openinverter forum

So I am planning on doing something a little different than your standard hybrid. Instead of a IC piston engine I am using a small-ish Garrett GTP30-150(F) turbine engine. Turbines kind of suck for cars, other than their horrible fuel economy, because the shaft output is mostly a fixed RPM. In the case of my engine I have two PTOs, one 8000RPM, and one at 12000RPM. Rated HP for the engine is 150 and actually puts out about 130 at the shaft.

Video of the first startup here if anyone is interested:

And I want to put this thing in a cart. Poor man's Batmobile, lol. Other than some complex mechanical solution the other option that people have use is hydraulic. Neither of these seem appealing to me.

So, my plan... Take two Kia/Hyundai HSGs and connect them to the 8krpm PTO and run them as alternators. Each would have its own bridge and feed to a common filtered bus. From the testing I have done with the HSG I have it looks like I should get around 270vdc loaded at 8krpm. If ORNLs info it to be believed I should be able to get at least 40kw out of this setup. This all seems to fall in the inverter's operating range.

Thinking of taking that and feeding it into an Outlander rear drive and inverter and use one of the teensy VCUs to control it. Come up with a cooling system for the gens and the motor and inverter should be pretty simple.

I think this should work. Am I crazy? (Yes, but that's beside the point)

This sand rail frame showed up on FB Marketplace this morning for $200 so I jumped on it and picked it up this afternoon. Everything turns, pretty basic VW bug based buggy. Will need a sandblast and paint when I am done making modifications. Oh, and real wheels.

IMG_8585 by Jerry Biehler, on Flickr

you need a HV battery in between to buffer the torque demand when (de)accelerating. Experience has shown us torque reaction from ICE to PMSM are order of magnitude apart and to bridge this gap you need a power source that can quickly buffer the torque lag. Either battery or supercap of some kind...

arber333 wrote: ↑Sun Mar 15, 2026 8:08 am you need a HV battery in between to buffer the torque demand when (de)accelerating. Experience has shown us torque reaction from ICE to PMSM are order of magnitude apart and to bridge this gap you need a power source that can quickly buffer the torque lag. Either battery or supercap of some kind...

Im planning a cap bank, I have done this before for servo drives to handle to sink the regen into something to keep the DC buss from overvollting.

Second Kia HSG showed up today and I managed to get the pulley off this one and lucked out with it being the keyed shaft version. This will make it a whole lot easier to couple to the PTO shaft on the engine. 

Ive decided to build a low capacity pack to act as a buffer. I think it will be about a 88s2p pack of LiFePO4s which should give me about 316v at 5AH. Enough to move it around without starting the engine. The pack will be able to supply 240A for 10 seconds.

Main components are all ordered. Drive, Inverter, Brat's adapter splines, VW CV flanges.

All in all the turbine/battery/inverter/drive combo should weigh about the same as a 1600CC VW engine and transaxle. I started removing unneeded parts from the sand rail, plasma cutter helped a lot with that. Also found a set of usable rear tires off marketplace which will make it a lot easier to move around. I need to pressure wash and strip the paint off this thing.

IMG_8620 by Jerry Biehler, on Flickr

IMG_8610 by Jerry Biehler, on Flickr

Parts are starting to trickle in. The VW 90mm hubs showed up a couple days ago, the poly-v belts yesterday, the pedal and inverter unit showed up today. Waiting for the rear drive to ship.

I machined the plate that interfaces the back and front bells from the old generator and holds the second generator offset from the shaft. Im waiting for the rear bell bearing and once I get that I can machine the outer shaft that the pulley that drives the second generator rides on. I have a pieced of 4140PH left over from another project I can use for that.

I might try one of those custom Orion 2 BMSes on ebay for my battery pack. I'll never hook up to a standard charger so the lack of features is not an issue for me.

