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Emissions and NA performance mods

Here is my math. Keep in mind these are all approximations as I took the stock combustion chamber volume of 51.7 CC and treated it as a simple arrangement of cylinders and a prism to approximate the effect of shaving the head. 6 CC cylinder dish and a 0.004" deck height. I also assumed a 0.036" Cometic head gasket as that seems to be the consensus on a generally safe thinner gasket. The chart also assumes you have an adjustable timing gear to adjust cam timing back to normal after raising the SCR. The 0.004" dataset is assuming you just went and got the head resurfaced without taking much off.

xiElOaX.png


From this you can see that there are a few groupings of cams that don't really line up with the common categories of skinny lobe, fat lobe, and hybrid.

I can see a few distinct groups.

1. T and M, relatively high dynamic compression, close to 9:1 in stock form.
2. V and VX, really the same intake valve close timing, next highest in dynamic compression around 8.3:1 stock.
3. D, H, K, VX3, all of these have around an 8.1-8.2:1 dynamic compression ratio stock.
4. A and B, lowest dynamic compression ratio at below 8:1, explains the ****ty idle I have with an A cam.

The T and M cams probably should not be run with a higher SCR as I noticed an increase in NOX production when even just going from the M to the T on a stock motor (I can dig up the smog results). So if you want to run a factory cam like the V or VX the most you can shave off without increasing DCR above the stock M cam configuration would be about 0.040" with a relatively conservative HG. This is at least my running theory. It will require real world testing to be sure. Hence why I plan to find myself a cam in the V/VX/VX3 family to complement my T, M, A, and K.
 
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Couple notes for your math. This info I have measured myself.

Piston dish on a B230F is 8.0cc. Dish on a B230FT is 12cc. I've measured enough to say that I have 99.9% confidence in these numbers.

While the engines are advertised at 9.8:1 and 8.7:1 respectively, I have found that the SCR is 9.1:1 and 8.3:1. You MIGHT be able to reach the 9.8:1 if you mill the head the maximum factory recommended 0.020", and if the piston deck height is at the highest possible tolerance. I have found pistons that protrude not more than 0.004", but have only measured a few. Your results may vary.

Keeping in mind that the combustion chambers are not EXACTLY the same cylinder-to-cylinder, I have measured an untouched 530 head at 54.5cc. A 0.040" mill netted a combustion chamber size of 49cc. It seems like a lot, but keep in mind that the first cut is cutting out the largest part of the chamber. Further cutting yields less return. With about 0.100" mill, the chambers are about 44cc.

Early race engine used a 0.040" mill, 0.030" Cometic (piston was 0.004" in the hole), and got us about 10.2:1. With a D cam and no tune, this combo got us 120whp on the button.
 
shoestring said:
Couple notes for your math. This info I have measured myself.

Piston dish on a B230F is 8.0cc. Dish on a B230FT is 12cc. I've measured enough to say that I have 99.9% confidence in these numbers.

While the engines are advertised at 9.8:1 and 8.7:1 respectively, I have found that the SCR is 9.1:1 and 8.3:1. You MIGHT be able to reach the 9.8:1 if you mill the head the maximum factory recommended 0.020", and if the piston deck height is at the highest possible tolerance. I have found pistons that protrude not more than 0.004", but have only measured a few. Your results may vary.

Keeping in mind that the combustion chambers are not EXACTLY the same cylinder-to-cylinder, I have measured an untouched 530 head at 54.5cc. A 0.040" mill netted a combustion chamber size of 49cc. It seems like a lot, but keep in mind that the first cut is cutting out the largest part of the chamber. Further cutting yields less return. With about 0.100" mill, the chambers are about 44cc.

Early race engine used a 0.040" mill, 0.030" Cometic (piston was 0.004" in the hole), and got us about 10.2:1. With a D cam and no tune, this combo got us 120whp on the button.
Click to expand...

That changes the measurements a bit. Do you mean you don't often find engines with the pistons above the deck more than 0.004"?

So with a stock setup, your 0.004 in the hole measurement, and an M cam I get 8.06:1 dynamic, VX3 is 7.55:1, A is 7.35:1, D is 7.56:1, and K is 7.54:1. With 0.040" off the head and a 0.030" gasket we get the M cam at 8.456:1, VX3 at 8.44:1, A at 8.23:1, D at 8.46:1 (10.137:1 static), and K at 8.44:1.

