I agree with trying the larger single carb before trying dual carbs. Now's the time to do it and it might be the best overall solution, who knows? Unless someone previously tried all this.
I enjoy the steady progression and agree with you. Let's stick with the single but larger carb before going full hot rod dual carb. If you don't eat your meat, you can't have any pudding!
Cars and cameras has a hopped up 670 on theyre drag rail. They have used dual carbs but it did require modifications to the cooling shroud. Id suggest 2 24mm mikuni carbs.
Single carb first. I’m enjoying this series way more than I thought I would. I could feel each “shift” on the 1-2-3 run. Ah, nostalgia. If I knew then, what I know now, I would’ve kept Oma’s car. 😢
I really enjoyed the 3rd person town driving shots like the one that shows the car from the side, coming to a stop and accelerating at the intersection. Nice addition!
My vote’s for single big carb next! If I’m not mistaken , you mentioned CVT/transmission upgrades earlier in the video. Now that’s interesting. Getting the power (what little you do have!) down effectively makes the most sense to me, but who am I anyways. Keep up the good work Jimbo!
Agreed on the transmission upgrades. He's losing over a second with every shift, and starting in third gear is both hard on the trans, and slowing it down significantly by default (when you take the slow shifting out of the equation). The trans is gonna have to be addressed at some point or it's always going to be the biggest hurdle.
I agree !! It’s been proven that the single carb system doesn’t distribute fuel equally to both cylinders on these 670. Plus I think that’s why you’re getting your lean rich reading
Those foam filters actually work vs the K&N style which let anything smaller than a bird into the engine. Project Farm has an air filter test that I found quite eye opening.
I'd do the single carb first, then the dual carbs with those red beer koozie foam filters. Prob won't be quite as beautiful as my old '68 firebird 400 tri-power setup, but its mpg will be far better!😊 This is a great series! Gotta get sime more white cheddar popcirn for next wee!
Single carb, then dual. Maintain the process. I keep watching the 0-30 numbers for a realistic city application. Thanks for one of the best Sunday morning shows on YT.
I definitely think you should start with the 36mm carb before going to the dual carb setup, just for the sake of comparisons. The printed spacer really helped in straitening the air flow to the ports on the manifold, thus adding some performance gains. The dual carb setup would probably be ideal for power, but would take time to tuning them properly. It's cool to see how far you've come with this. I'm anxiously waiting for next week. Nice work Jimbo!! 💪🔥
My suggestion is to go with the larger single carb first. You already have it, so why not (Yes, I'm trying to keep with the theme of the channel!) After that, try the dual carb. I think you're going to find, once they are dialed in, the twin carb setup will really help with performance. The reason being is, when the air comes through the single carb, it has to change direction four times by the time it gets into the cylinder (90° at the aluminum manifold; 90° just after the 3d printed manifold; 90° turning to head for the cylinders; 90° turning through the head and into the cylinder). When you have the dual carbs, you're eliminating three of those turns. If the engine is intake restricted, this is going to help big time (but you already knew that).
Finish the single carb tests since you have it mostly dialed in Jim. Once done, then work with the duals. As tempting as it is, I have the feeling that you're on the right track with Venturi.
I kind of like this set up. It seems to have "continuously variable" as its theme. The CVT on the engine and the continuously variable venturi in the carb. I guess if you move on to a new car, finding something that has a CVT may be interesting. Then you could have CVT to CVT power delivery with CV venturi. :D Continuously variable all the way down. LOL
Holy cow! Knocking a full second off the 0 to 55 time is awesome. Time for some more safety equipment... like a neck brace. I can only imagine the strain.
Another fun Sunday morning, always look forward to the videos and this one made the mark. I want to see the mule marbs but the path through the larger single is the most logical and informative so I go with that.. So there's my vote. Whatever happens will be a blast. We'll see next time.
Wow! I stumbled across this channel by accident and wasn't really that interested until the Renault adventure. Now I am hooked! Try the larger single carb first and let's see how we do. I would also like to see the dual carbs later on. Anyway, you captured another person in your audience! Watching to see what happens next. . . . 😊
Great show Jimbo! The single carb with the tunnel ram was really good & simpler that 2 carbs! Too bad the low speed jet was not responsive. Love your experimental spirit. Blessings, Paul from S. Central Tx.
