fiery

My Feedback: (2)

Good to see the "bumpy" Irvine is doing well David.

[Love the "Saito" glass bowl fuel filter. They are a favourite of mine].

Hobbsy

My Feedback: (102)

Thanks Derek, sometimes the after run oil can fool us on the feel of the compression but in this case the compression is as good after the run as right after I put the aro in it. Did you happen to notice the rod bushing, it shows no wear at all. If my instincts serve me well, the bumpy intake port is to direct the intake blast away from the glow plug so as to not drown it like MDS engines tended to do. Could be wrong though.

downunder

That "bumpy" port has stirred a memory in me. I think it may be a true boost port if the cavity isn't connected directly to the crankcase but is closed off by the descending piston just before the transfer ports open so it traps the most highly compressed fresh charge inside the bump until the piston uncovers its port.

Hobbsy

My Feedback: (102)

Thanks Brian, tomorrow I'm going to pull the head and show you a tiny little port, you probably have already seen them. These tiny transfer ports are beside the larger front and rear transfer ports.

fiery

My Feedback: (2)

I pulled the head off my Irvine .40 Mk II ABC the other day.

I did that to freshen it up with a new piston and liner.

The head is a two peice affair, the finned head holding down a separate glow button.

I am curious. Is this standard with the Mk II .40, or was this a special .40 for pylon use?

I have heard of an Irvine SP .40 but have never seen one.

Hobbsy

My Feedback: (102)

Derek, I can't remember that any of my Irvines are set up like that, I'll check the bumpy.

Hobbsy

My Feedback: (102)

OK, here are some shots of the bumpy's ports and head. I think they are self explanatory.

fiery

My Feedback: (2)

Hi David

That "Bumpy" Irvine .40 looks good!

Regarding the Irvine I have with a two peice head, you may know of the engine I am referring to.

I will take the head off it tonight and post some shots of it on this thread.

It seems professionally made. I would say it is a factory job, but I would like to know more from someone with knowledge of these engines.

It's liner also has the small extra ports (2). I would wager the liner is identical with the one in your "bumpy".

If so, good news, as you can still buy ABC P&L sets for them.

downunder

It seems that both (Hobbsy and Derek) of your Irvines are ringed which probably explains the 2 small ports and with Derek's engine there's likely to be a divided boost port as well going by the picture of a Mk II ringed liner on that Ripmax site. There aren't any heads shown with a button though so I'm guessing someone made it which isn't really too difficult. The "bumpy" though would have to be what might be called a Mk I and I'm still not certain about the layout of the boost port although one photo seems to indicate the bump doesn't connect to the crankcase but is a small chamber that traps compressed mixture until the piston uncovers the port in the liner. With the backplate off it'd soon be obvious if it connects to the crankcase all the time or not.

Veeger needs to know

Hobbsy

My Feedback: (102)

OkeyDokey, tomorrow Veeger will pull the cylinder and the backplate and do sum vestigatin. How zat? Its bed time here in the Upper Half.

Hobbsy

My Feedback: (102)

As promised, the pictures show that part of the fuel mixture flows through the window in the piston up through the bump and over the piston top. In the shot of the bump port just opening the exhaust is about 3x as far open as the intake ports. One picture shows the crank position just as the intake ports open.

Recycled Flyer

Isn't a windowed piston simply a way to convince, by way of gas flow, oil and its cooling charge up under the piston crown?

Other wise the flow is just directed around the outsides and never through the center.

earlwb

Interesting thought.  Maybe that was the idea ages ago. But I can see it having a performance disadvantage as it restricts and obstructs the flow of the air fuel oil mixture through the piston and up the port like that to the combustion chamber.
Which is why everyone now uses the ports being exposed on the bottom of the cylinder sleeve.

Hobbsy

My Feedback: (102)

One possible advantage Ron Irvine saw was that by reducing the channel down to the bump reduced the crankcase volume, increasing the crankcase pressure at intake port opening time.

Kostas1

Very explanatory pictures Hobbsy!

Hobbsy

My Feedback: (102)

Thanks K-man, it not easy photographing that shiny stuff.

