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Rotec TBI issues

Flew three test flights yesterday, but could not fly high due to low ceilings. The Rotec TBI continues to impress me with low fuel flow numbers, perfect behavior with rapid throttle movements, easy starting, and general smoothness.

Prior to the upgrade it was easy to cause the CHT to go 425-450 by holding takeoff power for extended periods. Now it won't go past 390 and I ran full power for 30 minutes straight and level. Have also done several 100kt extended climbs and it stays cool, under 400.

At cruise, seeing 340-350 CHT.

The carb which was replaced was a MA4-5 3878 (not a 3878N). My RV-6 had a 4164 which had the main jet more appropriately sized for the RV and even that never ran as nice as this is now running.
 
Sure sounding good Bob. So are you going to start making adapters to bolt to the bottom of the Rotec so the rest of us can replace our carbs while leaving the air box in exactly the same place?
 
No I don't have time to get into manufacturing parts, although I'd be happy to send the Solidworks files to anyone interested.
 
speed runs

OAT on departure 78 deg F 850msl
110kt climb to 7500ft, wide open throttle 2700rpm
405 CHT 1450 EGT 195 oil temp

level off 2500rpm/23"

GPH/EGT/CHT/4way GPS speed
9.1 1375 350 165.5kts
8.1 1310 305 159.0kts
7.5 1325 295 148.6kts

Lean of peak operation seems to be no problem. Encountered some roughness playing around with the mixture, fuel flow was around 6.5 GPH.

I've noticed any time the throttle closes, fuel flow bumps up and more attention has to be dedicated to the mixture knob when making power changes.

Also unlike carbs and FI mixture position is not necessarily indicative of "true" mixture...tonight when I was up high with WOT for a the same fuel flow that I would see at a lower altitude the mixture was not nearly as far pulled back.
 
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Bob,

What is your CR in this engine? And what is your EGT's on takeoff (at what AMSL too)?

And did my posts on the last page help?
 
CR 8.5:1, 850msl, 1450 EGT.

The chart agrees in general with my LOP knowledge and what I'm seeing with the Rotec.

Pretty cool that this $750 fuel metering device does what systems > 3X the price do and simple enough that I can completely overhaul it myself with no special tools or equipment.

When I was setting the Rotec up I was able to get idle down to 150RPM. No I didn't leave it that way but it was interesting to entertain a small group of people for a few minutes with a Lycoming steam engine chugging away.

The altitude tests were done on a 50/50 mix of avgas and mogas. As soon as I empty the right tank I'm going to test running on 10% ethanol mogas.
 
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CR 8.5:1, 850msl, 1450 EGT.

Thanks Bob,

Now you need to work on fuel flow flow. It is no wonder your CHT's are so high. Unless your magneto timing is retarded several degrees, the 1450dF on takeoff is showing insufficient fuel flow.

Assuming you have 25DBTDC static timing, and WOT full rich, I would like to see that EGT value around 1270-1320.

That mixture is not rich enough, or someone stop your pistons and put in 7:1 or retarded your timing a heap :D

Cheers!
 
I have fooled around with the takeoff mixture a bit and found all it did was burn more gas with no tangible benefit to climb. I can reduce EGT quite easily with a slight closing of the throttle but otherwise everything is running very cool.
 
Timing is perfect, I check that as part of the condition inspection and am running EI on one side. The only possibility is a decrease in pressure inside the spray bar due to the top four row of holes on the WOT end being exposed in a "leaner" orientation since they don't line up with any other holes. I may silver braze the top row closed as an experiment at some point but right now its running great and I don't mind the elevated WOT EGT since oil temp and fuel flow are stable. A slight throttle reduction drops the EGT big time. I'm sure many on this forum would rejoice with a stable 405 CHT and 195 oil temp on a hard climb to 7500 burning mogas. Normally I never do that and always go 25/25 cruise climb as soon as obstacles are clear, so I have zero concerns about it.
 
That makes it even worse. An EI will reduce EGT, so it carries some advance even at WOT most likely, plus reduced fuel flow.

