924Board.org

[skemcin]

I recently posted this:
http://www.924board.org/viewtopic.php?t=22328

which began a pretty interesting conversation. So I am going to do a little research and try to document it here. I am going to research the in the overall difference in weight between all the parts needed to run an internal combustion engine(from a 79 924 na) versus an electric engine.

Below is a list of ICE parts that would be removed from the 924 when preparing the car for an electric motor install. I just need your help with two things:

Request:

• weigh any spare parts you have laying around that are related to an ICE
  
• correct/contribute to my parts list - let me know if I am missing something

The following list is a work in progress. I, by no means will be able to define this without your help - please feel free to reply with additions or correction and I'll edit this post accordingly.

Items to Remove:

• 308 lbs / 140 kgs - Engine - block, head, throttle body/carbs, plugs & wires, starter, alternator
  
• 60 lbs / 27 kgs - Exhaust - header, downpipe, catylitic converter and back, muffler, tail pipe
  
• xxx lbs / xxx kgs - Fuel - Gas tank(empty), fuel lines, fuel pump
  
• 20 lbs / 9 kgs - Cooling - radiator, hoses, air compressor
  
• 45 lbs / 20.5 kgs - Interior - front and rear seats, carpeting

Notes:

• The radiator may say as some electric systems are water cooled
  
• The air compressor motor - if I choose to restore the A/C in the car, then the current compressor will be replaced with an electric motor
  
• In the interest of maintaining near 50/50 weight distribution, I might look at the possibility of mounting the main motor and control system in the rear above/in front of the rear axle or rear seat and then stack two rows of batteries in the rear of the engine compartment or visa versa depending on the amount of room needed for each.
  
• I added the interior section so the racing folks can add their two cents on how to reduce weight. I know I have the front seats - I'd like that calculation so that when I do the new EV version I will add in the race seats that I have currently.
  

Estimated Total Savings = 433 lbs / 196.5 kg
(thus far)
_________________
924.org (no time to complete)
9249206346 - 89k – new shifter bushings, belts, running well.
9249206347 - 8k – waiting its resurrection, no power at the fuel pump and fuse #7 blows w/power

[Martijnus]

hmm i've got a spare engine in the garage... which I can weigh...

Haynes says it's 140kg...but I don't know how complete their weighing is....including manifolds and stuff...

radiator is out too... and so is the kjet...
Oil could be approximated... 3liter equals 3 kg or something like that..
If you guess/take everything a bit lower than it appears the outcome of the saving is always in a positive way...


Don't think my bathroom scale can hanlde the engine...but hey...I'll try if I get the chance (which isn't soon ...damn exams..)...
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

[skemcin]

That will be a big help. Thanks.
_________________
924.org (no time to complete)
9249206346 - 89k – new shifter bushings, belts, running well.
9249206347 - 8k – waiting its resurrection, no power at the fuel pump and fuse #7 blows w/power

[Rasta Monsta]

Your poll is missing an option. . .Too Slow, Too Heavy
_________________
Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[skemcin]

[leadfoot]

I would suggest in the interest of weight saving that you convert all major panels (quarters/hood/spoilers) to fiberglass and make a perspex rear hatch.
If you look at the various models that have done this it is easy to get the car down 100/200kg, Most of these cars still have a turbo/sc various EFI parts/intercooler fuel pump etc so you can keep reducing weight from there on... just going off racecars that have managed to get down to 900kg

I guess bellhousing,clutch,torque tube and gearbox go too... so this would be another decent reduction
so minus engine and above your looking at 150/200

It might be possible to start with a rolling chassis of 700kg...
then start adding you E.V parts minus 1 X battery allready installed
Leadfoot
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

[skemcin]

[endwrench]

Not sure if you have seen this post but I have been keeping a running tab on weight savings of various things I have done.

http://www.924board.org/viewtopic.php?t=18254&start=0

You'll have to page thru the post for the actual weights of various items such as the exaust system. I'll be pulling my radiator soon and I will weight it too.

Even if you don't actually do this I would like to see a rundown on the parts list and what you think it may cost to do it. I think it would be a viable option if you lived in town.

Todd
_________________
'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....

