TC engagement time?

[Flyinhillbilly]

Looking at clutch setups for my minibike for 150ft drag racing. From the videos I've seen, it appears that the torque converters have a slight delay in engaging. My engine is a professionally built briggs flathead that can turn 9000+ rpm on an old school DB30 that I'll be running 11" tires on with about a 160lb rider (I'm 215, so I've found a rider for it). I've found racing clutches that can be tuned to come in at about 5500rpm and lock solid when they hit, and I can buy one as low as a 9 tooth. The crux of my question is that would I be better off with a racing clutch or a TC? My goal is to be spinning it about 92-9500 at the finish line. With the 9t clutch and a 72t rear sprocket that puts me at an 8:1 gear ratio. Reaction time will be critical with this, and I want the best setup I can get as I don't race to lose. Any help and or opinions are greatly appreciated.

This will be my class and the guys I'll be racing. Yes, that is dual predators on the Missouri missle. That guy is a good friend of mine, and a super cool cat, but I still want to drag him down through there.

https://m.youtube.com/watch?v=Fkd21rj_iNk

 

[chancer]

I have heard that TCs are not Good over 7500RPM if that cause the belt slips.
So if you are racing and Knowing you running to the Max 9000 RPM.
I think you would not want a TC.

 

[bob58o]

What about the 3D Manual cluch?
I'd like to try that on a drag bike.

 

[Flyinhillbilly]

I'm afraid of bogging it off the line. It might not be able to make it up on the big end.

 

[bob58o]

I'm debating this same thing right now.
A 7000 RPM cam with TC or an 8000 RPM cam with clutch.
I'm thinking I want the TC, I'm leaning towards the NR 285 series with 1.2 ratio rockers
Camshaft, 285-0211: 7000 RPM. 11.0 to 1 compression or more. 26+ lb Springs Required, Small track cam for serious torque
Camshaft, 285-0611: 8000 RPM. 11.0 to 1 compression or more. Dual Springs Required, Recommended for most serious GX200s needing good mid range torque.

---------- Post added at 10:18 PM ---------- Previous post was at 09:49 PM ----------

The TC gives you some tunabilty plus Overdrive makes 7000 RPM more like 7750 RPM

 

[chancer]

The TC gives you some tunabilty plus -Overdrive makes 7000 RPM more like 7750 RPM

But can he get to 92-9500 RPM with a TC?

 

[bob58o]

But can he get to 92-9500 RPM with a TC?

I think not, I was kinda saying a different grind, with a lower powerband and a TC might be better for a 150 ft race.

Just guessing tho.

 

[Joe-405]

Just buy a adjustable bully and be done with it. You will thank me later !

Spent alot on tc's and a manual. Shoulda went with the adjustable bully in the first place. I would still be riding my mini dragbike if i did that is in the buildoff.

 

[bob58o]

Here is a related thread.
http://www.oldminibikes.com/forum/e...rformance-dry-clutch-drag-minibike-gx390.html

 

[FreeRunner15]

Drag racing and Drag racing only? well..mainly, i'm sure hahaha

Clutch!
Instant power and zero horsepower(rpm) limitations ? Heck yeAhh.

As long as you really mean the expensive multi-hundred dollar clutches.

I recall seeing some torque converters that I added to my mental Dream List because they are reaaaallyy expensive but they allow for high horsepower and torque applications.
I dont think i have the link anymore because they are too unobtainable for me, sorry. Snowmobile TorqueVerter concepts should work If you are capable of fabricating new stuff along with plenty of time and energy to do so.

 

[Joe-405]

Drag racing and Drag racing only? well..mainly, i'm sure hahaha

Clutch!
Instant power and zero horsepower(rpm) limitations ? Heck yeAhh.

As long as you really mean the expensive multi-hundred dollar clutches.

I recall seeing some torque converters that I added to my mental Dream List because they are reaaaallyy expensive but they allow for high horsepower and torque applications.
I dont think i have the link anymore because they are too unobtainable for me, sorry. Snowmobile TorqueVerter concepts should work If you are capable of fabricating new stuff along with plenty of time and energy to do so.

The ones your referring to are billet jr. dragster converters made by polar industries or similar manufacturer and start at $650.

And no on the snowmobile one working. All of them are the tapered shaft or too heavy to work properly.

