cookie64 Posted January 3, 2012 Share Posted January 3, 2012 Hi all Happy new year I'm currently looking at putting a side exit exhaust on to my 300tdi truck but am not sure weather diesels need exhaust back pressure or not to run efficiently like petrols do. It currently has no cat or backbox only the middle box which i was debating taking out to do the mods Thanks Tom Quote Link to comment Share on other sites More sharing options...
cookie64 Posted January 3, 2012 Author Share Posted January 3, 2012 Darn forgot the actual question lol So does my truck need the center box or can it be a straight through exhaust? Note: I don't care if it's loud and was thinking of sticking the end out through the panel just infront of the passenger side rear wheel Quote Link to comment Share on other sites More sharing options...
nicks90 Posted January 3, 2012 Share Posted January 3, 2012 no, you dont need back pressure in the exhaust. You have a turbo that does all that for you anyway. If anything, having back pressure after the turbo will slow the spool up time of the turbo. Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted January 3, 2012 Share Posted January 3, 2012 Indeed. You say you don't care if it's loud, but after driving it for a while I'm sure you will Quote Link to comment Share on other sites More sharing options...
mark-d Posted January 3, 2012 Share Posted January 3, 2012 yep the turbo gives enough back pressure, it is quite a bit louder without the centre box though Quote Link to comment Share on other sites More sharing options...
Disco-Ron Posted January 3, 2012 Share Posted January 3, 2012 I tried my 300 without any silencers, well, far too loud, it was changed within 24hrs . . . And i don't use my truck much, and i still couldn't live with it! Quote Link to comment Share on other sites More sharing options...
chris-b Posted January 3, 2012 Share Posted January 3, 2012 I have run my 300 truck cab 90 with a straight through exhaust exiting just behind the passenger door for 4 years now, off road is fine but after 10 mins on a dual carrageway your passenger will suffer some form of industrial deafness. Quote Link to comment Share on other sites More sharing options...
Tom1809 Posted January 3, 2012 Share Posted January 3, 2012 With my 90 straight through my in cab db went from 78 to 91, its something to bare in mind bit it did sound nice and make a difference in low down grunt as it was spooling up quicker. Quote Link to comment Share on other sites More sharing options...
RILEY Posted January 3, 2012 Share Posted January 3, 2012 Hi mate removed my centre box (straight thro pipe) kept rear sounded ok seamed to improve performance (pump also tweaked ) one new X-member later i was on straight thru . Drove as flat as a fart noisey and slower i put the centre box back ,not as quick as when the centre was out but a straight thru IS to loud, sounds Turd, Turns heads for all the wrong reasons Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted January 3, 2012 Share Posted January 3, 2012 Back pressure is a mith: http://en.wikipedia.org/wiki/Back_pressure However. as strange as this will sound, to run silencer free, you will need to turn the pump up a bit to give the turbo some pressure to work against. I ran my 200 silencer free for a bit, it went well, and does no worse with the remains of the little silencer in the system (thats a story on its own). Quote Link to comment Share on other sites More sharing options...
smokinv8 Posted January 3, 2012 Share Posted January 3, 2012 Mate of mine has de-catted and de-silenced his 300tdi and I thought I might do the same to my 200 but after a day out in his the other day it got on my nerves that amount of noise. Ok on play days but not for greenlaning in my opinion. Mates contemplating putting the cat back in to see how much it would quieten down. Quote Link to comment Share on other sites More sharing options...
Disco-Ron Posted January 3, 2012 Share Posted January 3, 2012 Mate of mine has de-catted and de-silenced his 300tdi and I thought I might do the same to my 200 but after a day out in his the other day it got on my nerves that amount of noise. Ok on play days but not for greenlaning in my opinion. Mates contemplating putting the cat back in to see how much it would quieten down. I would advise a small silencer rather than the cat, a silencer is still free flowing.... a cat is like sticking a potatoe up the exhuast!! Quote Link to comment Share on other sites More sharing options...
