[Yabert]

Originally Posted by njloof

One thing I don't understand is why you would build a 144v x 120Ah pack over a 288v x 60Ah pack. Even if you're targeting a 170V motor, the controller can modulate the pack voltage to the motor's limit, with a corresponding increase in amperage. That would be pretty voltage sag proof, no?

You are right!
144v vs 288v was just an example.

But if you target 120-150 hp, I don't see reason to build 288v battery pack.

[njloof]

Higher voltage, less amperage, less heat in the wires, no? Up to the motor's voltage limit, I mean. It just seems disadvantageous to end up feeding lower voltage to the motor at high RPMs.

[njloof]

So I emailed the Kostov guys; they hope to have dyno numbers on the Alpha in a couple of weeks. I like the higher (5500 RPM) redline on their 11" motors.

The next best choice seems to be the K9" 220V. I'm still favoring the higher voltage to ensure I have enough torque at higher RPMs at reasonable amperage (~500A). 6800 RPM redline is as good or better than the ICE.

Right now I'm driving the car to get a feel for how it performs with the ICE. The insurance grace period ends in another week, at which time I garage it, file for "non-use" and drop the insurance. Then it's time to pull and sell the engine, not necessarily in that order.

[MN Driver]

The redline for the 9" motors is 7000rpm, the nominal is 6800rpm. Basically what it means is that if you are feeding it 220v 176 amps and have a 42nm torque load at 6800 rpm it is rated for 31.2kw for an hour.

If you want to push any more than 176 amps through the motor at that speed you need a higher voltage pack than whatever would sag to 220v at 176 amps. From the chart in that other thread your peak torque is at 4500rpm or so unless you are pushing more voltage because the amps start to drop there. I'm not sure what the commutative limits are but 250v was fine according to Plamenator in the other thread but be sure you aren't going to go over 7000rpm. I'm looking to go with 100 cells of 60Ah with a Soliton Jr so that sag won't be an issue, although it's a 20kwh pack of prismatics so some care would need to be taken to be sure that I'm not drawing too heavily against it and getting the battery too hot through heavy discharge but then again I'm looking to convert a 1900 pound aerodynamic car pre-conversion so I'm not too worried, it'll get to 60 fast with a setup like that.

[njloof]

Prepping to pull the engine at the end of the month. Once that's done I'll attach a mockup of the motor to the transmission and start looking at the fitting issues.

Early specs on the K11 Alpha look pretty good. Integrated forced air gives me a little more confidence about pushing 1000A at low RPMs. I think that's nominal 5800 RPM I see on the site? If so, that seems pretty reasonable; that would be ~100 MPH in 5th. K9 220V is a very decent fallback if the mechanical issues of the 11" motor prove more hassle than they're worth. I'm curious as much as anything else at this point; I may still choose the smaller motor in the end.

This thread needs some pics soon. So far nothing to show that doesn't look like a stock Miata.

[njloof]

Compression checked the motor... not perfect (210/180/180/210), but not bad for a 20-year-old engine with 145k miles. Looking around for a buyer on the Miata forums.

Received the Warp 11" mockup from EV Source. Once we have the engine out we can reassemble this with the transmission and do a test fit. I want to be absolutely sure the larger motor is going to work. If I end up with the Kostov 11" motor I'll have an extra .2" of clearance on both sides, but I'm hoping it won't be *that* snug a fit.

Also received the hub and adapter plate. Kerryman, if you're watching, cancel your order and get one from EV Source/CanEV instead... mine arrived in about two weeks from the order date.

Next weekend: drain, disconnect and pull engine.

FWIW, the EVMiata folks just hired a new welder, so my kit may have some delays. The part I really need first is the motor mount.

To DJBecker's point: the EVMiata kit has already saved me time in the planning stages, since it lets me predict how many batteries I can fit, and where; and it takes most of the welding out of the build, which is not my strong suit. Plus, those guys have been very supportive and answered lots of my questions, both through their step-by-step instructions and many emails.

[njloof]

Well, seven hours later, my friend Andy and I wrestled the engine out of the car. Getting at some of the transmission bolts was... amusing.

CIMG0248s.jpg
Andy brings his heavy equipment.

CIMG0251s.jpg
Catching the wild 1.6L ICE.

Next step is to transfer the flywheel/clutch/plate to the 11" motor mockup and see what it will take to fit it. It's pretty clear it will hit the steering rack first, so that'll be the thing to look at.

[DJBecker]

You didn't pull the motor and transmission out still joined? It would have been easier that way. You'll eventually need to pull the transmission out anyway.

[njloof]

Transmission stays, at least as far as the EVMiata manual says. Once the hub and adapter plate are on the motor, I mount it and bolt it back on.

Light progress in the last couple of weeks. Took the clutch/plate and flywheel off the engine:

CIMG0252m.jpg

... and drained the gas tank. Every set of instructions said to loosen the drain plug until your arm is soaked in gasoline, and they were right. A gallon and change later and I put it back in. Have to figure out a clean way to fill the tank with soapy water (siphon, probably) so that I don't set any remaining fumes on fire with the plasma cutter later.

[Batterypoweredtoad]

I would suggest just dropping the rear subframe to get the gas tank out. Subframe removal is not that difficult.