Cam and emissions compliance
02-20-2006, 06:25 PM
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Cam and emissions compliance Hey guys. I have done a lot of searching and reading lately. I think it may be time for me to do a cam soon. Car is a 98 Z28 M6, pacesetters, TSP catted Y and LM 1. The car is raced seldom and basically is a city cruiser. I need a cam that will: 1) give me a nice SOTP, down low, crusing around town power increase 2) A nice Rumpity, Rump sound and 3) Pass the sniffer etest. My friend has HP tuners and a wideband set up so we can tune after the cam. I've read that a -7 overlap is what I need for the smog test. Do other things also affect the abiltiy to pass? Like lobe profile (XE vs XE-R) and lift. For example a TR224 VS a TSP224R, same overlap. Would both pass equally? How about LSA? Like a TR224 114 VS a TR220 112. Both -4, would both of these pass equally?
I know the 224 cams are borderline for passing. I want to able to tune myself for etesting and daily driving. I also want lots of leeway for etesting (dont want to pay a professional to tune a "borderline cam")
The cams I am condidering are: TR224 or a TSP224R. If these are "iffy" for passing smog then TR220, TSP220 or Speed Inc's Comp 222/222. All on a 114.
Im not concerned with spring life as the car only sees about 3000 KM a year or less.
Can you guys offer any sugestions? Sorry for the long post.
I know the 224 cams are borderline for passing. I want to able to tune myself for etesting and daily driving. I also want lots of leeway for etesting (dont want to pay a professional to tune a "borderline cam")
The cams I am condidering are: TR224 or a TSP224R. If these are "iffy" for passing smog then TR220, TSP220 or Speed Inc's Comp 222/222. All on a 114.
Im not concerned with spring life as the car only sees about 3000 KM a year or less.
Can you guys offer any sugestions? Sorry for the long post.
02-21-2006, 10:37 AM
#6
1) give me a nice SOTP, down low, crusing around town power increase 2) A nice Rumpity, Rump sound and 3) Pass the sniffer etest
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02-21-2006, 02:50 PM
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Good stuff Rich. 
I'm hoping that something with 0.5 degrees of overlap can be made to pass an e-test up here as well or else I'll be doing a cam swap once every 2.5 years.
To further Rich's question, will a cam with -7 degrees overlap require no tuning at all to pass an e-test and a cam with say -4 degree's just a few minor touches? Are most of you guys running a "sniffer" tune and then another tune maximized for WOT power?
So far I'm planning on running my cam and tuning it first for max power using the wideband and HPTuners. After getting it dialed in that way I figured I'd work on a sniffer tune and do a few tricks here and there with timing, idle speed, fuel additive etc. and then test it on an e-test dyno to see if it's able to pass both with the power tune, and next with the sniffer tune. I'm curious to see the differences between both.
What kinds of cams are you Cali guys getting to pass your tests if any? Or do you do the big swap every time the test comes about?
I'm hoping that something with 0.5 degrees of overlap can be made to pass an e-test up here as well or else I'll be doing a cam swap once every 2.5 years.
To further Rich's question, will a cam with -7 degrees overlap require no tuning at all to pass an e-test and a cam with say -4 degree's just a few minor touches? Are most of you guys running a "sniffer" tune and then another tune maximized for WOT power?
So far I'm planning on running my cam and tuning it first for max power using the wideband and HPTuners. After getting it dialed in that way I figured I'd work on a sniffer tune and do a few tricks here and there with timing, idle speed, fuel additive etc. and then test it on an e-test dyno to see if it's able to pass both with the power tune, and next with the sniffer tune. I'm curious to see the differences between both.
What kinds of cams are you Cali guys getting to pass your tests if any? Or do you do the big swap every time the test comes about?
02-21-2006, 04:25 PM
#9
I know that a number of people have made the 224/224 114 pass the sniffer without a special tune or additives. Bumping the idle to 950 rpm for the test helps. Others have made bigger cams pass playing with timing etc and using 1000+ rpm idle speeds.
02-21-2006, 07:26 PM
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Originally Posted by Ragtop 99
The TR 220 on a 112 LSA best meets that criteria. Same overlap as the 224 cam on a 114 so tuning will be very similar but the response in the 2000 - 3000 rpm range will be stronger than the 224 cam.
Originally Posted by Ragtop 99
I know that a number of people have made the 224/224 114 pass the sniffer without a special tune or additives. Bumping the idle to 950 rpm for the test helps. Others have made bigger cams pass playing with timing etc and using 1000+ rpm idle speeds.
02-21-2006, 07:54 PM
#11
Originally Posted by Ragtop 99
I know that a number of people have made the 224/224 114 pass the sniffer without a special tune or additives. Bumping the idle to 950 rpm for the test helps. Others have made bigger cams pass playing with timing etc and using 1000+ rpm idle speeds.
