emissions testing 1600DP

[crosswind]

hello all.

been fighting the emissions testing blues and am losing.

to make a long story short I took my motor back to almost completely stock to get it through emissions here. it's a 1600 dual port, 34pict3, SVDA, blue coil. meticulously cleaned carb on several occasions. it is a nearly new BOCAR. the only thing not stock is the Engle 100 cam.

idle HC's are twice the limit. even took the main down to a 120, but just leaned out the loaded readings. even with the new SVDA there is a rough spot in the off-idle transition.

i've done testing after each step in the process with no real change. it's the only thing left. everything is is top notch condition.

would you think this cam could be causing my problems. have not checked my vacuum at idle yet. poor mixing due to a low vacuum by a lopy cam?

i have no problem with replacing the cam, but am I missing something else?

any advice?

[Amskeptic]

idle HC's are twice the limit. even took the main down to a 120, but just leaned out the loaded readings.

HCs are not a mixture measurement. By reducing the main, you lean out the CO yes, but you can seriously increase idle HCs by lean misfire.

If you are truly stock, I can get you through the idle HCs with no problem.

DROP your plug gaps to .024-.025" Make sure your points are .016-.018" File the vertical edge of the tip of the rotor.
(this reduces misfire HCs)
Increase the idle speed with the big brass idle air screw to 1,100 rpm.
(this dilutes idle CO)

Turn the little mixture screw just below it until you get the very best idle you can.
(this reduces misfire HCs but may increase idle CO)

Make your last movement of that mixture screw in a clockwise direction to drop the idle speed (we are on the mixture screw!) 50 rpm lean.
(this reduces idle CO and keeps HCs still low enough)

Now retard your ignition timing (turn distributor clockwise) until the idle is 950. Raise idle speed at the big brass screw just 25 to 50 rpm. This is to get through emissions test.
(now this is a trick, it heats up exhaust temps to help lower HCs AND it dilutes CO nicely) Engine will have less power and warmer exhaust, but do not fear.

Arrive with a fully warmed up engine and a clean supply of fresh crankcase oil. If you have an oil bath air cleaner, change the oil in it just before heading on down.

Let me know how it works

[vwlover77]

From personal experience, I know that "performance" cams can cause problems at idle. In my case, it was a 78 Bus with a CBPerformance "Torque Special" cam. Even with fuel injection, the idle had to run extremely rich to be smooth.

What are the specs on that Engle cam?

[crosswind]

I plan on replacing the cam and lifters with stock once I get back into town. Then I will let you all know how it goes.

Here are the spec's on the Engle 100 cam.

http://www.vwspeedshop.com/camchart.htm

Just remembered to mention that the heat risers are clean too.

[Amskeptic]

Just remembered to mention that the heat risers are clean too.

Wouldn't even matter. On test day, you want a thoroughly thoroughly thoroughly warmed up engine. But, good for you, they are instrumental in good warm-up driveability on a cool humid day.
Colin

[crosswind]

Update for my emission testing on my 1970 Beetle.

I installed a good used factory VW camshaft this past weekend (-1 cam gear) and some new lifters. Took it through emissions today and the results were unbelieveable! HC were at 172 and CO was 2.92%. Passed with no problem. Smooth acceleration from a stop and excellent driveability overall. Very happy with my results and am looking forward to putting some miles on it. Has not been registered for 2 years. Just like a new car to me.

I really did not think that such a 'mild' camshaft would affect idle emissions, but it did. I've got the numbers to prove it.

[Amskeptic]

Update for my emission testing on my 1970 Beetle.

I installed a good used factory VW camshaft this past weekend (-1 cam gear) and some new lifters. Took it through emissions today and the results were unbelieveable! HC were at 172 and CO was 2.92%. Passed with no problem. Smooth acceleration from a stop and excellent driveability overall. Very happy with my results and am looking forward to putting some miles on it. Has not been registered for 2 years. Just like a new car to me.

I really did not think that such a 'mild' camshaft would affect idle emissions, but it did. I've got the numbers to prove it.

Preach it brother.
ColinAmen

[vwlover77]

You'll certainly get an "Amen" from me!

And the lord of the VWs spaketh, "Stickest thou with thy stocketh camshaft and though shalt reap the reward of an engine bestowed with the smoothness and power of an angelic army." Or something like that....