XX4me Posted May 30, 2004 Share Posted May 30, 2004 I believe they stand for Manifold Absolute Pressure Intake Air Temperature I'm curious how they affect the ECM under different conditions. Quote Link to comment Share on other sites More sharing options...
EVLXX Posted May 30, 2004 Share Posted May 30, 2004 Is the sensor on the Bird a MAP or a MAS or neither? I know what they do... Just don't know which one it is... never looked into it that deep yet. Quote Link to comment Share on other sites More sharing options...
XX4me Posted May 30, 2004 Author Share Posted May 30, 2004 It's a MAP sensor. Quote Link to comment Share on other sites More sharing options...
XX4me Posted May 30, 2004 Author Share Posted May 30, 2004 Not sure on the MAP, but as far as I know the IAT is merely a blanket enrichening device designed for cold start and extremely low temp operation. Meaning it only comes into play on cold starts and cold days and affects nothing other than fuel? Quote Link to comment Share on other sites More sharing options...
XX4me Posted May 30, 2004 Author Share Posted May 30, 2004 Interesting, Thanks Dean. The Hahn kit has the IAT sensor mounted on the fuel rail which when I thought about it would see ambient temperature of the engine compartment rather than outside air. Dave and I talked about this at MegaXX and I was planning on moving it to sample true ambient air temp today. I'm wondering how it will affect my A/F. Will "seeing" cooler air mean it will richen it up? I hadn't thought about frequency differences between the stock motor and mine. Since I'm pulling out some timing with the PCII at higher RPMs I'll disconnect the knock sensor and see what happens. I only run 93 octane so I doubt I need to worry much about "knocks" off boost. So it grounds when activated then disconnecting it should work to take it off line without affecting anything. Quote Link to comment Share on other sites More sharing options...
XX4me Posted May 30, 2004 Author Share Posted May 30, 2004 It appears that the sensor sees a normal frequency and an abnormal frequency. Also has a fail safe mode. Hmmm? Quote Link to comment Share on other sites More sharing options...
XX4me Posted May 30, 2004 Author Share Posted May 30, 2004 Now I'm making some assumptions because I don't really know the details. If the sensor circuit has a fail safe mode I would think it probably removes timing if the sensor isn't responding. So if I disconnect it I'll lose 2.5 degrees timing. Quote Link to comment Share on other sites More sharing options...
XX4me Posted May 30, 2004 Author Share Posted May 30, 2004 The IAT will typically cause richening on colder temperatures but not leaning on warmer temperatures. So you should be safe moving it to ambient, the engine compartment might be a little warm. Then again, it may make no real difference EXCEPT that the block is colder on a cold start and that may cause a virtual choke circuit of the ECM to kick in. Well I moved the IAT back into the tail section and went for 4 tuning cruises. I had to remove fuel from most of the cells. It was running around 12:1 at 10000 RPM, now after moving the IAT it was 10.5:1-11:1. It was bogging out the motor at WOT starting at 9500 RPM I know? WTF? Your guess is as good as mine. That was the only variable I know of. Quote Link to comment Share on other sites More sharing options...
XX4me Posted May 30, 2004 Author Share Posted May 30, 2004 So it's cool enough in the tail to activate the IAT and enrichen the mixture.......that's the easy take on that situation. It's just seeing ambient air temp as opposed to the radient engine heat it got in the Hahn specied position it had been relocated to. If MiDNiTXX confirms this with his bike it will be just one more fucking thing for me to rant about when talking about hahahahn kits. WTF, why would I want the ECU to lean out the mixture on a turbo bike? Quote Link to comment Share on other sites More sharing options...
EVLXX Posted May 30, 2004 Share Posted May 30, 2004 So it's cool enough in the tail to activate the IAT and enrichen the mixture.......that's the easy take on that situation. why would I want the ECU to lean out the mixture on a turbo bike? Maybe because 10 : 1 is way too rich.... but hey what do I know. Was that 10 : 1 on boost at 10,000rpm or not? You could always up your water injection and lean it out somemore. Quote Link to comment Share on other sites More sharing options...
