The MegaSquirt Project has experienced explosive growth other the years, with hundreds of new MS installations occurring every week - a phenomenal success! MegaSquirt has been successfully used in all aspects of Internal Combustion engine applications including R&D, Industry, Race, and Research. The MS project has transformed itself from a simple R&D project into a full-featured mature engine control system. To reflect this the support structure has also changed to meet the needs of MegaSquirt Users.
Moving forward, the R&D forums for MegaSquirt project are in a read-only mode - no new forum posts are accepted.
However the forums will remain available for view, they still contain a wealth of information on how MegaSquirt works, how it is installed and used. Feel free to search the forums for information, facts, and overview.While the R&D forum traffic has slowed in recent years, this is not at all a reflection of Megasquirt users, which continue to grow year after year. What has changed is that the method of MegaSquirt support today has rapidly moved to Facebook, this is where the vast majority of interaction is happening now. For those not on Facebook the msextra forums is another place for product support. Finally, for product selection assistance, all of the MegaSquirt vendors are there to help you select a system, along with all of the required pieces to make it complete.
For discussing how to choose sensors and create a wiring harness for all Bowling and Grippo versions of the MegaSquirt® EFI controller.
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I am planning to install a MicroSquirt on a LSR specific 1000cc turbocharged Sportster. My concerns relate to placement of the O2, MAP, IAT, and a head temp sensors.
I should add that the sensors have to fit the as-built.
Can people see this? Sam may not be able to post pics.
My concern is the temp on the o2 sensor that is soo close to the exhaust and the turbo. Keep in mind that this is a top speed car so exhaust temps are a real issue. Eric, Geek, Bruce ... any help would be great. The Harley guys are a little over their heads.
Well, you've certainly got some challenges there...
I think you're screwed on the O2 sensors. If you put it in pre-turbo, it's going to fry pretty quickly at wide-open throttle and post-turbo there just isn't enough room to keep the exhaust gasses from getting contaminated with raw air. So, you'll have to do mixture control the old fashioned way, reading plugs and all that. (Get an expert to help tune it, Andy has already mentioned one above: dieselgeek aka Scott Clark.)
MAP should be easy, just plumb in anywhere after the throttle plate. Are there any ports in the casting at the cylinders? That would be as good a place to tap in as any.
IAT should be somewhere after the intercooler, I don't think you have to worry about heat soak of the sensor as it should equilibrate quite quickly with large throttle openings. Placing it in the outlet tank of the IC might be good enough, near but not occluding the outlet would be a good place as it won't impede flow.
CHT is typically used just for warmup enrichment, so do you even really care about this? I would normally suggest one of those little spark plug washer sensors, but on a race engine you will be popping plugs out all the time and it would break sooner rather than later, so I'd suggest getting a thermistor sensor from an air-cooled airplane engine and tapping one of the fins on a head and installing it there. Or better yet, just short the input with a resistor to indicate full temp and then suffer with the lean mixture while you warm the thing up... (No CHT sensor = less junk vibrating on the head, so one less thing to break.)
Oops, forgot to ask about mixture balance. I see from the turbo that you have already run this engine, so how do the plugs look? Does one cylinder steal charge from the other? Got any idea how much?
How far should an O2 sensor be from the head?
How about using a wide band on the rear clyinder and a narrow band on the front (if it will take the heat)? The idea being to use the NB as a double check of the WB, not as a tuning input.
I had it running on a carb just long enough to verify it does run and roll. Plug readings are ~close~, but not identical. Doing plug chops is not gonna be easy; most LEO's would not understand....
I don't remember the operating temps for O2 sensors (but Bruce has a mind like a steel trap on this stuff, I'm sure he could recite it at the drop of a hat), but if you want to datalog runs, I don't think anywhere in the pre-turbo exhaust plumbing is going to be safe. For tuning, I'm pretty sure you could do 10-second long pulls on the dyno and not destroy the sensor (well, at least before you got some good info out of it), so maybe install one (or two) for tuning and then pull them out for racing? As tuning-only devices, I'd put them up close to the port, so as to get good response and separation for the two cylinders.
I believe the sensor failure due to heat will affect both NB and WB sensors identically (if they are both, say, Bosch parts, they'll likely share substrate materials).
