Jab Plenum Chambers

[Oscar]

Oil temps too low can be a problem too. Oil can get diluted with fuel and water ( combustion makes water vapor) and you need to boil these off. This is one reason why a few minutes of ground running is not good enough to keep off corrosion.My old Jab 2200A had low oil temps so I partially blocked the lower-cowl intake hole. Then one day I was in climbout on a hot day ( over 30 ) and the oil temp went into the yellow.

Now I have put in more ducting plates etc to ensure that the air coming in to the lower cowl all goes through the oil cooler and not around it.

 

What would be nice would be a flap-plate to control the air going to the oil cooler but this would be too complicated I reckon.

Thank the gods that I bought a CAMit TOCA ( Thermostatically-controlled Oil Cooler Adaptor) while they were available. That's the 'pro' way: you have sufficient oil-cooling capacity installed, and the TOCA takes care of the amount being cooled. Quick oil-temp rise on first start-up - so no lingering on the ground waiting for the oil-temp to rise while simultaneously cooking the heads..

 

 

[seb7701]

Not sure which XR's they were, (have to be one of the very first perhaps?) as they are about THE most bullet proof air cooled bike around since the mid 80's at least, but that's for a different forum I guess!!!

 

 

[jetjr]

The CAE unit works brilliantly

 

80 deg except full power in hot weather and it gets to 90

 

Theres a guy in UK makes a similar thing

 

 

[Oscar]

Yep, I know a few blokes still running one CHT monitor on their engines, in which case I guess ignorance is bliss, although that ignorance is what caused others to overheat my no.2 pot once upon a time, as there used to be a CHT ring on no.4 only!!I'm sure VW's and Honda XR bikes are immune to the effects of normal thermodynamics!!!

Ever tried to start an XL350 on a sub-zero day? I KID YOU NOT, I used to stand mine over the embers of the camp-fire for about 20 minutes before I could get the bastard to start. ( Alpine Rallyes, around 1974 - 1978).

 

 

[seb7701]

Ah-ha, I KNEW you old fellas were talking pre-80's Hondas!!! Lol!!!

 

Love to see a photo of the oil thingy....although even I can't figure out how to post pics at present??? My oil temps is OK, but I have often thought of cheating and whacking in a 6cyl cooler...

 

 

[bexrbetter]

Ah-ha, I KNEW you old fellas were talking pre-80's Hondas!!! Lol!!!

No, I am referring to a couple of early 80's XR range that some moron engineer in Honda decided they would be fine with just a bit over 1 liter of oil. There were numbers of failures in Oz and hotter areas of the US as the oil boiled away. Oil cooler sales were high as it not only cooled, but increased the capacity.

 

 

[seb7701]

Well there you go eh? Only had the pleasure of flogging (and I mean FLOGGING) 1 x '85 350 and 3 x 600's from the 90's and gosh darn, the can't be killed. As such, very popular with contract musterers out here and further, who would probably pass out if they saw their own oil temps some days I would reckon!

 

 

[bexrbetter]

Well there you go eh? Only had the pleasure of flogging (and I mean FLOGGING) 1 x '85 350 and 3 x 600's from the 90's and gosh darn, the can't be killed. As such, very popular with contract musterers out here and further, who would probably pass out if they saw their own oil temps some days I would reckon!

It was the 83 and 84 models, the 350 suffered the worst as they were heavy and had to be ridden a bit harder. The 85 was considered a great bike, single carb, dry sump and disc brake. the 600's were pretty well bulletproof as they were lower stressed.

 

I went SL 70, SL 125, XL 175, XL250 Motorsport with 305 kit, TT500 Yammy ... then I found 2 strokes and never looked back.

 

 

[seb7701]

Well, after some very enticing claims regarding ducting of oil coolers, I spent some time over the past two days knocking up something similar. To say that I am curious as to the effect is an understatement!!! Here's the before and afters...

 

 

 

 

 

[derekliston]

Well, after some very enticing claims regarding ducting of oil coolers, I spent some time over the past two days knocking up something similar. To say that I am curious as to the effect is an understatement!!! Here's the before and afters...

I'll be very interested in your results!

 

 

[seb7701]

Yeah well...don't rush into the duct thing.... Tested briefly this afternoon, with very odd results.

 

No.1 up by 6deg?? (still only 116 on a 30 deg day...it's my golden haired cylinder!)

