Exhaust on 300tdi

[110 Pete]

Hello all,

I am planning on getting a straight through exhaust put on my 1994 300tdi Defender but I am not quite sure what size and what configuration to go for.

I am tossing up between 2.5" or 3" Straight through pipe. Would the 3" have too little back pressure resulting in MORE turbo lag?
I am after the turbo to spool up faster (i realy want it to be spooling slightly when idleing like when I took my centre box out for a clean and ran it with the pipe straignt from the turbo ). I am also after better low end torque and less turbo lag.

I do not want the exhaust to drone when cruising on the Highway but I would still like it to sound a bit meatier than stock. Should I run a Hotdog on the tip or a straight through Muffler on the end?

Anyone who has done this your advice would be much apreciated.

Cheers

Pete

[weeds]

i went for 2.5" normal bend with no mufflers, cheap as chips........

i believe the turbo spools up quicker but hard to tell what if any increase in power and torque...........without putting your rig on a dyno before and after your exhaust mods i say most guys want to bleieve there is an increase just because they have done the mod. i have had mine dyno'd a couple of times but never before and after each mod

do you monitor EGT's? if you have tweaked the fuel pump i would suggest installing an EGT guage

I should have kept the resinator which sits behind the rear wheel, as i can hear the 'drone' if the rear passanger window is down, more so on freeways when there is concrete barriers beside you. Its not really that bad and i have gotten used to it

[110 Pete]

i went for 2.5" normal bend with no mufflers, cheap as chips........

i believe the turbo spools up quicker but hard to tell what if any increase in power and torque...........without putting your rig on a dyno before and after your exhaust mods i say most guys want to bleieve there is an increase just because they have done the mod. i have had mine dyno'd a couple of times but never before and after each mod

do you monitor EGT's? if you have tweaked the fuel pump i would suggest installing an EGT guage

I should have kept the resinator which sits behind the rear wheel, as i can hear the 'drone' if the rear passanger window is down, more so on freeways when there is concrete barriers beside you. Its not really that bad and i have gotten used to it

Hi Weeds,

Thanks for the helpful reply! A few questions does your turbo spool on idle and is your drone bad just on the highway?? Is it heard in the cab and reverberates?

I am going to get an egt gauge as soon as possible but I am also getting a straight through to lower the temp as my fuel pump has been tweeked and my turbo is already spooling up fast.

Oh and is the exhaust note deeper and meatier than with stock, if you get what I mean :P

Cheers

[weeds]

A few questions does your turbo spool on idle i don't believe so
Is your drone bad just on the highway?? yes >90km/hr
Is it heard in the cab and reverberates? only heard if the rear window is down, if front passenger window is done you can just hear it

I am going to get an egt gauge as soon as possible but I am also getting a straight through to lower the temp as my fuel pump has been tweeked and my turbo is already spooling up fast.

Oh and is the exhaust note deeper and meatier than with stock, if you get what I mean :P there is an increase in noise.....i haven't really heard it as when my girlfriend drives off she doesn't really put the boot in

Cheers

HTH

[Landie333]

I am tossing up between 2.5" or 3" Straight through pipe. Would the 3" have too little back pressure resulting in MORE turbo lag?
I am after the turbo to spool up faster (i realy want it to be spooling slightly when idleing like when I took my centre box out for a clean and ran it with the pipe straignt from the turbo ). I am also after better low end torque and less turbo lag.

In a forced induction engine, the backpressure of the exhaust is created by the turbo. The collector is before the turbo which is where your scavenging effect is created.

After the turbo, you pretty much want the gasses gone ASAP. Backpressure after the turbo isn't good, but having the largest exhaust isn't great either. You want the compromise between backpressure and gas velocity.

For a forced induction engine after the turbo, gas velocity is important. Whereas in a naturally aspirated engine, backpressure is more important. Realisitcally, a transitioned 3'' turbo back would be a good size. Plenty of people run 3'' on 2-2.5L engines with good results.

Things to consider with an exhaust is firstly, transitioning. the turbine housing, for example, may be 2.5" putting a 3'' straight into that will cause a drop in gas velocity resulting in higher temperatures (at that point) The lowering of gas velocity means you are effectively creating backpressure aswell.
Secondly, Bends. Mandrel bends are more effective as the bends are smooth. Not with low and high points through the bend. Results are the same as above. On that aswell, the radius of the bends is important. Having sharp bends results in gas velocity slowing. The straighter the bends, the more efficient it should be.

If you are looking at doing it yourself, have a look at this website:
Tube Bending & Fabrication - Columbia River Mandrel Bending
I havn't personally used them YET. But I know of people that have and have made nice exhuasts out of them.

Keep us posted

[dromader driver]

I put a hot dog in to replace the under floor muffler after it fatigue cracked. Definitely pulls better on my calibration hill. The kids have a spare cannon kicking around that I keep threatening to put on instead of the rear resonator.

Exhaust is off at the moment for a clutch fork change and it was very interesting to see the thickness of soot inside the pipes.

Will be interesting to see what that sounds like with the cannon.

[newhue]

Isn't standard 60mm diameter, so a 2.5" is basically the same. I know I put a 2 and 3/4" on a 3l to replace the original 2" system and the results were minimal. It held itself better on hills parhaps, but that was the only noticible effect, apart from more drone and the $1100 bill.

To put it in context, I just bought a second hand tail pipe for a Tdi for $50.

[weeds]

my straight through cost $200 band new, i wasn't really looking for performance just wanted a simple exhaust........oh the main reason for fitting it was to accomodate my PTO drive

[110 Pete]

my straight through cost $200 band new, i wasn't really looking for performance just wanted a simple exhaust........oh the main reason for fitting it was to accomodate my PTO drive

Weeds, how did you get it so Cheap!! Ive been quote $600 3" straight through with Hotdog on the end with madrel bends! Ive also been quoted $1200 which I thought was ridiculous as i only asked for a pipe, no mufflers or anything!!

Landie333, that was very helpful!! So you would put a 3" on the 300tdi?? Id love to build my own exhaust, only problem is I cant weld

Dromader Driver, tell me more about your system!


Thanks guys

Pete

[Landie333]

Landie333, that was very helpful!! So you would put a 3" on the 300tdi?? Id love to build my own exhaust, only problem is I cant weld

From what i've seen on other makes (predominatly petrol engines) 2-2.5L forced induction engines have had good results with 2.5'' and slightly moreso 3'' exhausts. I've never played with exhausts on 300TDIs, so I can't comment on what effect it will have on a 300.

I had a chart somewhere showing the theoretical exhaust sizings in relation to engine size and I can't find it. But from memory, 2.5'' was upto about 3ish Litre engines. If my memory serves me correctly.

Buy a cheap welder (if you can afford it) and learn. The only way you will learn is by doing it. Atleast with a supplier like Mandrel Bends, you can buy plenty of bits, destroy them and still not have spent too much.

A thing to consider, measuring up the lengths you need, purchasing the bits from them and then paying someone to weld it up. $1100 for a exhaust sounds right, but so does $200. It really depends on where you go and who you know. Shop around.