Work in progress

[Jekyll and Hyde]

Thought I'd stick up a shot of how my EFI conversion is going, for those who might be interested.

[Anth73]

So what are you trying to do and how is it going? What will the motor go into? How much power and torque are you aiming for?

[Jekyll and Hyde]

I'm fitting GSX-R 750 motorbike throttle bodies onto my 2 litre GTV ('81 model), to be run by a Megasquirt computer.  Got sick of the clouds of black smoke coming out the back from the carbies, and I'm not fond enough of them to rebuild them.  Do like the sound though, part of the reason I'm going with individual throttles, along with the fact I reckon going to a single would be a step backwards.  Also the cost is pretty similar either way.

No idea what power/torque will be achieved at this stage, I'm mildly musing that the EFI might be worth 10kw over standard, but the EFI conversion is more targeted at better driveability (cold starts etc), and the power gains will be kind of incidental.  That said, the car when dynoed with the carbs put out 55kw at the rear wheels, and was filling the dyno room with black smoke, so the gains over what it WAS should be quite impressive in my case.

Future plans call for a turbo setup which should easily top 150kw at the flywheel, and/or perhaps some bigger cams, but thats later.

First, I want to get it going again and onto the track.  Currently the project is past the halfway point, most of the hard stuff has been done, and its down to fiddly bits and redesign - and a lot of wiring, which I just added to by fitting a later dash and loom into it.  Now I have 10 foot of wiring loom spilling out of the engine bay, and only half of it I know where it goes.  Fortunately, its mostly the important stuff I know!

[Jekyll and Hyde]

Thought I should update this....  Engine bay is pretty much finished, allthough I want to tidy a few things up a little (mostly hoses).  The car drives now, and gets you somewhere, although you come back on a tow truck.  Went for the first drive this afternoon, and was greeted by awesome sound at low revs, extreme leanness at higher revs, and a random death without the chance of a restart (until an hour later when I managed to restart it, drive around the corner and then died again).  Guess what fault I'll be chasing for the rest of the long weekend.

Also wacked up an outside shot of the car (in the rain after unloading from the tow truck!) for kicks, hopefully some of you will be seeing it at sprint days soon (not PI though, not entered and probably won't be happy with the tune by then anyway.)

[jimnielsen]

Great work!  Its cool to see different fuel injection systems on the traditional Alfa 2L engine.  I'll look forwards to seeing the car at a sprint soon!

attached is a pic of my cars fuel injection system as a comparison!

Cheers, Jim ~

[Jekyll and Hyde]

attached is a pic of my cars fuel injection system as a comparison!

That's a very nice setup!  Whats in it - looks like EFI hardware or Jenvey throttle bodies?  And what engine management is firing it all?  I like the upstream injectors too.

Just out of curiosity, what size are those two sets of injectors, and at about what RPM do you have the second set kicking in?  I have two sets of injectors also, currently running on the smaller injectors in the bike throttle bodies, and have some slightly bigger ones set into bosses on the undersize of the intake manifold, so would be interested just for comparision sakes.

[jimnielsen]

The ECU is an Autronic SM4. The front injectors start to come on at 3750 RPM. I don't know the actual size of the injectors - the system was implemented by Bennica's.

Cheers, Jim ~

[Domenic]

Hi

Just wondering what size those throttle bodies are from the GSX-R that you have used on your efi conversion?

What size in diameter are they?

Cheers.

PS,  cool looking set up.  would like to see it at the track or at the spettacolo next weekend.

[Evan Bottcher]

Last time I looked into the megasquirt system it was not multipoint - meaning with individual throttle bodies the ecu could not fire them independantly, but would fire all four injectors on each cycle.  Is this true?  What effect does this have?

Great thread by the way 

Also - why two sets of injectors?  I've seen lots of race engines set up like Jim's with injectors suspended above the trumpets.  Guessing that would be inefficient for anything but a race motor which runs at high RPMs (and high air velocities).

[Jekyll and Hyde]

Just wondering what size those throttle bodies are from the GSX-R that you have used on your efi conversion?

What size in diameter are they?

They are 2000-2002 GSXR-750 throttle bodies, which are 50mm at the intake side and taper down to 42mm.  They are probably slightly too big for the 2 litre, but I selected them with an eye to future expansions.  If you wanted truly insane throttle response, you would probably look for GSXR bodies in the 38mm exit diameter.

