02GF74
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| posted on 20/7/18 at 08:42 PM |
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I was suggesting running engine up to temp without the prop I. E. No cooling to see if uneven temperature is due to the air cooling.
Also what is the mac running temperature?
Is the temperature difference causing any problems, if not, then maybe you are worrying over nothing.
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Pigsy
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| posted on 20/7/18 at 10:02 PM |
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Pikes peak is at 14114.17 feet. Injection beats carburetion there hands down.
When was the engine last rebuilt? Are the oil-ways clear on the hot bank? If you are running the standard air cooling shrouds then surely it will be
down to the forced air passing through them, not around them to do the cooling, especially if completely encased. I now rest my laurels. Please do not
reply to me now.
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Mr Whippy
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| posted on 21/7/18 at 03:21 AM |
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stupid question... but have you spoken to Jabiru? compared to some manufacturers I've seen they seem very helpful, the also have some very good
docs online on cowling which are some of the best I've seen yet (I'm quite into planes...) -
linky 1
linky 2
I like their flow visualisation, quite funny and probably very true 
I notice that your cowl does not match their pics inside, they are showing air dams which seems to be totally missing on yours. As you say the later
head is so much better fin wise, can the heads be swapped?
I'd have a chat first with them and they have a forum...
Welcome to the fun and rather costly  world of private planes.... 
[Edited on 21/7/18 by Mr Whippy]
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russbost
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| posted on 21/7/18 at 08:36 AM |
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quote:
Originally posted by steve m
Russ,
What is baffling me, is which bank is at fault, is it the hot one is too hot, and shouldn't be, or the cool one is to cold, and should be
hotter?
Does the engine have separate EGT gauges, as in one for each bank, and if it does, are you able to verify that both are reading the same temps ?can
they be swapped with wiring to the opposite sides, to allow a comparison ?
Is carb heat fitted? and if so is it working off one bank or both,
Are the cold air feed ducts the same size, and placed equally behind the propeller,
Hot air needs to exit the cowling equally from both sides, does the hot side have any obstructions in its air exit, like startermotor
battery, or any large obstruction, that would impede its exit
steve
The one at fault is defo the hot one, tho' the cool one, at cruise is actually slightly cooler than ideal, but at present we certainly
don't want to take ANY cooling away from the engine as a whole, you would think, given that it's a dirty great aluminium casting that heat
would soak fairly immediately from one side to the other, however that's certainly not the case, I can only guess the cast iron barrels act as a
barrier to heat transfer
Separate EGT's, yes, & after various minor changes early on in the induction system when we first had the plane we now have very equally
balanced EGT's (within, frequently 10 deg or so, which with no.'s in the 600's is very close indeed)
It has carb heat as a manual heat redirect off the exhaust, we tend to pull that as soon as temps get a little high as it gives only a fractional
reduction in power, but because it draws less dense air that richens the nix slightly, EGT's drop almost immediately & there is a slight
drop in head temps shortly after. There is also a low & high electric carb heat which we always have switched on , on the low setting, we've
truied that on, off, high & low & there is no visible difference in performance or any temps
Cold air ducts are the same & equally placed (tho' actually all sorts of reasons why they probs shouldn't be)
WE've looked at the exits & various size additional "spoiler flaps" have been added to the bottom of the cowl, the cabin heat is
taken from the exhaust on the LHS & does block part of the exit, so we recently removed that (don't need cabin heat at present!) & it
made not a scrap of difference
This is what is so frustrating, every time you see something that could be a possible canditate, it turns out to be another dead end!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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russbost
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| posted on 21/7/18 at 08:46 AM |
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quote:
Originally posted by 02GF74
I was suggesting running engine up to temp without the prop I. E. No cooling to see if uneven temperature is due to the air cooling.
Also what is the mac running temperature?
Is the temperature difference causing any problems, if not, then maybe you are worrying over nothing.
That is effectively what we've done by blanking off the air entry ducts, you are specifically forbidden to run the engine with no prop, I assume
to easy to over rev.
Max running temp depends on who you speak to & which particular pilot's handbook you refer to, Jabiru keep moving the goalposts, when our
engine was built, absolute max was 220 deg C, 200 for max 5 mins & continuous at 180 - we can comply with those figures providing you control
temps on climbout when heavy & with no headwind (worse case scenario) with carb heat pulled (see above) & sometimes a slight reduction in
throttle, however, Jabiru have since issued various updates suggesting significantly lower temps with the later heads etc. which is still the same
engine.
If you approach Jabiru they will not give a firm answer (I believe there have been some court cases in Aus where they are based) & say helpful
things like "refer to pilot's handbook"
The temp difference isn't causing any actual problems at present, nor has it in the past, but it is quite obvious that something isn't as
it should be &, for longer engine life it would obviously be better if more equally balanced. It can be somewhat of a distraction on climbout, we
have a warning light which kicks on at a preset temp, & the last thing you want around a busy airfield is to have your eyes & concentration
inside the cockpit rather than outside where it should be
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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russbost
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| posted on 21/7/18 at 08:56 AM |
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quote:
Originally posted by Mr Whippy
stupid question... but have you spoken to Jabiru? compared to some manufacturers I've seen they seem very helpful, the also have some very good
docs online on cowling which are some of the best I've seen yet (I'm quite into planes...) -
linky 1
linky 2
I like their flow visualisation, quite funny and probably very true
I notice that your cowl does not match their pics inside, they are showing air dams which seems to be totally missing on yours. As you say the later
head is so much better fin wise, can the heads be swapped?
