ok so after i cleaned all conectors and swapped my ptu I found that I had alot more power but am now getting my cat over heat light coming on. so i've now decided to de-cat the beast and got intouch with the local garage that says they will do it but dont know how many cats the z has nor do they know anywhere I can get replacement pipes from. so firstly is there 1 or 2 cats (Iv looked and I think i can see 2) on the zed, and secondly do any of the leicester boys know of a local place where i can get replacement pipes from??? :D

theres 2 main cats + 1 or 2 precats

as Paul says but if it's a 92+ it'll have just the one pre-cat on the passanger side.

 

Vijay

No its on a 'h'. so what do i need then to de-cat her?

Daft question - Does a Series 2 PTU give more power?

I swapped mine to a series 2 cos my original was fubar. but it def help in the old power department!

give Luke a call - http://www.zcentre.co.uk/exhausts/zc070a.htm

 

Vijay

august 93 was when the law was introduced to have a cat, if your car was registered before this then cats off they come

Daft question - Does a Series 2 PTU give more power?

 

no, its just more reliable

Cat overheat light means you are losing a spark somewhere - there's more power to be found yet LMAO

 

Pre '92 cars have no precat at all, '92> have one precat on the passenger side. All you need is the standard decat pipes. Sort the spark problem first though - the light is coming on because raw fuel is getting into the exhaust and overheating the cats ;)

Cat overheat light means you are losing a spark somewhere - there's more power to be found yet LMAO

 

Pre '92 cars have no precat at all, '92> have one precat on the passenger side. All you need is the standard decat pipes. Sort the spark problem first though - the light is coming on because raw fuel is getting into the exhaust and overheating the cats ;)

 

or the sensors faulty ;) :D

 

i think it was only LHD cars that had 2 precats wasnt it?

I don't know of any of the models that had 2 pre cats. Remember though that the pre cat will be on the drivers side if LHD and passenger side if RHD ;) :D

Doesn't de-catting the 300 make it less reliable? I have read elsewhere on this forum that de-catting it will reduce back pressure (obviously) which will reduce crank case pressure (not sure how!) which will cause the bottom set of piston rings to start leaking because they require a certain ammount of pressure to stay seated. The oil vapour in the exhaust fumes will then damage the turbos. Can anyone confirm this?

I thought the only reason why we didnt have a pre cat was because of the way the column was routed on a RHD??

look here ;)

 

http://www.ttzd.com/tech/precatstech.html

Doesn't de-catting the 300 make it less reliable? I have read elsewhere on this forum that de-catting it will reduce back pressure (obviously) which will reduce crank case pressure (not sure how!) which will cause the bottom set of piston rings to start leaking because they require a certain ammount of pressure to stay seated. The oil vapour in the exhaust fumes will then damage the turbos. Can anyone confirm this?

 

 

4 stroke engine cars don't need back pressure. If anything with backpressure your slowing down the turbos. 2 strokes need it.

Doesn't de-catting the 300 make it less reliable? I have read elsewhere on this forum that de-catting it will reduce back pressure (obviously) which will reduce crank case pressure (not sure how!) which will cause the bottom set of piston rings to start leaking because they require a certain ammount of pressure to stay seated. The oil vapour in the exhaust fumes will then damage the turbos. Can anyone confirm this?

 

I can confirm that this is a load of *****x!! :D

I believe the J-spec cars have restrictors in place of the pre-cats, even on the early models. Worth removing these since they serve absolutely no purpose whatsever other than to restrict power output to meet the 280 bhp limit in Japan.

 

Reliability wise I think the biggest threat is to your turbo seals due to the reduced back-pressure afterf removing the cats. I'm not an expert so do a search on it.

Two strokes dont actually need back presure, what a well tuned 2 stroke gets is a pulse of pressure which goes from barrel to the end of the expansion chamber (if your lucky) and then reverses back towards the engine and then reverses again when it gets to the barrel, this second change of direction creates a low pressure area behind it as it goes for the next load of exhaust gas to exit into. I was told this by a clever man who raced them.

Thats right, and if done correctly can work on a 4 stroke as well as the exhaust fumes are litteraly sucked out of the head (if it is done very wrong the exhaust fumes can litteraly be blown back into the head, it's quite a science and only works at a specific rev range and this is why car manufacturers don't tune their exhausts). What I mentioned was completely different, if the crankcase pressure was dropped and the bottom rings relyed on that pressure to keep them seated then they could start leaking. How the crankcase pressure is connected to the exhaust back pressure I'm not sure unless the exhaust fumes are used to pressurise the crankcase (possibly through the crankcase breather) and if the back pressure in the exhaust drops, then that pressure would also drop. I don't have a 300 yet so I was trying to do a bit of homework before I get one and blow it to bits!

Thats right, and if done correctly can work on a 4 stroke as well as the exhaust fumes are litteraly sucked out of the head (if it is done very wrong the exhaust fumes can litteraly be blown back into the head, it's quite a science and only works at a specific rev range and this is why car manufacturers don't tune their exhausts). What I mentioned was completely different, if the crankcase pressure was dropped and the bottom rings relyed on that pressure to keep them seated then they could start leaking. How the crankcase pressure is connected to the exhaust back pressure I'm not sure unless the exhaust fumes are used to pressurise the crankcase (possibly through the crankcase breather) and if the back pressure in the exhaust drops, then that pressure would also drop. I don't have a 300 yet so I was trying to do a bit of homework before I get one and blow it to bits!

 

 

:D:D:D:D I suppose this person also told you that you need forged pistons for anything more than a filter/exhaust? :D Crank case pressure is exactly what you DON'T want!!! All that will do is blow the oil seals out and you'll end up with a nice sticky mess....

Two strokes dont actually need back presure, what a well tuned 2 stroke gets is a pulse of pressure which goes from barrel to the end of the expansion chamber (if your lucky) and then reverses back towards the engine and then reverses again when it gets to the barrel, this second change of direction creates a low pressure area behind it as it goes for the next load of exhaust gas to exit into. I was told this by a clever man who raced them.

 

Am I right in thinking the Scooby engines are two of the above glued together out of phase a bit - hence bom-BOM-bom-BOM rather than the usual boring 4-stroke whirrrrrrr?

Am I right in thinking the Scooby engines are two of the above glued together out of phase a bit - hence bom-BOM-bom-BOM rather than the usual boring 4-stroke whirrrrrrr?

 

no bud, its cos they are a flat 4 or otherwise known as a Boxer engine. Where the two banks are at 180 deg from each other.

 

As you can see here

Doesn't de-catting the 300 make it less reliable? I have read elsewhere on this forum that de-catting it will reduce back pressure (obviously) which will reduce crank case pressure (not sure how!) which will cause the bottom set of piston rings to start leaking because they require a certain ammount of pressure to stay seated. The oil vapour in the exhaust fumes will then damage the turbos. Can anyone confirm this?

 

The only detrimental effect decatting will have is that without back pressure, aging or slightly worn turbos begin to make themselves known..... :rolleyes:

 

The reduction in back pressure causes oil to get past the turbo rear seals giving a James Bond type smoke-screen behind you as you boot it ;)

 

Don't know if it actually causes the rear turbo seals to fail prematurely though.

 

Richard :)

I wish someone who KNOWs would settle this "no cats and it kills your turbo seals" once and for all. I for one find it hard to believe. Anyone?

for all the engine cares take all the exhaust off after the cats, it will only help with the efficient working of it. How can you get backpressure back throught the turbos when the exhaust is flying through them at a high pressure.

 

NO BACK PRESSURE IS NEEDED IN NAs OR TURBOS