Recycled Flyer

Another advantage with a windowed piston is lightness, and to some extent it gives a 'piston ported' timing for that distinct transfer port only.

downunder

Thanks for the photos Hobbsy, all is explained now . It doesn't work the way I thought it might have where the highest crankcase compression gets trapped inside the bump and then released a little after the flow starts to drop through the main transfer ports giving a "boost" to the scavenging. I thought this might have been the engine I'd heard about using that system. Quite a few engines use a window in the side of the piston to help make the mixture usually trapped inside the piston flow through into the transfer/boost passage which helps cool the underside of the piston crown and aids lubrication of the wrist pin. All in all an excellent idea and I don't know why all engines aren't like that.

Your "bumpy" Irvine is a little different though because all flow to the boost port passes directly from the underside of the piston so should give even better cooling/lubrication. This is exactly the same type of porting used by the Dooling 29/61 except in their case all gas flow was through the piston windows (3 of them) into the transfer passage. The iconic bulge on the Dooling is its equivalent to the Irvine's "bump".

buzzard bait

I've got two Irvine 39s, UK made. I ran one this summer on a sport model and was really pleased with the power and the very low idle, but the transition from idle is not ideal. Transition is very reliable, but a little slow and always with a bit of hesitation. This is after quite a bit of time working over the HS and LS needles. I thought maybe I could just lean the LS needle a teensy bit more and fix it, but that caused the engine to quit when throttling up, so I'm pretty confident I don't have the LS needle rich. Ideas? Maybe try a hot plug? I don't know what plug Irvine provided with the engine. It has an idle bar, which I thought was odd.

Jim

fiery

My Feedback: (2)

This is my Irvine 40 ABC Mk II featuring a two peice head.

I am not sure if the two peice head is a factory item. I do know Irvine supplied sport 40 pylon engines. If anyone knows whether they were delivered with separate button chambers ex factory, please advise.

Texas Don

My Feedback: (5)

Was the pylon model a rear intake?

downunder

I'm just about certain that's a home made button, although quite nicely done, because every head button I've seen is only wide enough to clamp on the cylinder flange so doesn't have the screw holes. It's almost as though someone took a standard head and machined it down to a button then another standard head and machined out the plug hole area to fit around the top of the button. Looking through the Ripmax site at all the heads shows they're not a 2 piece, even the SP40 head which for some reason is quite a bit more expensive than the standard head.

Also from the Ripmax site,the SP40 (whatever it may be) uses the same side exhaust crankcase as the MkII but it's cylinder liner has some unusual porting compared to the normal. Actually it's quite interesting looking through the Ripmax site because it seems as though you could mix and match many different parts to make whatever type engine you wanted like ringed/ABC, rear/side exhaust, front/rear induction etc.

fiery

My Feedback: (2)

Hi Brian

I just replaced the P&L in the above engine with a new set, ordered from "RCmodelcentre" in the UK. They stock all the parts RipMax list for Irvine, and are very easy to deal with.

The "SP" spec items did catch my eye. I shied from buying them when I saw the uplift in price over the standard Mk II .40 ABC set.

It would be interesting to try the "SP" P&L and head set out though. I expect it would really perform on FAI fuel (like yourself, I don't use nitro except in Cox's).

The fit/compression from the new (new old stock?) Mk II .40 ABC P&L set I fitted is superb.

I intend retro-fitting an Irvine 25 glow JetStream carb for use when I have made up a diesel head for it as well.

One day I must run my Irvine 61 RLS ABC pattern engine. I recall you have one as well.

downunder

Yep, I've got one that's brand new although mine has a Dykes ring. What I found interesting in the Ripmax site is that there are two crankcases for the RE 40, one for ringed and one for ABC. My ABC 40RLS has Irvine 40R cast on both sides of the crankcase while the photo for the ringed crankcase is plain on the left hand side. Unless the liners have a different outside diameter I can't see the reason for it. They list all the parts for the 40RLS except the cylinder head which is red.

Below is my 40RLS which is a bit of a hen's teeth because they were only made for CL stunt. I believe this is the only one in Australia.

fiery

My Feedback: (2)

I just missed on an a rear drum induction Irvine 40 Speed (the mysterious "SP" methinks!) on the internet auction site.

There are also a few of the early "bumpy" Irvine 40's being listed.

It seems Irvine made a proliferation of 40's, one for nearly any application.

My Irvine 61 RLS originally had a dykes ring set up but it was replaced by the previous owner with an ABC P&L set.

I see you can still get a backplate with pump set up for them, if you are willing to pay the price!