ViperExchange Heads/Cam car goes 10.5@139

[rlhay2]

One things that appears to be definitive is that the OEM clutch is not at all acceptable for tq values above what a bolt on car can generate.

[swexlin]

One things that appears to be definitive is that the OEM clutch is not at all acceptable for tq values above what a bolt on car can generate.

True, but maybe only in a drag-race situation? Perhaps for more "normal" ( if there is such a thing with a Viper) it might hold up. Andy can chime in here.

[slowhatch]

I do not think the clutch issue is a matter of lacking clamping load to hold the tq, but more so an issue of hydraulics and heat in the engine bay. Its not like the clutch is slipping, its just failing to disengage/engage after the lines are heat soaked with a burnout. I only saw issues on the shifts during all the passes.

[Tiago]

if the pedal is not working, staying on the floor, or not actually moving the slave cyl, then yes it is a hydraulics problem, but the clutch itself could also be fubar and not allow the shift.

[Jack B]

My factory clutch slipped, two BBG clutches slipped, a modified factory clutch slipped - my McLeod Clutch with the same hydraulics does not slip.You be the judge.

One step further, at the strip, I am sure that some individuals confuse the clutch slipping with wheel spin, especially past the sixty.

I do not think the clutch issue is a matter of lacking clamping load to hold the tq, but more so an issue of hydraulics and heat in the engine bay. Its not like the clutch is slipping, its just failing to disengage/engage after the lines are heat soaked with a burnout. I only saw issues on the shifts during all the passes.

[7TH_SIGN]

Andy, I want you to get Dick Winkles to make you an 87 octane drag strip tune. Then I want you to go run with the skinny tires on the back. Or maybe some winter tires. Until then, your package isn't validated. Shame on you for telling us all the specifics of your setup, and disclosing every aspect of your testing. That is too much information, and we cannot process it at an expert level.

Thanks,
President, 87 Octane Drag Racing Winter Tires Association.

LOL! That is funny. At the same time, considering Flatout represents the VE H/C package from a product advertisement standpoint more than anyone else in our community, its nice to know what fuel is being used when posting product results. I'm sure it wasn't his intent to mislead anyone.

[ViperDog]

Jack B, does the McLeod clutch have higher pedal effort? I couldn't care less about this because I have a healthy left leg and prefer clutches with some feel to them but want to understand the tradeoffs in performance clutch design.

Andy, would wrapping the hydraulics as much as possible with heat insulation help?

[FLATOUT]

So I wasn't getting any "slipping" at all. I have had this happen in three specific instances. Shifting into 5th gear at the end of the straight at COTA and shifting into 5th at Project X, and this past weekend at the drag strip on drag radials.

The more I think about the drag strip problem the more I think it's not heat related. I run SRF fluid in the resevoir and it was brand new, all lines wrapped in lava mat and heat sheathed all the way to the trans, and the shield by the header primaries was also wrapped in lava mat.

It doesn't do it on the street on the 1-2 because the car doesn't hook up as well and there's not that tremendous force on the driveline like there is when the car is hooking in first at the drag strip.

I was talking with Dan Cragin last night and he thinks the the stock organic material can actuall swell some not allowing the clutch to completely dissengage between the shifts. That makes some sense and if I switched to a non organic disk and it went away that would make sense.

I know at the drag strip that the clutch pedal after the burnout did not feel mushy at all. I would do a very small burnout and then pump the pedal 5-10 times and even let the car cool for just a second before I pulled up to the line. I would then launch the car very soft and it would still not want to disengage.

Interesting.

Andy

I do not think the clutch issue is a matter of lacking clamping load to hold the tq, but more so an issue of hydraulics and heat in the engine bay. Its not like the clutch is slipping, its just failing to disengage/engage after the lines are heat soaked with a burnout. I only saw issues on the shifts during all the passes.

if the pedal is not working, staying on the floor, or not actually moving the slave cyl, then yes it is a hydraulics problem, but the clutch itself could also be fubar and not allow the shift.

My factory clutch slipped, two BBG clutches slipped, a modified factory clutch slipped - my McLeod Clutch with the same hydraulics does not slip.

You be the judge.

[FLATOUT]

if the pedal is not working, staying on the floor, or not actually moving the slave cyl, then yes it is a hydraulics problem, but the clutch itself could also be fubar and not allow the shift.

This is what I think was happening. It was odd to me that the 2-3 and the 3-4 shift was just as crisp and clean as it had always been with the clutch disengaging no problem. There's not nearly as much torque on the drive line up there as there is from a dig in first so that was what got me thinking that it was a force related issue and not a heat related issue.