IMG_8635 by Jerry Biehler, on Flickr

IMG_8636 by Jerry Biehler, on Flickr

IMG_8637 by Jerry Biehler, on Flickr

Got the support plate bolted to the adapter and started figuring out how I am actually going to attach the belt driven generator, Once the coupling and bearing arrive I can start machining the outer shaft. I ordered a parabolic drill to drill out the shaft, it's going to be pretty deep. 

Also messed around with the servo for the soft starter. I put together an RC circuit and then found my messing with he sensitivity pot on the servo itself I could set it to go few travel over a few seconds with just using a switch contact. Easy enough. I drew up a mount to attach the servo to the resistor, I'll hook up O2 to the laser cutter tomorrow and cut that part out of some sheet steel.

I got notification the rear drive shipped too.

IMG_8642 by Jerry Biehler, on Flickr

IMG_8641 by Jerry Biehler, on Flickr

Brat's spline adapters arrived yesterday and the rear drive arrived today. Drive looks like it survived the trip from Japan even though it was covered in coolant. Guessing they didnt blow the water jacket out. Rotated the motor by hand through the drive hubs and it turns smoothly.

I lifted the drive into position with an engine hoist and used some nylon straps to hold it in position about where I want it. Going to pick up some 1x2" steel tubing tomorrow to make the mounts.

IMG_8652 by Jerry Biehler, on Flickr

IMG_8657 by Jerry Biehler, on Flickr

IMG_8658 by Jerry Biehler, on Flickr

I can see the cart flying!!! 80kW is available from OEM control loop, if you modify brain with OI than you can release up to 115kW!!!

Now the way i see you want to use the HSGs (why two, it would just add complexity?) i would see you can use Honda inverter with Lebowski brain in simple starter generator sensorless mode. You wouldnt even have to use encoder or resolver sensors as turbine starting is not a huge load.
How Romale did it
https://openinverter.org/forum/viewtopi ... =honda+IMA

And on other forums
https://endless-sphere.com/sphere/threa ... ep.119952/

I am working with a simple SMD Lebowski board and i just got it up to respond to my commands. Now i will put it on the IMA inverter and test run HSG motor in sensorless mode. Will post results... Later on i will also work with resolver to encoder conversion...
https://openinverter.org/forum/viewtopi ... 107#p89107

At this point I just want simple to make it work. The HSGs are good to about 24kw a piece, im going to add some forced air cooling to supplement to keep the exposed winding cooled just in case. The prime mover on this will be the engine, the battery is just the buffer. Honestly, I could have just used a single outlander motor as a generator but I think I might have issues getting it to fit. I can always change things around later. The two HSGs will fit nicely in the overall footprint of the engine. The engine has its own starter so there is no worry about that.

Got the teensy controller ordered from JLC and the box for it arriving soon.

lumonic wrote: ↑Fri Mar 27, 2026 5:37 pm At this point I just want simple to make it work. The HSGs are good to about 24kw a piece, im going to add some forced air cooling to supplement to keep the exposed winding cooled just in case. The prime mover on this will be the engine, the battery is just the buffer. Honestly, I could have just used a single outlander motor as a generator but I think I might have issues getting it to fit. I can always change things around later. The two HSGs will fit nicely in the overall footprint of the engine. The engine has its own starter so there is no worry about that.

Got the teensy controller ordered from JLC and the box for it arriving soon.

The HSGs are liquid cooled so you should be good up to 18kW each .
Will you be using my new board wuth ULN2003 chips? https://evmeganetech.wordpress.com/2025 ... velopment/
If you need to load firmware and are tight on time i can send you my hex already compiled for CAN2 driving Outlander motor, inverter, charger, heater and AC compressor.

According to ORNL they were able to pump up to 24kw into the HSG, but really im only ever going to see that kind of power draw on heavy acceleration. Between the HSGs and the LiFePO4 pack which can supply 240A for 10 sec, I think this thing should be pretty quick. Im considering mounting the batteries up front to give this thing a little weight in the nose so when I add disc brakes to the front it will have a bit more grip.

I had a set of both your boards and the other ones made up since I would be paying more for shipping than for the boards. I have not ordered any parts. I think I have most of the stuff for the version with all the through hole components. If you could give me a BOM for your version I could order a set of parts for that.

