Mercedes W114 250 Coupe - help!

[grober]

dup
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[Charles Morgan]

I suspect my needs will be more than satisfied without that level of accuracy!

Edis is my preferred coil pack solution as it is superabundant and therefore inexpensive, plus it has no need for a cam sensor.

 

[Charles Morgan]

Edis coilpacks, module and bits and pieces ordered today. SM will go on a ramp on Wednesday for a good look at the flywheel and the sensor suite as well as me have a good look at a E30 325 with the M20 engine to look at sensor locations etc. The aim is to start drawing up a spec for the MS conversion so that everything is thought through first.

Analysing the SM there are sensors in the inlets (one immediately after the filter (MAP?) and one in each manifold - temp sensor),TPS, CPS, Lambda sensor, and coolant temperature sensor. I need to locate the latter two.

 

[grober]

MS1/Extra Ignition Hardware Manual
or possibly better

http://www.megamanual.com/ms2/

 

[grober]

MS1/Extra Ignition Hardware Manual
or possibly better

MegaSquirt-II - Advanced Electronic Fuel Injection Computer by Bowling & Grippo ©2005

oops see this was posred before by you Charles.

 

[Charles Morgan]

Never hurts to be reminded!

 

[Bellow]

Analysing the SM there are sensors in the inlets (one immediately after the filter (MAP?) and one in each manifold - temp sensor),TPS, CPS, Lambda sensor, and coolant temperature sensor. I need to locate the latter two.

Inlet sensors - the MAP sensor(s) will be downstream from throttle butterfly(s) so the one immediately post filter most probably for temp.
Coolant temp sensor - begin at the thermostat housing and if not directly there work downwards to find it. Lambda - as close to the exhaust valves as possible is the preferred positioning! It will be downstream from the final convergence of downpipes. I'd imagine there will be two - one for each bank.

The aim is to start drawing up a spec for the MS conversion so that everything is thought through first.

Not forgetting to devise a method of accurately obtaining the 1mm air gap twixt flywheel and CPS (if the flywheel is chosen as 'trigger wheel').

Also, though all crank(nose) wheels appear to have their CPS' mounted at their periphery (radially) there is no reason I can see not to utilise a an axial mounting (as the SM has on its flywheel) utilising a slightly differently formatted wheel. Such an arrangement may liberate a better CPS mounting solution eg, by employing some fixings located on the block's side. More options to muse over....

 

[Charles Morgan]

More options to muse over....

So we have

Sensors
Sensor locations
Mounting location and bracket for CPS
Mountings for other sensors
Location for coil packs and module
Location for MS
Type of MS
Injector spec
Rail design
Fuel pump
Fuel pressure regulation
Map for fuelling
Map for ignition
Loom

Other musings - limp home mode for sensor loss?

(all of this will be considerably easier with an engine back!)

 

[Druk]

Not forgetting to devise a method of accurately obtaining the 1mm air gap twixt flywheel and CPS (if the flywheel is chosen as 'trigger wheel').

Is this 1mm a 'given'? Reason I ask is that during the diesel SL construction I fabbed up this triggerwheel for the speedo and tested it by spinning in the lathe with the pick-up in the toolpost. It worked up to a gap of 3.5mm before refusing to register. Just saying...









.

 

[grober]

If we are talking VR type [magnetic-2wire] sensors here the following evidently applies.
The spacing between the sensor tip and tooth is important. The VR sensor output voltage output is highly dependent on the proximity of the sensor to the passing teeth.
Closer provides a higher voltage signal from the sensor, but too close and the amount of noise created by machining irregularities, scratches, etc., also goes up.
The best bet is to use the sensor gap recommended by the manufacturer, and if that is not available, you may have to experiment.
Sensor gap seems to be universally at 1-2mm depending on sensor manufacturer
VR sensors appear produce a native alternating current which varies in amplitude with rpm presumably a faster change in magnetic flux= more induced energy e.g.
At idle the peak output is approximately 0.6 volts (but could be lower, or higher, than that), at mid-RPM it is likely close to 3 volts or higher, and at very high RPM it might go as high as ~50 volts.
For that reason contrary to what I supposed its more difficult to produce an accurate signal with VR sensors at low rpm than at high due to less signal for processing. Some examples here
Trigger wheels and rev limits
You will be gratified to read Charles that larger wheels produce stronger signals.
taken from MegaSquirt-II - Advanced Electronic Fuel Injection Computer by Bowling & Grippo ©2005 pickups.

ps HALL PROBE type sensors [ 3 wire] evidently generate more signal for processing and are for that reason thus favoured for Camshaft sensors being as how they rotate at half crankshaft speed

 

[Charles Morgan]

I took Bellow's comment to be more about devising a bracket that can supply the necessary gap accurately.

My favoured solution remains the flywheel for reasons of mounting, accuracy and stability. Hence the little trip in the SM tomorrow! (well, that and it needs a good run).

 

[Charles Morgan]

Coilpack kit arrived at 8.40am via the lovely Jan, she who has a VW splitty and who checks up on all the elderly neighbours while on her round, having been ordered at 2pm yesterday. I like that level of service. How it all works is a mystery, but there we are, a monkey has a better chance of writing Shakespeare than a mediaeval history graduate ex banker has of coping with lots of wires.

