S3 E28. Performance tuning and MPG tuning the 670cc predator powered Renault 

This IS the only channel on RU-vid with this kind of content.

Robot Cantina: I hate doing fuel economy tests! Proceeds to do 5 fuel economy tests in one video.

You know, its current acceleration makes it a perfectly acceptable "around town" driver that would beat the pants off most cars for gas mileage. I really like this little car. :)

The saturn turbo diesel is the most incredible car ever ! ❤

I'm very jealous that you can spent your time working on these projects. Thanks for documenting the fun and sharing with us!

The ram air failed because you did not adjust the mixture to compensate. Gotta richen that mixture. But I agree to get the carb you’re going to use first. Once you pick a carb, the ram air can be a focus. Good job. Fun stuff.

Thanks for the recap of the progress so far. It's hard to believe you've been able to make such an improvement with relatively little modification. I totally understand wanting to tune the engine performance before tuning the transmission. The engine develops the power according to the load, while the transmission converts it to the appropriate torque for the current speed. The tuning of the transmission will greatly depend on the power curve of the engine, whereas getting power out of the engine is its own thing. And whatever you do, you don't want to change a bunch of things at once, otherwise you won't know what change made the difference.

I drive an Excursion, and after seeing all the fun with this car it makes me want to consider something tiny to tinker on.

The pressure from the ram air system also needs to connect to the vent of the float bowl. The jets work on the pressure difference.

If you are interested in what fuel costs in Germany. Conversion rate is $1.09 for 1€ Today here in Bavaria/Germany: Gas= 7,82$ Diesel= 7,08$ for 1Gallon I think twice about taking out my Corvette😊 . Thanks for the conversions to the metric system. Great Video👌👍.

I’m happy you’re going with a variable Venturi carb. My British cars have SU carburetters which are variable Venturi.

That last 55 mph test was great! The car sounded like it stayed in the power band and kept pulling! I am enjoying this project! Very impressive gains!

Loving every bit of this series. And I 'm sure the Saturn will get a decent farewell.

So I love the straight edge across with fuel cell with the combi square for measuring the fuel level, but to increase the accuracy how about a little gnome in a boat acting as a float holding up a stick, fill the fuel cell up until the end of the stick reaches the same point on the combi square every time

Dude, I love the fuel consumption figures. Please don't stop doing those! I want to do an in line hybrid of sorts and that helps me out a lot!

Thanks Jimbo, I always enjoy checking in on the Cantina!

Note to OP: Re: Cowl Induction. It's well-used in NASCAR as a way to create a "Ram-Air" effect with inlet air to the engine.😉

Tune in next time when Jimbo powers a M1 Abrams tank with a 3.5cc 4 stroke Toyan engine! Joking aside, I love this channel and the thorough testing- it never ceases to amaze me with what you can get away with yet still be drivable.

With the "Ram-Air" system a friend built on my '85 S-10 pickup, it drew from the "clean" air seen by the lower front-end air dam. Also: The GM/Bosch TBI system (EFI) was able to compensate for the change in inlet air mass & temperature by constantly monitoring and adjusting the A/F-ratio in accordance to input from the numerous inputs it employed, as well as referencing the programmed fuel mapping "burned" into its PROM (Programmable Read-Only Memory) chip. The result: Avg. 25-mpg@77-mph cruising speed!😁

This is probably my favorite channel on RU-vid. I stumbled upon it at the beginning of the Saturn build. I look forward to every video! Keep up the good work!

I usually finish my Saturday evening watching some carnage in an I Do Cars engine teardown, and then enjoy my morning coffee on Sunday catching up with what Jimbo and the crew have done with lawnmower powered classic French tourers. It's a nice contrast of things that don't work, and things that do even if they shouldn't. Love it! Heat this week is no joke, stay frosty, gentlemen!

An old trick I've seen done to help with the fuel's phase change is to heat the fuel before it enters the carburetor, done "quick & cheap" by running the fuel through a length of copper tubing wrapped around a "waste" heat source (heater hose or an under-hood exhaust part) placed in a point along the fuel line's delivery path AFTER the fuel pump or fuel filter.

