Hi all,

Couldn't think of any other way to describe it, hence the flat spotting topic name.

I've been setting up my 1915 fuel injection with EDIS ignition, and an Megasquirt 2 controller.

I got a basic fuel map set up and have been using the auto tune function on Tuner Studio to get it right. This is really starting to come together. The more I drive, the better it gets. In fact when it's running right it's a joy to drive, very smooth and powerful. My problem is that it stutters and flat spots when I put my foot down, even gently. In my old carburettor days, I would say it's 'bogging down'. It does this quite severely, to the point that as I'm blatting the throttle on the sand dunes, it bogs down so badly that I have to put the clutch in, rev it til it clears itself and then go again. Not fun when you're trying to get up a dune or squirt around in the soft stuff! It also does this on the road. If I bury my foot off the line, I can get good up-shifts, but if I try to drive like a normal citizen, it stutters and carries on a treat!

If I had carbies, I"d be thinking that maybe the accelerator pump jets are too big, but with EFI I don't know. I'm very new to EFI. Could it have something to do with accelerator enrichment? Or is at a fuel map problem? I think the fuel map is getting right though because auto tune is making less and less adjustments each time I drive it.

Hopefully someone might have a suggestion, because other than this problem, everything is going really well and the car is fun to drive.

Many thanks, Marc.

Not done any Megasquirt but plenty of Haltrech and one CB under my belt. You answered your own question, accelerator pump adjustment. By your description I'd say too lean, needs more pump(fuel) added.
Obviously an O2 sensor would confirm rich/lean.

Hi Matt,

Thanks for the input. Too lean you think? I'll double check the O2 readings. Must admit I was more concentrating on getting it to rev as I started getting bogged in the sand rather than looking at the lamda reading, but it felt like there might've been too much fuel in there!

At least now I have a starting point, as I was a bit lost before!

Thanks, Marc.

Have you started data logging yet? It will make life real easy to diagnose things. I can come for a drive up tomorrow and have a look if you like?

I'm leaning towards rich.

What are your injector times ( say at idle and WOT @ 3000) and % enrichment on acc pump settings? Sometimes if your way off on the rich side, because of unburnt fuel, your O2 may give a bum steer, if so it'll look rich, black smoke yada yada.

it may need more timing advance

Thanks Ian, I'm leaning (LOL) to rich as well.

Matt I think you might be onto something. When I was giving it throttle to try and clean it out I saw black smoke in the rear view mirror, so it might have so much unburnt that it's throwing the O2 sensor out. I'm going to do some more reading about how to set/change the accelerator enrichment in Tuner Studio as I'm using the settings that were in the Megasquirt when I got it, which the guy who set it up said should be about right. Niaive of me perhaps to believe him!

Ian I think it's got plenty of advance, for example; 10 deg @ 800rpm, 14 @ 1100, 23 @ 1500, 30 @ 2000, 32 @ 2500 then 34 from 3000 onwards. Does that sound about right?

Thanks for all your advice.
Marc.

Oh, and those ignition timings are at revs under boost. Once on boost they back off a bit

i have a locked dissy on my carby turbo and timing is set at 28 at idle no advance.
lee has a efi turbo and he runs upto 40deg

I haven't finished reading it myself yet but it should give you a good idea.

http://195.159.109.134/vemsuk/forum/index.php/topic,97.0.html

Good grief! That's a big read vlad! Better make a coffee and start at the top!

Cheers.

Yes it's a turbo engine, running about 8:1 with a W120 cam (not ideal I know but should still work).
Quad throttle bodies with injectors in the manifolds

It runs 34 degrees from about 3000 rpm and up with no boost. As the boost increases, the timing retards back to about 27 degrees at full boost. I currently run 10lbs max boost.

For example: at 4000 rpm, no boost - 34 deg, 4lbs - 31 deg, 8lbs - 29 deg, 10lbs - 27deg

Does that look reasonable? I know the formulas can be complex, but I want to try and get it right, so if you think this is way out, I better get out my abacus!

Now that looks good to me. If anything, I'm feeling some are slightly high, you could retard some of the higher settings a degree or two, but I have little recent experience in this area. It will definately perform, just may get hot or cause detonation, so retard slightly if necessary.

10lbs, 8:1, 27* advance.......I hope your fuel is good!
I'm not saying it's not safe (depends on chamber, DCR, etc), but sounds a bit close to the edge, the 120 cam will bleed a bit to help out, but if you're not sure if you have enough boost retard, dropping 1* timing for every1 lb boost is normally a good starting point that's safe.

And yeah, if you need steady throttle to clear it, it's probably rich, if you need a few pumps to keep it going, probably lean (accel cct). Also check your TPS is set correctly, a lot of throttle stumbles can be caused by TPS mis-adjustment.

Thanks Matt, Rod, it's good to know I"m at least somewhere near the mark!

Yeah I'm going to recheck the TPS setting this weekend, I'm not 100% sure it's reading closed to WOT properly. I'm also going to datalog so I can try and really accurately identify the problem.

Thanks again.