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Whos makes best decat??
- Thread starter Ja5on
- Start date
Yozzasport mate...its the only one with a bend in it....the ktec one is made by blueflame as is the gdi one IIRC.
http://www.yozzasport.co.uk/store/proddetail.php?prod=clio_rs_182_cup_trophy_decat_link_pipe
http://www.yozzasport.co.uk/store/proddetail.php?prod=clio_rs_182_cup_trophy_decat_link_pipe
ForceIndia
ClioSport Club Member
Gentlemans spec 200
Will insurance cover a de-cat, just wonderin because prob not gonna get thru MOT with one
Also look at Supersprint for extremely high quality. The got a 7 bhp gain on a 172 with a metal cat and back box.
Much higher quality than most of the stuff on the market.
Decat - if you have an accident with your CAT removed and the car is taken away - you will not be covered for your car nor the damage you may cause to other cars/objects. Be VERY careful.
M
Much higher quality than most of the stuff on the market.
Decat - if you have an accident with your CAT removed and the car is taken away - you will not be covered for your car nor the damage you may cause to other cars/objects. Be VERY careful.
M
Ali said:
Maybe you should look into exhaust design and you might understand. Exhaust internals, bore size all comes into it.
Why does a 6 branch manifold release upto 18 bhp on some cars - it's justa bunch of pipes some could say!
Removing a CAT on most BMW's for exmaple yeilds some very good gains.
M
MY10 R35 GTR
^^^^^
its had me wondering mate!
you ran 6/7 bhp less than last time. On the same rollers. With all the same items in the car.
Its made me wonder if my reading is accurate. tempted to buy me bits and do a day at the RR changing bit as I go. Then I can get an idea of the difference a change makes because its on the same day.
Alis changed stuff so we aint got a proper comparison for what his was
its had me wondering mate!
you ran 6/7 bhp less than last time. On the same rollers. With all the same items in the car.
Its made me wonder if my reading is accurate. tempted to buy me bits and do a day at the RR changing bit as I go. Then I can get an idea of the difference a change makes because its on the same day.
Alis changed stuff so we aint got a proper comparison for what his was
Clio 197
warren4 said:
Bizzarely, I told my insurance about my decat.
My car won't need an MOT for another 18 months mind.
They asked if it would give me any power gain - I said under 5%. Job done.
which dyno cell do you regularly use fred?
not sure where my nearest one is.
Standard 182 cat is pretty free flowing as standard. De-Cat wise.....
Another reason to fit the BTB unit is a bit more technical, most people want to take the CAT off as they sap so much power, the problem is taking the CAT out and substituting a straight pipe is not really correct. OK, this will certainly give you the power back the CAT takes away through restriction but this causes another problem. When exhaust gas comes out of the cylinder it produces sound/pressure waves that travel up and down the exhaust system, if these S/P waves can be controlled correctly they can be harnessed to draw extra gas from the cylinder and so make the engine more efficient. These S/P waves are controlled by the cam timing and the pulses go down the exhaust until they meet the first expansion chamber, silencer, CAT (anything that causes the size of the exhaust bore to rise significantly). As soon as the gas reaches this expanded section, the S/P wave stops and goes back to the cylinder head, as this wave hits the back of the valve it bounces back and causes a suction pulse that helps pull more gas out the next time the valve opens. The problem is the distance from the first expanded section to the cylinder head is critical, to get this pulse action working correctly, if this distance is not correct the wave goes back at the wrong time and hits the gas coming out of the valve and so stops the gas coming out rather than helping it. This is what happens when you take the CAT out, you no longer have an expanded section in the correct place and the S/P wave will go down the system until it reaches the first silencer box before returning. Before CAT's were fitted, this was the reason all cars had an expansion boxes in a similar position to where they now fit CAT's. I know some one will say, what about the VTR with the CAT on the down pipe, or the old mini with only one silencer at the rear. The complications of how these S/P waves travel is not quite as simple as above. Lets assume the correct distance from the valve head to the first silencer should be 80 inches, providing you double or treble the distance or half it, quarter it, the S/P waves will still work their effect, so having the CAT on the down pipe or just one silencer at the back can still be right, what is practically certain is that taking the CAT out and substituting a straight pipe will not be correct and so you will loose some power.
taken from a very good tuner, talking about BTB system for a citroen saxo, which same principles apply!
not sure where my nearest one is.
