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Electric Porsche

167K views 393 replies 52 participants last post by  Joey 
#1 ·
After 10 years, I'm finally able to begin my electric car conversion. My goals are 0-60 MPH in < 8 seconds, 100 mile range (60 is an absolute min) at 80% dod, >80 mph top speed, and 4 seats.

I've narrowed the donor car decision down to two: Porsche 944 or Porsche 911/912. I would prefer the 911, but not at the price they seem to be selling for in my area, $14 -20 k USD (1978-1989). The 944 goes for between $1,000 - $5,000 (1983-1987).

For components I don't think I will stray too far from what a lot of people have been doing:
9 inch Warp - keeping the clutch and flywheel
Soliton Jr, or Soliton1
56 cells at 130 aH CALB or 48 cells at 180 aH
Manzanita 20 - The idea of long recharging times (12 hours) doesn't bother me
Battery monitoring and instrumentation - not selected yet

I'm thinking that the batteries will be the system bottleneck and any money I can squeeze from the bugdet should go there. Not sure how many will fit without messing up the weight distribution too much.
 
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#6 ·
Top tip, wait until a Porsche boxter engine blows. They are driven usually quite hard and failure rate is high enough to find them. This could help with keeping donor costs low.
I've waited 10 years already. I can wait a little longer to get a good deal. I do need 4 seats though, so the boxter and 914 are out.
 
#3 ·
100 mile range
Using the method here,
http://physics.ucsd.edu/do-the-math/2011/07/100-mpg-on-gasoline/
and just accounting for air drag, to go 100 miles at 33 mph using the vehicle cross section and drag coefficient in the link you'll need 2200 w-h.
At 67 mph you'll need 8800.

0.3 =Cd
3 =A, cross sectional area, m^2
1.3 =p, air density in kg/m^3
30 =v, velocity, m/s
60000 =D, distance traveled, meters
E=0.5(Cd)pAD(v^2)
31590000 =calc'd E, energy, in joules
8775 =calc'd E, energy in w-h

The energy used to cancel out rolling resistance is another calculation, as is your accel requirement, as is your top speed.
 
#5 ·
Using the method here,
http://physics.ucsd.edu/do-the-math/2011/07/100-mpg-on-gasoline/
and just accounting for air drag, to go 100 miles at 33 mph using the vehicle cross section and drag coefficient in the link you'll need 2200 w-h.
At 67 mph you'll need 8800.

60000 =D, distance traveled, meters
Thanks for the link. I think D should be 160000 meters (= 100 miles). Then the needed energy is 23500 for 100 miles, or 235 watt hours / mile.

I was estimating 250 watt hours / mile based on results for other porsches posted in the garage and on EVAlbum.

For a series pack:
Energy = S*C*V

with S = 48 cells
C = 180 amp hr cell capacity
and V = 3.2

I get 27650 watt hours.

If I multiply pack energy by 80% dod, and divide by 250 watt hours/mile, I estimate 88 mile range.

This safely meets my minimum range requirement of 60 mile, and my goal of 100 miles could be feasible at lower speeds (62 MPH) or with more cells (55).

These calculations assume a lot (like level terrain, constant velocity without starts and stops, low friction losses, etc) and I'm only considering then as a general guideline.
 
#4 ·
The 911 is a great choice of car! I'll admit my bias, I have one that I have converted (actually am converting). The 2.7 motor had issues, so you can get those a bit cheaper. I found one with a blown motor but very good condition otherwise. The rear seats are pretty small and don't have seat belts (at least for my old one). 1977+ is nice because they were fully galvanized and much less rust prone. The 912 is basically the same car and much cheaper.

Here are a few details on mine:

http://ExplodingDinosaurs.com
 
#7 ·
The 911 is a great choice of car! I'll admit my bias, I have one that I have converted (actually am converting). The 2.7 motor had issues, so you can get those a bit cheaper. I found one with a blown motor but very good condition otherwise. The rear seats are pretty small and don't have seat belts (at least for my old one). 1977+ is nice because they were fully galvanized and much less rust prone. The 912 is basically the same car and much cheaper.

