2004 Speed Week Prius project sent to junkyard in Texas

[JimL]

This news popped up on a number of car-stuff websites.  It seems sad that the car was "eliminated" from the museum property.  The websites describing the mods for the build have many "errors".  Since I was part of the build team, I think it will be ok to tell some of the "back story".

The engine was basically a stock Prius engine, except we ran using the Echo long block.  That means we ran the engine in traditional "Otto" cycle, and not in "Atkinson" cycle.  This gave a slight power boost, but most importantly, added another 1500 RPM available (6500 versus 5000 RPM).  We had the Echo fuel management chip in the Prius computer.

The inverter/converter used an Estima (hybrid van from Japan market) booster, which gave us 10% more torque across a wider speed range.  Keep in mind that the stock battery was running out of "juice" about half-way through the measured mile...if we did our push and launch just right.  After the battery fell to 40%, electric assist was reduced and engine power was partially diverted to work on battery recharging.   Our best runs showed about the same speed at "mile entry" and "mile exit", with about 5 mph peak in the middle of that timed mile.

We added an ice water tank in the right front floor area, to help cool the "pots" for as long as possible during a run.  We ran two electric water pumps in series...one at the tank, and the other at the inverter.  This allowed us to "force charge" the battery by holding on the brakes and flooring the engine throttle for about 10 minutes prior to each run.  We could completely melt 40 pounds of ice, each pass.

We had custom final drive gears made, for 3.14:1 ratio (not 3.2 as claimed in various postings).  During initial testing, before we began the "hard build" I found that the transition from "sine wave" to "square wave" showed a positive increase in torque for about the next 500 motor RPM.  On a normal Prius, this transition occurs about 62-65 MPH and gives a little better passing performance.  The change from "sine" to "square" is necessary because the 3-phase is computer generated and smoothing/curving the wave gets beyond speed capability of the "pots" that do the hard work.   I planned the re-gear to give the best possible "jump" off the push bar, if that became necessary.  Working with Car & Driver, we found that my Tundra push truck could not push the Prius beyond 92 mph.  So....now you know why I chose 3.14:1.  As we learned on the salt, there was no need to push the car as far, or fast, because the battery capacity was just enough to make the runs.

That "sine wave" to "square wave" issue is a problem for fast and powerful electric cars on the salt.  At Speedweek 2004, I was asked to look at the Buckeye project tires for a blistering concern.  I measured the blister spacing and found it was exactly the distance between "square wave" hits, with the gearing they used for 300+ MPH.  Shifting from "sine" to "square" makes a very sharp torque event for these type of projects.  Within a small group of us that have worked on unusual projects, we have brainstormed the idea of running through a conventional torque converter.  I don't know of anyone that has tried it.  Now...back to the Prius story....

In order to lower the car, sufficiently, we ran into the problem of front axle shaft angles.  In order to solve that problem, we had to "clock" the entire e-motor/transaxle 28 degrees (counter-clockwise as viewed from drivers' side).  That was as far as we could go without getting the right axle into the engine block.  The attached photo shows how far we had to "notch" the unibody, and move the inner fenders as high as possible.  We had to plan for various tire sizes (up to 28") because this whole project was "unbroken ground".  This brings us to the "tire solution" we discovered at SW 2004.

We started our runs using 24" tires at all four corners.  This gave us our 128 MPH runs, which was 6 MPH faster than Toyota engineers in Japan thought possible.  Keep in mind that hybrid vehicles monitor front and rear wheel speed carefully, in order to keep the vehicle safe in a panic stop or accident avoidance maneuver.  This is super important because that heavy electric motor is geared solidly to the wheels.  During ABS braking, the motor computer has to ADD power as necessary to prevent the wheels from unexpectedly locking up.  If you ever stop that massive "flywheel" attached to the front wheels, it will be a lot of skidding and sliding before the wheels might start rolling again.

Understanding this logic system, we installed 26" tires on the front only.  This made the hybrid control system do all possible to get those front wheels caught up to the rears.  Thats how we got past 130 MPH, and eventually beyond 135 MPH during our last run.

It was a long time ago, and I have probably forgot things, but I hope you get a little enjoyment out of this story.  They can't fire me for telling this....I retired 13 years ago!

[sabat]

Fascinating work Jim, thanks for sharing. I love the nitty-gritty details that go into an effort like this. -Dean

[kiwi belly tank]

Interesting read! So what was the Echo engine? Or was that the Eco engine?
  Sid.

[hotschue]

Jim,
After setting the record I met your group on the parking lot of the Rainbow Hotel. I had to ask how did you do it... I was totally impressed with your achievement. One of your group stepped forward, and in typical racer style, said it was a stock Prius, the only modification was in the flywheel.  Walked away even more impressed...have shared that story many times....thank you for your post!!

