I looked in Bob/bbywu's excellent sticky but didn't find the result. Just curious, not doing anything nutty :-) based on this.

1. What does this parameter "Engine Load" measure? What is its unit in Durametric (lb-ft? Newton meter?)?

2. Is it real/measured? Or is it, the term is "requested" or something like that?

3. What is the formula for conversion engine load to horsepower? I saw this: Horse Power=Load*RPM*pi/16,500. Is that it and anyone has any idea how that is derived?

Thanks in advance, Bob and Dave .

 

Hi Tony, thanks for taking time to answer.

Of the above 4 choices, which one is the one that I am seing in Durametric Datalogging please? All the title says is "Engine Load" IIRC.

 

Tony pretty much summed it up. It's a Volumetric Efficiency calculation based on input parameters of MAF, IAT, rpm, etc...so it's unitless. You can't really equate it accurately to horsepower because different dyno's are calibrated differently and will give you different readings. This is the beauty of measuring engine load on the DME. It's all based on the same input parameters from car to car but the DME is constant. Your load curve vs RPM will align with your torque curve on a dyno. It's a poor man's dyno and a way to street tune your car. You don't need a formula. Just look at your load values and you will be able to tell how much relative torque your motor is producing. The formula you cited (which I also haven't seen) for HP is simply mathematically manipulating another calculation which you don't really need. For instance, my 63.5mm vtgs with Proto tune was putting out load values of around 250 max. That correlated to a 6.8-6.9s, 60-130, flat, full weight time (4th gear pull). Hope this clarifies.

 

Yes, that is the parameter. Not the Engine Load (SAE).

 

Thanks Dave for the very good explanation.

1. Please clarify: the Durametric "Engine Load" that I see is actual, NOT requested?

2. Did I understand you correctly, that in many ways this Engine Load could be compare across cars with more accuracy than dyno curve because it is a number that can't be manipulated like a dyno?
In other words, if I am seeing 220 max Engine Load, that means that my car is generated 12% less torque than your 250 (I understand, at whatever condition and rpm that we achieve our nunmber.

 

Yes, it's actual load. I don't believe there is a requested load parameter in Durametric.


Yes, that is correct -- direct comparison; none of this your ECU is whimpier than mine. But don't let that take all the fun away from arguing over dyno numbers.

 

No bottom line we all know is Vbox right. Anyway, thanks Dave; I understand this better now.
2 more questions please:

1. Does engine load depend on which gear I am doing it? For example, I didn't want to be put in jail so all I did was 3rd gear WOT from 2000 rpm. What I got was max engine load = 220 at 3600 rpm. Could I compare this number with another person who did his test in 4th gear? Another way to ask the question is, does max engine load value vary depending on which gear it was obtained in? And other condition such as at what rpm I stomped on the throttle? (I wasn't aware of how important this is so I didn't do these other tests that I am asking you now.)

2. Should "engine load" be the ultimate parameter that you should check for during datalogging with your tuner?
In other words, I know lamda is very very important, ignition angle obviously, but those numbers are for the tuners to decide what's right or wrong, what's safe or not. Engine load OTOH is quite relevant and easy to understand, more is better.
If my tuner makes a change in the program and I now see that the load is down, is that cause for concern and questioning?

 

As long as you get to full load. 3rd or 4th gear should be fine. Higher gear, load would come on earlier just like dyno. Lower gear, might not be able to get to full load.

Engine load is a calculated parameter representing volumetric efficiency of a motor. The more efficient the motor, the higher the VE. VE is also rpm dependent and a function of motor design and any peripherals like turbos. So VE depends on both hardware and software. You want your tuner to be able to maximize your tune based on the hardware you have. For instance, stock turbos will only do so much. Your VE is going to be limited compared to an upgraded VTG no matter how optimized your tune is. In theory, for ultimate power, you want to maximize the load at every RPM, which will give you the greatest area under the curve. You can only do this if your tuner sticks your car on a dyno and tunes every at every couple of hundred rpms.

 

I read up on this topic related to Dave's and Tony's explanation of "Engine Load": Volumetric Efficiency. It's in Wikipedia if anyone is interested.
I believe what's confusing to me was that while my question is about "how much power," the answer seems to be about the amount of air moved by the engine! I am starting to see the connection though; I think :-).

>>>>>>>>>>>>>
Wikipedia
Volumetric efficiency in the internal combustion engine design refers to the efficiency with which the engine can move the charge into and out of the cylinders. More specifically, volumetric efficiency is a ratio (or percentage) of the quantity of air that is trapped by the cylinder during induction over the swept volume of the cylinder under static conditions.VE can be improved in a number of ways, most effectively this can be achieved by compressing the induction charge or by aggressive cam phasing in Normally Aspirated engines as seen in racing applications. In either case VE can exceed 100%.

Volumetric efficiencies above 100% can be reached by using forced induction such as supercharging or turbocharging.

 

Very good point Dave. I remember the discussion during my car's dyno tune was the shape of the torque curve - exact same point that you are talking about. After each dyno, multiple curves were displayed on the big screen, the engineers would look at the curves and numbers, discuss stuffs like AFR, then took the ECU off, re-programmed it, then ran the dyno again. As the day went on, each successive run produces a better curve until the fat final one.

An interesting point was Garrett seemed to be able to predict ahead of time what changes will happen when he re-programmed. A minor but even more interesting point was he also seemed able to hear from the sound of the dyno run whether it was a good run! I guess this happens when you've done too many of them.

Back to topic at hand, my "Engine Load" in my stock mode yields max Engine Load of 154 at around 3300 rpm. Questions for you please:
1. Anyone on this forum with a stock car should yield a similar number for Engine Load at similar temp, about 154 in Normal stock mode? Did you have similar number for yours?
2. I am always suspicious, ok... curious, about horsepower gain with exhaust alone, I could have done this test and find out the result for myself: Testing for engine load values before and after exhaust install would tell me whether the exhaust has gained power?
Thanks.

 

Can, That number (154) is right in the ballpark for stock (similar to mine), so no worries there. And yes, you would be able to estimate relative gains using load values before and after exhaust change.

 

Dave,

With my Durametric datalog numbers, if I am to graph "Engine Speed- RPM" on the x axis, and "Engine Load" on the y axis, then this is an approximate of the torque curve of a chassis dyno?

This would be such a powerful tune to monitor tuner's alterations of the ECU program after each datalog run. The graph allows one to visualize "area under the curve" very quickly.

Thanks for taking time to answer Dave. I hope more than just me (for example customers who rely on datalogging of OBD tuning) is reading your words of wisdom.

 

Here's an example of MBailey "upgrade" from GT740 to GT775 based on AUC using load (VE) measurements. This resulted in faster 60-130 time. It's been a while since I first posted this years ago so I don't remember the details.

 

Great read !! Keep it up guys..I've also heard MAFless tunes produce a bit higher load #s;
is that bec it makes more power or something else ? my highest load #s are in the 265 range - dont think hit quite 270 but not 100% sure .. I am a proto 3076 blo-through setup

 

MAfless tune will calc load differently than with maf. Don't know if the values are exactly the same but I suspect that the difference is small. 265 is a solid number. How much boost are you running?