S3 E38. We road test the new comet 94c clutch on our 670 predator powered Renault.

Season 3 Episode 38. Jimbo reassembles the 670 cc Predator powered Renault and takes it on a road test. Will the new clutch hold up to the power of the 670cc engine?.... tune in and check it out.
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Jimbo
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Robot Cantina
207 S. Sedgwick Ave
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[@ctre97]

To be honest, I'm kind of surprised you didn't just flip the header upside down and stick the muffler up in the air. Can't wait to see how it goes from there!

[@Name-vu1kn]

I had the same thought. It would make the engine bay temp cooler too.

[@eby6114]

I thought the same though the angles will be different, cut rotate interior pipe welds. Maybe he's trying to go incognito or keep the pipe as wide as possible

[@ccscomments757]

I thought of that as well, but if you look at the clearance the stock muffler has between the engine and the body, I question if the bends of the modified header would clear the body.

[@gabrielmarcos1069]

Its difficult to see how much space you have to work with, with the old exaust. I would try to cut out some of the exaustpipe away, on one side of the pipe just under where the 2 pipes are connected, then bend it away from the engine and reweld it. Just as you would cut away a piece of wood, when you try to take down a tree. Hope this make sence to you. I look foreward to the episode. Have a great day 😂

[@tobihaifisch7558]

3-inch chimney-exhaust pipe! 💨💨💨

[@bigphillAchtung]

i vote you shoulda done vertical stacks on the exhaust with tractor flaps!! ;)

[@user-nm7lj3wr3x]

This is such an underappreciated channel, great content every week!

[@eriklarson9137]

Underrated.

[@Eluderatnight]

Fill exhaust manifold with sand. Bolt flanges to a jig. Heat and bend as needed. Packing with sand keeps the pipe from crushing/deforming. and mitigates heat stress.

[@mattfarahsmillionmilelexus]

Ah yes, the ol' sand mandrel trick.

[@niftyjig]

I learned about that from Jericho

[@robertm2663]

I filled a copper pipe with salt before bending.

[@ionstorm66]

​@@robertm2663salts good for water pipes as it will desolve instead of plugging up things.

[@jttech44]

@@ionstorm66You can also use sugar for the same reason.

[@Stratotank3r]

Every sunday with a Robot Cantina vid is a good sunday. It is 2pm here in Germany, grabbed a mug of coffee and watch a the new stuff the clutch and the Renault have to offer.

[@ronwalsh]

Thanks for doing what you do over there. Semper Fi.

[@jojohnson215]

Let’s GOoooooooo!!! It’s finally that time!

[@bike6626]

I've been looking forward to this video all weekend. Nothing like some Robot Cantina to start my Sunday.

[@ArcticMayhem]

I used to be a Ski-Doo service tech in a former life. The new clutch is doing what it's supposed to. Ideally, it should allow the engine to rev to max rpm, and then shift to keep it there. The CVT is a fine balance between the fly weights, primary and secondary springs, and the primary and secondary ramps. Any time we would change the power output of the engine, we would have to adjust the clutch. Different weights, springs, ramps, so many different variables, and I can't remember off the top of my head what variables changed what, although it was usually a combination. For example, reducing clutch weights increases top RPM, but reduced clamping force, shortening belt life if it slips too much. The 94c is probably fine for your application, but it's tunability is limited. I believe Comet has a tuning manual that would help you get a little more out of the engine. Unfortunately, CVTs are notorious for power loss due to inefficiency. Something that is worth the loss in a 2 stroke to keep it in the narrow power band.

[@poptartmcjelly7054]

You could pie cut right at the Y joint in the collector and angle the exhaust pipe just enough to pass the cradle. Would have been a quick 15 minute job or just shy of 2 hours if you're me.

[@markzachmann2688]

To disassemble the clutch, hold the movable side of the clutch by hand, shaft between middle and ring finger, cover up, and then tap the center shaft like you did. That way you dont have to pry. Make sure you are only holding it an inch or so off the bench so when the fixed side drops it doesn't get damaged.

[@philipjohnson1103]

Jumbo, For acceleration you need to optimize for Hp not torque, which means you need to bring engine rpm up to near max. Hp = Torque x RPM. Clutch needs to be tuned to allow engine to achieve max rpm during acceleration. Love your channel! Phil

[@crissd8283]

Yep peak hp is where you need to run to get max acceleration. Unfortunately with this CVT, if you tune it like this then even when you are just cruising, the engine is spinning faster than ideal. It would be nice if the CVT governor ratio could be changed depending on driving conditions.