 

[tazmannusa]

The comet 44 magnum might do the trick, uses the 40D/44D driven and the driver is available in 3/4"

 

[KartFab]

If you are looking at a briggs that is hopped up, you can also look into what people are putting on junior dragsters. *hint hint*

a 30 series isnt going to cut it. I know from experience that it sucks. Even when tuning the springs and driven unit for engagement, no matter what I did, it still sucked. The engine wants to rev higher, and will even pull out to 4300 rpms at launch, only to get sluggish when the torque converter starts changing ratios (probably something wrong with my gear ratio too).

Also, an engine that is built for 9000 rpms isnt going to have a good torque curve at lower rpms anyway...

Bully, Noram Cheetah, any disc type of clutch you can tune to engage at max torque for the best launch, then the pest power at the wheel once engaged because it doesnt suffer parasitic drag losses from friction etc like the torque converter does

The guys that do mini drag bikes and win races make sure their engines can wind out to the highest rpms possible with the highest compression ratios possible. You are already at a disadvantage with compression ratio since its a Briggs (i remember reading it has maybe a 6:1 compression ratio?) and flow, since its a briggs.

 

[Bbqjoe]

Oh for heaven's sake! I thought you were gonna tell us you were marrying a clutch assembly.

 

[Joe-405]

The comet 44 magnum might do the trick, uses the 40D/44D driven and the driver is available in 3/4"

No on that, I blew 3 44c's up with a mild 420cc on my mini dragbike last month or so. Cant and will not handle the rpm's

 

[Flyinhillbilly]

If you are looking at a briggs that is hopped up, you can also look into what people are putting on junior dragsters. *hint hint*

a 30 series isnt going to cut it. I know from experience that it sucks. Even when tuning the springs and driven unit for engagement, no matter what I did, it still sucked. The engine wants to rev higher, and will even pull out to 4300 rpms at launch, only to get sluggish when the torque converter starts changing ratios (probably something wrong with my gear ratio too).

Also, an engine that is built for 9000 rpms isnt going to have a good torque curve at lower rpms anyway...

Bully, Noram Cheetah, any disc type of clutch you can tune to engage at max torque for the best launch, then the pest power at the wheel once engaged because it doesnt suffer parasitic drag losses from friction etc like the torque converter does

The guys that do mini drag bikes and win races make sure their engines can wind out to the highest rpms possible with the highest compression ratios possible. You are already at a disadvantage with compression ratio since its a Briggs (i remember reading it has maybe a 6:1 compression ratio?) and flow, since its a briggs.

It's a professionally built full on race engine. Already in my possession.
It was built by one of the best race kart engine builders in the world just for drag racing my minibike. I'm leaning toward a two or three disk bully and low enough gears that I'll be turning about 9500rpm at the finish line.

 

[Flyinhillbilly]

Powerband

 

[x-Speedy-212-x]

It's a professionally built full on race engine. Already in my possession.

I'm leaning toward a two or three disk bully and low enough gears that I'll be turning about 9500rpm at the finish line.

Oh s * t. You are copying my style now?? All right. I would like to see it in the 3rd person anyways.
Hey... I am crazy and all but I, myself don't even want to go those high RPMs with my stock flywheel. Better Gear Up bruh

Safety shields. Back Cover. Bulletproof vest. Flak Jacket. Whatever you have, protect yourself. We, the viewer love this kinda stuff and don't want to see our content creator stop making crazy awesome and cool videos. Such as the dyno. When is that thing going to be done ? Wants to sees it. So I can know how to make it, if it works without much flaw.

If we were to ever race right now, I would feel the need to install some scatter shields. For the potential flying shrapnel when the magneto falls off from rubbing the magnet due to crank flex causing it to be wedged halfway into the flywheel causing further flex thus causing cracking and ultimate destruction.

 

[Flyinhillbilly]

If Jerry Dover says it's ok, then I believe him. He's been building flattys since '72. I've been bracing on the dyno a little here and there as I can find time, hopefully it'll be done within a month as next week my work load should lighten significantly. I'd like to dyno one of your cams to see an real comparison of before and after. I have a wideband already set up, and can set the timing to the optimum with the dyno. I'm really curious to see how it would change, and where in the rpm range it did change.

 

[Joe-405]

By what you posted............. 25-30 HP on alcohol ? Good choice sir. And I know cause of the stock block and not a blockzilla. Anything over 35 will split the block.