Just got off the phone with a Bosch application type. He didn't think reversion would be a problem in a steady state operation, but 400 deg C is what the sensor wants. It will take excursions to 950 C, but for only a few seconds.... I'm betting EGT exceeds that real quick.
Are there any other options for real time feedback?
Looks like my sensor list is down to MAP and IAT?
Sam
LEO: Law Enforcement Officer
Dyno: 3 miles of public highway
Here's the datasheet for the Bosch LSU4 (page 5 has the specs that may be most pertinent for your project). You may not be in all that bad a shape especially if you heatsink the sensor's mounting and can find the "Inconel protection tube" version of the LSU-4.
Link: http://smrmicro.com/Bosch_20LSU4_english.pdf
Eric,
How about another angle; view the O2 sensor the same as a spark plug. Toss after every pass. Manufacturer data lists extreme testing and repeatable excursion parameters; i.e.; it's gonna fail. Because I haven't toasted sensors in my motor, it's unknown how long they will last in my application.
As an O2 sensor fails under load, what is the parameter that changes? Can it be tracked by MS? If dectected, fall back to the something "safe"?
Hmm, good question regarding failure mode. I always thought it was just catastrophic failure (for example, the ceramic substrate just fractures or melts down). Like Mike says, you can shield the sensor in the pipe and make it last longer (but I suspect you are compromising response times when you do so).
Eric, you bring a valid point re the response time. I certainly wouldn't want to utilize a shielded sensor's output for a time sensitive (AE for example) tuning project. If load/RPM steady state tuning were being performed I would think that a slower response would be OK. I'm trying to remember where I read/saw/heard that the failure mode for typical WB sensors was similar to NB sensors in that response time rises until complete failure occurs. (?) Your observation that Bruce would probably know all the answers to these questions in his sleep is probably correct...
Been reading up on EGT on Landracing.com. Seems any application where EGT nears 1500 F, folks start looking to back off the heat. Since this is within the operating range (barely) and only for a short duration (3 minutes), a planar 4 wire is in my future. A K thermocouple within an inch or so of each exhaust port for backup.
Now, I have to finish the airbox so I can fit the MAP and IAT.
Out of curiousity can I ask if this a fuel-only or fuel and ignition install? What are you using for the tacho input?
efahl wrote:Oops, forgot to ask about mixture balance. I see from the turbo that you have already run this engine, so how do the plugs look? Does one cylinder steal charge from the other? Got any idea how much?
I have a similar engine (Buell motorcycle) that has stock EFI. With both cyls getting identical PW from the stock ecm (sequential), the rear is running a fair bit richer than the front. When MS was running the fuel 2 squirts sim on the other identical bike I don't recall seeing such a difference at all. I only just got 2 x O2 bungs fitted, one in each header, to check this out further.
Ian,
I'm planning on fuel only at this point.
I have a stock '91 ingnition. I'm using the tach output.
I also have a PowerArc to install when I get closer to done.
On the 2004 Buell the tach output is odd-fire, so if the '91 ignition module has a similar output then you might need to use some odd-fire averaging code. Hopefully you have an even pulse train from the '91 ignition. On the Buell (which I admit may be very different to the Sportster electronically, so this info is just in case) the tacho output signal from the ecm was barely capable of driving the optocoupler in a standard MS box, so I connected it to the base of a 2N2222 with a 4K7 resistor and a 1M bias resistor to gnd, this worked very well, the tranny was switching the 5V via 4K7 resistor instead of the optocoupler to feed the tachin pin of the processor. Good luck with your project, good to see.
Ian,
I wrote PowerArc and asked about the tach signal.
"current limited 12V squarewave" was the reply.
Sounds good to me, but I haven't your experience.
If you fire the engine up with the carb again it might be worth hooking up an LED and 470 ohm resistor to the tach output and see if it flashes. At idle you might be able to detect if it is odd-fire or not. If it will drive an LED, then no problems driving the optocoupler. If it doesn't drive the LED though, maybe buy another opto and connect that to the tacho out and see if the opto will then drive an LED. Better to get details worked out sooner rather than later, says he who can barely follow his own advice : )