As always, this was a amazing and enjoyable video. I love the concept of slapping together a car and getting the most out of it. Makes me want to do it sometime.

I like the "dare to be different" approach to the carburetor selection. And I hope the Saturn gets another motor. Try to find something really weird that nobody has heard of ever to put in it.

The reason VW probably found the exhaust thingy to improve power is because you don't want your fuel to vaporize before getting into the combustion chamber; if possible while still getting good atomisation. It's one of the reasons direct injection is better for fuel efficiency and why it lends itself well to higher compression engines. Latent heat of vaporization is a pretty powerful thing when it comes down to engine performance and even though petrol/gasoline is almost laughably weak at pulling heat from the air around it to do so, it still makes a massive difference for engines. It's also why you can make more power on E85 even though the specific energy of E85 is far lower than petrol/gasoline, the simple fact that ethanol pulls much more heat out of the air to vaporize cools down the combustion chamber enough to provide an actual performance benefit over petrol/gasoline, even though absolutely everything else about E85 should make your car less powerful. Also ram air intakes need to be very carefully designed to get a decent amount of more air forced into the intake. On modern cars it's easier (and less aerodynamically problematic) to use intake manifold resonaces to achieve a similar amount of extra manifold pressure. Even then you'll be looking at maybe 15% more air which is speed dependent and a nuisance to manage on a car without some sort of system to monitor and adjust the AFR constantly, like say, an EFI system. You could also go the old plane route and add a lever or dial in the interior to let you adjust AFR on the fly, which could make it work. Probably doable somehow with some cables and whatnot going through the firewall and looking like a tripwire inside the car lol. The carb spacer is also a bad idea on principle alone. You want as short of a distance between the throttle and intake valve as possible to reduce the distance of vacuum between the two to reduce pumping losses. It's why things like ITB's exist. They won't make any more power than a good intake plenum, usually, but they improve throttle response for that reason. There's a reason BMW dumped a whole lot of money and time into developing valvetronic. Having the intake valves be the throttle bodies themselves does a whole lot for throttle response.

I used to drive a Renault R10 back when I was in High School (1974-75). I loved the front seats in it and it also got great gas mileage back then. When I came to driving it in the snow it was much better than than rear wheel drive cars of the time. It also had Michelin X radial tires on it. Radial tires were unheard of back then. My dad later replaced the back tires with a set of bias-ply tires. This made the car extremely unstable to drive as the rear of the car wanted to fishtail on every curve. It would be neat if you could find a person who still owned an original R10 and have a race between yours and the original car with the 4-cylinder engine. Thanks for posting these interesting videos.

Thanks for producing such interesting content. I look forward to Sundays so I can watch your latest efforts. Phil

We need more episodes of this, I know it's difficult. But really.. We need more Great job as always and keep it up

Well done to Performance 670, it made your life much easier. That said, $3.50 a gallon is only about $1 per litre, you get no sympathy from me :-) It's great to see this quirky French car back on the road.

The air-cooled Volkwagens are known for using CV-style carburetors as well... hence why they typically got such good feul economy from the factory. And at one point, they decided to go with a variant of Bosch's Jetronic EFI system. (Every multi-point EFI on the road pretty-much is...!😉) It worked well... until they discovered American CB-radios were able to generate a strong signal on the same operating frequency as the un-shielded ECM that it employed, resulting in many frustrated VW owners on the roadside wondering "Why the F@$# did it suddenly shut-down!?!"😆

Thanks for the sunday moneing entertainment jimbo! Coffee and robot cantina is my favorite way to start the day

Cool, i hadn't seen one of those constant velocity something carbs before, but it immediately reminded me of the legendary 'constant depression' SU carb. Cheers Jimbo!

The carb on my parent's early 80's Ford LTD Station Wagon was a variable venturi carb, too. From what I remember, my father said it worked really well really liked it. His only complaint was at the time, it wasn't rebuildable. So, when it was time for a rebuild, he ended up having to replace it instead. Really neat design: Good power, good fuel economy, and minimal maintenance.

about jumped out of my chair w/ excitement when you mentioned you would be giving us at least one last video with the saturn. that little thing is one of the coolest cars on youtube IMO

i must say I appreciate the amount of effort you put in. and also the metric conversions, they help me out alot!😊

I love this guy. I think everyone who works on engines should watch this as its valuable information.

