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Discussion Starter #1
Has anyone tried modifying their prius for PERFORMANCE? Either the gas engine or the electro-motors. There are probably any number of things you can do. The gas engine is basically a variant of the ECHO engine. I'm sure there is an aftermarket in parts for that.

I'd be interested in hearing about any mods that have been attempted.
 

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The Prius has been optimized for efficiency and emissions reduction, not for performance, although it provides a fairly decent one. And also for reliability, like any other Toyota, but there's a specific item here that needed special attention : the HV battery. Engineering is always about compromises; if you try to gain somewhere you will loose somewhere else...

If performance is your requirement number one then you should probably not consider the Prius.
 

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ken1784 said:
http://response.jp/issue/2004/0112/article56897_1.images/60572.html
If you could hack the computers and beat them, you'll be a hero.
The hacking that you refer to is common place in the aftermarket for other cars. It's called chipping. Seeing as the engine in the Prius is basically a detuned ECHO engine,...which is also available in the Scion platform, I can't imagine it being that difficult to do.

As far as I can tell the Prius powerplant differs from the ECHO only in that it has higher compression pistons, a different camshaft (probably with less lift) and a different ECU. The cam and the ECHO ECU should be available off the shelf from Toyota. The question is whether the ECHO cam will cause valve interference problems with the higher deck on the Prius pistons. My guess is that it will so you'd need to dig into the bottom end on the engine as well to replace the pistons...at which point given costs you may as well just do a swap with an ECHO longblock.

I'd be interested if anyone has tried this. I'm gathering that it has not been attempted.
 

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The biggest accessible gains from software reprogramming alone might come from removing some of the safety/longevity limits on the battery. Panasonic say it's rated for 1,300W/kg, but Toyota have programmed the battery management to only allow about 750 W/kg - presumably to enhance the lifespan of the battery. If you allowed the batteries to deplete at their maximum rated power, you could get about 37kW out of the battery, as opposed to about 21kW just now. That would mean an extra 21bhp, and as far as I can tell, the 50kW motor should be able to handle it.

Having said all that though, there is a good chance that working the battery harder will shorten it's useful life somewhat! :wink:
 

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Just had another thought along the same lines that could see you safely past 225 bhp.

You could add another two batteries in parallel to the existing one, using the same type as already in place. Once the supply issues are out of the way, these could possibly be picked up from Mr T for around $1,000 each.

Then you'd have to seriously uprate the motor, to take about 120kW max, (rasertech have this sussed) and reprogram the battery management to allow each battery to run at peak output of 1,300W/kg.

Total available battery power would then be 3 * 37kW, or about 150bhp. Add the 75bhp or so available from the ICE and you've got a temporarily available peak power or 225bhp for a weight disadvantage of around 100 kilos. Should see a 0-60 of around 5.9s.
 

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R50 - Though chipping may be common in other cars, to my knowledge, it hasn't been done in the Prius. Toyota made it particularly hard to do, probably as part of the deal to get the best emission ratings from various gov't agencies (such as the EPA). You can't even easily drop in an Echo engine because the electronically controlled throttle requires the engine computer to talk to the hybrid computer and nobody's even figured out how that protocol works (though progress is finally being made on that front after 3 years).

clett - Rather than hooking the extra batteries in parallel to the existing battery and needing to upgrade the main motor (and the transmission and drive train), it would probably be easier to add a grid charged set of batteries powering a pair of motors connected to the rear wheels. Just add a switch that dumps full power to these motors whenever the accelerator pedal is fully depressed. That would give you your extra burst of neck snapping power when you want it without draining the batteries much during normal driving. Then just charge them back up overnight for tomorrow's fun. It would be far easier to implement and you can add a lot more power at the back wheels than at the already powered front wheels. Be sure to take extra care balancing the power to the two back wheels.
 

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RSnyder - you're right, that is a better idea! You'd then have one of the world's first plug-in hybrids, which to my mind are the best compromise we have at the moment by having the refuelling and range practicality of petrol, while at the same time having the cost and environmental benefits of electric.

