DIY Fitting EFI

[MrPerkles]

My car a 1978 SC shell with Carrera 3.0 engine was imported from the USA and fitted with 46mm PMOs carburettors.

Now there are many debates on the Porsche forums regarding sizing of these mechanical contraptions. My car has a 3.0 litre engine some say 46s carbs will be perfect some say 40s.After many frustrating dyno hours I decided for myself that 46s are to big for a 3.0 litre engine, the carbs either ran very lean with smaller jets or very rich with the next size up making it a 10mpg fuel guzzler, good for Gordon and his treasury but not for my cake and Stella fund.

The engine just didn’t pick up correctly and always felt bogged down unwilling to rev.Pumping the accelerator to start the engine like some spiritual ritual also didn’t float my boat so it was time to move on but where ?

 

After reading various posts regarding EFI and throttle bodies including converted bike kits and 3.2 set ups I decided an aftermarket kit would be more plug and play and the correct way to go.

One thing I didn’t want to lose was the look and the induction noise of the carb set up, the ram pipes and high air filters also finish off the perfect engine bay landscape.

I have no electrical experience at all I cant even remember the last time I wired 3 pin plug,I didn’t know what a relay did or how it worked before this project. Even if you are a novice thinking about this conversion please read on, it is definitely a project a novice can take on with a bit of help and investigation on the usual forums

 

I found out Jenvey Dynamics were down the road from me and after a few investigative phone calls I wrangled a deal and bought a 48mm 2 stud taper kit,later cars are 3 stud. You can over size a throttle body set up and get away with it more than carbs; there is a useful sizing chart on the Jenvey website if you are unsure what size to go for.

http://www.jenvey.co.uk/

The kit includes ram pipes, throttle linkages manifolds and also an option for an air filter set up which I decided to leave for the time being.

 

 

The following items would also need to be purchased to make a complete kit and a finished system. I also suggest a good soldering iron,industrial crimpers,multimeter,cable, fuses,various quick fit connectors and a decent timing light.

 

• ECU

• Wiring loom

• High flow fuel pump Bosch 004 or similar & 3-5 bar fuel regulator

• Relays and various wiring connectors

• Fuel hose

• Throttle linkage rods

• Air Filters

• Fuel injectors x 6

• Coilpack

• Longer plug leads

• Crank trigger wheel

• Distributor plug

• Dyno set up

 

My engine has 39mm intake ports and the Jenvey kit I bought tapes from 48mm to 41mm so I had to resolve the 3mm step.

PMO supply spacers for their carbs to eliminate heat sink from the engine ,I fitted a set to the Jenvey manifolds and ground a smooth transition from manifold to spacer. From ram pipe inlet to head inlet my throttle bodies now taper from 48mm to 39mm.

Next I drilled and tapped into one of the manifolds for my vacuum line connection for the brake servo. You can also chose to run a MAF sensor and use the same ports back to a common manifold block if desired.I built the kit up off the car including the throttle linkages as the supplied diagrams and put it to one side

 

You need to decide on your injector sizing, a good reference for this is http://www.rceng.com/technical.aspx

Injector selector

If you over spec you can turn down the fuel pressure although idle may be effected

 

Along the way I made a few mistakes that cost me a lot of time and hassle .For anybody doing this from scratch I suggest setting out by building the throttle bodies up and setting them to one side and concentrating on the loom ,ECU and sensor locations. At all times make sure the open ports are covered to stop any debris falling into the engine.

 

There are many options for ECUs ,Omex,DTA,Emerald,Megasquirt, Motec.All have different prices and options, my car is never going to be anymore than a fun Hot Rod,I needed value for money and most importantly advice and telephone back up.

I investigated all the options above and decided on the Omex 710. Omex were very helpful and I had also seen a few early 911s fitted with the same kit.

Edited May 13, 2009 by MrPerkles

[MrPerkles]

I located my ECU as shown in the photo under the driver’s seat safe and out of the way fixed with super strong Velcro on an aluminium tray.