[Petrovich]

You might want to wait with the batteries for a year or so. Firefly is getting its carbon-graphite lead-acid ready for production - nothing seriously ground-breaking, but should easily halve your battery pack weight, at the same price. Or if you have a big wad of cash, you can go with li-ions now - pack them into aluminum pipes and then stuff those where the transmission tunnel is. Will need a good charging circuit, though.

As for motors, I'm still waiting for R/C motor manufacturers to "get it". They're already making 2-kg, 15kw motors. I say they're cluelessly sitting on a gold mine. If you move this up a magnitude, you get a 20kg, 200hp motor. Couple it with a 50-mile small battery pack and you have a conversion that's actually desireable.

[Keaton]

put a medium battery pack and one of these, then you can charge at your house, using you house. and when your batts get low you can charge while driving

http://cgi.ebay.com/NEW-5500-WATT-10HP-DIESEL-5-5kW-PORTABLE-GENERATOR_W0QQitemZ320125648115QQihZ011QQcategoryZ106437QQcmdZViewItem

and you can use old veggie oil to power it

[skemcin]

[skemcin]

I'm still tracking down some information but I wanted to share some numbers that I think are correct - I need to track down a couple sources that I used to double check my findings since they seemed to be quite impressive.

First before I share the number I want to state on the advantages of an electric motor and why they can be so attractive. The traditional internal combustion engine (ICE) measures performance in horsepower, but the number we alway here about is the maximum horsepower achieved at a certain RPM. At any other stage, the ICE does not produce as much HP and is not as efficient. The electric motor - by contrast - has all its equivalent horsepower (measured as killowatts - kw) at 0 RPM - or instantly. This makes it more efficient in that it delivers power instantly. One additional finding to note is that the average car, once up to speed, may only need no more than 10 hp to sustain momentum - depending on terrain and wind of course - often time much less.

Having said that, here is what I've found specific to our lovely 924:

FYI: 1hp is roughly 0.744 kw and various sources calculate electric motor kw requirements to be about 1/4 of the ICE equivalent rating

ICE Stock 924:
125 hp (93kw)
2,448 curb weight
19.58 power to weight ratio

Budget 924ev:
30 kw motor (~209 hp)
3,100 lbs curb weight (traditional lead batteries)
14.83 power to weight ratio

High-Roller 924ev:
40 kw motor (~279 hp)
2,700 lbs curb weight (carbon free lithium ion batteries)
9.67 power to weight ratio

So what does this mean for the 924ev? Well, off the line the car is still slow - in fact arguable much slower - but that can be controlled. But once the vehicle is up to speed, the throttle is two to three times more responsive than an ICE version. That means quicker out of turns, quicker on and off ramp acceleration, etc - we are already used to losing drag races). From some of the figures I've been able to collect, it would seem possible to even get the power to weight ration into the low 8's with fiberglass panels and other track like weight saving techniques referenced in previous posts. The reduced rate only gets the car closer to the ICE off-line performance and widens the gap in all the other areas - including range.

For the last point, I'm not 100% sure on my calculations on range and I'm seeking some help on this from an EV discussion board - but I think Budget 924ev would get 50 to 75 miles where the High-Roller 924ev would hover around 100 miles. But range has yet to be accurately scrutinized.

Any thoughts?
_________________
924.org (no time to complete)
9249206346 - 89k – new shifter bushings, belts, running well.
9249206347 - 8k – waiting its resurrection, no power at the fuel pump and fuse #7 blows w/power

[rat]

If going down the route of making the 924 electric, it makes sense to bin the gearbox completly, have each wheel driven by its own motor which can also be made to act as brake.

Not too sure how useful this is, especially since there is no indication on prices, however...

http://www.pmlflightlink.com/motors/hipa_drive.html

Is a comercial unit to do just that. Far greater power ratings than listed previously too.

[skemcin]

[Rich H]

First of all, keep up the good work!

But why a 924? Why not start with a much lighter chassis in the first place? Either start with a car that is much lighter and adapt that (Lotus Elise for example an earlyu version has a kerb weight of 750-800kgs 1700lbs in full trim) or why not look at a kit car or similar that can be built with elecric power in mind form the start. Something like a Caterham/Westfield/Locost (600kgs/1400lbs in full lightweight trim)
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec