Spy photos of Porsche testing 911 GT3 Hybrid for the streets

Pretty cool. I have no doubt it is for performance over economy, but still it is a chance for an automaker to support lighter/larger capacity energy storage solutions.

The obvious benefits I see, are by using regen and disc braking, the driver can brake much much later in a turn, then using the batteries along with the motor accelerate out of the curve faster than with an ICE only. If there is any economical effect, then in longer races there would be less pitstops.

Something I have wondered about before is why a CVT isn't used in racing? I would think with the right logic behind it, the CVT could keep the power at a maximum no matter what is going on. In a race, this would be a huge advantage over traditional gearings. Does anybody know why they aren't used, or are they and I just don't know about it?!

 

CVT..??

First, the HSD system's CVT is not really a traditional CVT, it is really a PSD, Power Split Device (analog computer summing machine).

But the bottom line is that neither version is anywhere close to having the capability of handling the kind of power needed for a Porsche 911, or the like.

 

"..might find its way into road legal.."

The advantage to Porsche's flywheel energy storage device is that it can absorb and disperse energy in much heavier surges than can any electric battery system known today. Road-going vehicles so rarely need/require that level of sudden braking that the expense, and technology, of the flywheel system would be wasted.

But I would early love to drive one a few trips around the Daytona track.

 

A manual transmission gearbox basically provides a direct engine-to-wheels gearing system when you select a gear and engage the clutch, which minimizes power losses in the drivetrain.

An automatic transmission has a lot of power loss in the fluid-coupling torque converter.

A belt-drive CVT transmission uses friction belts and variable-diameter pulleys as well as a fluid-coupling torque converter, so in addition to the power losses in the torque converter there is also the question of friction losses in the belt and pulleys as well as durability.

The Prius PSD is a completely different animal by the way-- It is permanently-engaged gears with a fixed gear ratio, not belts and pulleys like a true CVT. Given a properly-engineered planetary gear system that can handle the torque from both a huge electric motor and a powerful gasoline engine, I think a PSD can work as a racing drive system (I think Toyota actually put the PSD into the FT-HS, which is a performance hybrid sports car concept.)

That's my limited understanding anyway.

 

I don't think the LS600h uses "the" PSD, nor the GSh.

For the LS600h to make use of the standard HSD PSD design you would need a >200HP 18,000 RPM electric motor, assuming a 3:1 "split" between the ICE and the opposite summing "machine" input.

 

The LS600h uses three PSDs in its transmission. File:THS evol 3.png - Wikipedia, the free encyclopedia

In that schematic, S = Center Sun Gear, C = Planetary Gear Carrier (middle planet gears), and R = outer ring gear. Each S-C-R arrangement is a PSD.

As is true with any of the variants of Toyota's PSD-based hybrid drive system, the LS600h system is also essentially direct gearing to the drive wheels using fixed gear ratios, with no fluid-coupling torque converter but a system of permanently-engaged gears.

 

Ah good point. Definately have done that before. It is almost second nature, and I completely forgot how that would be negated with the CVT... I think you hit the nail on the head, this is probably the main reason. I am sure all mechanical problems could be solved, but the technique is not something people would want to give up.

However, perhaps a manual CVT? Something where instead of a gear changer, you have a lever. Move the lever, and change the positioning of the tranny belt. So you could essentially manually control an infinite amount of gears, while allowing them to be fixed. Perhaps a couple preset points to simulate fixed gears...

 

Didn't Honda include a "paddle shifter" with their current-generation Insight (which has a belt CVT)?

I remember that Nissan did in fact program "lurches" into their CVTs to simulate "gear shifting" like you would experience in an automatic multispeed transmission car too.

As far as the Porsche goes... From the scant descriptions floating around the web, it seems to be using a variant of the KERS system that was developed for Formula 1. Is that really a "hybrid" system (as in hybrid electric vehicles)?

 

Honda has 7 virtual gears in the insight that locks in a gear ratio on the cvt. They also have a real manual on the cr-z. The honda trick won't work as easily on the hsd, as there isn't a linear relationship between engine rpm and speed. The hsd could simulate engine drag and torque with virtual gear ratio though.

 

Hugh? I thought the 5.0L V8 in Lexus' 600h has 400hp ... even before you throw in the electric motors' hp.

Whoops!
Should'a read more posts.