Help with mapping ignition curve

beachbuggy61 · Post by **beachbuggy61** » Sat Mar 12, 2011 12:46 am

G'day all,

Well, I've finally got the MJLJ to talk to my computer and it's all looking good! What I have to do now is get the advances curves right.

It currently seems to be running out of puff in a big way around 4500 in 2nd so I think I've got some work to do on getting the curve right.

I looked in the "Library of Maps" and couldn't find anything that matches so I thought I'd ask the question here as the library is, let's face it, a library, not a place for questions!

So:
1915cc type 1 VW
W130 Cam
Biggish valve heads
8.8:1 compression
2 x 40mm Kadron (Solex) carbies
Borg Warner K16 turbo on a blow through set up running about 8-9lbs boost

Does anyone have any maps that would suit, or ideas of what some of the values should be?

Many thanks in advance,
Marc.

DannyP · Post by **DannyP** » Sat Mar 12, 2011 3:20 pm

Sorry Marc, mine is NA, no experience with turbos at all. Some of the aircooled drag turbo guys should be able to give you a rough curve, as well as the right amount of boost retard.

Spockie-Tech · Post by **Spockie-Tech** » Sun Mar 13, 2011 3:41 am

The first question is..

Was it "running out of puff around 4500" on the dizzy *prior* to fitting the Megajolt ?

You could have a mixture/fuelling problem that no amount of fiddling with the ignition curve will cure.
The easiest way to tell for sure is get a Wide-Band-O2 sensor in the exhaust and watch your A/F ratios.

Fuel supply starvation, incorrect jets, boost-pressure leanouts or any one of a number of things are more likely to give you a major "out of go" feeling than less-than-perfect ignition curve. (Assuming you dont have an accidental rev-limit activated or something like that)

If your ignition is way retarded, then a tweaked up engine tends to feel sort of "lazy" rather than hitting a real no-go wall in my limited experience of such things. If its a really obvious dip in the power, look to the fuel first.

If it *was* running well on the dizzy, and isnt on the megajolt, and nothing else has changed. then take the old dizzy (assuming you still have it) to an ignition shop, and get them to spin it up on the testing machine and draw you a graph of its curve, and start with that in your megajolt. Then tt should run just the same as the dizzy did if the installation is ok.

If I was running any sort of super/turbo charged carburettored engine, I would consider a WBO2 sensor a highly worthwhile investment. You dont want to lean out without knowing it when on boost.. Meltdowns are mere seconds away if youre pumping air in hard and the mixtures get lean.

beachbuggy61 · Post by **beachbuggy61** » Sun Mar 13, 2011 12:53 pm

G'day Spockie, thanks for the advice.

It used to run fine on the dizzy, revved all the way to 6k clean as a whistle with the Compufire that I used to run until it's dizzy-top sender failed for a third time, which is why I went to MJLJ.

Old dizzy was a 009 so I've tried to replicate that on the MAP as the advance curve of a 009 is pretty easy to find on samba and similar. The bloody thing should rev but it just doesn't sound like/feel like it wants to!

The WBO2 sensor of which you speak, can that be connected to the MJLJ so that I can get a reading on the screen? Where abouts should I mount it on the exhaust? Threaded into the pipe just after the turbo? Are they an expensive item? If it is fuel, then I'd like to know, or at least be able to rule that out even though it seemed to be fine before the MJLJ installation. I'm confident I got the installation right, all other parts of it work and the car fired up straight away.

Just another thought.... I'm not right up to speed on the 'wasted spark' thing, does this mean that I could have leads on wrongly and it still works but not as well as it should?

Thanks for the help, Marc.

Spockie-Tech · Post by **Spockie-Tech** » Mon Mar 14, 2011 11:17 am

OK, So its probably not an engine fault if it used to work on the dizzy...
unless other work (or unknown changes) were done in addition to fitting the megajolt.

No Vacuum leaks ? Is the MJ reading the boost pressure correctly on the MAP sensor ?

Have you monitored the 12v supply (to both the MJ and the coilpack) to make sure they arent sagging at higher RPM ?

Does the MJ display show the expected advance on the readout when revving it ? Have you verified the timing is changing under MJ control with a timing light on the balancer/pulley
?
Have you tried the datalog feature so you can playback and see what the advance being fed to the engine is ?