It is a bad idea to use the CHT as a direct proxy for cylinder pressure, you may have good cooling compared to someone else with poor cooling but they have much lower stress than you, but the same CHT.

I would not be happy.

Is it going to kill your engine any day soon, no. Is it a good result? sub-optimal at least.

Just trying to help you get it better having seen a lot of fully instrumented dyne data over the last few years. ;)
 
1450 EGT is no problem for a Lycoming...many turboed airplanes run much higher TIT (EGT) than normally aspirated engines do. Couple hundred degrees higher.

I believe that the superior atomization of this system is moving heat out and away from the combustion chamber and hence the EGTs are higher. Its a different animal.

Collect some dyno data on a Rotec install then talk to me. :)
 
1450 EGT is no problem for a Lycoming...many turboed airplanes run much higher TIT (EGT) than normally aspirated engines do. Couple hundred degrees higher.

I believe that the superior atomization of this system is moving heat out and away from the combustion chamber and hence the EGTs are higher. Its a different animal.

Collect some dyno data on a Rotec install then talk to me. :)

Bob, The EGT itself is not a problem?.TIT's run up to 1750 max continuous on some systems. But that is not the point.

You are not flowing enough fuel by my estimation, and so far you have not confirmed this by quoting your numbers. The higher CHT you are noting confirms this.

Collect some dyno data on a Rotec install then talk to me. :)

Gladly, lets start with a $20,000 deposit and your engine in a crate ready to ship. :cool: The laws of physics apply equally to all things Bob.

I believe that the superior atomization of this system is moving heat out and away from the combustion chamber and hence the EGTs are higher. Its a different animal.
Explain your belief please, as it seems at odds with the science. You are quite likely getting better atomisation compared to the old carby but the rest of the science of combustion and the rest of your engine remain a constant.

Just trying to help you out here. :)
 
Explain your belief please, as it seems at odds with the science. You are quite likely getting better atomisation compared to the old carby but the rest of the science of combustion and the rest of your engine remain a constant.

The combustion event is happening so slowly now with a lean but stable mixture therefore more spark advance is required to move the peak pressure point back closer to TDC. EGT is higher because the combustion event is continuing after the exhaust valve is opening. Adding more fuel will move the peak pressure point back and reduce EGT but as I stated previously with little benefit. More spark advance would be more advantageous in this situation.

Since the airplane has an older Electroair I can add a pot and a resistor to advance the timing for cruise conditions.
 
Enlarging Holes in ROTEC TBI unit

After a few more flights I made the following changes to my Long EZ induction set-up. Added a K&N Filter between the NACA inlet and the Carb air/heat box. That helped with over-leaning issue at lower RPM's. However, the last flight I took I noticed some surging of the engine. it almost sounded like when you're flying a twin and the props are not in sink. I determined that the TBI was running lean at full rich above 2800 RPM. So, I ordered the #80 drill bits and the hand drill. I will open up the holes in the TBI spray bar so I have some mixture to play with. As it stands right now I can not pull back the mixture at all. the engine is running on the lean edge at Wide open throttle. Now most of you would not agree but I am an engineer that design's engines for Chrysler, Detroit Diesel and PACCAR engine, So I will tell you that I run my Lycoming up to 3200 RPM's. So long as the valves, springs, retainers and guides are strong the engine will run like that just like any other engine does at 2600 RPM's. Lycoming's like running under load so-long as you can maintain cooling and lubrication. When I built my engine I balanced the rods, pistons, wrist pins and crank to under a gram. I know I will get a few squaks about the RPM but I would appreciate any negative comments come with Facts and not Hear-say.
 
On the four row of holes at the WOT end, enlarge only the holes parallel and below (to the rich side) of the double row of holes. I believe the other holes do nothing but drop the pressure inside the spray bar. And enlarge all the others. #80 won't help much, at least that's what I observed. But they helped.

I was enlarging by hand and it took forever so I got a chuck from McMaster to go in an air pencil tool. Then it was a breeze but took a steady hand.

Here's what I ordered from McMaster...