Fantastic video! That was more exciting for me than I thought it would be. I was very curious to see if the improved airflow of the fillets would help. I designed it when you used the original carb so I thought the added length and fillet would help mixing and flow, but it seem to fit great with this carb as well.
Great work Grumpy RC! You should publish a design/build video about the production, I love a good cross channel tie in. Curious to know what filament you used? ASA or ABS I would assume.
As a driver who's well-familiar with driving stick, I can tell you: You need to work on your technique. Try not lifting so much off the throttle when you shift, and get your shift/throttle efforts synced better so that you're shifting just before you're "lifting". That way, the engine will stay more in the "sweet spot" RPM band, so you won't lose as much power under acceleration.
I have driven manual transmission cars all my life, it's my preferred transmission. Keep in mind there is no conventional clutch on this setup. So when I shift I'm shifting without a clutch. I have driven many cars like this, but on this Renault gearbox the synchronizes are a bit worn.
There is a group of 3 people who build performance engines call carsandcameras and they have been able to make a single carburetor work with a modified intake manifold. The biggest setback of the single carb is that they noticed one side of the engine getting more fuel than the other and it would foul out the spark plugs. I would say a good test of single vs dual carbs would be to make variable intake runners (if we have the tools to do so) that way the air to fuel ratio is even between both cylinders. It would be awesome to see your way of do this and testing results since you are the diy person who shows anyone can do this without intensive knowledge and tools. Truly a trial and error, and I admire that.
Absolutely try the bigger Carb Jimbo. We’re all loving this. Very much appreciated that you don’t get a sentence like this anywhere else on the internet too 😂
1) Single 36mm carb 2) Dual carb 3) Since you've already added the O2 sensors, single EFI throttle body 4) Dual-throttle-body EFI! Seems like a natural progression to me! :D Love the series.
Single carb is way less hassle to dial in than dual carbs. I want to see both, but I think trying the single carb first just makes more sense. More of a linear progression. I have been enjoying all of your videos since I happened upon your channel a couple months ago. Thanks for entertaining us!
The 36mm carb first. The 32mm is big enough for a 420cc up to about 5000 RPM or so(for ideal top end flow), and 33-34 mm is what’s recommended for most 420cc class performance engines. I would imagine that the 32mm is holding your motor back a little bit on the top end. Would be nice to see the 36 mm next, so that we could have a back to back comparison of a smaller carb to a much larger carb, and then we can do the twin carbs. Keep it up Jimbo, the content you make truly cannot be found anywhere else on RU-vid or probably on the Internet for that matter. Thanks for all your time and hard work.
I’m always looking forward to seeing your new videos. I’m sitting on my front porch drinking coffee and watching the morning happen while watching this.
re the low-mid throttle: these things have an idle mixture screw and an idle jet. The idle jet effects the range you were talking about. the screw just does idle and effects what happens when you snap the throttle open or closed. Also you can get down draft (or semi-down draft) motorcycle carbs. typical found on Japanese v-twins. these might suit your setup more.
I want to see both options. I guess if I had to vote it would be "Moor Carbs" at least one moor. I think the less than ideal standards of the knockoff will be a pain to get fine tuned and those DUAL CARBs are worth tinkering with. Either way it makes my day to watch the build.
If you could figure out a way to manually control the CVT to keep the engine at its torque peak throughout the run, it would undoubtedly give you better acceleration times...maybe a cable attached to the output side to overrride the spring in the CVT (just go by the engine sound and feed it in as the RPM climbs)
I like all of your projects but this one is the coolest IMHO. You could actually use this little car for a runabout going back and forth to town. I dig it😎😎😎👍👍👍
Those OKO carbs are a Keihin knockoff, specifically of the Keihin PWK series of carburetors. Used many of them when I was building mopeds as a late teenager, and as long as you use genuine Keihin jets and atomizers they will be just as nicely tunable as the genuine PWK carbs although a four-stroke engine will generally still run just fine with some mixture deviation from suboptimal fuel atomization, as you've already demonstrated in prior videos.
