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+--- Thread: NO EXHAUST......ok? (/showthread.php?tid=4969)
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NO EXHAUST......ok? - ANTB1986 - 18-07-2012
How much harm will it do if I completely removed the exhaust off my hdi? Seen people do it and was seeing if its ok to take it and drive. Cat back removed i was thinking.
RE: NO EXHAUST......ok? - lolsteve - 18-07-2012
Drvien from leeds to southampton with no backbox on with no issues, only thing I can think of is if you're sat idleing the hot gases might melt any plastics/wires above it but that'd be worse case I think like if you were sat there 10 mins with a hot engine
RE: NO EXHAUST......ok? - Toms306 - 18-07-2012
I think its illegal not to have an exhaust!
I drove around for a week or so with no exhaust from the turbo with no problems.......sounded cool, until it shat its oil everywhere, pretty sure it was totally unrelated though lol.
RE: NO EXHAUST......ok? - ANTB1986 - 18-07-2012
Was thinking that myself mate. My friend is thinking of ripping it off later and asked me to get some feedback before he does it. I had my backbox off for 6 months and not probs aswel.
Ha ha turbo on it's way out or something?
RE: NO EXHAUST......ok? - Toms306 - 18-07-2012
(18-07-2012, 08:17 AM)ANTB1986 Wrote: Ha ha turbo on it's way out or something?
Erm, ya could say that!
Replaced it now though, and done a decat while I was there. Just one box now and sounds alright. 
RE: NO EXHAUST......ok? - ANTB1986 - 18-07-2012
I will tell him to just do it then lol
RE: NO EXHAUST......ok? - HDIkyle - 18-07-2012
It won't do any harm but you will be down on power and it will fill the cab with fumes when you are sat. Does dounds awesome tho
RE: NO EXHAUST......ok? - ANTB1986 - 18-07-2012
How much pier will it loose do you know?
RE: NO EXHAUST......ok? - Ruan - 18-07-2012
Shouldn't lose any power, it's not a petrol...
It'll sound awesome, fill the cabin with gasses if you have a leaky boot floor like most 306s do... I've driven for months before now with no exhaust, they're pretty quiet unless you've got your foot down anyway, much quieter than a Petrol equivalent anyway.
But it is illegal, yes...
RE: NO EXHAUST......ok? - THE_Liam - 18-07-2012
It shouldn't make a difference to power, it will on a petrol because they need back pressure but on a diesel you just want to get the gases out as fast as possible so if anything it will have a touch more power...
Never driven a diesel with no exhaust, but I once had a ride in a gen 3 Camaro 350ci with no exhaust...
I came slightly
RE: NO EXHAUST......ok? - ANTB1986 - 18-07-2012
How will the gases go inthe boot if their ain't gna be an exhaust on it as I'm talking about cat back, remove the hole exhaust not just the backbox
RE: NO EXHAUST......ok? - samass - 18-07-2012
cuz theyll get sucked up in and around the car as you're driving along, the air get very turbulent and as the gases arent getting stuck right out the back, you'll get fumes in the cabin.
even when i had no back box on my 106 i got fumes inside, and on my 306, where the exhaust kinda just points at the bumper, instead of underneath it, i get fumes when sitting still with the engine running
RE: NO EXHAUST......ok? - Eeyore - 18-07-2012
(18-07-2012, 08:50 AM)ANTB1986 Wrote: How much pier will it loose do you know?
lots... i removed mine and lost about 95% of Brighton pier
![[Image: 800px-England_-_Brighton_-_West_Pier_1.jpg]](http://upload.wikimedia.org/wikipedia/commons/thumb/0/08/England_-_Brighton_-_West_Pier_1.jpg/800px-England_-_Brighton_-_West_Pier_1.jpg)
RE: NO EXHAUST......ok? - THE_Liam - 18-07-2012
(18-07-2012, 09:16 AM)ANTB1986 Wrote: How will the gases go inthe boot if their ain't gna be an exhaust on it as I'm talking about cat back, remove the hole exhaust not just the backbox
It's because of the aerodynamics. Air passing under the car will draw the fumes straight up against the floor, and if you have any holes, cracks or gaps in the floor the fumes will be pushed straight up into them and into the cabin. Most 306's have leaky boot floors, so that's most likely what will happen. Ever notice when it's pissing down you always end up with filth all over the back of your car? That's road grime being pulled along the floorpan then shooting straight up as soon as it passed the rear bumper
RE: NO EXHAUST......ok? - ANTB1986 - 18-07-2012
Fill the boot holes? Lol
RE: NO EXHAUST......ok? - samass - 18-07-2012
side exit?
