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General Category >> Rubber Side Down! >> CDI unit: what do we know about it?
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Message started by philthymike on 07/11/19 at 18:28:29

Title: CDI unit: what do we know about it?
Post by philthymike on 07/11/19 at 18:28:29

Regarding this units advance/retard is there any curve to it?
I read somewhere that it's a fixed ratio at all RPMs.
Anyone know otherwise?

Title: Re: CDI unit: what do we know about it?
Post by DragBikeMike on 07/11/19 at 21:45:17

It has a curve. Like 3 BTDC at idle and 27 BTDC full advance (probably above 4000).

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1521968829

I have also found specs on the older DR650 that show that model was 0 at idle and 28 BTDC above 4300. I have no idea if the ignition modules are interchangeable.

Title: Re: CDI unit: what do we know about it?
Post by batman on 07/12/19 at 05:02:33

The DR650 has a two plug head ,and a CDI , the Savage has a TDI , the coil and ignition modules are a matched set , even changing to a hotter coil can damage the igniter mod. (flashback) . The Savage having a plug in the center of the head is considered "fast" being as the flame front needs to travel only half as far as the flame front on a normal two valve head, and is up to the job even when we mod the motor for higher performance . There is a wire from the starter that sends a signal to the TDI that further retards the timing when cranking during startup. If you felt that the timing needed more advance you could enlarge the holes in the pickup coil and shift the advance/retard a couple of degrees, but I'm not sure it would be worth the effort, being the two times you want the timing to be retarded is at startup and high speeds to avoid detonation.( don't fix it if it isn't broke)

Title: Re: CDI unit: what do we know about it?
Post by philthymike on 07/12/19 at 10:16:52

My concern is it may have broke the day they introduced ethanol blended fuel everywhere.
The blend burns faster so retarding should be necessary to prevent peak cylinder pressure too early in the cycle.
Suzuki hasn't changed this bike significantly since the 80s so the ignition timing is still likely set for 1980s fuel without ethanol.

Title: Re: CDI unit: what do we know about it?
Post by verslagen1 on 07/12/19 at 10:26:02

0A0C037F7D7A7E4E0 wrote:

I was reading the SSM the other day, I think it's 5 to 30 BTDC, idle to 4000 rpm.

Title: Re: CDI unit: what do we know about it?
Post by Fast 650 on 07/12/19 at 10:35:57

3E2627223A26372327252B4E0 wrote:

The rotor and ignition module changed in the mid 90's for the LS. Trigger location changed on the rotor so static timing is different. And the module has to match the rotor or the timing is way off, which sounds like the curve may have changed then also.

Title: Re: CDI unit: what do we know about it?
Post by verslagen1 on 07/12/19 at 11:02:13

4E697B7C3E3D38080 wrote:

Yes, the trigger points are different, but I believe the static timing is the same. But you really can't check static timing.

The old rotor has a short trigger plate and the new one has a long one.
The old rotor trigger point has a large offset from 0°TDC.
Whereas the new is short.

I'll have to put a timing wheel against the rotors and check.
But I think the new rotor is set up to spark somewhere between the beginning and end of the trigger plate.
Whereas the old just triggers it.
I believe the change was for accuracy, not that this type of timing is incredibly accurate. Also may indicate that the processor was changed.

Title: Re: CDI unit: what do we know about it?
Post by batman on 07/12/19 at 19:11:23

Octane is a fuels resistance to burn, 87 octane pure gas 0r 87 octane E10 ,burn at the same rate. No adjustment (retarding )of the timing is needed.

Title: Re: CDI unit: what do we know about it?
Post by philthymike on 07/12/19 at 19:23:38

There's many sources that say otherwise.

Has anyone here ridden a savage on straight non blended gas from a marina?
Does the engine run any different then?

Title: Re: CDI unit: what do we know about it?
Post by Todd James on 07/12/19 at 20:43:45

I have been running my S40 on ethanol-free (pure) gasoline for
several years.

The only performance advantage that I notice is that it may start
a little easier and achieve smooth idle sooner; especially if it has not
been started for a month or more.