Standard 182 cat is pretty free flowing as standard. De-Cat wise.....
Another reason to fit the BTB unit is a bit more technical, most people want to take the CAT off as they sap so much power, the problem is taking the CAT out and substituting a straight pipe is not really correct. OK, this will certainly give you the power back the CAT takes away through restriction but this causes another problem. When exhaust gas comes out of the cylinder it produces sound/pressure waves that travel up and down the exhaust system, if these S/P waves can be controlled correctly they can be harnessed to draw extra gas from the cylinder and so make the engine more efficient. These S/P waves are controlled by the cam timing and the pulses go down the exhaust until they meet the first expansion chamber, silencer, CAT (anything that causes the size of the exhaust bore to rise significantly). As soon as the gas reaches this expanded section, the S/P wave stops and goes back to the cylinder head, as this wave hits the back of the valve it bounces back and causes a suction pulse that helps pull more gas out the next time the valve opens. The problem is the distance from the first expanded section to the cylinder head is critical, to get this pulse action working correctly, if this distance is not correct the wave goes back at the wrong time and hits the gas coming out of the valve and so stops the gas coming out rather than helping it. This is what happens when you take the CAT out, you no longer have an expanded section in the correct place and the S/P wave will go down the system until it reaches the first silencer box before returning. Before CAT's were fitted, this was the reason all cars had an expansion boxes in a similar position to where they now fit CAT's. I know some one will say, what about the VTR with the CAT on the down pipe, or the old mini with only one silencer at the rear. The complications of how these S/P waves travel is not quite as simple as above. Lets assume the correct distance from the valve head to the first silencer should be 80 inches, providing you double or treble the distance or half it, quarter it, the S/P waves will still work their effect, so having the CAT on the down pipe or just one silencer at the back can still be right, what is practically certain is that taking the CAT out and substituting a straight pipe will not be correct and so you will loose some power.
taken from a very good tuner, talking about BTB system for a citroen saxo, which same principles apply!
maahny said:
bit of a difference between one straight pipe that has a universal size of 2.5" and a 4 or 6 branch manifold with varying pipe paths to select from...
a decat is just a straight pipe, granted, some are better than others, but only in the welds and quality of material. BB tuning twisting decats I'd stay away from if your a MK1 owner, went through two of those, they split and fell to bits both times... utter crap. Powerflow one I have now is fine, £60 fitted in 15 minutes. No problems since.
This is a very simplistic look at exhaust pulse tuning, and there are far too many generalisations.
Firstly the size of the crossectional change has a greather bearing on the amplitude of the refracted negative sign that will travel back towards the head, so ultimately opening to atmosphere has the greatest result, a perforated silencer will do very little, especially the high efficiency ones.
Then you have to take into account exhuast temps as this will effect density of the gasses, and the speed of sound which the pulse will travel at. This is changed when the car has moving air under the vehicle.
And these pulse tuning effects will invariably lead to a corresponding trough to the peak in the power graph you have just created, so you need to know where you want to place the peak. IMO, for road cars its best to try and cancel out the effects and work with manifolding.
Its a complex area and not something an exhaust place, even like btb, can pump out correct numbers straight off.
Firstly the size of the crossectional change has a greather bearing on the amplitude of the refracted negative sign that will travel back towards the head, so ultimately opening to atmosphere has the greatest result, a perforated silencer will do very little, especially the high efficiency ones.
Then you have to take into account exhuast temps as this will effect density of the gasses, and the speed of sound which the pulse will travel at. This is changed when the car has moving air under the vehicle.
And these pulse tuning effects will invariably lead to a corresponding trough to the peak in the power graph you have just created, so you need to know where you want to place the peak. IMO, for road cars its best to try and cancel out the effects and work with manifolding.
Its a complex area and not something an exhaust place, even like btb, can pump out correct numbers straight off.
fmp_ said:
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