RE: NO EXHAUST......ok? - ANTB1986 - 18-07-2012
So will it lose power and undercoat the under of the car? I will tell him to drive with the windows open lol
RE: NO EXHAUST......ok? - Mr Whippy - 18-07-2012
I've been in a Td without a back box (fell off on motorway), and I was a passenger in the back and it was getting horrible within a minute and we needed to have windows wide open to not feel sick etc.
People in front have their vents and stuff so it doesn't seem as bad there
So yeah, illegal for a good reason, you could end up killing yourself or passengers with carbon monoxide poisoning or possibly co2 asphyxiation... oh dear
Dave
RE: NO EXHAUST......ok? - ginge191 - 18-07-2012
(18-07-2012, 09:18 AM)samass Wrote: cuz theyll get sucked up in and around the car as you're driving along, the air get very turbulent and as the gases arent getting stuck right out the back, you'll get fumes in the cabin.
RE: NO EXHAUST......ok? - samass - 18-07-2012
*this also happens when your fire ring is FUBAR...
RE: NO EXHAUST......ok? - HDIkyle - 18-07-2012
Both mine and sams hdi stage 1 and 2 def lack power with no exhaust on so does make some difference
RE: NO EXHAUST......ok? - Ruan - 18-07-2012
Mine goes like absolute f*ck with no exhaust, it's more laggy and hasn't got as much off boost torque...
On boost it's much more violent with no exhaust...
RE: NO EXHAUST......ok? - Toms306 - 18-07-2012
(18-07-2012, 02:25 PM)Ruan Wrote: Mine goes like absolute f*ck with no exhaust, it's more laggy and hasn't got as much off boost torque...
On boost it's much more violent with no exhaust...
Would a decat give those same things?? I've been blaming the bigger turbo for my comlplete lack of low end torque and extra lagginess..........wondering if it was the decat that done it now though, as they were put on the same time.
I was under the impression diesels didnt need any back pressure though....or is it due to the turbo that doesnt need backpressure, so offboost it does need some??? 
RE: NO EXHAUST......ok? - 4WayDiablo - 18-07-2012
Optimum exhaust length for a diesel turbo is 18 inches IIRC
Stack out the bonnet yO?
RE: NO EXHAUST......ok? - HDIkyle - 18-07-2012
Mine struggled in top half of the revs where it usually pulls well uto the limit it was just breathless once on boost
RE: NO EXHAUST......ok? - kyleo92 - 18-07-2012
When my backbox fell off doing 80 on the m1 I put off having a new one for as long as possible as the sound was pretty epic... Didn't Affect my performance or fuel economy
RE: NO EXHAUST......ok? - THE_Liam - 18-07-2012
(18-07-2012, 05:52 PM)4WayDiablo Wrote: Optimum exhaust length for a diesel turbo is 18 inches IIRC
Stack out the bonnet yO?
As long as you don't mind not being able to see where your going off boost
RE: NO EXHAUST......ok? - Ruan - 19-07-2012
The optimum length for a turbocharged engine is straight out the turbine wheel...
There's no pulse tuning or resonance to scavenge the cylinders of their gasses past the turbine wheel.. Before the turbine wheel if you have equal length runners you might see a slight gain, but obviously the turbine wheel is what causes the back pressure...
It's really a myth that an engine needs backpressure to make *power*... It needs the least amount of backpressure to make it's *PEAK* power - wherever that is in the RPM band, but as always with engines, it's a compromise, you want the backpressure there to prevent the valve overlap from sending half the mixture out the exhaust at low RPMs to keep up the midrange torque, but unrestrictive enough at high RPMs to allow the valve overlap to keep gas velocity up to let inertia keep pulling the gasses out the cylinders after TDC combined with the pulse tuning of the exhaust.
When gasses exit past the valve, their velocity is very high, the higher the engine speed, the more the velocity of the gas goes up... When you send a gas very quick through an orifice, even after you stop the force that caused the gas to want to exit the cylinder (the piston returning back up the bore...) it'll want to pull some extra gas with it - the inertia effect...
RE: NO EXHAUST......ok? - ginge191 - 19-07-2012
(18-07-2012, 09:49 AM)samass Wrote: *this also happens when your fire ring is FUBAR...
I now know the fire ring is still decent; the back box had come off along time ago and leaking into the cabin; we must have broken it when we changed the turbo
RE: NO EXHAUST......ok? - lolsteve - 19-07-2012
How about a standard/sports exhaust for low rpms then when you start reaching higher rpm a valve/port opens near turbo that vents out the increased gasses and then closes when foot is off throttle
All theological though