I'd have a chat first with them and they have a forum...
Welcome to the fun and rather costly world of private planes....
[Edited on 21/7/18 by Mr Whippy]
See above re talking to Jabiru! Our cowls are actually very similar to those shown in the diagrams on the first link, you can't really see the
air dams as they are the same colour as the plenum itself (other than the temp ali one) & have somewhat "disappeared" on the pics,
we've tried various minor changes with the air dams, added to them, removed them etc etc, you can get more cooling to, say, no. 6, but you
sacrifice cooling on 2 & 4 to do so, & so on, what you CAN'T do is get cooling from 1,3 & 5 to 2, 4 & 6! I did recently suggest
to my colleague who has been tearing his hair out on this project with me, that it might be best to start from scratch with an empty cowl, &
gradually add parts, checking on the ground each time bits are added
My colleague has spent some considerable time on the Jab forums, lots of peeps seem to have similar issues, but nothing quite as unbalanced like
ours
Been playing private planes for some years now, not actually that costly, probably not a lot more than plenty of peeps spend on a kitcar or a
motorbike, if you're in a sensible sized group & doing your own maintenance, but sometimes it does seem like we're spending more time
working on it than flying it!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Mr Whippy
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| posted on 21/7/18 at 02:55 PM |
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they do seems to have reliability issues with their engines just now and serious restrictions soon to be in place because of this. I was into light
planes about 15 years ago with Cessna's, sailplanes, then 3 axis microlights then flex wings but the hanger costs got too much (was only me as
the owner) and the useless weather here and even more useless forecasts ended up just making it frustrating and I had a few scares (even one forced
landing in a field...) so decided to call it quits while I was still alive and sold up and got into kit cars. Now my flying is all rc planes &
heli's but still love planes
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Beardy
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| posted on 21/7/18 at 03:25 PM |
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could it be exhaust design causing the temperature imbalance?
First thought was prop wash spiral input to the cooling ducts, or similar different airflow over the exit hole causing different cooling air
extraction, but might it be that one side of exhaust is more restrictive?
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russbost
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| posted on 21/7/18 at 05:36 PM |
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quote:
Originally posted by Mr Whippy
they do seems to have reliability issues with their engines just now and serious restrictions soon to be in place because of this. I was into light
planes about 15 years ago with Cessna's, sailplanes, then 3 axis microlights then flex wings but the hanger costs got too much (was only me as
the owner) and the useless weather here and even more useless forecasts ended up just making it frustrating and I had a few scares (even one forced
landing in a field...) so decided to call it quits while I was still alive and sold up and got into kit cars. Now my flying is all rc planes &
heli's but still love planes
I wouldn't say they have reliability issues with the engines as such, the problems tend to be when people don't monitor temps properly
&/or abuse the installation & certainly not aware of any issues/restrictions in the offing??? (bear in mind we've had the plane around 4
& 1/2 years, it's been flown to Spain & back during that time, never missed a beat & it's all still functioning fine) Unless
you know something I don't?
& yeah, hangarage is a b*gger if you're paying it on your own, & if you think it was bad in Scotland, just imagine what us poor sods
down in the South pay for it!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
|
russbost
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| posted on 21/7/18 at 05:47 PM |
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quote:
Originally posted by Beardy
could it be exhaust design causing the temperature imbalance?
First thought was prop wash spiral input to the cooling ducts, or similar different airflow over the exit hole causing different cooling air
extraction, but might it be that one side of exhaust is more restrictive?
I actually think that is about the most likely thing, I had a good look at the exhaust when we serviced it, the design is stupid, it goes forward
& then turns around to go back into the box which is toward the rear of that ali plenum chamber underneath that I pictured in the first post, but
the bank that gets hotter has 2 outlets that go in the direction of flow, then the 3rd (which is no. 2) gets added to the flow of gas, but actually
points probably 20 degrees or so in the wrong direction, ie any gases flowing from no. 2 are actually trying to push the gases from 4 & 6 back up
the headers. It does NOT do the same thing on the RH bank (the cooler one), all the exits point in the direction of flow, albeit that the exit from
no.1 is probably only 15 or 20 degrees off perpendicular to the main flow, but at least not pointing in the wrong direction.
Unfortunately to do anything about that we'd need to apply for a mod & I'm not at all sure they'd let us have it, alternatively,
we can fit the later exhaust, which is far better designed, but to do so you need to get the heads milled as the later system doesn't have
gaskets! If we're pulling the heads off anyway, we might just as well bite the bullet & replace them along with exhaust, cowls, plenums -
the lot
I think until that point it's going to be a question of applying sticking plasters until such time as the engine needs a strip anyway.
The only "good" side to it is that it's highly unlikely to result in the engine stopping suddenly, most likely occurrence would be a
burnt valve, which just gives a power drop, so you'd have no probs in making an airfield to land again ............
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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