Battery assist can occur at any speed and at any load. The battery pack is pretty limited in power, so you get seconds, not minutes of battery assist.

You can get battery assist at less than 99% load.
You can get battery assist just when you reach and try to exceed 99% load.
You can be at 99% load and not get any battery assist.

99% load simply means that all the power being created at the given RPM is being used. In many ways, 99% is a good thing. You are getting the maximum power per drop of gas.

Also, since this car has a continuously variable transmission, it purposely keeps the RPM as low as conditions allow. In a standard 4-speed transmission, the RPM is governed by gear ratio... so most of the time, a traditional car is below 99%.... meaning the car is running at xxxx RPM due to gear ratio, but not all the power available is being used.

99% load used to bug me. But with the eCVT, it makes sense, and is a good thing. Your best bet is probably keeping it below 99%, but close to 99%. It kind of means you are being 99% efficient.

I do not find the load feature very useful.

I use water temp, RPM, MPG, and MPH... as it is VERY useful to know when you are at 39 MPH, since EV is only possible at 39 and below, and the needle is not very good to tell when you are at exactly 39 mph.

 

John, thanks for the info on assist. I keep forgetting how little capacity the EV battery really has, which means it couldn't be of much use on a sustained grade.

I too have settled on water temp, RPM, MPG, and MPH on the SG. I prefer the digital readout for mph and rpm over the analog gauges.

 

I'll try Don

If you want to understand what I'm talking about, it may require experience driving an under powered cars where you floored it, but it slowly starts to gain speed. The power you got was all that was there, some refer this to WOT (wide open throttle) in the carb system of long ago vehicles. In this day of electronically controlled fuel injection, you really don't have a WOT, but you do have the same maximun acceleration abilities of the engine.

The reason I am concerned with max load is MPG. The only way to reduce MPG, is to reduce max load of the ICE which is 99% on the SG. This is why I point to load on the SG.

For max MPG, you must accelerate much under 99% load to see the higher MPG readings. Over 99% load, you are in assist and draining the HV battery that has to reduce MPG to recharge the system.

You will get assist throughout acceleration, but once you have used assist to raise the atkinson RPM to handle the complete torque and load, there is no longer a need for assist.

GaryG

 

Gary,

I received my SG II just last week and have been following this thread closely. I'm currently using RPM, MPG, Water Temp, and load. The load seems to run very high for me when accelerating (over 80 a lot and in the 90's as well). What's the best way to keep the load lower? Is it just a matter of holding at the lowest RPM possible to accelerate, or backing of the gas to get to a lower RPM?

BTW, thank you (and others!) on the list. I've been lurking for a month or so and have learned a lot. Now that the temps are back up here in northwest Missouri my last 3 tanks have been running 34.9 to 36.8mpg!

Thanks,

Rick

 

Hi Rick

The first thing to learn and control is RPM. Sounds like your with the program knowing to keep load as low as you can. Sometimes, that's not possible in traffic, but keep trying no matter what when you can.

What I do, and I've posted this many times, is use the torque curve for acceleration. The Atkinson cycle engine we have has very little torque at low RPM. This is why your seeing a high load at low RPM's, and I wanted to point Load as an important factor in mileage. I used the torque information to get the most power for the buck. I use 1,800 rpm's for acceleration when possible, and jump to 2,400 rpm's as my second choice up to 3,000 rpm's for fast and busy traffic. It is very rare that I use 3,000 to 3,500rpm's because that is a dead area with no increase in torque. It is important to hold the engine RPM and let the CVT (computer) adjust the speed till you reach that speed and back off the pedal for KAM fuel trim to take over.

Here is a photo of the torque curve that I'm talking about:

http://www.cleanmpg.com/photos/showp...to/864/cat/508

Enjoy

GaryG

 

Gary,

Thanks for the link to the torque curve ... a picture always helps! I'd read about the flat ranges, but it's easy to see (especially the 300-3500 range) that your not getting any help from the increased RPM in those ranges). Just one question: What is "KAM"?

Thanks,

Rick

 

KAM stands for keep alive memory and is part of the PCM (Powertrain Control Module). The PCM learns engine RPM and Load at every level of operation and stores this in KAM tables that are referenced by engine speed and load. In other words, instead of constantly changing the fuel trim which may reduce MPG, the PCM learns the right fuel trim corrections for the RPM and Load and works off that stored data in KAM. Short term fuel trim can be +/-25% of the perfect fuel mixture of "stoichiometric" which is 14.7:1. Short term fuel trim corrections can be learned by the PCM as Long term fuel trim corrections and stored in KAM. One reason this is done is to allow the engine to operate with this data in Open Or Closed Loop and provide the right fuel mixture for that RPM and Load.

During warm-up, you are in open loop till the CAT goes what they call lights-off at about 550F. This is when the PCM go into closed loop and uses stored data in KAM for a delivered fuel mixture by the PCM at those set RPM's and Loads. Now, when you get to those higher speeds and remove a lot of the Load and RPM with drafting, the fuel trim is stored for that speed. When you loose that draft, you can maintain speed and RPM running on a leaner fuel mixture (remember short term fuel trim can be +/-25%) for a good distance. You can now see this with your SG because of no MPG changes in your average. You will lose this lean mixture when you begin to change speeds or go up overpasses etc.

Long term Fuel Trim will change depending on the operating conditions, ambient air temperature, and fuel quality. With regard to fuel quality, ethanol or alcohol are oxygenates and screw up the air/fuel mixtures to run much richer than normal. When you use this stuff, your mileage will drop considerable. If you start cleaning this crap out by filling with good pure 87 octane, it may be a good idea to reset KAM to the default settings and start from there again. To reset KAM, just remove the 12V battery ground cable for a minimum of 5 minutes. Adaptive learning content such as idle speed, refueling event and fuel trim will all go to the default settings.

Hope everyone understands KAM better now. Most of this information came from the '05 FEH PCM/ED manual.

GaryG

 

Gary,

I recently found a station that sells pure gasoline (everything else around here is e10). I have already seen about a 15% increase in MPG after 1.5 tanks... do you think I should still reset KAM as you describe above? Or will it continue to get better all on its own?

 

Brady, it took me 3 tanks to clear the KAM damage in the past, so your at least half way there. If your already seeing a 15% increase, don't reset KAM IMO. It should get back to normal on its own like mine did. I stopped buying Citgo gas period here in South Florida, but it was not for Political reasons.

Most if not all higher test gas has oxygenates, so always use pure 87 octane for the best MPG when you can.