Scangauge vs Energy screen

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#11

06-22-2009, 08:14 AM

Big-Foot

Currency-to-hydrocarbons

Join Date: Sep 2006

Location: Minneapolis, MN

Posts: 343

Re: Scangauge vs Energy screen

Quote:

Originally Posted by rburt07

What does the Cutoff function do? (from Linear Logic)
Some vehicles will turn the fuel injectors off when coasting down. We sense this with the open/closed loop indicator and the throttle position. We have to know if the throttle is opened or closed but the minimum value for it is rarely 0. The Cutoff is the value the throttle has to be below in order to indicate a fuel cutoff and show 0 fuel flow.
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First you read your TPS (throttle position) at idle. (engine warm) Take the number 14? and add 2 to it. Set the fuel cut-off number to 16. This is per linear logic.

Some other forms say add 1 to the TPS for the cutoff number. The scan gauge II should come with the fuel cut-off default set to 24 for most vehicles.

The default is right for most vehicles, but it can be adjusted for different situations. If set to "0" it disables this method of fuel cutoff sensing.

Thanks for posting this...

According to my SGII - My TPS is a consistent 15 (1.5v) at idle setting and coasting and has never read lower. The TPS does not update very quickly nor is it linear at all to the amount of pressure put on the pedal as I can easily vary my throttle pressure without impacting the TPS reading on the SGII. Certainly the only way the HSD system knows when to increase output to the traction motor is via the TPS (unless there is yet another sensor on the throttle pedal - which I believe there is although I've not been under the dash yet)..

Fuel cutoff -
In my past experiences with firmware programming for ECU's - the accepted norm was to cut fuel flow to 0% at speeds above 30mph and TPS reading of 1.5v. This was to curb exhaust detonation (sending raw fuel into a decelerating enging which may make it into the exhaust system as either a liquid or excessively rich mixture). If you've ever been along side of or driving a louder car that had a carburetor - they will make a series of muffled pops while decelerating from a higher rate of speed. That's Exhaust Detonation.

#12

07-29-2009, 12:02 AM

cwerdna

Pretty Darn Active Enthusiast

Join Date: Feb 2008

Posts: 269

Re: Scangauge vs Energy screen

Quote:

Originally Posted by rickkop

cwerdna said in a previous post "No arrows does not mean the ICE is off". I agree because I've seen this condition. So, if the ICE isn't off and in fact is running with no arrows leaving the ICE, you are coasting or at a stop, and your battery is not fully charged, then what would be the reason for the ICE to be running? With these conditions wouldn't it make sense to be charging the battery? The same scenario with the ICE cold, produces an arrow charging the battery. Not a problem but I must be missing something. Rick

FWIW, today in my Prius, when I was in stage 1a (see PDF at http://priuschat.com/forums/knowledg...rence-aid.html) w/a cold ICE running, IGN definitely at -10, no arrows in any direction on the display, and I saw BTA values, IIRC somewhere between -8 and -2 amps (don't recall exact numbers but it was NOT 0). The negative refers to HV battery charging.

Covnersely, when during the glide phase (dead banding == no arrows) of pulse and glide, I can see a draw from the battery: BTA being ~5 to 10 amps, IIRC. If you sit idle w/the headlights and AC off, BTA is ~1.2 to 2 amps. Turning on the headlights and esp. the AC makes BTA go way up.

BTA and other interesting values are from XGuages on my SGII. See the Prius section of http://www.cleanmpg.com/forums/showthread.php?t=11742.

FWIW, ~3 years ago, Toyota Sunnyvale held a hybrid seminar (owners were invited) given by a pretty knowledgable Toyota rep and he even said sometimes the "display lies". Many got a chuckle out of that.

I think the above is a case of the display lying. Maybe you have some of the above going on w/your TCH?

Last edited by cwerdna; 07-29-2009 at 12:05 AM.