Straight Through Exhaust a good idea???

bkingb

Active Member
Apr 29, 2012
191
0
kent
dont do decat as mot will fail also too loud for every day use sounds **** after a while
 

john_tdi

mmm 385lbft
Feb 21, 2007
687
0
s wales
decats on diesels pass. they are not tested. It's smoke only.

Its the back box which really dictates the sound. With it all removed it's obviously louder, but I didn't find it bad at all on motorways etc. It only became really loud on full chat.
 

Pimped up vario

Cordy Cruizer
Nov 20, 2009
1,291
0
Belfast N Ireland
I'll second that on the noise front. Mines 2 1/4 inch with no cat and one backbox and doesn't have any boomyness and isn't overly noisey. The overrun noise when you lift off the throttle is nice and hearing the turbo noise clearly down the exhaust pipe is always amusing. I hear it when the wife takes the car for a message.
 
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DarrenJ

Seat like you mean it!
Dec 3, 2008
470
0
Galway, Ireland
I did a decat and the smell is still terrible a year later.

It's far smokier in the morning and looks like it's overfueling.

What would be causing it to overfuel (thermostat and temp sensor are done and it's always serviced well etc.)
 
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DarrenJ

Seat like you mean it!
Dec 3, 2008
470
0
Galway, Ireland
Egr was cleaned 10k ago and since then was turned down to 1% function.

I have fitted an oil catch can too.

It's just something that's bugging me for a car @74k miles.

Egr was sticking after if was cleaned - open one minute and then closed and the exhuast note would change.
 

martin j.

Active Member
Feb 11, 2007
1,996
889
Fife
After following the wtcc and btcc for years I noticed that the diesel leons were unbelievably quiet under all conditions(usually loads of throttle) so noisy may not the the way to best power? surely competition building guys would know best, could there be any replica kits out there?
 

andypandypoos

Rodeo Monkey
Feb 14, 2009
319
0
Cowley, Oxford
After following the wtcc and btcc for years I noticed that the diesel leons were unbelievably quiet under all conditions(usually loads of throttle) so noisy may not the the way to best power? surely competition building guys would know best, could there be any replica kits out there?

they have to abide by all sorts of regulations, including noise limits?
 

john_tdi

mmm 385lbft
Feb 21, 2007
687
0
s wales
Egr was cleaned 10k ago and since then was turned down to 1% function.

I have fitted an oil catch can too.

It's just something that's bugging me for a car @74k miles.

Egr was sticking after if was cleaned - open one minute and then closed and the exhuast note would change.

if it was sticking, change it for a allard power pipe or something like it maybe?!
 
Apr 13, 2011
1,971
1
hull
Egr was cleaned 10k ago and since then was turned down to 1% function.

I have fitted an oil catch can too.

It's just something that's bugging me for a car @74k miles.

Egr was sticking after if was cleaned - open one minute and then closed and the exhuast note would change.

U say u have a custom catch tank. The Reason am asking is because the pd engine if that's what u have has a lot of crankcase oil pressure and require a lot of breathing.

And if its not breathing enough it can cause it too over fuel so I'd defo start by cheaking out ur engine breather system.
 
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DarrenJ

Seat like you mean it!
Dec 3, 2008
470
0
Galway, Ireland
U say u have a custom catch tank. The Reason am asking is because the pd engine if that's what u have has a lot of crankcase oil pressure and require a lot of breathing.

And if its not breathing enough it can cause it too over fuel so I'd defo start by cheaking out ur engine breather system.


I made the tank myself with the correct width 19mm pipes and inserts so it breathes properly.
Even before the tank it threw out clouds of greyish blue smoke and stunk around the car after decat at 63k miles.

I'd just like to sort out the problem getting sick of it!
 

DarrenJ

Seat like you mean it!
Dec 3, 2008
470
0
Galway, Ireland
if it was sticking, change it for a allard power pipe or something like it maybe?!

Since the map I have disconnected the EGR vac pipe as the fault code is deleted from the map.

It still throws out far too much smoke and stinks around the car even when it's fully warm.

I don't think the injector loom or injectors are faulty and all heater plugs are working and I checked the resistance - all within proper values.

It's good on diesel and I can easily get 60mpg on national roads doing a 60/70 mile trip.

It isn't burning oil and only gets the very best 67 euro oil a go and gets it every 10k miles at the very most.

I use millers every 3 tanks or so aswell.

When it's warm even after a 60 mile trip it still puts out visible smoke ticking over so maybe valve stem seals as ticking over will cause a vacuum more so than revving.

It's an interesting case!
 
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Pimped up vario

Cordy Cruizer
Nov 20, 2009
1,291
0
Belfast N Ireland
I raced a 325i sport e30 and beat him the first time and was beaten the second time. My point is that one of the guys from work watching said they could hardly hear my tuned 110 bhp tdi leon, all be it with a standard exhaust, and could hear the beamer miles away.

Diesels are inheriently quieter engines due to the more effiecient combustion process. When people say a diesel sounds noisier, its not actually the case. They just emit their sound energy in a frequencey that causes irriatiation more readily.
 

john_tdi

mmm 385lbft
Feb 21, 2007
687
0
s wales
Over twenty years ago that e30 might of had a whopping 160 bhp! Any who . A Diesel engine is louder than a petrol counter part all day long, if you measure sound from the engine compartment. Which is what people refer too. Not extaust noise. Petrol engines use a spark to ignite the fuel/air mixture. Diesels ignite it by sheer brute force, squeezing the air/fuel mix until it spontaneously combusts. The forces involved are massive. Relatively speaking more of the resulting energy is lost as vibration/noise than a petrol. This is also the reason why diesel engines are heavier, tougher, more expensive than equivalent petrol ones. If they weren't they fly apart with a bang and a puff of smoke.
 
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