The live for the ECU and fuel pump were taken directly from the battery and wired to a switch I fitted to the dash, a fused relay was wired into each live.

The loom was routed through the lower rear bulkhead in the same position as a 3.2 loom and protected with flexible plastic conduit.

At this point I made some mistakes, firstly I suggest working out where each sensor goes and fit them first prior to deciding on where the loom will terminate.

 

The sensors and lives for my set up are as follows.

 

• CHT cylinder head temperature

• Crank trigger wheel sensor for timing feedback

• Air temperature sensor

• Lambda sensors x 2 one for each bank

• Throttle position sensor

• Coil pack triggers and lives

• Injector triggers and lives

• Earths

 

The most important sensor to locate is the CHT which should be fitted as close to the head as possible preferably cylinder no3.If you have a 3.2 engine this sensor exists fitted to the side of the head under the tin work

Omex use a Bosch V6 Omega coilpack,I picked one up off Ebay for £17 and fitted it central on the rear bulkhead using anti vibration mounts

Edited May 13, 2009 by MrPerkles

[MrPerkles]

I took off my heat exchangers and welded on two bosses for the Lambda sensors one for each bank. You can tune and balance each cylinder bank and the Lambda sensors also monitor AFRs giving smoother running and improved mpg.I used pre heated sensors which get up to temperature instantly and work from cold start up

Next I pulled out the distributor as I was converting to a crank trigger wheel and sensor to monitor the timing,the distributor hole was blocked off using a Clewett distributor plug complete with “O” ring seal

You will need to buy a 36 tooth wheel for the Omex ECU ,I marked a annulus on the OE crank wheel in a lathe and marked out a PCD for my mounting holes.

It is important to space the trigger wheel off the OE crank pulley wheel to avoid crushing it by using washers,fix it tightly with threadlock.

The trigger wheel has a missing tooth for pick up by the trigger sensor this needs to be mounted approx 30 degrees BTDC.I suggest marking TDC prior to taking off your distributor otherwise you will have trouble finding it again

OE crank pulley wheel

36 tooth wheel

Fitted , lightened and balanced on a lathe to keep it true

You will need to decide where you are going to mount your sensor and make a permanent bracket with some adjustment for set up.

I took of my engine beam and welded two studs central to the crank pulley, machined a bracket and fixed it offset for later access with a timing light.You will need aprrox 1mm clearance to the trigger wheel hence why you should take time to fit it radially true.

Once fitted use a 1mm feeler gauge and turn the engine manually to check for clearance issues

Why crankfire ? it gives a clearer and more contollable signal than a distirbutor and the ability to control advance in more regions of the rev range.

If you decide to go twin plug in the future it is far more cost effective than the expensive Porsche dual distributors ,£25 for the toothed wheel £12 for a sensor,a coilpack from a Ford or similar car or aftermarket such as Clewett.You can make you own bracket and fit easily.The ECU has the software built in to control the crankfire system and you wont ever need to set points again.

 

 

Next it was time for me to tackle the wiring the part I wasn’t looking forward to,at this point I decided to use quick fit connectors and make a mock up to test the system prior to cutting any of the loom back.

I left my loom uncut and connected all the wires as the Omex manual,routing it out of the rear firewall terminated at the engine bay fuse board.The looms wires and manual use colour codes and surprisingly I made no mistakes on this part of the project, in fact I found the wiring quite a relaxing exercise once I had got my head around what relays, fuses and power supplies would be required.

With everything fitted I tested power to the engine bay fuses and connected up to the laptop,Omex use a operating system based on windows, my USB port wouldn’t recognise the ECU and after a phone call to Omex the problem was diagnosed and I needed to turn up the Baud rate setting in the software.

Now we had connection and all the sensors were showing sensible readings as suggested in the manual.

When you purchase an Omex ECU they will send you a start up map that you download to your ECU drive, I loaded the map and rebooted the system.

Time to try and start the car, this is quite a nerve racking experience, have I dropped something into one of the ports, is it wired properly, why didn’t I just leave it alone (words of the wife) what if it runs to lean and explodes!

