I've decided to sequentially multipoint inject the damned thing, and this page will summarise all my findings and link to all the pages I've found genuinely helpful. There's tons of people out there who will tell you to get injector xyz because injector abc is too small, but unless they have serious proof that the smaller abc injector would perform worse they can get stuffed. Fortunately for me, I've found enough people with the guts to back up their assertions on a dyno to be satisfied that 30lbs/hr - the point beyond which injectors get expensive - will service over 500bhp.
Before you go much further you may wish to check out another site where someone has converted a 351C to EFI using 351W parts for his Pantera, very worth reading. Pay particular attention to the distributor section. You can buy an MSD pro-billet 351W EFI distributor from Summit for US$225 and swap a Cleveland gear onto it and use that instead. See http://www.detomaso.nu/~thomast/efi/ for the article.
Update 01/Dec/2003 I now own a pair of stunning looking Vortech fuel rails from Summit, 30lb/hr SVO injectors, EEC-IV A9L manual trans computer and wiring harness, injector harness, new oxygen sensors, various oem sensors including MAF sensor to fit into a vortech MAF body recallibrated for 30lb/hr injectors, I'm getting there!
Injector types : There are several basic nozzle types. The most common and still the best overall is the pintle type. The others are the disc and ball types. See www.sdsefi.com/injectors.htm for excellent close-up photgraphs.
Impedance : The resistance of injectors falls into two basic ranges; the low resistance, usually around 2.9ohms, is the 'peak and hold' type of injector where the opening current is higher than the current required to hold the injector open. This is the faster responding type, and less common, but be warned that few ECUs will support it. Be warned too that most Toyotas, including 7M-GTE and 2JZ-GTE turbo motors whose injectors are tantalisingly large, are of this type. It is possible to add resistors to these injectors for use on all ECUs however. The second type is the 12-16ohm saturated type, which is far more common.
Injector sizes : I'll assume we're talking V8s here. The smallest injector you'd entertain for a 5 litre (the smallest motor you'd entertain I hope) is 19 lbs/hr and this is stock on plenty of 5.0s. From there the choices in the Ford world are 24 lbs/hr, 30 lbs/hr and 36 lbs/hr. Plenty of larger injectors are available, and plenty of people will tell you that you need them, but here in the real world we'll confine ourselves to engines that are usable. What they never tell you is that too large an injector murders your economy and gives you a dribbling motor that won't idle. Don't believe me? Click here for dyno results of engines making over 500bhp on 30 lb/hr injectors. The second motor in the list is the Lingenfelter 420cid motor, as described in his book (if you've heard of Lingenfelter you'll know he's no fool) and it makes 509bhp from 420cid at only 5,200rpm. The third motor in the list is a 409 cid LT1 motor making 523bhp at 5,750rpm.
Injector Cost : The cost is related to two things; Size, and whether you buy from a pack of theiving bastards like the UK agents for Bosch who want an astonishing 100 pounds each for the bloody things! Ignoring those pricks for a while, the very best prices I've found are again at Summit Racing, and as at September 2000 they are;
They don't price the 36 lbs/hr injectors, but I have seen them for around US$90/set more than the 30 lbs/hr ones elsewhere. I think the reason they aren't listed is simply that they are too big for most applications. After all they're the biggest injectors that Ford make for racing and they also sell superchargers so I'm satisfied that I don't need 55 lbs/hr injectors at US$650/set!!! The fact that Holley fit 25 lbs/hr injectors on their new multipoint injection kit for up to 450bhp, and 31 lbs/hr for 550bhp bigblocks, fills me with confidence, although I don't know what fuel pressure they're running of course.
Mass Air or Speed Density? : These are the two main ways of determining how much air is entering your motor and therefore how much fuel to inject (although with the advent of the wide-band oxygen sensor, wide open throttle (wot) closed loop operation, where the oxygen content of the exhaust is measured and used to adjust the mixture, is now possible where previously it was only achievable under part throttle conditions.
