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Discussion Starter #1
On LXForums there's a thread http://www.lxforums.com/board/showthread.php?t=24094
discussing a new cam for the 6.1L engine. I don't want to fork the discussion unnecessarily but I want to have a thread here on the topic. The new cam has higher lift and more overlap between the times when input and exhaust valves are open. According to some Chrysler website the old cam was "superseded" in Chrysler's parts database on 11/02/05.

I'm wondering for one thing which cam (old or new) I have in my engine. The car was built on 11/17/05. Wouldn't they use different engine computer settings for the different cams?
 

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I regret posting the specs for the new cam on LXforums now, as it has become painfully obvious that very few over there and here understand what those numbers mean. There isn't enough of a change in that cam to require any computer tweaking. Would it benefit from some find point custom tuning, probably. The issue most don't seem to understand is that the 114LSA provides more overlap and depending on the ramp rate and valve close event, the cam could actually be simulating the 'old' cam in overlap. The additional lift will only benefit the 6.1L head flow and the slightly longer duration will give the 15 to 20 HP that was reported on DTW.

This cam would probably see much nicer gains with GSM's ported head package, though, so it will be necessary for those looking at numbers to figure in when the SRT8 reported on was built.

Todd
 

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Discussion Starter #3 (Edited)
WhiteDiamond said:
I regret posting the specs for the new cam on LXforums now, as it has become painfully obvious that very few over there and here understand what those numbers mean. There isn't enough of a change in that cam to require any computer tweaking. Would it benefit from some find point custom tuning, probably. The issue most don't seem to understand is that the 114LSA provides more overlap and depending on the ramp rate and valve close event, the cam could actually be simulating the 'old' cam in overlap. The additional lift will only benefit the 6.1L head flow and the slightly longer duration will give the 15 to 20 HP that was reported on DTW.

This cam would probably see much nicer gains with GSM's ported head package, though, so it will be necessary for those looking at numbers to figure in when the SRT8 reported on was built.

Todd
I may not understand either, and my thinking is the same as one or two other people over on LXForums, so please explain it to us.

You say the LSA provides more overlap time, and there's also more lift so that probably also includes higher lift during the overlap period. The two effects are additive rather than offsetting.

I can readily understand the added horsepower being available especially at WOT. Eliminating starvation at high RPMs can do that.

I wonder how it affects low-RPM operation: due to the greater overlap, there would seem to be the possibility of the intake fuel-air mixture (especially the air part of it which has less directional inertia) going straight into the exhaust unburnt, and the possibility of already-burnt exhaust gas going into the intake manifold before finding its way out the exhaust. (These effects would seem to effectively richen the mixture even more than it already is set, because the relative amount of cold air in the cylinder during combustion would decrease. There would be other effects as well, I'm sure.) Can you explain why these effects would not be important?

Why would none of this matter a great deal for whatever tunable parameters are in the engine computers?
 

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artichoke said:
Why would none of this matter a great deal for whatever tunable parameters are in the engine computers?
It is simply because there isn't enough of a change in the cam specs to warrant a complete retune. If they changed a bunch of components all at the same time, then they would have to look at tuning. Also, valve timing events are VERY important. Just knowing the lift and durations is very helpful, but doesn't explain fully the effects of the cam. Depending on cam profile ramp rates, a 114LSA cam could actually have less overlap than a 117LSA cam(not likely in this case, but possible). Also, it is important to understand that many of the manufacturers are moving to slightly closer LSAs for EGR purposes. Many vehicles don't have EGR specific equipment on board anymore, as the cam is doing it for the motor.

15-20hp is what a Mopar performance shop guesstimated for this cam over the old one. What we need is a new SRT8 rear wheel dyno and a pre-November 2005 SRT8 dyno(SAE corrected on both) to compare where they are at. If it is 15-20hp, that is probably only 9 to 14 hp at the rear wheels. Possibly not even noticable by back to back driving. If the cam shows more, then we need to take a closer looks at the event timing.

Todd
 

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Discussion Starter #5
Thanks for your information, Todd. But I still don't know enough.

I'm worried that low end torque is actually decreased and/or gas mileage is actually worsened by this change. Let's not talk only about high RPM horsepower which is the obvious good side of this change.

Regardless of how common this type of cam is (someone on LXForums said GM cams aren't like this at all -- what are the other examples then?) I think I will have to wait for this stuff to settle out before knowing the likely effect of tuning on my engine.

