My car is to much for the dyno!!

[mobythevan]

I have heard that the Act is very quick, hard and jerky when it engages.

 

This is true, and like Sleeperz said it behaves pretty much like the clutch he is using. The flipside, the ACT clutch is rated for 500 pounds of torque, it does not slip.

[TimZ]

This is true, and like Sleeperz said it behaves pretty much like the clutch he is using. The flipside, the ACT clutch is rated for 500 pounds of torque, it does not slip.

 

Clutch Specialties can do a clutch with that same ACT pressure plate and a sprung hub, sintered iron disc, that still holds 500 lb-ft and behaves much better. I'm currently using that setup, and it works well. It isn't particularly cheap (~$500), but it works.

 

My Centerforce 2 only held until I started putting close to 300hp to the wheels.

Ditto for the CFDF, with maybe slightly higher power levels.

[datsunan]

Thanks guys, I'm at the point where I'm thinking, "how much is it worth to know that magic #..?" My clutch does not slip on the road so the only reason to change it is to see my max hp/torque, and after all isn't that why we spend this ungodly amount of money on our cars? I know that why I do it, its like crack or something! So.... what if the ramp rate was just increase a bit, so it could spin up with a bit less resistance, my clutch might not slip, I would gain Hp, but maybe lose a little torq, then It would smooth out and I could see an accuate reading of my hp-trq at 16 or ever 20 psi.......? Does my Apexi AVCR boost controler have an adjustment that would allow a slower spool? I think all I can do is adjust the duty cycle which is like the ramp control but it only controls your set point or set for a boost spike. I guess I could figure out how the speed control boost works. Thing has so many options! I'm rambling and should get back to work.

[Tony D]

From that first response to me about the CF2 or CFDF clutch, and having a DROP in the power delivery, then YEP! You got clutch going out.

 

I was at JeffP's when it started slipping (CFDF Clutch) they seem to hold fine to around 300 hp and around that much torque.

 

ufortunately the WAY the turbo makes tortque overwhelms the CF's ability to clamp at lower rpms (like 4000) and the things slip. In lower gears you pass through peak torque so fast, the little centrifugal weights can clamp and ther is no problem.

 

Let me guess, you started to loose power transmission right around 4000rpms, right?

 

That is where JeffP's took a dump. And the CFDF WILL smoke, and WILL smell like slipping clutch if you slip it consistently and badly enough!

 

Curiously it was around 20 to 23psi that it was slipping, also....

 

So I wouild say you have hit the limits of the CF clutch assembly. Jeff had dual driver rings and extra weights, blah blah blah.... Still slipped.

 

Mine is still holding, and and has since I installed it in 1991. But then again, I only dynoed it once after I installed it, flashed to 325hp, and then turned the boost back down to 275hp, and was happy with that since my wife was driving the car....

 

If you don't want a jerkey clutch, consider a dual or triple plate organic clutch. HKS and OS Giken make them. But they are around $1500. They are smooth as glass on engagement, and if you swap from organic to ceramic friction material the torque holding capabilities go to unreal numbers.

[Guest bastaad525]

From what I've seen, a lot of turbo guys (supra's, DSM's) with very powerful cars that do ANY street driving, tend to go with carbon/carbon clutches with a heavy duty pressure plate.

 

I've heard many times that this setup results in only a moderately stiffer than stock pedal, and stock-like smooth engagement, yet the clutch has no problem holding massive amounts of power again and again and putting up with a lot of abuse.

 

 

I have no idea how much those wonder-clutches cost but I imagine it ain't cheap

 

 

If you have the money though you'd be MUCH better of than going with those ACT puck-style clutches... the chatter sucks *** and the pedal is VERY stiff... if you ever get caught in traffic you will be hating life. I had an ACT six puck for a while because some people convinced me I needed it... drove that for about 2 years, and now I'm using a STOCK clutch disc with heavy duty pressure plate... it is sooooo much better. Unfortunately, and I"m not even exagerating about this... I seem to have done some kind of permanent damage to my leg from driving that other clutch so long. I still get aches in my left shin almost every day.

 

 

I say look into those carbon-carbon setups or even a multi clutch setup, the cost will be high but you'll thank yourself later.

[Tony D]

Chatter comes from run-out and those damnable springs in the hub center. I ran a solid Centered disc four-puck clutch for years in my VW, with never any chatter. Went to a spring centered disc, and it started grabbing.

 

I was told some time ago if you can't get a car to launch smoothly with a solid centered clutch disc, you don't know how to use a clutch right. I tend to agree, with the solid center, modulation and actually slipping the clutch (even a puck style) is possible. Not particularly easy since it becomes grabbier the more you slip it... But it CAN be done! (I'll remind you this is with a 1934 era designed CABLE clutch linkage, too, not the antiseptic Hydraulic Actuators we have in the Z!)