30585A96 3 Each Uncoated Hss Jobbers' Drill Bit, Wire Ga 78,7/8" Oal,0.2" Drill Depth,118 Deg Point
2 30585A95 3 Each Uncoated Hss Jobbers' Drill Bit, Wire Ga 77,7/8" Oal,0.2" Drill Depth,118 Deg Point
1 30585A98 3 Each Uncoated Hss Jobbers' Drill Bit, Wire Ga 80,3/4" Oal,0.1" Drill Depth,118 Deg Point
2 30585A97 3 Each Uncoated Hss Jobbers' Drill Bit, Wire Ga 79,3/4" Oal,0.1" Drill Depth,118 Deg Point
3 30505A5 1 Each Small-hole Drilling Adapter, #99 To #60 Cap, 1/8" Shank Dia, 1-5/16" Oal
 
Ready to open holes up in TBI

I purchased a drill pencil and a complete set of 60 thru 80 number drills. I will follow your instructions as best as possible. I have a good idea where the fuel delivery needs to be increased on the spray bar. Your suggestions are very much in line with what I was going to do. So thanks for the info. I know that eventually this TBI unit will be a very much appreciated device on my engine. I also know that some times it takes a bit of Trouble-shooting to make things work as designed especially if the engine is not stock and has been modified. I do believe if I had a stock 0320 150 HP engine this unit would be a winner right out of the box. but like all of us understand, once you start modifying things, everything else requires a bit of tweaking to work correctly with other parts.

Phil
 
I do believe if I had a stock 0320 150 HP engine this unit would be a winner right out of the box.

That's what I have, and yes, it worked fine "out of the box". Going on a year and half now, no issues so far.

-Dj
 
I agree with the priming procedure, just open the mixture and turn on the boost pump and the idle circuit primes the unit after about 5 or so seconds. I did install a lever on the priming unit so I could pull a cable and manually prime the TBI. However, that is coming out and I am installing a Small Euro door lock motor with 8 Kg force to open the primer unit by pulling the lever I installed. Its a 12 Volt unit and it is about the size of a large Key-Fob.
www.longezpilot.com

I just did this to my TBI and it works great! If you go to Www.facebook.com/radialconversions there is a short video of it working.
 
I don't have the primer hooked up but will put it in sometime soon as a safety item, so that in the event the regulator fails one can control the mixture manually. The only way to do that is with a cable actuator because it might take half throw, or whatever, to get the engine running smoothly. One could practice it by pulling the mixture full lean on runup then using the primer lever jockey it to where the engine runs smoothly.
 
I don't have the primer hooked up but will put it in sometime soon as a safety item, so that in the event the regulator fails one can control the mixture manually. The only way to do that is with a cable actuator because it might take half throw, or whatever, to get the engine running smoothly. One could practice it by pulling the mixture full lean on runup then using the primer lever jockey it to where the engine runs smoothly.

Not a bad idea, although the primer button on my unit won't start to flow any fuel until almost fully depressed. That is why I had to go with a bigger priming solenoid. The first one would only depress the button a little more than half way. This didn't flow any fuel through the regulator at all. Now I have good priming flow when the button is fully depressed. You might have a very narrow window for regulating fuel flow using the primer. It will be interesting to see your results!
 
Actually I found that for normal starting you don't want to prime, at least with an electronic ignition. Any time I messed with the system which required purging air with the primer, the prop would turn half a blade then a kickback would happen. It starts fine with the throttle completely closed and no prime.
 
That's great to hear! Talking with the other Rotec Radial guys it seems that the radials first start needs a good prime, then nothing after that for the rest of the day.
 
TBI Modified

Pulled the ROTEC TBI off the long EZ this morning. Brought it home and started opening up the holes to .018. Everything went very smooth. I returned the unit to the airport and reinstalled on the plane. It started getting late and I just wanted to get things put back together prior to it getting dark . Everything is ready for a test run. However, I am leaving for vacation on the 2nd of September and may not get a chance to try out the increased fuel flow until after the 19th of September when I return. I am looking forward to the TBI performing great!