Here are a few details on mine:

http://ExplodingDinosaurs.com
I love the shape and style of the 911, and I agree on the rust protection. The plan is to be a daily driver, and while we don't have salt on the road, we do get 37 inches of rain a year. If I could get one for $10,000 in good shape I would have to do it.
 
#8 ·
I'd love a 911, but budget gave me a 944. If you go that way get the 85.5+ the interior is just so much nicer. The 944 is still a nice car, and nice to work on (once the gas stuff is gone) not a single rusted bolt, many lightweight parts. Plenty of original and after market support for parts/upgrades. The transmission from a Turbo gives you nicer ratio's to use the high torque of an electric motor (assuming 1000A controller), as well as being a bit beefier to handle that torque long term. I'm using an A123 pack and it will all be in the rear, but there is plenty of room up front if you went with a larger prismatic pack and had to split it front/rear.
 
#10 ·
It will be a 911 afterall. I put a deposit on one today after work. I'll pick it up tomorrow. It is a 1983 SC and the condition was very nice. Service records going back over the last 40,000 miles.
 

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#11 ·
On the 100 mile range, you have a good chance of getting better than 0.13 w-h/mile per pound of vehicle weight so for a 2200 lb vehicle you'd need 280 w-h.
Does that sound plausible?

And I can always use more [valid] data like that below\/

four wheeled electric vehicles
w-h/mile lbs w-h/mile-lb.. notes
217 .......2723 0.080 ............tesla roadster
275 .......4800 0.057 ...............truck
225
240
265
290 .......2020 0.144
300
310
320 .......3000 0.107
325
161 .......1250 0.129
400

3/4ths of the vehicles sampled did better than
312.5 w-h/mile
and better than
0.129 w-h/mile-lb

half the vehicles weighed between
3000
and
2020
 
#14 ·
100 mile range at what speed? I would guess to get that range at 60 mph and 80% DoD, no heater, no AC, you would need around a 32kWh pack. If you use the motor/controller dt suggested, you could use a 178V pack of 180Ah CALB to get the required kWh (the Soliton1 takes up to 340V I think) and limit the MOTOR voltage in the controller sw to about 160 - 170V (limit suggested by Jim Husted: http://www.diyelectriccar.com/forums/showpost.php?p=19666&postcount=4) to protect against arcing brushes etc. Provided of course you can find room for 55 cells in the car and the money to pay for them.:D
 
#16 ·
100 mile range at what speed? I would guess to get that range at 60 mph and 80% DoD, no heater, no AC, you would need around a 32kWh pack. If you use the motor/controller dt suggested, you could use a 178V pack of 180Ah CALB to get the required kWh (the Soliton1 takes up to 340V I think) and limit the MOTOR voltage in the controller sw to about 160 - 170V (limit suggested by Jim Husted: http://www.diyelectriccar.com/forums/showpost.php?p=19666&postcount=4) to protect against arcing brushes etc. Provided of course you can find room for 55 cells in the car and the money to pay for them.:D
Yes, I agree. Not sure if space or money will be limiting factor.:confused: 60 mile is the need. 100 miles is the want.

My 4 year old daughter loves the car, too. She asked Mommy if we now need to wear helmets when we drop her off at school. Sound like someone has been watching too many episodes of "Top Gear" on Netflix.
 
#17 ·
Something you will seriously want to do before doing ANYTHING to the car is to fix ALL of the 12v systems so they work perfectly. Since this is a relatively new car (unlike my 1975 914), you *shouldn't* have rust issues, but that should be looked for as well.

Take it to a Preferred Porsche Specialist for a very thorough checkout. You will find things you don't really want to know, but should.

As for the batteries, I second the recommendation to go higher in voltage - but keep it below 200v - there aren't many parts available to handle higher voltage (I'm all too aware of that - my pack is 370v).

Cheers,
Peter
 
#19 ·
After 10 years, I'm finally able to begin my electric car conversion. My goals are 0-60 MPH in < 8 seconds, 100 mile range (60 is an absolute min) at 80% dod, >80 mph top speed, and 4 seats.