 

Come to think of it, the Corvair had a launch problem with the six puck disc until we had it changed to a solid center style.

[Guest bastaad525]

The 6 puck ACT I ran for a couple years was solid-centered, not sprung.

 

After a while I became very good at modulating that clutch and could actually roll from a stop light with no chatter at all. The only time I got chatter anymore was when in reverse. It really was a strain though, letting that pedal out slowly enough to get a smooth rolling start... the pedal was just SO stiff.

 

So does that mean I truly know how to use a clutch?

 

I had a few people advise me that I should have swapped out for the 6 puck with the sprung center... back when I first got the clutch and I hated how bad it chattered... a few guys told me the sprung ones dont' chatter nearly as much. But you're saying it would have brought my chatter back, am I understanding you right?

[Clifton]

Sprung hubs are only to minimize driveline shock during shifts. Does nothing for easing engaugement. The marcel is what makes a clutch easier to slip and aid engaugement.

 

I have got a few clutches from Clutchspecialties also 7M and L28. I was running a 6 puck with a stock PP on the 7M. 4 puck on the L28. A puck disk with a stock PP will give alot more torque holding capability for not alot of money. If you are about at the limit and you go through the gears a few times and put soem heat into it it will slip.

[datsunan]

Yup thats what happened the night at the drags when it slipped, to many smokey burnouts and slipping the clutch on launch, I thought thats what made it slip. Who made the clutch you were getting from clutchspecialies? What kind of power were you throwing at it?

[TimZ]

Who made the clutch you were getting from clutchspecialies? What kind of power were you throwing at it?

 

My last best dyno pull was 467hp, 437lb-ft at the wheels on a dynojet. This was with the sintered iron setup I was referring to earlier. I believe that I'm making more than that now with the new cam, although I have not had a chance to dyno it. Not had problems yet. I get a very small amount of chatter on soft launches in traffic, but I have a fairly tall 1st gear (~50mph at 7000rpm in first). It's far better than the six puck clutch I had in there before.

[Guest bastaad525]

Conversely, a heavy duty pressure plate and stock clutch disc will ALSO give you much more torque holding capacity for VERY cheap, while also not giving any of the bad symptoms of the metalic puck-style clutches

 

Jmortensen recommended this setup to me and I can't thank him enough.

 

I"m now running a stock clutch disc with a Daikin heavy duty pressure plate (the part is actually specified for a Nissan Pickup truck). The set including throwout bearing cost me $120. I'm putting 240ish rwhp and just over 300ftlbs of torque to the wheels and have never had the clutch slip once, even after MUCH abuse slipping it to lauch with boost.

 

Unless I ever reach a power level where I have to, I will NEVER go back to a puck-style clutch.

[TimZ]

Conversely, a heavy duty pressure plate and stock clutch disc will ALSO give you much more torque holding capacity for VERY cheap, while also not giving any of the bad symptoms of the metalic puck-style clutches

 

Not sure if I was clear on this - the sintered iron disc that I mentioned is not a puck sytle disk

[datsunan]

Damn Tim! What have you done to that car to get that much power? Have you seen my list of mods? What would you recomend that I do next for more power? Oh by the way thank you all for the help with my clutch selection.

[z-ya]

We have had similar problems with my turbo Z and a customers turbo Z on a Dynapack. If the ramp rate is too high when we are doing a standard pull (not fixed load or RPM), the thing starts bucking like a bronco, and you can smell the clutch. Its like the engine is fighting the dyno, and the dyno is fighting back. All this surging torque is too much for the clutch. I suppose we lost some material on the clutch disk, but it doesn't slip on the street.

 

The dyno dynamically varyies the load to match the torque at the wheels. If this ramp rate too steep, the car and dyno start oscillating (kind of like a tank circuit for you EE types). It's a little scary for sure because the frequency of the oscillation gets faster and faster.

 

With the Dynapack you can select many dfferent ramp profiles. You can also adjust the load directly like a Dynojet. Anyway, we found one that works well with L6 turbos. The Dynapack is an awesome tuning tool for sure.

[datsunan]

Hey Pete, what was the ramp rate you used? Maybe I could tell my dyno guys to give it a try. Hows New Hampshire? Use to have a cottage on lake Wentworth off Winni till my bitch of a stepmonster sold it when my dad died. I love it there.

[Drax240z]

For your car I would use 15.0km/h/s to 17.5km/h/s on a dyno dynamics unit. (150 to 175 on the handheld)