Phil Camarda
Long EZ N55GR
 
I?m owner one Vans RV-4 in Hungary. We have not experience with Rotec Tbi. We set up the Enigene 0-320 with Rotec Tbi, When i give quick full throttle, engine was not running perfect. I readed this forum, and read much usefull information. We cut the spring 0.606, Engine running much better, but stay one problem.
700 rpm-2000 rpm engine is fine, but 2000 rpms engine hesitates, does not run up, 1-2 sec later running normal to max rpm .
Regulator assembly higher than the tbi is, not leaking, spray bar holes is clear.
The engine with the old marvel carb run fine this is not engine problem.
What is the problem?
Gabor
 
Gabor you will need to drill out the holes in the spraybar as I mentioned. Rotec is of no help in this process. I have traded numerous emails with their support staff and they simply do not understand the product they sell nor do they have any interest in improving their own product. That said you can make it work perfectly as I have. I can't say what sizes of holes are correct for an O-320 so you will have to experiment. This is something THEY (Rotec) should have done or work with customers who know what they're doing.
 
700 rpm-2000 rpm engine is fine, but 2000 rpms engine hesitates, does not run up, 1-2 sec later running normal to max rpm .

The engine with the old marvel carb run fine this is not engine problem.
What is the problem?
Gabor

Gabor,

Unlike your carb, the Rotec lacks an accelerator pump. Slow the throttle movement down a bit and see what happens.

Tony
 
Gabor you will need to drill out the holes in the spraybar as I mentioned.

I've not had to drill anything. Works fine "out of the box" on my 150hp O-320.

As Tony mentioned, there is no accelerator pump. Move the throttle slower and you should have no problem. They mention this in the installation information:

http://www.rotectbi.com/Installation.html

"Set idle mixture screw for best Idle and pick up. The TBI unit does not have an accelerator pump so rapid use of the throttle slide should be avoided. Setting the idle mixture screw a little on the richer side can aid pick up and is recommended."

Once you get it tuned in it works very well. You will like it! :)

-Dj
 
There are two versions of the spraybar the second one having larger holes. Could very well be he has the one with smaller holes.
 
My guess is you're talking apples and oranges. The recommended unit for an O-320 is the 40mm, and for an O-360, 48mm.

Tony
 
Yes i have the 150 hp version o 320 and slower throttle movement the engine run good, just 2000 rpm little hesitate. My country this is first rotec /and rv-4/ and we have not experimence. Setting the idle mixture screw /lean/ running much better in ground, tomorrow will flying, i hope run perfect. Thank for usefull answer.
 
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Firstly, thanks to the group for the info on this subject.
I'm actually a Mustang II guy but frequently search this forum for info as the RV community is vastly larger then the MII one is, and we all use pretty much the same stuff except for airframes.
Thanks to Rocket Bob for the work you have done on this, I was pulling my hair out trying to get my Rotec TBI set up on my 0360, with Vans FAB etc, the usual problem, good idle, good mid-range, Lean kills at WOT, or at least lost RPM and stumbled, added the air grid, helped, reshaped the regulator spring, helped, started drilling out WOT end of spray tube to #78, big help. started slowly did a few, ground tested, did a few more, ended up with about 12 holes opened up to #78 on from 3/4 to all the way to WOT end am now able to WOT and actually lean a bit before lean stumbles start and have consistant smoothness over rpm range from idle. I found it was easier to take the fuel dist tube out of the TBI to drill, that way I could hold it under a lit magnifying glass and was able to use a small fine file to roll over the holes to smooth the tube, then blew the holes with compressed air and brake clean before re installation.(#80 drill made little difference as it is nearly the same as factory holes) Will be doing the final tie down engine run up this week, then to see how it handles ram air in flight. all in all I gained 150 RPM static from previous max RPM. will keep you posted. happy to answer any questions on progress thus far on this particular installation.
regards, Jay
 
