HCH1 UK Manual Lean Burn - Page 3

samwichse · 02-10-2013, 08:42 AM

I can enter lean burn up to exactly 65 mph. Any higher even by a tiny bit and it will not enter lean burn. Obviously, I can't necessarily maintain speed in lean burn mode at 65mph, it's terrain dependent.

The other quirk is that I've not hit the upper limit for lean burn speed, as you can go faster than 65mph in lean burn and accelerate up to over 70 without it kicking off (imagine the case of cresting a hill on the interstate at ~62mph, then pressing the throttle lightly on the long downslope, catching lean burn and hitting 75 at the bottom still in LB).

My ECM number is in the spreadsheet, and I got the latest software update done as well.

Sam

**honda-dave** · 02-11-2013, 01:27 PM

Everything you have said Sam rings true with what I experience, Apart from mine Is 45MPH.
The only time I can get it at higher speed is like you said is when the car picks up momentum on its own IE: downhill.

retepsnikrep · 02-11-2013, 02:15 PM

I'm going to try a gizmo which modifies the VSS speed sensor signal on the wire going into the ecm. This will make 65mph actual speed equivalent to 45mph at the ecm input. Beacause the LB cut off is so sharp i think it must be VSS related. If we only modify the signal going into the ecm then we may not cause knock on problems with the speedo/gauges which IIRC is also feed by the VSS. Time for another 12F683 pic project!

I want to try this before I start swapping ecm's and cat's / sensors etc.

I'll try to knock something up later in the week thur/friday.
I'm away for a couple of days for Mother in laws funeral

If the LB cut off is controlled by the VSS then we might be able to extend the LB speed window on all cars

The mod will affect the IMAC&C speed related functions as they come via the ecm so we might have to add compensation for that.

**honda-dave** · 02-11-2013, 02:21 PM

Sorry to you both for your loss.
I'm up for a another PIC project when you ready.

retepsnikrep · 02-11-2013, 02:59 PM

Just a thought can you all check if LB works in 4th and cuts off at exactly the same speed on your cars?

If it does then it's not rpm related as that would be a higher rpm than when in 5th, and that supports the theory it may be VSS related.

**honda-dave** · 02-11-2013, 05:19 PM

no problem will give it a go tomorrow.

Aqua · 02-12-2013, 02:53 AM

My cvt wouldn't hold LB in 2 gear pass 2,500 rpm for 50mph. Could it also be engine load (vacuum map sensor) and rpm both together ?
Because You can short shift ( heavy load) and still be in LB if your barely pressing the throttle, and be out of LB and deep into heavy load if you press harder. And still you haven't reach 40mph or 2,500 rpm. They is also the risk of burn valves on heavy load, 25-1 (impossible mixture) short shifting,wind up hill, etc all kick it out of LB.
Pete also try my mods. I've got mod that are top mpg add ons I promise you will get into the 90 mpg soon.
I just found a way for double your coasting distance by eliminating disc brake drag Your car will feel like it's has just 4 wheel on, coast for 2-3 blocks this will help your LB but you find it's just better to gain speed and put in neutral
I have uploaded pictures I will start a new how to thread tomorrow.

**honda-dave** · 02-12-2013, 01:42 PM

Just tried the lean burn test: 3rd gear 2850rpm, coolant temp 84c, 45mph lean burn cut out.
Second test: 3rd gear 2850rpm, coolant temp 68c, 45mph lean burn cut out.
Both tests also conducted whilst in 5th gear at 1900rpm, 45mph lean burn cut out.
the only difference was the second test in 5th gear was the coolant temp was 71c.
Just to add: both sets of tests were done on a flat road and the ambient outside temp was 2c.

retepsnikrep · 02-12-2013, 03:39 PM

That seems to strongly suggest the lean burn cut off is VSS controlled.
Good news for our potential gizmo. May be transferable to the G1 Insight as well.
Extending the lean burn speed window won't be a magic bullet but it will be very interesting and a probable improvement.
Might look at some code later. I think the VSS is a 12v line but will have to check

Might be 5v which is a little simpler.

retepsnikrep · 02-13-2013, 03:30 PM

I've written some code to test tomorrow for the Pic 12F683 VSS mod device.

65mph In from the VSS will equal 45.5mph Out to the ECM in the test code.

The device also has a jumper pin which will enable the VSS to pass thru unmolested when the pin is grounded.

I'll breadboard it tomorrow and see what happens.
If it works I'll post the simple schematic.