Last time I looked into the megasquirt system it was not multipoint - meaning with individual throttle bodies the ecu could not fire them independantly, but would fire all four injectors on each cycle.  Is this true?  What effect does this have?

The gains from sequential injection are fairly minimal over a batch fire system.  Most earlier injection systems are batch fire with no issues, and quite probably a few of the current models still use batch fire.  The disadvantage is that you can't trim cylinder fuels individually to account for slight differences in cylinder efficiency.  If you are trying to squeeze the extra one or two percent out of a race car, then the time to setup a sequential injection system is probably worth it to you, but for most people batch fire will be just fine.  It doesn't really affect individual throttles any differently to any other setup, as far as I know.  Further to this, if you were running just the 4 injectors, you could wire two to each injector driver (or bank), and use alternating injections (ie. fire one bank then the other).  By pairing the injectors in respect to firing order (say 1+4 on one bank and 2+3 on the other), people have reported extremely good running.

Also - why two sets of injectors?  I've seen lots of race engines set up like Jim's with injectors suspended above the trumpets.  Guessing that would be inefficient for anything but a race motor which runs at high RPMs (and high air velocities).

The second set of injectors in that sort of situation is, as you guessed, for high rpm running.  Placing injectors that far up tends to not work very well at low RPMs, as the fuel drops out of suspension and puddles in the intake, but when pulling higher revs, the air velocity is much greater, and by having the injectors there the fuel atomises much better by the time it gets to the cylinder.  The other reason for two sets of injectors can be to have a bigger secondary set (turbo/rotary applications).  Bigger injectors are not as fine tuneable when you get to small open times, such as idle and low speed running.  By having a small primary set you can achieve a smoother idle, and then when into the power band or coming on boost the big boys can cut in to supply the fuel that the smaller ones are not capable of delivering.

My reason for having a second set of injectors is to allow for expansion, if I do decide to go turbo.  I have set the whole intake system up so that I won't have to redo any of it (hopefully) if I put a turbo on it.

As far as Spettacolo goes, at this stage I'm still fighting with the car to get it running properly under load, so doubt it will make it there in any form - it definitely won't be an exhibit should I make it there anyway...

[Jekyll and Hyde]

More update: This car is lethal in the wet.

Has 30mm wider rear rubber than before, and supposedly a stickier compound, with fat water grooves in it, and still lights them up unbelievably easy on the wet bitumen today, despite its fairly rough tune.

May have to do with the fact that the carbies were basically down to the point where power was produced from 3000 to 4500, and now it has serious low down grunt and throttle response (even with the crappy tune).

Anyway, the point is I now seem to have de-kinked it, its running like a champ (tonight at least), and tuning will begin in earnest the next few days.  Should see the grin on my face after tonights little blast in the wet, after 4 weeks of sorting gremlins out.  And the sound............

[Jekyll and Hyde]

Well, its been a long couple of weeks filled with much swearing and periods of depression, but finally I'm fairly hopeful that I've got it sorted.  Ended up going to individual pod filters due to my bad airbox design causing some issues, and had to stuff around with a couple of issues, but it now has run pretty damn well (up to 6500 rpm anyways  ).  And I thought it sounded good before?  Well, nothing can compare to it running on all 4 cylinders and breathing through pods - its an angry angry noise.

Still have some work to do - I want to finish panelbeating the V6 bonnet I have, and replace the teatray with some kind of subtle scoop arrangement, so that I can run a box around the pods and up to the bonnet for a nice big gulp of cold air, as the current temperatures around the filters are in the 37-40 degree range (ouch).  But for the moment, it is actually driveable, and I'm glad.

[jimnielsen]

umm. So will we be seeing this mighty beast at Phillip Island at the club sprint on Sunday?

JimN~

[Jekyll and Hyde]

No, I ran it to work and halfway back on Monday before the fuel pump deathed!  So I'm finding myself a new one of those, and I wouldn't trust the current discs and pads in the front to do a single lap especially of Philip Island, so I'm giving that one a miss.  Should be all go for the next track event in some form however - I believe thats probably the driver training day in March?

Oh yeah - and compared to your race car, mighty beast is probably a very inaccurate description - loud, slightly more powerful than standard beast is probably better