too bad you dont race with NASA. i primarily race with NASA and go to VIR at least twice year. I mostly run in northeast tracks.

Watkins Glen is on my bucket list

Glen is an awesome track. scare the shit out of me but i love it. check out PittRace also, I think i like that more than Glen now.

so after getting the car back together, i start the car up and let it warm up. then it push the clutch down to get it in gear and the car would lurch forward and doesnt want to go in gear, i tried several times in different gear and its the same. i even put the car in gear and try to start it in gear with clutch down and the car would lurch forward. so the clutch is definitely dragging. i couldn't figure out why. then i tired something else. with the engine running, i put slight pressure on the shifter to put in gear, then press down the clutch slowly till it slide into gear. boom. that's when i realize that the over travel of the pedal cause the clutch to drag. the clutch has a very narrow window of disengagement, anything over that would cause it to reengage. i had already made a pedal stop but i didnt have it turned out far enough. i end up having to turn the pedal stop out so far, for the perfect clutch release, that the clutch pedal wouldnt engage the low switch to start the engine. i had to add a half inch spacer just so the pedal could engage the low switch to start the engine. i probably took about half of my clutch travel out. which is great, less clutch pedal travel

the clutch grabs like crazy, but can still slip if you try, doesnt chatter much. there's no engine momentum at all when taking off from stop. rpm drop so quick between shift. and if you take it out of gear coming to stop, rpm drop so quick then engine stalls out. gotta keep it in gear till rpm drop low enough then take it out of gear.

Yeah, they have a very narrow window of adjustment that is acceptable - about 1/4" actually. You have to be careful, because if you overstroke the pressure plate it will mess it up. Follow the instructions carefully.

That is a separate problem from clutch drag, however. If the pedal isn't adjusted right and you have too much travel, you will actually re-engage the clutch, which is what it sounds like happened for you this time.

Yeah definitely wasn't clutch drag but clutch re-engagement. I haven't driven the car hard and shift at redline yet. Still taking it easy to break in the new 5.1 FD and osg diff.

Fast Rev
 

I had mentioned that the aluminum flywheel and 5.5" clutch revs super fast. I found one of my blooper videos where the lighting was just right so you can see my feet and the throttle blips.

I figure its worth showing

nice, yeah i'm pretty decent with heel/toe but i dont think the throttle by wire react as fast as cable throttle when it comes to a quick throttle blip.

Is there any truth to this or is it just how you feel about it?

i had my first track event last weekend with the new clutch setup. the clutch felt amazing on track. shift was lightning quick and effortless. can feel the synchro doesnt have to work very hard, with the low inertia of the small disks. also probably because the rpm drop so fast that synchro doesnt have to do much to match the speed of the disk to the engine. getting the car moving from a stop is a pain. have to rev it up pretty high and ease off the clutch or it will stall. idle is also not very stable sometimes. i did drive it on the street for about 300 miles to break in the clutch and and final drive. definitely not DD friendly. getting on the trailer is not as bad as i thought. i pull the car up the ramp to line it up. then back up about 5 feet and get a running start up the ramp. didn't have to slip the clutch much. if you're car is primarily a track car, i would highly recommend this setup. it would probably make the tranny last longer also.

my tranny was grinding going into 5th at the last event last year. and i never had to use 6th on track. with the new clutch setup, i can bang into 5th without any issues. and getting into 6th is a breeze also, which i have to do a lot now with the 5.1 FD.

here's a short vid from last weekend.

Nice driving man, I can see what you mean. I'm going to have to pick your brain when I start my "24 Hours of Lemon Racing" thread in here when my Noob 30 days are up so I can start a thread. Your temp looks pretty solid.

Generally speaking, when you go to the smaller clutch sizes the PP doesn’t need as much actuation/pedal travel. Most of the mini PPs need a pedal stop added to prevent overthrowing & damaging it. So the thing to do if possible is to swap out to a larger diameter slave/release cylinder.

This not only decreases the amount of TB throw relative to pedal travel, it also increases the applied force to the throw-out bearing pivot arm. Which in turn decreases the pedal force on your leg and is helpful with high PP spring rates. It also helps with the engagement/slip control when releasing the clutch to move/launch the car forward.

FEED/Fujita Engineering sells a 21mm slave to replace the OE 19mm unit for this purpose. You’ll still need a clutch stop on the mini-clutches. Also a bit pricey compared to buying the OE slave; around $210/shipped from JP.

https://www.japanparts.com/parts/detail/18736

I tried to find an OE equivalent to save money, but gave up and just ordered it from them instead. My car is still not running yet to try it out though. Common mod for FD3 RX7TT cars using stiff /multi-disc clutches.

good info on the larger slave to reduce pedal pressure and elongating the engagement point. The QM had a very stiff pedal pressure, so i'm sure a larger slave cylinder would have reduced that pressure. i switched to Tilton because they offered three different pressure plate force. i went with the lightest one they had. pedal pressure is just a tab stiffer than the gas pedal, it's awesome. i also had to make a pretty long pedal stop, so pedal travel is short, which is also great for me since i'm short and usually have to tip toe the clutch pedal to fully disengage, but with the pedal stop, i dont have to anymore.

when i put the car on the dyno, after only putting about 200 easy street miles on the new clutch to break in the final drive, i think the clutch was slipping a little on the top end for the first few pulls. i thought the tires was slipping on the drum but there's no way it would slip with only 130 torque. but after a few pulls, it stop slipping. my guess is the disks wasn't fully bedded in during break in.

maybe ill go with the medium pressure plate spring when it's time to rebuild the clutch. the lightest spring that i have is rated for 300 torque.