My Sunday is now complete. Get up and watch Robot Cantina. I'm anxious to see the results of the dual carbs, but I think it will all be incomplete if you didn't try the larger single carb first.
Great project! Those CV transmissions are amazing. A higher ratio in the differential might make better use of your four speed, but probably not worth the effort? When I was driving a 1000cc 3-cylinder geo metro, I got noticeable improvement in mileage and performance when I over inflated the tires. They wore faster, but only cost $25 each at the time, so it was worth it. Caveat emptor!
Put an RPM governor on the engine and make the CVT adjustable via a foot pedal. So you set the governor to peak performance and adjust the RPM to accelerate without dropping the RPM too much. :)
SInce you are set up for a single carb right now, try the 36, although I think it will be too big. At least you will know at that point and can try the duels. Then you wont have to worry about going backwards with the setup to try the 36mm later.
V-twin manufacturers often use twin-barrel carbs to isolate the intake pulses from each other. The reason for this is because the firing order is uneven, meaning one fires then the other does quickly after (normally 0-270-720) This creates a discrepancy in intake charge between each cylinder and possibly mixture, because the second intake pulse is right on the back of the first. Making the throttles separate effectively turns one carb into two, but uses a single float, fuel inlet and throttle linkage.
IF YOU GO DUAL CARB... TRY and shorten the intake tubes (EQUALLY) AS MUCH AS POSSIBLE, it WILL help with the intake of the fuel and air, ALSO, INSULATE the aluminium intake tubes (wrap them with something that will keep them isolated from midday sun & engine heat), as they COULDget hot, and affect the intake too. Note: This is why you'll see on motorbikes (especially aircooled) that each carb is only mounted on rubber intakes and close to the engine... 🤔😏 😎🇬🇧
Definitely do the single carb first, but it's unlikely you will see a big gain from it. I think a cam and valvesprings would really be the key to improving your performance to 50 mph.
Been a while since I commented, but I still haven't missed any shows! LOVE seeing the results you get with these experiments! Between you and Garage54, yall surely satisfy my curiosities with vehicles and experiments lol. Keep up the awesome work! 😎✌
HEY JIMBO. That car seems so loud. What I would like to see in a future episode is you obtaining a quiet car resonator and a quiet muffler. Then maybe fabricate and run the exhaust halfway towards the front with a resonator inline then curve it back towards the back and have a muffler inline with a pipe going out the back. Then maybe measure the before and after backpressure, exhaust temp, and engine performance like 0-55 and mpg, comparing before and after. Also a measurement of decibel output before and after. Hope I gave you a great idea!
Dual carb here. Once tuned it will not only run better but be more responsive and idle smoother because you eliminate the charge robbing effect the leading cylinder tends to do to the trailing with a shared plenum induction.
You sir are at the for front of a revolution,as the government pushes electric cars more and more people will do this as a option to keep vehicles going
My dad bought a 1960 Plymouth Fury convertible Indy pace car replica in 1961 when I was 8 that had the 354 hemi with dual 4 bbl. carbs and a Tunnel Ram" manifold that mechanic's used to call Plummers nightmare. My point is, these long manifolds placed the carbs right against the opposite wheel wells and had maybe a 30 inch run, supposedly for mid range touque, but who knows? I know that when in tune, whic only lasted about 2 weeks, it would pass anything on the road but a gas station! 7 to 9 mpg! Maybe you could experiment with a much longer intake manifold, maybe several inches? Maybe this would even out the a/f ratio between cylinders? Ask someone above my pay grade, I was merely a semi truck driver, not a real engineer, because I flunked calculus 3 times in college and called it quits!