[Nine Ball]

A friend of mine was the drivetrain development engineer for the C6 Corvette (all models). As you know, Corvettes have the same "mushy pedal" issue when hard launches are made. They don't disengage properly at high rpm, and prevent shifting properly. Two issues here, which he found.

1. Hydraulics getting hot, changing the fluid properties. Inside the bellhousing is also very hot after a hard launch or burnout, that slave cylinder can heat the fluid too.
2. The fingers on the pressure plate are springs. Their metallic spring properties change when hot. Meaning, the fingers reduced in spring rate when ultra-hot, and sometimes wouldn't be strong enough to push back. Hence the mushy pedal.

Jack's observation on the clutches he's tried with the same hydraulics, seems to support #2 here. Weak pressure plate fingers, which hate heat.

[FLATOUT]

Yep I think you guys are right. I'll throw the McLeod in there and see what happens. Alex has a group with another rental in early January, if they have an extra spot I will squeeze in and see if I notice an improvement.

Andy

A friend of mine was the drivetrain development engineer for the C6 Corvette (all models). As you know, Corvettes have the same "mushy pedal" issue when hard launches are made. They don't disengage properly at high rpm, and prevent shifting properly. Two issues here, which he found.

1. Hydraulics getting hot, changing the fluid properties. Inside the bellhousing is also very hot after a hard launch or burnout, that slave cylinder can heat the fluid too.
2. The fingers on the pressure plate are springs. Their metallic spring properties change when hot. Meaning, the fingers reduced in spring rate when ultra-hot, and sometimes wouldn't be strong enough to push back. Hence the mushy pedal.

Jack's observation on the clutches he's tried with the same hydraulics, seems to support #2 here. Weak pressure plate fingers, which hate heat.

[Jack B]

The McLeod effort is similar to the oem, however, the release point is more precise. The only disadvantage is that it is harder to slip, which would only affect drag racing. I have always had all the hydraulics wrapped and insulated.

I do not think that a perfectly functioning clutch gets a lot hotter when the track is prepped, however, that is if the clutch is not slipping. I still feel the clutch is acting somewhat like a torque converter and there is inherent slip on a prepped track, that is where the heat gets into the clutch and Dan is correct, unless the disk is metallic in nature, it can swell. That swelling is exacerbated by the twin disk design. With the twin and triple designs, you have several surfaces that have to disengage. Personally, I think the strapped designs have a harder time disengaging.

Sort of interesting, I had the oem disk resurfaced with metallic material on one side and Kevlar on the other side. They were also converted to a petal type configuration. It shifted fine till I put on the slicks, the Kevlar heated up because the clutch was slipping, the Kevlar expanded and would not allow the clutch to disengage.

Jack B, does the McLeod clutch have higher pedal effort? I couldn't care less about this because I have a healthy left leg and prefer clutches with some feel to them but want to understand the tradeoffs in performance clutch design.

Andy, would wrapping the hydraulics as much as possible with heat insulation help?

[slowhatch]

A friend of mine was the drivetrain development engineer for the C6 Corvette (all models). As you know, Corvettes have the same "mushy pedal" issue when hard launches are made. They don't disengage properly at high rpm, and prevent shifting properly. Two issues here, which he found.

1. Hydraulics getting hot, changing the fluid properties. Inside the bellhousing is also very hot after a hard launch or burnout, that slave cylinder can heat the fluid too.
2. The fingers on the pressure plate are springs. Their metallic spring properties change when hot. Meaning, the fingers reduced in spring rate when ultra-hot, and sometimes wouldn't be strong enough to push back. Hence the mushy pedal.

Jack's observation on the clutches he's tried with the same hydraulics, seems to support #2 here. Weak pressure plate fingers, which hate heat.

That makes a lot of sense, thanks for sharing.

[98intrigue]

This is what I think was happening. It was odd to me that the 2-3 and the 3-4 shift was just as crisp and clean as it had always been with the clutch disengaging no problem. There's not nearly as much torque on the drive line up there as there is from a dig in first so that was what got me thinking that it was a force related issue and not a heat related issue.

My 2-3 shift issues were not heat related. I could take the car out of the garage and drive it gently until up to operating temps...then do a 2-3 gear pull, but 3rd gear would not engage. If I could scale my shifting speed 1-10 with 10 being the fastest shift possible (lifting), 3rd gear would not engage 8 out of the 10 times when shifting at a speed of 10. Shifting at a speed of 5, never 1 issue. Shifting at a speed of 8, never 1 issue.

