Jump to content
IGNORED

Have you used a CDI on an Oilhead?


Bert Remington

Recommended Posts

Bert Remington

This is Roger 04 RT's fault for asking the question: slots me into solutions-mode :).

 

BLUF for most probable solution: MSD MC-1 or MC-2 p/n 4220; MSD 8830 filter capacitor; Nology ProFire Ignition Coil PFC-03-D; TBD ignition wires; and Autolite 3923 >copper< spark plugs at stock or up to 0.060" gap.

 

Warning: do not use non-resistive wires or plugs unless your R1100 came from http://www.rbracing-rsr.com/bmwturbos.htm.

 

The MC-1 and MC-2 are basically analog 6-series modified for single- and dual-channel DISs. MC-1 and MC-2 have the same p/n with the differences apparently being parts availability and maybe some shifting functionality. At 3lbs 8"L x 4"W x 2.25"H sans vibration isolators they are kinda big. The electronics themselves are in a potted cast aluminum housing, quite rugged and quite water-resistant. You really don't need the vibration isolators and could probably install it underwater except for penetration points. There are two categories of penetrations: low-voltage/low-impedance and high-voltage (500V) to coil. The former can be weather-sealed with Honda dielectric grease; the latter need extra care to protect against stray voltages getting into places they shouldn't (note: you can use shielded twisted-pair to reduce inter-circuit interference without affecting ignition coil performance). You want #16 minimum for +12 power to filter and battery; #22 is adequate everywhere else. Always always use stranded wire (high strand count better) for vibration reasons!

 

I'm going to research mounting locations using my MSD 6AL (I have an MCCruise so options limited) and research spark plug wire options (I doubt BMW's wires can handle dv/dt stress).

 

Link to comment
Bert Remington

Mounting the MSD electronics box is easy: cut an 8" length of 4x4 and find a place it fits :).

 

I'm not giving up my MCCruise and its vacuum-actuated throttle control occupies a good location.

 

Another good location is the left-hand storage box which I'm not giving up either.

 

So far the best (really only) location is...the Telever "wishbone", "trailing arm", etc whatever it is called.

 

My experience with both direct chassis and engine mounting of the MSD boxes indicates they are shock- and vibration-resistant and temperature-tolerant. I've never had a failure, albeit no off-road use.

 

I don't think the wishbone location will significantly affect unsprung weight or suspension compliance. Forward weight and moment-of-inertia, yeah, but I could do better by losing weight.

 

I think I can make an aluminum bracket that doesn't require any modifications to the wishbone itself.

 

I'm continuing to research spark plug wire options.

 

Reminder: so far this is a design exercise based on Roger 04 RT's question.

Link to comment
Bert Remington

This design exercise has now moved to the wallet stage: I just purchased a Nology ProFire Ignition Coil and a pair of used spark plug cables. My friend who has my two 6-series MSDs will be bringing them back because he's got other issues with his Bronco (low-to-high altitude ECU tuning). And I'm pretty sure I have an 8830 somewhere in my parts bin. Autozone has copper 3923s.

 

My wiring for the AF-XIED is all laid out...but I haven't cut any wire. Its going back in the box.

 

What happened is I found a serious mounting location for the MSD electronics box. I was planning on replacing the BMW dual-socket power outlet (I'm selling it if anyone's interested) with a standard "cigarette lighter" socket so the bracket on the left footrest assembly was removed. The bracket is fastened to the footrest assembly with two small bolts and, if I make a tilted mounting plate, there appears to be room for the MSD box. Even though its only 3lbs I don't like the rocking forces on those two bolts so the mounting plate will include a third bolt stabilizing it to air box. I'm going to skip the vibration isolators for space reasons. I lose easy access to rear shock rebound adjuster and remove/replace of footrest assembly just got harder but...another MSD in another one of my vehicles!

 

Thinking out loud, (1) I'll probably run primary power to starter and mounting the 8830 nearby; (2) I'll run coil power as foil-shielded twisted pair inside a copper braid shield (ie double-shielded, I use the braid from RG-8 coax cable) to the ProFire coil mounted in the stock location; (3) I'll run the ignition enable and trigger as twisted pair to the stock location; (4) based on Doug Raymond's schematics it appears I will have to use the MSD tachometer feed for the BMW tachometer (suggestions and insights appreciated).

 

My understanding of MSD history is its an abbreviation for multiple spark discharge. Apparently at low rpm they "ring" the coil to ensure complete combustion in slow cylinder fill speed conditions. For my past street cars (they are all DIS now) the cold idle was definitely smoother; any other differences I'm sure are imagination. For my track car, definitely improves combustion at all rpm (max 6,500 when E303 cam stops breathing) with tuned-for-torque 5.0L engine (much much fun to drive).

 

Will the MSD compensate for BMW lean burn driveability? Maybe. If it does is it a better solution than an AF-XIED. Definitely not! The AF-XIED is a well-engineered device supported by instrumented measurements with simple installation and configuration. I'm pursuing this MSD experiment as a lark in response to Roger 04 RT's question. Why? Like the dog licking his...because I can.

 

I'm working on posting photographs and wiring diagrams.