This channel is excellent and unique. You present the content so well. Can't wait to see what you do next my man.

$3.5 dollar a gallon is a great deal. Here in the Netherlands we pay €2 euro a liter....😮

The basic rule of thumb when experimenting is to concentrate on one thing at a time, otherwise it's easy to get lost. You are talented and it's fun to follow the channel. Thank you

Driving around on a 100 degree day in my girlfriends Austin America the engine suddenly died. I got out and opened the hood to find that the carb(constant velocity) was a large block of ice. I chipped some away and as soon as it was mostly thawed I discovered that the heater band that was wrapped around the top had the wire broken off. I thought it only worked to warm it up during cold weather. Apparently that particular carb was very efficient at vaporizing the fuel. No wonder it got a solid 35mpg all of the time. Hooked the wire back and away we went !

09:38 - For the 'Ram Air' to work more effectively, you'd have to install some form of fuel injection system setup, driven by a seperate 'Stand alone' ECU with various sensors to monitor and adjust fueling to suit the increasing air flow the faster you drove. It CAN be done, but, it's not cheap as, well, you'd have to buy the gear, install it, and then book the car in for a coupla runs on a Dyno to tune it correctly & effectivly... So... Sadly a little too much for this kind of project. Though yeah, it would be intriguing how that route would go with regards to power & economy. 🤔 😎🇬🇧

I drive an air cooled VW and I swear I don't think my carburetor is any bigger that the ones you've been using. So now you got me thinking...

In my experience with tuning cars, fuel ratio is only half of the equation. The perfect (stoichiometric) ratio is 14.7:1 at this ratio you get the most efficient burn. The other half of it is ignition timing you want the timing to be advanced to the point the motor creates the most power as possible then take a degree or so out for safety. The more power the motor makes the less throttle and fuel you need to supply to get the same results. Don’t know if you’ll read this or not but hope it gets to you and possibly help :) awesome project

the tinyest tires are 125/80R15 who are use on Citroën 2cv...But the best quality (Michelin) tires this size are very expansive (91€ for ONE tire in France).Carb pipes heater are relative similar to the VW on the 2cv flat twin air cooled engine...

This content strokes the best part of my ADD brain. Ive been watching for a long time and always look forward to your posts every week.

This is the most interesting experimental engineering channel out there imo. It’s crap like this, that I want to work with daily.

I just love that old car. You still find some of them in Denmark.

God i love your content. Never thought id be so ecstatic to see a french car with a harbor frieght motor shave 2 seconds on a 0-55 run. Youre doing great and im glad i subscribed

Can't wait for that carburator upgrade, your dedication to the science is admirable. It's always easier on paper.

For you who cares😅 - I was the owner of an BMW 530d A (e39) it had a 3.0 turbo diesel and ran 5.7ltr/ 100km at around 100km/h (60 miles) the car weight was 1880kg and had a topspeed 247kmh and 0-100 at around 6,7sek. I kept that engine for a boat but sold it cheap before knowing this channel.

Garage 54 did a test when they did heat up the fuel to its boiling point and did get almost 2/3 the mileage as with the ambient temp fuel. Sure, the test subject was fuel injected. Our old moskvitch 412 had also problems when it was below freezing. It also had a pipe connected from the exhaust manifold to the air filter. On summer, many drivers(my Dad also) disconnected the pipe to get better performance and mileage. But in autumn, if you forgot to connect the pipe back, then you where sitting beside the road waiting to the carb to heatsoak a bit and drive forward few km/miles if you did nod had the pipe with you.