I hope some more detail will come out as people investigate this further.
 

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Guys, this is a direct quote from a real live DCX guy, one VERY close to the SRT team. My bolding......

There was no engineering change to the 6.1L cam profiles when the part was nic'd from AB to AC.

The engine software was not changed and contrary to what you THINK, the car would HAVE to recertify emissions and fuel economy if there was any change to the profiles BY LAW. Otherwise, DCX would be in a bowl of hot soup.
Please spread this word. We already have folks running out to buy this thing, when theres not any gain to be had.
 

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By the way: I was tardy to these threads, but I can vouch for GLHS's direct line to some people who are truely "in the know."

DCX isn't likely to be recertifying both smog results and mpg ratings by switching cams mid-year. Switching suppliers? Now that's more plausible.
 

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Discussion Starter #8
glhs837 said:
Guys, this is a direct quote from a real live DCX guy, one VERY close to the SRT team. My bolding......

DCXguy said:
There was no engineering change to the 6.1L cam profiles when the part was nic'd from AB to AC.

The engine software was not changed and contrary to what you THINK, the car would HAVE to recertify emissions and fuel economy if there was any change to the profiles BY LAW. Otherwise, DCX would be in a bowl of hot soup.
Please spread this word. We already have folks running out to buy this thing, when theres not any gain to be had.
So the software didn't change (which we sorta already knew) and the physical cam didn't change either? Is that what he meant? That would be good to know, because it means the work of the tuners and chip guys is still valid for all our engines.

Then, why did the part number change? Did they go with a different alloy or machining process or something? Which of the two profiles given on LXForums is correct, the "old" or the "new" one?
 

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From what I was told, and no quotes here, neither. I'll look back shortly and get the exact comment. As far as why, they are not saying, I can ask, but I dont really expect an answer. Tech details like that can get folks fired.
 

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glhs837 said:
From what I was told, and no quotes here, neither. I'll look back shortly and get the exact comment. As far as why, they are not saying, I can ask, but I dont really expect an answer. Tech details like that can get folks fired.
Please find out for sure. The cam specs that are posted are specs I took directly off of DTW. A member over there says he sent the AB and the AC part number cams out for read on a Cam Doctor. He posted those numbers on the forum a few weeks back. All the cams that the truck guys have ordered and received are the AC cam part number.

STU is the member over there that posted the info. He has a lot of information on the Hemi motors and had several 6.1L motors and a LOT of 6.1L parts. I'm not real sure how he had all the parts he had, as you cannot get MOPAR to send you and 6.1L short or long blocks and most of the other stuff he had. The cam gets released from hold periodically, so that is how many of the truck guys are getting the cam(I am waiting for the next release, in fact).

Todd
 

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I have an AB CAM here at my office and I have a new AC CAM coming.. I will compair them when they get here to see if they are different.. I already have a shop lined up to install it in my Magnum as soon as I get it
 

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artichoke said:
Then, why did the part number change? Did they go with a different alloy or machining process or something? Which of the two profiles given on LXForums is correct, the "old" or the "new" one?
I know for a fact that GM will make a small change to the part number of a part if a new supplier is brought into the picture. It was posted on DTW that a new supplier was brought into the picture on the cam, but nobody verified it. Then the specs pop'd up out of nowhere from STU oneday.......

Todd
 

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Discussion Starter #14
duglas said:
I have an AB CAM here at my office and I have a new AC CAM coming.. I will compair them when they get here to see if they are different.. I already have a shop lined up to install it in my Magnum as soon as I get it
Great, thanks!

One other thing ... especially if they are the same, could you see whether they match the specs we've seen on LXForums for the AB or the specs for the AC.
 

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Discussion Starter #15
artichoke said:
Great, thanks!

One other thing ... especially if they are the same, could you see whether they match the specs we've seen on LXForums for the AB or the specs for the AC.
Bump ... any more on this?
 

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too quiet

all you cam people, we're hoping to hear if this is real or imaginary.
 

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It's real. Duglas's came in today. His slipped through the system. He should be getting us some numbers soon hopefully. Hint, hint...

They canceled my order even though duglas's and mine were submitted on the same call. They are working to get this resolved with the District Sales Manager, so we'll see.
 

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Dug and X

Dug & X , so what gives, what is the verdict? Same cam or slightly modified? Same cam different vendor? Different composition? Or is it truly different specs.?

thanks,

Richard:stups:
 
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