743 engine change v2203 Kubota (743 gauges)

[mclark]

Here is my 743 with a V2203 refer motor in it. Had to flip muffler to reduce heat in engine compartment. Machine had no shroud or finned flywheel (could not locate one) Added 3 toyota cond. fans to radiator and one under hyd. cooler. Had to do a bit of hot rodding on this 743 as you can see. Ran a pipe from filter to pull in cool air at door. Little bit of plumbing pipe for intake. Added top cover to keep out the rain and snow. Think I'll put a shield between muffler and fans as not to pull hot air through radiator. She seems to run alittle hot.

 

[Rojas]

THe "Finned flywheel" is actually a centrifugal fan. Works at high static pressures. The best advice is to go find the OEM setup and put it back in there. If you insist on trying to go electric I think you'll blow a bunch of cash trying to make it work. Maybe someone makes a well engineered kit that will git the job done. That's your second best bet.... Some comments about what you've done so far.....I don't know your fan sizes but the cond fans look to be ~8" or less. You need bigger and you need to pull through the full core face. No ram air on a bobcat.... Two 12" fans are liable to give you allot more air. Build a box to act as a plenum and mount the fans to that. Get fans that will work at hight static. Probably around .7". Don't look at CFM claims. There is allot of nonsense claims in the aftermarket and big CFM numbers are almost always open air where the fans not getting any work done. insist on seeing the fan curves

 

[Rojas]

In the second picture the fan appears to be sticking out of the plenum and there is a large gap along the back edge. Honestly, you wont stand a chance like that. The water jackets in the head were notorious for cracking in that little Kubota when you overheat. I would hate to see all your work spoiled. Take a look at the Derale 16928 dual fan setup. I know these fans work at high static pressure and you might stand a chance with something like that. Allot of small block V8s using that setup with no problems. That fan draws over 500 watts however, so you may need to upgrade the alternator. If that wont fit on the bottom side, the same fans are available individually. You could build a sheet metal plenum and mount them on the top as pushers. On the salvage side, I believe Lexus used a hydraulic puller fan on some models.... What do the factory parts run from Bobcat? Surely there's a salvage 743 setting around somewhere.

 

[mclark]

In the second picture the fan appears to be sticking out of the plenum and there is a large gap along the back edge. Honestly, you wont stand a chance like that. The water jackets in the head were notorious for cracking in that little Kubota when you overheat. I would hate to see all your work spoiled. Take a look at the Derale 16928 dual fan setup. I know these fans work at high static pressure and you might stand a chance with something like that. Allot of small block V8s using that setup with no problems. That fan draws over 500 watts however, so you may need to upgrade the alternator. If that wont fit on the bottom side, the same fans are available individually. You could build a sheet metal plenum and mount them on the top as pushers. On the salvage side, I believe Lexus used a hydraulic puller fan on some models.... What do the factory parts run from Bobcat? Surely there's a salvage 743 setting around somewhere.

Looking for a salvage 743 now, did'nt check with Bobcat as don't want to go into shock. Everything seems high, just paid $38 for the radiator hose to thermostat. Found a 743 about 1 1/2 hrs away sitting in a guys yard for at least 5 years will be contacting him about parts to return to orignal setup if the machine has'nt been changed as mine was. In the mean time I'm going to install a plenum and try to install two 12" fans on top. As you can see from the fan I installed under hydraulic cooler I don't have a lot of room. Will let you know if it works. Will also check on the Derale16928 dual fan setup also. Thanks for your input.

 

[mclark]

Looking for a salvage 743 now, did'nt check with Bobcat as don't want to go into shock. Everything seems high, just paid $38 for the radiator hose to thermostat. Found a 743 about 1 1/2 hrs away sitting in a guys yard for at least 5 years will be contacting him about parts to return to orignal setup if the machine has'nt been changed as mine was. In the mean time I'm going to install a plenum and try to install two 12" fans on top. As you can see from the fan I installed under hydraulic cooler I don't have a lot of room. Will let you know if it works. Will also check on the Derale16928 dual fan setup also. Thanks for your input.