I've narrowed the donor car decision down to two: Porsche 944 or Porsche 911/912. I would prefer the 911, but not at the price they seem to be selling for in my area, $14 -20 k USD (1978-1989). The 944 goes for between $1,000 - $5,000 (1983-1987).

For components I don't think I will stray too far from what a lot of people have been doing:
9 inch Warp - keeping the clutch and flywheel
Soliton Jr, or Soliton1
56 cells at 130 aH CALB or 48 cells at 180 aH
Manzanita 20 - The idea of long recharging times (12 hours) doesn't bother me

Battery monitoring and instrumentation - not selected yet

I'm thinking that the batteries will be the system bottleneck and any money I can squeeze from the bugdet should go there. Not sure how many will fit without messing up the weight distribution too much.
Having to charge on the road for a long time will bother you I am sure. BAD decision on the charger. A 914 would be a much better donor car and a lot cheaoer than a 912/911.
 
#20 ·
How is the charger a bad choice if you don't know what charging station/electrical outlets are available? The PFC20 can max out a normal plug, if that is all that is available bigger helps how??

And for the car how is a 914 better than a 911? I can't stand the look of a 914, so I would never convert one, it's personal choice. Others don't like the 944 so they would never convert one. The best car for "you" is the car you will enjoy driving for the next decade or so, it could be a Bug, 911, 914, hummer or anything that fits you needs and wants.

If you have constructive input, like the transmission of a 911/912 won't last or shift or something related to an EV conversion then it may be useful to suggest one car over another, but it is very clear that the "dream car" is a 911 and unsupported comments about a 914 being better just don't seem to provide worthwhile input.

You may have valid points, but back them up and explain your reasoning, why is the charger a bad choice? What's wrong with a 911?
 
#22 · (Edited)
Why such the negative chip on your shoulder all the time! You seriously need to lighten up. You take everything as if someone is assaulting you, you're always ready to attack.

He asked some fairly simple questions on WHY you made the comments you did so the poster and others in this threat know why you made those comments.
 
#29 ·
I would argue that a simple PFC with 'normal' 110v plug is 'better' for several reasons:

- a properly sized battery pack won't leave you stranded in your daily travels, so the whole concept of quick charge on a public plug is a red herring benefitting only the manufacturers of the charging stations.

- a regular 110v plug allows a (slow) charge ANYWHERE

- most people's garages and outside outlets have only 15 amp 110v service anyway, so why pay double to put in a 220v high amp charger? The overnight charge will get ya a good 15kwhr.... enough to get *most* people their sub-50 mile daily needs.


....ok, ok, if you are driving OVER 50 miles a day, you probably need a higher capacity charger to get enough kWhr on board overnight. But I would still maintain that you'd be more likely to find a 110v outlet *somewhere* for an emergency charge than you are to have a J charge station handy.
I think, like many things, this depends on how/where you drive. Myself I think a 110V charger is useless anywhere but charging at home over night, or maybe at someone's house if you are staying there for a couple hours or more and just need to add 10 miles worth or so. If you only have an hour or so to charge it isn't going to help you much. I sometimes drive to a nearby town 60 miles round trip, return home in the afternoon then charge to drive another 30 miles a bit later. Or, drive to that town, charge in an RV park for 1 1/2 hr from a 240VAC/50A outlet while I walk to a nearby restaurant and eat breakfast, then continue on to my destination and have enough to get back home with about 30% SoC. Most of the time I charge at home over night at 7 to 10A, so a 120V charger would work fine, but the other times it would not.

I am thinking of upgrading to the new Curtis controller next year that is supposed to be about 160-170V max, so I can add 12-13 more cells and have about 100 mile range at 60 mph. If I do, I also plan to go to a 8 or 10kW charger - maybe valerun's. I could then charge at say 45A for an hour at the RV park adding 45Ah and drive to South Lake Tahoe to hike or mountain bike, and back home. So depends on how/where you drive.
 