In the config I have been thinking of with 0.030" off the head, 0.036" HG, and a K cam I get about 8.16:1 dynamic and 9.79:1 static. Although I need to revise how I am approximating the combustion chamber volume to account for that taper. I should be able to figure out a function to approximate new combustion chamber volume after shaving some off the head.

What interests me is how the dynamic ratios change as we increase the static CR for each cam. Demystifying some of the behavior of these camshafts and give some guideline numbers. I am right now working on a dynamic compression spreadsheet calculator to complement your cam profile spreadsheet. So more numbers are helpful.

My big hypothesis is still that we can approximate how much we can take off, which bigger factory cam to use, and still keep combustion temps under control to squeak through on NOx with a nice street motor. CO and HC I am not so sure about.
 
This stuff makes my head spin... Too many variables trying to satisfy too many different requirements and desires (emissions, performance, cheaper gas).

There are lots of online dynamic compression calculators, including some with extreme detail. You can take a look and double-check your results to one of these.
http://www.wallaceracing.com/dynamic-cr.php
https://uempistons.com/rt-4-calculators.html
http://www.pcengines.com.au/calculators/Calculate%20dynamic%20comp%20ratio.htm

Isn't the idle NOx strongly dependent on overlap or exhaust valve closing angle (causing EGR), or can a fresh CAT clean this up enough?
 
bobxyz said:
This stuff makes my head spin... Too many variables trying to satisfy too many different requirements and desires (emissions, performance, cheaper gas).

There are lots of online dynamic compression calculators, including some with extreme detail. You can take a look and double-check your results to one of these.
http://www.wallaceracing.com/dynamic-cr.php
https://uempistons.com/rt-4-calculators.html
http://www.pcengines.com.au/calculators/Calculate%20dynamic%20comp%20ratio.htm

Isn't the idle NOx strongly dependent on overlap or exhaust valve closing angle (causing EGR), or can a fresh CAT clean this up enough?
Click to expand...

I am unsure. I was under the impression that idle NOx was tied to the AFR and combustion temperature. The leaner the mixture and higher the temp the more NOx you get. With HC being tied to the valve overlap as you can get unburnt fuel out the tailpipe.

Although I already used those calculators to double check mine.
 
But wait, there's more! Based on Shoestrings measurements for combustion chamber and piston dish volume. I will be measuring the combustion chamber on my stock cylinder head to see if I can't get better numbers for the shaved head volume. They are rough at best with only three data points to extrapolate from. Ignore the disregard for proper significant figures. This is version 0.1 of the calculator.

uvkpvxn.png
 
my buddy Dan does that kinda of stuff when he builds a motor

<iframe width="560" height="315" src="https://www.youtube.com/embed/s7iYNJjbuQA" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
 
spock345 said:
That changes the measurements a bit. Do you mean you don't often find engines with the pistons above the deck more than 0.004"?
Click to expand...

I've never found one higher. That said, I've only measured a strong handful.

If you want to amuse yourself, try running the DCR calculator with the cam "advanced", that is, the intake valve closing, 2, 4, or 6 degrees earlier. You'll see how aggressively that changes your DCR. In my opinion, when you have to move your cam timing around to get the engine to "run better", what it really highlights is the point that your cam and compression ratio are not correctly matched. Now, changing cam timing is WAY easier than changing compression ratio, and I'm not being critical of guys who take that approach, I'm just highlighting that this is what's afoot.

I always try to approach mods math-first, like what you're doing here. When you reverse-engineer what the factory did, and think about the desired result (like an engine that runs well on low octane fuel), you can get an idea what may be tolerable. Good example is those longer-duration cams, how much compression you need to add just to maintain the DCR of the M cam.

Something you may want to look at is DCR on a throttled engine. I've briefly read some things on this a while ago, and throttling an engine affects compression ratio differently, and this seems relevant to your NOx concerns.

As a sidebar, many many years ago I looked at DCR on Chevy V8s (my background. Small Chevys forever!) from the 60's and it looked like 8.0:1 was the factory target, most of the performance engines came in very close to that number. Oddly enough, I think these Volvo engines have a similar number. I deduced that for a 2-valve, kinda lousy chamber design cylinder head, 8.0:1 was the approximate number for mass-production.

I am enjoying this thread.
 
Going over my build notes re: head milling, here's what I have. The 54.5cc head milled 0.040" yielding 49cc chambers is what we'll call cylinder head A. It used stock valves, which will matter later.

I have a DIFFERENT head that shows cut 0.070" to yield 48cc chambers, and then cut another .008" to get 47cc. Later that Summer (2013) we have an exhaust valve change that changes the chamber to 46cc. The following year we milled again 0.103", with another exhaust valve change, and chambers 1-2-3-4 measured 45-44-44-45cc respectively.

