the fact the coolant isn't very warm on this engine stock is not necessarily a problem, since kubota likely designed it to operate under load as a stationary engine for very long periods of time, while being as thermodynamically efficient as possible, hence the cold exhaust manifold. by blocking off almost all the airflow to the engine bay with the airomods, the engine is likely now heat-soaking under heavy load, leading to your perceived power loss. additionally, without an oil cooler, the higher than stock RPM is probably getting the oil nice and toasty-you should probably be monitoring the temperature of that too.

Alright, I'll pitch in now. I own an 82 Isuzu I-Mark Diesel. .50 drag coefficient. From the factory, it is equipped with a 51 horsepower, 72 lb-ft 1.8L engine. On the tire size, from the factory, it was equipped with 155/70R13s. Those are difficult to come by where I am, so I run 175s. I also run my tires at 40 PSI. I've been able to pull 62 MPG out of it. 0-60 takes 20 seconds. Fastest I've ever had that car on a test track was 94 MPH. Not kidding. Anyway, just figured I'd toss you that information to give you a base for what was commercially available.

It's the boot spoiler! Removing that cost you 3 seconds! :-) Everyone know's they make you go faster! I reckon adding a couple of stripes will knock another couple of seconds off!

If you want to gain 30% more power do the LPG (propane-butane) injection to the air intake. If you never heard of this, search for LPG-Diesel. Actually I have this system mounted in my 2.5 Audi A6 C5 and it is working great. Before I installed proper system, I was experimenting by just putting hose from camp gas tank into air intake,.You can try this for beginning :) (this is short term solution, because without heating system for gas, nozzle will froze after few minutes).

Aero engineer by education here, a couple of tips to consider: 1. The spoiler does actually help with aerodynamics. You probably don't need to put the big spoiler back on, but you can get the little plastic stick on spoilers, or even just cardboard/plastic board plus tape to help the air at the back to separate from the trunk. You just want the air to ramp up a little bit. If the air can "jump off" the spoiler ramp a bit, then it can rejoin the airflow easier and reduce drag. 2. Another cheap thing you can do is try adding vortex generators to the back of the roof, to help the airflow stick to the back window as it flows down. Something like you see on Subaru WRX's. This will also help guide the air into the spoiler. If you want to crank the hillbilly aerodynamics up to eleven, you can add a full undertray and boat tail. The channel "think flight" has a small series about this for a better visual of what I mean.

This sort of reminds when I was 9 or 10 years old , riding a Kubota on a rice/padi field in my village.... Never in a watever lifetime a YT content gonna kicked my memory into reverse 😁

"It's not pretty, but it's, well, it's not pretty" Brilliant 👏 👏 👏

Try putting the spoiler back on. Strange as it sounds it might actually cut drag in your case. IF The airflow stays attached going over the rear of the car that can increase the air pressure acting on the rear window which has the effect of pushing you forward slightly or at least pulling you backward less intensely. If you have a pitot tube and/or a magnahelic gauge laying around that you can measure air pressures you can do an a/b test on that or if not you could do tuft testing with some yarn to at least observe the airflow to see if you have a separation bubble

Possibly fuel supply shortage? A turbo should lower EGT with the help of an intercooler. Looks good so far Jimbo keep it going 🙂

I'd bet the spoiler did more for aero than you may think. I know all late model cars and trucks have a hangover lip off the truck or tailgate to smooth Eddy currents at the rear of the vehicle. That spoiler might have done just that.

Seeing the engineering on all other videos I have no doubt you could add oil squirters to this engine. Tap into oil galley and just add them to stand alone rail inside block under rotating assembly. Honestly that would be simple compared to the other wizardry you have already done.

I wonder what effect covering the rear wheel wells like with the insight would have

Looking forward to the turbo test! In theory, you’ll be wide open throttle less if you boost it, so your EGT’s shouldn’t be too insane. I’d get a gauge for oil temps just in case, and run an oil cooler with a thermostat.