#30 ·
Generally, you can't say one choice is better than another without considering the use case. If you need to quick charge, then the PFC 20 is a bad choice. I don't think I will need to, but I will think it over again before making a purchase. I will almost always have 12 hours of charge time per day and I have a 240 volt outlet already in the garage. So I need to select a charger that can charge a 180 V, 180 amp-hr pack in 12 hours. I may move up to the PFC30, but first I will have to do some math.

As for the 914, I have seen many nice conversions, and they make great donors. I need 4 seats, so it wouldn't work for me. The 911 is more attractive to me. My second choice was a 944, which would have been a lot less costly. I would have been happy with the 944, but the 911 is the right car for me once I found one in my budget. I think I can make it into a decent electric car that will make me very happy.

I want comments, criticisms, design reviews, opinions on my planning for this project. I don't want to buy too many components more than once. That's why I'm posting here. The most useful posts for me give an explaination of why something may be a problem.
 
#32 · (Edited)
Generally, you can't say one choice is better than another without considering the use case. If you need to quick charge, then the PFC 20 is a bad choice. I don't think I will need to, but I will think it over again before making a purchase. I will almost always have 12 hours of charge time per day and I have a 240 volt outlet already in the garage. So I need to select a charger that can charge a 180 V, 180 amp-hr pack in 12 hours. I may move up to the PFC30, but first I will have to do some math.

As for the 914, I have seen many nice conversions, and they make great donors. I need 4 seats, so it wouldn't work for me. The 911 is more attractive to me. My second choice was a 944, which would have been a lot less costly. I would have been happy with the 944, but the 911 is the right car for me once I found one in my budget. I think I can make it into a decent electric car that will make me very happy.


I want comments, criticisms, design reviews, opinions on my planning for this project. I don't want to buy too many components more than once. That's why I'm posting here. The most useful posts for me give an explaination of why something may be a problem.
You didnt tell me you needed 4 seats. I wouldnt do the 944, resale value is real bad, and motor goes in front. Stick with a 912 which will be more reasonable and will be re sellable. I have done many of most Porsche models as well as VW's. My students did a 944 and cant sell it. One suggestion is, when selecting chargers,etc. always try to design the car to resemble the production cars in every aspect. The more corners you cut due to price will bite you on the ass. A 220v charger with a L1772 recepticle would be a good choice as you will be able to use a public charging station if needed without a bunch of cable adaptyers. Install a 220vac charging station in your garage, either designing your own, or buy one off the shelf from Home depot with additional features. Within time, houses with the charging stations will become standard, have more value for reasale and work a lot better at charging than the retrofits some are using today. We should look to the future when designing a EV and selecting components with less regard to cost.
 
#31 ·
Elcon PFC2500 to PFC5000 ($650-1600). Dual voltage. For instance, the PFC5000 will output the full 5kw on 230VAC, or 2200kw on 115VAC. Of course, the 5kw charger is bigger than pure 2kw charger. Just a possible alternative...
 
#33 · (Edited)
Whatever your vehicle ends up weighing, every thousand pounds of vehicle weight will cost you ~37 w-h/mile.
With a correlation coefficient of only +0.6 the relationship is not too strong but as I get more data this should improve.
The formula is
wh/mile = [(veh wt in lbs) x .0369] + 151
and it's based on the few data points below.

wh/m...veh wt....notes
217 2723 tesla roadster
275 4800 truck
340 3354 Nissan Leaf
320 3000 ptcruisin
161 1250

0.0369 =slope
151 =intercept
0.64 =correlation coefficient

Some of these data points may be 'outliers' and so should be discarded but time will tell. I did graph them and the scatter didn't look too bad.
 
#36 ·
Whatever your vehicle ends up weighing, every thousand pounds of vehicle weight will cost you ~37 w-h/mile.
1000lbs = 37Wh/mile eh?

Not even close to accurate. My motorcycle, about 110wh/mile and it was ~400lbs , which is about average for most motorcycles. I think it's not just y = mx. There's energy lost in transmission, energy to overcome static friction and a bit of kinetic friction via tires.....vehicle speed..... motor efficiency.... all of those vary widely based on vehicle type.

