IAT sensor... add resistance to lean out? - Wrist Twisters
 
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post #1 of 18 Old 10-25-2009, 10:34 PM Thread Starter
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IAT sensor... add resistance to lean out?

Well i got an idea, dunno if it will work but let me explain. We all know the 919 runs rich way rich from the factory. Now alota people get a pcm3 run w/e map they like best and enjoy the correct tuning. BUT alota ppl like me cant justify or have the money for a pcm 3... this is when i got to thinking.

We have an intake air temperature sensor. a simple thermistor. And if its like most thermistors, its resistance increases as air temperature rises, telling the ECU to lean the mixture slightly due to hotter temps. Now on most cars you couldnt do what im about to explain because there are 02 sensors that will counter act this and recalibrate the ECU to the new intake air temperature resistance. BUT on our 919 we have no such thing, and thus there is no way for the ECU to tell if the mixture it to lean or to rich, it simply just does what the IAT says in respect to air temperature and respective fuel mixture window.

Now what im proposing is if the IAT sensor's resistance increases with a rise in temperature, to simulate a rise in temperature one could simply add a resistor inline on either side of the sensors 2 pins. This would make the bike think its running in hotter weather than it actually is and thus run leaner.

Ima do a lil probing with my multi meter. Ill let you guys know what i find. But please share your opinions and knowledge on this, as im not 100% sure that just making it seem like hotter air is entering the motor will in the end lean it out.

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post #2 of 18 Old 10-25-2009, 11:17 PM
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you should see if you can get "robtharelson" to jump in on this , I believe he has a post with regards to the bike running rich somewhere here. If I remember correctly he concluded that 919 does not run rich until it gets to high RPM's. this was designed as a form of cooling of valves . I hope I'm not misquoting him

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post #3 of 18 Old 10-25-2009, 11:25 PM Thread Starter
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hmmm. ya id like to get someone here with some experience with the bike in regards to tuning.

I do feel as though it runs quite rich across the whole rpm range, some areas more than others, and it would be beneficial to lean it up across the board. I dunno. Ima play around tomorrow, look at resistance values and wiring diagrams. Maybe wire up a multi turn variable resistor inline and play around. We will see, ill report back and hopefully we can get some more incite on this idea.

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post #4 of 18 Old 10-26-2009, 01:15 AM
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I'd use a variable resistor, but also an oscilloscope on any of the fuel injector control lines to see if you can notice the pulse width changing (narrowing) when you up the resistance.

Do you happen to know the resistance range of the thermistor?

Also, it seems odd to to get an external unit (like a PC3) to lie to the ECU to get it to lean out the low-end mixture, so I wonder if anyone just chips the ECU itself. Kind of an expensive part to bust open to see if there's an obvious EPROM in there that can just be replaced.

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post #5 of 18 Old 10-26-2009, 03:59 AM
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I would not recommend putting a resistor inline because if you lean it out at idle it will also be lean at WOT, if the bike is to lean at WOT it can cause damage to the engine, high performance engines usualy go rich at WOT to keep from damageing them, i get customers coming in on occasion saying there evo's smoke at WOT and just explain to them that is normal because the computer riches up the mixture to prevent damage to the engine. I know bikes are different but the do run under the same princibles the sport cars do. the pc3's have different maps for different set ups and iam sure they go richer at WOT.

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post #6 of 18 Old 10-26-2009, 04:34 AM
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I'll look it up later and post it, but there is exactly what you are talking about on ebay. Sells for like 20 bucks or something.

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post #7 of 18 Old 10-26-2009, 05:32 AM
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post #8 of 18 Old 10-26-2009, 06:58 AM
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WOW!!!!!111

35 HP for only 20 bucks. Honda engineers must be TERRIBLE at their jobs.

Our founding fathers understood that the guys with the guns make the rules!

"I'll keep my guns, money and freedom...you keep the change"
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post #9 of 18 Old 10-26-2009, 07:05 AM
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WOW!!!!!111

35 HP for only 20 bucks. Honda engineers must be TERRIBLE at their jobs.
Kind of what I thought. I wasted 300 bucks on a pc3 and another 350 on dyno runs for even less gains that what they say I'll get for $20.

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post #10 of 18 Old 10-26-2009, 08:54 AM
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Quote:
Originally Posted by Ripper View Post
Kind of what I thought. I wasted 300 bucks on a pc3 and another 350 on dyno runs for even less gains that what they say I'll get for $20.
well.... its gotta be true... its on ebay... they can't lie on their postings...



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post #11 of 18 Old 10-26-2009, 08:56 AM
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the idea on the ebay chip is to richen the mix, the op wants to lean it out.

I say there is too much variability between each bike to make one chip and not damage at least one bike, especially if you are leaning it out. There is much less risk in richening a mixture than leaning it out too much.

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post #12 of 18 Old 10-26-2009, 09:09 AM
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That's extremely cool, Ripper. Thanks!