Man i really like all your vids, they're very technical and illustrative, thanks for taking the time to do what most of us wanted to but can't, appreciate it budd

07:12 - Hahaha yeah, I suffered 'Carb Icing' once. Many years a go I had a 1991 VW Polo Classic 1.3 Litre (2 door saloon). I had removed the large circular metal air filter & housing (the design that had a 'Summer/Winter' flap that would allow heat to be directed up through to the air filter housing for warm air to stop the carb feezing in winter), and had installed a home made sponge air filter... ALL WAS FINE in the summer months (could hear the induction roar sound nicely too 😏😉), but, one time during a cold November night driving home from a girlfirends place, the car suddenly coughed and died miles from home. I though "FAAAAK! How am I gonna get home!?" Anyhew, checked under the bonnet, nothing seemed out of place, tried starting the car again and, hey presto! She started! And so, gingerly drove her home expecting a total breakdown... Well, this happened a few times, and after some research I was starting to get a few ideas (fueling? Blockage? Carb Icing?) until one night, torch and screwdriver at hand, I was ready for it. Yup, she died, so I quickly pulled over, popped the bonnet (hood - for you guys lol), unscrewed my DIY air filter, and yup! There it was... FROZEN FUEL in the top of the carb! Hahaha. Being a biker too I felt such a dope as I SHOULD have recognised this from the start! hahaha. So, I swapped back to the original filter & housing for winter, then back to the DIY foam one for Summer. Ohhh what a numpty eh? Hahaha 😉 Sadly, I miss that car 😟, it's one of a few that I SHOULD have kept... 😎🇬🇧

The discussion about warm air intake reminds me of the "thermac"/thermal air cleaner/exhaust manifold heat shroud on a ton of GM cars from the late 60s and 70s. There was a vacuum modulating thermostat and a vacuum operated solenoid connected to a door on the air cleaner. The air cleaner had a normal under hood or front grille intake, and *also* an intake that connected to a flexible hose and shroud around the exhaust manifold. You can find some excellent 1960s service training videos from Chevy that explain this system in detail - it would blend the air intakes to target a 125°F intake temperature in all conditions. If I remember from the original EPA documents, this system reduced cold start carbon monoxide by *ninety* percent! That's a huge improvement on top of driveability and efficiency improvements.

Intro music!!! I miss the Season 1 intro music. It was short, not too serious, and delivered good vibes.

"Nested" intake and exhaust manifolds on inline engines was common from the early 1900's untill fuel injection and multi valve crossflow heads became more mainstream.

When I built my first 4-stroke motorized bike I added an aftermarket "free flow" air filter because it looked cool. It ran like absolute crap until one day I decided to put the stock air filter back on. It has run like a swiss watch since that day. DERP on me.

I had variable venturi carbs (with diaphragms) when I owned a 1980 R80/7 BMW motorcycle. One carb each side (one for each cylinder). Yeah, they were pretty good.

Worked on air cooled engines for many years as a Porsche tech up in Dallas. Almost every carburated motor I worked on had down draft mikuni or weber. Individual runner for each cylinder, not very long runner either. How about a set of regular mikuni carbs on short manifolds for each cylinder? Those long, bendy manifolds are not helping peak power for sure. Call me crazy but I always enjoyed syncing up the carbs. 3 barrel down draft weber on each side. Great fun.

5:26 Treee Fiddy! Dat got dam Loch Ness monster..

Your videos have become a sunday tradition for me, keep up the good work!

The "work" you've done on various cars has always looked so fun. If I was your neighbor I'd be over at your garage so often, you'd probably get a restraining order against me. Oh, and I love the shots of those blue skies and green vistas. 😃

On the ram air idea, there is a difference in pressure between the fuel in the float bowl and the air in the intake pipe. If you connect the float bowl vent to the intake, I'll bet the mixture will be more stable. Rotax used to use this trick to their advantage in the 90s to tune their carbureted snowmobiles for higher altitudes. It was called a H.A.C. or high altitude compensator. Early versions used some kind of mechanical vacuum regulator, but later versions used a solenoid to regulate the negative pressure on the float bowl.

You have to have the carb vents in the ram air tube to keep the float chamber pressure the same as the ram air.