 

On initial start up Omex give you a sequence of checks and procedures mainly related to timing and fuel rate.

 

Turn the key fuel pump whirrs into life for 5 seconds and cuts out, strange why does it do this. I learnt most ECUs prime the system prior to turning the starter motor then cut back in again, the wiring is also configured to cut the fuel pump off in the event of a crash or other problems with the engine.

 

I turn the key and crank her over again, we have spark, we have wet plugs but she’s not catching.

I decide it has to be the timing out as the crank wheel and sensor need to be configured as you would a distributor.

Edited May 15, 2009 by MrPerkles

[MrPerkles]

The next point to consider is how your ECU has been wired to the coil pack and how the coil pack fires, mine has been set up to run wasted spark. My cylinders were wired as pairs 1 + 4 ,6 + 3,2 + 5 Omex state this reduces load on the drivers although I am unsure what real effect this has, it is worth noting for set up you will get a double reading on your timing light due to the wasted spark.

 

Each unit added to the timing input retards the ignition by 30 degrees of the crank,you will need to find what the base setting of your trigger wheel is showing.

The only way to do this is with the help of a friend and a good old fashioned timing light.

I pulled all the plugs except for cylinder no1 for less compression and with the help of a friend Higgoe turned the engine over until I got a reading on the timing light. The timing light was showing 18 degrees of advance so I needed to work out where I needed to be for 0 degrees to be safe.

 

Once the timing was set as close as I felt safe, Jeremy from MBS car parts came over and helped start her up again.

The car was very close to starting and eventually it spluttered into life when I upped the fuel loadings, what a moment of relief, joy and fear if it was running to lean.

 

Omex commented my fuel loading was very high suggesting low fuel pressure this was confirmed by Bob Watson when he looked at the set up.I had used my original PMO fuel regulator which was set at 3psi ,what a stupid mistake EFI requires 3-5 bar

 

I shut her down content that the loom was wired correctly and made a list of tidy up jobs prior to the dyno set up.

 

I cut back the loom soldered in all the connections and labelled any important connections for trouble shooting at a later date.

I now needed to fit my air temperature sensor in a fixed position and also order some air filters.

Edited May 13, 2009 by MrPerkles

[MrPerkles]

I didn’t want to buy the Jenvey filters as they hide the ram pipes and are also expensive. After a bit or research I called ITG and popped in to see what they could do. The normal base plate and filter set up again was very costly and was a retro fit to the ram pipes. I couldn’t work out an easy way of fitting the base plates to the ram pipes without fouling the throttle linkage or drilling into the pipes.

ITG suggested a custom set up made from a simple filter sock and showed me a picture of a beetle set up which looked good and was 50% cheaper. The filters would also sit high on the ram pipes and show off the bling .Measurements were taken and the socks were ready in a week, great service and ITG have kept the patterns.

I fitted the air temperature sensor to a throttle body spacer on a bracket positioned to enable it to poke into the filter sock. Hopefully this would give a true reading of air temperature going into the ports.

Other jobs I tackled was to rewire the OE engine harness, ignition switch, headlight switch and starter motor cables, all had eroded and crumbled away over time. It is also worth checking your earths and replacing if necessary to avoid any problematic electrical gremlins at a later date

So next the car was loaded on a transporter and taken to Bob Watson Engineering for it to be set up,dont be fooled this will cost as little as a normal remap.Each throttle body needs balancing and setting up individually,the base map has to be tuned in small steps to avoid detonation and requires several dyno runs,then cold start maps need to be figured out in conjunction with the CHT sensor

 