I'm afraid you might have blocked off air intake into engine, so it's possible that after some time of max throttle engine is starved of (cold) air, so maybe installing a cold air intake would work out, and since you have that area on bumper to cut, you don't have to ruin bonnet. Should slightly improve performance on high speed doubling as an inertia supercharger (air resistance in front push more air into engine) Cheers, that's a good project and video, Thanks!

Fender skirts? Increased tire pressure? Air scoop enclosed directly to intake? Front campaign sign mod increases downforce, try moving top forward and bottom rearward, so it looks like an arrow shape from the side (reduces downforce, reduces drag)? Lower oil viscosity,? Water injection? Continued success! Thanks for the video!

The transfer pump you are using is all the evidence you need of air bubbles in the fuel. Magnetic piston fuel pumps of that type are notorious for causing cavitation bubbles in fuel lines, especially with oil fuels like diesel. It’s a well known phenomenon in the self-installed diesel air heater community. Try mounting your pump on about a 25-45 degree angle with the outlet side up and the inlet side down. This is the first piece of advice given to anyone dealing with cavitation bubbles in a heater. I sincerely hope this helps. Thanks for reading my comment and thanks for all the great content. I have been watching since the insight first got a predator.

You should push the speed in 4th speed higher because it seems that the gearing makes the 5th very "long" for economy. When switching from 4th to 5th you go down to 2400rpm!

skinnier wheels will indeed have less rolling resistance and provide less air resistance. You can also max out the pressures to whatever the sidewall allows. You can also try to cover the rear wheel wells.

16:00 When you said "eventually when we add a turbo" I giggled like a little girl from excitement! This is awesome!!

Hi Jimbo, greetings from the UK and loving this project.

I bet removing the rear seat and front passengers' seat would be help for weight reduction. The best car to put the little diesel in would have been a late 1980's GEO Metro, they only weight 1650 pounds. But we use what we have for experiments. I like how you explain things as you go, it helps us who don't understand everything, understand. Thanks from Michigan.

The engine is likely heat soaking which would explain the power loss. If you put a hole in the aero mod for the intake air you will get way better power and lower egts. This bit will be very important for turbo charging as without the piston oilers and perhaps a oil cooler, you are going to want the air going in as cold as possible. Remember colder air going in give better power and fuel economy

Thank you for zooming in and showing the heater core is plumbed to the bypass tube. Many thanks!

Robot Cantina: Posts new D722 video Me: Searching Craigslist/Marketplace for a junker to do the same.....

To verify if the aero-mods are improvements or not, you could use cotton/textile strings and a camera to see flow separation, turbolence, etc. A Pitot tube or Magnehelic gauge are a bit more expensive but obviously more accurate. Would be cool to see the data of lift and drag before and after mods

Hey Jimbo, That was a fun video. You can fit a pressure guage to your fuel supply point at the pump, make sure you're not dropping fuel pressure at wide open throttle. That engine should be good for 1 Bar boost, it has a tough sub assembly. You can also safely go to 650 on the egt, but you may want to either intercool the boost or add water/meth injection...keep going !

okay so long term veiwer here, you got me into electrical back in the day, always been into cars and now i think this is the best channel on yt.

Hey, I had a diesel swapped SL2 a few years ago. Aero mods on mine were blocking the front ducting with plastic removing the side view mirrors and having mirrors mounted inside the doors that could see outside. They were basically a convex mirror. Worked well. And on the sedan at least the front lights were inset on the body. The lights were mounted on stand offs to ouch them out to be more level with the hood and front bumper. And finally the wheel covers were like the flat ones you see people running at bonneville. Car got about 90-100mpg when driven nicely. And even driven hard it was capable of 50-60mpg.

Try adding water meth when you go about installing the turbo. It will help drop charge temperatures and will also add more fuel into the system. Also that aero is probably a bad idea since you’re going to want that area and air flow for a intercooler. Like another viewer commented rig up a cool air intake, your power loss is most likely due to the engine breathing hot air. It’s not about how much boost you can cram into an engine but how much air density you can feed it.

