Jab Plenum Chambers

[jetjr]

The CAE toca runs around 75- 78 deg oil temps

 

Unless theres a measurement location discrepency, thats too low

 

You can buy a 88 deg unit for the toca but that sees 80-85 deg in the sump

 

This maybe says that temp monitoring location is a bit cooler than elsewhere.

 

As with cht being measured on one cyl, this may mean those seeing 100 deg oil temps infact have much higher elsewhere in the circuit

 

In hydraulic lifter engines, temp and pressure variation has to have efects on lifters operation

 

 

[Bruce Tuncks]

My engine was one of the first with an oil cooler. Before that, Rod Stiff reckoned the finned sump was enough.

 

It turned out that the temp probe was too short and the real oil temp was too high.

 

 

[facthunter]

I've always tried to do enough flying to fully heat the motor when used and avoid water contamination. When hydrocarbons burn, water is produced. Quite a lot of it and it goes past the rings together with other products of combustion forming acids (condensed in the oil).. Water in suspension will cause what has been mentioned with Oscar's post .(High pressure steam). Bearings under load run hot and the oil is what cools them. Alutin and copper-lead don't have as good antifriction figures as Babbit lined bearings and have extra clearance when used to allow more oil flow to provide the cooling effect. Where you measure the oil temp is important. Synthetic oils can stand more temperature than "Mineral" oils but the water could still be a disaster. Nev

 

 

[Oscar]

The CAE toca runs around 75- 78 deg oil tempsUnless theres a measurement location discrepency, thats too low

You can buy a 88 deg unit for the toca but that sees 80-85 deg in the sump

 

This maybe says that temp monitoring location is a bit cooler than elsewhere.

 

As with cht being measured on one cyl, this may mean those seeing 100 deg oil temps infact have much higher elsewhere in the circuit

 

In hydraulic lifter engines, temp and pressure variation has to have efects on lifters operation

Apologies: my previous post re the CAMit TOCA was not well-worded.

 

I have the '88-degree' thermostat installed, which ( as I understand it), means it 'cracks' at 88 C and is fully open at about 96C.

 

The location of the standard Jab. OT sensor places it in the oil that is cooled by heat transfer from the alloy sump in the general air blast from the oil cooler intake, creating an 'inversion layer' in the oil in the sump. What that causes, is a fairly thin layer of well-cooled oil, over the top of which the hotter recirculated oil slides around the engine.

 

The TOCA thermostat reacts to the OT being delivered at the oil cooler take-off - i.e. effectively the last point in the oil delivery system. Unlike the OT sensor, it is getting the oil that has done the work of lubricating (and cooling) of the engine bearing surfaces.

 

 

[jetjr]

Are you sure about that?

 

My understanding is it is after pump and before oil goes into lube circuit

 

PRV dumps excess back to sump and toca opens oil cooler into circuit

 

Oil pressure sender is at the outlet of PRV ......why it doesnt move much and honestly doesnt tell too much about whats going on in the engine until temps allow it to flow properly. The lower port below it is apparantly the end of engine oil circuit, much more useful place but numbers are a bit of a worry when hot.

 

If my info is correct then the toca see’s oil from sump temps, maybe a bit warmer as it goes through pump and block to filter.

 

The numbers above are from my experience in using both spec toca waxstats, the rated temp is a bit above where they regulate, maybe cracked open is all it takes. I sure dont see anything above 96 even 38deg hard climbs

 

Actually a shame they dont make another step higher.

 

 

[Oscar]

jj - I think I have confused myself, and you are correct. Mind out to lunch, I suspect...

 

 

[jabiruken]

No dramas at all Ken, will just take what I can get as you really seem to have the best figures I have ever seen!!!