You could the breather from the bowl into the ram intake tube and it would balance out the pressure rise on the intake vs the bowl and it would maintain your AFR. Theoretically

Jimbo, I appreciate you take your time to do these fuel economy tests. As always, tip of the Hat to the Robot Cantina Team for all your efforts and mad science-ing. 👌🙂👍 P.S: The cold air induction it's always a blessing on ANY engine operating in warm climates. The whole ram air debacle: YUP, YOU NAILED IT ! It's the same as trying to run a blow thru turbo or supercharged system with a regular carb off an N/A engine.

Hey Jimbo, back for more like all the others here. Just a great Sunday vid, thanks man! 👍💪✌

Uncle Tony just learned about heating the intake on his slant 6 race car. It was causing stutter while doing 1/4 mile passes. Drove him nuts.

Just drove my 2002 ford focus wagon with 285k miles on it to the junkyard 150 miles away in 3rd gear on local roads . Tranny shot they gave me 175 dollars for it delivered . A guy picked me up at the junkyard in his 2000 Honda insight manual transmission car as a test drive . I bought it, had to, no way to get home! I seems to run fine and gets great Milage . When the engine goes who knows what I will put in it….

Smokey Yunick developed the Hot Vapor Engine back in the 1980's ,he used the waste exhaust heat to preheat the fuel charge so the fuel was fully vaporized before entering the cylinder and got 50+ MPG out of the awful Iron Duke 4 cylinder engine made by General Motors.

Good video! Recently Uncle Tony did a similar fix on his slant six drag car, he found that routing some exhaust heat to the intake manifold both improved his time and made the engine run smoother.

BMW used these CV carbs on their Airhead boxer engine bikes from the 70's and 80's. The carbs were made by BING. I have two on my bike and the carbs are fiddly, but work well when they are dialed in. Throttle response is slower by my experience to traditional carbs.

Im looking forward to seeing how the CVK carb works!

I have some points to make: * Using a shared plenum between carb barrels is not a good idea on an uneven-firing engine. One cylinder robs the other due to intake pulses being closer together in one part of the cycle than the other. * The "richer" readings you were getting with the carb shrouded might be due to more complete combustion from better atomisation. More oxygen is being used up, less comes out the exhaust, O2 sensor shows richer. * The long intake tube might be providing a tuned induction effect, which the carb may not be calibrated for.

Yes grease works. good,, I said cold air intake.. but you went for cold air plus ram. but I just said cold air.. hope it works good I love that car.

Ram air is doing exactly what it should do

My wife says she enjoys the fuel economy runs because she gets to see a part of Kansas.

As usual I enjoyed this vid very much. There's only so many Gen II 426-572 Hemi vids on RU-vid and I'm Hemied out! For those interested, the Keihin carb, like all carbs, load senses on the principal of there being an inverse relationship between manifold vacuum and Venturi vacuum. Where it is different over conventional carbs is it has a variable Venturi as opposed to the more usual fixed Venturi.

This car is a beast.

Thanks Jimbo for another cutting edge tech update delving deeply into the world of D&D (Dittle and Develope). 😂 I wonder if Albert Einstein started this way? You might want to consider a fuel flow meter, coupled with road speed to yield an instant mpg at whatever steady state speed seems best, just to save huge amounts of time. Of course, then other factors start to weigh heavily, such as air temperature, humidity, tire pressure, wind speed & direction, windows open/shut, and road smoothness & grade. Those variable venturi carbs have been used on motor cycles since the late 1980's. With the fuel/air mixture going all over the place, exhaust gas temperature would be a nice parameter to know. I don't know how much extra effort/expense these ideas would add, just some thoughts. Combustion temps peak out at about 15:1, so 18:1 may be okay.

Could you chop the bottom of the funnel off so that it is level with the fuel when the tank is full. You could then just keep poring in measured amounts of fuel until the fuel level reaches the bottom of the funnel (instead of having to take the funnel out, align the file and set square, then put the funnel back in, add more fuel, repeat).

You sir are living the dream! Love your channel. Hi from Australia 🇦🇺

Hey Sir, i have a gnarly suggestion. Being that the Saturn is a Metro and a Metro is Toyota based and it's 850 lbs lighter than a Tercel (made from Pvc, fiberglass, polymer and recycled refrigerator doors. Convert the SL2 into a quasi hybrid meaning Prius electrical mixed with Predator vtwin. GNARLY for sure.

