity, meaning the temps in the exhausthangs around... Possibly cooking your turbo.

[Aragorn]

I'm not sure thats really the case.

Fitting bigger freer flowing downpipe/exhaust should reduce the EGT's. Certainly does on the petrol Audi's i've seen which have EGT monitoring from the factory.

[reb78]

When we had this discussion on LRO before I had my stainless exhaust made, it was suggested that going too large actually impeded the exit of exhaust gases by increasing turbulence and thus decreasing velocity of the gas. It made sense to me.

My system is 2 inch downpipe (or whatever is determined by the turbo outlet and then 2.5 inch from there backwards. It works well - good spool up and not a lotta noise. The other thing with going for 'as big as I can fit' is the price. Price will increase the larger the diameter you go for, so if there is no need to go larger than 2.5 inch, then why pay for it??

[Boydie]

Reb is quite right, too large a diameter and you will cook the turbo, the velocity is too slow and the resulting turbulance causes a reverse harmonic which pushes the gas flow back into the head, talk to any motorcycle exhaust tuner in regard to this, they are the masters of high speed gas flow in engines. Getting the right dia. is a science and I'm not at all sure of how its calculated but I wouldnt be going up to 3".

[Aragorn]

Pulse reversion? AFTER the turbine? Dont talk rubbish!

Any gas flow pulses are completely destroyed in the turbine housing, they essentially dont exist after the turbocharger. Trying to apply motorcycle, or any other Naturally Aspirated engine exhaust tuning principles to a turbocharged engine is completely pointless.

After the turbo, you want the gasses out with as little resistance as possible. That means a big, free flowing pipe. FLOW matters more than PRESSURE once your past the turbo. PRESSURE impedes the turbine to do its job, meaning you need MORE pressure on the other side of the turbine (ie in the exhaust manifold) to do the same work.

Less back pressure after the turbo means the turbo works more efficiently, and produces LESS heat. You WILL NOT see an increase in pre-turbo EGT's by fitting a larger free flowing downpipe. They will decrease if the downpipe was restricting things, or remain the same if it was not.

On a standard TDI, 2.5inch is likely plenty, however if you fancy tuning the engine, theres no harm in going larger.

[andy2986]

Pulse reversion? AFTER the turbine? Dont talk rubbish!

Any gas flow pulses are completely destroyed in the turbine housing, they essentially dont exist after the turbocharger. Trying to apply motorcycle, or any other Naturally Aspirated engine exhaust tuning principles to a turbocharged engine is completely pointless.

After the turbo, you want the gasses out with as little resistance as possible. That means a big, free flowing pipe. FLOW matters more than PRESSURE once your past the turbo. PRESSURE impedes the turbine to do its job, meaning you need MORE pressure on the other side of the turbine (ie in the exhaust manifold) to do the same work.

Less back pressure after the turbo means the turbo works more efficiently, and produces LESS heat. You WILL NOT see an increase in pre-turbo EGT's by fitting a larger free flowing downpipe. They will decrease if the downpipe was restricting things, or remain the same if it was not.

On a standard TDI, 2.5inch is likely plenty, however if you fancy tuning the engine, theres no harm in going larger.

Kinda glad you said that I bought a 3"stainless system from Griffin exhausts a while back, haven't got round to fitting it yet though, hopefully should have it on by next week.....

[Eightpot]

You can use standard pipes, if you can do a little welding.

You can use a standard 300TDi downpipe, it needs shortening by 170mm if using LT77 gearbox. If you remove the 170mm section just after the bend where the pipe is on a slight decline, it will also shorten the height of the pipe, allowing it to pass over the gearbox crossmember, so long as you are careful gettingthe angle of the pipes right when welding it back up. I use the 170mm section as a sleeve to join the two halves of downpipe together (slit a section out, roll it a little tighter and push it inside the pipe) which helps keep it in place while welding and reduces blowthrough.

Sometimes the downpipe still interferes with the crossmember, i usually notch a section out.

From there backwards you can then use normal pipes, though you'll more than likely need to add a couple of brackets.

[bkgonefishin]

back in the states I have 5" pipe on a cummins 6 cylinder. I monitor gas temps and when I installed the exhaust it dropped tons.

3 in should make a little difference in your EGT's improving performance as well.

[Boydie]

Have it your own wayn Aragorn, but any bend in the exhaust system will produce a harmonic - with or without a turbo, as for blowing turbo's talk to your own UK Subaru STI people - they melted a lot of them on their rally cars before they worked that out - so did we over here with Diahatsu turbo GTi's - bigger isnt always better

[Aragorn]

Perhaps you'll believe a Garret engineer then? Probably not, but i'll post it anyway as i'm sure others will find the information useful:

http://www.tercelreference.com/tercel_info/turbo_exhaust_theory/turbo_exhaust_theory.html

[dirtydiesel]

Perhaps you'll believe a Garret engineer then? Probably not, but i'll post it anyway as i'm sure others will find the information useful:

http://www.tercelreference.com/tercel_info/turbo_exhaust_theory/turbo_exhaust_theory.html'>http://www.tercelreference.com/tercel_info/turbo_exhaust_theory/turbo_exhaust_theory.html

Excellent link.

