any danger associated with decat on N/a?

[drunknmunky]

Hi people,
As per title, are there any dangers/problems to the engine with decatting a N/a car? Lean or rich running, detonation etc? ECU light?

Thanks in advance
Andy

[Draven]

You'll fail your MOT

[drunknmunky]

thanks pal, should have said I am aware of this one though, I mean to the actual car itself?

[synXero]

You'll slowly gas yourself to death and your car will smell pretty bad.

There are no real engine risks as far as I'm aware but please don't fall into the trap of thinking you're unleashing chained up performance either!

[Draven]

Yeah there are no real risks but no real gains on an N/A

[SonicSW20]

The only O2 sensor is before the cat, so it won't make any difference to fuelling or anything like that.

As others have said, you'll fail an MOT though.

[craig]

No danger or benifits. As above, mot fail

[Lcfcdan]

Mine came with a Decat already fitted, but it was made before the Cat converter law in August '92, will it pass with a Decat on as it was manufactured in the same year but months before?

[ashley]

Hi people,
As per title, are there any dangers/problems to the engine with decatting a N/a car? Lean or rich running, detonation etc? ECU light?

Thanks in advance
Andy

No danger to the engine what so ever, and it can only help the exhaust flow better- and in theory increased exhaust gas velocity should help free up a few ponies with the right corresponding modifications.

Never seen any back to back dyno plots to prove decatting a 3S engine does or doesn't make any extra power, not sure why folk claim it doesn't help

Also saves a nice chunk of weight, which always a good thing

[drunknmunky]

thanks for the responses people, much appreciated:)

[synXero]

Never seen any back to back dyno plots to prove decatting a 3S engine does or doesn't make any extra power, not sure why folk claim it doesn't help

I'll revise my input then... There's certainly no tangible improvement in performance. Allegedly most people will 'notice' 10% increases in power when modifying. That would correlate to 17hp and you're definitely not getting a tangible improvement with a decat, so IMO whatever you gain is so minimal it's not worth it for the legal and environmental implications.

[craig]

Plus don't na engines rely on back pressure? Thereby removing the cat making things worse.

Plus the above is irrelevant really given that you'd have to keep refitting the original cat for the mot

[JohnnyC]

The only benefit will be the noise.

[ashley]

Plus don't na engines rely on back pressure? Thereby removing the cat making things worse.

Plus the above is irrelevant really given that you'd have to keep refitting the original cat for the mot

It's not about back pressure, it's about exhaust gas velocity, tuning exhaust valve pulses and scavenging...none of which will be helped by having a cat in the system.

I'll revise my input then... There's certainly no tangible improvement in performance. Allegedly most people will 'notice' 10% increases in power when modifying. That would correlate to 17hp and you're definitely not getting a tangible improvement with a decat, so IMO whatever you gain is so minimal it's not worth it for the legal and environmental implications.

I agree- you probably won't see a 10% increase in power simply from removing a cat- but in combination with other mods it may help yield increases (with these engines every little bit helps!); the main saving is from weight, and in the most important place as well- right at the back of the car.

[SonicSW20]

Plus don't na engines rely on back pressure? Thereby removing the cat making things worse.

Plus the above is irrelevant really given that you'd have to keep refitting the original cat for the mot

The back pressure thing is a myth.

I think it's often confused with scavenging which is something different entirely! Removing the cat won't affect that if the system remains the same length as I understand it.

[ashley]

Wouldn't the gas having to pass through a fine mesh slow it down, and so have a direct effect on scavenging?

[Nic]

Plus don't na engines rely on back pressure? Thereby removing the cat making things worse.

Exhaust back pressure on NA engines is a myth. This explains it better than I can http://www.gomog.com/allmorgan/exhaustbackpressure.html

Removing the cat should help the engine rev freer but gains in hp will only be small. The main effect of removing the cat will to make the car a lot louder.

[firebobby]

I have a NA import and will be fitting a mongoose rear box, I want to keep the cat for noise reduction, Not being a speed demon and being fairly new to MR2 ownership, I find my car plenty quick enough for me.

[2mad]

Dont know the science .. but I dcated a 1.6 na .. and it defiantly had a sprig in its step afterwards .. I think with na's good exhaust velocity is key .. fitting a 3" piped exhaust for-instance would not be good for performance .


Just my 2p

[ashley]

Dont know the science .. but I dcated a 1.6 na .. and it defiantly had a sprig in its step afterwards .. I think with na's good exhaust velocity is key .. fitting a 3" piped exhaust for-instance would not be good for performance .


Just my 2p

Spot on