Hello to All,
KilowattA798@cs.com wrote:
> With 2 zillas and the power to feed them from the lithium pack the 4700lb chevy with all the good suspension work should run 8.64 seconds in the qt.mi. at 157mph.I would not expect this in your 1st run out but after 5-8 passes. These #s come from the VERY predicitable Speedworld horsepower calc. on their site, but do not include my multipiler. With that multiplier in the equa.you will run 8.48 in the qt.mi. What a difference a little NITRO makes!!!! Dennis Berube
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Whoa, Dennis’ ET predictions for the Monster Garage project Chevy sure seem ‘optimistic’! I respect Dennis, he’s a great competitor, a friend, and quite a character, too! He’s still the top dog as far as having the quickest electric ET, too. However, as excited I am about the rad one week conversion that friends Rudman and Lawless did, these guys, the ones that helped build the thing, both feel low to mid 13’s are more realistic, certainly not 12’s….it’s too heavy and there’s just not enough raw power to get the job done.
To investigate Dennis’ predictions, I’ve done some research of my own, and offer the findings as balance to what I feel is a wild prediction of performance I personally, don’t think is even close to being correct…no offense is intended. I have tried very hard to keep past predictions of performance as accurate as possible, whether it’s my own car, or someone else’s. As an example, when Matt Graham first contacted me more than a year ago about his proposed twin motor electric Nissan 240SX, I predicted it would run easy 14’s, and that it could get into the 13s’….he ran a 14.2 first time out. I’ve been pretty much right on the mark with my car all along, too.
OK, here we go…..I plugged in a known performance spec list from my own White Zombie, at three different 1/4 calculator sites. The first one, Simple Horsepower Calculator, is at:
http://www.dsm.org/tools/calchp.htm
This site has open boxes where you can enter data:
(1) Vehicle Weight (including driver weight)
(2) 1/4 Mile ET
(3) 1/4 Mile Trap Speed
I entered my accurate data of 12.151 for the ET and 106.25 for the mph, and my estimated data of 2550 lbs. for vehicle (2350 lbs. & 200 lb. driver) weight. Historically, I’ve been within 50 lbs. on my electric conversion weights. The calculator came up with this:
(1) Based on the ET, 281 hp
(2) Based on the mph, 239 hp
Since drag racing EVs typically have a lower top end speed as does a gasser running the same ET, I tend to lean toward the mph based hp levels.
The second site, Horsepower Calculator, is at:
http://www.s-series.org/htm/calc/hpcalc.htm
This site has open boxes where you can enter data:
(1) Known 1/4 mile ET
(2) Vehicle Weight (including driver weight)
(3) 1/4 Mile MPH
(4) 60 ft. Time
Note that this site adds a box for the 60 ft. time, which I feel really improves the accuracy.
I entered the same accurate data of 12.151 for the ET, 106.25 for the mph, and added 1.59 for a 60 ft. time, plus the estimated data of 2550 lbs. for vehicle (2350 lbs. & 200 lb. driver) weight. The calculator came up with this:
(1) RWHP (rear wheel horsepower) from entered ET of 280.93 hp
(2) RWHP from MPH of 238.71 hp
(4) Break hp from ET of 337.116 hp
(5) Break hp from MPH of 286.452 hp
The third calculator site, National Driveline, is at:
http://www.nationaldrivetrain.com/calcs/dragcalc.html
This site has open boxes where you can enter data:
(1) Vehicle Weight (including driver weight)
(2) Vehicle hp
(3) RPM through the finish line
(4) Tire diameter
I used the same 2550 lbs. vehicle weight, and since the 239 hp from the first site and the 238.71 hp that the second site were pretty much identical, I rounded it to 240 hp, 6900 rpm from our tach data and calculations using the rear end ratio and tire diameter, and 24 inches as the current diameter of the Goodyear Drag Radials (before we burned them down, these were actually 24.3 inch tires). The third performance calculator came up with this:
(1) 1/4 Mile ET of 12.23
(2) 1/4 Mile Top End Speed of 106.52 mph
(3) Ideal Gear Ratio of 4.63
(4) 1/8 Mile ET of 7.79 seconds
This data is surprisingly accurate. Compare the results to what the car actually did:
Predicted ET of 12.23….actual ET of 12.151
Predicted top end speed of 106.52 mph….actual top end speed of 106.25 mph
Suggested ideal gear ratio of 4.63….actual gear ratio is 4:57
Predicted 1/8 mile ET of 7.79 seconds….actual ET of 7.602 mph
OK, now that I’ve demonstrated how accurate the three sites are with a known vehicle’s performance, let’s now use the first site, Simple Horsepower Calculator, the one that seems to have nailed my car’s hp pretty darn well, and see how Dennis’ predictions of 8.48 seconds and 157 mph come out:
Again, this site has open boxes where you can enter data:
(1) Vehicle Weight (including driver weight)
(2) 1/4 Mile ET
(3) 1/4 Mile Trap Speed
I entered the Chevy’s 4900 lb. estimated weight (4700 lbs. + 200 lb. driver) and Dennis’ 8.48 ET and the 157 mpg figures. The calculator came up with these outrageous results:
(1) Based on the ET, 1588 hp!!
(2) Based on the mph, 1480 hp!!
I’m told the Chevy’s incredible battery pack can deliver 3800 amps at around 170 volts, or a whopping 646 kw!
Now, though that’s a huge amount of delivered power, in the real world of DC motors at BIG amps, a best case scenario is figuring 75% efficiency, so for every hp generated (746 watts) the motors will actually suck 1000 watts….this comes in at 646 hp, tops.
OK Dennis, where do you come up with at the least, 1480 hp? Where do you get 157 mph? Where on earth, do you get 8.48 seconds?
At the National Drivetrain site, I entered the Chevy’s 4900 lb. estimated weight (4700 lbs. + 200 lb. driver) and the more realistic 646 hp figure, plus 5000 rpm and 26 inch tires. The calculator came up with these results:
(1) 1/4 Mile ET of 10.98
(2) 1/4 Mile Top End Speed of 119.18 mph
(3) Ideal Gear Ratio of 3.25
(4) 1/8 Mile ET of 7 seconds
Note, that if I’m off on the rpm or the tire size, it still doesn’t change the ET or the MPH figures. Of course, a scorching 10.98 would make us all proud! However, an 11 second ET is a far cry from a predicted 8.48 seconds! Likewise, the 119 mph is a far cry from the predicted 157 mph! If the battery pack can’t actually deliver the full 3800 amps, or if at that level the voltage falls below 170, or if both are on the optimistic side of things, then the actual horsepower will be less. With 3600 amps from twin Zilla 1800 amp controllers and keeping the pack sag to 170 volts, it comes in at 612 kw, and the car would run an 11.17 @ 117 mph. Still killer, but approaching 3 seconds slower and a full 40 mph shy of Dennis’ predictions.
Dennis, care to correct me on any of this? Did you slip up with your figures, or were you merely using Neutrino logic and cold fusion calculations here?
See Ya…..John Wayland