Alright so about a year ago I installed Kelford 272's on my car. My buddy had done the same a few weeks before and I was in love with the sound/lobe on the car. However, same person did mine and my car doesn't lobe much, sounds more like a rough idle than anything which I am certain it is not.

Base timing is at 5* BTDC, everything is dialed on good, car was dyno tuned and all, nothing wrong with it. Just wondering why such difference from one car to another if we have identical cams? I've also heard a few more with same cams and they actually sound cammed.

I am at work, but I can upload a video later today.
Any ideas?

By the way, both cars done by the same person and both tuned by me.

So you guys have a idea, I put these two youtube videos up for comparison.

This video is pretty much how much my car "cams" not much and it's more of a stumble. Mine stumbles a bit more as my idle is lower than this guys:

http://www.youtube.com/watch?v=Bvs_w3NdWNw

This is how all the other 272 Kelford cams I hear sound, including the one that had the identical cam setup as me.
http://www.youtube.com/watch?v=lBh8dbhOXkQ

I heard if you degree them perfectly you can make even a 280 sound almost factory, im not 100% about that though.

All your answers are here:
http://www.dsmtuners.com/forums/cyl...est-delta-hks-272-delta-k272-bc-272-cams.html

^^great link above, and I second that cam timing plays all the roll you could imagine and more in the "lope" of idle, my 264/272 can sound stock or i can make them lumpy depending on how i time them, ut i prefer the way they perform when sounding stock, guess i can't have MY cake and eat it too, but i love top end power and less overlap with move vacum

Thanks for the info and I did find some interesting stuff in that thread, but I am unsure of something. What exactly is Cam Timing, like the actual advancing/retarding of timing via adjustable cam gears?

maybe this will help!


Technical Specs & Information

DSMBanditFZ6 said:

maybe this will help!


Technical Specs & Information

Click to expand...

Came across that article but not sure on how the LSA works. I mean I know what a tighter LSA does or what not according to the table, but how is this relevant to adjusting Cam Timing. Does the LSA change when cam timing is changed?

Still not sure what you guys mean by adjusting Cam Timing, I'm assuming through the cam gears, like advancing/retarding timing?

***NOTE

added two videos in the first post, to compare the two different "camming" sounds I'm talking about.

Sounds about right, if you find something post it up!

DSMBanditFZ6 said:

Sounds about right, if you find something post it up!

Click to expand...

What the videos or the post itself about the LSA changing when the Cam Timing is changed?

You know i want to know why my car sounds so smooth, and other cars sound like they have a big cam. I have the FP2s, and i was going to switch them out for the kelfords, but after you saying the samething happeneing to you i think i may stay with my FPs

What rpm is your idle? The lower the rpm, the more it will lope.

The second video is my car at 10° base timing set up in ECUFlash/Ceddymods

My idle is at 900, bit lower and it still doesn't lope.

Just throwing this out there, have you pulled your valve cover to verify 100%the kelfords are in your car?

No need to, I assisted with the install, it's a friend of mine, not a shop. I was there. Good observation though.

The car in the first video is idling higher than the car in the second video. Timing will also change the lope.

If your cams are degreed in right you will notice less difference until you get a bigger cam.

Boostinsideways said:

If your cams are degreed in right you will notice less difference until you get a bigger cam.

Click to expand...

I didn't degree my cams, could this be it?

I was reading this article here, so you can't degree cams without adjustable cam gears? That's what it says in the parts list. So with stock cam gears you can't do it?

http://www.4g63turbo.com/tech/4g63-camshaft-degreeing.html

^ That is correct, you need adjustable cam gears to degree cams.

Thanks guys, guess there's not much I can do for now.

Also, I just noticed this morning, I was approaching a stop light and when I put in in neutral, as the car came to idle speed the wide and read a bit lean for a few seconds which I've never seen it do before. Anyhow when it was like at 16.x I actually hear the car canning a lot, like in the 2nd video I posted more or less. Any thoughts on that? Tune? I haven't dialed it in since my dyno session months ago. So my tune could be a bit off as far as trims and such, but sound shouldn't have changed I would say.

Technically, Mike and Modern Automotive Dynamics can degree cams with stock cam gears... but yea.

Sounds like an exhaust leak. What idle speed were you running? It sounded like it was above 1000.

Any how to's that you know off? Or is that like their own little secret?

I'll try to contact them, see if they have any pointers.

1 : With Wrex, I noticed that she idled a lot 'lumpier' with stock cams opposed to the 264/272's. It sounded rather stockish when I installed them. They were HKS, for reference, on stock cam gears.

2 : An exhaust leak, before or at the front 02 sensor/simulated 02, will cause these conditions. The wideband is going to feed the incorrect information. It's somewhat like a boost leak but causes more profound effects, and a lot sooner. You could be idling just perfect and be reading lean. I had to fight this with Wrex for a while.

3 : Fuel trims tend to change with different cams. When I made the switch from stock - 264/272's I noticed a little bit richer of a condition that I had to accommodate for via MAF adjustment and deadtime adjustments.

You'll get her figured out. The lower you get the RPM's and the fuel trims dialed in, you'll notice the cams a bit more. However, to each vehicle their own.

The loping sound from a bigger cam is caused by the unstable vacuum drawing air into the engine, the unstable vacuum is caused by too much exhaust to intake valve overlap for the current engine rpm. You can't correctly call it Lobe Separation Angle because a higher duration cam with a wider LSA can create the exact same vacuum instability as a smaller duration cam with a narrower LSA.

When the exhaust valve is still closing and the intake valve has started to open it's called valve overlap. Overlap changes with physical camshaft timing (cam gears) as well as lobe duration (cam size).

When both intake and exhaust valves are open and the piston is approaching TDC on it's exhaust stroke, you may get some reversion of exhaust back into the intake port. As the piston passes TDC and starts down the intake stroke it creates vacuum to draw in air and fuel, and if the exhaust valve is still closing... well then, some of that exhaust previously pushed out can be drawn back in, some of that very precisely measured air mass and precisely corrected tiny fuel injector pulsewidth (*with your big injectors) can even sometimes travel out the exhaust valve unburned.

Both of these undesirable conditions usually occur with big duration cams and they work together to cause misfiring and random weak firing due to poor air/fuel charges. Hunting intake manifold vacuum levels are caused by the weak firings interspaced with good firings, because the ECU is working overtime adjusting things to correct the fuel trims and spark timing to try to maintain target idle speed.

As you increase engine speed, the loping effect will generally subside. This is due to the mass of air. It takes time for it to move, gaining momentum and achieving a velocity that drives the air/fuel mass through the valves in the correct direction, albeit sometimes partially overshooting and passing a little unburned through to the exhaust.

Some expert tuners will work around the lumpy idle and set constant or very narrow range idle speed timing correction and fueling, some will simply ignore it because they don't care to fix it and still others will try to make their car produce the sound just because they think it's cool.

I wouldn't be too upset or worried, but you might want to consider adjustable cam gears and scheduling dyno time to degree them in so they work the way you want them to.