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Discussion Starter #1
Guys,
Highsider989 asked me if I would chime in on the large fuel injector that is available from Japan.

First, give me a second to let you know what I do. I work for one of the oldest & largest industrial engine manufacturers in the US. I'm presently working on their latest prototype engine program. I designed all the induction, including the cylinder head ports. I also am in charge of all the testing. My last project was their EFI engine, converted from carburation.

OK, so much for that:
All most all EFI systems monitor:
intake temperature, intake pressure and air density - what kind of day is it, IE, hot & muggy, cold & dry, how much air is being sucked in by the engine
crankcase oil temperature - does the system need to be enriched for start up
throttle blade position - closed idle, mid throttle, wot & the throttle is pegged
air flow in CFM - cubic feet per minute - I don't think this system has this - my bike is still 2 weeks away
ECU - with a closed or open mapp - calibrated at the factory to pass emissions, etc
Lastly - a narrow or wide band O2 sensor, calibrated to 14.7 air fuel ratio, for the cat./emissions system

The ECU sends out a signal based on all those inputs, and opens the injector circuit for a predetermined pulse width
This bike having a narrow band O2 sensor just turns on & off sensing whether its at 14.7/1 or not.
The ECU sends out the same signal regardless of the size of hole in the injector, IE, rich fuel condition.
Without a wide band O2 sensor to monitor the mixture, or at least tell you whats going on, it's a crap shoot
I contacted my friends @ Dynojet this past week to see how far along they are on there PowerCommander for the Grom.
It's going to be a fairly simple box that can alter the mixture - lean/rich, @ idle/mid/top end
I do not know if it wil have a wide band O2 sensor
I'm putting my Grom on the dyno after it has 100 miles on it, & I'm welding a fitting, before the cat, for a wide band.
I'll have a much better idea of the workings of the system in about 3 or 4 weeks, and what it will take for modification
Hope this helps, more to come
Brian S
 

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14.7 to one being the ideal stociometric ratio for a complete burn of the air fuel mixture. Leaner or richer the burn is not as good leading to a dirty or polluting engine, bad fuel efficiency thus poor fuel economy.
 

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Hey Brian. I was in the engine and vehicle testing industry as well. I am planning on throwing the grom on the dyno as soon as I get it for baseline numbers. I do alot of performance calibration work as well.

Sent from my Samsung Galaxy S4 using HondaGrom.net mobile app
 

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Welcome to the forum turbo. Please post up your dyno results when you get them.
 

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Will do. I plan on making as many performance parts myself as I can. I use a mustang ac motoring dyno that we have used for epa emissions certs for other models so data is as accurate as factory.
 

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Wow two experts in the industry are among us! Very cool.

I doubt i will understand your results, but i will have fun trying!

woo hoo! it is already the 5th. 11 days more for the first groms to hit US shores.
 

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From what I understand a14.7:1 AF mixture may not be ideal to produce the optimal power output throughout the entire RPM range and under all load conditions. The stock map uses a table of mathematical variables and when the system is In closed loop mode at operating temperature the ecu computes and changes the length of Pwm based upon which variation of inputs from an array of analog sensors like the temp sensors. Additionally there are inputs from digital sensors like hall effect sensors. For example, if the engine is at X temperature at Y altitude based on the Map sensor and the oxygen content in the exhaust from the O2 sensor the ideal AF mixture could hypothetical be leaner, say 13.9 based upon the current engine conditions. This is why it's not so easy to just slap on a box and call it good. You need a dyno to optimize these mapping tables.
 

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From my experience the afr will be more geared toward emissions. I am unsure if the grom will have power enrichment or run open loop fueling at wot. Anyone have any facts?
 

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From my experience the afr will be more geared toward emissions. I am unsure if the grom will have power enrichment or run open loop fueling at wot. Anyone have any facts?
Unfortunately, not yet. We are all hoping guys like you and Brian S can spend some of your time educating us carburation guys. Once you have a Grom in your hands, will you be able to find out the questions you ask?
 

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All most all EFI systems monitor:
intake temperature, intake pressure and air density - what kind of day is it, IE, hot & muggy, cold & dry, how much air is being sucked in by the engine
crankcase oil temperature - does the system need to be enriched for start up
throttle blade position - closed idle, mid throttle, wot & the throttle is pegged
air flow in CFM - cubic feet per minute - I don't think this system has this - my bike is still 2 weeks away
ECU - with a closed or open mapp - calibrated at the factory to pass emissions, etc
Lastly - a narrow or wide band O2 sensor, calibrated to 14.7 air fuel ratio, for the cat./emissions system

The ECU sends out a signal based on all those inputs, and opens the injector circuit for a predetermined pulse width
......
Thanks very much for any input you can offer us, Brian!

So given what you are saying above, if the ECU reacts to the array of sensors, will a larger discplacement kit and a different cam effect any of that? Or will the ECU simply adjust to what the sensors are reading (which may not be very different than stock displacement if its mainly reading ambient conditions)?
 

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The key here is if the ecu operates full time closed loop or not.