A strong Renesis engine will make around 190 lb/ft torque at the flywheel. These smaller clutch discs are going to wear faster than a larger clutch. When you use the lighter PP you’re more likely to get caught out with a slipping clutch between maintenance inspections.

For Tilton the stiffest high-ratio PP will allow for the longest disc wear before slippage occurs.

https://cimg1.ibsrv.net/gimg/www.rx8...d1faf39b86.png


If you’re running the 2-disc cerametallic then you probably want the 480# PP, imo. I pushed in the pedal with one on the std slave setup and it didn’t seem stiff to me at all. Similar to a stock clutch.

the clutch was brand new with about 200 street miles. so i don't think there much wear on the disks. it felt like it was slipping on the dyno for the first couple pulls then it stop slipping. the pedal fells very light, just slightly stiffer than the gas pedal. i plan on servicing the clutch at the end of each season. sooner if it's required. i do about 30 track days a year.

https://cimg1.ibsrv.net/gimg/www.rx8...cfc603304e.jpg

Well if it lasts that long. Not saying it won’t though. I wasn’t implying anything about the initial issue you had or anything else really. It’s just general information for anyone else considering going that route. Based on what I already posted, I’d imagine the 2-disc 300# PP feels a lot lighter than the factory clutch.

But to put it into perspective, on the disc wear vs torque capacity image I posted in the previous reply above; take that same green line and put it about 1/3 lower than where it is and that would be the comparison between where your 300# PP is compared to the 480# PP being the existing green line. That’s mostly what I was trying to explain and also that people shouldn’t necessarily think they’ll get a super stiff pedal making that choice. It might make it a bit more on/off, but the larger slave cylinder will help offset that and if for some reason the clutch discs wear you’ll have more torque capacity coverage before it slips.

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I have it On my 13B PP rx7
Love it really change the engine response

Here are old video of my with oldschool mazdaspeed fltwheel with 4.5 inch
But is similar idea

wow i cant imagine a 4.5" clutch. my engine revs insanely quick, and shift super quick. my s1 tranny felt really notchy getting into 5th, would grind if i shift quick. after installing the 5.5", the tranny felt great and i could powershift any gears without issues.

vid of my recent event.

It’s not necessarily quicker depending on what it’s being compared to. It all depends on the mass and how it’s distributed. It’s also approaching the zero-sum gain of % difference. Pretty sure that’s why Tilton doesn’t offer anything less than 5.5” for metallic. I’ve never seen QM post this info, but for Tilton comparison:

7.25” Twin metallic
Weight**: 7.5 lbs/3.4 kg
M.O.I.**: 66.3 lb-in2/.0195 kg-m2

7.25” Twin carbon
Weight**: 6.2 lbs/2.8 kg
M.O.I.** (Step): 52.81 lb-in2/.0155 kg-m2
M.O.I.** (Pot): 52.26 lb-in2/.0153 kg-m2

5.5” Twin metallic
Weight**: 5.7 lbs/2.6 kg
M.O.I.**: 29.8 lb-in2/.0087 kg-m2

5.5” Twin carbon
Weight: 3.7 lbs/1.7 kg
M.O.I.: 17.8 lb-in2/.0052 kg-m2

5.5” Triple carbon
Weight: 4.4 lbs/2.0 kg
M.O.I.: 22.0 lb-in2/.0065 kg-m2

4.5” Twin carbon
Weight: 2.6 lbs/1.2 kg
M.O.I.: 11.4 lb-in2/.0033 kg-m2

4.5” Triple carbon
Weight: 3.2 lbs/1.5 kg
M.O.I.: 12.3 lb-in2/.0036 kg-m2
.

When I don't have trailer back then, I use to drive this set up on street to track
To get my life a bit easier , I bought a Rally disc
Which is a bit thicker then normal road race disc

Did you happen to weigh the OE clutch? I can’t seem to find a weight for one anywhere and never thought to check it myself.

Just weighed my used oem clutch which still has a lot of meat left on it, came out to 16.2 lbs, disk and pressure plate.

I was assuming 15 lbs, so not far off. On page 1 you didn’t mention that you must also use the auto counterweight, which adds another 3.6 lbs to the overall combined weight of the race clutch/flywheel assembly

thanks

You are right, good point about the counter weight. That weight is pretty close to center tho. The rev is insanely quick.

Yes, but it still adds static weight on the scales :)