# Can you help an old gear head?



## Duncan (Dec 8, 2008)

Hi 
The SAAB is a nice car - I wonder if you could put a motor in the front driving something like a Subaru diff at the back

https://www.diyelectriccar.com/foru...dubious-device-44370p15.html?highlight=duncan


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## dhymers (Sep 9, 2013)

Damn Paul, I wish I was close by, I would help physically and financially.

Usually the fastest cars omit a transmission and go direct drive to a low ratio diff. Then there is the question of DC vs AC. DC motors torque tops out at a fairly low RPM and AC can keep going up to 6-7k.

I'm struggling with this decision myself, DC can dump "fairly" cheap power on the road but drive train considerations must be carefully done, AC has the RPM and efficiency advantage.

If your funds are limited you can do something similar to my daily driver truck, keep the transmission, DC Warp 9 motor and some sort of ~150kw capable controller (300kw is the next step up). 144v of CALB lithium 100ah+ (160ah or a higher voltage pack to go with your ~300kw controller is the next step up)
Make sure you put in a performance clutch!
Stock clutches are garbage for electric IMHO.

In a 2800lb car or truck, this setup will do 0-60 in about 8 seconds and will cost about $10k.

Anyone else have ideas ?


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## Colspaul (Jul 24, 2017)

dhymers said:


> Damn Paul, I wish I was close by, I would help physically and financially.
> 
> Usually the fastest cars omit a transmission and go direct drive to a low ratio diff. Then there is the question of DC vs AC. DC motors torque tops out at a fairly low RPM and AC can keep going up to 6-7k.
> 
> ...


Great information! Thanks!
would my current 700 auto transmission handle this torque? 
Maybe a real high stall converter?

I've used all sorts of gear boxes.
Even a Caddy Lasalle 3 speed with 1st and reverse removed in my old gas dragster.
but I'd like to make this one street able. 

Any other info?
anyone have gear to sell or trade?


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## dhymers (Sep 9, 2013)

I have zero experience with auto transmissions so I'm not sure. A warp 9 can deliver bursts of 350ftlbs at low rpm with even a ~150kw controller.
(http://spicerparts.com/calculators/horsepower-torque-calculator)

The transmission in my truck which was built for the Toyota 22R engine (72kw peak, 130ftlbs peak) has held up no problems. My battery/controller/motor setup can dump about 110kw for a while, about a 30% increase.

What I'm saying is you might have a little wiggle room to push it.

You could also go direct drive and use an overdrive or small 2 speed transmission, it would be streetable.


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## Duncan (Dec 8, 2008)

For a small car you simply don't need a transmission 
You can go 9 inch DC motor straight to something like a Subaru diff in the back


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## brian_ (Feb 7, 2017)

Colspaul said:


> ...
> would my current 700 auto transmission handle this torque?
> Maybe a real high stall converter?


Assuming for the moment that you want to use a transmission...

1. Why would you want to have a torque converter?
An engine needs some element which can slip so the engine doesn't stall when starting from a standstill, and that's either a mechanical friction clutch or a fluid coupling; an electric motor doesn't need that. A torque converter also cushions the driveline when shifting an automatic (and a clutch is disengaged during a manual transmission shift), but unless the converter has a lockup clutch it is a continual power loss for little reason.

2. If you do have torque converter, why would want a high stall speed?
With an engine, the high stall speed allows the engine to run up to the speed at which it produces maximum torque, before the torque converter couples, but the maximum torque from any type of electric motor is at or near zero speed.


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## Kevin Sharpe (Jul 4, 2011)

Colspaul said:


> Goals? Street driven, but not daily. Fast enough to embarrass the kids down the street with their fart can Hondas, quick enough to make passengers pee their pants!


I'd recommend you take a look at the Tesla drivetrains. You could put the Tesla in the back if you fancy RWD or in the front if you wish to keep FWD. I like the idea of RWD because you can put the batteries up front under the hood.

Three Tesla drivetrains are available... 'large' with at least 450HP (probably lots more!);

http://www.diyelectriccar.com/forums/showthread.php?t=182274

http://www.diyelectriccar.com/forums/showthread.php?t=188202

and 'small' (front and rear versions available) with ~200HP;

http://www.diyelectriccar.com/forums/showthread.php?p=905146#post905146


The Tesla drivetrains have open source controllers in development which will allow you to 'tune' the performance to meet your needs 

http://www.diyelectriccar.com/forums/showthread.php?t=185753


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## Kevin Sharpe (Jul 4, 2011)

Colspaul said:


> would my current 700 auto transmission handle this torque?


Don't bother with an automatic transmission... efficiency will be terrible... more here;


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## brian_ (Feb 7, 2017)

A complete powertrain from a production EV takes advantage of a lot of serious development work, and provides a properly matched set of components, including the transmission (single-speed reduction gears) and differential. The only obvious current production EVs with enough power for high-performance two-wheel-drive applications and any degree of salvage availability are the Teslas - so far, any variant of the Model S... although any current EV would have more power than a stock Sonett. Even a Chevrolet Spark EV (if you could find one wrecked - they're not common) has a compact and relatively powerful power unit (149 hp).