Link to comment
Bert Remington

he MSD CDI is of interest due to the very oversquare design of the R1100 engine. I believe BMW chose this oversquare design to reduce width at moderate cost. BMW went to a two-inlet/two-exhaust valve configuration to improve cylinder fill and empty speeds. However the flame front propogation speed across the wide bore along with varying piston and cylinder head temperatures makes complete combustion difficult, especially with environmentally-responsive lean fuel-air mixtures. BMW chose to retain the Kettering (inductive) ignition. I don't know if this was the cause of driveability issues for many riders but the later R1150 engines went to a twin plug configuration which I believe was intended to address the problematic lean-burn initial ignition and flame front propogation characteristics that I and many others believe are the underlying cause of the driveability issues.

 

If the BMW is a high-swirl design then the multi-spark nature of the MSD offers the possibility of more complete combustion as the unburned mixture passes by the repeatedly-firing spark plug. This more complete combustion should be more noticeable at low rpm where the intake manifold, piston, and cylinder head have more time to cool and condense the fuel-air mixture before ignition. (In an undersquare design the cylinder wall becomes more of a factor.)

 

At higher rpm the essentially constant capacitively-stored energy discharge of the CDI overcomes the decreasing energy of the Kettering ignition (the decreased dwell time reduces inductively-stored energy). While driveability is less of an issue power production is.

 

I believe the more favorable fuel-air ratio provided by the AF-XIED is a better driveability and performance solution than the multiple high-energy sparks provided by the MSD. I'm not getting rid of my AF-XIED...I'm just leaving it in the box for awhile until I get this MSD thing out of my system.

Link to comment
WindyKnowItAll

Just my opinion here... There's no reason to wait on the AF-XIED install (except for the dread tank removal) while considering the ignition upgrade.

The only issue I have with the MSD CDI is unknown reliability compared to stock. I just don't have any knowledge about it.

Yes, the twin plug, the stick coil, and multi-electrode plug were all attempts to get the too-lean and somewhat lopsided non-swirly mix to light.

It does seem to me the CDI solution might be better.

As far as power production at the high end I have my doubts you'll see a big improvement there on this engine.

It does start breathing more efficiently around 4500 RPM and from what I can tell the computer shifts into a slightly rich mode anyway.

I guess I'm saying that the issues the CDI addresses may not really exist at the high end of the RPM range.

That wouldn't stop me from installing it though.

Link to comment
Bert Remington

First, a progress report. Searching through my electronics bins I discovered another MSD 6AL with 8830 filter on a mounting plate. I think it was for an 1.8L Integra but the Integra experts talked me out of modifying the ignition (I wish someone had talked me out of Integras entirely as they are a sad, expensive story for me).

 

So I tried fitting it behind left footrest plate. Almost...loosened three front 6mm bolts about three turns and it slipped right in. The MSD 6AL mounts at its four corners and the footrest plate has two bolts (for BMW power-port bracket). I will make an L-bend mounting bracket where the bottom of the MSD and footrest plate bolts penetrate one side and the other side provides a heat-shield from the exhaust. The mounting bracket will be parallel to the exhaust and will have aluminum-coated protective mat facing the exhaust.

 

The 8830 filter capacitor will be mounted behind the starter, either tie-wrapped to a flange on the airbox or with another mounting bracket fastened to the transmission.

 

And I retain access to the rear shock rebound adjuster!

 

The tight space constraints for both the two footrest plate bolts and four MSD bolts means the MSD+mounting bracket must be removed as a single assembly together with the footrest plate.

 

Remove/replace won't be much of an issue. I will use one 2-pin waterproof connector for the coil power and another 2-pin waterproof connector for the ignition enable and trigger. Primary power is #12 with screw lugs on the 8830.

 

Heat of course is a concern. While moving you have the rear wheel acting as a fan. While stopped the engine is producing less heat. Stop-and-go traffic in the summer is most likely to produce heat buildup. This is the closest I've mounted an MSD to an exhaust system but I think if the ABS luggage can take the heat so can the MSD.

 

The other concern is water intrusion. Driving my track Mustang to Buttonwillow one summer I went through rain that was inches deep on I5 North. Track tires are not fun in the cold or deep water so I stayed in the right-hand lane about 50 yards behind the trucks. My MSD system is in the area between the left fog light and front wheel. Never misfired even when the smog pump water-locked and sheared off its three pulley bolts. So between MSD's design and my installation methods I think this won't be a problem.

 

WRT to the BMW tachometer feed I examined the BMW coil thoroughly and could only find four wires: two secondary wires and two primary wires. So I believe Doug Raymond's schematic does not apply to my BMW. Therefore I'm don't think there will be any tachometer issues.

 

Second, addressing WindyKnowItAll's points (thank you for your analysis): I want to keep the MSD and AF-XIED modifications separate for the moment to better understand the MSD's effects on driveability and performance. My experience with the MSDs >I< installed is 0 failures and 0 misfires under all driving conditions (none off-road). Non-swirly fuel-air mixture...sigh. But I can hope. I concur on performance but since my age exceeds the Descanso-San Diego I8 speed-limit I don't see 5K+ very often so this is a lost performance measurement :). And yeah this is a crazy installation. And I don't seem to be able to stop myself from proceeding with it.

 

My neighbor will configure my website so I can publish photographs and drawings but I haven't asked her yet.

Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...