Uk Rotec

Hi Guys,
I have been anticipating fitting the Rotec to my RV4 (O320 160hp Superior with dual Pmags MT C/S prop' http://gikonhome.blogspot.co.uk/ ) and reading with interest your developments. Thank you for sharing them.
First flight yesterday showed lean mixture throughout the full throttle range with poor mixture distribution. Using carb' heat improved both distribution and mixture (but I would expect it to affect mix' due hot air/same fuel supply)
My TBI had to go back to Rotec as it had a broken spray bar upon delivery, so they rebuilt it with a new spray bar with "holes opened up to current spec' 0.35mm and 0.40mm (they don't say which ones).
I have considerable experience with getting an Ellison to work well on my Tipsy Nipper some time ago, and will first see what improvements can be made with an air deflector on the face of the air filter and a honeycomb air straightener as suggested earlier on this thread. (The airbox is std)
I wonder if any adjustment to the mixture can be made by altering the pressure regulator spring length.....has anyone tried?
I have uploaded some photos to Flikr: https://www.flickr.com/photos/62722241@N00/sets/72157647983156255/
I wish to run on unleaded Mogas at some time in the future (a LARGE paperwork excercise in the UK) and have temp' sensors on the fuel pump and in the TBI fuel gallery blanking plug to gather data. I saw very high temp's 35degC at both the carb' and the fuel pump before fitting the air ducts to the pump and carb'. I am now seeing much lower temp's but still higher than I would like for mogas. The shield around the TBI is yet to be fitted so will see what I get then.
Any suggestions/support gratefully received.
Neil
 
If you increase the fuel pressure by extending the spring, when the local pressure inside the venturi at WOT there may not be enough pressure differential to draw enough fuel out of the spray bar since at WOT throttle the pressure is at its highest (Bernoulli's principle).

The spring should be sized to deliver the right spraybar pressure for a given flow required of the installation. One-size-for-all is what Rotec sells and it works but definitely could be improved upon. Changing the spring length can cause leaning of the mixture at WOT.

Same goes for the spraybar pattern. Ellison didn't fully get it right either.
 
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Thanks for that.
I flew again today with a 5" piece of alloy tape at the front of the air filter, it made a tiny difference, but I still have terrible mixture distribution. Are you all using the honeycomb air straightener? At 21"/2100rpm I can lean beyond what I could with the M/schleber carb', but anything beyond that the mix' distribution makes the engine run uneven.
Did some aero's to check the inverted pickup, all ok and so, so nice to do a big loop (round rather than egg shaped) and slow rolls inc' stall turns without the engine running down, I have so missed that.
The Ellison I had on the Nipper did not need any adjustment to mixture at any stage once I had perfected the manifold and airfilter, I did not have to mess with drilling the spray bar or anything, I don't see why Rotec can't make the subtle adjustments to order, they have the technology, but I don't think they have the interest.
The carb' is still getting far too hot especially at low throttle settings on approach, got as high as 32degC today with an ambient of 21degC.
Next flights will be with the airflow straightener (honeycomb) and a partial skirt around the top of the airfilter to see if I can reduce the carb' temp'.
Thanks for the info',
Neil
 
I like your idea about the shroud around entire TB, has me thinking, any reason one could not use a small amount of FAB air pre filter to cool the regulator on the TB. If one has a small pressure in the FAB, a short tube from the top plate to the regulator or as in this case open to the inside of the shroud. we seem to need a straightening device anyway to help the turbulent air in the FAB.
any drawbacks?
Also noticed you have the fuel rod in line with centerline, was there a reason for that, think the suggestion was to have it perpendicular.

regards,
 
Ellison have always advocated the throttle slide to be transverse rather than Fore/Aft. I went this way as it seemed that is what the majority have done, but then quite a few of those photographed elsewhere on this forum may not be flying yet? Also it was far simpler to orientate the TBI this way for simplicity of installation. I can't quite get my head around why the transverse/FA should make such a difference. If you ask Rotec they don't seem to know anything about it!
I will update that Flikr account with the shroud.
Neil
 
