Change MPG gauge into Boost gauge

Does anyone know how this would be done? I know that you would have to associate correct voltage with corresponding boost pressure, but I think the MPG gauge is pointless- I know when Im WOT that im getting bad gas mileage. In my 2000 Bonneville SSEI it had a boost gauge right on the display.

 

Anyone know how to accomplish something like this?

You'd need to intercept the CANBUS signal coming from the cluster, then deliver a new CANBUS signal to it.

 

I looked into doing something like that when I wanted my MPG in the digital display to read correctly after modified injectors.

 

I determined it to be a major PITA, and not worth my time.

 

It might not SOUND difficult, but you'd have to monitor ALL CANBUS traffic and pass-thru all but the MPG needle signal (which you'd have to track down). Then you'd have to combine your generated signal with that from the ECU.

holy shit

 

ok

 

maybe if i get wicked bored ill check that out. How would one monitor the can traffic? can that be done with tactrix and a program other than RR/LV

Unfortunately, CANBUS is composed of 2 wires, and ALL CAN traffic goes through them. All traffic. When I did my OE Nav swap, I needed CAN data so I could have the "gauges" work. I T'd into the CANBUS wires for the cluster. I could have T'd them anywhere in the whole car, though, and had the same results.

 

So you'd have to track down the CAN code from the needle. Then stop it going to the ECU entirely, and fabricate a new signal on the SAME code (because

 

At least thats how I understood you'd have to do it.

 

You could do it with an Arduino or something, but boy would it be an awful lot of work to figure out. But once you figured it out, it would be a plug-and-play solution for any car. AND you could use the same module to control ANY CAN feature... sort of.

interesting. I deal with alot of CAN stuff at work, but more on the mechanical side of things and not really the software side.

 

maybe I can figure it out and sell it to all the people on here and become a millionaire. GENIUS!

I'd pay for that

assuming tomorrow is as slow as today was, I am going to talk to the "most" mechanical software guy on my project and see whats good with this. Most of the software guys drive prius's, so this could just be comical

not sure if this is possible, but it sort of plays off your idea OP. how about instead of changing the mpg to show boost, find a way to add boost to the display options as you cycle through the different readings?

 

i like both ideas.

Adding boost to the display options would be nearly impossible, I'd think. You are talking about pixel mapping the whole display. Too much, methinks.

 

Of course, replacing the "throttle opening" chart with boost might be more easily possible. That's my least used info-screen.

 

Again, we are talking about ADDING CAN data that doesn't otherwise exist. I think the first step, would be to modify existing data (make the MPG read correctly with aftermarket injectors). That's a good "get your feet wet" project.

 

I abandoned it after a while, due to lack of time, but I'm certain it's possible.

So I did some more looking, and I found two products that might actually make this work.

 

I haven't looked at datasheets, yet, but the company Kvaser makes a TON of CAN interface products.

 

I think their Leaf Lite HS OBDII module would be the first step.

 

http://www.kvaser.com/index.php?option=com_php&Itemid=258&eaninput=7330130004023&lang=en&product=Kvaser%20Leaf%20Light%20HS%20OBDII

 

That will allow you to receive and send messages on the bus.

 

Then they have their own SDK, which SHOULD allow you to interrupt a signal and replace it with your own return. You'd just need a way to interject a numerical boost value. You could probably pull that from the ECU, actually, and then massage it into whatever format the ECU wants for the gauge. The problem, is that the gauge operates on the average MPG value. Center on the gauge isn't a fixed MPG, but rather your current average MPG.

 

Like I suggested, fixing the MPG display after you've modified the injectors would be a good starting point. If you succeed in that, then the rest is just steps ahead.

 

I DID see something in my searches that looked cool. It was an intercept block that would trigger a relay based on a CAN signal.

 

What was so cool about that, was that you could control relays with CAN signals. And THAT means, that you could wire a cutout to open when you access S#. Or any number of interesting options to be triggered by SI-Drive events.

You probably need to cut the CAN bus cables to the IC and install a repeater there that is transparent for all traffic in both directions except for the specific message that you want to tweak.

 

Of course - if you get a male/female connector pair that is identical to the one on the IC you should be able to avoid cutting the cable.

 

But to make things "interesting" - if you do it wrong you can get all kinds of odd things to happen. Airbags, VDC and other stuff runs on the same bus.

But to make things "interesting" - if you do it wrong you can get all kinds of odd things to happen. Airbags, VDC and other stuff runs on the same bus.

 

this is what worries me about even attempting. Since dailydrivenracecarbro, I cant afford to break shit

Theoretically, you should just be able to plug the CAN back into itself, and all issues would go away.

 

I don't think the CAN can trigger the airbags, it just provides information to control the 2-stage I think. There is still an independent air bag controller.

perhaps I could expose some of the wire and intercept off of that? This is what I do with to make the Oscope trigger off certian messages

 

This is what I use at work to read CAN signals:

http://www.automation.com/images/commerce/thumb/USB-to-CANcomp_Md.jpg

 

This along with an inside program allows me to read and issue CAN commands to the machine at work. Perhaps I could borrow this? I feel like I would need to know the more about the type of CAN signals that the ECU uses

The MPG gauge is connected to the low speed bus.

