G40 ECU controlling fuelling only

[prankstar2003]

Is it possible to have the ECU control fuelling only with the ignition controlled by stand alone?

[Alexiskayak_7]

What's the reason of doing that?

Just fit a performance chip and it will fix all your needs

[prankstar2003]

I was hoping to create a hybrid mechanical headed engine, meaning the G40 distributor won't work as the fitment is different. Unless there is a suitable replacement that can be used with ECU controlled ignition. Original plan was to use a blow through R5 carb annd vacuum retard dizzy pot, but it seems like a massive compromise when compared to EFI and ignition.

[Alexiskayak_7]

I was hoping to create a hybrid mechanical headed engine, meaning the G40 distributor won't work as the fitment is different. Unless there is a suitable replacement that can be used with ECU controlled ignition. Original plan was to use a blow through R5 carb annd vacuum retard dizzy pot, but it seems like a massive compromise when compared to EFI and ignition.

Magajolt will do the job

[G40supercharged]

The Hall sensor in the distributor times firing of both the ignition coil and fuel injectors so the fuelling wouldn't work at all without the dizzy. You should also consider that the ignition timing on the G40 is automatically retarded if the ECU detects pre-ignition via the knock sensor. An alternative system would ideally need a similar function to give maximum power without the risk of melting anything. Stand alone ECU will still need something similar to the Hall sensor in whatever dizzy you fit. 

[Alexiskayak_7]

You can also use a standalone ecu (if you what to control fuel and ignition), stick a crankshaft position sensor and a crank trigger wheel, so you have RPM pulse and get rid of the distributor.

Or if you want to keep the costs down stick a megajolt ecu to control ignition only and use a carb.

I still haven't understand what you are planning to do...

[prankstar2003]

I had a feeling the hall sensor in the dizzy was going to be the problem.

Alexis, the idea is to use a mechanical head (from an early polo) mated to an ABD bottom end. The fitment of the dizzy is different on the earlier heads so its not possible to use a G40 distributor. The current plan is to use an R5 carb and keep the ignition as standard (with a retard pot substituting the vac advance pot on the dizzy). The thing is the compromise of using a carb and mechanically adjusted ignition. I'll either need to over fuel or keep the boost down to prevent damage and thus power will be down. It's as much an exercise in building a hybrid and aesthetics (the older mech heads look better imo) as it is going for big numbers. I'm unlikely to get a diff so the gearbox is going to limit usable power anyway. However, I would like it to be reliable and if making huge compromises I may as well fit an AFH/AYC and get as much power without the difficulty.

[Alexiskayak_7]

I had a feeling the hall sensor in the dizzy was going to be the problem.

Alexis, the idea is to use a mechanical head (from an early polo) mated to an ABD bottom end. The fitment of the dizzy is different on the earlier heads so its not possible to use a G40 distributor. The current plan is to use an R5 carb and keep the ignition as standard (with a retard pot substituting the vac advance pot on the dizzy). The thing is the compromise of using a carb and mechanically adjusted ignition. I'll either need to over fuel or keep the boost down to prevent damage and thus power will be down. It's as much an exercise in building a hybrid and aesthetics (the older mech heads look better imo) as it is going for big numbers. I'm unlikely to get a diff so the gearbox is going to limit usable power anyway. However, I would like it to be reliable and if making huge compromises I may as well fit an AFH/AYC and get as much power without the difficulty.

Mechanical head, you mean the old mk1 heads with rocker arms and adjusters?

[prankstar2003]

Yeah that's right.

I've since contacted Aldon Automotive and they do an ignition system that works using the original hall sender but is mappable. Probably not as advanced as other systems, but it does do away with the advance/retard pot on the dizzy, which to me has been a concern. If it doesn't work properly and the ignition isn't retarded, then there's potential for damage. I may just have to go with the R5 carb and accept its not perfect

[Alexiskayak_7]

Yeah that's right.

I've since contacted Aldon Automotive and they do an ignition system that works using the original hall sender but is mappable. Probably not as advanced as other systems, but it does do away with the advance/retard pot on the dizzy, which to me has been a concern. If it doesn't work properly and the ignition isn't retarded, then there's potential for damage. I may just have to go with the R5 carb and accept its not perfect

Prankstar, tell me a reason thing of doing all that...

Whats in your mind for your project? Power?

[prankstar2003]

I understand that a solid lifter mechanical head is able to rev higher without suffering valve bounce (due to the lack of fluid in the lifters). I'm not sure any engine I make will ever rev that high but it's a consideration. Also, I have an early saloon that had the old type engine in and I like the look of them so its for aesthetics too. Finally, I have accumulated all the parts (except pipe work) for relatively little money (around £500) which makes this a cheap project. In the end though it's just an exercise in building a turbo charged engine. I know there are 'better' ways of doing this but power is not the major concern. There is only so much usable power you can have in a polo on the road and the chassis. The transmission will be the weak point as I don't think I'll bother with an LSD so I'm aiming for around 150 bhp. Possible I think with the set up

[JoeH]

The transmission will be the weak point as I don't think I'll bother with an LSD so I'm aiming for around 150 bhp. Possible I think with the set up

Is a load of rubbish, even a stock G40 needs a quaife because it wheel spins in gear 1, and you easily lose front end traction on roundabouts. Any G40 needs as much handling help as possible! You clearly have never driven a G40 properly if you think you don't need a lsd or to improve the handling, they desperately need it, whether: subframes, bushes, quaife etc.
Rant over.

[prankstar2003]

Not once did I say I didn't need an LSD, just that I wasn't going to bother with one. I have never driven a G40 at all, but even a lowly 1.3 handles like a dog so I'm more than aware of the frailties of early polo handling

[JoeH]

apologies I was going over the usual mk3 polo handling woes rant.

[prankstar2003]

I would like an LSD but with so much other stuff requiring attention, it's a lot of money on something I can't see! Maybe in the future