TCU TurboLamik

Howdy folks. I could use some help with a project. If you have any useful input, it would be appreciated.

I'm planning on using an 8hp on a 1/4 scale tractor pull. I'm using a 34hp Kawasaki EFI motor, but as per the competition rules, I can't modify the motor in any way and that includes drilling a hole for a vacuum port.

I've contacted turbolamik US about using the analogue harness and he replied that I need MAP, RPM and TPS. TPS and RPM is doable but I don't think I can get MAP.

So I sent a message to the email address on the European website and they said I can go without map, it's just that the shifts will be harder, which is fine by me.

So here's the real dilemma - I'm actually going to be using gear reduction *before* the transmission (as well as after) because I need to maximize wheel torque and because the motor is a vertical shaft motor so I'll be needing to convert it to horizontal via a gearbox.

So basically, the input speed on the transmission is going to be quite low. If I use a 3.23 ratio, it'll only be about 850-1110rpm. Could this be an issue? Perhaps the oil pump wouldn't be spinning fast enough to execute shifts quickly? If someone has experience with this, it would be greatly appreciated. Honestly I'd like to use even high reduction than that, but that might be pushing it.

And also, what should I use for RPM input? I haven't been able to find any documentation on that.

Lastly, can the transmission be programmed to only shift based on RPM? I want it to keep the engine in its peak powerband at all times. I don't care about comfort/fuel economy or anything like that. Just performance.

Thank you for the help!

I've used the TCU with TPS/RPM only and have had success. Most race engines have no vacuum with large overlap cams. You can scale the TPS to act like load, although it sometimes lags during on-off conditions.

For MAP, I've used a pilot tube positioned horizontally to the intake and inverted the MAP calibration (more vacuum = more load). This works great on older naturally aspirated diesels that don’t rev very high.

I haven’t tried a reduction on the torque converter, but I’ve set up a CV belt from a snowmobile to achieve something similar. It holds a specific RPM regardless of load, which is great for max torque.

I can’t comment on the actual line pressures in the transmission, but it would be interesting to see how much torque it could hold at a given RPM.

Have you looked at the transmission’s first gear ratio? It’s already very low. With 4.10 or 4.56 gears in our trucks, it’s low even with tall tires.

For RPM input, you can wire up your own crank sensor and trigger wheel or use a tach signal. Just set the input source in the TCU along with 'tooth' count. This one is easy imo.

As for the shifts, I’m not sure I fully follow, but you can set shift points for each gear to whatever you want. Shifts can be triggered manually or via an external ECU. You can set your start and end gear to and use it as a 2 thru 8 speed. Lots of options here

Thanks for the reply.

I'm glad to hear it works with just TPS and RPM. We're really optimizing the setup for just one scenario - WOT at maximum RPMs. Anything less than maximum load isn't of concern for us, so we'll just program it accordingly. The motor also doesn't have much rotating mass.

The pilot tube idea is very interesting, though. If we do find that we need map, that might just work.

We should be at an absolute maximum input torque of 164 ft/lbs, seeing as the 8hp45 is rated for about double that, I think we'll be alright. I just hope it copes well with being run at such a low RPM... pretty much our biggest unknown at this point.

The reason we need such gear reduction is because our top speed is going to be, very optimistically, about 16mph. Our goal is to keep engine RPMs as high as possible, because the motor has a very steep power curve. So we've got around 3.15 first stage gear reduction, 4.7 first gear in the transmission, and 5.37 in the rear axle. About 80x gear reduction haha, but that will only be about 17x gear reduction if we manage to hit 5th gear going a whopping 12mph.

Good to hear about the RPM too, that's easy enough.

And as far as shifting - you've answered my question. I just want to make sure I can set my shift points to whatever I please, ignoring load, only based on RPM. With a manual override, too. F30 shifter gonna look pretty goofy on a tractor haha.

Just kind of thinking of this as a slowed down drag race, but it ends whenever you run out of momentum and wheel torque. So we want to maximize acceleration to gain momentum, and as the load increases from the slead and we lose speed, we gain wheel torque by downshifting.