I would want to avoid the configuration of a Nissan Leaf and similar vehicles which are based on a front-wheel-drive car with an engine - they end up driving the front wheels but with a huge battery under the rear seat, making them rear-heavy when carrying passengers: that is a terrible configuration for performance. That leads to what Kevin suggested, with rear drive and the battery placed where you can, which would be mostly in the front.

Packaging is still a problem.

The Tesla rear suspension is nice but not usable, because it is too wide for the Sonett and the wrong type. A Tesla Model S has a rear track of 66.9 inches, while the Sonnet has a rear track around 48" (depending on vintage). The Sonett's beam-type rear suspension was never intended for driven wheels, or to clear a rear-mounted powertrain; I assume that the plan is to build an entirely new suspension.

The Tesla configuration puts the motor behind the axle (both front and rear); the rear motor is as low as possible (bottom level with bottom of differential housing), while the front motor is substantially higher (to sit over the front of the battery case). The Sonett is very short in the rear (how short depends on which generation of the Sonett), so this might be a concern for fitting the motor in the body.

Tesla uses open differentials (both front and rear), and controls wheelspin and stability with application of brakes to individual wheels. I don't know if that can be made to work with the do-it-yourself controllers (even if you put in a bunch of Tesla brake hardware), so you might want a limited-slip differential. Someone (possibly Kevin?) recently posted a link to video showing the installation of a worm-gear-type (probably Quaife) limited-slip into a Tesla Model S transaxle, so that can be done.


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## Colspaul (Jul 24, 2017)

brian_ said:


> A complete powertrain from a production EV takes advantage of a lot of serious development work, and provides a properly matched set of components, including the transmission (single-speed reduction gears) and differential. The only obvious current production EVs with enough power for high-performance two-wheel-drive applications and any degree of salvage availability are the Teslas - so far, any variant of the Model S... although any current EV would have more power than a stock Sonett. Even a Chevrolet Spark EV (if you could find one wrecked - they're not common) has a compact and relatively powerful power unit (149 hp).
> 
> I would want to avoid the configuration of a Nissan Leaf and similar vehicles which are based on a front-wheel-drive car with an engine - they end up driving the front wheels but with a huge battery under the rear seat, making them rear-heavy when carrying passengers: that is a terrible configuration for performance. That leads to what Kevin suggested, with rear drive and the battery placed where you can, which would be mostly in the front.
> 
> ...


All great information!

Yes , the Sonett is a iii, 1972.
it was hit in the right front corner, parked in a barn with the front end removed. Interior stripped out, rear pan rusted out.
I got it for a song. It started and ran. Fuel pump dryed out, clutch seal shot.
towed it home from the state up north.
had it finished , painted and on the street just after 9/11/01.
It was a hoot to race with the original 65 hp!
and up to approximately 100hp! Tightening it up with auto x slicks just demanded more power.
and the wife demanded pow steering! 
Hence the v 8 stage! 
So now, all custom tube frame, Miata power rack in the front and a Lincoln / t bird IRS narrowed drastically! All 4 corners on coil over , Cobra shocks.

So yes, I am sticking to rwd. Power steering? I'll ad a pump, somewhere! 
I'm not stuck on the auto gear box. It just came off the 1990 Camaro.
I'm fine with direct drive. If it is streetable. But I will need some reverse gear. Even if it is for on and off a trailer. But for cruises too. 
Motor behind the axel is fine. Battery's up front.? Leaving a little more room for two inside!
that huge 350 just looks so heavy for only ? 200 to 300 hp!
Tesla running gear? I'm looking at it! 
Thanks for the links!
anyone have gear to sell or swap for a fresh ice?
Paul


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## brian_ (Feb 7, 2017)

Colspaul said:


> So now, all custom tube frame, Miata power rack in the front and a Lincoln / t bird IRS narrowed drastically! All 4 corners on coil over , Cobra shocks.


That sounds like a nice setup. Not a Sonett any more, but a nice car 

The Ford IRS with 8.8 diff is a popular choice - available, strong enough for significant power...

The challenge using it with a complete Tesla Model S powertrain (motor with transaxle) in place of the Ford diff is that if you have the stock Ford subframe, the rear part of the subframe will conflict heavily with the motor, transaxle, and inverter housing. Almost any IRS for a front engine and rear-drive car will include a subframe component immediately behind the diff to support it, and that will be an issue with the Tesla unit.

A motor without transmission mounted directly ahead of the Ford diff would fit better, but gearing is a problem with a motor designed to run up to 10,000 rpm and only the final drive reduction.


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## Colspaul (Jul 24, 2017)

brian_ said:


> That sounds like a nice setup. Not a Sonett any more, but a nice car
> 
> The Ford IRS with 8.8 diff is a popular choice - available, strong enough for significant power...
> 
> ...


Yes, not much SAAB left except the glass body.
I bought a Jegs frame kit for the steel! And Scca cage steel.

The frame around the IRS is all out of my head! 
I can change that easily with a torch and tig.

Welding is a passion , after the temp drops below 90!

I expected RPMs to be in five figures.

So yes, some transmission will be in the mix! 

The tires can be chosen too. My old 50s gas dragster was like that. The slicks of the day were spun. Slipped. Putting modern, 70s , wripple walls on it , just snapped, axels, drive hook ups or sent the front wheels skyward!


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## Bru (Oct 3, 2019)

hi..newbie here...just curious to hear how this build turned out!
cheers


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