It does make sense that potentially the clutch was not fully engaging when trying to shift hard, but in my case it was not a heat related issue.

[slowhatch]

My 2-3 shift issues were not heat related. I could take the car out of the garage and drive it gently until up to operating temps...then do a 2-3 gear pull, but 3rd gear would not engage. If I could scale my shifting speed 1-10 with 10 being the fastest shift possible (lifting), 3rd gear would not engage 8 out of the 10 times when shifting at a speed of 10. Shifting at a speed of 5, never 1 issue. Shifting at a speed of 8, never 1 issue.

It does make sense that potentially the clutch was not fully engaging when trying to shift hard, but in my case it was not a heat related issue.

There are many many factors here that would create issues, and I doubt people would admit to driver error. I had an "issue" with grinding 3rd gear for a few days out of the blue, then i figured out I had bumped my seat forward by an inch. That caused me to not be disengaging the clutch fully before I grabbed 3rd. Scooted the seat back into regular position never had a problem again.

[Nth Moto]

Great runs Andy, 139mph in an OEM like package naturally aspirated is really not something to scoff at. There was a time when people would be excited about that with forced induction.

In reference to all the clutch talk; the day anyone puts a true carbon disc/carbon floater multi-disk clutch in a car that is properly designed and setup you will never, ever want to go back.

[FLATOUT]

Great runs Andy, 139mph in an OEM like package naturally aspirated is really not something to scoff at. There was a time when people would be excited about that with forced induction.

In reference to all the clutch talk; the day anyone puts a true carbon disc/carbon floater multi-disk clutch in a car that is properly designed and setup you will never, ever want to go back.

Thanks Aaron every time you talk about the carbon clutches it makes me want one I haven't decided which route I am going to go yet but I need to do something for dig runs, the stocker worked fine everywhere else at my power level.

[FLATOUT]

There are many many factors here that would create issues, and I doubt people would admit to driver error. I had an "issue" with grinding 3rd gear for a few days out of the blue, then i figured out I had bumped my seat forward by an inch. That caused me to not be disengaging the clutch fully before I grabbed 3rd. Scooted the seat back into regular position never had a problem again.

I agree with you 100% on driver error and I made adjustments to seating position and pedal postion after the first two passes. It was the 1-2 shift which is pretty much the easiest one out there, but I agree other changes can be tricky. I even played around with how I engaged the pedal but nothing changed the outcome except for slowing the shift way down.

[rlhay2]

In reference to all the clutch talk; the day anyone puts a true carbon disc/carbon floater multi-disk clutch in a car that is properly designed and setup you will never, ever want to go back.

I should certainly hope so. $7000 worth of buyer's remorse would really suck!!

[Nth Moto]

I should certainly hope so. $7000 worth of buyer's remorse would really suck!!

Indeed it would, which is why it's a good thing they're not all $7000! Please see here - $3885 and already proven to hold over 1300 TQ @ the wheels in a Gen V, but can still be modulated and slipped.

http://driveviper.com/forums/threads...-Carbon-Clutch

[TurboTA]

wow. impressive

[98intrigue]

I agree with you 100% on driver error and I made adjustments to seating position and pedal postion after the first two passes. It was the 1-2 shift which is pretty much the easiest one out there, but I agree other changes can be tricky. I even played around with how I engaged the pedal but nothing changed the outcome except for slowing the shift way down.

I'd admit if it was driver error... I even mentioned that it the thread I started. I've also tried adjusting the seating position and pedals to see if maybe I wasn't fully engaging the clutch before shifting, but that was no help. I would go WOT in 2nd to redline, clutch in, and try to put it in 3rd, but you could hear the synchros fighting right away. The only way to alleviate the issue was to slow my effort of shifting into 3rd. Either way, I have a new transmission on order.

[cashcorn]

^^^how does your clutch look?

[Jack B]

What type of lead time on the trans?

I'd admit if it was driver error... I even mentioned that it the thread I started. I've also tried adjusting the seating position and pedals to see if maybe I wasn't fully engaging the clutch before shifting, but that was no help. I would go WOT in 2nd to redline, clutch in, and try to put it in 3rd, but you could hear the synchros fighting right away. The only way to alleviate the issue was to slow my effort of shifting into 3rd. Either way, I have a new transmission on order.

[98intrigue]

^^^how does your clutch look?

What type of lead time on the trans?

Sorry, guys...I don't want to derail this thread. My thread is posted here: http://driveviper.com/forums/threads...mission-issues