How much exhaust back pressure?- TD42

[patrol_maverick]

I've got a TD42 with extractors and a 2.5 inch system but I'm after the same deep sound as a turbo TD with 3 inch exhaust (obviously I won't have the turbo whistle sound). I'm looking at shortening the system- I'm going to put a 45 degree bend off the back of the muffler so the exhaust blows under the back diff. (or remove the muffler and just go straight into a 45 bend) The reason for doing this is simply to make it sound better (sound deeper & louder).

Anyway like the title says, How much back pressure do I need? I don't want to run lean due to excessive air flow and also I don't want burnt valves.(do diesels have this problem or have I been misinformed?) Also looking at spending as little as possible, so don't suggest a turbo and big exhaust, it's not going to happen.
Thanks

[RIZZO]

Mate at the end of the day its still not goin to sound as deep or nice as a turboed donk. In your situation i'd go straight through pipe from manifold as large as possible within your budget, as for burning valves out I have never heard of this happenin to 4.2 s with high flowed exhaust, there a tough donk. but sadly at the end of the day if you want you 4.2d to sound like a 4.2td simple - turbo it

[tweak'e]

turbo 4.2's with a straight through 3" are not all that loud. the turbo quietens them right down.

basically just need to play around with different muffler styles. i would still exit it at the rear, just use 3" from the rear muffler back.
i don't know how many mufflers your system has, it would probably pay to put a straight resonator/muffler through half way down the main pipe just to help get rid of some of the horrible diesel noise.
use a fairly big empty rear muffler should give you i nice note without sounding like a tractor with broken exhaust.
just a bit of trail and error with different mufflers to get the note right.

don't need to worry about valves or back pressure. its pretty much set by the extractors and first bit of exhaust up the first resonator.

[coxy321]

I'd just have a FULL straight through system (key word there being FULL), and get a "turbo" type muffler (Genie or similar) or quality resonator. Cutting your exhaust short is only going to cover the underside of the car in soot, and will most likely score you a canary at the next RBT station.

I ran a 3" mandrel bent MTQ system on my car before i put the turbo on, and it wasn't really loud at all.

Might pay to jump on some street car forums and have a dig around there for ideas.

PS. And no, you're car will never sound like a turbo diesel, as the turbo itself does most of the noise reduction there.

[patrol_maverick]

Thanks for the info. I'm not after the turbo whistle, I'm obiously not going to get it without a turbo. I'm just after that 'deep grunt' sound that some TD's have. My brother tried his with half of the standard exhaust with no mufflers, it sounds better.

Back to the point, Do diesels need much back pressure to operate properly? Like I said I don't want burnt valves. What's a pyro worth and where do you get them, I think it would be useful for comparing different setups. How high are the temps anyway? Maybe I could use my infrared temp gauge if it reads high enough.

[KiwiBacon]

They only way to burn valves on a diesel is to make it run very rich. You're not going to do that on a non turbo engine without first smoking out the entire neighbourhood.

[Clanky]

Diesels like low backpressure, especially turbo ones.
You cant damage the valves by taking the exhaust off. After all its only a compressor with a fuel stick in the top.
More fuel = more heat
Less fuel = less power
Mixture control is no different to putting you foot on or off the throttle

[patrol_maverick]

Diesels like low backpressure, especially turbo ones.

Sounds good, the exhaust place also said diesels only need a slight amount of back pressure.
Hopefully I get some improvement on sound, I guess I'll find out tomorrow when I'm done modding it.

[suggy126]

Hey bud, i've got a TD42 non turbo wagon and have recently had a set of extractors fitted with a 2.5 inch exhaust system with a straight through muffler, the muffler is basically under the back seats and a 45 mandrel bend somes out of the muffler and dumps, it doesn't have the turbo whistle but has a deep satisfying note to it, it really gives it that deep diesel note. Love the sound of it and goes hard for a non turbo too

[DEZ]

I've got a TD42 with extractors and a 2.5 inch system but I'm after the same deep sound as a turbo TD with 3 inch exhaust (obviously I won't have the turbo whistle sound). I'm looking at shortening the system- I'm going to put a 45 degree bend off the back of the muffler so the exhaust blows under the back diff. (or remove the muffler and just go straight into a 45 bend) The reason for doing this is simply to make it sound better (sound deeper & louder).

Ok i basicly have exactly what your saying. Extractors, 2.5inch exhaust, 1 straight through sport muffler and finishes just before rear diff with a 45 at the end and all above chassis. It's deffinatly got a nice deep note low and growls and higher revs. Where abouts in NSW are ya? Im around sydney PM if you want to check it out.

[patrol_maverick]

I done the exhaust today and it sounds good. I didn't loose too much back pressure either -I measured it before and after and it's only slightly less.

[KiwiBacon]

I done the exhaust today and it sounds good. I didn't loose too much back pressure either -I measured it before and after and it's only slightly less.

Out of curiousity, what was the pressure and how did you measure it?

[money_killer]

I done the exhaust today and it sounds good. I didn't loose too much back pressure either -I measured it before and after and it's only slightly less.

similar to my old one i have a vid of it at full noise too sounded good

[patrol_maverick]

Out of curiousity, what was the pressure and how did you measure it?

I made a gauge called a 'manometer' to check the pressure (see the pict). It's basically a clear piece of hose held to a board in a U-shape with some water in it and a scale drawn on it. One end of the tube goes to an outlet I put on the side of the exhaust. I used it more for a before/ after comparison, I haven't done the maths to work out the actual exhaust pressure.

These are the measurements I recorded (the water level rise in centimeters)- (1)Before/ Full exhaust, Idle +1cm/ 2000rpm +14cm/ 3000rpm lost the water -too much pressure. (2)Half exhaust with no muffler, Idle 0cm/ 2000rpm +2cm/ 3000rpm didn't bother testing. (3)Finished exhaust/ half exhaust with muffler & 3-inch tip- Idle +1cm/ 2000rpm +10cm/ 3000rpm +18cm.