You could do it a-la AC-propulsion, and stick together a whole load of LG-Chem 18650 lithium ion batteries. These have a power density (once assembled and including casings, control electronics etc) of about 500W/kg, so an extra shove of around 100bhp would require a pack weighing ~150kg. Storage would equate to around 21kWh, or an all-electric range (at ordinary speeds!) of about 100 miles before the ICE needed to kick in. 100 miles of full performance stealth mode, anyone? Oh, cost of these are currently around 250/kWh, so you're looking at 5,250 for the batteries alone!
 

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clett said:
RSnyder - you're right, that is a better idea! ...

<snip>

... so you're looking at 5,250 for the batteries alone!
Plus the cost of installing a drive train to the rear wheels! And the VSC and traction control would not know that the rear wheels were being powered!

I love the idea of a gridable 100-mile EV range. But I'd much rather see the car designed that way from the ground up. Maybe for the next major model revision around 2010????
 

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1967 50/2 said:
The hacking that you refer to is common place in the aftermarket for other cars. It's called chipping.
You mention only about the engine ECU.
I stated "computerS".
http://john1701a.com/prius/presentation ... ion_35.htm
It'll be limited improvement to modify the engine ECU only.
There are another ECU's like HV ECU, Battery ECU and others.
You can't beat Racing Prius by modiying only the engine ECU.

For those who are looking for 4WD Prius, I believe you had better think about Toyota Highlander or Lexus RX400h. They have 270HP and enough performance with reasonable price.

Ken
 

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Discussion Starter #11
ken1784

You can't beat Racing Prius by modiying only the engine ECU.

Ken
Not interested in that at all.

What I am interested is how the Prius can be modified for the street. From the answers above, it would sound as if there are several options with the electrical motor, and PERHAPS with the engine as well.
 

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Interested in opposite

Well, I'm interested in "chipping" the Prius to make it "perform" worse. I would like to be able to put the pedal down a reasonable amount without the ICE always kicking in. This has to do mostly with the region in which I live (Western Michigan). What we have here are numerous 55 and 70 mph speed zones which are broken by widely spaced stops. This is also a flat area, which isn't really ideal for the Prius (I consistently get better economy in rolling hills). The Prius seems designed to work best in true city driving. It *assumes* that it can't just go ahead and use up a bunch of the stored battery power during a single acceleration because you'll be doing it again and again. This isn't true here in West Michigan, where we're frequently accelerating from a stop right back up to highway speeds. If the Prius would just let me do that as much as possible on just the electrics I'm sure my economy would improve considerably. The battery would have plenty of time to recharge because it is likely going to be 5 to 10 miles before I hit that next stop sign...

The acceleration would be fine on the just electric. Go to an empty parking lot, put the Prius in reverse and hit the gas. See how fast you hit 25mph? But getting to 25 mph in drive without the ICE kicking in, is almost impossible (unless you're willing to create a traffic hazard).
 

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Re: Interested in opposite

Daniel said:
I love the idea of a gridable 100-mile EV range. But I'd much rather see the car designed that way from the ground up. Maybe for the next major model revision around 2010????[\quote]

Hey, so would I, but this thread was asking about the possibilities for modifying an existing Prius.

Panjandrum said:
The Prius seems designed to work best in true city driving. It *assumes* that it can't just go ahead and use up a bunch of the stored battery power during a single acceleration because you'll be doing it again and again.
The Prius actually seems to work best in "country" driving with long duration drives at around 40 MPH with rolling hills and little change in speed.

Anyway, you're assumption about what it assumes is not likely to be correct. :) Moderate to heavy acceleration is the worst possible time to use the battery precisely because it's the best time to use the gas engine. There's also the secondary issue of battery longevity.
 

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Re: Interested in opposite

Moderate to heavy acceleration is the worst possible time to use the battery precisely because it's the best time to use the gas engine.

Is this really so? Seems to me that the traction motor, with its highest torque available from rest, is best employed to assist in acceleration when ICE torque is low; this in the absence of progressive gearing to step up engine torque. Conversely, the ICE is best used to maintain cruising speed when power and torque requirements are low. Is this not the engineering design principle involved here?

A further note: is it not the case that ICE efficiency is greatest at high RPMs, such as at sustained highway cruising speeds (55-65 mph)?
 