[@evan010101]

@@crissd8283exactly my thought. It needs to be hitting peak power, and will then be a bit revvy around town. A “manual” CVT is what Dutch DAF cars of the era used, in fact. IMO it would be “better” to use a fixed ratio chain or belt drive into the original clutch, with an engineered thrust bearing etc to allow it to work properly. But I get that Jimbo likes how the centrifugal clutch drives, and it’s his project :) One other comment, adding an alternator and belt drive sounds like a lot of work and power loss. Consider using a Lifepo4 battery instead, they produce a consistent 12.8 volt under load, and just recharge it once in a while.

[@timothybayliss6680]

It looks like he needs less weight or more spring. Having the transmission behind the cvt also plays havok with it. A higher gear, numerically lower, puts more pressure on the ramp of the driven clutch and will make the engine operate at a higher rpm. If you were cruising at 40mph in 3rd and shifted to 4th the engine would actually be spinning faster. There is more torque production from the engine and it will cause the clutch to downshift. Usually its not terribly noticeable but this car has 4 forward gears.

[@sidecarbod1441]

I disagree, for maximum acceleration you need maximum turning force at the wheels and that means holding the engine at max torque, With a manual gearbox you actually need to rev the engine to the point where you would apply more torque to the wheels by shifting up into a higher gear, at that point you change gear. A gearbox is basically a torque multiplying device. With a CVT then surely max torque must be getting applied to the wheels by holding the engine at max torque RPM. HP will determine the top speed of the car, that's all.

[@jamesglavich1426]

@@sidecarbod1441 You might want to think that one through a little more. Try that in a full size car, if the torque is say rated at 3,000 RPM and the hp is say 4,500 RPM. Now accelerate for a quarter mile, but keep the engine at max torque for the entire distance, while changing gears to reach max trap speed. I will bet that if you ran it through again but let the engine go into max hp RPM range, again through the gears in the transmission it will be quicker and a higher trap speed. If you have a torque converter then it will multiply the torque until it reaches it's designed stall speed.

[@gregholloway2656]

Great video, Jimbo. About the clutch, I’m thinking the RPM should be much higher, at 3600 or above, to achieve peak power, instead of peak torque, while accelerating. My experience is with snowmobile clutches, though. What’s up with the little alternator? Not charging sufficiently? 👍

[@GoldenCroc]

Yes it should. Peak engine power is where ou want to be, and that should be quite a bit above 2500 (or 1800?) with this engine, I should think.

[@sp90009]

That is correct, if the variator works properly, then flooring the engine should put the tachometer at the peak power. Which is probably around 4k rpm.

[@cad5359]

For peak acceleration, tune the clutch to where it starts accelerating at peak torque and then goes through the ratios at peak power. Peak power is the most torque over time after all! If you listen to a CVT powered car, it'll start off at 2500 or so after torque converter stall and hold the revs at 6000-6500RPM WOT.

[@darwinskeeper421]

Jimbo has my sympathy about the weather. I was driving Darwin back from Rochester NY, and I it started raining just before I hit Kansas City. Rain might be moderately annoying when driving a newish car but when dealing with a 40 something station wagon, or an even older Renault, things are far more interesting. Stay warm and dry if you can.

[@enwri]

Speaking of suspect handling older cars. You can account for blustery side winds by holding both hands at 12 o'clock on the steering wheel, and sitting forward off the backrest. As the wind knocks the the car out from under you, the inertia of your upper body, arms and hand placement on the wheel turns it into the wind, with a bit of feel, it happens almost automatically. Works for vw beetles and combis too. Tail heavy light front type cars. Plus, toe in or out can make a huge difference how things feel, even if other adjustments aren't possible. Have been watching the whole series, wondering if you'd get to stall speed and powerband tweaking.

[@PsRohrbaugh]

This sounds sketchy AF which means it's probably accurate

[@lightdark00]

Currently missing the gnomes Hopefully they're helping you on a another project.

[@KC-pf4tj]

I am so hooked on this video and project! Man’s ingenuity is just amazing. Keep up the great work.

[@eriklarson9137]

I have never welded. I can't even rebuild a lawn mower. But watch me give Jimbo suggestions.

[@timothyprice5240]

Back when these cars were new, some people chose to drive them with about 50lb in the trunk to improve weight distribution and therefore stability at speed. Apparently, by making the nose of the car sit lower, it also improved the aerodynamics. So l for one would love to see you try experimenting with weight in the trunk, in case it improved both handling and top speed. Absolutely love your channel.

[@noyopacific]

There is always something interesting going on in your head and shop. Thanks for the video!

[@stephengreen3566]

I look forward to every video you make. Thanks.

[@webmasale]

Sad you had to make so many compromises, I was excited to see how the new clutch performs.

[@everettstormy]

Ill suggest you send pipes off each side of the engine cradle then combine back under the engine or something

[@VirtualCryptid]

I was brought in on earlier projects..and honestly originally was not planning on watching this series... RC you do a great job! I love the animations and explanations...and even with a technical background you make things very enjoyable! Great job! Don't forget the intros!

[@brian6739]

Same with me. The harbor freight motors brought me in... I lost interest a bit with the diesel. That being said, RC does such a great job narrating and editing, I stayed! Glad to see cheap motors are back too!

[@eriklarson9137]

I was brought in earlier.

[@oddshot60]

Speaking about handling, Ralph Nader called. @17:59 he spotted 2 pictures of the broken rear camber limiting straps on the Reno. Ol' Ralph is thinking about writing another book, "Unsaferer At Any Speed". On a serious note, did you ever consider getting the front end aligned? Any toe-out AT ALL will make the handling of ANYTHING real spooky. And check those tie rod ends too.

[@htimmermans1938]

You worked hard! Thank you for the great episode again!

[@mdsuave13]

Jimbo, great work. The knowledge you are teaching people is great. You don't need to go fast to have fun.

[@johnwells5314]

I'm really digging that clutch. Those brackets really beefed up everything. That was really some nice work👍🏻👍🏻 you did and I think we all can appreciate it

[@geoffreyb3337]

Another satisfying video on a Sunday morning much-needed

[@Sokoldalu]

I like the approach of more equal length primaries on the header. A longer taper merge should help too if you can find one in that size.

[@ccscomments757]

Sunday is complete. A new episode of the quirky car mods of Jimbo.

[@hattyfarbuckle]

Pity the shocks have seen better days Jimbo - I reckon your enhanced engine sub-frame has reduced the flex in the aged chassis by at least 31.72% [metric] potentially leading to much better cornering

[@lynnhooley7608]

LOL

[@iamahood1]

Solid work. Thanks for providing what you can as you can. Always interesting!

[@nodrug2]

Thanks for aanother great video, with the old exhaust system it sounded like a stock model off the assembly line, very well mannered. Let's get the new exhaust on it and change the carb and see what this baby will do, ha ha. Until next week.

[@mortimersnerd4156]

LOVE THESE VIDEOS, Jimbo. They Make me smile & think back to simpler times. Thx.

[@paulhall170]

Each new episode delights, can't wait for the next!

[@replikvltyoutube3727]

Thanks for the video update on the project. Its sad to see exhaust not fitting. I wonder could it temporarily work if exhaust manifold was pointed upwards?

[@douglasmayherjr.5733]

Really Enjoy the Mechanical Journey. Thanks for the explanations. Appreciate your Videos.

[@paulbennell3313]

That it lost power on the original carb and exhaust muffler is only to be expected. However, that it can move at all must be considered as a minor miracle!

[@scrotiemcboogerballs1981]

Great video as always thanks for sharing can’t wait for more

[@user-bf6kl7vu7c]

Good fun! brings back my memory of tuning snowmobiles. For max accel get that engagement closer to peak torque, but it will be rough for regular driving. The secondary spring and ramp angle will control the "shifting" rpm, stiffer / steeper will raise the rpm.

[@CMFL77]

Always look forward to the next new Sunday episode! You've done some very cool projects and have very good mechanical / engineering instincts when going into uncharted territory. See ya next week :)

[@richardschaefer3889]

Always a fascinating watch.

[@coryernewein]

Those clutches are dialed in perfect so far, nice tension and deflection😎

[@Turbochargedtwelve]

Think that splash shield would keep rocks from splashing too if the car somehow were to do doughnuts again?

