PiP – the Marvelous Mountain Machine

The base of Pike's Peak at Colorodo Springs is at about 6000 ft. So it is about an 8000 ft climb.

The Atkinson design of the ICE in the PiP mitigates a lot of the effects of altitude (or so I have heard). Unlike the Volt, into which GM dropped an engine off the shelf, the ICE for the Prius was designed for the Prius. (Disclaimer: This may well be different for the Gen II Volt.)

 

Oops, early morning brain fart, I was answering on the basis of a regular Prius. The PiP will be able to use regen far longer.

But I stand by the compression ratio and B-mode portions on my post.

The full descent to the gate is far more than that, though the mandatory brake check is only half way down, and the remainder of the descent is less steep.

 

As far as I know, the engine will go all the way up to 10:1 at WOT, but the majority of the time it's operating at much lower effective CRs.

Toyota ZR engine - Wikipedia, the free encyclopedia

Edited b/c of typo in wiki article ("compression" ratio for the hybrid 2ZR is really the expansion ratio)

 

From previous discussions here, it is very clear that cannot happen.

That Wikipedia article mention nothing about this engine's valve closing angle. To get that high compression ratio, the intake valve must close at or very near BDC. However, the VVT-i system in these engines is mechanically limited to closing no earlier than 72 (Gen2) or 61 (Gen3) degrees after BDC. This late closing greatly reduces the possible compression ratio:
compression ratio and spark timing | PriusChat
Can we bring up Power Mode again? | Page 2 | PriusChat

 

Are you sure that the intake valve can't open fully even when VVT-i isn't operating?

 

How could it possibly be shut off, without major mechanical surgery?

If you can invent a wider range adjustment system, at marketable cost, knock yourself out. And reap a bundle selling the rights to it. But do it soon, as plenty of others are already working on the issue.

 

The same way it engaged in older models (just VVT). As far as I know, VVT systems don't always have to be active, and cars can be driven with them disabled.

Putting this another way, the 2ZR-FXE puts out 98hp at 5200rpm, which matches up almost perfectly with the 136hp at 6000rpm of the 2ZR-FE when adjusted for rpm/torque (105ftlbs/128ftlbs)*(5200rpm/6000rpm)*136hp=96hp.

Toyota ZR engine - Wikipedia, the free encyclopedia

If the earliest the valve closed was at 61 degree, I doubt the 2ZR-FXE would make 98hp. The 2ZR-FE probably makes a little more torque due to high load enrichment, but my feeling is that the numbers seem to support VVT-i being off at WOT in the Prius.

Edit - I guess the 2ZR-FE could also have the same 61 degree limit for the numbers to line up well, but if that was the case it would also have the same lower CR, which I don't see it having.

 

The system has been described in multiple past threads, some dating back years before you signed up. In my 6+ years here, I cannot recall any credible information that the intake valves could close any earlier than indicated above. Doing so is simply not within the mechanical capacity of this particular system.

Try reading the links above, and chase back from there.

Why do you have torque in that equation? Shouldn't it be just RPM ratio alone?

I'm taking the lower Prius' lower torque output as being a direct result of the delayed valve closing and reduced air mass and compression ratio. If the valve could close at BDC and get a full air charge, then we'd be asking why that Atkinson engine gets such terrible torque for the same air mass as its Otto sibling.

 

My point isn't that the intake valves close earlier than the literature suggests, it's that the Prius isn't very different (with the exception of cooled EGR instead of a richer mixture at WOT) than a conventional engine at WOT. With that said, the Wikipedia article references a 13:1 compression ratio, which is a typo, and should be the expansion ratio. Both the conventional and Atkinson 2ZR have a compression ratio of ~10:1.

In terms of torque, it should technically be torque at that specific speed, but most stock Toyota FE engines have pretty flat torque curves. But anyhoo, adjustments need to be made for torque unless both engines have roughly the same torque curves.

 

I've long suspected PiP battery capacity may improve real-life MPG in situations like this. On similar tracks around Yosemite and lake Tahoe with 4 people loaded we got low 50s in Gen3. On many mnt passes( Tioga, Monitor, Towne pass out of Death Valley, etc.) it ran out of battery on both way up and way down.

Thanks for sharing I might consider PiP in future just for that. With current gas prices it will be still cheaper not to change it though.

Does anyone know if PiP recharge rate is higher than Gen3? Can you brake harder without using friction brakes?

 

FYI Prius C has 13.5:1 compression ratio

 

PiP highway is rated 49 MPG instead of 48 for regular. Bigger battery back isn't utilized much on the highway. I think it has newer inverter as it wasn't part of the recall.

 

I suspect the conventional engine has a different cam system that can close the valves at BDC, getting a full 1.8 liters of intake displacement, compared to ~1.4-1.5 liters max intake on the Prius. That would account for the max torque difference.
Plus, the conventional engine probably has an expansion ratio of ~10:1, same as its compression ratio. It would seem at a small difference in connecting rod length between conventional and Prius engines would do this, though not the only way to do this.

 

See the many past years of discussions on this. Toyota was labeling that an expansion ratio back when GenIII was released, but later reverted to the more customer-familiar terminology of 'compression ratio'.

 

On fake Atkinson compression and expansion ratio is the same. You posted that 13.5 can't be done and that is what C currently has

 

See the earlier intake valve closing angle graphics. The current Prius system simply cannot get that much on the compression side.

 

I'll look but it is not an actual pressure but compression ratio, which is defined as the volume at the bottom / volume at the top. On real Atkinson the intake and power strokes are physically different, but on fake "modern" they are identical. Thus compression ratio = expansion ratio

 

Then we have a semantic issue, using different definitions.