There is no gap between shroud. The fans are 1/8" away from radiator. The radiator is only 10" wide and the fans are 9". They don't draw enough air , the plemun I think is the answer and a larger fan setup.

 

[Rojas]

There is no gap between shroud. The fans are 1/8" away from radiator. The radiator is only 10" wide and the fans are 9". They don't draw enough air , the plemun I think is the answer and a larger fan setup.

My comments about the gap in the shroud was in reference to the puller fan mounted on the oil cooler. A plenum on the pusher side will make a big difference. With three 9" fans mounted directly to a 10x28 core you are covering about 68% of the core face. That's a 30% reduction in capacity. If you build a plenum you will lower the pressure drop (each fan will move more air) and use the full air side capacity of the rad. You can knock something up out of wood to test. A deep plenum is more efficient, but there is a point of diminishing returns. I'd probably use 1" deep minimum with 9 inch fans. Since the rad is much more rectangular than square three smaller fans might be better than two larger without building a really large plenum. What size is the finned area of the rad, length by width? Where are you located at?

 

[mclark]

My comments about the gap in the shroud was in reference to the puller fan mounted on the oil cooler. A plenum on the pusher side will make a big difference. With three 9" fans mounted directly to a 10x28 core you are covering about 68% of the core face. That's a 30% reduction in capacity. If you build a plenum you will lower the pressure drop (each fan will move more air) and use the full air side capacity of the rad. You can knock something up out of wood to test. A deep plenum is more efficient, but there is a point of diminishing returns. I'd probably use 1" deep minimum with 9 inch fans. Since the rad is much more rectangular than square three smaller fans might be better than two larger without building a really large plenum. What size is the finned area of the rad, length by width? Where are you located at?

I just stuck the cooler fan in there to add a little more air. The rad finned area is 30 1/2" X 10". With the shroud on them one fan sticks into the bottom (left side) of rad about 1 1/2 and does nothing, thus reducing air flow to even less . I'll build a wooden plenum as you suggested and try it with the three fans. Thanks for the suggestions. I live in Washington state. On the Olympic peninsula accross the water from Seattle. Where are you?

 

[Rojas]

I just stuck the cooler fan in there to add a little more air. The rad finned area is 30 1/2" X 10". With the shroud on them one fan sticks into the bottom (left side) of rad about 1 1/2 and does nothing, thus reducing air flow to even less . I'll build a wooden plenum as you suggested and try it with the three fans. Thanks for the suggestions. I live in Washington state. On the Olympic peninsula accross the water from Seattle. Where are you?

I'm down in Texas. If you happened to be in the area I thought I might be able to lend a hand. I can't tell for sure from the pictures, but the fans you have look to be Denso units with their disk motor (~80 watts). I don't have much confidence that they will get the job done. Three of the 10" Spal VA15-AP70/LL-39S (~180 watts) would probably get you in the neighborhood.

 

[mclark]

I'm down in Texas. If you happened to be in the area I thought I might be able to lend a hand. I can't tell for sure from the pictures, but the fans you have look to be Denso units with their disk motor (~80 watts). I don't have much confidence that they will get the job done. Three of the 10" Spal VA15-AP70/LL-39S (~180 watts) would probably get you in the neighborhood.

