Comp 918 Springs?
07-22-2005, 08:20 AM
#11
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Motohead's runs pretty good, I got to see it in Dallas recently. No lope, although I hear there is an occasional misfire generated but it does not put the truck into "limp mode" or shutdown.
The smallest CC ( 260 ) is the best compromise right now. The other two ( 268 and 273 ) use a very tight LSA, 108 degrees or so, that causes low idle vacuum that the computer can't handle. There are a few shops working this issue as we speak, so hopefully someone will rewrite the MAP code and increase the idle slightly to keep us smiling and running with the rest of ya!
BTW I am installing the 260 in mine ( instead of the 6.1L cam ) and will report on the results. Hope to be running by Monday but you know how these things go....
The smallest CC ( 260 ) is the best compromise right now. The other two ( 268 and 273 ) use a very tight LSA, 108 degrees or so, that causes low idle vacuum that the computer can't handle. There are a few shops working this issue as we speak, so hopefully someone will rewrite the MAP code and increase the idle slightly to keep us smiling and running with the rest of ya!
BTW I am installing the 260 in mine ( instead of the 6.1L cam ) and will report on the results. Hope to be running by Monday but you know how these things go....
07-22-2005, 02:39 PM
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Originally Posted by ktmrider
Motohead's runs pretty good, I got to see it in Dallas recently. No lope, although I hear there is an occasional misfire generated but it does not put the truck into "limp mode" or shutdown.
The smallest CC ( 260 ) is the best compromise right now. The other two ( 268 and 273 ) use a very tight LSA, 108 degrees or so, that causes low idle vacuum that the computer can't handle. There are a few shops working this issue as we speak, so hopefully someone will rewrite the MAP code and increase the idle slightly to keep us smiling and running with the rest of ya!
BTW I am installing the 260 in mine ( instead of the 6.1L cam ) and will report on the results. Hope to be running by Monday but you know how these things go....
The smallest CC ( 260 ) is the best compromise right now. The other two ( 268 and 273 ) use a very tight LSA, 108 degrees or so, that causes low idle vacuum that the computer can't handle. There are a few shops working this issue as we speak, so hopefully someone will rewrite the MAP code and increase the idle slightly to keep us smiling and running with the rest of ya!
BTW I am installing the 260 in mine ( instead of the 6.1L cam ) and will report on the results. Hope to be running by Monday but you know how these things go....
We have not had the chance to line them up as of yet but we will soon.
I just want to get my stall and gear in.
I have them both just don't have the time to do any work on my truck.
07-22-2005, 03:26 PM
#14
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Originally Posted by Fandango
Why the narrow LSA?
I assume the 260 is advertised duration. Got any numbers at .050 or .200?
I assume the 260 is advertised duration. Got any numbers at .050 or .200?
The 260 number is the gross duration, correct. The specs on the cams are:
Duration ( 0.050 lift ) Lift
Stock 196 / 196 0.477 / 0.462
XFI260 208 / 212 0.522 / 0.525
XFI268 224 / 228 0.547 / 0.550
07-22-2005, 04:02 PM
#15
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Overlap:
The narrow LSA creates a "scavenging" effect in the cylinder. The exhaust and intake valves are open at the same time on the end of the exhaust stroke. The exiting gases create a larger vacuum effect and helps suck more intake charge into the cylinder. This is great for extra power, bad for idle vacuum ( less of a signal ) and really bad for emissions ( unburned fuel going into the exhaust ). It's an old practice on N/A motors.
08-02-2005, 12:23 AM
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Originally Posted by ktmrider
The narrow LSA creates a "scavenging" effect in the cylinder. The exhaust and intake valves are open at the same time on the end of the exhaust stroke. The exiting gases create a larger vacuum effect and helps suck more intake charge into the cylinder. This is great for extra power, bad for idle vacuum ( less of a signal ) and really bad for emissions ( unburned fuel going into the exhaust ). It's an old practice on N/A motors.
The 260 number is the gross duration, correct. The specs on the cams are:
Duration ( 0.050 lift ) Lift
Stock 196 / 196 0.477 / 0.462
XFI260 208 / 212 0.522 / 0.525
XFI268 224 / 228 0.547 / 0.550
The 260 number is the gross duration, correct. The specs on the cams are:
Duration ( 0.050 lift ) Lift
Stock 196 / 196 0.477 / 0.462
XFI260 208 / 212 0.522 / 0.525
XFI268 224 / 228 0.547 / 0.550
I understand the LSA pretty well.
