ECU/EFI adjustments Trail versus HWY

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rmel
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ECU/EFI adjustments Trail versus HWY

Post by rmel »

If your running with EFI, you may be leaving up to 20% of your potential torque on the table.

There is a trade off between fuel economy and power -- basically HWY versus the trail.

After a lot of experimentation, I have finally dialed in a decent recipe -- and yes, I had been
leaving unexploited torque under the Dog house. The fix turns out to be simple, run richer
at low RPM -- better torque and no hesitation.

What I have noticed is that between 1,000 to 2,000 RPM torque was poor with hesitation.
Above 2,000 RPM, nice and smooth. But with the TD Tranie in a 710K, 2,000 RPM is a
race walk not a crawl -- which can be dangerous on step grades with obstacles.

It has bugged me that with 2.7L/EFI, with supposedly more torque across the entire RPM
range, I should be able to crank at a lower RPM than a stock Pinz compensating for the
gearing in the TD tranie -- this hasn't been the case at all. To get there I need to run strong,
at load, below 2,000 RPM.

The fix was simple. Run a richer fuel mix at low RPM, and VERY important -- turn OFF
Closed-Loop operation on the ECU. The target AFR for peak torque is 12:1, for fuel
economy it is 14.7:1 which will be at the expense of power -- up to 25% less.

That did it, smooth and increased Torque from 1,000 to 2,000 and no hesitation.

The ECU's Closed-Loop feature attempts to maintain a Stoichiometric condition in the burn; as
perfect as possible conversion of Octane to CO2+H2O which results in best fuel economy. The ECU
table values set the base-line for the amount of Fuel to inject at a given RPM and Manifold Pressure.
Then Closed-Loop will increase (or decrease) that amount to get as close to 14.7:1 as possible. Most
ECU's limit the amount of tweaking to 10% to 20% of the table value, but that's sufficent to mess things
up. The key point is if Closed-Loop is ON it works hard to get better fuel economy thus defeating best
possible power.

If you had your ECU tuned by someone thinking economy was important, or high RPM is normal
operation you may have less than optimal values set in your tables and you may have Closed-Loop ON.

It was pretty easy for me to tune in AFR as I can monitor AFR and MAP and adjust accordingly.
Looking at AFR going up steep grades. The RPM range of interest is 1,000 to 3,000 RPM. Some ECU's
are very simple to adjust. Ones with 2-dimensional or 3-dimensional tables are a wee bit harder. My
unit is a SDS EM4 which supports an external AFR meter and has a fuel adjustment knob so I can
increase/decrease the baseline amount of Fuel versus RPM on the fly.

For the trail, I will have the fuel adj. knob set +15% for 12:1, and near 0% for a HWY AFR of 13.5:1.
It would be nice to have a switch or programming feature to load a table for trail or HWY which is
not supported on my ECU.

This has made a huge difference in my low end power, you might want to take a look at your setup
if you haven't already.
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
bikmakr
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Re: ECU/EFI adjustments Trail versus HWY

Post by bikmakr »

Great info! Thanks. I've been tuning to achieve 14.7 under most conditions. I had no idea that I should go that rich. I have a Wideband up the tail-pipe as well as narrow-bands on all four cylinders, so I can see right away the mix. I would like to see your timing curve. I'm still having trouble with that. I am at 2.7 liter as well.
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rmel
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Re: ECU/EFI adjustments Trail versus HWY

Post by rmel »

Would be happy to shoot you my tuning info. I think I have your email address
salted away on my home system. If your a MAC guy I can send you a "Numbers"
spreadsheet, or PDF.

Ya, what a difference! I live up in the Santa Cruz Mountains a somewhat steep grade
but very windy with hairpin turns. Had to go up in 2'nd to not stall out. Now 3'rd is
just fine, far more predictable power with AFR centered at 12.5:1. It's even better still
at low-low at lower RPM down as low as 1,200 -- obstacles permitting.

I have a wide-band Bosch, using the PLXdevices wide-band controller. Has 3 outputs,
one to the ECU, one to a wide-band meter and one that simulates a narrow band bar-scale
meter. Oh! If your ECU supports this, do use the Engine Check light feature. In most cases
this light will arm when there is a LEAN condition for too long -- it will latch ON and some units
will increase the fuel injection to be safe until the condition is reset.. I find this very
useful to tell me the conditions that got me there.

cheers,

ron
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
bikmakr
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Re: ECU/EFI adjustments Trail versus HWY

Post by bikmakr »

Ron,

I'll send you a PM with my email address. I would love to see your tuning data. The actual VE numbers will not correlate necessarily but the ratios can be interpreted.

Can't you simply change your target VE table to achieve the richer numbers and still run the closed loop to achieve mileage when running higher Kpa numbers?

I can send you screen shots of my tables to compare.

Thanks
Brandt
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rmel
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Re: ECU/EFI adjustments Trail versus HWY

Post by rmel »

Home now, I'll send you the tables ASAP. First I have to clean up my PM folder -- I am overdraft so can't read your PM :oops:
But I think I just found an email from you -- we were exchanging notes on that OD converter you built.