Sent from my SCH-I545 using HondaGrom.net mobile app
I don't think so. It probably goes to closed loop after the engine reaches it's optimal operating temperature like a car does. This is probably why on the yuminashi website he mentions the efi having to adapt to the changes with a bore kit and that it takes 10-15 minutes.

The ecu should be able to adapt to some extent, like with a light bore kit or exhaust. If the sensors read outside the range they were designed for the ecu will only be able to compensate up to a certain degree, but after some time it will turn on the CEL and default to open loop. Eventually, an injector for example, would be operating at full duty cycle and not be a able to provide enough fuel for the increased air flow. Another limiting factor, as mentioned before, would be the narrow band O2 sensor. You would need to have an efi controller designed to run with a wide band sensor to be able to maintain the stoiciometric mixture to allow for stage II or III tuning.
 

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Discussion Starter #16
Fuel Injection 201

Guys,
I'm very impressed, this has turned into a great discussion.
A few basic facts:
Ideal air / fuel ratio for making good power with an air cooled engine - 12.8 to 13.2 - shoot for 13 / 1
leaner air / fuel ratio - 14.7 / 1 >
richer air / fuel ration- 14.7 / 1 <
O2 sensor reading - 12.8/13.2 - .88 / .90 lamda, unleaded gas, depending on how the gage dia is set up.
Ideal air / fuel ratio for running down the freeway 13.8-14.0 / 1
Start-up, cold engine, about 11.8-12.2 / 1
Acceleration, 12.2-13.2 depending on the engine
* A narrow band O2 sensor is set up to bring the fuel curve back to 14.7 / 1, not any richer, unless Honda programed it odd
* Lean is hotter, hotter means less HP, hotter means parts wear out faster, oil breaks down faster, cooler is good
* DO WE ACTUALLY KNOW FOR A FACT THAT THE ECU RESETS WHEN THE 12 VOLTS ARE REMOVED???
* Most ECU's do not reset, because they have internal batterys, and they save the data
* Cats need to get hot and light off, and they do that with a stoic fuel ratio
Brian S
Fuel Injection & Mufflers to follow
 

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Discussion Starter #17
Fuel Injection & Muffler / Cats / Pipes #1

For practical purposes, EFI is the same as carbs, just a lot more accurate. They cost Honda more to make, so if emissions were not around, the Grom would probably have a simple Keihin carb on it. Honda owns about 40% of Keihin. But emissions & cats are here to stay, so, if we have to we make it work.

EFI & a cat back systems, ie, a slip-on muffler/pipes: The cat is the biggest air flow restriction in the exhaust system, so a slip-on pipe is most probably a weight reduction, and yes it looks good, but performance gain, ???
I flow test all my exhaust system parts on a 1020 SuperFlow digital flow bench. If I don't see an improvement in air flow, I never see a HP/torque improvement. But street engines NEED a little back pressure off idle and in the mid range, so straight through systems are not always the best street set-up.
So we are down to what's the intended use???
If it's a street Grom with a slip-on and a slight upgraded shock used around town, and for a pit bike? I'm guessing the stock system will handle it just fine, so long as the muffler is not straight through, and has chambers to dampen the sound pulse.
A complete system will probably have less back pressure, meaning less bottom end, and a little more top end performance.
The saying is: There is no free lunch! You gain one place, lose somewhere else.

Let me tell you about my new 2012 Kawasaki Ninja 1000, it will make my point:
It is a very fast bike, approximately 126HP. The exhaust system is very efficient, but very heavy. I purchased a Akrapovic Stainless/Titanium full system, because I was able to remove 35 pounds off the bike, and increase the power to 141HP ( like I really need it )
The engine exhaust was too loud, and it effected the bottom end torque, but Akrapovic provided an insert for the muffler that lowered the sound level to a nice tone, and it cost me about 6 HP. But I picked up more bottom end than the stock set-up. That's a WIN-WIN for me.
135 HP, raised torque, 35 less stainless steel on the bike, & the Power Commander, with the wide band Auto Tune solved the fuel mapping.

Guys, the Taco's are here, back in 20 minutes.
Brian S
 

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Discussion Starter #18
Fuel Injection & Mufflers / Cats / Pipes #2

The Taco's were great.
Back to EFI & open pipe systems:
So you and I want to run an open full system that someone manufactured.
That's what I going to produce for my Grom, costs will dictate, if it is to be produced in volume.

A few bacics:
Longer pipes favor the lower part of the torque band, with very little effect on the high end
Shorter pipes favor the higher part of the torque band, more negative effect on the lower end
Smaller diameter primary pipes favor torque
Larger diameter primary pipes favor HP
Staged diameter pipes solve all the above
Look at Honda Grom pipe, very long & fairly small in diameter, good overall wide RPM band torque, many rider skill levels, really very well designed
7000 RPM power peak, about 29" long would be good place to start
Does anyone know the stock intake & exhaust valve head sizes? I can drop the data into my computer program

It's ice cream cone time, back in 10 minutes
Brian S
 
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