XX4me Posted May 30, 2004 Author Share Posted May 30, 2004 Maybe because 10 : 1 is way too rich.... but hey what do I know. Was that 10 : 1 on boost at 10,000rpm or not?You could always up your water injection and lean it out somemore. I set the A/F at 12:1 for 10000 RPMs under full boost and by moving the sensor it seems to have richend it up somewhat. I guess what I meant was why would the maker of a turbo kit instruct the turboee to do something that would cause the bike to run leaner and so require some form of compensation be it higher fuel pressure or longer injector duty cycle. Quote Link to comment Share on other sites More sharing options...
Northman Posted May 31, 2004 Share Posted May 31, 2004 Simple answer: They just made a kit to fit the bike, and didn't bother testing it thoroughly, or researching it properly. The kit fits, right? Doesn't mean it's going to work right, but at least it fits. :roll: Quote Link to comment Share on other sites More sharing options...
XXTi Posted May 31, 2004 Share Posted May 31, 2004 Sorry if I'm being Mr. Obvious here, but I think the IAT and MAP sensors are used to estimate the mass of the intake air charge. The FI system adds fuel in proportion to the mass of the air charge. Quote Link to comment Share on other sites More sharing options...
Northman Posted May 31, 2004 Share Posted May 31, 2004 Mass of the air is calculated using the MAP sensor and RPM. The rest of the sensors only modify that curve to a relatively small extent, but they are the two most important sensors in a speed density fuel system. Quote Link to comment Share on other sites More sharing options...
XXTi Posted May 31, 2004 Share Posted May 31, 2004 Hmmm. That's interesting. I wonder how they do that since the mass of a volume of gas varies with both pressure and temperature. Quote Link to comment Share on other sites More sharing options...
XXTi Posted May 31, 2004 Share Posted May 31, 2004 On second (third?) thought, I guess the air temp. doesn't really vary all that much since absolute temperature (Temp F +460) is used in the calculations. It's probably insignificant isn't it? Quote Link to comment Share on other sites More sharing options...
daveszx302 Posted May 31, 2004 Share Posted May 31, 2004 Ok, time to jump in. Even MAS equiped vehicles have a air temp sensor. Older injection systems that use MAP and or vane/flapper style sensors to measure air flow still need to know air density to figure out proper injector and timing rate. When he moved his sensor to the rear of the bike and got different a/f ratios only proves that this is a full time sensor, not just a cold start sensor. As we discussed earlyier, now find a way to let the processor know actual air temp entering the engine! Fuer rail is toooo hot, tail section is to cool, air box below/after intercooler is actual air temp into the engine which is why Honda put it there in the first place! I really don't beleive the sensor being under "boost" will affect anything. To test this just turn on the ignition and take your sensor and set it on a ice cube. With a digital multimeter read voltage/resistance off of it then take a hair drier and blow it across it from a distance and bring it closer while watching your reading, if the reading goes steadily up then put the sensor in the air box and refigure your timing and air fuel tables and be happy! One other thing, your (our) map sensor, does it have the ability to measure boost? Anybody? Can the ecu use this info? On cars that I have put turbos on I have sometimes had to put in Mopar 2 bar map sensors to get the vehicle to run proper! Dude, when I was finding u some air temp sensor topics my computer crashed and Rich (Hobicus) just fixed it earlyier today. Let us know if this helps. l8tr -Dave Quote Link to comment Share on other sites More sharing options...
demon Posted June 1, 2004 Share Posted June 1, 2004 Well, since they use the RPM - engine speed, MAP - pressure in the intake tract, IAT - temp of the air in the airbox, plus a Baro sensor - Ambient air pressure, they can pretty much calculate how much air is entering a motor through algorhymic (sp?) calculations. Seems to work pretty good since I haven't seen any Mass Air Flow sensors like on most cars on any bikes. Quote Link to comment Share on other sites More sharing options...
MiDNiTXX Posted June 1, 2004 Share Posted June 1, 2004 I'm not sure if the MAP sensor correctly reads the "boost" but the ECU definitely reads it as an error code. Quote Link to comment Share on other sites More sharing options...
demon Posted June 1, 2004 Share Posted June 1, 2004 I would say it does read "boost" up to a point where the ram air is pressurizing the airbox, but the boost from a turbo would be a lot more and it thinks something is not quite right, as it wasn't programed to read high boost pressure. Quote Link to comment Share on other sites More sharing options...
