These scanned pages come from the Daimler Chrysler Academy "Convertible and Supercharger Engine Update" book.
This book is now out of print.
See also the PDF at the bottom of this post.

 

Good stuff, thanks for posting!

 

Thanks Dave, your always updating our knowledge.

 

What I have noticed for sure is that when I first got the SRT6, the SC engagement was tame and smooth. Since I have fully modified it with just about every mod., it now has a buck at 2900 rpm(wife hates it!) unless you start off aggressively(getting to that specified load quicker and engaging the SC before it reaches the 2900 rpm.). To not feel the buck/jerk, we need to get off the line quickly. This isn't such a good thing for smooth daily driving.

 

Could it be that with less belt slip the SC gets up to speed faster from the free wheeling condition and result in a faster power surge? The magnet faces would probably slip a bit more as well. As the engine revs faster the SC has to catch up to something that is moving faster and faster. Maybe the fuel requirements lag behind for a moment and then suddenly catch up resulting in the surge.
Smaller SC pulleys and or larger crank pulleys with PSKs would be the worse condition for this obviously.
The dog bone springs in the SC pulley would be under greater stress and lead to earlier failure.

 

All interesting points Dave; I'm not certain. I didn't have any belt slip before or after the mod.'s. I've been scratching my head over this for awhile now. The surge is definitely the SC clutch "hooking", and happens at precisely the same rpm. Here is my theory: With the added torque and horsepower from the modifications, the engine works easier, and it's harder to reach the 44% "load" threshold that our AMG power plant was originally programed with to engage the SC. Thus, it will reach the "2900rpm" threshold before it reaches the "load" threshold.
Does anyone else with highly modified SRT6 experience this? I've got big air and big fuel.

 

You have to have belt slip otherwise the SC would have to go from free wheeling speed to the speed determined by belt speed. Obviously that is not possible so belt slip occurs. This happens with or without a PSK, less slip would bring the SC up tp belt speed sooner.

 

Dave, I believe you are confusing belt slip with SC clutch slip. If we all had "belt slip", there would be a fine rubber powder/dust down by the SC pulley from the wearing of belt. I don't have that. Look at the back of the SC clutch plate. That is the wear from the "hooking up" / slip of clutch.

 

Yes, I do. I find that I either have to get into it, or back off a bit. I was thinking if the point of engagement could be raised a bit, most of my driving would be done without the SC engaging at all but when I need it, it's still there.

 

I've had similar thoughts about it too. But I would opt for it to engage sooner(less load)so that when it did engage, it would hopefully not have as much pronounced surge/jerk. This is a side affect of way better air flow than stock IMHO.

 

I have previously mention the magnet slipping more, but belt or magnet slippage occurs and amounts to the same thing. A PSK will make the clutch slip more as something has to absorb the sudden load due to the rotors and gears coming up to speed. Mine remains unmodified and I have no noticeable powder from magnet or belt. More slipping at the magnet and less belt slipping means the dog bones are taking the load more.

 

Yes, agreed. To my point, this is why I believe (if it could be done) it would be better for the modified guys to have it kick in a little sooner; so it wouldn't be taking as high of a load(less rpm's for it to catch up to). Your comment on the dog bones is why many of us have installed LM21's pulley shield. For me, this small inconvenience is worth the performance now experienced. But it would be nice if there was an easy fix. I wonder, can EC tune it out?

 

I experience the same thing u are describing and I just have a 65mm pulley. I made a thread about this topic last year about this time. https://www.crossfireforum.org/forum/crossfire-srt6/75044-chirp-sc-clutch.html

 

Same thing here. I really notice it now with catless downpipes.

 

Yep , same here , well sort of ,there is no delay or jerk . its in tall gears with light throttle the sc kinda moans as it spools up
I was hoping a 70mm fixed pulley stacked with my crank pulley might 'fix' it but sadly thats a no no on our v6.
Oh well , i think maybe we are being a bit picky ,
but possibly motors with more mods it could be more of an issue.

 

That is good thought. I hadn't considered that. I have every imaginable engine mod and maybe one or two more but isn't it fun when that baby hooks up!!!! With the wail from the exhaust and whine from the SC, it sure attracts lots of attention.

 

I don't have this delay. You might look at your spacing. If your space is too wide it might allow some magnet slip. I no longer use a spacer. My clutch will turn with no load on it. I can put a little pressure on the clutch and stop it from turning, but I feel my engagement is more immediate without the spacer. The 62 mm doesn't have a spacer, but the 65 did. Just a thought, but I have never had any lag on either car. I run belt raps on both cars as well. Trying to fight belt slippage.

 

To be a bit more clear; we don't really have a delay per se. It's just that(apparently)for me and a few others in fully modified SRT6's, when we drive conservatively, 2900 rpm's is reached before the 44% load that was programmed OEM(see 180's info. on top). Our bigger air and fuel has created a noticeable jerk/surge when the SC hooks. I'll check my spacing as you mention, but slip doesn't seem to be the issue here. Conversely, I think that if it was slipping a little, we wouldn't feel the jerk so much. If we "get on it" and reach the 44% load before reaching 2900 rpm's, then it doesn't happen(because the SC engages at a lower rpm). Doc, not that you ever do; but if you drove it like Grandma from a stop, don't you ever feel the 2,900 rpm SC engagement? Some of us are experiencing this jerk engagement, and I'm wondering if it can be tuned out for us highly modified guys. Can anyone here link this thread to Eurocharged and see what they may think about this issue. I can live with it, but my other half hates it!

 

I don't know about "tuning it out", but some genius like Woody could maybe design a circuit that would 'gently' engage the clutch, then fully engage after a few milliseconds. This would of course imply intentional slippage and wear. Just a thought, I have no dog in this hunt.

 

I tried to convince my wife to simply be a bit more aggressive off the line, but I got the head shake and eye roll.