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Emissions and NA performance mods

culberro said:
You should be fine if the catalytic converter is up to snuff. Raising the idle speed also helps.

Kyle (klr142) has a decent cam in his dd and it passes the PDX sniffer test... though I think he run larger valve clearances to get it through smog (reducing the cams duration).
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This last time I didn't get it to pass, actually, so now it's registered as a Special Interest vehicle. :rofl: Sometimes I'd also have to put in E85. That being said, I have a small race cat and a full header with no wrap or coating. The cat cools down too fast and I don't pass at idle. If I raise the rpm for a bit I can watch the cat start working better with a gas analyzer, but as soon as it gets back to idle it isn't good enough anymore. This is with an H cam and a header designed for 175whp+. I did get it to pass years past with the H or a smaller cam in it, but the primary header pipes were smaller with less volume to cool off. I need to get it coated to help keep the heat in there. I also should just get a larger, factory style cat, as it isn't that big of an issue. I also have had big valves with port work. Right now it doesn't have the big valve head with much/any port work, but it still doesn't want to pass with the H cam in. B cam went through emissions testing with flying colors, even with the rest of the setup mostly as it is.

spock345 said:
Well I am due to replace the cat anyway. It barely squeaked by on NOX last time. I have narrowed it down to the 30 year old cat.

I am mostly worried about what shaving the head will do as that feels like a point of no return. The goal is the low 10.3-ish to 1.

At this point I am debating between a V, VX, or K cam. With the overlap I am guessing a K will probably hurt emissions the most.
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If you take .030" off, add a thinner headgasket and slap the K cam in there, it will be a good setup. You might want to adjust the combustion chamber a bit for less possibility of detonation and to help make the compression ratio not be too high for your 91 octane fuel. The stock ignition timing may be too much with just .030" off the head, a .030" or .036" headgasket and the K cam. I wouldn't run anything less than a V cam at the very least, and even likely less than the K cam because the dynamic compression will be high.

I'd get a K cam, slap a thinner headgasket on it, get a nice 3 angle valve job done and shave .030" off(or more, depending if you can tune your ignition timing), maybe open up the combustion chamber around the spark plug's bump, and run it. Set the valve clearances to stock or on the looser side around .018", advance the K cam 3-4 degrees to account for the shorter head and gasket, and it'll be a torque "monster" from 2000rpm on up and should go through emissions testing without issue if the downpipe and cat are stock-ish items, I expect.

PCH said:
I had the K about 3 degrees advanced. M47 with 3.73 rear. Single muffler turbo style under axle exhaust.
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A good recipe for fun, and even more fun if you shave some off of the cylinder head and/or use a thinner headgasket.

dl242gt said:
I run a V15 n/a cam. Use a chipped ezk only and a simons sport exhaust. I pass emissions every time without issue. As my cat got older it started to get higher nox readings but still passed the last time it was checked. Then I got an exemption and no longer have to inspect or test the car as it's older than 1995.

Changes I would make for a bit more performance.
A lighter flywheel.
The 3.73 rear which you already have.
Shave the head a bit and some flow work.
While the head is off measure the piston height so you can make the engine tight squish.
Maybe go to slightly larger injectos like the 16v ones if I did the head work.

That's all I'd do and then leave it alone and enjoy. If you use the rear axle ratio of the manual cars you'r testing rpms will be lower so you'll have lower emissions. But the 3.73 is a better axle ratio for fun driving.
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Agreed with all of this, too. The V15 NA cam will have better idle and emissions than the K cam, with maybe slightly less peak HP, but it'll still be good all around and much better than a V or VX.
 
BTW I run the V15 at six degrees advanced. With the 3.31 rear I don't mind giving up a bit of top end as Kyle mentioned and the cam advance helps get the car going. If you look at the specs the V15 has the ~lift of the K cam but with the same duration as the B cam. So it's not going to rev out as high as the K.

I bought my cams direct from enem many years ago.
 
I have 0.040" off of my 530 head with a V cam and 3.31s. '91 245 with an M47. Cam is straight up. I can speak from a driveability standpoint that there's no reason to advance the cam, it will gently pull itself out from low rpm/high gear circumstances, no problem. With 3.73s, it would be even less. I also run 87 octane with this combo with no problem. My commute is about 20 miles one way and a near 50/50 split between city and highway and I average just over 23 mpg winter. Took a long road trip up through Maine a couple weeks ago and got about 29. I'm very happy with this cam, I feel it's an improvement over the A I had been using for years.
 
klr142 said:
The stock ignition timing may be too much with just .030" off the head, a .030" or .036" headgasket and the K cam.
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Note that in CA they check timing. You can deviate a couple of degrees away from whatever their books tell them is "stock", I don't recall how far, but it isn't much.
 