Mass Air sensors measure the amount of air entering the motor by either a crude and horribly restrictive trapdoor, or the far more sophisticated hot wire. With the hot wire the current required to maintain a nominated temperature in the wire is used to determine the mass of air passing it. This type is able to adjust for cams, compression and a myriad of other changes you may make. The wire has a self cleaning feature which 'cooks' impurities off of it, but over time they do deteriorate.
Speed Density determines the amount of air entering the engine by the manifold vacuum (or pressure with forced induction, hence the term 'manifold absolute pressure') and incoming air temperature. Of course both methods also check throttle position, revs, engine temperature etc, but the difference between the two basically comes down to this. The downside of speed density is that a map must be made of the amount of fuel to inject under all combinations of sensor values, and this will need reprogramming when changes are made to the engine such as cam and compression. It relies on knowing the pumping / volumetric efficiency of your motor. This isn't such a big deal, however, and with a laptop either can be programmed to achieve the same power and driveability. Overwhelmingly, the aftermarket caters to the speed density type of measurement BUT as I've just been shopping on eBay as far as I'm concerned you cannot go past a stock 5.0 MAF setup from the '89-'93 mustangs (or '94-'95 which have remote TFI modules on the distributor) with a different MAF sensor body and bigger throttle body.
Sensors : The sensors you will need include;
|This is a graph of the output of a standard narrow-band oxygen sensor, borrowed from someone else's website. All you need is a voltmeter and to make sure the sensor's had time to warm up (if it's an unheated one-wire type, wait 2 to 3 minutes and mount it as close to the head as possible) and you can go to it. Values on the y axis are millivolts, with air/fuel ratio on the x axis. It returns from 0 to just over 1 volt and as you can see, unlike an expensive wide-band sensor, it sort of flops from one to the other as it goes from rich to lean. Hard to determine 12.6:1 for full power, but a good start. Wide-band O2 sensors are over a thousand bucks usually, and can be used for closed-loop at WOT.
Image is twice the size shown - click to expand.
Mass Air Flow meter (MAF) : I've completely changed tack since starting this project, I was going to to the Speed Density route but now I've discovered eBay I've been able to buy pretty much all the electronics etc off of a 5.0 mustang that being an '89-'93 model, used Mass Air. This is the system that automatically adjusts regardless of what changes you make to your engine. Great idea. The only snag is when you change injector sizes. This can be fixed by buying a vortech or similar Mass Air Flow sensor body. These do NOT come with the hot wire / sensor, you will need to retain this off your factory MAF sensor. What is great though is that you can buy them callibrated for various injector sizes. They achieve this by having different 'sampling tubes'. This is the smaller tube into which the hot wire pokes. Having bought one of these sensors, you need only buy different sampling tubes to accommodate changes in injector size. Brilliant. However, I've heard that this isn't the best solution to changing injector size, I'm not sure why but ideally you would reprogram your ECU to tell it. In the case of the EEC-IV this can be done a number of ways (see below).
Sequential or Batchfire? : When GM were selling batchfire cars, where the injectors were fired together on one bank, then together on the other, wth each fired once per rev, they claimed it was the best thing since the diesel vibrator. But now that they've gone the way of Ford and adopted sequential, where fuel is injected into each cylinder as air is inducted into it, suddenly that's the way to go!!! Well common sense says it certainly is, but only up to a point. Above 3,500rpm apparently all sequential systems behave like batchfire anyway, because the injectors are open longer than the intake valve is. However we do most of our driving below 3,500rpm and it seems that sequential fuel injection offers far better driveability with superior economy. Although anyone going down this road is going to spend a year's fuel bill on the conversion so it's probably not about saving money!
