Blowing exhaust and back pressure

[muddyjames]

I have been told that if a diesel car doesnt have an exhaust it wont run at all as there is no back pressure. I know my exhaust has a few ponts it is blowing from but not bad enough to fail mot. Will this reduce the engine power and economy or was my mate talking rubbish?

[muddysteve]

when the downpipe broke on my clio the other day it was bloody noisey but did run, it was a pig to start though (1.9 normaly aspirated)

my rangie 200tdi when the exhaust fell off just past the 1st silencer it wasnt too noisey and went like stink (was tempeted to keep it like it)

so to sumarize, your mate was talking sense as alot of petrol engines and normaly aspirated diesels need a bit of back pressure but a tdi wants as little back pressure as possible

[extreme90]

as little back pressure as u can so tubby spins up alot quicker  
mine a straight through 65mm, no silencers  :lol:
danny

[muddyjames]

So when I get a proper exhaust on with no holes it will go slower very slightly :(

I have also been told a 110 exhaust will fit my disco and easier to fit or something.

[extreme90]

unless theyre gr8 big whacking holes ur never going to no
u need half the exhaust to  be missing really too notice any difference
danny

[muddyjames]

They arent big whacking holes as they passed the MOT like it. I thought any blow in the exhaust was an mot failure but obviously not!

So is there any truth in that a 110 exhaust fits better or any advantages to it?

[extreme90]

cant see what the difference is  :?
i seen 110 exhausts before and i cand say they would fit better  :?
dont no what all that about, they same size bore and fitting wise they completely diff shape
danny

[rollazuki]

If possible throw the exhaust away from the turbo backwards :lol:
sounds great.

Unless an exhaust system or manifold is a 'tuned' length, then youre not gonna suffer from changes in backpressure. Youre probably gonna let the motor breath a bit more easily if the system is shortened. The problem with holes in the zorst is that they let exhaust out, AND air in, causing pops and crackles, and maybe making flow worse.

[Xtremeteam]

a defender 300tdi front pipe should fit as it has no particle collector or flexi joint,

[Range Rover Blues]

KNowing Land Rover it's probably the same part.

[MartinV8]

A normally aspirated engine relies on a tuned exhaust length & bore combination for optimum performance as the momentum of the exhaust gases in the exhaust will suck the burnt mixture through the exhaust port rather than absorbing engine power by pushing them out. On a turbo engine the less back pressure the better as previously stated. This lets the turbo spin much more easily and hence more ponies. The power absorbed by the engine pushing the gases out of the cylinder is neglible when compared to the huge benefit of the turbo spinning nice and freely. This is why you see all the jap turbo cars with big bore exhausts.
Remember seeing a 90 in one of the mags, think it was French and called Xtreme, it had a small stubby pipe exiting behind front wheel with no silencers. Ran big boost and went like the brown stuff off a shovel!


Martin