 

You HAVE to intercept, you can't just read then try to write. If you do that, the ECU will send it's signal following your generated one, and you'd never win.

 

I was talking to a guy who is using a USB-To-CAN dongle to communicate with his Mazda.

 

CAN requests are somewhat simple, and a gauge could be built that will send requests and receive them on the bus.

 

Now that I think about it, the High speed bus (which concerns itself with engine running, the low-speed is the mundane features, like the radio) contains all OBD data IIRC. So that means that you SHOULD be able to read MAP off of the CANBUS.

 

That's exactly what we want to do!

 

You should be able to request from the ECU the following:

 

7E0 8 02 01 0B 33 00 00 00 00

 

7E0 is the arbitration ID

DLC is 8 for CANBus

02 is the # of bytes of the message

01 is for powertrain requests

 

That will give you MAP (0X0B) and absolute pressure (0X33). MAP-AP=boost.

 

The MPG gauge operates off of average MPG, which is on the low-speed bus. So you actually need to do 2 things:

 

1) You need to intercept ALL bus traffic. You need to make the request to the ECU from the high-speed bus here, and receive the response here.

2) You need to modify the result, then output a return on the low-speed bus to the average MPG gauge.

 

How that works, however, I'm not entirely sure.

 

CAN Addresses are one thing, but modifying their content to output to the display is quite another.

 

My best guess, is that you find the request for the MPG gauge, and decode the numeric values while logging under extremes (idle for 0mpg, and engine braking for 100mpg). I think THEN you could calibrate your calculated boost value within the bounds of the gauge (such that straight down is MAP=AMBIENT, far left is some iteration of boost, and far right is some arbitrary peak boost).

 

There is no "set and forget" method for this. It WILL require an external microprocessor. You could test-bed on an Arduino, which has a CANBUS shield available, then build a custom IC once you get the code correct and everything working properly.

 

I have heard of people datalogging using CAN, and the speed with which it reports is absurd. I read one story of a guy logging 100 parameters/second from the high-speed bus. It was pulling data so quickly, it was actually pulling data faster than the ECU was receiving updates.

I determined it to be a major PITA, and not worth my time.

Bingo.

 

It'd be cool, no doubt, but it'd also be kind of silly. With modified injectors, the MPG gauge still reads correctly since it is based on deviation from the mean.

 

The numeric display would be wrong, but the needle would always be spot on giving you relative MPG data.

 

I'd focus my time on fixing the MPG display on the MFI panel.

 

I've also given up on RomRaider/OpenECU and others to begin utilizing the CANbus. They only use K-line and SSM, which means that they are completely useless in modifying the CAN. This is evident by changing the injector size. If the CAN referenced anything having to do with the engine running, the MPG display would change with that factor. It doesn't.

 

The possibility to hard-change the CAN is there, but is it worth anyone's time? I doubt it. It would be different if all sensors were running CANBus. THEN we'd have an easy solution, because it would be forced.

 

I believe cars are going to head in that direction over the next half-decade, where everything will run through the bus.

dude you are wicked smaht

Cars are going wireless LAN instead of wires

I don't see that ever happening.

No, but some are looking at using ethernet.

CAT5 would be more than sufficient for running a vehicle.

 

There are two hurdles to overcome. One is that I don't believe there is sufficient processing power in a standard ECU to be able to operate vehicle controls at the speeds a CANBUS allows. This is, really, a marginal fault. It can be done quite easily, but not quite cheaply. It's like comparing a TI-83 to a MacBook Pro. The TI will get the simple jobs done, but start feeding it complex data at an extraordinary rate and you will stall while the MBP will chug it out without so much as a blink. We are talking about processing rates faster than you can comprehend.

 

We will see CANBUS operated vehicles as Hybrids and electric vehicles become more prevalent.

 

The other speedbump in this development is the sensory input. To go FULL-CANBUS, you'd need each sensor to transmit it's value through CAN signal, which means "smart" sensors and solenoids. This can be done, but durability will be a concern for now. Things are getting better every day, though.

 

As the Green push gets heavier, I expect CAN control will be the only thing that will save the ICE.

this thread has succeeded in blowing my mind

 

http://blogs.dallasobserver.com/unfairpark/Mind%20Blown.jpg

big informative post

 

You are on the right track.

 

The ONLY way to do this is to perform a man in the middle attack on the MPG gauge.

 

This means you have to have a new micro that has (count them) 2 CAN controllers on them. From the MPG Gauge to the outside world you simply pass through and don't modify the data. But messages going to the MPG Gauge you modify the contents to perform your action.

 

So basically, as BAC5.2 pointed out, you override the message to the MPG guage with your own algorithm to scale the boost across the needle.

 

You need to keep any message the MPG Gauge sends to the outside world because if you stop them other controllers that are looking for the MPG module to exist will throw a code.

I don't see that ever happening.

 

I think cars will always use internal networks to communicate within the car, but a wired connection will pose a problem when cars start talking to other cars, traffic lights, and the road.