V-twin front cyl runs much hotter than rear--- Why?

[Norzilla]

Hi

I am having some issues with the 60 deg V-twin Aprilia RSV1000 engine that I am running on Microsquirt.

The main issue / concern is that the front Cyl 1 has a stronger power pulse than the rear cyl 2, it also runs at a much hotter exhaust gas temp (60-80degC) measured at the same point on the pipe 1" from the exhaust outlet flange at an idle of 1500rpm. I am running 2 seperate exhaust pipes, but only have 1 o2 sensor running off the back cyl. I have set the idle AFR at 12.5.

http://taimoshancycleworks.com/tcw/wp-c ... acer11.jpg

You can see the engine layout in the photo.

I have tried splitting the fuel maps in 2 , 1 front and 1 rear and running richer mixture on the front and it does not much any significant difference.

The other cause I thought was that not enough adv on the front cyl causing it to run hot, but there is only 1 spark map so can't change this paramater.

Is it possible that I have the baseline timing points wrong ? and how could I adjust this?

Anyone have any ideas?

Cheers
Norzilla

[grippo]

Are you running wasted or sequential ? If you are running or can run sequential, then you could change to 3.x code and get individual cylinder fuel and spark trim.

Since you have tried using the dual table option to change the fuel trim with no improvement, then it might be the fuel timing rather than quantity, especially if you have an odd-fire engine. If on one cylinder its all going through the exhaust during overlap, then increasing fueling is just dumping more fuel into the exhaust. You can test this by changing the Injection Start % and move the timing to better equalize the 2 cylinders. You can't change the individual cylinder timing, but you might be able to find a spot where both cylinders are happy. In 3.7x code, fuel timing takes into account the odd-fire angle, while in previous 2.x code it assumed an even-fire engine for purposes of injection timing.

The other possibility is that spark timing is off. First I would confirm timing is correct by timing each cylinder individually, using 2 separate marks on the timing wheel for TDC 1 and 2. If the timing is not the same and/or not correct, then it is a configuration problem - either trigger offset or the odd-fire angle is wrong. If timing is all correct, then you could still move the advance to try and make the problem appear on the opposite cylinder. For that matter you could move the odd-fire angle and that should only affect spark timing of the second cylinder.

[24c]

I would expect any engine with your type of configuration to run hotter on the back cylinder, so the fact that it doesn't, does suggest a mistiming of fuelling events or a difference in ignition timing as Grippo suggests. A few months back, I lent an original Aprilia exhaust can for a Mille to a garage mechanic, because he complained the bike wasn't powerful enough! He thought the straight through pipe was responsible, but when the guy came back after a test ride, I noticed the rear cylinder exhaust wasn't hot, so he should check the plugs first.

The next day he checked & the plug cap wasn't attached and hadn't been for weeks, so that's why it was a gutless, it had a one cylinder engine!

[Norzilla]

Thanks for the input Grippo and 24c,

since posting and before reading your responses, I started adjusting the timing of the oddfire offset from 60deg back to 55 and upto 65 (about 62 seemed the best position) at 65 the bike kicked back on start and broke the sprag clutch so I am waiting on the new parts before I can test further, but as I will have the timing side cover off, I will be double check the TDC 1 & 2 marks and ensure that the offsets -60 & oddfire offset at correct. Another issue that I have been trying to resolve is the when I blip the throttle as the revs drop back to idle the engine dies, but I found that changing the ignition predictor alg from alpha-beta-bamma to last interval solved the problem and created a more stable idle. Could this be a related issue to a possbile misalignment of the TDC 1 & 2?

I also did try adjusting the injection timing which had previously be set at 26% which had historically been the position creating what i felt was the smoothest idle but I will explore further after checking the timing marks and seeing if I can get the stronger pulse to swap to the back cylinder.

I will keep you posted once I get the new parts installed.

Grippo, sorry to ask a somewhat dumb question, but can you send me the correct link to download the 3.7x version of the software for my Microsquirt?

Thanks again
Norzilla

[grippo]

If the timing of both cylinders is correct at idle and also at a higher rpm without a load then it should be good everywhere under all conditions, assuming there is nothing mechanically wrong. So if you can establish this, we rule out trigger offset or odd-fire angle being wrong.

The alpha-beta-gamma predictor is really not needed if you have a toothed wheel setup with a decent number of teeth - like 12-24 or more. But prediction is much more sensitive to error at slow speeds rather than high speeds so I'm not surprised if it affected idle.

As far as the new code, its not a dumb question, the code isn't out there yet, I was waiting for release of the new microsquirt. I can give it to you, but as I said, it won't help if you don't have sequential cam sync. You can't trim an individual cylinder unless you are sure which cylinder you are trimming. Also, there are quite a few changes that may mess you up if you load your old msq. But I am glad to have a tester, so let me know when you are ready to try it. (I would try to verify the spark timing is correct first.) If I get your msq, I can sort those problems for you and give you back an msq that will work with the new code.

[Norzilla]

Ok, I have had the timing cover off the bike today and double checked the accuracy of the timing marks for TDC Cyl 1 & TDC cyl 2. They are what i believe are correct. ( See attached scan of the Timing diagram of timing events )

NB the engine is running a 36 tooth wheel with 2 missing teeth. There is also a single cam trigger to ID the front cyl event ( Cyl 1), it is positioned as per the timing Diagram. I am also running sequential injection for fuel not batch injection.

I have also attached the MSQ that I was using when the engine kicked back and broke the sprag clutch. I hope I have not made and obvious mistake

I am happy to test the new code and give feedback.

Thanks
Norzilla

(while you are looking at the msq can you take a peek at the accel enrich map and see if it is in the ball park, as when the bike was running i think it felt a bit boggy, maybe too much fuel in accel enrich ? if so what is the best protocol for set this area? Thxs. Norzilla)

[grippo]

I will try to take a look at this tomorrow.

[Norzilla]

I have been staring at the timing Dia I drew the other day of the timing events and the only thing I can think is that because the TDC for 1 & 2 appear on the trailing edge of the tooth 25 & 31 and not the centre of the tooth, that there is a 2.5 deg difference in the the timing ie the timing is over advanced by 2.5deg, which may explain the kick backs as the cranking and low rpm timing would be 2.5 deg more than it shows on the Ign map.

This might be a big downside of not being able to put a timing wheel and a strobe light on motorcycle engines you can't tell if reality = computer.

Any thoughts? also anythings one how to fix?

[dontz125]

Is there not a 'timing port' on the side of the bike, where you can unscrew a plug and actually see the stock timing marks?

[24c]

Norzilla, you've possibly see this manual for the earlier bike, but it's still useful info.

I had a quick scan and haven't seen a timing window...yet