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13brv3 wrote: I'd really like to hear more about the Rotec TBI experiments. I've been considering a homebrew EFI, or a single carb setup since I really hate the dual carbs.

Thanks for the reply Rusty,

With the Rotec TBI, I could not get the engine to run faster than 4600rpm, that was after trying a larger air box, then removing the said airbox which made no difference, I also overhauled it to make sure everything was clean inside and also put a new diaphram in but all that did was increase the power by 1000rpm ( I believe from the larger airbox). Before I did any of this it would only pull 3600rpm. The mixture seems very unstable at any rpm although, even when it seems to be running rich it is only drawing 15LPH which is way lower than what you would expect at full power but given it will only run up to half throttle before running extremely rough it probably makes sense that 15lph would be too rich. The engine would run at any mixture setting but leave it in one place for long and it would start changine rpm again. I finally got sick of dealing with it and degrudgingly decided to go back to what is proven to work and I know, all the maintenance that goes with the dual carb system probably will suck so much that I will wish at some point in the future that I perservered with the TBI, but for now, I am so close to first flight that I just want it to be reliable.

Has anybody else tried to run a single carb or TBI on a rotax? I copied a design that was known to work yet I didn't persist long enough to suceed with it.

I'm assuming this was with a prop that was known to have full static RPM with the stock carbs? Was is a single TBI? Pictures would be excellent.

You mentioned that you copied a known working configuration. Was it the recent webinar that mentioned an aerobatic team that used that configuration? Was that the config that you copied? I had never heard of that before.

Dual carbs is always claimed to be higher performance, but I can't believe that's universally true. With a proper size single carb/TB, and a well designed intake, I have to believe the performance would be equal. I do hope to test that theory some day. I've joked that the only thing worse than a carb is two carbs.

Rusty

13brv3 wrote:I'm assuming this was with a prop that was known to have full static RPM with the stock carbs? Was is a single TBI? Pictures would be excellent.

You mentioned that you copied a known working configuration. Was it the recent webinar that mentioned an aerobatic team that used that configuration? Was that the config that you copied? I had never heard of that before.

Dual carbs is always claimed to be higher performance, but I can't believe that's universally true. With a proper size single carb/TB, and a well designed intake, I have to believe the performance would be equal. I do hope to test that theory some day. I've joked that the only thing worse than a carb is two carbs.

Rusty

If you can open the attachment, this is what I copied, it was sent to me for guidance by Rotec.

I have the early sensenich prop that Sonex sells, it was never tested with the original carbs but other reports found it should be close to 5200 static. Single TBI 40 used

The attachment didn't work so here are a couple of screen shots of it.

Murray Parr wrote:

TBI induction copy.pdf

If you can open the attachment, this is what I copied, it was sent to me for guidance by Rotec.

I have the early sensenich prop that Sonex sells, it was never tested with the original carbs but other reports found it should be close to 5200 static. Single TBI 40 used

Thanks. The attachment worked fine for me. Have you been told by users that this works as shown? I'd certainly be suspicious just from the hard 90 degree turn the air has to make out of the TBI, and the back and forth motion that must be going on inside that larger piece of tubing. I'd have to think about that some more.

As for the prop, I agree that it should be a known quantity. I've been tempted to try one of the Sensenich props, but I'm not sure it would be any improvement over the 3 blade Warp Drive.

Rusty (trying to resist)

Your searching skills must be better than mine, because I can't find any info about TBI usage online. The Rotec site did mention people who had made intakes that worked, but there was no hyperlink where you were supposed to click to see it. Searching for that person's name didn't turn up anything either. I found a Rans forum thread where someone was going to make an intake for the TBI, but it wouldn't let me view it without being a member of the forum. I'm clearly spending way too much time thinking about this...

Hi .Are you making any progress with your TBI .I ask because I have have been involved in the installation and setup of Rotec TBI before
and a 40mm should pull way better than the results you are seeing.
Regards Bish

bishoff7 wrote:Hi .Are you making any progress with your TBI .I ask because I have have been involved in the installation and setup of Rotec TBI before
and a 40mm should pull way better than the results you are seeing.
Regards Bish

I wasn't able to get it to run properly so I degrudgingly went back to the Rotax dual carb setup. If I was to speculate what the problem could have been, I would say the fuel metering spray bar needed more holes in it sooner, the engine would start running too lean at just over half throttle 10 mm before the slide uncovers the wider set of metering holes, it was becoming unmanageable to go back and forth to the airport trying different things. If I lived closer to the plane I might have persisted with it. I'm pretty dissappointed with it all...

I ordered one of the TBI-40mm Rotec units to try. After a week or so, I decided to just go straight to EFI, so I tried to cancel the order, but I was too late. I'll likely still give it a try with an engine on a test stand, and I might even use it as the TB for EFI where the Rotec could act as a backup if the EFI failed.

Rusty (I hate carbs)

Had the same experience with them on a revmaster and also on a jab 3.3 .Really fickle , the only answer for me was to mod the spraybar and use a really really fine filter as if you get garbage in the spraybar it will send you lean inflight .Not a good outcome. On the revmaster the trick was to adjust the spraybar rich an lean out once you were in the air