Point here I guess is that there is definitely some deviation between heads and even chambers, so it is probably wise to err on the side of caution.
 
shoestring said:
I've never found one higher. That said, I've only measured a strong handful.

If you want to amuse yourself, try running the DCR calculator with the cam "advanced", that is, the intake valve closing, 2, 4, or 6 degrees earlier. You'll see how aggressively that changes your DCR. In my opinion, when you have to move your cam timing around to get the engine to "run better", what it really highlights is the point that your cam and compression ratio are not correctly matched. Now, changing cam timing is WAY easier than changing compression ratio, and I'm not being critical of guys who take that approach, I'm just highlighting that this is what's afoot.

I always try to approach mods math-first, like what you're doing here. When you reverse-engineer what the factory did, and think about the desired result (like an engine that runs well on low octane fuel), you can get an idea what may be tolerable. Good example is those longer-duration cams, how much compression you need to add just to maintain the DCR of the M cam.

Something you may want to look at is DCR on a throttled engine. I've briefly read some things on this a while ago, and throttling an engine affects compression ratio differently, and this seems relevant to your NOx concerns.

As a sidebar, many many years ago I looked at DCR on Chevy V8s (my background. Small Chevys forever!) from the 60's and it looked like 8.0:1 was the factory target, most of the performance engines came in very close to that number. Oddly enough, I think these Volvo engines have a similar number. I deduced that for a 2-valve, kinda lousy chamber design cylinder head, 8.0:1 was the approximate number for mass-production.

I am enjoying this thread.
Click to expand...

I have been playing around with it a bit. I currently have my A cam advanced three degrees and with the very late intake close angle for the A and B it kind of needs it to recover a bit of the DCR.

I also added the NA version of the V15. If my math is right it is similar to the K and H.

I think at this point I will have to take the head off the existing motor to figure out what my deck clearance is. I know this motor runs fine through emissions on a T or M cam when everything else is stock. So that gives me a DCR range of 8.06:1 to 8.28:1, so just call it 8.0:1-8.3:1. Once I know the actual deck clearance I can estimate how much to take off and what head gasket to buy to keep that DCR range with cams like the K, VX, and V15 (IVC within a few degrees of each other). With the adjustable cam gear providing the ability to fine tune it.

I think I will be taking about 30 thou off with a 0.036 cometic or whatever the equivalent of that is with a thicker or thinner HG. It would be nice to be able to rev to 7K. The rev limiter is really the biggest thing I want to change on the ECU.

Given the sound and head configuration I always thought of these motors as half a 283 V8. For decades my family was almost all Volvos and Chevys, especially early 60's Novas. I think the last Nova standing is my uncle's restomod. Almost everything looks stock but with an LS1, painted orange of course.
 
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I've seen deck heights over .004". I'm pretty certain the General Leif's pistons were higher than that and according to RSI's measurement(not that I trust it) with my B230F, the pistons(or at least one or some, who really knows) were .010" over. My block hasn't been cut, and I don't think the General's was either.

spock345 said:
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.
Click to expand...
I hadn't noticed that PDF until now and I can't imagine that the number are correct. The D cam is more aggressive than the A and B, this suggests otherwise. Etc...

I feel like we can't look at the math as much as we want to. Dynamic compression ratio and intake valve closing times can't be the only things that affect idle emissions. The numbers don't seem to match the real world with regard to idle quality and very likely tailpipe emissions, but they aren't considering overlap or total duration. I didn't take notes when I ran them, but I'm certain the K cam idled worse than the A cam(even with much higher static compression), and a V(VX or VX3) cam idle better than both. Etc.

Also, where did you find V15 numbers? :)
 
Kyle's here ^^^ is a LH2.4 and NA performance guru. I was impressed watching his NA 240 beat up turbo cars and win that small autocross at Davis back in 2011(?)
 
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klr142 said:
I've seen deck heights over .004". I'm pretty certain the General Leif's pistons were higher than that and according to RSI's measurement(not that I trust it) with my B230F, the pistons(or at least one or some, who really knows) were .010" over. My block hasn't been cut, and I don't think the General's was either.


I hadn't noticed that PDF until now and I can't imagine that the number are correct. The D cam is more aggressive than the A and B, this suggests otherwise. Etc...