You need one of those little English muffin sized turbos for that engine now

I did an experiment on a VW Polo 1.4 TDi a few years back. Reduced weight by as much as possible, aerodynamic mods such as narrow tyres, closing off un-necessary ducts and removing anything that caused excessive drag. Had the engine slightly modified with a custom remap, a more free flowing exhaust. Can't remember exact figures but it achieved slightly over 100mpg and the performance was incredible

2:00 That is 100% correct. It's a thing amongst older Jeep guys to take off the passenger mirror, because it's almost totally blocked by the windshield anyways

Such a fun project to watch! We can't see what the exhaust is doing, but if you're giving it more fuel then it may also not be buring it completely. Maybe consider adding a propane injection when you get the turbo on? Thanks for sharing!

I just want to say thank you for converting those numbers for us, all metric folks out there. Keep up the good work!

The majority of small diesel equipment engines that are turbocharged are running low boost to help with widening the torque bulge and keep revs consistent when the load varies. Typically, manifold pressure is 4-6 psi so an intercooler is not really needed, nor are piston oil sprayers.....however, the majority of turbo Kubota's do utilize a water/oil cooler under the oil filter. An air/oil cooler would probably be easier to fabricate and would greatly help with engine/turbo longevity, especially when holding full throttle for long periods in top gear.

I'm so glad you write the metric values! It is warming up my heart!

Come on turbo, we added a oil cooler with our mod on our old cummins, that was a good move. Might want to watch that oil temp. Have a wonderful week. God Bless

Very Nice! Fun times had by all!

The exhaust on my Cub Cadet with a D600 Kubota gets very hot. It has a stamped metal safety guard. Under heavy load it blows black smoke, 54" snow blade, chains and tractor tires. I use it to plow my drive way over on Fox road by MIchigan ave near your old stomping grounds. In cold weather the tractor runs very cool, the only time I see the temp gauge move is during summer. There were Cub Cadets that came with those diesels. The garden tractor pullers use a turbo from a European smart car, its 3 cylinder, and has the turbo built in to the manifold, you just need an adapter plate. The Military also had d722T on their generators.

Simply fascinating! Such high-quality graphics and explanations!

I'm impressed with those numbers. Good as a VW TDI or little Saab TDI. Obviously, the recirculation of the exhaust gas will balance the increased KW Joules nicely. ✌️♥️👍👍 Maybe the drag at the rear should be red yarn tested with three or four 1 meter lengths across the trunk lid. In practice the yarn will likely not fly straight away but instead suck back into the low pressure drag ares created by removing the vortices extending wing. Good for a guy riding your tail on motorcycle but not for acceleration and fuel savings.

a small turbo with a few pounds of boost would solve every problem with speed, and make it so the car doesnt need to have crazy aero mods. Plus, turbos for diesels increase overall efficiency and can easily lead to more MPGs Maybe a k03 turbo from an older audi / volkswagen turbo engine would do well... The inducer size on those is like 30mm so not too big for the baby sized engine

Highway tires with the least rolling resistance, smaller and lighter weight wheels, +15% recommended tire pressure. (Pre turbo) Intake piping to ram air intake, change intake manifold to 3 independent, long, and thinner? tubes. Possibly angle them greatly from the valves to increase turbulence pre-ignition. Someone mentioned lower oil viscosity but I imagine that will need a change of bearing clearance if you intend to change boost. You could get stiffer valve springs and get an increased RPM. Love your videos

Can confirm a 26hp Kubota tractor engine has cool exhaust at idle, cooler yet in winter.

Thanks for another interesting episode! That little Kubota is gonna go places :-) Wondering what new thrills and chills (or pitfalls) the turbo is going to bring. We'll see next Sunday :-)

I took the spoiler off of mine because I liked the clean look without it better but it actually hurt my gas mileage a bit. More modern cars will have a little lip on the back of the trunk lid that would take the place of this spoiler for you. Manufacturers claim 1-3% increase in fuel efficiency from that, so it has to reduce drag significantly.