Flikr updated. The photos of the "skirt" show it installed but not secured. I have used self tappers to attach it to the top of the airfilter FAB. It has also been modified to allow the throttle slide linkage to protrude through the front...photos to follow once I have fitted it.
Just uploaded to Flikr the "shield" I made that fits to the front of the air filter to be used in conjunction with the honeycomb. I am glueing the honeycomb to a alloy "flange" that will be bolted to the airfilter fange, it is shown partly filled with epoxy resin. I have just finished filling the honeycomb where it meets the flange. Hopefully if it is cured enough tomorrow will fit it and report back.
I have to say the idea of adjusting the pressure regulator spring to enrichen the mix' throughout the range is my prefered way of doing business. If the alloy "plug" behind the spring was shimmed it would be a neat way of having a calibrated method.
For the Mogas application where I will have a bleed return from the regulator back to the fuel tanks I am thinking of fitting a nipple to that plug with a calibrated orifice. That is what I had with the Nipper on the Ellison, it worked very well. I have a high-ish fuel pressure (about 6.5-7.0 psi) at the fuel regulator, so bleeding some back to the tanks should work well.
Neil
 
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Bob, you mention several times the improvement when you pull it back slightly off WOT. We have a Rotec 40 TBI on our low compression (6.7-1) 0-235 C2C. running Duel P-Mags. Like you we opened up the spray bar holes slightly but only on the full throttle end of the bar. But this made no difference to the fuel flow or temps on first flight after the mod. But I did notice the temps reduced and stabilised when I pulled it back slightly off WOT. At the time I assumed it was the throttle slide protruding out into the air flow and creating some turbulence thus giving better atomisation and a cleaner burn.
But when I checked the data download from the EFIS, it showed a substantial increase in fuel flow at this throttle setting (as you have found).
To us this indicted an increase in air flow was sucking out more fuel so we assumed the Rotec 40 was too large for our 0-235. With testing we readjusted the throttle cable to get the maximum fuel flow with the knob full in.

On hot days (95*-100*temps) we were sometimes getting a slight stumble on start up and going to full throttle on take off. We over come this problem by insulating the fuel system under the cowl. This included insulating the fuel inlet part of the TBI and fitting blast tubes to the regulator and the fuel inlet of the TBI. This mod not only solved the stumble problems but also increased power in all conditions.

Bob RV9a
 
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From Ellisons online manual, relating to the EFS-2:
EFS-2:

Because the EFS-2 TBI may be installed on a wide range of engine sizes, a throttle stop screw has been incorporated to permit the adjustment of the full throttle opening of the EFS-2 to match the airflow requirements of the engine. This throttle stop has been preset at the factory to approximate the needs of the engine specified in the customer's original order.

The following steps should be followed only if it is determined that the engine runs rough, loses power, or is excessively lean at the full throttle position.

1. Secure the aircraft with tie-downs and wheel chocks.
2. If an absolute pressure manifold pressure gauge is installed, note the reading that occurs prior to engine start. If a manifold vacuum gauge is installed, confirm that the gauge reads "zero" prior to engine start.
3. Start the engine and run at low power until the engine is properly warmed.
4. Slowly open the throttle until the manifold pressure gauge reads 1 to 1.5 inches of mercury less than the pre-start reading. If a manifold vacuum gauge is used, slowly open the throttle until the manifold vacuum reads 1 to 1.5 inch of mercury.
5. While the throttle is locked in the position established in step 4 above, adjust the mixture control to provide peak RPM.
6. With the mixture control secured in the peak RPM position, confirm that the manifold pressure or vacuum gauge reading is unchanged from step 4.
7. Mark, measure, or otherwise note the throttle position so that this position can be reset following engine shutdown.
 
Like I said previously in this thread the notion of restricting the WOT throttle travel is a bandaid approach to fixing the incorrect hole pattern at WOT throttle.
 