It's not as simple as you want to make it.

Many people have done the calcs before, including myself. Look up EVCalculator and put some info in there. It's straightforward, but it's not only weight, it's cross sectional area, drag coeff, etc. Maybe look at those some more before you release your theories.
 
#38 ·
Ok, misunderstood. His wording was confusing.

But maybe don't make the assumption that it works with all "vehicles" because the equation doesn't work for light vehicles very well.

It just can't be a blanket equation.

Sent from my SGH-I897 using Tapatalk
 
#42 · (Edited)
Man, that thing goes down to the level of individual molecules! :D

I was going to have more of a summary: how much hp to move a car at walking speed and to achieve top speed and what accel curve is expected with a constant torque and an inverse torque speed curve, using the '5252' equation.
Assuming a default drive wheel radius of 11" I'll try to fit my results to published data and I'll certainly check my results against this worksheet.
Maybe I can get some of my numbers within 10% of other data, some of the time.

Muchas gracias. . .:)
 
#41 ·
Wow, that even fits my Buggy pretty well, putting it at 192 watt hours per mile. I could easily do that in city traffic if I enjoyed the Zilla a little less. Usually the Buggy is a terminal outlier on any energy use figures because at 1100 lb. it just doesn't fit any normal definition of a car.

However, that good number isn't going to happen on the freeway unless someone gets out and pushes.
Yes, the data will fit any car at some speed since energy/mile varies so greatly with vehicle speed. The correlation coefficient is low because it is a sample from a population with large variance, consisting of a wide range of speeds, drag coeff/area, weight, and measurement method/accuracy. Means of small samples from such a population will vary considerably. If you take many small samples from such a population you can find one that gives the result you want to "prove" your point and throw the rest out. Larger samples will have lower standard error, and their means will have less variability.
 
#45 · (Edited)
Does this prelim calc. contradict anything you have in mind so far?

80.00 >Enter min top speed in mph
117.33 =calc'd speed, ft/sec
11.00 >Enter drive wheel radius in inches
2.88 =calc'd wheel circumference in feet
2444.62 =calc'd max wheel rpm
5000.00 >Enter top speed of motor in rpm
2.05 =calc'd max gear reduction

8.00 >Enter max seconds for 0-60 mph
88.00 =calc'd accel, ft/sec
2700.00 >Enter vehicle mass in lbs.
83.85 =calc'd mass in slugs
11.00 =calc'd avg min acceleration, ft/sec^2
922.36 =calc'd min force on ground to achieve this, lbs
845.50 =calc'd total wheel torque, lb-ft
422.75 =calc'd per wheel torque, lb-ft
1833.46 =calc'd wheel rpm at 60 mph
295.16 =calc'd total hp at the wheels

I have a formula for almost any speed torque curve so you can input any values at any point and get any outputs. The idea is to work backward from the specs to a speed/torque of some existing motor.
Basically I can model graphs like this
http://www.thunderstruck-ev.com/Manuals/AC15_Torque.png
With formulas you can see what needs to be changed and how much effect a change will have, as opposed to a spreadsheet clunking through values.
Since the max hp for this type of curve is reached at below 5000 rpm the 295 hp is understated for the motor's rated hp.
 
#50 ·
Does this prelim calc. contradict anything you have in mind so far?

80.00 >Enter min top speed in mph
117.33 =calc'd speed, ft/sec
11.00 >Enter drive wheel radius in inches
2.88 =calc'd wheel circumference in feet
2444.62 =calc'd max wheel rpm
5000.00 >Enter top speed of motor in rpm
2.05 =calc'd max gear reduction

8.00 >Enter max seconds for 0-60 mph
88.00 =calc'd accel, ft/sec
2700.00 >Enter vehicle mass in lbs.
83.85 =calc'd mass in slugs
11.00 =calc'd avg min acceleration, ft/sec^2
922.36 =calc'd min force on ground to achieve this, lbs
845.50 =calc'd total wheel torque, lb-ft
422.75 =calc'd per wheel torque, lb-ft
1833.46 =calc'd wheel rpm at 60 mph
295.16 =calc'd total hp at the wheels