[@jasonz7788]

Jimbo you rock! Awesome job thank you sir

[@johncarter1150]

With the success you have had in this engine swap, I would like to see you go full resto-mod on brakes/suspension and transmission. Maybe eliminate the original transmission with a one or two rattio gear set. Thanks for the content of your project videos!

[@willemm]

Great to see the CVT in action. It makes it so much easier to understand how it works. It also makes me realize I never want a CVT in my car...

[@confuseatronica]

I hate em but on paper they're just fine. I have a sneaking feeling that I'd be happy with one if I didn't know it was a CVT, but they just feel weird compared to a traditional automatic. Or if they felt weird but were known to be dead reliable I think I could hold my nose and drive it.

[@nerd1000ify]

Some newer CVTs pretend to be traditional autos, they even fake gear changes when you accelerate. Which rather defeats the purpose in my opinion. Toyota kinda figured them out properly, by taking a page from Jimbo's book and combining a CVT with a gearbox. Their CVTs have a 2 speed auto behind them, so the car can start in low gear and not put so much strain on the belt.

[@Dwayne7834]

Good job . Thanks for the video. 👍

[@KarriKoivusalo]

That engine looks good, I wouldn't be surprised it it exceeded the original performance. It would look like a pretty nice ultralight aircraft engine too, if not for the hassle of adding thrust bearings.

[@UnfinishedProjectDartSport]

Sweet!!

[@fahb68]

Excelent video looking for the next one..... Thanks

[@markchapman2585]

Great video Jimbo 👍

[@coryernewein]

Good hoist for the Vtwin💪I've been known to ratchet strap them babies from my beefed up garage ceiling joists🤦🤣😂

[@chriswinter2400]

I absolutely love your videos and I'm sure others do too even though it's just a silly project thank you for sharing

[@markrenfrow9873]

Nice work Jimbo.

[@3rdpig]

Good to see it running again, if only for a day!

[@pepethefrog7193]

Glad you fixed that belt slip issue. I bet the revving up and then bogging down during acceleration runs is now gone. The error ist to set rpm to max torque. This is WAY slower than setting rpm to max power at 3600rpm. Remember a CVT does convert HP into torque, let the CVT do its job!

[@jaredsimcox2248]

Thanks for another great video I find myself looking forward to your next one every week my 2cents on the clutch is the engagement speed is good but tune the full throttle rpm for 3500-4000 i learned in my go cart racing days it’s risky to go past 4000 on stock valve springs

[@Dis-Emboweled]

The car is running pretty good! "Don't worry! We'll bring back the excitement soon enough!" 😂

[@truthboomertruthbomber5125]

Maybe you can mod the stock muffler for more flow. Remove the down pipe and shine a light into the opening to see if there is a baffle that you can drill some hole(s) in.

[@petertimp5416]

All good, thanks.

[@tnnaroot]

Thanks for all information you give

[@skozer22]

Thanks for another great video

[@crazyoilfieldmechanic3195]

Cut the shorter header pipe 2 inches from the mounting flange. Cut the 90° going down on the longer pipe completely out. Put the shorter piece back up against where it was cut and clock it so the collector is away from the engine plate and all. Then pie cut the 90° you cut out until it fits back where it was. No extra tube needed.

[@3kids2cats1dog]

Great baseline!

[@deltacx1059]

7:12 that is more of a skill issue, rear engine cars are something that needs a bit of practice to get good with. but a solution is to add weight to the front. If you can get the weight distribution close to 50)50 then it should be very easy to control. Interesting video though.

[@thatonedude5237]

Too bad we don't have a dyno. Would be cool to have an episode or episodes delving into a little RnD. Playing with intake and exhaust runner length after installing the dual carbs to see what kind of torque and power curves you can make. You could test different combinations before and after a cam and possibly advancing ignition timing. Adjusting those carbs for every configuration would be such a pain. So many possibilities for content though.

[@BillyBob-uc9zp]

Well done Mr 😎

[@littlebearish]

It sucks the stock exhaust robs so much power cause I think it sounds a lot better this way. Glad to see the new clutch doing so well. Definitely seems to accelerate off the line a lot smoother.

[@michaelblacktree]

The license plate made me chuckle. 😎

[@justinr9753]

If you look up the MSDS if you want to see if that dry lubricant is the same as anything else. That's how i used to check GM brand fluids.

