timing off (pops, etc) - ideas on this map? (pics)

paulc · Post by **paulc** » Sun Aug 16, 2009 2:08 am

first, I took the car for my first drive today! very exciting... Everything seems to be working fine (I built the car from ground up!), so no fires, shorts, loose bolts, squeels, etc.

My timing is off however and i am an ultra newbie when it comes to fine tuning this via MJ.

the engine is a 2L air-cooled Type 4 VW motor (914 and buses came with these). Internals are stock, performance mods are bolt on (dual Weber 44mm carbs, sidewinder header, etc).

when it's cold, it runs perfect.

when warm, it's sputtering under load. It idles like a champ when warm. starts up fine.

because i am so new to this and to be honest, don't fully understand timing that much, i figured you guys would have suggestions for me to try rather than me driving up and down my (quiet) street for hours tuning it.

so... here is my map:

dave9469 · Post by **dave9469** » Sun Aug 16, 2009 12:21 pm

Hi Paul

A number of things spring to mind, first the bins need setting up. On a normally aspirated engine you will not get over 100 Kpa. This is atmospheric pressure at startup. We need to understand where your vacuum take of is because I'd expect a figure a little lower than 70 at tickover with closed throttles.

If you note what value you get with a wide open throttle and closed throttle then the load bins can be adjusted to within this range.

Similarly the RPM bins need setting up to your engines rev range.

Because of the way the map is setup currently you only have RPM advance and no vacuum advance because between 20 and 70 the advance is the same.

Can you explain 'sputtering under load'? I assume you mean spluttering. If the advance is too high under load then you'll get pinking/knocking which I would expect with your current map but spluttering could be a fuel issue which shouldn't be ignored with a completely new build like yours.

Hope this helps

Dave

paulc · Post by **paulc** » Sun Aug 16, 2009 4:21 pm

wow - that fills in a lot of blanks - thanks Dave.

i took a look through the ignition map files and found dannyP's. his is NA and about the same setup.

after looking at that config - it started to make sense.

I tried his map, and it still isn't right. the off idle response is great, but any under load (up hills, etc), it backfires, etc, so i know the timing isn't correct. I got it idling at just over 500RPM (i heard my fuel pump relay (connected to one of the user outs) switching on and off.

so, if i adjust the RPM bin to match my engine (500-6000RPM) and the KPa to be a normally aspirated motor (up to 100KPa), where do i adjust for load ?

NITROPIXIE · Post by **NITROPIXIE** » Sun Aug 16, 2009 6:51 pm

Don't forget you will get an increased vacuum when deccelerating so it is advisable to put an extra bin in for this case although not entirely necessary.

paulc · Post by **paulc** » Sun Aug 16, 2009 10:16 pm

I'm not sure i completely understand what you mean NITROPIXIE. Could you please explain it a bit more?

I've edited the bins for Load / RPM.

here is what i have so far:

I did some poking around and saw this distributor curve map ("205" is the type of distributor MJ replaced)

NITROPIXIE · Post by **NITROPIXIE** » Mon Aug 17, 2009 8:45 am

Ok if we take the pic on your first post and we say that the car is idling at 1057rpm and is creating 70 KPA vacuum as the throttle valve is completely closed. Now consider the car deccelerating from say 3000 rpm with the throttle valve completely shut. The engine will now create more vacuum say 50 KPA as the engine is sucking more being at a higher rpm.

If you don't add an extra bin for this event then an engine can pop during decceleration.

paulc · Post by **paulc** » Mon Aug 17, 2009 8:44 pm

is that normal to have 70 KPa at idle?

edit: i played around with the mapping.xls file that was loaded into the library and it came out with this map (very different than default and danny's)

mapBins=19,28,38,47,56,66,75,84,94,103
rpmBins=6,11,17,22,28,33,39,44,50,55

advance0=18,21,24,27,30,34,37,40,43,46
advance1=17,20,23,26,29,32,35,38,41,45
advance2=15,18,21,24,28,31,34,37,40,43
advance3=14,17,20,23,26,29,32,35,39,42
advance4=12,15,18,22,25,28,31,34,37,40
advance5=11,14,17,20,23,26,29,33,36,39
advance6=9,12,16,19,22,25,28,31,34,37
advance7=8,11,14,17,20,23,27,30,33,36
advance8=6,10,13,16,19,22,25,28,31,34
advance9=5,8,11,14,17,21,24,27,30,33

paulc · Post by **paulc** » Tue Aug 18, 2009 3:18 am

well, i tried logging a trip up a hill and back. the timing is waaay off (could barely make it up the hill).

I've never logged before, so i am hoping someone can help decipher this screen shot.

Broke4speed · Post by **Broke4speed** » Tue Aug 18, 2009 10:27 am

You're positive it's timing related? It almost sounds like the carbs are jetted too lean.

NITROPIXIE · Post by **NITROPIXIE** » Tue Aug 18, 2009 10:44 am

It maybe be best if you can take the car to be rolling roaded and get it setup professionally. As the incorrect fuelling and timing could be detrimental to the engine and would cost you more in the long run if you damage your engine.

Did you have the webers setup correctly before putting the megajolt system on??

paulc · Post by **paulc** » Tue Aug 18, 2009 10:49 pm

yes, the carbs are rebuilt and jetted correctly.

i took it for a long drive last night. laptop on the passengers seat, up / down hills. idle, part throttle, full throttle. basically guessing at the timing for each bin.

funny enough - it runs a lot better now. i'm getting closer.

i would have thought there was a better way to make a config file - like a theoretical way based on average distributor curve. i've searched here and the web and have not come across anything other than the mapping.xls file uploaded here. that creates a linear timing 'curve' that the engine did not like.

so - i guess it's a lot of seat of the pants tuning.

Post by **brentp** » Wed Aug 19, 2009 2:11 am

Wouldn't that be a nice feature for the software?

If you guys could post some requirements, nice-to-have for a "make a map wizard" I would love to work that into the next version.

Broke4speed · Post by **Broke4speed** » Wed Aug 19, 2009 2:34 am

By jetted correctly do you mean wideband-tuned or old-school-possibly-inadequate-for-new-high-power-ignition-system-tuned?

paulc · Post by **paulc** » Wed Aug 19, 2009 3:47 am

brent.... fantastic idea!!

requirement 1) know the stock ignition curve

just out of curiosity - what would happen if i made a 2d map based on that curve? would it not perform like stock?

Broke4speed - this is car #14, i know it's not the carbs. you can hear/feel it.

TwoSheds · Post by **TwoSheds** » Wed Aug 19, 2009 5:59 am

In my opinion, the stock curve (if you have it) is where everyone should start

You could easily set up that curve and then impose the stock vacuum advance curve on top, then you would have the ignition absolutely per standard and could check fuelling without distraction, returning to fine-tuning the ignition map at the start of the 2nd cycle of adjustments.

I wish I could find the stock curve for mine!