 

No.4 up around 9 degrees. (which is just bizarre, as it is now within 2 degrees of no.2. They are usually 20 degrees difference.)

 

I am wondering whether the outlet size has something to do with it, given the relatively slim outlet. Might possibly need to tape a big lip just in front of it to see if that get the flow happening or perhaps just chuck it in the bin...

 

It's been an odd week. First I chopped the side out of the duct and enclosed the plug leads (ala picture) which simply jacked up the temp on the back cylinder, rather than helping with some increased volume and reduced leakage with no plug lead holes. I also added a read deflector, which seems to have made bugger all difference also.

 

At this stage it looks like I'll have to re-order and 'old' style duct again, as thing were pretty bearable at least with that configuration. I am at a loss.

 

Here's the outlet area and the modified duct for interest sake.

 

 

 

 

 

 

[horsefeathers]

Yeah well...don't rush into the duct thing.... Tested briefly this afternoon, with very odd results.No.1 up by 6deg?? (still only 116 on a 30 deg day...it's my golden haired cylinder!)

No.4 up around 9 degrees. (which is just bizarre, as it is now within 2 degrees of no.2. They are usually 20 degrees difference.)

 

..................

 

.

Can you tell me what your CHTs on all cylinders were then?

 

And what about your oil temp?

 

 

[seb7701]

Can you tell me what your CHTs on all cylinders were then?And what about your oil temp?

---------------------------------------------

Monday - with butterfly added between cylinders and that rear deflector looking thingy

 

OAT 28deg

 

Oil - 92ish

 

#1 110deg

 

#2 160deg

 

#3 141deg

 

#4 151

 

Today - with oil cooler duct added

 

OAT 29deg

 

#1 116

 

#2 162

 

#3 142

 

#4 160

 

Oil temp was weird - 92ish, but later saw 100, but it may have not cooled down after a quick climb, so hard to say, but was expecting great things in the oil temp especially.

 

-------------------------------------------------

 

As a comparison - before getting a new barrel on no2 and modification of the left hand duct to enclose the plug leads, this was a typical set of numbers-

 

OAT 27deg

 

Oil 95

 

#1 112

 

#2 154

 

#3 139

 

#4 146

 

Overall - if I can get back to this, I think I'll live with it and concentrate on some more lower cowl mods, which I have played with and shaved a few more degrees off.

 

Oh, and I haven't even bothered to put a fence in front of no.1, but I know it knocked 18 degrees off!!!

 

 

[seb7701]

Out of curiosity, what CHT's are you guys seeing at 30deg OAT??? I need some comparisons if possible....

 

 

[Old Koreelah]

Out of curiosity, what CHT's are you guys seeing at 30deg OAT??? I need some comparisons if possible....

Here's my installation, Seb. The stupid climate panel has reverted to F, but you can see it's a hot day.

Since then I've significantly reduced CHTs with better cowl flaps; they're so effective the head temps stay under 145C even after a long idle on the ground- but it might be a different story in hot summer weather.

 

 

 

[jetjr]

 

thats 12 deg OAT, 124 kts IAS, I do have carb heat on a little, disturbed air - not heated, helps even EGT out a lot

 

air temps doesnt change it much other than during take off climb, one CHT will get to 150-160.

 

New CAE CHT probes read fair bit hotter, I think its closer to real number.

 

Im keen to lower these significantly.

 

 

[Bruce Tuncks]

Mine are similar to yours to yours jetjr . I will fly tomorrow ( 26 forecast) and take some pics.

 

 

[seb7701]

Thanks to all of you guys - appreciated. Previously, a lot of the comparison temps were at much lower OAT's. I must say that the first flight today was at 25 and the last at 30deg, by which point the EGT's are now longer as even. I do wonder what effect air density has on the EGT's...

 

My readings got more bizarre as the day went on after 4 test laps with same temps regardless of various mods. Annoyingly, no.4 is now within 2 degrees of no. 2. If it weren't a breach of forum rules, I'd be using profanities by now!!!!!n Just ridiculous when my pax side duct was whacked on stock standard and shows a temps of 116/140 wile the driver's side is was a pair of 160's by the end.

 

New duct in the mail and hopefully will regarding some normality...I am sooooo over this!!!!