[pat_pending]

There is a principal in tuning that states a component doesn't need altering until it becomes restrictive.

IMO it's possible to tune a tdi to the point of unreliability before the standard exhaust becomes a problem

Obviously if you have a knackered system on there at the moment, replace it, but the cost and effort of going 3" is just not worth it.

The one thing you can guarantee with a noisy big bore pipe is that you'll think you're going faster.

[Aragorn]

Indeed.

That link suggests 250hp is about the limit for 2.5" pipe to pose no restriction, which agrees with my own experiences. Bear in mind however that the AFR that a diesel runs at means that typically it consumes 25-50% more air (and as such produces the equivalent increase in exhaust gas) than an equivalent petrol turbo producing the same output.

I'd imagine that a free flowing 2.5" system with well formed mandrel bends and straight thru boxes should be ok to ~200hp on a diesel, which like you say is beyond what most would try to tune a TDI to. If you've got a TD5 and are aiming for 200+ then a 3" downpipe at the very least would likely be a welcome addition.

That said, there is no HARM in going 3" (other than potential earache), and any reduction in backpressure it does provide will be a benefit.

[cackshifter]

It would be interesting to measure the back pressure under battle conditions - presumably a boss welded on the down pipe would enable one do it. Especially as the link suggests a small back pressure improvement is worth looking for as it is multiplied by the turbo pressure ratio.

[CwazyWabbit]

All things being equal would this be evidenced in any other way? For example would there be an effect on EGT's?

[Aragorn]

EGT's would likely drop, as less back pressure means the engines VE improves, meaning more airflow for a given fuel quantity thus lower temperatures. This is why i made the earlier comments about a bigger exhaust somehow melting the turbo makes no sense.

As the chap with the cummins above notes, EGT's fell when he installed his 5" pipe (albeit on a much larger engine, hence the size).

And yes, it is possible to monitor exhaust pressure, though i've never heard of anyone testing post-turbo pressure, exhaust manifold pressures can often hit 2-2.5 times the inlet manifold pressure on a highly tuned engine. Often causes problems with keeping the wastegate penny closed!

[CwazyWabbit]

Cheers for that I'll be swapping my exhaust over in a few weeks from the standard one that is on there to a more free flowing one, I shall make a note of the current EGT's on a few local test hills before and after the swap to see what difference it makes to a 300 TDI

[Aragorn]

good idea, useful to have real-world figures!

[Adam001]

2.5" is fine on any TDI... All science aside...it's not exactly a powerful high performance engine even if you do shove a VNT and thousands of pounds of kit on it! 3" is just plain overkill, it'll just be louder you won't get any gains.

I run 2.5" on a 110 with no silencers and smooth large radius mandrel bends,

I had a bodged straight through TD system before and if you were cruising along you could not hear it inside, only if you put the window down and floored it. But it was messy and it did suffer for it.

[rick]

FFS a lot of **** gets spewed about on forums.....

I've read and been told a 3" exhaust will definitely lead to turbine overspeed and the turbine and/or compressor will rev into oblivion, (can happen in theory, highly unlikely with an inefficient T250-4) that the big pipe will cook the turbo, (what ??!!) that.....

The facts.

Stock pump fueling, 255/85-16 tyres, digital pyro in exhaust manifold, highest EGT ever recorded on hills around here at WOT, 5th gear, 2.5km long climb, 180m altitude gain, 900m ASL at gap, 623*C max EGT.

Another mountain pass near here, approx 250-300m ascent buta lot steeper and lots of switchbacks, most all of climb in 2nd, 623*C.

Fitted 3" exhaust, much wider rev band through the gears.

Previously 3rd woould peak at 75km/h, 80km/h and it would just stop revving.

New exhaust, hit 100km/h in 3rd up a hill. (yes I'm mechanically insensitive, I used to race open wheelers )

Still ocaisonally take it to 90-95km/h if situation demands so obviously a huge decrease in backpressure. remember, this is a long 130 system too, so higher duct frictional losses than a 90 or 110.

Max. EGT's dropped to around 598* max. recorded temp. which confirms huge backpressure drop which gave more scope for increased fuel/pump settings.

Pump adjusted very soon after pipe fitted, can now exceed 750* on climbs if I don't abck off.

Over 7 years later and the engine now has 304,000km and it's all still together, no bangs from the little Garrett.

Yes, 3" is overkill on a Tdi, but 2.75" pipe was stupidly exxy here at the time and I didn't want to make a 2.5" system from scratch and find I had bugger all improvement.

I will dig the photos up