Another Emissions/Cam Question

Bushdude · Feb 12, 2006

I asked this question on another forum I frequent and got no answers...maybe its a dumb question...'I dunno'...but I am really curious so I'll ask here as well.

At what point do you reach the point of diminishing returns.

I have a 331 with the TFS top end kit (stage 2 porting by Foxlake) with the stage 1 cam.

I have to meet Maryland emissions so I kept the stage 1 cam and I am hoping for the best. There are a few tricks that I can do to get it thru if it is marginal. I have no desire to swap cams every two years for a 15 minute appointment.

I know that by using this cam I am leaving a lot of power on the table but it is a DD and strictly street car. Even so I still would like to squeeze it to the limit or close to it but still be able to pass the test.

What I was wondering is how far can you push the cam before you are screwed emissions wise. The stage 1 is .499/.510 @ 112. What specs are you all running and still passing emissions.

I have been reading and researching and have yet to reach a definitive conclusion. It always seems that there is some oddball factor thrown into the mix on cam manufactures websites or in magazine articles. So I come to the real world to find an answer. Any thoughts.

joel5.0 · Feb 12, 2006

The problem with an aftermarket cam is basically the overlap (OVL). Since this is the period of time when both I/E valves are open, an increase in HC and CO is to be expected...how much of an increase?...that's the 64K cents question.

In your case the stg 1 OVL is 53° vs. 39° OEM, I know your concern about the oddball factoring thing, but this cam doesn't have the "50-states emissions-legal" disclaimer...reason why the stress on the performance, emissions wise, of the other components in the engine; they need to "make up" for the cam specs....what do they check for in Maryland?...CO, HC, CO2 passing levels = ?, do they check for NOx emissions?.....

In order to keep CO and HC's at bay, you need to make sure the rest of the systems are in top shape...PCV system, no missing cylinders, clean air filters, timing right (a little on the high end helps), Air mgmt system (smog pump), no system codes, O2's sharp and ready, FP pressure at the minimum possible (if you have an adjustable FP reg).

NOx, EGR tip-top conditions, no codes........get the picture?.....Hope this helps.

mackey · Feb 12, 2006

Running the FP at the minimum doesn't help. As the AF/R goes lean the NOx emissions spike GREATLY. Keeping it at the stock level is the best for emissions. There is a graph of it in the Electronic Engines control ford book if you would like to see. The emissions are least at stoich, which is 14.7:1.

Bushdude · Feb 13, 2006

Joel5.0--so what you're saying is that since the overlap comparison is so great that all the other components must be in working order...Okay I got that, plus a few of the other little tricks imparted by jrichker on "How to pass emissions" plus the last choice of denatured alcohol. I know the e-cam is supposedly the alternative to the stage 1. Are there other cams that offer similar or better performance yet allow you to stay under the radar. Ummm maybe I should start a speadsheet of cam ovl's to see where the legal issue drops off...sounds like I am grabbing for straws again. I will post the emissions ranges later.

mackey--sounds like the best thing might be to run the stage 1 and try to get thru emissions with it and wait until I get the superchager installed and get a custom cam and chip to stay legal and be done with it. I always considered custom cams as being for all out racing...I'll just have to make sure I am done with the build-up before I have one spec'ed. would not want to pay for a custom more than once. Problem is that I never seem to be finished.

Thanks for the info.

Another Emissions/Cam Question

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Another Emissions/Cam Question

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