A lengthy EFI Conversion

[decoupe]

This first post (of a series that I will continue to update) is to share what will be a very aggressive learning curve for me with respect to converting a fairly basic engine system to something much more sophisticated. The why part is not as important as the how to.

I’m converting my very well sorted twin Weber 38/38 downdraft 3.5l - with a mechanical distributor and 528i engine module - with decent power and very smooth delivery from idle to wide open throttle (yes that was an advertisement for a sale as a package when I’m done) to a fully programmable distrbutorless ignition and EFI system. The car is essentially an early 80’s five series drive train from the fan to the rear diff and OEM stock originality is long gone. It was like that when I bought it and I’ve continued down that path with various small projects (battery under the rear seat, A/C delete, rear seat delete) with a view to reducing the weight of the car and increasing my skill set.

The SDS system is an integrated fuel injection and ignition system. Engine spark timing is fully programmable for both RPM and load (manifold pressure/throttle position). Programming is done with the standard LCD hand held programmer. Triggering is accomplished with magnets attached to the crankshaft pulley and a Hall effect sensor fitted to the timing cover.

Three triggering magnets are used along with one sync magnet that is used to synchronize the computer with the engine so the computer knows which coil to fire. As each magnet passes the Hall effect sensor, a pulse is sent to the ECU. The ECU determines the exact rpm and manifold pressure, sums the programmed spark retard values and calculates the appropriate delay for the specific conditions at that instant, then triggers each coil to fire at the precise time. Each coil fires two cylinders simultaneously, while one cylinder is on compression, the other on exhaust.

The system measures air temp entering the throttle body (TB) and engine temp in the water jacket and controls start to fast idle to warmup/kick down air/fuel ratio in the ECU so several of the water houses will be eliminated and the ports covered/closed (something to fabricate). A MAP sensor and a throttle position switch provide volume and density of air data to the ECU in order to determine duration of the injector pulse.

For more information (and to correct anything I have misspoken) try http://www.sdsefi.com.

To date, I have gutted the engine of everything that is to be replaced, removed anything that was /is going to be in the way and come up with a bunch of other ideas that will make the task even bigger than I thought it would turn out to be. Typical. Oh, and my life got in the way as well.

I had to fabricate a bracket to mount the trigger sensor that picks up the magnetic field of 4 magnets in the back side of the engine dampener/crankshaft pulley. The location, spacing, and depth of the holes is precision work so a machine shop took my markings, checked and drilled the holes into which I epoxied the magnets.

The recommendation for the bracket was to make it strong enough to lift the engine (ie no movement or vibration) so I used ¾” aluminum plate and between the jigsaw, hacksaw, drum sander and files produced a spacer and bracket that bolts into the A/C mounting holes cast into the block. Drilled a couple of holes (measure, measure, measure) in the bracket for the sensor and this is DONE. Almost. Need some final shims to bring the sensor 1.5mm from the magnets.

I found a very nice aluminum distributor hole plug meant for 2002 EFI conversions from Tom at http://www.02again.com/ - a perfect fit and nice quality. He also had a TPS Adaptor Plate that was, again, a perfect fit on the throttle body and compatible with the SDS system.

I’ve been doing some dry fitting of the intake components and throttle body to see if there are any issues that need to be resolved (duh) before starting on the fuel delivery system with a La Jolla in tank pre-pump and sending unit , EFI fuel pump, surge tank, fuel lines, injector servicing …. Lot’s of stuff and order more parts.

Sorry about the length. Enough until there is more.

Doug

 

[OZCSi]

Nice, I will be keen to follow your progress.

Cheers

 

[Ed G]

Would be great to know if you were able to document any pre-op performance specs.

 

[decoupe]

G - it was dyno'd about 3 years ago so lots of baseline. The timing was off - not enough advance for altitude. I think it was 176hp and 205ftlb torque. This was at the rear wheels of course.

Doug

 

[AndyM]

Doug -

It looks good! I have practical solutions for the throttle position sensor and air bypass valve that may work for you if you need them. Keep us posted!

 

[decoupe]

Andy:

I have the TPS mounted with an adapter plate from o2again.com that is used on MS conversions. Looks like it will work.

SDS supplies a fast idle option that consists of extra circuitry added to the ECU, a control wire, a modified relay and an air bypass solenoid. When the coolant or CHT is below a certain temperature, which is now user programmable, the ECU commands the solenoid to open and bypass aditional air past the throttle plate to increase idle speed. Installation requires running 5/16 vacuum hose from the air filter to the solenoid and from the solenoid to the intake manifold. The control system is either on or off. There is no proportional control of rpm.

Currently ordering the next round of parts from Steve Blunt - a well known purveyor of advice about and the necessary parts in the '02 world. Also some block off plates and plugs for some redundant ports on the fuel rail, TB and intake manifold.

Doug

 

[AndyM]

Cool. Looking forward to seeing the final results.

 

[decoupe]

EFI Update

I’m doing a lot of problem solving on a platform that has pieces of several different generations and models of early BMW’s including CS, 535i, 528i and a dash of 6 series – none older than 1988 (I think). The CS/CSi Blue Books were a good start but I’ve had to buy a 77-81 528i Haynes manual (out of print) off ebay. Waiting for my next order of parts and this manual has left me free to sort out the additions and deletes on the intake and fuel delivery end of things.