 

 

[jabiruken]

Thanks to all of you guys - appreciated. Previously, a lot of the comparison temps were at much lower OAT's. I must say that the first flight today was at 25 and the last at 30deg, by which point the EGT's are now longer as even. I do wonder what effect air density has on the EGT's...My readings got more bizarre as the day went on after 4 test laps with same temps regardless of various mods. Annoyingly, no.4 is now within 2 degrees of no. 2. If it weren't a breach of forum rules, I'd be using profanities by now!!!!!n Just ridiculous when my pax side duct was whacked on stock standard and shows a temps of 116/140 wile the driver's side is was a pair of 160's by the end.

 

New duct in the mail and hopefully will regarding some normality...I am sooooo over this!!!!

 

 

[jabiruken]

I bought this jab because of the builders detail to duct work etc. photo taken at 32 deg day @ 1000 feet last year.

Oil cooler attached to lower cowl, large opening lower cowl and hand made air ducts that Inclose spark plugs and has scat hose at rear of ducts used to balance air between the 2.

 

On hard climb no 3 can reach 156 on a stinking hot day but lowering nose will quickly lower temps.

 

Oil is a bit cool, but I don’t want to play around with it and up set something else

 

 

[seb7701]

Thanks Ken - although those temps are almost depressing!! Just goes to show what is possible. All I can say is next time you have the cowl off, I would very much appreciate a few snaps if you have the time, as you obviously have the golden goose of setups with temps like that!!! I would be particularly interested in the lower cowl opening and lips also. Those temps are just a marvel, particularly in terms of how even they are!

 

 

[jabiruken]

Thanks Ken - although those temps are almost depressing!! Just goes to show what is possible. All I can say is next time you have the cowl off, I would very much appreciate a few snaps if you have the time, as you obviously have the golden goose of setups with temps like that!!! I would be particularly interested in the lower cowl opening and lips also. Those temps are just a marvel, particularly in terms of how even they are!

 

 

 

 

 

 

 

[seb7701]

Thanks Ken!!! Just got back from hols, so hadn't noticed the post but just about to pour over the photos for some solutions!!!!

 

 

[seb7701]

VERY interesting cowl work!

 

Sorry, but there were always going to be some questions!!!

 

1. Sorry to be painful, but any chance of some rough dimensions of your intakes at some stage (even just the yellow sections)? I took a chunk out of mine, as per the red section in the attached photo, but looking at them both, mine still has a LOT to open up!

 

Interestingly yours still seem to have more material on the bottom of the openings, so I guess the top of your cowls have flared upwards a fair bit?

 

2. Are there any thoughts on what the insert in the intake is doing (just focussing some flow through the head?) and is there anything similar on the left hand side at all, given the upwards prop blasting on the 'driver' side?

 

3. Which oil cooler and is it ducted exclusively out the bottom or is all exhaust air mixed in together?

 

The scat joining the two ducts, well that's got me beat, but fascinated...

 

Thanks again!

 

 

 

 

[jabiruken]

VERY interesting cowl work!Sorry, but there were always going to be some questions!!!

 

1. Sorry to be painful, but any chance of some rough dimensions of your intakes at some stage (even just the yellow sections)? I took a chunk out of mine, as per the red section in the attached photo, but looking at them both, mine still has a LOT to open up!

 

Interestingly yours still seem to have more material on the bottom of the openings, so I guess the top of your cowls have flared upwards a fair bit?

 

2. Are there any thoughts on what the insert in the intake is doing (just focussing some flow through the head?) and is there anything similar on the left hand side at all, given the upwards prop blasting on the 'driver' side?

 

3. Which oil cooler and is it ducted exclusively out the bottom or is all exhaust air mixed in together?

 

The scat joining the two ducts, well that's got me beat, but fascinated...

 

Thanks again!

Hi, Seb

My intakes appear standard with an insert (grey coloured) in pics. You need to remove these inserts prior to removing cowl as they are screwed in. The hole intake moulds are not jabiru and are hand made of thick fibreglass and there is no deflector on drivers side, completely open unlike photo of passengers.

 

Yes oil cooler is from bottom inlet and cooler mounted on lower cowl then air forced into lower cowl that exits with exhaust.

 

I have a video somewhere that shows the engine on bench with smoke and fan showing air flow.

 

Will try to locate if you wish.. I think the scat hose is used as a balance for air pressure balance during different angles of attack, not sure but all seems to work ok.