I have a formula for almost any speed torque curve so you can input any values at any point and get any outputs. The idea is to work backward from the specs to a speed/torque of some existing motor.
Basically I can model graphs like this
http://www.thunderstruck-ev.com/Manuals/AC15_Torque.png
With formulas you can see what needs to be changed and how much effect a change will have, as opposed to a spreadsheet clunking through values.
Since the max hp for this type of curve is reached at below 5000 rpm the 295 hp is understated for the motor's rated hp.
The circumference of an 11 inch radius wheel is 5.76 feet (2*pi*R = C). This increases the max gear reduction to 4.6:1. In 5th I have a ratio of 3.18, and a wheel radius of 12.43 inches, so at 5000 motor RPM I would be doing 116 MPH (if the system were capable).

And then in the second grouping of calculations, the second line should be "calc'd velocity." This one is just an error in the label, the math is OK.

The 11 ft/sec^2 acceleration is what would be required for constant acceleration. Not sure how the rest of the calculations are computed, or how the motor torque/power curves are applied. Do you have the formulae for the last 4 calculated expressions? I don't think the acceleration is constant, or that you want to use this as a minimum over the run. I think you would need to do some kind of integration. I'm not saying this is what you have done, I just don't follow yet.
 
#46 ·
I have a question that will likely advertise my ignorance, but here goes anyway. I'm reading a drive wheel radius of 11.00 inches. Is that correct? :eek:

The best I can tell, the radius is from the center of the hub to the outer edge of the tire. Using my tire sizing calculator and entering the tire size for a stock 1990 Miata {185/60-14}, that diameter works out to be 22.74", so the radius is 11.37". I would've thought the Porsche tire would've been bigger than that.
 
#47 ·
My Porsche has 225/50R16 tires on the drive wheels. That works out to 12.4 inch radius. I probably should measure to see if this is close. I'm still working on the math for the rest of the calcs Rational posted, but the gear ratio is going to be different. The fifth gear ratio is 0.8214 and the final drive ratio is 3.875, so ratio of input to output on the gearbox is 3.183.

From the link tomofreno provided - http://www.diyelectriccar.com/forum...-charts-ev-performance-spreadsheet-41565.html (zip at the bottom of the first post)- the 0-60 time is estimated to be 6.5 seconds. Seems rather quick.
 
#49 ·
Maxvtol, I posted the file here. The wheels are forged aluminum. I estimated 15 lbs wheels + 22 for the tire, times 4 wheels = 148 lbs. I got the gear ratios out of the owners manual. I didn't change too many of the other values. Perhaps I was too optimistic with the total mass of the conversion. Adding just 200 lbs predicts a 0-60 time of 7.3 seconds. I would be curious to see if you would recommend any changes to the parameters.
 

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#52 · (Edited)
Parameters look pretty good. I think you might have too much wheel spin in 1st to get the ET that low. I've toyed improvements to the spreadsheet that take into account wheelspin and voltage drop under load. I've also put in dropdown boxes in a couple of spots and included where the drive wheels are, and F/R weight ratio to help with figuring out wheelspin.

I've put in your values with the new attached spreadsheet and come up with about 8.45 sec 0-60 starting in second gear, which is pretty good, I think. You could toy around with the F/R weight ratios and throttle settings if you start in 1st and see what happens.

You going to be able to get 56 batteries in there?
 

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#54 · (Edited)
I don't think the acceleration is constant...
It's usually not. Even if you can maintain the motor at its peak torque throughout the acceleration by shifting, the wheel torque drops when you shift up. It would only be about constant if you could maintain peak motor torque all the way through, 0 to 60 mph, without shifting. Even then, the drag force is increasing with speed and the applied force is constant with constant torque, so acceleration will still decrease some.

Hey Joe, thanks for the updated spreadsheet!
 