The elimination of several components common to both the CSi D-Jet and 528i L-Jet fuel injection and ignition management including the auxiliary air valve, A/C idle valve, thermo time switch, air flow meter, cold start injector and start valve and several hoses related to fuel supply, coolant and vacuum mean I have several openings, ports and barbed hose connections to deal with. The attached shows the extent of this.

The little time I have spent over the last month on the conversion has been spent using my low tech fabricating skills and tools (Dremel Multi Pro, jig saw, hack saw, various flat files and chain saw file) and flat aluminum stock to do the best I can in the absence of a CNC machine shop. The barbed fuel connection on the fuel rail and some of the vacuum ports and coolant ports on the intake manifold will get welded and ground smooth. Very few of these will be visible once the whole thing is reassembled so perfection is not required but I’m fussy about doing a decent job so the amount of time I’m spending on second and third attempts is all out of proportion to the final product.

When this is finished there will be considerably fewer hoses of all types, fewer associated components that were reading engine temp from circulating coolant and a more minimalist appearance with the long block, intake and throttle more visible which is fine with me but probably not everyone’s cup of tea. AndyM made his goal to have a more correct appearance with his Mega Squirt EFI conversion and I think he succeeded and I hope to do as well but in a different direction.

My just recently serviced and refurbished OEM injectors are on their way back from Lake Havasu City, AZ so I can start reassembling the fuel rail and building the new fuel delivery system.

Doug

 

[decoupe]

Conversion Completed

May 30/10

This is the last update before powering up the car to test the new fuel system, starter, SDS ECU circuit and all of the old wiring circuits I hopefully haven’t buggered in the process of adding a stand-alone engine management system to a 37 year old electrical system.

To recap, this whole project really boils down to deleting the original ignition system consisting of a mechanical distributor, coil and an ignition module from a 528i and associated wiring and replacing it with a fully programmable ECU and wasted spark coil pack that is timing triggered by a sensor reading engine position for timing off magnets located on the engine dampener running off the crankshaft. At the same time the twin 38/38 weber carburetors and intake manifolds were removed along with the associated cooling hoses and fuel pump and replaced by the throttle body, intake manifold, fuel rail and injectors from a 1981 528i and a new high pressure fuel system.

The new high pressure fuel system consists of a Walbro EFI pump, OEM CS hard fuel line along with a new pre-pump (from La Jolla Independent) in the fuel tank feeding a 4 line surge tank – all of this ending up in the trunk. The fuel line is pre-bent from the factory, which made shipping via US Postal problematic – the line was carefully coiled before packing and uncoiled at this end with no problems. The last 1/3 was re-routed anyway to enter the trunk at a different location determined by the EFI pump. Everything zip tied to the old line or fixed points along the way.

SDS recommended using a 4 line surge tank mounted above the level of the EFI pump to ensure no risk of fuel starvation during “aggressive cornering”. The EFI pump is feed from the bottom port and the pre-pump, the return line from the engine (using the existing fuel line) and the return line to the fuel tank all (top of the surge tank) all connect above it. It’s 60mm diam aluminum tubing - volume is just over 1 litre and is bolted to the floor. I call it “the squid”.

The installation of the coil pack, resistor pack (for the low impedance injectors) and the fast idle solenoid all ended up on the exhaust side of the engine and in spite of what seems to be a cavernous compartment had issues with clearances and mounting. The best location for the coil pack required pouring a mounting block using a two component urethane casting system. The coil pack is bolted through the block to fender.

The fast idle and the resistor pack are attached to the firewall with great difficulty and at this point I realized life and the retrofit would have been much easier if I had taken 4 hours (or less) to remove the engine. This would become even more apparent as I got into deleting the old ignition circuit from the wiring harness and installing the new. Live and learn but the difference would have been huge.

The in order to delete the original ignition system, I opened the original wiring harness, including the engine test plug, from the coil back to the fuse panel and closed it back up – all of this in situ. This was replaced with the SDS ECU, numerous sensors (MAP, Air, Coolant, Vacuum, timing), wiring harness(s), richness control module and LCD programming unit. Sounds like a lot of work but really just wiring to run to specific locations with terminations already attached – all this in lengths I specified or could trim to length.

In addition to the SDS electronics package I added a power distribution block located near the hood lever to split the battery main from under the rear seat to the starter and stereo amps, a new sub-panel and alternator. The sub-panel was added so I didn’t have to mess with the stock fuse block and feeds the relays (lights and horn) in the engine bay, new fuel pump (s), and SDS power needs. Three relays in the passenger under dash send +12v key switched power to the fuel pump, fast idle solenoid and SDS ECU, injectors and coil pack. Again sounds like a lot of work but just wiring and fortunately all stand alone from the original wiring harness. The last item installed was a SRx441 starter. With the manifolds off this was a great opportunity to remove (a miserable job) and replace the OEM starter for something lighter and more powerful.

The mandrel bent 3” diameter aluminum tubing, couplers and clamps for the air intake are on the way from Florida. I’ve picked up the cheapest cone air cleaner I could find (really bling) until I have time to build a cold air box.

All of the wiring for the SDS sensors (timing, air, water, throttle position etc) and the alternator, regulator and temp gauge are in looms tied to the fuel rail behind the air runners. The 8mm fuel return hose from the fuel pressure regulator is also tucked in behind the runners. The wiring looms run along the suspension brace to the old A/C hose firewall penetrations. The net effect is a neat uncluttered engine and everything protected but easily accessible.

The whole thing is pretty much complete and I’m checking the systems one at a time. At that point, by the end of the I’ll be ready to turn the key. Actually I did turn the key to check the ECU circuit and it's alive.