I'll need to edit out the stuff for the charger, compressor, and heater. None of that will exist here. Maybe throw in a charger at a future date but I have other ways of charging the pack for now.

Speaking of I need to get the BMS ordered.

I placed an order for tubing to mount the rear drive as well as the turbine. Online Metals has a location here in Portland and I can just pick stuff up directly, they are so much cheaper than Metals Supermarkets. Also ordered the isolation mounts for the turbine from McMaster.

lumonic wrote: ↑Fri Mar 27, 2026 9:58 pm
I'll need to edit out the stuff for the charger, compressor, and heater. None of that will exist here. Maybe throw in a charger at a future date but I have other ways of charging the pack for now.

No need to edit out components for first tests. They will just not populate those variables. Motor and inverter will still run. You will need Prius/Auris throttle pedal though as my VCU is calibrated for that particular pedal. It uses dual signals.

I tested Outlander components from 240Vdc to 400Vdc...

I'll look up that pedal. I picked up a BMW pedal with dial signals but I can get something else. It was cheap.

If I used the 12krpm PTO on the turbine I can probably get closer to 400v but a lot of the bearings are not rated for that.

Ordered a whole bunch of parts today, CVs, brake parts, metal for the engine and motor mounts, bolts, and rubber mounts. I chopped loose the upper part of the rear roll cage which was in the way and will need to be moved. It was barely welded in place. Once the engine is in ill come up with something else. Spent a bunch of time figuring out where I can put the engine, it's going to have to mount a bit further back than I anticipated. The generators will stick out a little further than I anticipated.

One other thing I was working on was a soft starter for the engine. Usually there is a big series resistor that limits the maximum current to the starter to avoid just slamming the gearbox of the engine. I couldn't find one anywhere. Someone suggested a battery load tester so I picked up one of the cheap "500A" load testers for $60 to extract the carbon pile resistor that was inside. Then I'd drive it with a big ole' RC servo with analog position input. I was messing around with a RC circuit to feed into the analog input of the servo and ramp up over 4-5 seconds. I probably would have ended up needing to ad an opamp to get the full range. Playing with the sensitivity pot on the servo I found I was able to adjust the servo so it just moved slower and all I need is a resistor to pull the analog in low and then when I connect the analog in to 5v it ramps up over about 4 seconds. I'll just add another relay in parallel with the starter relay. Or get an another relay with an aux set of contacts. The solenoid pulls about 17 amps so it needs something decent sized.

IMG_8671 by Jerry Biehler, on Flickr

The packs from battery hookup showed up yesterday and after a couple hours I got the pack apart and the cells stripped. Need to see if my laser cutter will cut nickel. I can blast through steel and stainless way thicker but im not sure what it will do to nickel. I have seen recommendations using nitrogen as assist gas, which I have. I also need to pick up a spot welder.

I pulled the drums off the rear axles and talk about a mess. Going to need to replace everything inside, while im in there I will replace the spindle bearings too. The drivers side seems ok but the passenger side does not feel great. The backing plate on the passenger side needs a little straightening too. I yank them off and bead blast them at work.

IMG_8675 by Jerry Biehler, on Flickr

IMG_8676 by Jerry Biehler, on Flickr

IMG_8677 by Jerry Biehler, on Flickr

IMG_8680 by Jerry Biehler, on Flickr

Got the metal for the rear motor mount Monday. Also picked up my MIG machine that I had over at a friend's shop so I can weld all this up. I could TIG it but I want to be done sometime this year.

I talked to an apps guy at work and I should be able to cut .15mm copper sheet with the lasers at work so I ordered some stock for that, drew up the interconnects in solidworks so I have DXFs ready for when it is time.

Spend the past couple days machining the shaft that adapts the old quill shaft from the old DC generator to drive the new generators. Screwed up the first one, it was .005" bent over its length so I did it like I should have the first time and turned it between centers. Waiting for a .3795 reamer to ream out the shaft for a shrink for over the old quill shaft. Machined it from 4140PH, I managed to burn my lip and hole in my sock with hot chips.