TurboBen Posted January 4, 2012 Share Posted January 4, 2012 My exhaust exits just behind the passenger door, only has the small box and i don't find it too loud, i only use my 90 as a toy suppose if i used it every day it may be different, Even the girlfriend doesn't complain so it can't be that bad!! Quote Link to comment Share on other sites More sharing options...
nige90 Posted January 5, 2012 Share Posted January 5, 2012 There's a strange idea out there that back pressure is needed but as Vulcan Bomber correctly says it's a myth. Why would you want resistance in the exhaust ? The only thing it will do is reduce the ability to empty the cylinders of exhaust gasses. A properly designed exhaust system will actually have a negative pressure at the valve in order to suck the cylinder clean. Each time a cylinder fires a volume of fast moving high pressure gas blasts down the exhaust creating a vacuum behind it, known as the Venturi effect ( a bit like a slipstream behind a truck ). Google "Pulse Wave Tuning". I've removed the back box from my 90 as I can't believe a box that has the gas enter and exit on the same end forcing it to u-turn can be anything but a bad thing but have kept the middle box nd have the tailpipe exiting through the rear wing just behind the NSR wheel. It's not loud but had a nice deep growl and even with the ragtop back window open don't get complaints from people in the back. Quote Link to comment Share on other sites More sharing options...
ToyRoverlander Posted January 5, 2012 Share Posted January 5, 2012 Found this a while back.. The following excerpts are from Jay Kavanaugh, a turbosystems engineer at Garret, responding to a thread on Impreza.net regarding exhaust design and exhaust theory: “Howdy, This thread was brought to my attention by a friend of mine in hopes of shedding some light on the issue of exhaust size selection for turbocharged vehicles. Most of the facts have been covered already. FWIW I'm an turbocharger development engineer for Garrett Engine Boosting Systems. N/A cars: As most of you know, the design of turbo exhaust systems runs counter to exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. There is a happy medium here. For turbo cars, you throw all that out the window. You want the exhaust velocity to be high upstream of the turbine (i.e. in the header). You'll notice that primaries of turbo headers are smaller diameter than those of an n/a car of two-thirds the horsepower. The idea is to get the exhaust velocity up quickly, to get the turbo spooling as early as possible. Here, getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging. The scavenging effects are small compared to what you'd get if you just got boost sooner instead. You have a turbo; you want boost. Just don't go so small on the header's primary diameter that you choke off the high end. Downstream of the turbine (aka the turboback exhaust), you want the least backpressure possible. No ifs, ands, or buts. Stick a Hoover on the tailpipe if you can. The general rule of "larger is better" (to the point of diminishing returns) of turboback exhausts is valid. Here, the idea is to minimize the pressure downstream of the turbine in order to make the most effective use of the pressure that is being generated upstream of the turbine. Remember, a turbine operates via a pressure ratio. For a given turbine inlet pressure, you will get the highest pressure ratio across the turbine when you have the lowest possible discharge pressure. This means the turbine is able to do the most amount of work possible (i.e. drive the compressor and make boost) with the available inlet pressure. Again, less pressure downstream of the turbine is goodness. This approach minimizes the time-to-boost (maximizes boost response) and will improve engine VE throughout the rev range. Quote Link to comment Share on other sites More sharing options...
nicks90 Posted January 5, 2012 Share Posted January 5, 2012 good find - finally lays the myth to bed on turbo charged engines! Quote Link to comment Share on other sites More sharing options...
lrfarmer Posted January 5, 2012 Share Posted January 5, 2012 Mate of mine has de-catted and de-silenced his 300tdi and I thought I might do the same to my 200 but after a day out in his the other day it got on my nerves that amount of noise. Ok on play days but not for greenlaning in my opinion. Mates contemplating putting the cat back in to see how much it would quieten down. i've taken the center box out on mine and left the rear box it's change the tone but not much louder, Pickup was alot better Quote Link to comment Share on other sites More sharing options...
Disco-Ron Posted January 5, 2012 Share Posted January 5, 2012 When i tried mine with no silencer, i decided i wanted to change the position of the exit, but i didn;t want it as a side exit, as i donlt like the idea of throwing soot over pedestrians..... so mine exits to the right of the tow bart, pointing downwards, it doesn't protrude beyond the towbar brace bars..... it now goes over the axle as per original, then goes straight back a little, then 90deg towards the drivers side, then another 90deg this time pointing downwards........ works for me.. plus i don;t get sooty when i stand by the back door, hence why i crossed it over to the drivers side.... Quote Link to comment Share on other sites More sharing options...
rick Posted January 7, 2012 Share Posted January 7, 2012 You fella's reckon a standard 300Tdi exhaust is loud sans silencers. You should hear a 3" 300Tdi system without any silencers whatsoever Nasty is the only word that comes to mind, and not in a good way. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.