Dyno Tuning Basics - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 23 (permalink) Old 12-15-2015, 12:38 AM Thread Starter
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Dyno Tuning Basics

With the recent interest in RC51 cooling on the forum, SPAL fans, Wibbly brackets, DHC radiator scoops, etc, I have a question regarding an article on the rc51.org site about dyno tuning. Specifically this part:

Quote:
Current Honda ECU's automatically get richer as the engine temp increases the air/fuel ratio is changing constantly at a non linear rate. For instance you may get the 100% perfect map developed for your bike on the dyno & let's say the engine is at 185 degrees, well at certain points in the rev range their are windows in the ECU where the mapping changes the mixture. Let me give you some examples (these windows will be different for each model of bike & even the same model of bike can have different ECU eproms for various countries/regions)

168-172 degrees is a window
173-178 is a window
179-184 is a window
185-194 is a window
195-205 is a window
206-212 is a window
213-218 is a window

Each one of those windows has a different mapping forced by the ECU that alters the air fuel ratio of the bike & generally they get richer in steps (sometimes a window at a higher temp can also be leaner) so even though the PCIIIr map may be perfect for 186 degrees it may not be so great for 195 degrees & it then might be worse or better at even 206 degrees etc....
5 degrees of engine temperature change can make a 7-10 horsepower difference. Pretty big deal.

With the previously mentioned cooling mods and a controller like this:
20 90°C Adjustable Temperature Control Switch DC12V Sensor Thermostat Probe | eBay

One could essentially keep the engine at any temperature they want. So what would the ideal temperature be for the RC51?
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post #2 of 23 (permalink) Old 12-15-2015, 07:08 AM
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Now that a magnificent and a useful thread

Thank you very much for it @drifter83


My Öhlins Project: https://www.rc51forums.com/forums/showthread.php?t=6033
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post #3 of 23 (permalink) Old 12-15-2015, 01:41 PM
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isn't that what your thermostat is supposed to do? What will this sensor control to MAKE the engine cooler? I know in SOCAL when the ambient temp is 110 F and sitting idle at stoplights, I could reach 230F...so, if this thermostat opens and says "cool", whats going to cool the engine?
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post #4 of 23 (permalink) Old 12-15-2015, 01:44 PM
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OR does this just "lie" to the ECU to make it think it is at the preset temperature? Not sure how it would work. Please explain.
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post #5 of 23 (permalink) Old 12-15-2015, 08:45 PM Thread Starter
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The thermostat primarily does two things, accelerate engine warm-up time and regulate minimum engine temperature.

From what I gather, the RC51 usually doesn't have much problem maintaining minimum temperature once warmed up.

What I'm interested in is regulating the maximum engine temp.

I would use the temp sensor I linked from ebay, or a similar design, to automatically activate the SPAL fan to keep the operating temp in the range I specify.

So it would be like the radiator fan switch mod, but automatic and set to maintain a temperature window of my choosing. That's why I am interested in seeing what the "best" temperature range is.

Quote:
Just as with the case of the cold engine, it’s not terribly uncommon to find a coolant temperature map that becomes extremely rich once a certain high coolant temperature is reached. The additional fuel slows combustion, greatly lowering combustion chamber temperatures. The additional richness also cools the combustion chamber through evaporative cooling, as was mentioned in the section on cold running above. Honda is particularly fond of this strategy, which is prevalent on the RC-51.

Wade, A. (2004). Motorcycle fuel injection handbook. St. Paul, Minn.: Motorbooks International.
The way I understand it is that there is a lookup table that enriches the mixture beyond the normal fuel mapping dependent on coolant temperature. During startup, when the engine is coldest, more fuel is added. As it warms up, this is decreased until the ideal operating temperature is reached. This coolant temperature lookup table begins adding fuel again in addition to the normal fuel map, as the engine heats beyond its ideal operating temperature.

The article on rc51.org seems to say that it isn't quite as simple as I described above and that the ecu doesn't simply continue to enrich the mixture the hotter the engine gets. It implies that there might be "better" windows at an even higher temperature.

What I'm looking for is the RC-51s ideal operating temperature. The service manual states that the thermostat begins to open at 176-183° F and is fully open at 203° F. To me that means the ideal operating range is between those numbers... but perhaps not? That is what I'm looking for.
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post #6 of 23 (permalink) Old 12-15-2015, 09:06 PM
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I have heard 185 is the best temp; however, even with 2 spal 5.2" fans running in stop and go traffic, my temp would reach 220-230 so I'm not sure how you can keep it at the exact temp by turning on the fans as it hasn't worked so far..unless you have a super efficient cooling system or are constantly moving.
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post #7 of 23 (permalink) Old 12-15-2015, 10:35 PM
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i think you're overthinking this, the bike is happy between 185 and 200. with scoops you shouldn't have much trouble keeping those temps.


trying to stick bandaids on the bike to "optimize" the running is just going to cost a bunch of headache for gains that are likely to be negligeable, perhaps only detectable on the dyno.


the big thing with the 51 is keeping it from trying to melt down when you're out on a hot day in stop and go. the scoops and fans should keep that under control. once you're out riding (when you actually NEED that peformance), temps should be stable anyway.
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post #8 of 23 (permalink) Old 12-16-2015, 12:19 PM
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Snake Oil.
imo

Like Ogiehooker says, if you're sitting in traffic in a 100F degree day, and one or both fans are running, how is this device going to improve the cooling task of the fans?

I tried the low-temp switch, which would kick my fan on at 190F. Great, a headstart in cooling action from the fan(s). But if you're not moving, or moving very slowly, like downtown traffic, the bike continues to rise in temperature to as high as 225F in my case. So all that really happened was my fan ran a lot more than usual, and my bike still reached temps of 210-220 on a regular basis.

I have to mention, I was seeking better cooling for MY comfort, because once your frame and tank get hot, it's no bueno for your thighs and rest of your parts!

John, 2000 RC51 #000100

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post #9 of 23 (permalink) Old 12-16-2015, 01:37 PM
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Originally Posted by jondog9 View Post

I have to mention, I was seeking better cooling for MY comfort, because once your frame and tank get hot, it's no bueno for your thighs and rest of your parts!

Come on Jon, get the sand out of your vag, buck up and go ride your hot, uncomfortable bike
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post #10 of 23 (permalink) Old 12-16-2015, 01:44 PM
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Come on Jon, get the sand out of your vag, buck up and go ride your hot, uncomfortable bike
Hahaha, laughing my vag off right now!

How are those panty-kool-liners working for you LDH?

John, 2000 RC51 #000100

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