But why not grind it on something more computer friendly? 115 or something like that?
08-02-2005, 09:29 AM
#17
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Sorry about the exessive details, can you tell I am a technical instructor? ;-)
I agree they shoulda cut it with a little more LSA or overlap, but then the power increases would not justify the cost/swap. It would not be a big deal if we could reprogram the PCM for the decreased vacuum signal but for now you wold need to live with the rougher idle and occasional codes.
Hey Fandango, I am in the Bay area right now and see you live in Castro Valley. Staying here thru 8/12, maybe we can hook up?!?
I agree they shoulda cut it with a little more LSA or overlap, but then the power increases would not justify the cost/swap. It would not be a big deal if we could reprogram the PCM for the decreased vacuum signal but for now you wold need to live with the rougher idle and occasional codes.
Hey Fandango, I am in the Bay area right now and see you live in Castro Valley. Staying here thru 8/12, maybe we can hook up?!?
08-02-2005, 02:57 PM
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Hey Mike- hows it goin with the new motor? Sounds like it's going well.
I'm going with the KRC custom nitrous/ supercharger grind cam. Here's the specs: 220/230-547/557 114 It's a custom grind of the Comp 268 I believe. They are installing the Apexi SAFC II to control vaccum so it will idle corrcetly and not stall out at stops.
KRC is working with a handheld tuner company to make the cam swap an option on the new tuner. I s/w KRC today and they mentioned that the tuner company wants my truck once the cam and springs are installed but before the Apexi unit so they can get the specs in order to make the cam swap option available. I know it won't be available on the first run of tuners, I've heard they are offering them before they get my truck. But, once they get the specs I'm sure it'll be an option very soon. Then I'll get one- I hear the killing of torque management with the ones about to be released is unreal. Imagine that with raised rev limit and cam.
I can't wait!
I'm going with the KRC custom nitrous/ supercharger grind cam. Here's the specs: 220/230-547/557 114 It's a custom grind of the Comp 268 I believe. They are installing the Apexi SAFC II to control vaccum so it will idle corrcetly and not stall out at stops.
KRC is working with a handheld tuner company to make the cam swap an option on the new tuner. I s/w KRC today and they mentioned that the tuner company wants my truck once the cam and springs are installed but before the Apexi unit so they can get the specs in order to make the cam swap option available. I know it won't be available on the first run of tuners, I've heard they are offering them before they get my truck. But, once they get the specs I'm sure it'll be an option very soon. Then I'll get one- I hear the killing of torque management with the ones about to be released is unreal. Imagine that with raised rev limit and cam.
I can't wait!
08-09-2005, 04:11 PM
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Originally Posted by ktmrider
Motohead's runs pretty good, I got to see it in Dallas recently. No lope, although I hear there is an occasional misfire generated but it does not put the truck into "limp mode" or shutdown.
The smallest CC ( 260 ) is the best compromise right now. The other two ( 268 and 273 ) use a very tight LSA, 108 degrees or so, that causes low idle vacuum that the computer can't handle. There are a few shops working this issue as we speak, so hopefully someone will rewrite the MAP code and increase the idle slightly to keep us smiling and running with the rest of ya!
BTW I am installing the 260 in mine ( instead of the 6.1L cam ) and will report on the results. Hope to be running by Monday but you know how these things go....
The smallest CC ( 260 ) is the best compromise right now. The other two ( 268 and 273 ) use a very tight LSA, 108 degrees or so, that causes low idle vacuum that the computer can't handle. There are a few shops working this issue as we speak, so hopefully someone will rewrite the MAP code and increase the idle slightly to keep us smiling and running with the rest of ya!
BTW I am installing the 260 in mine ( instead of the 6.1L cam ) and will report on the results. Hope to be running by Monday but you know how these things go....
08-11-2005, 11:02 AM
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Well my cam and springs are in BUT I had to leave my baby in FL for another week or so. They are having to do some "extra" work so I left her. They were able to fire her up and believe it or not she caught idle the first time! Didn't stall. And with the KRC 220 you can definitley tell it's a cammed hemi. Nice LOPE. My buddy went to FL with me so we got the video on his camera. He's uploading it, I'll post a link asap. It's sweeet.
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