Northman Posted June 2, 2004 Share Posted June 2, 2004 MAF sensors are no doubt more accurate than a speed density system, but you need to plumb an additional sensor, and a MAF sensor would be difficult to fit on a bike. Plus, they're expensive, so manufacturers avoid them if at all possible. MAF sensors usually have the IAT built right in, and some MAF systems use a MAP as well. Cars also run closed loop systems, and are subject to emissions testing, so better metering of the airflow is necessary, or more beneficial to the operation of the system. Bikes run a base map, and alter the fuel curve for different conditions, but don't actually "learn" like a car system does. The IAT seems to have the capability of varying the fuel curve considerably, as this is the sensor the PCII manipulates to add/subtract fuel. Quote Link to comment Share on other sites More sharing options...
XX4me Posted June 2, 2004 Author Share Posted June 2, 2004 The more this gets hashed out the more I think on a turbo application it's better that the sensor see ambient air temp and not actual intake air temp. Mostly because if the intake air temp is rising due to an extended boost session the last thing I would want is for the ECU to start removing fuel causing it to get leaner. Quote Link to comment Share on other sites More sharing options...
Northman Posted June 2, 2004 Share Posted June 2, 2004 It would only lean proportionate the the rise in the temp of the charge coming in, which is exactly what you want. As long as your base map is where you want it, having all of the sensors "active" will help tune the curve for differing conditions. That way, you don't need to alter the map if you take it out on a 60 degree day, then the temp rises to 90 the next. Your fuel curve would be either really fat on the hot day, or too lean on the cool one. Just my opinion, FWIW. :???: Quote Link to comment Share on other sites More sharing options...
XX4me Posted June 2, 2004 Author Share Posted June 2, 2004 It would only lean proportionate the the rise in the temp of the charge coming in, which is exactly what you want.As long as your base map is where you want it, having all of the sensors "active" will help tune the curve for differing conditions. That way, you don't need to alter the map if you take it out on a 60 degree day, then the temp rises to 90 the next. Your fuel curve would be either really fat on the hot day, or too lean on the cool one. Just my opinion, FWIW. :???: Yep that's what I was thinking as far as having the sensor tune the map for varying conditions. Hot day lean it some, cool day richen a bit which it will do in it's current location. Problem I see with putting it where it reads the charge air is if under extended boost the intercooler becomes heat soaked and the charge air temp starts to rise it could lead to detonation if the fuel mixture was getting leaner as the air temp got hotter. This would be even more critical for a non-intercooled turbo application because they might experience larger temp fluctuations. Lets say I installed it in the plenum post intercooler and normal intake temp was 125 degrees at 10 psi boost but I was in the process of laying waste to a Busa, a Gixxer, an R1, et al, so I was running extended boost back to back then intake temp would start to climb due to more heat being absorbed than released by the intercooler. If it went up 50-100 degrees (stretching it here) and the ECU pulled as much fuel out as mine was when the sensor was bolted to the motor then it would change the A/F as much as 1-1.5 points. So from a 12:1 up to a 13.5:1. In the above situation I'd rather have the ECU do the inverse and add some fuel which could be used for cooling the cylinders and valves or hot spots on the pistons. Quote Link to comment Share on other sites More sharing options...
daveszx302 Posted June 2, 2004 Share Posted June 2, 2004 I read what u say and understand your rationall for it BUT I really don't think heat soak is a problem you would ever have since your intercooler is water cooled, I have seen and heard about heat soaked intercoolers in air/air applications but never air/water as water dissipates heat a lot faster than air and your water temp guage is always around 100 deg even after a hard run for your intercooler. Just a thought though, where is your sender at for the intercooler, by your discharge hose off the inter/after cooler or is it by the radiator for it? No, I was not trying to tell you to run a mass air sensor, just trying to state that both systems use a air temp sensor in their configurations. I wish there was a way u could mount an air temp gauge in your air box to test this though. It just seems that u changing your fuel settings every day u ride is useless if the ecu will do it for u with the proper reading for an input but then again I base all of this on automotive ecu's and the problems I have run into installing aftermarket turbos on them, and I have done many of them! I will admit I have no idea about Honda motorcycle ecu's and how much the programing differ's from the Civic's and Integra's I have built. I will also say that I am totally against disconnecting your knock sensor for any reason. I have changed the sensivity of some by removing them and installing a fiber or rubber washer on the base of it but would always leave it in the system. If you ever have a injector clog or plug go out and you were on boost u will wish it was there to cut back timing as pistons can melt VERY fast! Hope this helps. -Dave Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.