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-   -   Rotec Engineering TBI ? (https://vansairforce.net/community/showthread.php?t=56864)

Dmadd 04-17-2010 05:31 PM

I'll see what I can come up with as far as pictures.
When I measured it, I figured I would only need a one half inch spacer between the oil pan and the rotec, and everything would hook right up...
Thats the guess anyway... <BG>

DM

Quote:

Originally Posted by ratc (Post 424739)
Dennis, thanks for the input, it does sound promising!
You have answered one of the questions I've posted to Rotec regarding the use of the Vans FAB. No rush, but if there is any chance of a photo of the FAB modification/installation it would be a useful reference.
More importantly having seen one do you think there will be any major issues fitting it in/under the -4 standard 0-320 cowls?


Alan Carroll 04-17-2010 06:02 PM

Quote:

Originally Posted by SvingenB (Post 424780)
Same principle, but different design (like a V6 vs a straight 6). Rotec TBI is a sliding carb with a totally separate fuel pressure regulator that when used together makes up a complete single point fuel injection or TBI. It is a simpler design than the Ellison.

Besides, at less than half the price, and can run on mogas and manufactured by an active team using modern manufacturing methods (unlike the stale Ellison), there really is no comparison.

I'd be curious to know how this is a simpler design - the Ellison is already very simple. The basic principle looks to be identical in both, down to the pattern of holes in metering tube. The Ellison is one piece, which seems simpler than having to mount the diaphram assembly separately. However, the Rotec clearly wins on price (perhaps reflecting lower development costs) and on being able to handle mogas.

Something that hasn't been mentioned yet is that the Ellison is known for being sensitive to inlet geometry. Presumably the Rotec will have similar issues, since it apparently works the same way?

rocketbob 04-17-2010 07:07 PM

Quote:

Originally Posted by petehowell (Post 424626)
I have been flying too much to take the time to install it. Probably next annual.

RocketBob has one for his -6 and is further along on the install. Maybe he will chime in.

Got the cable brackets and spacer made, but have hesitated to put it on since I could not get adequate test time this winter before making a few long trips in the RV. I just got back from SNF so I've got no more excuses...:) Its hard sometimes to start modifying a perfectly good flying RV that runs like a watch. The other side of it is I want to make a few more 'before' test flights to validate the data I've already captured in order to properly validate my testing with the Rotec. Stay tuned.

petehowell 04-17-2010 07:09 PM

Install Pics
 
Install Pics can be found here....

Clouddancer 04-19-2010 01:28 AM

planning to use one in my RV-4
 
I'm planning to use the Rotec TBI on a O-360 in an RV-4. Will order engine and TBI later this year. I've been in short contact with Paul Chernikeeff from Rotec. He told me that they primarely developped the TBI on their on, because they needed them for their radial engines and that Ellison had to struggle for supply and was rather expensive.
For instance it seems that it will fullfill my needs: aerobatic, mogas, simple ...altough I've never seen one installed on an O-360.

carguy614 04-19-2010 06:16 AM

Rotec "injector"
 
Quote:

Originally Posted by Alan Carroll (Post 424808)
I'd be curious to know how this is a simpler design - the Ellison is already very simple. The basic principle looks to be identical in both, down to the pattern of holes in metering tube. The Ellison is one piece, which seems simpler than having to mount the diaphram assembly separately. However, the Rotec clearly wins on price (perhaps reflecting lower development costs) and on being able to handle mogas.

Something that hasn't been mentioned yet is that the Ellison is known for being sensitive to inlet geometry. Presumably the Rotec will have similar issues, since it apparently works the same way?

Looks to me to be the same technology that Ellison uses. Pressure diaphragm housing is integral to the casting on the Ellison, and separate on the Rotec. I hesitate to refer to it as "fuel injection" Rotating the metering tube into the venturi airstream meters the fuel. It's a slide carb. Looks like it could be a winner though, and I would love to see someone try to install one on a forward facing sump.
Regards,
Chris

Alan Carroll 04-19-2010 08:28 AM

Quote:

Originally Posted by Clouddancer (Post 425163)
IHe told me that they primarely developped the TBI on their on, because they needed them for their radial engines and that Ellison had to struggle for supply and was rather expensive.

Looking closer, the main functional difference seems to be that the the Rotec uses the pressure drop at spray bar to meter fuel:

http://www.rotecradialengines.com/TB...owTBIworks.pdf

In contrast the Ellison uses a separate pressure monitoring tube in the inlet throat. Not sure what difference this makes in how much fuel is metered. The geometry of the inlet, spray bar, and slide appear to be identical.

SvingenB 04-19-2010 08:41 AM

Quote:

Originally Posted by carguy614 (Post 425175)
Looks to me to be the same technology that Ellison uses. Pressure diaphragm housing is integral to the casting on the Ellison, and separate on the Rotec. I hesitate to refer to it as "fuel injection" Rotating the metering tube into the venturi airstream meters the fuel. It's a slide carb. Looks like it could be a winner though, and I would love to see someone try to install one on a forward facing sump.
Regards,
Chris

I have to agree, they are very similar. It is not a slide carb. The pressure regulator, or rather the modulated constant flowrate device makes all the difference. The same principle is used in ordinary fuel injections, but the mixture is very different. These TBIs use the metering bar to adjust the mixture as well as the main fuel flow by connecting it with the constant flowrate device, very elegant.

SvingenB 04-19-2010 12:03 PM

Quote:

Originally Posted by Alan Carroll (Post 425208)
Looking closer, the main functional difference seems to be that the the Rotec uses the pressure drop at spray bar to meter fuel:

http://www.rotecradialengines.com/TB...owTBIworks.pdf

In contrast the Ellison uses a separate pressure monitoring tube in the inlet throat. Not sure what difference this makes in how much fuel is metered. The geometry of the inlet, spray bar, and slide appear to be identical.

It is just different ways of obtaining the differential pressure between "static" and total. It is not really static since the main point is to vary this by adjusting mixture. The Ellison patent can be found here:
http://www.freepatentsonline.com/4524034.pdf

Look at fig. 14 and the following for different layouts.

The Rotec TBI sort of assumes that the total pressure is whatever pressure is inside the cowl (like fig 14 in Ellison patent). This is probably good enough in most cases, but I wonder what happens when flying without a cowl ?

Alan Carroll 04-19-2010 07:07 PM

Quote:

Originally Posted by SvingenB (Post 425276)
It is just different ways of obtaining the differential pressure between "static" and total. It is not really static since the main point is to vary this by adjusting mixture. The Ellison patent can be found here:
http://www.freepatentsonline.com/4524034.pdf

Look at fig. 14 and the following for different layouts.

The Rotec TBI sort of assumes that the total pressure is whatever pressure is inside the cowl (like fig 14 in Ellison patent). This is probably good enough in most cases, but I wonder what happens when flying without a cowl ?

Thanks, Figure 14 does help a lot. The Rotec design does appear to be slightly simpler than the Ellison in that it doesn't use a separate pressure sensing tube in the inlet throat (not sure if this is better or not). It also seems clear that both variants were fully described in the Ellison patent (now expired).

As noted by Rotec, the basic principle is a lot like a diaphram-type diving regulator? (except for mixture adjustment).


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