Well I made up a sheetmetal plenum as you suggested, 31/2" high and installed all three fans(will post pics). Pushes alot more air than before. Ran bobcat for 1/2 hr to get heat up. It got to 220 degrees which is better than the 240 it reached the other day. But I think the temp should be in the 180-200 range. The engine came with no thermostat so I will put a 180 in and see if that changes anything. I was told that I might be able to make the fans I have run faster. Do you know if this is possible? Where would I look for the Spal VA 15-AP70/LL_39S fans you mentioned? Thanks

 

[Rojas]

Well I made up a sheetmetal plenum as you suggested, 31/2" high and installed all three fans(will post pics). Pushes alot more air than before. Ran bobcat for 1/2 hr to get heat up. It got to 220 degrees which is better than the 240 it reached the other day. But I think the temp should be in the 180-200 range. The engine came with no thermostat so I will put a 180 in and see if that changes anything. I was told that I might be able to make the fans I have run faster. Do you know if this is possible? Where would I look for the Spal VA 15-AP70/LL_39S fans you mentioned? Thanks

Hey, your workmanship looks pretty good on that plenum! One improvement would be to have a straight section ~.75" to transition to the included angle. In the grand scheme of things it's probably trivial point. Might keep it in mind if you make another. Might be worth a few percent. To make the fans run faster you will need to increase the voltage. It's not really practical in your application. It can be a good way to determine the fan operating point required. You can attach an external power supply to the fans and increase the voltage until you get the heat rejection you need. At that point you record the fan speed and current. You really need to be working with a fan supplier or have some known system characteristics or a way to measure them. And be advised, you can toast the fan motors really quick this way. That's the reason I inquired as to your location. I've got the equipment to be able to determine the fan characteristics required without going through allot of iterations (money). I recommended the Spal fan as a starting point because I've tested enough of them know their fans preform in line with their data sheets. In the high performance line they have a VA02-AP70/LL-40S FAN (9" HP) and VA15-AP70/LL-39S FAN (10" HP) pusher fans. At 20mm of static pressure they move 580 and 860 Meters3/hour with power consumption of 150 and 180 watts respectively. It appears Spal sells these fans direct from their website for 172.00 each. I saw lower prices from some of their distributors. If it were me I'd look for someone who would let me return the fans, no questions asked, if they did not work for my application. That way you could try the 9" fans that should mount directly to your plenum and the power consumption is lower. My recommendation is based on the assumption that the fans you have now are ~90 watt Denso units. Can you measure the current and voltage on one of the fans you have now? I don't believe adding the thermostat is going help. It needs to be in the system but mass flow is mass flow. You will probably see some reduction in heat rejection.

 

[mclark]

Hey, your workmanship looks pretty good on that plenum! One improvement would be to have a straight section ~.75" to transition to the included angle. In the grand scheme of things it's probably trivial point. Might keep it in mind if you make another. Might be worth a few percent. To make the fans run faster you will need to increase the voltage. It's not really practical in your application. It can be a good way to determine the fan operating point required. You can attach an external power supply to the fans and increase the voltage until you get the heat rejection you need. At that point you record the fan speed and current. You really need to be working with a fan supplier or have some known system characteristics or a way to measure them. And be advised, you can toast the fan motors really quick this way. That's the reason I inquired as to your location. I've got the equipment to be able to determine the fan characteristics required without going through allot of iterations (money). I recommended the Spal fan as a starting point because I've tested enough of them know their fans preform in line with their data sheets. In the high performance line they have a VA02-AP70/LL-40S FAN (9" HP) and VA15-AP70/LL-39S FAN (10" HP) pusher fans. At 20mm of static pressure they move 580 and 860 Meters3/hour with power consumption of 150 and 180 watts respectively. It appears Spal sells these fans direct from their website for 172.00 each. I saw lower prices from some of their distributors. If it were me I'd look for someone who would let me return the fans, no questions asked, if they did not work for my application. That way you could try the 9" fans that should mount directly to your plenum and the power consumption is lower. My recommendation is based on the assumption that the fans you have now are ~90 watt Denso units. Can you measure the current and voltage on one of the fans you have now? I don't believe adding the thermostat is going help. It needs to be in the system but mass flow is mass flow. You will probably see some reduction in heat rejection.

Added thermostat and am looking at making up a heat shield for my exhaust and engine to deflect some rising heat.