type 4 timing

[Bruce.m]

What is your idle map value? Somewhere around 55-60 I’d expect.

I’d remove your 96 MAP row by bumping the table values down one row.
Then add a new row for 60MAP. Copy the values from the 78 MAP row and change the 800rpm setting to 8degrees. You might need to adjust that between 7 and 10 until you (hopefully) get a stable idle.

[oprn]

Ok, give me a bit of time to digest this...

Bruce, I believe I put that value in based on the reading I got at idle at the time. That was with a fresh engine so it is possible that it has changed with the rings breaking in. I can check it again.

Piledriver, you could be correct on 10* being the limit. Yes that is the default timing on the EDIS 4 system and perhaps it will not recognize any lower value than that. What does the acronym COPs mean? Not familiar with that one.

This Mega jolt is my first experience with crank trigger ignition. I am an old points and distributor guy so the learning curve is steep. Set it up 4 years ago and it's run pretty flawlessly since, just this last little bug to work out. Not sure if it's carbs or timing, maybe a bit of both.

[Piledriver]

COP= Coil On Plug. Coil literally pushes on the plug, integrated boot, Most Japanese or European cars, most modern Fords.
CNP= Coil near plug. Independent coil per plug, short wire, usually mounted to valve cover or such, LS2 coils for GM.

You should be able to cut off the engine with the throttle plates closed regardless of timing unless there are large holes in the throttle plates or a vacuum leak. I don't think your air bypasses are active (but possible, original app may have has fixed idle airflow). Hows your carb balance? I have had to untwist the shafts at least a little on every IDF carb I have worked on.

[Bruce.m]

Check each intake for suction at idle, to see if it’s strong & the engine stalls when it’s restricted . I’d used a nitrile gloved hand but you may want to use something else for safety reasons .

[Piledriver]

I have a smoke setup but I used to use an unlit propane torch, just lean out all the carbs idle screws until the RPMs drop a little first,

[oprn]

The carbs balance well at idle. Here is a picture of the two adjacent carb bores. There does appear to be idle bypass screws in there. They are not set the same. I always assumed the carb was balance flowed at the factory, then the plugs installed on the outside to prevent Joe Greasy Thumbs from messing with it.

I do need to double check my vacuum lines for leaks. Hopefully get a chance to do that today. I have a part time job that I don't want. It takes more time than it is worth but the Boss is like a date gone bad. I just can't seem to get rid of him! Maybe change my phone number...

[oprn]

Check each intake for suction at idle, to see if it’s strong & the engine stalls when it’s restricted . I’d used a nitrile gloved hand but you may want to use something else for safety reasons .

Due to space restrictions on this Buggy body the air cleaners cannot be taken off with the carbs in place. The air cleaners won't lift high enough to come out. To do this test I would have to remove the carbs and re-install them without the air cleaners. Each time I remove the carbs they have to be balanced all over again. You can never get the carbs positioned exactly the same each time. A snail is useless to me too for the same reason so I use the age old biker bottle trick for balancing.

[Piledriver]

Balance by manifold vacuum is an ancient but proven method, it's done on bikes for same reason, limited access.

That leave us back with vacuum leak, or the bypasses being open causing high idle, with EDIS base timing being a possible contributor.

Per a quick Googling, Megasquirt with EDIS allows -10 (ATDC) to 59 BTDC timing so I expect Megajolt would as well, you probably should simply try dropping your timing at low rpm and see if the idle speed follows. (it should)

Those carbs look almost worse to get to than my `75 Goldwing, and with a lot less air cleaner.

Consider shorty manifolds and taller air cleaners. (stacked elements?)

[oprn]

Do short manifolds even exist for the type 4? When I bought these it seemed only one manifold height was offered.

Life just keeps demanding on my time but maybe I can get to it tomorrow? That is if I don't get called away to go baling straw...

[Piledriver]

I have a set I bought (IIRC) here in the classifieds, looked like new parts.
They exist.

I have really stubby 42mm flanged Yamaha jet ski TBs on them, welded the flange up a bit and redrilled, they easily clear my engine lid on my squareback with the angled velocity stacks/flow straighteners. Didn't run them on the 1800 because overkill.
Will try to post pics tomorrow, have to crash, work nights.

[oprn]

Here is a new timing map I just worked up. I removed the 600 RPM row and pulled a bunch of timing out of the low pressure end. The pressure range is still subject to review pending an engine run to see what my actual manifold pressure is in real life.

Thoughts?

[Piledriver]

I would bump the high MAP area of the first column up a bit as antistall.

I usually run ~20+ degrees starting just off idle, makes for a nice kick on tip-in.

This isn't exactly whats in the car, just something similar found handy, that happens to still be on this laptop.

Timing.jpg

[oprn]

That is really aggressive at the low end! What fuel grade and compression ratio is in your engine?

[Piledriver]

That is really aggressive at the low end! What fuel grade and compression ratio is in your engine?

Regular (us) 87 8.5:1, 2l heads, web 73.
Id prefer a .035' deck and 9:1 but cant get there with the local machine shops.
With more cam i'd run more.

New shop, after AC/heat its getting a bridgeport knee mill and decent lathe to do myself.

The 1.8 was planned to go back together after a freshen up but now it looks like 100 Empi birals x 71 w/hbeams/dodge rod bearings and oddly modded 1.7 heads. hoping the extra ~5mm meat in the deck will help sealing under boost.
(100mm cylinders will seat in shallow registers over the 100mm registers in the heads, top ring stops 1mm below in cylinder)
Had this idea decades ago, determined to try it.

[oprn]

Ok, this is a 1700 Bus engine with a Web 86, 96mm P/C set. The C/R would have been in the 9/1 range but there is no premium fuel available locally, I needed to be able to run 87 octane. I bought a set of rebuilt 1700 heads from Brothers and they opened up the chambers so I could get the C/R down to 8.4/1. On reflection I should not have done that and just lived with the 1 hour drive to full the tank.

I hear you about the lack of machine shop services. Nothing here either. The type 1 engine in the sand rail came out with a disappointing 7.8/1 C/R even with a .038" deck. The cost of shipping the heads two ways to correct that was more that I wanted to invest in a set of stock SP heads for a simple trail ride sand rail.

I do have a small lathe and a small milling machine. I bought a head for the milling machine advertised as fitting a #3 MT machine but when it arrived it was actually a #4 MT. So... now I need to find a machine shop that will adapt it... I don't really feel my skills on the lathe are up to the task with no taper attachment.