915 clutch

[magnum10]

What is the best clutch for a 915 transmission paired with a 930 EFI engine.
Looking for street and track/race application?

[magnum10]

Hey Rob. Do you have any thoughts on a clutch i should use?
Seems like nobody knows.

Brian. I would appreciate your input. Still using your exhaust and its going strong.
I get lots of complements up in Canads, always send them your email.

[safe]

Use one that slip easy so you don't grenade the 915

[Sboxin]

Originally Posted by magnum10

What is the best clutch for a 915 transmission paired with a 930 EFI engine.
Looking for street and track/race application?

We use a Sachs SPO #3000.961.101
964 3.8L 300HP 275FtLbs with CMS race built 915

Regards,

[Sboxin]

Originally Posted by Sboxin

We use a Sachs SPO #3000.961.101
964 3.8L 300HP 275FtLbs with CMS race built 915

Regards,

New information on Sachs pressure plate - photo of failure causing damage to bell
housing and seizure of clutch to bell housing stopping engine during race = rivet
failed causing flat spring to rotate outward lathing the bell housing and catching on
the starter hole =
Regards,
Roy T
PS: changing to Kennedy pressure plate . . . bell housing will be welded and machined
by CMS

[gled49]

I had trouble with Sachs PP. Went to Kennedy ALU/ALU pressure plate with light diaphragm and street/race organic disc, clutch is heavy but works great.

[r lane]

Don't think the clutch is the issue, not sure a 915 will survive a 930 track car.

[chrismorse]

The KEP clutch, (Kennedy), is rated for 400 HP, is aluminum/aluminum, weighs a bit over 8 pounds and has triple riveted springs at each attachment point.
I'm using an organic Sachs disc and hope the diaphram isn't too stiff for my 74 year old leg
chris

[spuggy]

Originally Posted by magnum10

What is the best clutch for a 915 transmission paired with a 930 EFI engine.
Looking for street and track/race application?

A stock, or Sport clutch (standard Sach clutch cherry-picked to be in the top 10% of spec) is kind of marginal on a stock 930 - like worn out after 15,000 miles marginal. It was obviously slipping, but the gears were so short you couldn't really tell when driving it...

With the usual CIS upgrades (turbo, intercooler, headers), went through "a number" (cough) of clutches in rapid succession - all, even the "upgraded" ones, broke free before peak torque on anything more than 1/3 throttle as soon as manifold pressure climbed. Difficult to ignore/miss that...

My shop supplied a pressure plate stamped "ZF Sachs Race Engineering" and "88.3082.999.746" with a Sachs 4 puck friction plate. Pressure plate apparently the closest thing to an RSR pressure plate available at the time.

Old for sale ad here for pictures/info: WTS: 915 Sport clutch & flywheel, WEVO coupler

It required finesse on hill starts (pucks are either "in" or "out"), but never slipped under power.

However, the extra pedal pressure caused almost every original part on the cable run (brackets, levers etc) to break within a month or three. And you'd be on the verge of crying like a little girl after 20+ minutes in stop-go traffic.

Other than that, it was fine and I daily drove it for 6 years before going G50.

IMO, you should really think about your output numbers, as others have advised.... My CIS 930/60 with upgrades made 350 ft/lbs at the wheels. Quoting my own "915 for sale" thread from long ago:

Hayden (of WEVO) saying a few years ago (on this board) that 300 ft/lbs and 5000 RPM are the killer points for a 915 - that anything over 300 ft/lbs at anything below 5000 RPMs means that you're just rolling the dice, no matter how much money you spend - in other words, it's not a good investment, if you're in that ballpark.

Tuned 930's are torque monsters - most certainly in that ballpark. They make ~80% of peak torque by 3000 RPM.

Hayden is almost certainly talking FWHP numbers, too. Not "at the rollers". You can dodge it for a while, but eventually that bill be due/payable...

Despite always staying out of boost/rolling the throttle on progressively in the lower gears, the 930 did this to 2nd one day. Driving to work. In commuter traffic. You can't see it in this photo, but the base of the 5th tooth is also cracked & moving sideways...:



So, yeh, not (re)using 40 year old gearsets would seem to be a smart move in this application too...

At some power level, a G50 (or 930) transmission are the only real choices, because even a built 915 is just a more expensive grenade; you're one bad choice away from disaster. All the time. And it could still just go boom anyway. Don't even get me started on M8 bolts and undersized axles, flanges & CVs...

I went G50 before EFI because seems to me that building a car where you can't use the power defeats the entire point... EFI will almost certainly pick up another 50-75 ft/lbs over CIS if you improve induction at the same time - at which point asking a 915 to deal is just denial/silly.

The "oh, OK, it seems so obvious now" moment for me was comparing 915 and G50 parts on the bench.

[pkabush]

Yep. I agree with Spuggy. I have a upcoming backdate project with a 3.3 turbo.
Initially, my plan was to use a beefed up 915 but I recently came to my senses and bought a short box 930 trans. No matter how you slice it there’s no cheep options. But, IMO it’s going to save money in the long run. 915 rebuilds aren’t cheap.