Seb can’t locate video after my move, it’ll show up in some stupid place I’m sure, took photos whilst doing oil change this morning the lower cowl has deflectors which hug around tail pipes, the video showed engine on stand with cowls fitted and blanked off at fire walll end, he used a smoke/fog machine and a large fan, u could clearly see the air flow through the cowl and swirling effects, personally I think it’s all a bit over the top as I found just little bits of tweaking on previous jabs had fair result with many hours flown on engine relatively trouble free.

 

 

 

 

 

 

[seb7701]

Thanks for checking Ken, as I must admit, that video would be the most interesting thing yet, given I have actually been checking for smoke machines to try just that very experiement!!

 

Nonetheless, the lower cowl shots seem to be quite similar to what I have been seeing on the lower cowl of whats now seems quite a famous RV4 of american airflow 'guru' Dave Anders. He had curved bits on his firewall to 'arrange' the flow outwards, like yours. (I'll see if I can find the shot of his...)

 

Two things I have been wondering about yours (yes, I actually have been...)

 

1. I don't suppose it's ever best tested without the balance hose between the ducts? (I have been infinitely curious as to whether that would help...)

 

2. How the intakes on yours compare to mine, as many have opened theirs up quite a bit from the older style top cowl like ours. Yours seems a hybrid of sorts, but bloody hell, it obviously works!!!!

 

If you ever happen to be walking past yours with the tape measure.....I am still debating whether to open the top or open the bottom more, although I am very much thinking I need to change my lower cowl to this 'overlap' style I spied on a J120 at the factory.

 

 

 

 

[Bruce Tuncks]

My upper cowl was modified by lowering the underside of the holes by about an inch to better fit the front of the ducts.

 

I also tweaked the ducts, blocking off gaps where air could escape without going near the cooling fins, and at the same time I made baffles to direct all the air from the lower cowl hole to go through the oil cooler.

 

These ideas came from a Limbach site, so no clever thinking on my part.

 

Too many things at once, so bad science but the engine ran cooler after that.

 

 

[Paul davenport]

At last after much tweaking the results are as displayed

 

 

 

[jetjr]

Just a update, I tried the round hole intake (rather than NACA)........bugger all difference to EGT. Evened out a tiny bit, mixture has changed to a little richer but hardly noticeable

 

 

[Paul davenport]

Just a update, I tried the round hole intake (rather than NACA)........bugger all difference to EGT. Evened out a tiny bit, mixture has changed to a little richer but hardly noticeable

Depressing isn’t it, when all your efforts are for naught. Hang in there when you find the answer it will have been staring at you . I need to put a larger main jet in to reduce wot egt, but for the moment I am one happy little veggie.

 

 

[biggles]

At last after much tweaking the results are as displayed

Paul,

 

If this is your aircraft , you can easily adjust the instrument to give you an almost full scale deflection. I have my EGT's set to 750 degrees and CHT's set to 160 degrees, like this....... Bob

 

 

 

[Bruce Tuncks]

paul, I drilled out my main jet to lower the wide-open egt. It is supposed to be lower than when you close the throttle a bit, but it was higher.

 

So I drilled it out again ( I have a set of number drills) and this reduced the egt a bit but it is still highest on WOT.

 

I don't dare to drill it out again without knowing more.

 

 

[Paul davenport]

paul, I drilled out my main jet to lower the wide-open egt. It is supposed to be lower than when you close the throttle a bit, but it was higher.So I drilled it out again ( I have a set of number drills) and this reduced the egt a bit but it is still highest on WOT.

I don't dare to drill it out again without knowing more.

I have a mushroom needle and matching needle jet and a 255 main jet. I have a 270 main jet to install next service, but for now I just want to fly it

 

 

[jetjr]

A couple of ideas, only a few cents worth.

 

The main and needle jet work together, not individually as it seems in tuning instructions

 

Whichever one is restricting flow is keeping lean @ WOT

 

To complicate this the needle moves to block (or not) the needle jet. If the needle isn't moving correctly it can restrict fuel.

 

If you are increasing Main jet without results Id suggest theres issues with needle jet setup. Either needle isn't moving up or its profile isn't working on your setup.