Lots of other parts arrived. PCBs for the controller, the Orion 2 BMS, brake pedal, brake parts, CVs, etc.

IMG_8701 by Jerry Biehler, on Flickr

IMG_8706 by Jerry Biehler, on Flickr

IMG_8685 by Jerry Biehler, on Flickr

Between yesterday and today I got the rear drive mounted. Using 1"x3" 1/8" wall tubing to mount it to the existing transmission mounting points. Did some other miscellaneous stuff too like broach a keyway in the generator coupling and mill off a piece of the HSG housing. Ordered some wrong brake parts so waiting for the right stuff.

Now I need to figure out where and how to mount the inverter.

Copper sheet arrived so I might be able to cut the battery interconnects out this week.

IMG_8719 by Jerry Biehler, on Flickr

IMG_8720 by Jerry Biehler, on Flickr

IMG_8718 by Jerry Biehler, on Flickr

IMG_8722 by Jerry Biehler, on Flickr

IMG_8721 by Jerry Biehler, on Flickr

Last night I put the axle stub shafts in the ultrasonic to clean them up, I went to paint them this morning and noticed that there is a lot of wear on the outside bearing journals. So they are junk. Ordered another set that are chromemoly, another $150... sigh. This thing is a money pit.

Cut the keyway in the shaft and cut the grooves for the snap rings to hold the bearing in place. Cut the quill shaft from the old generator and it looks like my reamer cut a little oversized. I could get the shaft to go about half way and then I had to use the press to get it in place. I used some green loctite and I'll drill for a 1/8" dowel pin later. I think it will hold, 48kw at 8000rpm works out to about 42 lb-ft which isn't a whole lot in the scheme of things. I guess we will see.

Also made up a plate that will mount to the face of the direct drive alternator and will mount to the end bell from the old generator.

IMG_8725 by Jerry Biehler, on Flickr

IMG_8726 by Jerry Biehler, on Flickr

​​​​​​​IMG_8727 by Jerry Biehler, on Flickr

Over the past couple days I got the generator section together. I Made the standoff pieces from a chunk of 1" 1144 that I have had around for probably 25 years now. Man, that stuff machines nice.

I decided to mount the second generator though the 4 case bolts like I did with the first one. I want to try and reuse the existing belt tensioner and to do that the spot where it needs to be to get tension means I can use the large mounting bosses on the housing. I made more standoffs from that 1144 and counterbored about .3" into the casting on the generator for a spigot on the standoff to sit into so I dont have all the tension on the 6mm bolts holding it together. I used 7/16"-20 SHCSs to hold the standoffs to the plate.

Man, this was a pain in the butt to get together. And im glad I bought a couple different belt sized because the one I designed around was a touch too long, the size down I had seems to be fine.

I lubed up the spline and put it into place. it seems to turn freely, ill need to fire it up this weekend with a bridge rectifier and a couple caps on it to see what my no load voltage is going to be at. Should be around 277v if I remember right.

Picked up some more steel today to build the mount for the inverter and whatever else. Also got the components to build the VCU. Stub axles also came in and got those installed. Still waiting for som brake parts to show up so I can put the wheels back on.

Getting closer... This is probably one of the most involved projects I have done. Also a huge money pit.

IMG_8738 by Jerry Biehler, on Flickr

IMG_8741 by Jerry Biehler, on Flickr

IMG_8742 by Jerry Biehler, on Flickr

I spun the engine up on the starter alone to see how everything worked with the generators and almost immediately the belt jumped the pulley. Not sure why, the pulleys are in line and parallel to each other. The only thing I can think of is the belt tensioner. It is on the slack side of the belt like it should be but it may be the arm is facing the wrong direction. Not much I can do about that. I looked at making a sliding tensioner adjustable with a bolt but there is just not enough room. So I machined out three of the four mounting locations for the generator into slots and left the fourth as a pivot. This way I can just tension the belt by pulling it back and tightening the bolts to hold it in place. Tested it with a drill to drive them and it tracks fine, ordered some more belts because the one installed was damaged.