I feel like we can't look at the math as much as we want to. Dynamic compression ratio and intake valve closing times can't be the only things that affect idle emissions. The numbers don't seem to match the real world with regard to idle quality and very likely tailpipe emissions, but they aren't considering overlap or total duration. I didn't take notes when I ran them, but I'm certain the K cam idled worse than the A cam(even with much higher static compression), and a V(VX or VX3) cam idle better than both. Etc.

Also, where did you find V15 numbers? :)
Click to expand...

The most common formula I have found is IVC = (intake duration/2 + LSA) - (ground-in-advance + 180). I just took the advertised numbers for the V15 and used those. The source of the numbers has me skeptical as well. Mostly due to variation between sources. I am inclined to listen to the numbers on the forum cam spec sheet and Shoestring's figures. I have updated the calculator with those. The numbers look more realistic. I think the D and V can be explained because they both have higher lift than the A and B but shorter duration. I have yet to update the sheet to include valve lash in the calculations. The only one I am still skeptical about is the M cam.

It also has me really tempted by the V15 over the K for my car. The dynamic compression is that of a B cam and it has less overlap than a K so it may stand a better chance for fuel economy and HC. I am still going to run the K for a bit to see how I like it, whenever the postal services get it here. It seems that for a DD or milder NA car I haven't heard anything bad about the V15. If I sell a few parts I may be able justify getting one to compare to the A and K head to head.

rdDMf3R.png


My hunch is that we can limit the increase in NOx through keeping the dynamic ratio and thus combustion temperatures under control. At least enough that one wouldn't have to be sticking fresh cats in it relatively frequently (which is the impression I am getting). HC will go up with any higher overlap camshaft. I am not so sure about CO, although a hotter burn should help. This is why I want to get my hands on an exhaust gas analyzer.
 
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Whatever cam spec dataset I draw from, it would seem that they tell me the same thing about the same set of cams. V, VX, K, and V15 with the equivalent of 0.25-0.3 off the head and the right thickness headgasket for proper squish results in a similar DCR to a T and M cam in a stock motor. I would like to be able to run a VX in a pinch if it can't sail through emissions with a K.

To be honest I am probably worrying too much and should just deck the head and see what happens but I am now invested in the engineering challenge.

In the interest of making a usable calculator, what measurements in Shoestring's spreadsheet should I use for the cam timing? I have noticed that duration and valve events are often measured at 0.05" lift. Is it fair to extrapolate what that point is by plotting the curves for the dataset or should I determine valve close some other way?
 
More later, but I just had a quick thought that’s relevant. I have always had trouble getting passed Portland’s emissions testing since having the .040” off, big valve 530 head done(and even now running a near stock head with .033” or so off with a .036” gasket), but I flew through with no problems when I tossed in the B cam instead of the H or K13 I was running. I have a large 4-2-1 header and small race cat, though. I should also ask Marc how he does with his more stock car that has a head and headgasket of similar height with a K cam how his car has been with emissions testing.

What are the emissions numbers you need to meet?

I need to look back up, but you mentioned you wanted a higher redline. I can likely do that for you if you want.
 
Here we have a two speed dyno test, 15 and 25. All rather strict. Up until 2011 it was 1600 NOx.

For 15mph we have to get 91 HC, 0.62 CO, and 730 NOx.
For 25mph we have to get 116 HC, 0.74 CO, and 791 NOx.

The cat on mine is still original, I may get one or two more tests out of it.

I have heard a lot about how the K hurts emissions but I have never heard anything about whether it passes or not.

I definitely want to rev a bit higher. So far I have a set of the larger B21 valve springs that are said to be good for 6800rpm instead of the small diameter early B230 springs that are currently in it.
Given the 4 thou per 1k rpm and 4 for safety rule I would need a clearance of about 0.032".

I thought the advertised SCR for a B230F was 9.8:1?
Click to expand...

Nominally yes, but according to Shoestring's real world measurements it differs a bit. I am going to be measuring my motor while building it up so we have more data points.
 
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klr142 said:
I feel like we can't look at the math as much as we want to. Dynamic compression ratio and intake valve closing times can't be the only things that affect idle emissions. The numbers don't seem to match the real world with regard to idle quality and very likely tailpipe emissions, but they aren't considering overlap or total duration. I didn't take notes when I ran them, but I'm certain the K cam idled worse than the A cam(even with much higher static compression), and a V(VX or VX3) cam idle better than both. Etc.
Click to expand...

I mostly agree with this. I think the math has value, but there's cylinder filling, throttling, exhaust pulse, etc., to consider.

There's a reason incremental improvements in powertrain technology and performance cost huge amounts of money.
 
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