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You're forgetting that at low speeds, most of the ICE power gets to the wheels via the generator/motor path. Thus you get the best of both worlds, efficient power from the ICE under high load (from the generator, not from the wheels), and high torque from the motor. At low wheel speeds but moderate to high acceleration, the ICE really does run at high RPM (and so does MG1, acting as a generator). So it really does run efficiently.

Prius|Genius
 

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Computer adaptability?

What an interesting thread!

It occurs to me that a vehicle like the Prius could conceivably have more than one performance profile (switchable) depending on the type of terrain/driver habits/preferences. Since is is drive by wire anyway, why not have standard/low acceleration but max economy/high acceleration but lower economy/flatland/rolling hills profiles available?

Or possibly have it adapt to your driving style?

Any of these would be better than chipping, and might not be that big a jump.
 

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More on driving habits

As you can probably tell from my posts, I have a relatively heavy foot (my wife gets, on average, 3mpg more from the Prius than I do!). I think this is because I've also always been a (classic) Bug fan. Yeah, I know, the simplest of vehicles (bug) and the most advanced (prius). I'm like that; my favorite audio device is my iPod, my second favorite is my Sonora crank phonograph! There is beauty in engineering marvels of both amazing complexity (prius) and their sublime simplicity (bug). Anyway, in the classic bugs, you accelerate foot-to-the floor through the gears a lot of the time. It doesn't seem to hurt the bug drive-train at all to do this because they are so underpowered and durable. The down side is that when I drive other vehicles, I tend to retain that heavy foot.

Now, I understand there is a debate about which is most efficient, using the battery or using the ICE under heavy acceleration, but what I'm saying here is that all I want/wish to try is for the vehicle to provide, say, 8 to 10 seconds off-the-line of electric-only power. You can't tell me that's all that taxing on the batteries. I've driven this puppy a lot (2003 model, already at 42,000 miles!) I know how much power those batteries can provide (a surprising amount, I'll post some of my driving experiences in another thread soon). I need say 8 to 10 seconds of heavy electric-only acceleration, then I'll be "nearly" back to highway speeds. Then I'll be *at* those speeds for probably another 10 minutes before I have to stop again. That "EV" switch mod for the '04 sounds GREAT. I hope they include that in the '05 from the factory.

My guess is that Toyota has the ICE turn on so quickly so that the car is reasonably speedy off the line. I would prefer an option to be a little less speedy and a little (maybe a lot) more efficient.

Also, heavy acceleration is the WORST time to use ANY ICE in any vehicle. That's when the vehicle has to throw tons of extra fuel to the engine to provide that extra power. It's the BEST time to use that high-torque electric. Once up to speed, the ICE is using far less fuel than it is under heavy acceleration.
 

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Would EV mode really be much more efficient?

Question for Robert:

If, say, EV mode were available, like in Europe, would it really be more efficient for short around-town trips than the standard Prius mix, or not? More battery cycling might impact battery lifetime.

It sounds like keeping the engine coolant hot (in the 2004 at least) is part of the great low emissions overall performance.

It does seem to a naive observer that there are possible future real-world efficiency improvements available if Toyota did some sophisticated computer power management tweaks, using the computer to monitor and improve performance in different driving situations.
 

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Hi Mel,

In general, I tend to trust the decisions of the Toyota engineers. However, since they only designed one car, they probably aimed at what they consider to be the most likely driving scenarios. It also looks like they specifically tuned the car to the emissions tests (aimed for the benchmarks). So certainly there will be some fraction of drivers who could do a fair amount better with a different design.

I would guess that the EV mode would have the most payback for trips that were mostly downhill, at least at the start. For example if you lived on a hill and the first three miles were downhill but the speed limits were 40 MPH or less. It could also have decent payback for short (1-2 mile) mostly flat but low speed trips. In this case you would probably only want to use EV every other time. I'm not as sure about this case though, it depends a bit on how willing the 2004 computers are to run the engine hard when the battery is low. The 2001-2003 models weren't very willing to do this at all, so this would not be a good use of EV mode on those models.

Basically, you want to use EV mode to transfer low load use of the gas engine to periods when the load is higher (or can be made higher with cooperation from the computers).
 
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