You took the wing off and made it slower!😄

That was awesome to see it accelerate so well on the doughnut tires and gain a few mph👍

Very interesting stuff!!! Keep it coming!!

it’s good to see another 18v makita impact driver up to no good on cars, at least i’m not the only one

Once again you made me chuckle ! Love your sence of humor ! Love those graphics too !

It nice to see your channel growing so fast. these one of a kind engine swaps are so much fun to watch and you present it so well.

good to see you’re doing better jimbo!! keep up the good work. highlight of my weekends

You should have left the dirt, it added a low pressure zone causing the air to help push the car forward! Lol I can't wait to see more.

Some of these have already been said by others, but: Power loss might be due to warmer intake air temps from closing off the grille. (Also, worse aero can notably hurt near-top-speed acceleration.) Maybe could run a hose from the rectangle hole in the airdam to the engine intake? Removing that spoiler might make aero worse (that type of spoiler is probably catching airflow coming off the roof and helping it separate from the car cleanly). Blocking unnecessary air from going into the engine bay with that airdam is good, but a sharp 90-degree transition at the bottom of that airdam is not good for aero. An easy way to make that a nice smooth curve is to get a length of foam pipe insulation two or three inches in diameter; slice it in half lengthwise so it's a semicircle in shape, then glue it round side out to the airdam so the bottom edge of it lines up with the bottom edge of the airdam. So that from the side (with the car aiming to the right), a cross section would look like a lowercase b.

12:10 Cold exhaust at idle. This is typical for a diesel. The excess air running through the cylinders keeps the engine cool. This is why idling a diesel for long periods is a bad thing as it leads to " Wet Stacking" / lots of carbon. Some gas engines during a cooling system failure shut down alternating injectors to limp home the car.

The spoiler helps with drag. It elevates the trunk and helps the flow to reattach. If you want to reduce drag further, look into making sharp separation edges on it and on the bumper.

Looking forward to the turbo test. Diesels LOVE boost

The extra air from boost will help cool the exhaust some up to a point as it will lean the mixture back out to normal. The mixture now is rich , and should be running cooler but its diesel and I don't know enough about the fuel system. Normal exhaust operating ranges can vary and be quite high on some engines. This is at full load in 5th right now . Its laboring. Boost will make a huge difference. 6 to 10 lbs. Would be a great improvement

on mechanical pumps the optimal pump setting is a little smoke at low rpm and clean burn near top, put a cold air intake because without the engine bay airflow the under hood temps might get really high and especially diesels need really cold air for best performance, if you run out of fuelpump you can raise the inlet pressure to the pump in mercedes mechanical pumps you can raise it from stock 1 bar to 2 bar without problems dont know how much you can raise it on that and if you still dont have enough fuel you can make a water/meth injection system and get a little bit more, pump timing makes a lot of difference especially at higher rpm, 800c egt temps shouldnt be a problem, i havent had any problems on my mercedes om603 without piston oil squirters, thank you for the great videos cant wait for the next one!😄

Thanks Jimbo! Once again you made my weekend better! I brag on your channel all the time and the shenanigans you get in to, love it!

Dope ass channel keep her coming!

I’m loving the channel! Everything I’ve ever seen from home built aero says that’s your problem. Remove the front covers, which will improve the aerodynamics and probably help keep your EGT down.

More fuel equals more heat only to the point that it will flow air. Controlling combustion temps is an art unto itself. Controlling the oil temperature is very important since that also helps control piston temps. The affect of piston oilers is not as great as most people think because oil is naturally being slung up against the bottom of the pistons anyway. Control intake air temp and oil temp and water temp and you find it much easier to control combustion temps. Increase the fuel until you need water injection to control combustion temps. Aluminum melts at 1000-1200 degrees if I remember correctly BUT just because your egt hits 1000 does not mean that's how hot your piston is. The constant cooling of the pistons from the skirts and the oil on the bottom of the piston keeps it much cooler. Keep that oil temp below 190F and it will work wonders to keep your piston the proper size. On the bonus side the water injection gives a bit of a power boost you can feel in the seat of your pants. My experience is via a GM 6.5 turbo diesel marine build in an old van with no intercooler. Just a "devil's own" water injection kit. Extra large oil cooler with auxiliary oil cooler. I've hit 1100 degrees with it climbing some mountain passes. I'm a chicken so I don't push it past that much. I've heard of guys pushing higher though.