Of course, as you guys have noticed, their claims are just a little outlandish. Let's ignore the dyno chart that shows even the engine with the stock chip getting twice the hp and twice the torque of everyone else's 919 (what's that chart from, a Hayabusa?), it somehow claims that by enriching the fuel mixture all over the map that you'll get better mileage. I guess they know something about fuel and power that the rest of us don't.

And it sounds like what the chip does (tell the ECU the engine's always cold) is the exact opposite of what nd4spdbh is looking to do. It would be very close to putting his proposed resistor in parallel with the temperature sensor rather than in series, thereby reducing the resistance.

Still, it's actually cheap to see what they give me, and give me a leg up on understanding how things are mapped in the ECU firmware, so I can substitute my own mapping. The alternative is a logic analyzer.

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post #13 of 18 Old 10-26-2009, 10:42 AM Thread Starter
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i mean correct me if i am wrong, but the reason why everyone gets a PCIII is to run leaner maps as the 919 is super rich from the factory right?

granted fooling the stock ecu into thinking its hotter and to thus run a lil leaner wont provide as good of results as a PCIII but it will be able to be done for all of 2 bucks, and some tinkering.

I just wonder however, does the stock ECU retard timing as intake air temps go up? cus then it would be completely pointless.

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post #14 of 18 Old 10-26-2009, 11:46 AM
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TANSTAAFL

First, I'm going out on a limb here and say the IAT sensor is a conventional NTC thermistor (the higher the temperature the lower the resistance), so a series resistor should fool the ECU into thinking the air is colder than it actually is. This is, of course, across the board. Unfortunately the stock injection map is not linear -- below 5500 RPM and 2/3rds throttle the A/F ratio is in the 13.2 to 13.6 : 1 range: just a little on the rich side of stochiometric. Leaning out in that range could cause throttle response issues, and at worst a holed piston or two. Above that it drops into the high single digits which is where the PCIII's come into their own, but you must remember the old racer's adage: "Play with rich, but flirt with lean."

As to opening up the ECU ... unless you have very extensive knowledge in removing electronic grade epoxy potting compound from around each IC and transistor all you'll end up with is a non functional ECU. Even then there isn't an EEPROM to remove (why make it removable if you can't get at it?) so forget opening it up. There are a bunch of extra pins in the connectors, and a likelyhood of a serial port equivalent for reprogramming, but Honda isn't too forthcoming with any information in this area.

+35HP PERFORMANCE CHIP HONDA CB 600 900 F HORNET:eBay Motors (item 390104536520 end time Nov-09-09 11:57:42 PST)
Heard of these. While they show a generic IC, all it is is a resistor in a fancy package that does what you want to do. It probably costs all of 22 cents to make, and will sell to all sorts of unknowledgeable (one born every minute) buyers thinking 35 HP gain for $20 couldn't be beat. GFL getting your money back if it doesn't give the claimed gains! It probably does produce the gains they say ... on a fuel injected 8 litre V-10 Dodge motor. About 5%. There isn't an easy way to get an equivalent gain from a 919, and certainly not for the 50 cents for a resistor. You might gain 5 HP with a good free flowing exhaust and a PCIII, but there is no simple wake up call for high performance.

My recommendation? Just ride it. If you want heaps more power buy a litre class sportbike -- they are designed and built for the kind of power you're thinking of, and you neatly avoid having to buy all sorts of stronger components to get less performance from the 919.

Then there's the chassis .......

Rob

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post #15 of 18 Old 10-26-2009, 12:48 PM Thread Starter
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understandable... ima hook a multi meter up to the IAT see how it works... either higher or lower resistance when temp increases. It will be much easier if its of the type.... temp rises resistance goes up. Im not looking to drastically lean it out, just fool it to think temps are 10-15*F higher maybe to see if leaning it out just a bit will increase Throttle response.

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post #16 of 18 Old 10-26-2009, 03:52 PM
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Quote:
Originally Posted by robtharalson View Post
My recommendation? Just ride it. If you want heaps more power buy a litre class sportbike -- they are designed and built for the kind of power you're thinking of, and you neatly avoid having to buy all sorts of stronger components to get less performance from the 919.

Then there's the chassis .......

Rob
+1 The very small gains are not worth the effort Vs. the possible things that can go wrong. Honda engineers did a good job making a nice around tune.

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post #17 of 18 Old 10-26-2009, 05:35 PM Thread Starter
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Ya so i got home today and took off the air snorkle to get to the IAT sensor. unplugged it and saw which way it worked.... the inverse way, temp goes up resistance goes down... thus not as easily messed with (would have to run a resistor in parallel... and then it would just act all weird) so i said meh F it... ima just go ride it, and ended up going on a 70ish mi ride.

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post #18 of 18 Old 06-15-2010, 06:15 PM
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Can you get to the point where you can see a part number?

Regards, Guy

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