Another MS conversion, Progress, at last. Options

[JimN73]

(IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif)

Well, the MAF solution that we were hoping for didn't work as planned. The engine responds much better at low rpm, but still bucks (buck downgraded to lurch since it's not as severe). Acceleration from stop is really good. Mark is looking at an AAR that may help.

Thanks to Mike, kg6dxn, for helping me tune after Mark got the MAF in.

Although sensitivity to cam overlap is still high on the list of culprits, Mike and Mark both think that the lightened flywheel may be contributing to the problem.

The flywheel is not the only lightened component:
I used AA H-rods, they are only 2/3s the weight of stock - a pretty savings. The pistons are also lighter than the 94s that I took out.

[VaccaRabite]

The 9530 is mild enough to drive CIS. MS can drive huge overlap drag cars. I have no doubt this can be tuned.

[JimN73]

If that's the case, and I thought it was, I have another problem that no one can even imagine.

[VaccaRabite]

Get on the MegasquirtII forums. Post your logs and your complete setup. Someone will probably see the problem or start a line of questions that gets you closer. If there is a shop nearby that specializes in MSII engine management - same deal. They may be able to see the issue.

As you said, you have already tuned out most of the studder.

I also agree that the lightened parts are playing a bigger role then the cam. But MSII drives all sorts of cars with lightened parts. Tune it out!

And then post about it here, as I will be doing the exact same thing this spring.

Zach

[904svo]

(IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif)

Well, the MAF solution that we were hoping for didn't work as planned. The engine responds much better at low rpm, but still bucks (buck downgraded to lurch since it's not as severe). Acceleration from stop is really good. Mark is looking at an AAR that may help.

Thanks to Mike, kg6dxn, for helping me tune after Mark got the MAF in.

Although sensitivity to cam overlap is still high on the list of culprits, Mike and Mark both think that the lightened flywheel may be contributing to the problem.

The flywheel is not the only lightened component:
I used AA H-rods, they are only 2/3s the weight of stock - a pretty savings. The pistons are also lighter than the 94s that I took out.

Have you try to used Tunerstudio to tune it? That will show you where the problem is. You must have a WB O2 sensor installed, this is what I found when I used a MAF.

[VaccaRabite]

Btw, the overlap period for the 9530 is 73.72 degrees.
This is found using the LSA (lobe seperation) methode.

Using the more common method indicates an overlap period of something like 118 degrees. Which is drag race territory and clearly incorrect.

The fromula for LSA overlap measurement is:
(((In duration+ex duration)/4)-LSA)*2
All those variables are on the cam card.

I don't know why the standard methode (intake open + ex close) gives the wrong number. Maybe pancake cams don't work for that calculation.

[Chris Pincetich]

For what it's worth (Not much) I have adjusted for a high idle on my 1.7 D-Jet to make the light flywheel more "drivable". With a low idle, the engine dies if I let the revs drop quickly when not warmed up. I also need more "revs" to get off the line from a start (w/o killing engine) with the light flywheel. Good luck! (IMG:style_emoticons/default/beerchug.gif)

Finding the "balance" of building a hot-rod AX 914 and having it pleasant for daily driving is not easy! (IMG:style_emoticons/default/happy11.gif)

[JimN73]

(IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif)

Well, the MAF solution that we were hoping for didn't work as planned. The engine responds much better at low rpm, but still bucks (buck downgraded to lurch since it's not as severe). Acceleration from stop is really good. Mark is looking at an AAR that may help.

Thanks to Mike, kg6dxn, for helping me tune after Mark got the MAF in.

Although sensitivity to cam overlap is still high on the list of culprits, Mike and Mark both think that the lightened flywheel may be contributing to the problem.

The flywheel is not the only lightened component:
I used AA H-rods, they are only 2/3s the weight of stock - a pretty savings. The pistons are also lighter than the 94s that I took out.

Have you try to used Tunerstudio to tune it? That will show you where the problem is. You must have a WB O2 sensor installed, this is what I found when I used a MAF.