[@that_jamesguy]

You need to be accelerating at peak horsepower RPM, not peak torque RPM. So 3600 instead of 2500. You will notice a big improvement.

[@nathanalsum]

Love the videos. keep em comin.

[@54mgtf22]

Hey Jimbo. Love your work 👍

[@TheDistur]

Getting ready for some real power!

[@TheGTstang]

Love this channel….niche and very interesting

[@nobbybrown8056]

For pure acceleration testing I would try the blue spring, to get the engine close to peak power sooner, I'd love to see the results!

[@lancegouvan1653]

Awesome nice work ...

[@caldaq219]

One thing to perhaps think about is doing a vw type exhaust heater for the cabin aera.

[@SamwiseOutdoors]

Man, this project really has been three steps forward and two steps back, but I love it. These are the kinds of real-world problems that us hobbyists have to deal with when we don't have a big-huge Motortrend budget to use to throw billet parts at a problem.

[@Alleroc]

Honestly, that's what I love about the series. Too many youtube "hobbyists" are like, "Oh, I don't have this part. Let me turn on my Tormach CNC and use about $200k worth of tools, shout out to XYZ Tool company for sponsoring this" and it just makes it unrelatable. Where as with Jimbo, when there's a delay, I feel it the struggle cuz it's what happens to me all the time too!

[@DracoOmnia]

Even on vacation in Cabo I can't help but have my Sunday morning routine, cup Joe and robot cantina

[@Clearanceman2]

LOL this morning I was hoping there would be a video today.

[@samizdat113]

Two steps forward, one step back.

[@alexjoyce1276]

I love spring rates!!!!!

[@mastercricket7626]

Man , me sooo eager to see what it do wit the new clutch and full power ... I am genuinely curious as to what the different start and finish ratios are gonna do for it when it has proper flowing exhaust back and then the twin carb test be cool af to but deff more pain to dial in, but a engine is a air pump so more air it can flow more powaah it can put down lol .. peace and love jimbo keep it rad stay safe and build on ... l8z

[@white_mage]

idea for a new exhaust there's this suction effect i saw on an old race car, i believe it was a matra. basically the engine was air cooled and the fan wasn't big enough to cool the engine, so the engineers replace the panels aroud the engine for an air duct with scoops on the front so the oncoming air would cool the engine. they cut a hole at the end of the duct for the air to escape but also left the exhaust pipes inside the duct with the ends close to the exit hole. this generated a suction effect on the exhaust dramatically improving scavenging, gaining a lot more power while keeping the engine so cool it didn't need the engine driven fan anymore. cut a small scoop on the side of the engine bay and put the exhaust inside the scoop to see what happens. maybe that'll gain some power like that time you tried the ram air intake.

[@elitecpudoc329]

Jimbo out there with another banger video.

[@pipeliner731]

Well my Sunday is now complete!!!

[@HeyImGaminOverHere]

Next mod should be 2x V Twin predator engines hooked together to make a 4 cylinder lawnmower engine!

[@jfan4reva]

You should drive it to Nebraska. We've had so little rain I haven't had to carry my umbrella in my backpack for a couple of months.

[@ramentaryramblings]

I wonder if Jimbo would have better time to do things if he took 2 weeks to do a video, especially during the rainy season and winter so we can get more content and more than just an update video once every 2 weeks since stuff takes so long to ship. I think the time to video ratio would be nice

[@twocvbloke]

I guess when something's made right, it doesn't break right from the get go, or even arrive broken from the factory, as per the "affordable options" that flood online purchase websites... :P

[@dragonbutt]

Also i wonder how hard it would be to get sponsored by briggs and get your hands on one of the 40hp vanguard motors.

[@mathuetax]

Next episode; We install a DAF Variomatic transmission ;-)

[@dongordon2754]

Thanks Jimbo!

[@Zupoyo]

Can't wait for the next video 😁

[@SmogFighter]

I have a different suggestion for the exhaust. Try cutting the downpipe side flange about an inch or two from the engine flange. Then cut the crossover pipe in the radius of the bend to allow for rotation of the header to clear the frame. Does that make sense?

[@virtualizeeverything]

best stuff on youtube

[@MOOGSTINE]

Love the videos