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Discussion Starter #1 (Edited)
Figured I would seperate this out from the long thread found here -> http://www.hondagrom.net/forums/7-grom-talk/10270-finbro-ecu-cold-starting.html

I am 95% positive i have found a solution!!!!

Background / What we know:

The stock ECU actually does enrich the mixture to make cold starting much easier when paired with the high idle valve. This was very easily seen via a volt meter across the injector. Stock ecu, cold motor, start the bike, watch the voltage at the injector (pcx 150 injector in my case), listen for the lil POP of the high idle turning off and you instantly saw a ~20-25% drop in voltage of the injector. In other words, with the stock ecu any time the high idle valve is opened by the ecu, it also feeds the bike ~20% extra fuel. Exactly what you need for a cold start.

The problem we have with the finbro ecu is the fact it doesnt 1. use the high idle solenoid by default (that allows extra air in at idle), but mainly 2. It does NOT add extra fuel to the mixture when the motor is cold for cold start enrichment.

We also know, the check engine light, high idle valve, and more importantly the injector are all GROUND SWITCHED. That is important.


So i went back to my original design here:

http://www.hondagrom.net/forums/7-grom-talk/10270-finbro-ecu-cold-starting-2.html#post138248

And tweaked it a little, I added in a very simple circuit to hold the injector open a little longer thus increasing fuel at idle to the motor (SAY WHAAAAAT?!?!)

I used my original design (which turn on the CEL and High idle valve together). Changed my switch to a DPDT (which is really just used as a DPST) switch, so i had another isolated circuit to play with that was switched at the same time as the CEL and high idle valve. This extra switch circuit was used to ground out the negative side a 68µF 25V electrolytic capacitor, where the positive side was tapped into the injector wire (pink / green, pin 16 of the ecu). The 68µF Cap gets discharged relativly VERY quickly when the ECU grounds out the injector for one of its pulse, but then when the ECU stops grounding out the injector, the injector can STAY OPEN longer as current can still flow through it to charge up the Cap. 68µF seemed to be ideal after some trial with various other sizes. It supplied right around a simulated extra 20-25% duty cycle at idle for my setup. Thus properly supplying the motor with the much greater amount of fuel needed for an easy cold startup.


Note YOU DO NOT cut the injector wire, you are simply tapping into it. (Obviously it goes without saying, you do the above, any damage is on you)




Here you go gents,

Seems to of definitely helped cold starting!!!


 

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Discussion Starter #6
Gotta say, came home today, le grom had not been ridden in over a day. Hopped on her, flipped on the cold start switch, turned ignition on, tumbed the starter switch really quick and she sprang to life.

Instantly started riding, left the cold start on for about 2 min while she warmed up, then flipped it off and all was still good.


SO MUCH happier with this experience with the finbro ecu, I was so used to stock where you could get on it from dead cold and just go, and my cold start switch has brought that back.


I will be interested to see what its like in cooler temps as its been pretty mild around so cal this past week. (That video was shot when it was 60*F out)
 

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So, who's going to be the one to assemble and sell a kit? I imagine there's a lot of people who would want this to retrofit. Perhaps Franco could offer it with the ECU? Or HR as a drop down option?
 

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This solves a huge problem. I replaced the starter (wemoto) & the battery (shorai) and the cold start improved slightly meaning I didn't kill my battery starting it. It would still take 3-4 min. 1 min to put load on the battery, 1-2 min of cranking. Was a joke.
Thanks for this info. Does the 31 mm TB finbro sells support the high idol valve?
 

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Discussion Starter #13
So, who's going to be the one to assemble and sell a kit? I imagine there's a lot of people who would want this to retrofit. Perhaps Franco could offer it with the ECU? Or HR as a drop down option?
Personally, i feel like the Monkey father / Finbro / Franco of finbro, should go back to the drawing board, and use the US based grom ecu and put their programming on one of those to keep the stock auto enrichment. BUT because that is not the case a kit of something like this would be nicely included with the ecu and really its all of 5 bucks extra in parts. You could even go as far as not requiring any soldering by using a bigger DPDT switch that you could use blade connectors on so everything is just crimped together.

This solves a huge problem. I replaced the starter (wemoto) & the battery (shorai) and the cold start improved slightly meaning I didn't kill my battery starting it. It would still take 3-4 min. 1 min to put load on the battery, 1-2 min of cranking. Was a joke.
Thanks for this info. Does the 31 mm TB finbro sells support the high idol valve?
No idea, but i think the 31mm TB that finbro sells is simply a forza 300 TB, those stock do not have a high idle valve, but better they have an idle air control valve which actually does the job of the idle air screw and the high idle valve on our groms. That stated, this is a much more complicated piece of equipment and our ECU does not support this, so its blocked off on the "finbro" ones.

i may have to switch over to it. So where would a person find a 68µF 25V electrolytic capacitor?
Like the person above linked to any 68uF cap will work so long as its got some headroom above 12v (i would say 25v would be the lowest id go). That stated i got my 68uf cap out of an "assorted bag of capacitors" from radioshack.
 

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I just purchased all the parts to get this done, will hopefully do it this week after work one day. Still waiting on my exhaust so will be delayed in trying it out. fwiw, Radioshack only sells the 68µF cap in the mutli pack, can't buy them individually. We'll see if it's the same for my 8-hole injector/170 4v. The Koso 34mm TB I'm using has the high idle valve.

I would also suggest to add some hotglue or epoxy around the switch solder joints for extra security in regards to vibration, especially on this bike.
 

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Discussion Starter #17
I just purchased all the parts to get this done, will hopefully do it this week after work one day. Still waiting on my exhaust so will be delayed in trying it out. fwiw, Radioshack only sells the 68µF cap in the mutli pack, can't buy them individually. We'll see if it's the same for my 8-hole injector/170 4v. The Koso 34mm TB I'm using has the high idle valve.

I would also suggest to add some hotglue or epoxy around the switch solder joints for extra security in regards to vibration, especially on this bike.

Definitely report back!!! The 68uf cap worked well with my pcx 150 injector, it might not be the same with the bigger 8 hole injector (though theoretically if its the same OHM rating the 68uf should do just fine) But worst case you go the variaty pack from radio shack and i think there is a 100uf cap in there.

And yeah On my switch i captured every solder point with some heat shrink then encapsulated all the connections in a big piece of heat shrink. Vibration disconnections shouldn't be an issue!
 
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