Can't get stumble out of engine
 

I just got my 13B-RE running on friday and have been playing with the E6K for a few days now. I have a problem where I can't get it to run smoothly under no/light load. At idle it seems to like 5 deg BTDC the best (very little stumbling) but I can't get the stumble out of it for the life of me durring any higher revs. Most noticable ~2500rpm. Plugs are BUR9EQ's Leading and Trailing. Thought maybe I had a bad plug or two so I put a new set in, no change. The timing is zeroed in although it does seem to scatter 2-3 deg, is that normal when using a CAS? Coils are FC and charge time is set to 5ms.

Any advice would be appreciated
Thanks,
-Cam

think if I went to 7's in the leading it would take care of it?

starting to think I'm talking to myself here but anyways..
Put some BUR7EQ's in the leadin gand that didn't do anything. But I did notice while under a slight load the stumbling would go away.

Anyone?

I'm trying to tune my engine right now also. So I know a little how you feel. The only thing I can think of is if it's too rich or too lean.

I adjusted both ways and it only made things worse in each direction. I'm stumped.

could be timing problem. timing should be 100%..... the only time i get a stumble is when it goes full rich or full lean. like mentioned earlier. time to buy a wideband :)

I am having a little stumbling too,very small. Could you post a datalog?

if the hotter plugs(7 vs. 9) are helping then the mixture is rich. what diagnostic devices do you have attached to this engine? EGT, AFM, UEGO, etc? if you are doing this by feel then you will never get anywhere. timing should not move. check that the timing is not moving when it stumbles. check all wiring connections and route all CAS wiring away from plug wires and alternator.

Thanks for responding tims.
Doesn't really matter what plugs are in it.
Don't have a diagnostic device. What I would do is hold it at 2000rpm and adjust fuel in both directions. You could hear it start to lean out and richen up when I did this, the stumbling would only get worse in either direction.
Have checked all connections but the alternator wiring does run close to the CAS wiring, I'll have to move that.
Should the timing hold rock solid?? Mine probably jitters maybe +- 2 deg at idle with it locked. I blamed this on the CAS gear clearances but maybe it not?

1revvin7- can't post a datalog because my home computer is a iMac :(

first you cannot tune the engine without load. reving it in the garage is not going to work. timing should be very solid. mine moves about +- one line width<1* either direction. once off idle it is solid though. second doing any tuning work without some type of tool(egt,afm,etc) is a recipe for disaster. if you are going to do the tuning yourself invest in the best guage(tool) you can afford and learn how to use it. or else rely on someone with experiene to tune it for you.

I wasn't reving it and trying to tune it that way. I would hold it at a constant rpm and adjust fuel in either direction to try to eliminate the possibility of the stumble being caused by over/under fueling. What I did that seemed to help a lot is bump the timing down. The map I have here was up to 36 BTDC in some ranges, I bumped it down to a max of 28 BTDC. At idle I have it set to 5 BTDC I think it was up to 19 BTDC.
Do you have a CAS in your 13B or the FD style trigger? Once mine is off idle mine is solid also, I just thought it was strange that it would jump around that much at idle (+- 2deg).

I am using the seconf gen CAS. as long as off idle is solid you should be fine. I keep max timing at 24*. this seems to work best on my engines. 36* sounds like way to much.

Setzep, toss me an email at home -> bdc196@attbi.com. I'll get you situated and fixed up when I get back to the house.

B

With the help of BDC and this WBo2 meter I have here I almost totaly eliminated all stumbles! :) It's amazing what the WB meter will tell you that you can't even come close to feeling/hearing. More tuning for tomorrow to get my AFR's exactly where I want them (little rich in bars 9-11 right now)
Thanks for all the help guys!

you have to have the correct tools for the job. good to hear it is working better.