I don't ride aggressively enough to know if there is more, less, or any
spark knock compared to ethanol blended gasoline.

The reason I run ethanol-free gasoline is that the bike may sit for
weeks or several months while I am traveling and I don't want to
deal with phase separation or moisture accumulation in the fuel.

Title: Re: CDI unit: what do we know about it?
Post by philthymike on 07/12/19 at 21:39:24

Thanks for sharing that Todd. Very interesting.
There's one report of the engine running normally on non ethanol gas.

Title: Re: CDI unit: what do we know about it?
Post by LANCER on 07/13/19 at 03:35:13

I keep a lot of fuel containers at home for the bikes, mowers and 4wheeler. I fill them with 100% gas (87 & 91 octane) at the one station in town that has it and fill the tanks when I return from a ride. When filling on a ride I use what ever fuel is handy and have not noticed any difference in performance between the fuels.
I like to ride aggressively. [ch128526][ch127949]

Title: Re: CDI unit: what do we know about it?
Post by philthymike on 07/13/19 at 07:47:22

I guess that the timing is such that the motor isn't too sensitive about fuel.
My old 67 Econoline wasn't so happy with the fuel changes. The reason I sold it back in 06 is I couldn't get it run right on blended gas no matter what. I fussed with the points and timing to no end. Replaced all the ignition system, rebuilt the carb and replaced the fuel lines. Nothing helped. When it became hard to find straight gas I'd had enough with messing with it.

Funny how some engines aren't picky about fuel while others are.

Title: Re: CDI unit: what do we know about it?
Post by Dave on 07/13/19 at 13:17:08

4A5253564E52435753515F3A0 wrote:

There's many sources that say otherwise.

Has anyone here ridden a savage on straight non blended gas from a marina?
Does the engine run any different then?

I have a modified engine and run Premium has I have a Wiseco piston with higher compression, a cam, VM, carb, etc.

I have run E10 pump gas, Avgas 100LL, a couple different brands race fuels, and Premium gas that is ethanol free (purchased at either a Marina or at gas stations that sell Pure Gas).

I have noticed a very minor change in smoothness with the higher octane pure gasoline....the burn seems to be a bit more controlled under full throttle and the full throttle acceleration just feels a bit smoother. I don't know if it is the octane rating that makes the difference.......or the fact that the fuel/air ratio is a bit richer as a result of there being no ethanol. During normal riding that doesn't include long full throttle runs - I can't tell any difference at all.

So......it really doesn't make much difference and running Premium pump gas in my engine seems to work well - with or without ethanol.

Title: Re: CDI unit: what do we know about it?
Post by batman on 07/14/19 at 09:23:50

The only real difference between pure gas and the SAME octane E -gas ,would be seen in mpg. E10 being 10 percent alcohol would contain about 3.33% less BTU content than pure gas. If you got 50 mpg with pure gas you could expect to only get 48.35 mpg from E gas. When you consider the difference in price at the pump , your wasting money ,If you spend the money to save a 5 miles per tank full on pure gas , you'll find that the same amount will allow you to ride an extra 25 miles on E-gas. But to each his own.

Title: Re: CDI unit: what do we know about it?
Post by justin_o_guy2 on 07/14/19 at 11:42:43

I'll Tell you what we
Know about it.
I've been looking into since this post started.
What I've discovered is very unsettling.
It was designed by a Russian SPY!

Title: Re: CDI unit: what do we know about it?
Post by Steve H on 08/02/19 at 08:22:10

Those darned Russians just get into everything ;D

Title: Re: CDI unit: what do we know about it?
Post by batman on 08/02/19 at 09:28:49

637B7A7F677B6A7E7A7876130 wrote:

Your 67 ran on leaded gas ,lead was removed around 1971 ,the reason it didn't run may have been that after 71 motors got harder valve seats that they needed to deal with unleaded gas, as lead protected them . If you didn't use a lead additive your valves got damaged over time ,hurting compression. If you had pulled the head and had the seats replaced it might still be running.