Manifold and Throttle body : A single plane manifold is supposed to be ideal for converting to dry flow port injection (see pictures of my efi manifold conversion under construction) BUT I have been told by a couple of people who have actually done it and attempted to tune on a dyno that the single plane such as my Weiand Xcelerator suffer from short inside runners, resulting in uneven mixture. I'm not sure why this should be such an issue on a port injection system but perhaps variations in velocity affect atomisation? I would guess that most people do NOT bother to aim the injector correctly at the centre of the intake valve as I've done, allowing for the 30 degree spray, so maybe that's their problem. They rely heavily on airflow turning the atomised fuel whereas I just shoot it into the cylinder. I hope so, I can't think of any other reason for mixture variations. This page from Dave Williams' site (link fixed Dec 2003) has excellent photos of a manifold he converted which shows once again that most people just put the injectors in aimed straight down. This may work, but I can't see it being the best way so in light of the warnings I've received I'd strongly urge you all to try and line the injectors up perfectly.
If you can fit a throttle position sensor to it, a gutted 4 barrel carb should make an adequate throttle body although part of the advantage of converting to EFI is that you can run over 1000 cfm of induction without the usual problems associated with such a low air velocity at low revs. Most people overcharge like crazy for throttle bodies, which is tragic because there is nothing to the damned things, they're just a bloody air valve for god's sake. I'll find some links and publish them soon. The first will be eBay motors, a brilliant resource.
Distributor : A 351W EFI DISTRIBUTOR WILL FIT A 351C-351M-400-429-460 WITH A SIMPLE GEAR CHANGE. The 5.0 distributor is about 1.5mm smaller in the housing diameter and uses a smaller driveshaft pencil. There are two types of efi 351W distributor. In '94 and '95 they have an external TFI module, whereas from '89-'93 they were all attached directly to the distributor. The best explanation is from someone who has done it, go to http://www.detomaso.nu/~thomast/efi/ for pics of his distributor conversion, he ended up using a 460 body but it was one of the external TFI ones so he had to cut it to fit the earlier distributor-mounted TFI. My recommendation is a brand new MSD pro-billet for 351W EFI, see http://www.msdignition.com/dist_16.htm for details and a picture, and http://store.summitracing.com/partdetail.asp?part=MSD%2D8453 to buy it at US$225 which is a brilliant price, Summit are great. One other side-effect of using a 351W distributor is that they are taller than 351C-460 ones, so if you have a 351M-400 with intake spacer plates, and the intake has been raised as a result, this will save a lot of intake manifold grinding for distributor clearance. Warning - firing order! 351W and 5.0/302 HO engines have the same 1-3-7-2-6-5-4-8 firing order as a 351C-351M-400. All others are 1-5-4-2-6-3-7-8 as per 429-460.
ECU (Electronic Control Module) : My intention WAS to purchase a New Zealand made Link Electro Systems unit for about NZ$1,800 including tax (US$1200) last time I priced it. The newly released LinkPlus unit is a full sequential port injection controller that can drive up to 8 coils and has an enormous range of features, even built-in datalogging, enough to please anyone and the price is very reasonable. You can contact them directly at 243D Annex Rd., Christchurch, N.Z. Fax. +64 3 3436195 Phone +64 3 3488854.
Wiring :Because I'm going with an EEC-IV A9L computer, I bought a factory main wiring harness which I now realise didn't include the injector harness which I got separately off eBay, they're not too common but if you're lucky you will find one with fuel rails and pressure reg etc complete, these do come up every couple of weeks so keep looking. It is also missing the oxygen sensor and oil level subharness which someone is tracking down for me. Don't be shy about contacting guys on eBay selling similar items and asking if they have these parts because often they consider them too trivial to bother auctioning and will sell directly. Note that Ford Motorsport makes these harnesses. M-12071-C302 for the main harness, M-12071-E302 for the injector and oxy sensor harnesses. A surprising number of the C302 harnesses come up on eBay in new or as new condition. You can find them for sale (new) for US$150 or so, so be careful if buying off eBay. Warning - firing order! When shopping make sure the injector harness you buy matches the firing order of your camshaft and distributor!!! Part M-12071-E302 is for 5.0/302HO and