List of suppliers I used and recommend

 

http://www.omextechnology.co.uk/ ECU

http://www.jenvey.co.uk/ Throttle Bodies

http://www.cbsonline.co.uk/ Throttle linkage parts, consumables

http://www.mbscarparts.com/ Porsche parts and potatoes

http://www.merlinmotorsport.co.uk/ Consumables & throttle linkages

http://www.lister.co.uk Fuel hose and fittings

http://www.magnecor.co.uk/ Custom made lead sets

http://trigger-wheels.com Trigger wheels and sensors

http://www.clewett.com/ Distributor plug

http://webpro.touchoxford.com/webpro/live/bobwatson/ Dyno set up

http://www.itgairfilters.com/ Custom made air filters

http://www.americanv8engines.co.uk/ Accel fuel injectors

http://www.rceng.com/technical.aspx Injector sizing chart

Would i do this again ? Dont know to early to say ,I test drove the car 100kms last night and it certainly felt better ,the cams have now come alive and it idles far better ,runs soother to the redline and the mpg is vastly improved.The bhp isnt far up but I put that down to the to the top end needing a refresh ,yes that was my bad news.

In reflection I would suggest finding a 2nd hand motec unit off ebay (£1500) and taking it to a motec dealer to fit or tune,Omex are at an early stage in the aircooled 911 game.My base map was wrong and also the wiring diagram ,Kudos to Bob Watson for sorting this all out.

 

Next test Lemans track day next week.............will it survive ?

Edited May 13, 2009 by MrPerkles

[heckschleuderer]

Superb write-up!

[TimNiceBut]

+1 - well done, and a good read.

[Bertroex]

Andy,

 

Superb piece of work: first the learning curve you went through and then this write up.

 

However: for someone doing quite a lot of miles per annum (14000 to 20000), and running the standard K-jet on the C3 and having it serviced as it needs to be, I'm achieving an average of 27mpg.

 

Once warm, I drive it in the upper 40% of the rev range, so I'm not holding back. Even when cruising on the motorway I regularly shift back 5=>4=>3=>2 and redline redline redline and gradually back off to a cruising speed between 3300 and 4000 rpm.

 

About 16000 miles after my engine rebuild, Mike Bainbridge measured and checked the engine whilst it was out and it is a cracker and all within tolerances (except the intermediate gear- something that the bloomin' helmut- in- the- fatherland DID NOT change RAAAH).

 

My questions now:

-why EFI over K-jet?

*Performance advantage (what about a heater backdate, SSI, rally exhaust instead)?

*Fuel consumption (tanking optimax 99RON or whatever and achieving 31MPG on a a k-jet rather than 95RON supermarket fuel and 27MPG)?

*Better wear and tear (over what timespace and with how many miles)?

 

I'd welcome your comments and really wonder whether you would expect a SIGNIFICANT advantage in 3000 miles. (All the low mile 911 I had came "loose" after about 2600 to 2800 miles or a good 6 weeks of Bert's Antics Behind the Wheel)

 

 

Best regards,

 

 

Bert

[Jammo]

Well done Mr P,

superb write up and the balls to 'have a go'. Well, fire extinguisher at the ready old chap and off to the track with you.

 

Seriously - excellent work, pictures and write up.

Good luck with her.

Regards

 

Jammo.

[johndglynn]

27 is good Bert. I would expect to get minimum 30% increase in efficiency on mine with ITBs.

 

Advantage of EFI: gets rid of all that CIS scrap metal and gummed up mixer head etc. Gives you complete control over proper injectors - not just dumb mechanical squirters. Deletes all the vac pipes, sharper response thanks to straight run to the cylinders from the TBs.

 

Better intake means you can run better cams and make more power. Much more than just SSIs alone though they are still de rigeur on a 3 litre.

 

Main thing is bigger intake charge and the flexibility of fully mappable fueling (switching off on decel etc). CIS is an old, unintelligent system, plus it wears out a treat. You don't need to use 98 Ron.

[Chris_911]

Good work Mr P.

[Kieran T]

Mr P

That is an excellant write up and indeed a voyage - I'm sure you will now enjoy the car more knowing it as intimately as you now do -

Top end rebuild next eh?

Be sure to lay in some extra Stella & Choccie cake

Well done - I think this "Wrap up" thread is great

Kieran

[mean in green]

The Playboy socks must be worth 5bhp?