Yes, we do use TunerStudio. I will try to get some meaningful logs this week and post the tune that we're currently using, and I'll switch back to MAP and log that, too.

thanks for the input.

[JimN73]

Here is the tune file that I'm using and a log file from a recent test run. The log file starts out idling, accelerates in low gear and shifts to 2nd.

Then the fun begins, you can see the bucking. It's interesting that the throttle position closes, but I have't taken my foot off the gas pedal. Is the TPS causing the problem or is it the effect.

The engine is a 2056 type IV with a 9.5:1 compression ratio and Raby's heads. Has Raby's 9530 cam (Web's Cam #494), lightened flywheel and other lighter components.

https://www.dropbox.com/sh/p593bw6iyebgwjn/bANp3X25ic

Any help figuring this out will be appreciated by me and by those who will follow.

[904svo]

Check your grounds to the sensors you are getting voltage spikes in them. Remember they must go back to the Megasquirt to a common ground. Also
check your WOB heater ground it must be seperated and run to the engine.

[Dave_Darling]

Throttle position closing when you haven't taken your foot off the pedal is very suspicious. Sounds like sensor issues, which you will never be able to tune around. Check all of the input signals you can against what you would expect them to be--in particular, be suspicious of sudden changes during relatively stable inputs.

Checking grounds like SVO says is always a good idea. Might be worthwhile to set up a dedicated ground circuit for the sensors if you can. Even if it's just sandwiching a wire or a loop connector in between the mounting screws or whatever.

--DD

[McMark]

Yeah, it's looking like there is a noise issue. I guess I didn't look close enough at the logs because the RPM vs. Time changes recorded are physically impossible. We'll have to see about shielding the VR sensor wire as a first step.

[904svo]

Mark the best way to trouble shoot your problem is to make up a external tooth wheel and run it to the VR sensor. Turn off the fuel pump first!!!!! You can now look at all the signals and disconnect them one at a time to find your problem. Thats what I did.

[McMark]

That's a good idea. I'm going to try shielding the VR sensor first because this harness was a prototype and doesn't have the same shielding rwilner's harness did.

[karlo]

You may be looking at a sensor issue, but the MAP and RPM readings you are seeing in the logs make no real sense. I would upgrade the firmware to MS2Extra (http://www.msextra.com/forums/viewtopic.ph...101&t=43433). I find it more robust and easier to tune, and it's the default firmware for the MS3 in any case. I have tuned somewhere around ten cars on Megasquirt, and I've never bothered dealing with the stock firmware.

The only thing I know is a little hard to tune is throttle bodies with big cams, but as far as I understand, you're not running throttle bodies?

Feel free to PM me if you have questions (I'm in San Diego these days).

[JimN73]

Good stuff. Thanks to you all.

Sometimes having the prototype is a bit tough, but I'm sure Mark is sorting the process out and will have something to test pretty soon.

We'll keep you posted.

[rwilner]

Mark
I looked at the log. Is the signal ground separated from the dirty (engine) ground? If not, that could be the source of the problem.

For the cleanest signals, the signal ground and engine ground need to be tied together in only one place -- inside the microsquirt, which they did on the PCB. If they're tied together anywhere else you'll create a ground loop.

It's easy to test if the grounds are tied together outside the microsquirt. Pull the connector at the MS and test for continuity between the signal ground pin (20) and the power ground pins (21 thru 23).

good luck and feel free to call me if you want someone to bounce ideas off of.
Rich

[JimN73]

Progress today. Mark got a VR sensor with a shielded wire installed. Didn't have to remove the engine.

Still left a bit of noise that causes some bucking generally at 1400 rpm - give or take.

He's looking into a couple of solutions and should have something in a couple of weeks.

[JStroud]

Glad to hear you're getting it sorted out Jim, Still plenty of time before ax season. (IMG:style_emoticons/default/driving.gif)

Jeff

[McMark]

Actually, it'll drive better at the AX than on the street. Since if you're cruising at 1400 at an AX, you're doing it wrong. (IMG:style_emoticons/default/laugh.gif)