Cams and emissions
Thread Starter
Burning Brakes
Joined: Mar 2003
Posts: 915
Likes: 1
From: UK
Cams and emissions
What is an aftermarket cam more likely to increase in terms of tailpipe emissions... HC or CO?
I understand that a lopey idle will significantly affect HC at idle due to all the unburnt fuel caused by a large overlap. However, with the engine running off-idle (say 2,000rpm), will the HC and CO levels be closer to stock, or will they still be 'off the scale'?
I've read that the LSA is a big factor in whether, or not, a cam will pass emissions and that a 114LSA is safe and a 112LSA is probably a 50/50 bet. I know tuning is important, but there's only so much you can do. What about lift and duration... do these numbers affect tailpipe emissions too?
It seems there is a real lack of data about how cam specs relate to exhaust emissions and it seems like it would be very difficult for anyone living in a sniffer state (or country) to pick a cam due to fears that it would fail the test. I know some tuners have cams that are 50-state legal for emissions, but many tuners have no real clue (or interest) in whether, or not, their cams pass emissions regs. This is probably due to the fact that the majority of their customer base live in states where emissions aren't really a factor.
Does anyone have any idea if this information is available somewhere online? Does anyone on here have any real-world data to share?
Any help is much appreciated.
Cheers,
Ian.
I understand that a lopey idle will significantly affect HC at idle due to all the unburnt fuel caused by a large overlap. However, with the engine running off-idle (say 2,000rpm), will the HC and CO levels be closer to stock, or will they still be 'off the scale'?
I've read that the LSA is a big factor in whether, or not, a cam will pass emissions and that a 114LSA is safe and a 112LSA is probably a 50/50 bet. I know tuning is important, but there's only so much you can do. What about lift and duration... do these numbers affect tailpipe emissions too?
It seems there is a real lack of data about how cam specs relate to exhaust emissions and it seems like it would be very difficult for anyone living in a sniffer state (or country) to pick a cam due to fears that it would fail the test. I know some tuners have cams that are 50-state legal for emissions, but many tuners have no real clue (or interest) in whether, or not, their cams pass emissions regs. This is probably due to the fact that the majority of their customer base live in states where emissions aren't really a factor.
Does anyone have any idea if this information is available somewhere online? Does anyone on here have any real-world data to share?
Any help is much appreciated.
Cheers,
Ian.
Last edited by i_york; May 23, 2005 at 02:13 PM.
Le Mans Master
Joined: Aug 2000
Posts: 8,762
Likes: 2
From: Murphy TX
I was speaking with the LG guys Saturday and they care, and are working on a setup to be able to test their various setups.
I would guess primarily HC like you mentioned. The way I see it is if lift and duration affect it too much then the tuning is off a bit because it means you aren't burning all the charge. Overlap is of course an obvious player.
Best bet is to call a tuner. Like I said I know one that is aware/cares about this stuff (I'm sure others do also, I just happened to discuss this point with LGM the other day).
I would guess primarily HC like you mentioned. The way I see it is if lift and duration affect it too much then the tuning is off a bit because it means you aren't burning all the charge. Overlap is of course an obvious player.
Best bet is to call a tuner. Like I said I know one that is aware/cares about this stuff (I'm sure others do also, I just happened to discuss this point with LGM the other day).