[Northy]

Some of the photos aren't showing for me, but did you include the money shot? A photo of what the finished installation looks like. It's car porn.

[burgundyben]

Eggsellent write up Mr P, one of the most informative on IB.

 

I wonder what the payback will be on fuel, depends on mileage I guess (plus of course other benefits).

 

You've answered a whole load of questions I had.

Edited May 13, 2009 by burgundyben

[Phill]

Awesome. Must have been mega intimidating at the start.

[MrPerkles]

Andy,

 

Superb piece of work: first the learning curve you went through and then this write up.

 

However: for someone doing quite a lot of miles per annum (14000 to 20000), and running the standard K-jet on the C3 and having it serviced as it needs to be, I'm achieving an average of 27mpg.

 

Once warm, I drive it in the upper 40% of the rev range, so I'm not holding back. Even when cruising on the motorway I regularly shift back 5=>4=>3=>2 and redline redline redline and gradually back off to a cruising speed between 3300 and 4000 rpm.

 

About 16000 miles after my engine rebuild, Mike Bainbridge measured and checked the engine whilst it was out and it is a cracker and all within tolerances (except the intermediate gear- something that the bloomin' helmut- in- the- fatherland DID NOT change RAAAH).

 

My questions now:

-why EFI over K-jet?

*Performance advantage (what about a heater backdate, SSI, rally exhaust instead)?

*Fuel consumption (tanking optimax 99RON or whatever and achieving 31MPG on a a k-jet rather than 95RON supermarket fuel and 27MPG)?

*Better wear and tear (over what timespace and with how many miles)?

 

I'd welcome your comments and really wonder whether you would expect a SIGNIFICANT advantage in 3000 miles. (All the low mile 911 I had came "loose" after about 2600 to 2800 miles or a good 6 weeks of Bert's Antics Behind the Wheel)

 

 

Best regards,

 

 

Bert

Hi Bert

I needed an instruction paint by numbers manual to work from and I dont know anything about K-Jet

Jenveys also look and sound like carbs,I am weird and like to look at my engine and also listen to it make funny hissing noises

I have SSIS and a two in two out M&K

I will do a proper fuel consumption test to lemans next week,last night I kept booting it chasing Mr North

Wear and Tear ? dont know but I do know I can fix it myself so wont have to rely on anybody except for dyno runs

Again to reiterate the reason I went EFI was to ditch my carbs

Edited May 13, 2009 by MrPerkles

[Northy]

Last night I kept booting it chasing Mr North

B4100 Banbury to Warwick - what a great piece of road

 

EFI has got to be better than 70s technology - I've seen it, it's the future.

[Tripe]

Got to doff your cap to an achievement like that, top work Perkolator. All your hard work has paid off.

[MaxDiesel]

Excellent write up Mr P That's an impressive DIY project to take on - I'm sure it will inspire others to do the same. Good to see the Stella made a regular appearance.

 

The final install looks fantastic

[Von Twinzig]

Great write up Andy. Have to agree the engine bay looks clean and uncluttered and the sound must be fantastic. Looking forward to some power runs on the French Autoroutes. Well done mate.

[tea boy]

the reason I went EFI was to ditch my carbs

 

 

The best place for carbs is in a ditch, for sure.

 

Mr P you are my electronically controlled hero

[MrPerkles]

Mr P you are my electronically controlled hero

Thanks TB I must admit im a dab hand with a rampant rabbit

[johndglynn]

Thanks TB I must admit im a dab hand with a rampant rabbit

They are for the girls mate. Leave it in her bedside cabinet!

 

Unless you are talking about a real rampant rabbit in which case: urgh

[flatsix777]

That's an outstanding piece of work - looking forward to seeing it in real life.

 

CIS isn't easily adjustable for a modified engine, only controls fueling so can't help you optimise timing and there's nothing to detect & stop your AFRs going catastrophically lean if something fails when you are giving it death on track, albeit less likely on a n/a motor. I like CIS, partly because it's a challenge, but the great thing about this is that Andy did it himself.

 

Cheers

David