Aprilia Trouble, opinions wanted!

[Aaron@Kaist]

Dear FSAE members,

with advice from some fellow FSAE'ers, we finally got our aprilia SXV 550/walbro/tune boy set up to fire up. However, the engine stops exactly after 10 seconds like clock work. We bypassed the tilt shut off sensor hoping that was the problem, and tried various AFI ratios for idle to see if that would work, but nothing seems to be the solution for this problem. Does anyone have any insight on why this might be? Also, if any of you guys are using tuneboy, any idea how to connect the tuneboy diagnostics to the ECU? nothing seems to work. Thanks all, hope all of you are having fun preparing for comp.

Aaron Park
KAIST

[Aaron@Kaist]

Dear FSAE members,

with advice from some fellow FSAE'ers, we finally got our aprilia SXV 550/walbro/tune boy set up to fire up. However, the engine stops exactly after 10 seconds like clock work. We bypassed the tilt shut off sensor hoping that was the problem, and tried various AFI ratios for idle to see if that would work, but nothing seems to be the solution for this problem. Does anyone have any insight on why this might be? Also, if any of you guys are using tuneboy, any idea how to connect the tuneboy diagnostics to the ECU? nothing seems to work. Thanks all, hope all of you are having fun preparing for comp.

Aaron Park
KAIST

[Erich Ohlde]

is the engine running or cranking when it stops. In an effort to save starters aprilia put something into the ecu that limits cranking time.

[Drew Price]

Maybe a safety circuit that's turning the fuel pump off? That's be easy to check by putting a voltmeter across the pump terminals (if it's actually starting and idling for 10 seconds, like Erich asked). Like if it's not seeing the tach signal correctly?

Or some kind of warmup enrichment cycle the completes at that # of revolutions, and when it switches to the run parameters they're not close enough to keep it running?

Sorry, I don't know the TuneBoy system, but MegaSquirt has something like both of those as selectable options, so they jumped out at me.

See if you can figure out what is causing it to stop, if it's spark or fuel, that should help troubleshooting.


Best,
Drew

[Kemper]

we found out the problem. I don't know how many teams use Aprilia and Tuneboy, but just for reference in case someone suffers with that here goes the explanation:

There are two maps on the stock ECU (Walbro): one for running the engine and other only for starting. The starting map is used on the first ten seconds, then it its swapped for the main one. What happened is that we had kinda messed-up with the trim maps (waaay too lean), but as it was starting we didn't figured that out. It started, but when it swapped to our map after ten seconds it just died.

Now, one thing that we found out is that the stock maps (both starter and main) work pretty well under 3000rpm, and we have to lean it out gradually after that. Is this normal for the other engines as well?

[Erich Ohlde]

the tuneboy starting map has really small numbers. are they a injector pulsewidth of running map or what?

[kapps]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kemper:
Now, one thing that we found out is that the stock maps (both starter and main) work pretty well under 3000rpm, and we have to lean it out gradually after that. Is this normal for the other engines as well? </div></BLOCKQUOTE>

Are you talking about leaning out a pre-made map or just that you've found that the injector pulse width drops as rpm's increase? Either way, as rpms rise (and influence of the restrictor increases) you will find that injector pulse width will drop. The faster the engine spins, the faster you're trying to suck air through that tiny hole. You won't be able to fully fill the cylinder with air so you won't need as much fuel to provide complete combustion. I only have experience with the F4i but for us, that was around 7k rpm. 3k rpm sounds low but I have no experience with that engine.

[Ale_ET]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> There are two maps on the stock ECU (Walbro): one for running the engine and other only for starting. The starting map is used on the first ten seconds, then it its swapped for the main one. What happened is that we had kinda messed-up with the trim maps (waaay too lean), but as it was starting we didn't figured that out. It started, but when it swapped to our map after ten seconds it just died. </div></BLOCKQUOTE>

Are you sure????
We use Walbro ECU for our engine. It's a specific FSAE Walbro ECU. I haven't seen these 2 maps! There are 2 blocks, 0 and 1, but they are 2 different maps. You can switch during competition.

