Target A/F ratio

[hemicat]

I know the fuel entering the cylinder offers some of the required cooling for our engines. I'm just not quite sure if the current target ratios are a little rich because of this or if it could use a little leaning out. It is currently around 13.4 at idle and progressively goes to 12.3 at WOT. It seems to be loading up idling and does use quite a bit of fuel cruising around. I'm pretty sure it needs to be thinned out a little bit not sure just how much being an air cooled... If that makes any difference on tuning.

[supaninja]

Give the motor what it wants, if it's loading up at idle then try pulling some fuel. Holy crap your giving it way too much fuel in the cruise cells.

My motor isn't stock but it's not super wild either. Idle is 12.5, cruise is 15.5, and WOT is 12.0. Ign is 18deg at idle, 41-45 at cruise, and 35 at WOT. That combo works for my motor and i'm pretty sure it won't work on yours so DO NOT try it, but give it what it wants.

[hemicat]

Ok. I just wasn't sure if there was any certain limit on just how lean was too lean being air cooled. My engine is in a Baja, (1915 with the new CB EFI with dual 40 tbs) not stock but no screamer either. Right now it is running 12* @ idle, near 32-34 cruise and low 30's WOT. So far so good with that but a stumble off idle from first take off after idling for a minute or so. The only other problem I'm having is the rpm is very unstable. It will be running at 1000-1050 while idling, but if you watch the dashboard the reading will jump to around 2500-2700 but only real quick. You have to really watch it to even catch it, or have the timing map up and watch it. Does it going down the road as well but only does it real bad when the vacuum reading goes to WOT, no matter where the throttle position is at.

[Steve Arndt]

Have you checked your throttle body synchronization at part throttle?

s

[MinamiKotaro]

Give it what it wants x2. Butt-dyno and the ear will tell you a lot but the only way to be 100% sure is to visit a real dyno and tune for highest vacuum and/or lowest BSFC.

Your RPM issue is more likely a trigger issue. The Megasquirt (or whatever system you are using) "thinks" your RPM spikes due to noise, the trigger being out of phase or too far away from the pickup, or many other causes. What are you running for ignition? Distributor? Crank trigger? Try using resistor-type plugs if you aren't already. That usually helps a lot.

[hemicat]

I have checked the linkage several times, Many of my carb problems were due to this. I am currently running a locked out Magnaspark II distributor as a rpm source for the ecm. It has 1 wire that goes to the ecm and 1 wire that is grounded to the case. My first thought was the wire going back to the ecm was too close to a plug wire, checked and moved that. Then thought that maybe the plug wires were too close to the pick up module inside the dizzy, rerouted those. Now im wondering if maybe the plug wires are causing interference where they are touching the case and manifolds messing with the ground? I am currently using NGK BCP6ET plugs with MSD 8.5MM wires and a MSD blaster coil. Not sure if these plugs are resistor plugs or not... Could running too rich be causing any of this? Maybe not allowing the plug to fire intermittently or is this more a distributor issue?

[Steve Arndt]

Make sure you have resistor spark plugs. 95% of trigger problems are from non resistor (easy to buy) plugs.

[MinamiKotaro]

Make sure you have resistor spark plugs. 95% of trigger problems are from non resistor (easy to buy) plugs.

NGK resistor plugs will have an "R" in the part #. Aka B5HS for non resistor or BR5HS for resistor.

[hemicat]

I did find a post in my search earlier about using resistor plugs and pile was talking about using NGK BP6ET plugs. I searched around and these seem to be resistor. Trying to find them is another story. Did find a pepboys an hour south of where I live has them. Going to try and get down there tomorrow and see what I can come up with. Hopefully this will solve that issue so I can continue my tuning efforts. Trying to tune with erratic rpm readings is nearly impossible... to say the least.

[andy198712]

surely a couple dollars in postage off ebay saves 2 hours fuel?

[hemicat]

OK went and got plugs (NGK BKR6EQUP) since I have a company service truck and the place was on my way... Put them in and it does sound better (starts easier and runs quieter) but am still having same issues. Tried leaning out at idle and still jumping around. Feels like its dropping a cylinder (but it is really jumping up and activating 2-step) when running heavy load still but only real quick and not consistant. May take it a 1/4 mile between times or it could do it 3-4 times every couple seconds. It keeps activating the 2-step which is set at 4500 when im only turning 2500 or so. I dont have the 2-step hooked to anything and have done everything short of pulling the wire out of the ECM to get it to stop. even tried setting it to 6500 but it keeps reverting back to 4500. Its set to ground activate, and if I switch it to 12v activate it stays on. Is this right or is there something else going on possibly? Just about ready to give this thing up and move on to a small block chevy since everybody and their mother knows about them. But that would mean 4 years have been wasted and I get too many compliments on the bug. But still rather pissed that after the stock pile of replaced parts it still just wants to give me trouble. Im beginning to think that its just a vw and that is how they are, you just cant care about how they run more so than they are just running.

[hemicat]

Sorry for the rant last night. It has just been a really frustrating build so far. Went out a little while ago and had a rider with me to watch the laptop. The rev limit and 2-step had not accepted the change I made a while ago so I went in and adjusted them and made sure they stayed where I wanted them. 6000 rev, 6500 2-step and it ran fine. I know that is just a patch. If I put the timing light on each wire individually they all read different. How its doing this with a locked out centrifugial only dizzy is beyond me. Im starting to wonder if I shouldnt try reinstalling my old dizzy (since it worked better than this one) and see if that makes any difference. I think im just going to have to bite the bullet and see if I can run some sort of crank trigger with the new CB ecm. Just about every dizzy I have put in this thing has had something wrong with it. The last 2 have been programmable and each cylinder has been off a little from the rest. Not sure where to go at this point.

[Piledriver]

The BP6ETs are NON resistor, but I had no issues as I was running resistor wires.
Usually resistor wires OR resistor plugs work fine, but some more delicate systems may need both..

...Plus all my ignition circuitry is as far, far away from the rest of the ECUs system as possible, ignition and injector drivers are external/logic drive and run off a different relay/power buss and physically ~all on the opposite side of the car from the sensors.

The LS2 coils (power side) are also the only part of the system that get grounded to the engine, logic ground goes back to the MS. They have their own direct off the battery relay and fuses for 12v power.

Someone said something about CB having a software update to deal with erratic timing IIRC, (but that could have been you)

[hemicat]

If the ganged ground wires say to attach them to the case would it hurt to run them back to the battery? The harness has a set of wires that come from the positive side of the battery already that go straight to the fuel pump relay and something else... Not looking at the schematic right this second. Not sure if it could be a noise issue with the plug wires and the case causing this. The plugs I'm using are resistor plugs now. Only took me 2 days of searching to find some of what I was looking for. But I got them now. Just thought that maybe switching to resistor wires with non resistor plugs might be another option to try?

[hemicat]

Finally got it figured out. Turned out to be a bad voltage regulator in the alternator. It was putting out 19-20 volts. The ECM was OK, not sure if it did damage to the coil but I swapped it out anyway. After I got that fixed I had to go back and readjust the target table and clear the learn table. It is taking time but we are getting there slowly.