With respect to closed-loop, it definitely should be disabled for trail use, it will just work hard to defeat best possible Power.
If your ECU supports the ability to arbitrarily set the AFR to target, for example 12.5 rather than 14.7 then that may be interesting
to try -- e.g. closed-loop for performance. My ECU only support turning closed-loop OFF/ON. I did find some comments from the
racing community that they too disable closed-loop, ironically for the same reason performance.

The only value I can see for closed-loop is HWY for runs were there is no significant grade. Grade is the killer for this feature
as I hate to admit, our rigs are under-powered for HWY speeds :( adding up to 20% in power back when on grade I'll take over
fuel economy.
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
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Jimm391730
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Re: ECU/EFI adjustments Trail versus HWY

Post by Jimm391730 »

FYI, the tuning books I've read suggest that 12-12.5 ratio does give the best power as there is enough fuel to ensure that all the oxygen (or as much as possible) gets consumed at the expense of using more fuel than is theoretically necessary. My maps also are running on the rich side; trying to eek out a bit more mpg really kills the power, and I end up using just as much fuel since the power isn't there to allow me to back off the throttle as often. So it's set richer which is also a cooler running engine. Good thing we don't have a catalytic converter or it would be cherry red.
Jim M.
712W and 710M
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TechMOGogy
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Re: ECU/EFI adjustments Trail versus HWY

Post by TechMOGogy »

Ron,
Question for you
I am very new to EFI and just started going through my setup (Jim L map)
Would it not make sense to split the difference and run inbetween 14.7 and 12.1?
Can you also not keep closed loop on and just set the value to say 13 if your ECU supports it?
Thx and sorry for my very basic questions!
Dan
72 Pathfinder | 75 710M 2.7i | 96 350GDT Worker
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rmel
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Re: ECU/EFI adjustments Trail versus HWY

Post by rmel »

Typically, peak power is at 12.5:1. It's a bell curve, if you are tuning for best Power then
stay between 11.1:1 to 13.3:1. Fuel economy is a different curve, let's say another bell
curve shifted to the right where Efficiency increases from 14:1 with a peak at 16:7:1.
Anything above 14.7:1 is too lean, HOT, and lacks power.

IMHO, you want to operate for optional power, so that's between 11.1 to 13.3. The
question is how to stay in that zone over a broad range of RPM and load conditions.

The way ECU's work is to look up a value in a table for the amount of fuel to inject
based on RMP and Vacuum (or throttle position). The table values are based on
displacement, injector flow, and subsequent "tuning" either on a Dyno or painstakingly
over time. The wrinkle in this is closed loop Lambda -- which introduces the O2 sensor
into the equation. The idea is that you have a real-time measure of the amount of O2 in
the exhaust, so why not add more fuel if there is a lot of O2 in the exhaust, or reduce
the fuel if you see the exhaust is O2 starved. The problem with closed-loop is that it's
target is to get to 14.7:1, best fuel economy -- thus trading off power . The problem is
you can't arbitrarily set closed-loop to target best power, e.g. 12.5:1, for that matter you
can't set the tables with let's say 12.5:1 entries per se. What you have to do is turn off
closed loop adjust the MAP table entries such that under engine load conditions your
between 11 to 13.3 -- essentially the only direct control the ECU has on fuel is to control
how long the injector is open, thus how much fuel is injected. Injectors are Open/Closed
valves. You just have to get regular logging dumps from your ECU and tune from there.
You may already be in the happy zone. If you have the capability to get an AFR meter
in eye sight I'd do that, it's the best way to get immediate feedback on where you engine
is running.
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
Nxp
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Joined: Sat Jul 31, 2021 11:50 pm
Location: Alaska

Re: ECU/EFI adjustments Trail versus HWY

Post by Nxp »

Hello
I’m new to the EFI system
It’s model em-4
Anyway you’d send me your MAP values plz?
Thx a bunch!!!
rmel wrote: Fri Sep 09, 2016 4:31 pm Would be happy to shoot you my tuning info. I think I have your email address
salted away on my home system. If your a MAC guy I can send you a "Numbers"
spreadsheet, or PDF.

Ya, what a difference! I live up in the Santa Cruz Mountains a somewhat steep grade
but very windy with hairpin turns. Had to go up in 2'nd to not stall out. Now 3'rd is
just fine, far more predictable power with AFR centered at 12.5:1. It's even better still
at low-low at lower RPM down as low as 1,200 -- obstacles permitting.

I have a wide-band Bosch, using the PLXdevices wide-band controller. Has 3 outputs,
one to the ECU, one to a wide-band meter and one that simulates a narrow band bar-scale
meter. Oh! If your ECU supports this, do use the Engine Check light feature. In most cases
this light will arm when there is a LEAN condition for too long -- it will latch ON and some units
will increase the fuel injection to be safe until the condition is reset.. I find this very
useful to tell me the conditions that got me there.

cheers,

ron
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rmel
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Re: ECU/EFI adjustments Trail versus HWY

Post by rmel »

Sent.
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
Rescue Pinz: 73' 712MK

Driver: Ron // KO0Q
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