 

[Bellow]

VR sensors appear produce a native alternating current which varies in amplitude with rpm presumably a faster change in magnetic flux= more induced energy e.g.

And at cranking speed the signal can be very low.

You will be gratified to read Charles that larger wheels produce stronger signals.

Hence my suggestion of moving away from a small diameter trigger wheel with peripherally mounted CPS to a larger one with axial CPS mount. Flywheel has the advantage here though.

ps HALL PROBE type sensors [ 3 wire] evidently generate more signal for processing and are for that reason thus favoured for Camshaft sensors being as how they rotate at half crankshaft speed

Makes sense - especially when the small radius of rotation is factored in.

I took Bellow's comment to be more about devising a bracket that can supply the necessary gap accurately.

Truth be told it was more about being able to verify the gap once installed as once the gearbox and engine are mated there is no access with the CPS in position.

 

[Charles Morgan]

Brake servo decision time. It has some brake fluid from the leaky master cylinder in it, the outside is crusty but getting better with each pass on the wire wheel, but it will never come up particularly well because the rust has made the surface quite pitted and I'm not spending days to get it back to scratch. I can get an ATE oem brand new one for £190.

New or keep?

 

[grober]

Off the top of my head---- if its orginal and part of the brake system ---- maybe a new unit would be best .

 

[Charles Morgan]

Yes - As I've got a new master cylinder and likely some lines (the rear brake lines looked a bit poor) to go in, it would make sense.

 

[Charles Morgan]

Bad news from the body shop. Matt went on an adventure holiday in Wales last week, abseiling, climbing, canoeing and similarly idiotic activities. Which he survived without a scratch but managed to break his leg playing football on the weekend. Another proof, if any further were needed, that sport is bad for you. Certainly not great for a business with lots of prep work on my car to be done in the next few week. Fortunately Dan has some help from Ryan, the car transporter who is also a trained panel beater, but talk about bad timing.

 

[Bellow]

So we have

Sensors
Sensor locations
Mounting location and bracket for CPS
Mountings for other sensors
Location for coil packs and module
Location for MS
Type of MS
Injector spec
Rail design
Fuel pump
Fuel pressure regulation
Map for fuelling
Map for ignition
Loom

Other musings - limp home mode for sensor loss?

(all of this will be considerably easier with an engine back!)

Coil pack under the battery tray - inspired!

More musings....

My flywheel face - too many holes irregularly drilled (for balance I think).

Which means (as far as using the flywheel's own material to form 'teeth') that a peripherally mounted CPS is the only remaining option.

[EDIT PS. Can the other side (engine side) be drilled? Are balance holes on clutch side only? Otherwise following comments re peripheral CPS mounting apply]

And, the peripheral hole in the above pic is the minimum diameter the holes can be. Ideally, given that they are quite large in diameter drilling right through would be the way to go - to avoid a balancing issue accruing from the holes not being drilled to exactly the same depth. This, however, (assuming my calculation is correct) is not viable as holes will share centres with the clutch cover bolts - dictated by having to use the existing three holes which in essence give start points. Thus, there is a depth limit for at least six holes...

...and looking at the above, that depth is not a great amount - but must mimic the open holes behaviour w.r.t magnetic flux. The slot to mimic the missing tooth (as it needs to be cut) will be approx 3.6'' minus the hole diameter - an awkward sod of a machining job and, depending on where it has to be located, may make rebalancing impossible (if material to be removed diametrically opposite coincides with a clutch cover plate bolt). Ascertaining the position of the locating dowel (the seventh hole) w.r.t. TDC will give a clue to the above.

If any of the above is insurmountable, then it's back to a crank nose mounted wheel as triggering method. There is still (I think) a method to get the flywheel to act as trigger (without incurring the problems I have associated with drilled holes.....)

 

[Charles Morgan]

Coil pack under the battery tray - inspired!

John Jones Jr proposed that a few moons ago - it's a seriously good place to put them.

I have done some measuring of the flywheel and think that with spacing evenly it should be entirely possible to drill a 5mm hole and not come close to fouling the bolt holes in any meaningful way, but it does bother me slightly.

 

[Druk]

...and looking at the above, that depth is not a great amount - but must mimic the open holes behaviour w.r.t magnetic flux. The slot to mimic the missing tooth (as it needs to be cut) will be approx 3.6'' minus the hole diameter - an awkward sod of a machining job and, depending on where it has to be located, may make rebalancing impossible (if material to be removed diametrically opposite coincides with a clutch cover plate bolt). Ascertaining the position of the locating dowel (the seventh hole) w.r.t. TDC will give a clue to the above.

If any of the above is insurmountable, then it's back to a crank nose mounted wheel as triggering method. There is still (I think) a method to get the flywheel to act as trigger (without incurring the problems I have associated with drilled holes.....)

Would protruding screw heads work instead of holes? Drilled and tapped into the face behind the ring gear with an adequate gap left for triggering. They couldn't be higher than the bottom of the ring gear teeth or the started dog would foul but that might be enough?