18R-G ignition curve needed

**pilot** · 10-03-2006, 08:13 AM

Does anybody know an "optimum" ignition curve for this engine? I´ve installed EFI on mine and I´m not sure on this issue. I haven´t been able to make it knock loudly so that I can even know how much is too much for it.

If anyone has, at least, a rough idea, it would be appreciated.

Thanks

**scootaphill** · 10-03-2006, 04:31 PM

page 12-20 green bible Ignition System
Distributor.
vacuum advance angle:
mmHg inHg Dis. advance angle degrees
65 2.56 advance begins
200 7.87 7.5deg +/-1deg

governor advance angle:
dist RPM Dis. advance angle degrees
600 advance begins
800 3.5 +/- 0.5deg
1600 10.0 +/- 1.0deg
3000 8.9 +/- 1.0 deg

does this help?

cheers
phill

**pilot** · 11-03-2006, 03:24 AM

I guess it should help, but it confused me a bit.
First, those RPM are distributor RPM or crank? Then, does it mean that at 800 RPM advance must be at 3.5, at 1600 at 10 and at 3000 at 8.9? It first increases and then decreases? it sounds strange to me.

**Steve M** · 13-03-2006, 01:50 AM

Phill, which edition Were those specs from? The later version around 1991?

Below are the specs for the 9.7:1 18R-G engine with the old, small style dizzy (88230 and before)

Vacuum Advance Angle
mmhg / inhg - Dis. advance angle Degrees
45 / 1.77 - Advance begins
75 / 2.95 - 4.3^
105 / 4.13 - 7.5^

Governer Advance Angle
Distributor RPM - Dis. advance angle Degrees
600 - Advance begins
1400 - 14^
3000 - 13.5^

(^ signifies degrees)
Published 1977 version of "The Green Bible"

Below are the specs for the 18R-C distributor

Vacuum Advance Angle
mmHg / inHg - Dis. Advance angle Degrees
80 / 3.15 - Advance begins
120 / 4.72 - 2^
200 / 7.87 - 5^
300 / 11.81 - 8^

Governer Advance Angle
Distributor RPM - Dis. Advance angle Degrees
600 - Advance begins
1050 - 5.5^
1600 - 13^

(^ signifies degrees)
Published 1977 version of "The Green Bible"

**scootaphill** · 13-03-2006, 10:41 AM

yeah close 1992

the book i have covers 18R*C
19100-34290
19100-34250
19100-34260
19100-34230
19100-34220
19100-34221
19100-34214

different model
19100-34240
19100-34270
19100-34202

different model
19100-34310

These are ALL 18R*C and the different models have different values, however they all start at the same mmHg (80)
the ONLY 18RG specs i have are for
19100-88233
and these specs are as i posted earlier

cheers
phill

**Steve M** · 14-03-2006, 01:54 PM

The book I have doesn't say what generations it covers, but the compression figures listed are for the 9.7:1 compression 18RG.
From memory the compression figures listed in the later edition are lower, for the 18RGU/EU, which ever one they were for I'm not sure.

As they republished the book, they changed all the figures to suit the most recent version of the engine.

**pilot** · 15-03-2006, 06:28 AM

Does anybody know if those are crank or distributor RPM?

**scootaphill** · 15-03-2006, 08:30 PM

"distributor RPM" is how it is listed in the book

cheers
phill

**pilot** · 16-03-2006, 02:27 AM

That was my guess too because maximum numbers are too low.
Now, which of those would be for my engine? Mine is a 1982 RA63 with 11111-88270 cyl. head.

**Steve M** · 16-03-2006, 11:33 AM

More likely to be the specs from Scootaphill as your engine was made after my book.
His specs could be for the 18RGU though not sure about the 18RGEU, I've heard that it is hard to find most specs for 18RGEU engines.

**scootaphill** · 16-03-2006, 04:29 PM

other than compression ive seen no vaid data for the 18RGEU anywhere. and as the Witzl can verify there is an abundance of missinformation for these motors on the net (fuel injected)

next trip into the garage i'll have a look and see whats on my motor... ok ive had alook
my dissy has two vacuum diaphrams the number on my diaphram housing is 029450-3202. (this number doesnt seem relevent to anything???)

i was unable to find any part numbers on the dissy housing (does anyone know where i should look)
cheers
phill

**Steve M** · 16-03-2006, 11:11 PM

That format of that part number is the same as for most of the later model dizzies, and the 18RGEU ones did come with two vacuum points, one seems to act only as a point for cleanish air to get into via the thermo vacuum switching valve that is mounted in the thermostat housing.

The part number is pretty easy to find if it is on there. It is on a little stick on metallic looking plate just under the mounting lip for the cap. This thing is actually plstic and shrinks when you weld the dizzy.

To tell whether you've got an 18RGU/18RGEU dizzy and not just an 18R dizzy, check that the shaft thrust is preloaded with spring pressure, i.e. the shaft has no floating thrust.

I hav only found this on 18RGEU and 18RGU dizzies (I haven't looked very hard at other models though, just never seen it on an 18R/R-C).