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

[Javal]

Sorry River, could you please explain how losing 500RPM due to excessive flywheel weight is still classed as revving properly?? Allowing an engine to rev an extra 500rpm without any further changes is what I would class as allowing an engine to 'rev properly'. Perhaps you need to revise your definitions??

Lets not get our knickers in a knot. River is right, but I understand your train of thought.

Flywheel weight will not dictate your rev ceiling, this is what the old man is trying to illustrate. However the larger mass attached to the back of the engine may dull its ability to swiftly hit said rev ceiling, or more to the point, make it more difficult to get there.

The difference in weight between the standard and a lightened flywheel is massive.

While you won't gain any more power, you will be playing physics to your advantage.

Educational post for those who'd like to know the theory behind it all:

A nice little analogy -

If one was to shoot a 10kg weight out of a cannon with 'x' force, it would travel 'y' distance
If one was to shoot a 5kg weight out of a cannon with equal foce, it would travel a greater distance greater than 'y', as due to its lesser mass, it takes less effort to put into motion.

The flipside of this is, the 10kg weight will carry more inertia and thus is better at maintaining its speed, as where the 5kg weight will retain less energy.

The automotive application is a heavier flywheel will result in greater smoothness when in an on-off throttle situation. In other words, better tractability, or, in the case of an 18R-G, tractorbility (HA, you see what I did there?!)

However in a fully awesome sick racing environment, response is more important than tractability, so we go for the lighter option, reach our rev ceiling earlier, lessen our parasitic loss by reducing energy stored in our powertrain and thus go around Eastern Creek 12 seconds faster.

[RAd28]

I'd just like to throw a few thoughts into the argument regarding flywheels. Dana and I have only seen the before and after of fitting a light flywheel to one engine, that was her first hybrid 2/3TG. That engine was for all intents and purposes standard save for the 3T bottom end. We removed the stock flywheel and installed a seriously light flywheel (around 4-5kg) and match a nice light clutch to suit. We expected that the engine would begin to idle rough, become harder to drive particularly hill starts, getting off the line etc.

What we found blew me away. Yes the engine was noticably different, but in all the best ways. It idled smoother then any other carby 4cyl I've witnessed. It responded to throttle input VERY well (dare I say motorbike like), and it improved drivability massively. Starting and turning the engine off became faster, more definate (less hesitation). Getting off the line was not hampered in the slightest way at all nor were hill starts, and shifting while driving became so much easier, smoother and faster because the revs dropped quicker to match upshifts, and it was more responsive to throttle blips on down shifts.

That is without taking in to account ANY kind of performance gain what so ever. I'll leave that debate up to the other folks.

In my opinion, is there any benefit to putting a light flywheel on a unmodified engine??? Definately, no questions.

The only reason you might hesitate in getting a light flywheel is the cost, but I'd happily say that no other single engine modification will become as instantly noticable in all aspects of your driving experience.

I ask why haven't you already got one?

[egamirrorim]

I've been reading back through the thread and am curious about stroking/boring the 18RG with the 22R crank out to 2.4L.
What kind of power increase could you expect from increasing displacement 20%? 20% more power?

Similar question regarding the 44mm mikunis - Will your power increase percentage be the same as your fuel consumption increase percentage?

[o_man_ra23]

There's a can of worms egamirrorim...

Second item first. No, your power increase is unlikely to be the same as your fuel consumption increase percentage wise. Depending on the motor, the condition of the old carbs and the condition of the new carbs, you may have a dramatically improved fuel consumption, or it may be dramatically worse. Also you may find zero power increase from the bigger carbs, or you may get a huge improvement. There are way too many variables. Suffice to say, unless you have bombed the crap out of your engine, 44mm carbs are likely a waste of time and money.

For the 20% increase in capacity... what else are you going to do to the engine?? Will you upgrade the cams to suit the new capacity, and change to bore/stroke?? The engine is likely to want to work at a lower RPM than previously because of the increased rotating mass and increased stroke. Of course if you get lightweight pistons that give much higher compression, and match the cams to suit, then you could have far more than 20% increase in power. Once again, the condition of the engine prior to modification will play a big part in the before and after equation.

So without being too vague, you may completely exceed your expectations with your desired modifications, or you could wind up worse than when you started... Best thing to do is work out what you want from the engine, and go from there.

[egamirrorim]

I thought the answer might be something like that!
The reason I ask is that probably a while after I drop the 18RG in I'll look into rebuilding it. I bought the motor in "OK, running condition", but I'll believe that when I see it, regardless it was advertised as stock anwyay.
If/when I do rebuild it I'll be going all out and pimping as much of it (cams/porting/valves/pistons/con rods/etc.) as I can because I dont like to do things half assed.
Bottom line is I guess I'm just interested in seeing if it's gonna be worth my while, power-wise, spending (from what prices I've read in this thread and seen on the net) a few thousand dollars rebuilding/working an 18RG or should I just save that cash for a late model turbo engine upgrade when I'm off my P's...
What ballpark power estimates can I expect from a worked 18RG in N/A carb-fed format?

[o_man_ra23]

You could expect eleventy billion HP as a ballpark, but that wouldn't be a reasonable expectation...

If you have a look in Lambolica's thread, I think he did a dyno of his angry 18R-G. You can work them more than that, but it should give a ballpark. It was significantly less than the 200+ RWHP that River got from his Turbo 18R-G with a small GT25 turbo. A lot more can be got from a turbo 18R-G. I would say drive it as is until you are off your P's and build a turbo RG.

[GT1978]

Just going to throw this out there. Did anyone on here buy that set of carbs on the manifold on eghey recently? If so I would be interested in the air box backing plate that was bolted to them.

Glen

[TRD184]

hey guys, wiring a new tscho up at the moment, wondering, wheres the signal wire on an 18RG RA23? i was going to connect the signal wire on the new tach to the negative on my coil, is this right? sorry if its a noob question, i did some googling and got some yes's and no's

[o_man_ra23]

Yup, negative of the coil should be the go. It'll be a solid black wire from factory.

[TRD184]

You must spread some Reputation around before giving it to o_man_ra23 again.

thanks mate

[lilcrash]

Can some one please help me, I'm looking for a link to an 18rg manual particularly the setup of the timing gears. All the links I have found keep saying document missing or error

[damian]

quick search oif this thread gets this
http://www.toymods.org.au/forums/sho...ok#post1191760

with this link that still works

http://members.iinet.com.au/~stepho/manuals/18R/

thanks to MnToyGuy

[lilcrash]

Why doesn't my search work ?? Thank you very much for the link. Sorry for being a newb

[o_man_ra23]

Why doesn't my search work ??

Because you have teh AIDS

[lilcrash]

its because i have an iphone that has aids