[Rex Schimmer]

Jim,
As always a great story from someone that was there! The sine wave/square wave part was really interesting. I always read your post as your background and knowledge really is valuable. I still have your book on the building of your roadster with a Toyota banger in it, you sent it to me while I was building my track roadster.

Rex

[Speed Limit 1000]

Interesting read! So what was the Echo engine? Or was that the Eco engine?
  Sid.

I think this is what he was talking about.

https://www.ultimatespecs.com/car-specs/Toyota/27864/Toyota-Echo-Echo.html

[kiwi belly tank]

Thanks, I wondered if that's what it was!
  Sid.

[JimL]

Yes...the Echo and Prius were basically the same except cams and pistons.  The Prius will not run below about 1200-1500 rpm (it has no idle) and runs out of breath at 5000 or so.  Atkinson cycle is efficient, but in a narrower range than Otto.  Many of the variable valve timing engines (these days) can drift into Atkinson cycle while you are cruising at light throttle.  Switching to smaller bore/longer stroke engines has made intermittent Atkinson easier to manage.

Interesting thought about salt flats racing....manufacturers have learned they can make more power than needed, using fewer cylinders and less RPM.  That hot rod Corolla GR is a 3-cylinder turbo that can run 25 pounds of boost on the street, and still get traction out of the corners.  This is not that new a deal....

I was sitting with Ed Iskendarian at Sema in 2004 and he told me about Model A engines he built for dirt track racing.  They ran harder and came off the corners better than anybody else.  He said he made them with a crankshaft that was front two pistons up, when the back two were down.  He ground a cam to work with it, in order to get better cylinder fill.  The more even spacing of combustion events helped traction coming out of broadslides.

I told him about Honda GP motorcycle racing, when they finally switched to 2-strokes.  Everyone else were running V4 or Square 4 2-strokes.  Honda ran a V3, and could set it up to fire all 3 cylinders together for tighter, slower tracks.  They won world championships until they got bored of it and quit.  Ed understood the concept exactly and really enjoyed the comparison.

Every time we think we are getting smart, we find out somebody already did it 100 years ago!!

P.S.  Almost forgot to mention one very strange difference between Prius engine and Echo engine.  VVTi engines have a "locking pin" that fixes the camshaft at retard position when you shut it off.  When you start your engine, the pin does not release until oil pressure is high enough to push it back.  This is done to prevent a lot of scary sounding rattling when the customer starts their engine.  The Prius engine is "spun up" by Motor Generator No.1 (there is no starter) and so no combustion events occur until the engine is at "normal" operating speed.  For this reason, there is no locking pin.  The pin "release event" would cause bad running during an actual start, and the customer would NOT like the surge events.

[Rex Schimmer]

JimL,
Great story about Isky, but I heard it a little differently. Ed Winfield was the guy that came up with the two up and two down idea and I think Isky did the cams. The  Model Ts only have 2 inlet ports so they are shared by two cylinders, if they are fired in standard banger configuration there is a crank position when both inlet valves are in overlap (open). One has been feeding its cylinder air/fuel but when the other cylinder's intake valve opens, it  has the lowest pressure so the majority of the charge is redirected to that cylinder and the other cylinder, on which the intake valve is closing does not get a full charge In the two up two down configuration the cylinders that are sharing an intake port are 180 deg apart and there is never a case of overlap on the intake valves. Each cylinder gets the full charge from the common inlet port.
Whether it was Winfield or Isky it was some damn good thinking.

Rex

[JimL]

That makes perfect sense.  I was only there to answer questions about the Prius (it was on display in a "Toyota rented" room), and a manager came and told me to sit down with Ed at a table.  He had questions about the Prius...kind of general, but pleasant conversation.  There is more "rest of the story" about that evening.

When we set the car up for display, we had the suspension dropped as used at Speedweek.  When it came time to get the car out of the room, down the hall, and out the doors at the ramp....I was told they wanted it driven out.

I said, "That is a bad idea."  The manager said, "I'll drive it out, you just get it running for me."

I did as I was ordered, and by the time the car was juggled into the hall, the engine had the catalytic converter well lit.

It melted the center of the carpet down to the concrete, all the way to the doors.  Smoke alarms went off, it stunk to high heaven, and I got in my own car and drove home from Las Vegas in the middle of the night.

I never did hear who paid the bill, and I didn't ask.

[jacksoni]

RE: Every time we think we are getting smart, we find out somebody already did it 100 years ago!!

When I was in training (I'm and Ophthalmologist) and somebody reported a new surgical procedure a faculty member said: " They just haven't read the old German literature. Been done years ago" 

Great story on the Prius. Thanks for sharing.