Toybox said:
Note that in CA they check timing. You can deviate a couple of degrees away from whatever their books tell them is "stock", I don't recall how far, but it isn't much.
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The car is LH 2.4. Last time they didn't check timing once they noticed it was computer controlled. It is also easy to revert back to a stock map by swapping a chip.
 
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Redwood Chair said:
:uh:

They check it at idle in accordance with the prescribed recomendations for a given engine according to their data base that is shown / prompted on their computer screen.
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Doesn't LH 2.4 idle timing not change even when you have advanced it by changing the map or through the pin grounding technique?
 
Well, there actually is the ability to adjust the idle timing maps(separate from the main timing maps) with the EZK XDFs now, but you don't really need to tinker with that in most circumstances(and definitely not in the one we're speaking of).

shoestring said:
I have 0.040" off of my 530 head with a V cam and 3.31s. '91 245 with an M47. Cam is straight up. I can speak from a driveability standpoint that there's no reason to advance the cam, it will gently pull itself out from low rpm/high gear circumstances, no problem. With 3.73s, it would be even less. I also run 87 octane with this combo with no problem. My commute is about 20 miles one way and a near 50/50 split between city and highway and I average just over 23 mpg winter. Took a long road trip up through Maine a couple weeks ago and got about 29. I'm very happy with this cam, I feel it's an improvement over the A I had been using for years.
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Just to confirm, this is with a stock thickness headgasket, right?
 
Honestly, too much, probably close to 0.050". I would also prefer to run the 0.036", but I think when I did this I was in a time crunch and had a stock gasket around...
 
Where does the argument of static vs dynamic compression ratio come in when talking about combustion temps and therefore NOX emissions?

If I have done my math right the dynamic compression ratio of a stock M cam B230F is 8.736:1 versus the dynamic compression of a motor with 0.030" off, 0.036" HG (10.3:1 static), and a K cam at 8.584:1. The VX3 isn't far off in that configuration with an 8.59:1 dynamic CR.

Do my math and assumptions look right?

I am still trying to figure out the difference between static and dynamic compression and how it influences the engine's behavior. It would be nice to know if I am going crazy from staying inside or not.
 
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Generally speaking, if you can run regular/low octane gas on your M cam setup, you can probably run regular/low octane gas on your K cam setup as well because your dynamic compression is lower. If your dynamic compression were higher than stock, you might have trouble with detonation while running that low octane fuel. The higher your dynamic compression, the more torque(and power) the engine is going to make - as long as it doesn't blow up from detonating.

Raising the static compression when you put in a larger/higher duration camshaft helps get you back closer to that original dynamic compression. This helps restore some of or all of the torque and low rpm performance(and efficiency) that you would lose if you didn't increase the static compression.

I haven't looked at the numbers, but I would expect the VX3 to have higher dynamic compression than the K by a decent margin. I would also not bother running the VX3 if you like performance. :)
 
klr142 said:
Generally speaking, if you can run regular/low octane gas on your M cam setup, you can probably run regular/low octane gas on your K cam setup as well because your dynamic compression is lower. If your dynamic compression were higher than stock, you might have trouble with detonation while running that low octane fuel. The higher your dynamic compression, the more torque(and power) the engine is going to make - as long as it doesn't blow up from detonating.

Raising the static compression when you put in a larger/higher duration camshaft helps get you back closer to that original dynamic compression. This helps restore some of or all of the torque and low rpm performance(and efficiency) that you would lose if you didn't increase the static compression.

I haven't looked at the numbers, but I would expect the VX3 to have higher dynamic compression than the K by a decent margin. I would also not bother running the VX3 if you like performance. :)
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From what I can tell the intake valve closing is the key event. The VX3 is at 57.7 degrees ABDC and the K is 57.8 ABDC. So they have similar dynamic ratios. The A and B have a later valve closing in the 61-62 ABDC range. The earlier the intake valve closing, the better the DCR. My plan is to try finding someone with an exhaust gas analyzer so I can tell which cam gets better emissions at higher compression.

http://dok.b230fk.de/volvo_camshafts.pdf

This is what I used for the intake closing event numbers.
 
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