I would think a pressure drop of 1.5"Hg would be unsatisfactory.
After all "fuel injection" is supposed to make more power than carburation.
My son Peter has a stock Rotec TBI-40-4 on his RV-4, O-320, 160 HP FP prop. It runs perfectly out of the box. His RV-4 has the old style unfiltered ram air inlet which makes a 90 degree turn up into the injector, which is mounted with the slide bar fore-and-aft.
So intake air and orientation are 'wrong' but it works 'right' ...go figure?
Because of his success, I bought the same Rotec unit for my T-18 which has an O-290 FP.
This thread is especially interesting to me because my O-290 might be a bit small for the Rotec TBI-40-4.
My T-18 has a manifold pressure gauge, so useful even with a FP prop. I'll be thinking of the manifold pressure vs 'lean out' near full throttle.
 
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......TBI......Throttle Body Injector has always been a moot point......its a carby mate, not fuel injection! (put another tinny on the BBQ!)
 
I have found an ideal way of finding a cheap but robust air straightener that will fit the Rotec 40-4 and probably the other sizes.
Many Air Flow Meters (AFM) for cars have a honeycomb air straightener just before the sensor. Some of these have a stainless steel mesh just behind it to catch any stray big lumps of anything including the honeycomb. They are plastic but designed to withstand a hostile under-bonnet environment. The one I have used comes from a Mercedes 200 (Merc' pt#: 000 0940948 Bosch pt#: 0 280217 114) which cost £10 (cheaper than making one from alloy honeycomb) from ebay.
Once I cut the end off of the unit I also found it has a perfect flange diameter to locate between the TBI bolts, using stand off spacers so that the flange is not crushed or the bolts bent under stress.
It made a big difference to the mix' distribution and allows LOP a long way before engine roughness.
Pic's here: https://www.flickr.com/photos/62722241@N00/sets/72157647983156255/
You will also see the heat shield I have fitted around the TBI which has reduced the TBI temp's to around 20degC from 39degC. The heat shield has a forced air supply from the Port intake baffle.
 
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......regarding the fuel pressure regulator spring length, I have just found this on the Rotec website:

If the regulator flow valve spring is over-tensioned, the regulator will limit fuel flow causing the engine to run lean.

This effect will be most noticeable at high power settings (WOT), as air velocity across the spray bar is minimal due to the throat being fully open. The result is a low negative pressure at the spray bar, causing the diaphragm to apply minimal force against the regulator flow valve spring, allowing an inadequate fuel flow for the system.
At the low and middle range power settings, the engine will run normally using the fast velocity of air running across the spray bar due to the smaller throttle opening and hence greater air velocity across the spray bar.
If the regulator flow valve spring is under-tensioned, it could leak fuel after shut down and the system could potentially be running rich as extra fuel will be leaking into the system unnecessarily.

To check length of the regulator flow valve spring:

Using a 19 mm or 3/4″ socket, remove the regulator threaded plug on the rear of the regulator.
Ensure the regulator flow valve, o-ring and spring are not lost upon removal.
Measure the length of the regulator flow valve spring. Under zero compression it should measure between 15 mm ? 17 mm (0.59″ ? 0.67″) in length.
If the spring is out of size, it can stretched or compressed to create the desired length. Although ideally an unmodified spring should be used.
 
After Opening Spray Bar holes

Well. I had a chance to fly the bird several times after opening up every hole in the spray bar with a #78 drill. I had to move the mixture with every move of the throttle as there was too much fuel getting delivered to the engine at every RPM setting. Leaning was not an issue but the possibility of fuel flooding the engine was very real. The engine would stumble and sputter if I did not reduce mixture in sink with throttle. The two levers almost ran parallel (side by side) for smooth operation. I enlarged way to many holes.

I contacted Rotec and ordered another fuel delivery tube. This time I only drilled out 7 of the holes at the Wide open throttle end. Unit is reinstalled back in the plane. Was going to go up today but had other items to deal with. I am sure that each ROTEC unit if designed for a standard HP engine is used on a non modified standard engine will work great. It does take a bit of tuning / tweaking to tune one of these units on a modified engine with higher compression and or a different cam profile.

More to come. By the way, all the mechanical and fiberglass work is done. Plus, paint is on the plane. Last item on the list is tuning the Rotec for best performance and operation.

Phil
Long EZ N55GR
 
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