For the love of a tractor engine: The life and times of the 18R-G

[o_man_ra23]

Fuel atomises better at 40PSI than at -5PSI. The fact you are blowing a spray of fuel into the ports rather than relying on suction to vapourise a stream of fuel means you get a better more even burn. Also you are putting fuel in at a better time, usually just before the valve opens, which again will give better flow than always running fuel, even when the valves are closing/closed.

EFI is fundamentally a better system due to the way it puts the fuel in. And then it can be precisely controlled by a computer with closed loop feedback, and temperature compensations.

Cheers, Owen

[Ren_RG28]

Ok ok you've convinced me! Now... where to find myself an EFI manifold...

[Omegaman]

Yeh, what he said.
Thats why,
I like EFI

[RAd28]

owen... correct me if i'm wrong, but at -5PSI would the fuel be atomised already?? since it's in vacuum? agree with every thing else though...

[timbosaurus]

Not denying EFI benifits at all, but at 95% duty cycle, injector timing aint gunna be much better than a carby.

Did any one on hear ever hear Damien Hortens* red 18RG "Sleeka" in it's initial tune? From what I read in a magazine article, it had some mega potent avgas* or methonal* sucking monster that ran something in the vicinity of 14:1 comp*!!! But then I think Damien bought*, or sold*, it and the motor was detuned to a more streetable figure. Now that would have been a sound for sore ears!

*my memory is pretty sketchy at the best of times, so if someone recalls better, please correct me!

Cheers,
Timbo

[airfireman1]

Just been sitting back soaking up this thread, and I just have to say that the perfect solution would therefor be fitting a crank angle sensor a better fuel injection computer and go for sequential injection so that the injectors fire just prior to the intake valve opening instead of batch firing. Am I on the right track?
Cheers

[SillyCarS]

i have an efi manifold and other goodies too!

PM me if intersted

[RAd28]

i want these on mine... but heaps of other things to do first up...

[Ren_RG28]

It's ok SillyCarS, I was just joking around. Thanks anyway.

[Gunna]

i want these on mine... but heaps of other things to do first up...

Yeah id love a set of them too one day...

[Norbie]

Not denying EFI benifits at all, but at 95% duty cycle, injector timing aint gunna be much better than a carby.

Correct, the benefits of EFI are minimal at WOT/high RPM. That's where sidedraughts really shine and they do a great job! What they're not so good at is the low RPM/part throttle scenarios (ie where the engine spends more than 95% of its time), and that's where the benefits of EFI come in.

Carbeurettors will always be a compromise between power, part-throttle response and fuel economy; EFI allows accurate fuelling under all conditions.

[timbosaurus]

It is often toted around that a nice set of webers will outperform EFI up high, but they are a compromise down low, so EFI will perform better overall. ie: carbies are better for max power, while EFI is less of a compromise.

I would suggest that this is not true however, as I can't see any shortcomings (assuming correctly sized injectors) of an EFI system, even at high RPM.

The only time I could see this argument being proven is if you compare maybe a perfectly tuned set of big webers on a short manifold on an 18RG with a stock EFI inlet manifold, which has long runners and a more complicated inlet path. But then it is not the carbies giving a higher power, it's the shorter and straighter inlet tract.

Does anyone have any real justification to the "webbers are actually better than EFI up high" argument?

Cheers,
Timbo

[RAd28]

interesting point there guys... say your application was circuit racing, where most of your time will be WOT or close to, then there would be little or no benefit to be gained by going to the trouble of setting up EFI (like that ITB setup shown above)?

[o_man_ra23]

ITB, rising rate fuel regulator, properly sized injectors (so they dont run anywhere near 90% duty), sequential injection etc, would all come under my heading of a decent setup. This is where EFI will kill carbies.

Another benefit of EFI is the use of knock control and closed loop feedback from the oxygen sensor, so you can always run peak torque, and dont have the fear of detonation which you get from carbies. I think the gains of carbs over efi have come from poor efi setups, such as the aforementioned stock 18RGEU setup.

Timbo, if you get 95% duty cycle ever in your EFI setup, you have a problem, or the injectors are too small. They should never run past about 70% (heat reasons)

Cheers, Owen

[timbosaurus]

So I guess from lack of responses no one remembers Damien Hortons red "Sleeka" RA28 engine, and who built it with what parts then?