Looks like crappy weather for the next few days so I spent a few hours this evening doing some work to the frame. Made spots for three of the four mounting points for the inverter while also beefing up the front motor support. I cut the cross piece out where the engine is going to go and ground out some of the leftover metal from places where tubes had been cut off in the past. Also designed a gasket for the cover plate on the inverter. I'll burn it out on the laser cutter when I get around to it.

Also did some searching and I think I found the right snap rings to hold in the CV stub shafts. Mitsubishi didnt make it easy.

Screenshot 2026-04-12 105354 by Jerry Biehler, on Flickr

IMG_8752 by Jerry Biehler, on Flickr

IMG_8761 by Jerry Biehler, on Flickr

Finally some dry weather. Got the inverter mount finished. I modified a couple of the feet to get them closer to the same level. Every foot mounts on a different plane.

The seats should be here this week and I can figure out where to mount them and where the pedals need to be. Also took the backing plates for the rear drums to work and cleaned them up with the bead blaster and painted them tonight. I think I have everything now to put the brakes together. 

IMG_8780 by Jerry Biehler, on Flickr

IMG_8782 by Jerry Biehler, on Flickr

IMG_8781 by Jerry Biehler, on Flickr

Brakes are done and it's finally on the wheels. I need to figure out routing for the motor phase leads and resolver, I have some 4AWG wire that should do the trick. Need to pressure was the thing, still has a bunch of grime all over it.

Seats should be here tomorrow and I can start figuring out where everything else will go.

Belts arrived and I got the generators back on the engine. I ran it up this morning and am making 330vdc no load, a bit higher than expected but then again my test setup was not the most accurate when it came to measuring RPM. The belt behaved how it should. Now that I know the max voltage I can size my battery pack appropriately. It looks like I'll be doing a 92s2p setup.

Short video here:

The seats arrived Monday. They fit well and are pretty comfortable. That evening I got out a zip disc and went around the rail and cut loose the old seat mounts and every other piece of crap someone had welded to it sometime in the past. Ill be able to reuse the old 1/4x2" bars the old seats were mount to, I need to add some captive nuts to the seat rails to fit. Also pressure washed the frame and the driveway while I was at it, it was needing doing.

The Mitsubishi snap rings showed up for the VW adapters so I was finally able to get the CVs installed. Mitsubishi 3717A030 is the part number. I also set the inverter in place and routed one of the phase wires so I can cut the rest to match.

With the voltage as high as it is I decided to go with a full 96s2p battery config. I ordered spacers for the 26650 batteries and will need to redesign the cell jumpers for the new pack when I get them. Using 96 cells should protect the pack even if the engine overspeeds to its shutdown speed.

IMG_8809 (1) by Jerry Biehler, on Flickr

IMG_8810 (1) by Jerry Biehler, on Flickr

IMG_8815 by Jerry Biehler, on Flickr

IMG_8816 by Jerry Biehler, on Flickr

IMG_8817 by Jerry Biehler, on Flickr

Make the lower motor mounts for the turbine. I designed them so they will keep the big 5/8" fine thread SHCS that hold the isolation mount captive and even if they managed to unscrew they cant unscrew far enough to extract from the mount on the engine. Also the top strip goes around the tube so it would really have to break to come loose.

​​​​​​​I machined a piece of 2" aluminum tubing to what I measured as the spacing between the engine mounts. Boy, I sure hope I got that right. Im planning on bracing the lower tube diagonally back to the frame to stiffen it and also sleeve the lower piece to give it a little more meat. 

I cut the strips to hold the seat down too. I can weld those in tomorrow. 

IMG_8818 by Jerry Biehler, on Flickr

IMG_8820 by Jerry Biehler, on Flickr

IMG_8819 by Jerry Biehler, on Flickr

IMG_8821 by Jerry Biehler, on Flickr