#57 ·
Hey Joe, thanks for the updated spreadsheet!
Your welcome, Tom. I hope it can be useful. Joey's car seemed to be close to mine, so I thought I'd post here.

OP specified 48 * 180ah or 56 *130ah.

I have a better plan. 80 * 100ah. Which is ~25kWh at nominal.

Unfortunately I can't input this into your spreadsheet as it thinks the voltage is too high
48 of the 180ah appears to be better, which would make sense since it's ~ 27kWh at nominal and the 56 of the 130ah is ~23kWh nominal. (If you maintain similar C rating between the batteries choices durning acceleration). And yes, the spreadsheet can't handle higher battery voltages than motor voltages.

My 2c would be 48 of the 180ah. Fewer connections, more range, better acceleration.

I put more battery choices in the attached spreadsheet.
 

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#55 · (Edited)
Building a spreadsheet, part 1

starting with a vehicle with drive wheel radius r and with drive wheel torque TQ
you calc. the force f that the wheel exerts on the ground
TQ = r(f) so f=TQ/r
0.5 >Enter r in feet
30 >Enter TQ in lb-ft
60 =calc'd f in pounds

you already have f so given the vehicle mass m you can calc. a.
f=ma, so a = f/m
100 >Enter m in slugs
60 >Enter f in lbs
0.6 =calc'd a in ft/sec^2

taking your rolling resistance as 1% of the vehicle weight
the force opposing the f from above is
1 >Enter 'slugs of rolling resistance'
32.2 =calc'd pounds of rolling resistance
so your new f is
27.8 =calc'd new, net f
so your new a is
0.278 =calc'd new a

right off the bat, v = at so t = v/a
for this vehicle, the t to reach a speed can be calc'd
0.3 >Enter a in ft/sec^2
88 >Enter desired v in ft/sec
293.3333333 =calc'd t in sec

since x [distance] = 0.5at^2


This is lousy and will not get better so a redesign is in order.

0.9 >Enter r in feet
60 >Enter TQ in lb-ft
66.66666667 =calc'd f in pounds

30 >Enter m in slugs
67 >Enter f in lbs
2.233333333 =calc'd a in ft/sec^2

0.3 >Enter 'slugs of rolling resistance'
9.66 =calc'd pounds of rolling resistance
so your new f is
57.00666667 =calc'd new, net f
so your new a is
1.900222222 =calc'd new a

1.9 >Enter a in ft/sec^2
88 >Enter desired v in ft/sec
46.31578947 =calc'd t in sec

1.9 >Enter a
46 >Enter t
2010.2 =calc'd distance in feet

How many seconds for this mythical vehicle to
go 1320 feet?
how fast will it be going at this point?

Since I make mistakes it would be wise of me at this point to ask forum members for their take on this.

Except
for the one member who is on my ignore list. Regrettably, nothing you have to say to me is welcome. The bad news is that if he/she ever becomes a moderator then the ignore list becomes moot for me and I'll have to come up with a more permanent solution.

BTW, this forum bolds my stuff for no reason that I can see.

MKS is superior but the US uses English. BTW, a spacecraft failed because some engineer didn't make the conversion.

In the interest of squeezing as much info out of what you have at the moment, here's some more.

For a constant TQ the hp curve will be a ramp
that goes up linearly with RPM.

For TQ = 60 lb-ft and RPM = 3000
the peak hp is
34.27265804
This looks like a triangle with height h
34 and base b of 3000.
The average hp would be the height of a rectangle
with the same area.
So 0.5bh equals an 'area' of 51000 so h of the rectangle is 17 hp
17 hp for 46 seconds is 430,000 ft-lbs
is 162 w-h.

You've gone about 0.4 miles so you can now figure w-h/mile at about 400
Your veh weighs about 1000 lbs so you've got 0.4 w-h/mile-lb

I'm not to motivated to check this yet because it's basic physics, and I'd like to debug my eventual incremental spreadsheet at the very end. It's probably the "not invented here" factor that is governing my motivation at the moment. That, and the programming experience I've had.
 
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