wwest — I'm pretty sure that in 'B' mode the rate of NiMH battery charging is increased relative to the rate of battery charging in 'D' mode. It's certainly not zero, as indicated by the arrow from the wheels to the battery. By a higher "rate" I mean that the regeneration amperage going to the battery is higher when coasting in 'B' mode than when coasting at the same speed in 'D' mode. The braking due to the regeneration will thus be greater in 'B' mode too. The higher-rpm fuel-cut spinning of the ICE in 'B mode compared with 'D' mode will also apply more engine braking. The combination of these two effects is a substantial increase in deceleration in 'B.'

Stan

 

Mine seems to kick in the generator at a high rpm to slow the car in the B position. I noticed on a rather long steep grade the generator stays in till about 40 mph. It;s then the engine takes over and assist in slowing the car up to 50 or so.

I could see this on the scan gauge and I do remember the gallons per hour were low but not at idle. One I reached about 50 mph the gph read something like .75 up from a .25 at idle.

 

rburt07 — I may be misunderstanding your post, but the RPM figure read by ScanGauge is the ICE's, not the generator's, rpm. Coasting at the same road speed, say 100 km/h (~63 mph), the ICE's rpm is much higher in 'B' than in 'D' — something like 3000 rpm versus 1000 rpm. This is why the amount of engine braking is higher in 'B.' The noise you hear is from the ICE not the generator. If you have the updated SG, the GPH reading should be 0 during fuel-cut. If it's not 0, then either SG is in error, you haven't calibrated SG's TPS setting for proper fuel-cut detection, or the ICE is actually idling and not in fuel-cut. If you have the updated SG, the correct TPS setting to use for proper fuel-cut detection is 16 (or possibly 17). After setting it to one of these numbers (I'd suggest starting with 16), it should register fuel-cut correctly. Since SG's default TPS setting is 24, it will definitely not correctly register fuel-cut at its default setting.

Stan

 

spl - My only reference to the scan gauge was talking about gallons per hour. I had the LOD readout on but paid no attention to it.

You bet, I also saw he engine's rpm way up to about 3000 rpm, when I shifted out of B to Drive. For the next mile the road was not as steep and I eased on the brakes to hold my speed.

I use the LOD and RPM mainly for climbing hills. I do understand the rpm shown on the SC is for the ICE.

I could not hear the generator or engine during the B mode. That was due to the increasing speed and wind as the car moved faster coming from the top of the mountain.

I read somewhere the generator spins up lots faster in the B mode to brake he car. Something like 10,000 is the max rpm at about 40/45 miles per hour. Then the engine braking takes over. Could be the engine as you say may be in fuel cut with no ignition, so I don't see any engine readings on the scan gauge. Till the rpm gets up to about 2500 when in the brake mode.

I'm using the updated scan gauge I sent in for the update over a year ago. I will have to check for the proper TPS readings.

 

rburt07 — Here's a formula that relates the speeds of the three items {MG1 (Ns, rpm), ICE (Ne, rpm), Road Speed (RS, km/h or m p h)}:

Ns = 3.60 Ne - 78.372 RS [for RS in km/h] = 3.60 Ne - 126.13 RS [for RS in m p h]

If you know any two of these three quantities, you can use this formula to solve for the third quantity. So, for example:

• If the engine is idling (Ne=1000) and you are stationary (RS=0), then MG1 is spinning at 3600 rpm.
• If the engine is idling (Ne=1000) and you are moving at 40 m p h (RS=40 m p h), then MG1 is spinning at -1445 rpm; e.g., coasting in fuel-cut in 'D' mode.
• If the engine is idling (Ne=1000) and you are moving at 60 m p h (RS=60 m p h), then MG1 is spinning at -3968 rpm; e.g., coasting in fuel-cut in 'D' mode.
• If the engine is spinning at Ne=3000 while coasting in fuel-cut in 'B' mode, and you are moving at 40 m p h (RS=40 m p h), then MG1 is spinning at -1445 rpm.

You can easily calculate additional examples for yourself. You will find that MG1 is spinning at nowhere near 10 000 rpm at any normal speeds — it reaches a speed of -10 899 rpm at the car's governed speed limit of 185 km/h (~115 m p h) if the ICE is idling at 1000 rpm. By the way, the MGs are specified by Toyota for speeds up to 14 000 rpm.

Stan

 

I always thought it was complex, I never knew it was that simple!

 

spl- You are correct. I wrote 10,000 rpm as I thought I had read someone else's post months ago saying that was it's max rpm. I looked in my bookmarks and this digram of the power split device tells the story.

It looks to me like 5590 is a safe max rpm for MG1. MG1 at 6500 would be the red line max according to this page.

http://eahart.com/prius/psd/

 

Today I got around to adjusting the fuel-cut on the Scan Gauge. I had mine updated a while back to the Scan Gauge II with X-Gauge.

Mine was set to the default, 24. I changed it to 16 then pressed Done. Still the GPH drops to .04 when the engine is off. I may have some other setting not correct. Engine Size = 2.4, Engine Type - Hybrid,
Tank Size = 17 gal, Fuel Type = Gas.

Friday I may call Linear Logic and talk to a tech about the .04 at engine cut. Could be a program problem. The .04 did not show up till the update.

Thanks Stan for the advice. I had overlooked the fuel-cut setting as the other older scan gauge I had did not have that setting.