There are many wideband sensors out there.. Most have a 0-5v output that can be connected to the MJ Auxillary input for display and datalogging - so you get it all on a nice single synced up graph.

I have an Innovate Lc1, but they are a bit pricey. If you dont mind patching a small circuit board and associated connectors into the MJ, then you could probably use something like this.. http://14point7.com/SLC-OEM.php

Exactly where to place the sensor on a turbo car Im not sure. Probably depends on the heat levels reached. If you get one, ask the manufacturer about their reccomended placement.

Wasted Spark is unlikely to even run if you have the firing order wrong. On a 4 cylinder, you only have two coilpacks, so there arent too many combinations that will even roughly work.

Waste Spark is simple. 4-stroke engines spin 720 degrees (or 360 degrees twice) for each cycle. Waste Spark just means that while one cylinder is being fired at top-dead-center on the compression stroke (about to go boom), the corresponding cylinder that is on the "opposite" side of the cycle (top dead center on exhaust) is also being sparked (which does nothing much, since the cylinder is full of exhaust gas being pushed out - hence "wasted spark").

WasteSpark means the ignition system only needs half the number of coils, drivers, and doesnt need a cam-position-sensor (which it would need to know which side of the cycle the engine is on otherwise).

Lets see what the answers to some of those questions are before I go further

beachbuggy61 · Post by **beachbuggy61** » Mon Mar 14, 2011 11:23 pm

Hi Spockie,

Speaking to you on two subjects at once!

Okay. I'll cover off the questions and see how we go....

No Vacuum leaks. The MAP sensor is reading exactly the same numbers as my on-dash boost guage (after I've done the conversion from kPa to Hg inches/PSI) so I'm confident it's working ok.

Voltages are good and consistent across the whole range

Yes, the MJLJ does show exactly the advance that is expected. When you give it a static rev, the green square moves about in a roughly circular pattern as the revs and the vacuum/boost change and then when I'm driving it, I can see the big advance number on the screen does exactly as the curve map says.

Yep, done the datalog feature thing too, although this is harder to red, it does as expected.

Thanks for explaining the wasted spark, that is what I thought it was. Surely if the coilpack is firing off an extra spark that's not needed, isn't that just reducing the time the coil has to build up with another spark for the next rev?

I'm also wondering if I might have a leaning-off problem. I'm only running 135 mains in my 40mm kadrons and I think that might be a bit too lean, although it seemed to work before. Maybe I'm burning mixtures better now and needing a bit more fuel up top? I'm going to try some 145's and if that improves, go to 155's which may make it better or worse, in which case I would go back to 145's. Will let you know how that goes.

In the meantime, please keep the advice coming, I'm open to any and all new learnings!

Cheers, Marc.

Spockie-Tech · Post by **Spockie-Tech** » Tue Mar 15, 2011 1:40 am

OK, So far so good.

Have you checked that the timing is actually moving with a timing light on the crankwheel ?
Its unlikely, but possible that the SAW wire from the MJ to the EDIS module is open, which would cause the MJ to think it is modifying the advance and show so on the screen, but the EDIS isnt getting the message.. A timing light will confirm you have timing control working.

In waste-spark, the coil doesnt fire twice sequentially.. They are "Double Ended" Coils, with a spark plug on each end of the coil that fire *simulataneously* from a single coil-charge. One is firing under compression pressure, and the other is fiting at near-atmospheric pressure (the waste spark).

They are effectively wired in series like this

gnd------||-------mmmmm------||-----gnd
...........^............^.............^
.........plug 1......coil.........plug2...

So the coil doesnt have to produce two sparks, its just one discharge, split across 2 plugs

beachbuggy61 · Post by **beachbuggy61** » Tue Mar 15, 2011 2:01 am

Ahah! I hadn't thought of that! I will go home tonight and check that the timing marks on the pulley move as the engine revs up.

I'm pretty sure that it is working though because when I changed a setting on my map from 13 degrees at 1000rpm to 10 degrees at 1000rpm, the engine changed sound, so I'm confident the signal is getting to the EDIS, but it's always better to make double sure of everything.

Thanks for explaining wasted spark. I get it now!

Tonight I'll check the timing mark and whack the bigger jets in it and see how we go!

Thanks, Marc.