 

Could also be a max fuel flow problem too, could be a fuel restriction dropping level in bowl.

 

And FYI mine has always run leaner at WOT same as you indicate. Chased it for years with no result. I just back off throttle a tiny bit as soon as practical. Its one cylinder in particular so I now reckon its to do with air distribution at high flows through intake and carb.

 

 

[derekliston]

paul, I drilled out my main jet to lower the wide-open egt. It is supposed to be lower than when you close the throttle a bit, but it was higher.So I drilled it out again ( I have a set of number drills) and this reduced the egt a bit but it is still highest on WOT.

I don't dare to drill it out again without knowing more.

Probably just being a bit obtuse and I’ll kick myself for asking, but what is WOT? (Was going to just say Wot’s Wot, but figured I might get some funny responses!)

 

 

[Camel]

Wide Open Throttle ! Don't feel you need to kick yourself as many others would be the same ! .---- Acronyms !

 

 

[Bruce Tuncks]

Sorry, in real life I hate people who WIFA ( write in fu....err....funny acronyms.)

 

The extreme use of acronyms by CASA and the meteorological reports proves to me that they rate the benefits of a closed shop higher than safety.

 

 

[Jaba-who]

Sorry, in real life I hate people who WIFA ( write in fu....err....funny acronyms.)The extreme use of acronyms by CASA and the meteorological reports proves to me that they rate the benefits of a closed shop higher than safety.

The safety or rather lack of it with acronyms has been shown worldwide in the medical literature.

Even seemingly basic acronyms often have different meanings in different places. Can lead to some serious mistakes.

 

These days if you write a piece for publication it won’t be accepted unless all acronyms are defined at the first use in the paper.

 

 

[facthunter]

The MET stuff is an international code. It $#1ts me as much as it does you, though. Follow up to Jaba -who there are overlapping meanings like ADF WAS a radio compass Now Australian Defence Forces. It's not a lot harder to SAY the full word. Writing it takes a bit longer. Checking it out can take quite a while so it's another possible area of confusion. Not needed in Aviation..Nev

 

 

[derekliston]

Wide Open Throttle ! Don't feel you need to kick yourself as many others would be the same ! .---- Acronyms !

After I posted my query I realised that might be the answer. I don’t have too many temperature problems, only oil temp on a sustained climb, but I’m hoping that goes away when I change from straight oil next oil change.

 

 

[Paul davenport]

A couple of ideas, only a few cents worth.The main and needle jet work together, not individually as it seems in tuning instructions

Whichever one is restricting flow is keeping lean @ WOT

 

To complicate this the needle moves to block (or not) the needle jet. If the needle isn't moving correctly it can restrict fuel.

 

If you are increasing Main jet without results Id suggest theres issues with needle jet setup. Either needle isn't moving up or its profile isn't working on your setup.

 

Could also be a max fuel flow problem too, could be a fuel restriction dropping level in bowl.

 

And FYI mine has always run leaner at WOT same as you indicate. Chased it for years with no result. I just back off throttle a tiny bit as soon as practical. Its one cylinder in particular so I now reckon its to do with air distribution at high flows through intake and carb.

Yes mine works just as yours does and I just back off a bit , just out of interest what temp are you running cht egt in cruise and what does your egt get to on climb before you back off

 

 

[Paul davenport]

Yes mine works just as yours does and I just back off a bit , just out of interest what temp are you running cht egt in cruise and what does your egt get to on climb before you back off

Oops also what main jet are you using

 

 

[Bruce Tuncks]

One day I said to myself " DBAW" " GAGOY" and UTBGTRTFT"

 

and the third acronym wasn't in the glossary! I reckon we should copy the medicos and castrate acronym users.

 

( DBAW = don't be a wuss; GAGOY = get a grip on yourself; UTBGTRTFT= use the blasted glossary to read the F'n thing)