Are you checking engine temperature sensor?
Read here:
HEATING COUNTER: This is the maximum value that the Starter Heating Counter is enabled to reach in order to avoid overheating of the Starter itself. The Counter is incremented every 10ms during crank and decremented while engine Stopped or Running according with values setting on HEAT_INCREMENT and HEAT_DECREMENT variables. On matching this value the ECU will switch off the ECR Relay untill the counter will decrease to 0.

Here http://www.athena-spa.com/ecu/prodottie.html you can find Walbro model and software to interface with your ECU.
Use the 3 wire (RX, TX and ground) to interface with a 9 pin serial port PC.

Bye!

[Wesley]

The tuneboy meters fuel in reference to "milligrams of air," in other words, you tell the tuneboy how much air gets in the cylinder, and it meters your fuel based on desired AFR.

The actual pulsewidth value should increase to some point (usually at your VE peak) and then fall as it tapers off. With the SXV, I'd expect it to increase.

[Kemper]

@erich
As Wesley said, the units on Tuneboy tables are "miligrams of air", so I guess what:
option 1: the small numbers state is that the engine sucks less air on the start (?).
Or option 2: is just a way to limit the amount of fuel going in, since you tell the ECU that not much air is going in so it wont put more fuel.

Putting in less fuel during start routine makes more sense after you read this thread (it did to me, at least): http://fsae.com/eve/forums/a/t...607348/m/39510557341 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/39510557341)
The way Aprilia's ECU figure out the right firing sequence by trial and error. I would guess that misfiring a big amount of fuel/air mix in stoichiometric conditions could be a potential damage to an engine that uses such "trial and error method". This would explain small numbers on starter map.

@kapps

I guess our plenum is waaaay too small, so the restrictor kicks sooner. But fluid dynamics is not my best subject... hehehe

@Ale_ET

Yes, I'm sure about the starter map. It comes on the Aprilia SXV 550 stock ecu (Walbro ECU-C1). As we are using Tuneboy to re-map the ECU, we get access to those maps. We did several tests before concluding that the starter map is the one valid for the first 10 seconds, then the other maps.

Now, I heard about the 2 map features on Walbro ECU. The question is, how to switch between different maps on the go? Could you share that infos? We still have a little bit of time to prepare a new map before sending to West...

(thanks for the other infos on Walbro, thou)



Wow, good to see information on Aprilias! Hopefully next teams will have less trouble. By the way, thanks to Wesley and other guys we managed to kill only one starter before reaching the 1-touch-start level.

Does anybody knows how many Aprilias are going to West 09?

[Ale_ET]

Ok, ok! If you use the original Walbro ECU you have 2 maps (one for the crank), that the system switches automatically.

We use a special FSAE Walbro ECU, the H1SAE_1. With this ECU and its software, you can modify all parameters and there are functions as gear cutoff, traction control, and other.

About switch maps, it's possibile to create two different maps with software. Both maps are loaded on the ECU and with a simple switch you can chose the favorite map (during running engine too).

Now, we're modifying the entire maps on the dyno because we've changed completely intake and exhaust system!

If you need some information, I'm happy to help you!

Bye,

[Grant Mahler]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kemper:
The way Aprilia's ECU figure out the right firing sequence by trial and error. I would guess that misfiring a big amount of fuel/air mix in stoichiometric conditions could be a potential damage to an engine that uses such "trial and error method". This would explain small numbers on starter map.
</div></BLOCKQUOTE>

Saab has done this on production vehicles for some time. I don't think it is done anymore. Look at the mid 70s to early 90s Saab 900/9000s if you want more confidence that this isn't an issue on startup if done correctly.

Also, I know of at least 2 other motorsport ECUs that do this.

Switching between the two maps you would hope there is some interpolation or at least a check and not just a time or or number of revs, though I have never used that specific setup and have no idea how it works.