Id recommend advancing the pump timing to make some power

stop messing around and bolt on the turbo, I have this same engine and want to know what its capable of, lol. todays video answered a lot of questions I've had about the fuel enrichment screw, thanks.

Every time a video is posted I can’t wait to click and watch… of all the content this is the channel I get the most excited for

This is one of the best shows on the entire KZfaqs.

Needs a air dog 165gpm lift pump,125hp injectors and a 63mm turbo and it will be golden 🤣

Love your videos!

I love love LOVE this project and I can’t wait to see future videos 😀

A fire breathing monster and a speed demon if I ever saw one ! 🤣 Great job, RC Team ! I so much prefer these type of videos than the big dollar budget with the sponsors and unattainable results by the humble home mechanic. I'm watching this as a wolf down some brunch. Your videos make it all better. 👌😃👍

Excellent progress Jimbo! Do I hear a bad wheel bearing? That is additional mechanical drag if so. Does the Saturn trans use atf or gear oil? If the latter, then a swap to GM Synchromesh oil will reduce drag further. Look forward to the turbo installation!

man this channel is so charming. Just curious, are you getting weird harmonics with that engine or smaller wheels/tires? i hear some odd noise on your acceleration test.

A little info on diesel egts, as you said there is no throttle for air so at low power times they'll run extremely lean which keeps the exhaust cool because there isn't enough energy in the fuel to make excessive heat, same reason for high idle switches for cold warm up. With adding a turbo if you can keep it at that point of being lean enough to keep cool it should be very efficient. Many people on the internet will argue this but if you add enough fuel you can keep the egts down as well, and get more power than lean cool. Another option would be injecting straight methanol under boost, I would expect impressive results from that. I would expect that lil engine to hold up to a decent amount of boost if you keep the egts down, don't turn up the timing, and keep the charge temp cool.

Hey Jimbo, thanks for another cool video. It's amazing the interest us mechanical types have in retrofitting an old Saturn with a garden tractor engine. Figured I would add my 2 cents, hopefully not covered under other comments. This little engine is probably used at 1,500 to 2,000 rpm in the garden tractor application so, I wouldn't be too surprised if fuel delivery was subpar at redline engine speeds. Since it is January and air temperatures will vary considerably from one week to the next, or even morning to afternoon, it may be difficult to compare "apples to apples". The colder temperatures (obviously) increasing tire rolling resistance and the air is more dense. Using a consistent tire pressure would help (which you are probably already doing). When I owned Saturn SLs and SCs, to give the best weight distribution across the contact patch equated to 42 - 44 in the front, 28 - 30 in the rear. With your lightened Saturn, I suggest 40 - 42 front, 27 - 28 rear.

Can't wait for a turbo

This would be interesting to run on the salt flats, probably do very well in a power/weight calculated division

It's good to see you've recovered enough to get back on the road! I hope your family has recovered from The Thing That Must Not Be Named.

I think the lack of improved acceleration time to 55mph (1:09.50) can be attributed to the lower power from having to shift to 5th (as well as time needed to shift). It looks like times to 50mph were about 50 seconds with the big wheels/tires and about 44.5 seconds with the small wheels/tires. I think if you were able to use a CVT and all other variables were the same, the times between big and small tires would be most noticeable. That is, unless I’m missing something here, which happens from time to time. That said, I love these kinds of projects. Thanks for sharing yours!

Thanks for sharing this engine was new wasn’t it when you started so it’s not broken in yet so it should run better after you run it more and change the oil once I’d think

That little diesel sounds lovely, though I've always like the noise that 3 cylinder engines make. The fuel delivery on a turbo diesel should be matched to boost pressure, otherwise you'll still get smoke off boost. If you were keen I suppose you could use a servo or stepper to adjust the rack stop automatically if that is a problem.

