Prius "launch control"

[miscrms]

Ok, so I got to test out a theory last night. After learning about the trick of stepping on the gas and brake at the same time to run the ICE and charge the battery, the natural question arose, what happens if you take your foot off the brake

I can now say the answer is it accelerates surprisingly quickly To my poorly calibrated butt dyno it seemed considerably quicker than a standard takeoff. I would guess this is not a great thing to do to the car, and needless to says its awful for your mileage, but it was kind of cool

Would be interesting to see if this method actually resulted in any improvement in 0-60 or 1/4 mile times. It could be helpful in two ways, one the ICE is all spun up and ready to go, and two bringing the battery up to near full ensures you'll have plenty of electric assist. As long as MG2 isn't spinning backwards there shouldn't be any less electric power contributed, but you should be getting more from the ICE sooner. Hmm... when is the drag strip open again

Rob

[Qlara]

It may launch the Prius quicker like you observed, but this doesn't sound healthy to the Hybrid System though. Will the MG1 overheat?

You can do the same 'Brake-Torque' technique to a conventional car with Auto-Tranny too. It also helps to launch the car slightly quicker. Again, not too good for the car, may overheat the Auto tranny.

[patsparks]

Half a secont to overcome the "lag" you feel on a conventional start wouldn't hurt you would think, no worse than a hill start or doing it to test emissions. The throttle wont open fully unless the computer says it can.

Might be good to hit the loud pedal 50% at the top of the christmas tree and drop the brake on the last yellow. Going to check for the date of the next street meet at Adelaide INternational Raceway now!

[Presto]

How about putting into the idle test mode where it idles the ICE. With the ICE already running, that should reduce the initial delay off the line without waiting for the electric motor to turn the ICE.

[David Beale]

I'm not sure what you've seen, but Pearl will not increase the cold idle RPM when you press the accelerator while you have your foot on the brake (in "D"). So I don't see how this could reduce acceleration time.

Now if you are in "P" Pearl will allow the engine RPM to rev up. But I saw no "jerk" or improved acceleration when I put it in "D" and released the brake. I was forcing Pearl to warm up quicker BTW, while waiting for a long light to change. Pearl will warm up to 50C (coolant temp) doing this in only about 3 min, whereas if you just let the car idle it only gets to 40C and that takes at least 5 min. Ambient temp was -20C or lower.

[V8Cobrakid]

that method didn't seem to help much when i did auto crossing. It did get the battery nice and full which helped around the track. the only drawback is that it heats up the inverters and battery. after a while. (3 or 4 runs around the track) you start to take a performance hit.

that mode you mentioned is called drivetrain maitenence mode. It won't make a difference on acceleration unless you're wheels are slipping. it did help around the track because while i cornered the old oem tires slid.. which the car would brake.. so free spinning helped.

[fmvs]

Commonly done with diesels. Gets the turbo spinning and thus avoids the acceleration lag as boost pressure is created.

With the Prius the electric motor has power right off the line (relatively high torque rating) but the low torque ICE (remember your physics? high torque translates to high horse power at low RPM,s) needs to get wound up to produce good power. That's why your power launch works. Jeff