All cars before the introduction of electronic fuel injection ran inlet manifold heating to aid atomization. In most cars, exhaust gases were used to heat the intake manifold but in some vehicles with inline engines and crossflow head coolant water was used. This system was also used in conjunction with a warm air diverter for the air cleaner to stop ice particles from forming in the carburetor venturi area and blocking the main fuel jet. The warm air induction tapered off as the engine reached operating temp because engine efficiency does improve with colder and therefore denser intake air. The more volume that enters the cylinder the higher the compression is and the more force generated by combustion, e.g. more power. As the engine is running more efficiently then fuel economy is generally better unless you let the extra power go to your head and push the foot down harder than normal. The new carburetor is a modern adaptation of the famous British SU units seen on so many British cars when performance was wanted and in the case of Jaguar they had up to three of them for a six-cylinder 3.8 and 4.2-liter engines.

I love this channel and this kind of experimentation! I look forward to each one of these videos, and I recon I ain't the only one. Looks like we are still in Kansas Toto. click click.

This is some fascinating testing in the real world very well explained and carried out.

Fantastic video as always, i want to see this puppy juiced up and roasting them little donuts its got!

Idea: go get a pick-n-pull 2 or 4 barrel carburetor and 3D print up an adapter (and riser if you need it). Carbs can be fairly cheap and rebuilding them is cheap, and they will let you ram as much air as you want.

We love the channel and the projects you are working on. Love Love Love the Saturn car wonderful design and execution of the Diesel engine happy some parts will get a second life. Thanks

Damn this is a hidden gem

Don't make the mistake of slapping an air filter onto the backside of the CV carb. It creates too much air turbulence for the vacuum slide to operate properly. The simple solution is to extend the distance between the carb and air filter with a PVC tube a minimum of 2-3".

A tip for the ram air intake, if you connect the breather tube of the carb into the intake, you compensate for the extra pressure, it will still lean out, but a lot less.

I appreciate how you've made the digital speedo easy to read on camera without needing a second camera. I don't think you mentioned how you did this.

I have found your voice double, even the manner of speech is the same! While watching coverage of the California hurricane a weather guy came on named Josh Breslow who works for FOX Now. Pretty amazing. The car is coming along well 👍

hey, for an easy mpg test with a constant load you could lift the car and get it up to speed and have something keep the peddle down to maintain speed , so you could work on other things while keeping an eye on it, less "real world" numbers but a less time/patience consuming option between mods, maybe you could even build something for the cars to sit on like an old car trailer flipped over so the tires are touching for friction for closer real world numbers , just a thought and I enjoy the content either way

Another option would be tyres for a spacesaver spare wheel. For 15 inch rim they'll usually be 125/80R15 and you can get them for free on a junkyard

Ram air needs a throttle butterfly to moderate the intake Velocity. Tuning the opening and timing used to be done with nonlinear linkages. You can use a constant Velocity carburetor with slides instead of throttle blades. These don't suffer from pressure increase upsetting the venturi. In all cases, calibrating the AFR is necessary. In the early 80s GM Rochester introduced PWM controlled jets for closed loop operation with a simple 02, MAP, temp, and other sensors plus a basic ECM. Thunderhead289s AFR cheater would probably help a lot for these experiments. That would allow you to get nearer to the volumetric efficiency limit of the engine and experimental accessories. Fun stuff!

I love this stuff. Look forward to seeing how these projects go. Reminds me of the days my mates and i spent in sheds with outboards, motorbikes and cars. You probavly already know but with ram air you need to pressure reference your fuel bowls. Tap a hose fitting in there to a plenum shared with the ram air.

you can make additional tube from the ram-air pipe to the float chamber, so when the pressure rises in the pipe, it rises in the float chamber too, making venturi work (for example - float chamber pressure will be 17psi, and venturi pressure would be 15 psi, because well, thats how venturi works)

Didn't know the cv carb was for atomisation, well explained! 👏