I’m really enjoying this series and I think trying the larger, single carb may get some good results, but I’m thinking you have pretty much reached the upper limit of what this little engine can do.
larger single first. The "tunnel ram" has shown an improvement, need to see what effect an increase in airflow will have on performance prior to changing runner length (the twin carb setup will have shorter runners) as well as carb size. I have no doubt that the dual carb setup will make more power at the top of the RPM band, but I think testing the "best case scenario" (larger carb with tunnel ram spacer) single vs dual will make for an interesting test- I don't own a 670cc V-twin Renault to go find out myself, so I'm counting on you, Jimbo.
From memory, every 8mm 5/16" increase in intake length drops peek power 300rpm. For single carb you have to look at piston demand timing of multi cyls, ie, overlapping demand. Everything outside piston demand, ie, intake stroke from TDC to BDC, is wave-tuning, and that doesn't really rely on carb flow, Basically it's just a matter of checking if both cyls want air at the same time.
Definitely want to see dual carbs,but lets progress with single carb 1st. I have a 420cc in my 1996 ford aspire a am very interested in your results of course for my benefit so i cant skip some of the trial and error. Great info and entertainment.
Think belt temperature should be monitored. A more tuneable CVT would be more helpful. It should engage closer to where the engine is most efficient and run the entire time at the most efficient RPM. Think most of it comes down to not having large enough diameter CVT. If it is just about motor power improvement, make an engine dyno and do bench tests. It would help in determining what RPM to set CVT to run at.
Hi, I'm one of your UK based viewers - I'd like to see the 36mm single first but with a view to moving to the dule carb setup once we have data on the 36...... I love your work hear on RU-vid & you have inspired many an idea...... keep up the good work! Kind regards David
Can you and/or do you know how to float gears All it takes is to let off the throttle shift and put your foot back down in it I have been floating gears for years while driving trucks for a living, having the CVT should act like the clutch, preventing you from needing to use a clutch while in motion It would be interesting to see if it is possible and the results of it Thank you very much for putting these very entertaining videos on. Enjoy watching. Thanks again.
I have driven this car hundreds of miles and I'm very familiar with the limits of how fast the transmission will shift. Keep in mind this car is old and the synchro's are not in the best condition.
You could use a single wideband controller, and two o2 sensors. As long as they both had a heating circuit you could switch between the two signal sources on the fly for each bank. One would THINK. Correct me if I'm wrong.
Back in high school my brother and I paid $150 each for a 67 R10. It had a fresh rebuilt engine in the trunk. I could drive it at 10/10th around the Kmart parking lot without anyone bothering us. Except for the body roll it looked like we were looking for an open spot! LOL!!!
When the motor blew up (10/10th may have had something to do with it) we changed engines with the help of a buddy. After we dropped the engine by hand two of us lifted the rear while my brother pulled the engine out from under. Install was the reverse procedure. I miss that car. I went on to own a plethora of VW Type 1s after that.
My Vote is go big then dual. Soon you will be modifying the engine insides and valves for more power. Old Red Beard has it figured out lol. Have a super blessed week.
You have to try the larger single carb first to gather the data. Otherwise you'd never know if just a big single carb is comparable to the complication of a twin carb setup, although the twin carbs would look very cool 😊 So much more fun to be had!
I agree with alot of the people here. Try the bigger single carb before going duallie. You might gain some valuable information going forward in potential future uses in using the big carb
I've had one with a signle cylinder, that reved out past 7000 rpms with little to no valve float. Even ran it with the stock cast blover, didn't turn into a bomb somehow.
In my experience those belts will last much longer if you can encourage some air flow over the pulleys, I have a 11hp Kohler engine and a comet 40 series on a biggish knobby tire go-cart, and it gets thrashed in dirt, burnouts and full throttle pulls would eat a belt in about four hours, and I noticed the steel pulleys would be blistering hot, so I built a duct to funnel the air exiting from the engines fan over both pulleys and now the same belts will last a whole day at least.
Turbo time !!! Harley and most other manufacturers have been using a single carb on their v twins for msny decades, and they work well and are simple..
I'm always doing dumb shit experimenting with things that don't belong together but actually work surprisingly well.....I wish I had the foresight to record the Frankenstein monsters I've created because people seem to like it and I'm definitely One of them why drawn to your channel