Why does bumping the idle to 950 help to pass a smog test?
02-21-2006, 09:15 PM
#12
Originally Posted by spazzyfry123
Forgive me if I stray off of topic here...Can you define "bigger cams"? Or better yet, can you give an example of what a bigger cam is to you?
I am really wanting a great sounding car at idle, but to acheive this I would need a car with more duration, correct?
The only thing that is keeping me away from a larger cam is the loss of low-end power. But can this low-end power be "recovered" by going with higher ratio rear-end gears and possibly advancing the timing? My ears are very keen to the T-Rex cam, but I would be afraid of its drivability on a M6 car (daily driver).
Why does bumping the idle to 950 help to pass a smog test?
02-21-2006, 10:32 PM
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Originally Posted by Ragtop 99
By bigger cams I was referring to cams around 230* duration rather than 224*.
False. Idle speed is the key to getting the lopey sound. The 220/220 112 at 750 rpm will sound just as aggressive as a 230/230 112 with an 875 rpm idle
Gears do improve the SOTP response and also get you into powerband sooner. Timing isn't a solution per se because the smaller cam should be optimally tuned just as you would tune the larger cam. You need to decide what you really want from a cam and where your combination of mods is going.
Generally, the "bigger" the cam, the less efficent it is at very low rpms. Because of the extra overlap of a bigger cam, it is going to run rich and generally have less complete combustion. Good, patient tuning can deal with this, but a higher idle speed helps move the cam to a little more efficent point and makes it easier to tune.
False. Idle speed is the key to getting the lopey sound. The 220/220 112 at 750 rpm will sound just as aggressive as a 230/230 112 with an 875 rpm idle
Gears do improve the SOTP response and also get you into powerband sooner. Timing isn't a solution per se because the smaller cam should be optimally tuned just as you would tune the larger cam. You need to decide what you really want from a cam and where your combination of mods is going.
Generally, the "bigger" the cam, the less efficent it is at very low rpms. Because of the extra overlap of a bigger cam, it is going to run rich and generally have less complete combustion. Good, patient tuning can deal with this, but a higher idle speed helps move the cam to a little more efficent point and makes it easier to tune.
02-24-2006, 12:56 PM
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So the lower LSA moves the power down in the RPM range? I always thought the opposite was true. Thanks for the info. One more question though. What are the benifits if any of a split cam? Is it benificial for guys that run cats to have a little bit more duration on the exhaust side? Thanks again.
02-24-2006, 03:07 PM
#15
I hate to generalize on LSA, but wider LSAs tend to make a flatter power curve while tighter LSAs tend to make the cam peakier and you notice the on cam / off cam feeling more. The combination of a smaller duration and tighter LSA makes it easier to move the power down.
Extra exhaust duration does help exhaust flow when you have restrictions such as cats or poorly designed manifolds (e.g. stock).
Extra exhaust duration does help exhaust flow when you have restrictions such as cats or poorly designed manifolds (e.g. stock).
02-26-2006, 11:37 AM
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SOTP = Seat Of The Pants. 
Hmm.. the cam I'm looking at has about 0.5 degree's of overlap. I'm wondering if I'll get into any issues with passing the sniffer. I can tune my vehicle with HPTuners and I have a wideband. I've been tuning for about a year now and did a complete overhaul of my VE tables, PE, and recalibrated my MAF sensor. What a difference that made. I guess I'll get to try my hand at cam tuning come mid-summer! Rich, you up for guinnea pig if my bumpstick doesn't go in my car until mid-summer and yours is in come spring?
Thanks for the well educated responses guys!
Hmm.. the cam I'm looking at has about 0.5 degree's of overlap. I'm wondering if I'll get into any issues with passing the sniffer. I can tune my vehicle with HPTuners and I have a wideband. I've been tuning for about a year now and did a complete overhaul of my VE tables, PE, and recalibrated my MAF sensor. What a difference that made.
I guess I'll get to try my hand at cam tuning come mid-summer! Rich, you up for guinnea pig if my bumpstick doesn't go in my car until mid-summer and yours is in come spring? Thanks for the well educated responses guys!
02-26-2006, 02:01 PM
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I'll be a guinnea pig! My plan right now is to test it with just the headers and catted Y. Then I have 2 years to play. We'll hook up with Gary and run it off the grid till we get it right. Then right click and save as!
02-26-2006, 03:14 PM
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That's the shizat! If we can tune yours to pass then we can tune mine. The TSP 224R on a 116 looks appealing.. what's the overlap on that one? Gotta be decent.
If we can tune yours to pass then we can tune mine. The TSP 224R on a 116 looks appealing.. what's the overlap on that one? Gotta be decent.