Great work I always advise fitting a electric fuel pump and 3psi will greatly assist fuel pump and add ease of bleeding up fuel an old diesel engine will appreciate the modified fuel system and be more spirited in its gallop lol 😆 thank you 😊

Turbulence inpacts aerodynamics a lot. Covering up all the panel gaps, window edges and headlight wells with self-adhesive tape or vinyl should do some good. Also reducing the ride height by like 6 ft, and adding a cover sheet for the undercarriage. Then there's the unsprung mass, and also getting enough air into the wheel wells to stop drag on the tires. Basically everything people did to 70's Nascar racers will work. Also this diesel engine is screaming for a turbo! Love the content by the way, keep it coming! =D

You don't need a wind tunnel, I'm sure a CFD company or a CFD engineer would be happy to help you model the car and run the *simulations*

One thing that can help is lighter wheels. I’m sure those little steelies are pretty light but when it comes to rolling only a few pounds means a lot more. I’m sure you knew that though just wanna see some nice rims on the beast performance wise that this is

Yay. The smaller wheels were my suggestion from a few videos ago. Maybe you were going to do it anyway. Looking forward to seeing the results.

can't wait for the day you buy a v8 sedan like the ls400 and put in the work to get 40 mpg . keep it up!

Sweet!!

I think you should use the insight wheels on the saturn to test if the lighter weight, combined with the wheel design could reduce drag and make it go faster! I just looked, and both sets of wheels should have a 4x100 bolt pattern with an offset range around 45. Who knows, maybe even a cardboard and duct tape mock up panel to copy the insight (rear wheel well panel) would help too!

Another good video. Not sure why I find your videos so interesting but I am like a kid on Christmas eve waiting for Santa to bring presents as I wait for your next video. lol Phil

This feels like if the Mythbusters narrator had an episode all to himself lol

I think the boot spoiler really helps earo dinamics. In some other video i saw it helps with flow separation of the boot. Those jelly bean styled cars date from a time with a genuine oil crisis and they were not fooling around.

Having a 999cc turbo 3 cylinder gasser in my daily driver, I find this series quite intriguing. My brother has the same car I do but with the naturally aspirated 4 cylinder. We both have five speeds and the difference is very noticeable. His transmission has much shorter gearing and close ratios. Mine has much taller gears and significantly wider ratios which I assume is to give my turbo a chance to spool up and do something. I'm curious if the close ratio transmission is going to be a problem during acceleration once the little Kubota gets the Turbota.

The pyrometer (exhaust gas temperature), is the best way to know just how a diesel engine is performing. you can figure as the exhaust temperature rises water temperature will rise along with it. there is some amount of over fueling that is acceptable. but if your smelling raw unburnt fuel then it's over fueling too much. a small puff of black smoke when shifting gears is acceptable. as long as that is the only smoke that is detected. there is a huge difference between turbo charged and naturally aspirated engines. and you want to have an intercooler with the turbo. but you will really have to keep an eye on the pyrometer. if the temperature rises too possibly nine hundred degrees for that engine. back out of the throttle and the will drop. and on both turbo charged and naturally aspirated engines you will want make sure the exhaust system is large enough diameter. it's important that diesels have free flowing exhaust. and don't ever shut off a turbo charged diesel with the pyrometer over six hundred degrees. I know this from many years of being an OTR truck driver and have ran a lot of turned up diesels.

Fun stuff as always. I'm excited for the turbo!

Mount motorcycle tires on the spare wheels! (idk if motorcycle tires are better durability than "temp spare tires", because they don't last much longer on a vehicle that weighs ~1/4 as much, with twice the tires)

Just get smart car tires on the donuts

I'm helping with engagement! Not really much to add on this one that others haven't stated... great stuff.

Subscribed for more madness in future. Now I dare you to design and test ducted fuel injector nozzles and install a compound turbo setup for the little Kubota diesel for ultimate efficiency.