Mechanical Lifters

[Thx1137]

I have heard that converting a Jabs hydraulic lifters to mechanical lifters can improve climb performance. Can anyone support this and give me idea of the improvement experienced?

 

We often have a bit of sink on upwind on a couple of our runways and climbing out at 150 to 200 fpm (near MTOW) with the treetops just below the wheels is a little too exciting for me!

 

Steven.

 

 

[turboplanner]

Everyone seemed to be desperate to get hydraulics lifters on the Jab, but I'm not up on the detail on the benefits of going the other way.

 

Has anyone designed a tuned exhaust system which is approved by Jab?

 

 

[facthunter]

Hydraulic Lifter removal.

 

The main reason for using these things is to save tinkering. (Frequent manual adjustment)

 

The downside is that you don't get any indication of what is happening to your valves/ seats.

 

they ( the lifters), can FAIL. RARE but it has happened to me Once and it nearly caused a bad SITUATION. NOT in a Jab, BUT they ALL operate on the SAME principle.

 

IF you change the lifters the CAM PROFILE should be changed also as the "ramps" are different.

 

I have always favoured "Solid" lifters in my aircraft engines. Nev.

 

 

[Guest Andys@coffs]

Wayne Johns is the Jabiru engines agent in SA and recently when discussing engine health, including the enrichening changes he made the comment that he spends a lot of his working life in recent years doing the conversions you discussed. Suggest that he may well be someone worth discussing the issue with. PM me if you want his contact details, or give Jabiru a ring and ask for those contact details from them. Wayne also has converted his 3300 to be fuel injected if that is something you might also be interested in discussing. If I recall correctly its not full closed loop monitoring of lambda as there arent good O2 sensors that will cope with the lead in Avgas

 

Andy

 

P.S, Ive never found that doing the lifter adjustments was that much of a hassle, as Nev says, its another source of data that can be used to understand what is happening in the top end of the engine. I was taught that the process is not a go/no go measurement of gap followed by an adjustment back to stated tolerance, rather its careful measurement of current state gap, document that for trend purposes in the Aircraft log book and then you can do that adjustment back to what is needed.

 

P.P.S Turbo, Iv'e certainly heard lots of people discussing the conversion from hydrolic to solid, I've never heard the reverse discussions taking place.

 

 

[turboplanner]

But if the object is to get more power - say 3% to 5% for a safety margin on TO how would just this conversion do it?

 

 

[facthunter]

Extra Power.

 

The simple answer is that it should make very little difference. Hydraulic to solid. There has been some suggestion that high oil pressures can cause the lifters to "pump up" a little causing some power loss. It is not recommended to raise the spring pressure on the relief valve for this reason.

 

Getting to the question of the exhaust system being modified to give greater power, the problem is always having the room and how do you get rid of the excess heat? The exhaust on the Jabiru looks pretty neat to me, and without playing with the camshaft and the other usual things, might not achieve much on it's own. The later 4-cyls are supposed to dyno 85 HP anyhow. The biggest factor in getting the full Take-off power from the engine, is to fit the prop that gives the full rated RPM specified for T.O. Nev.

 

 

[Guest Andys@coffs]

All of the times I have heard people discussing solids vs hydrolics it has never been about power one way or the other, always about reliability. Me personally, I dont know enough to take a stake in that argument one way or the other, obviously from my earlier post I have solids in the J3300, though that wasnt a conscious determination one way or the other, rather just what was available in the 2nd hand market at the time I was hunting a suitable J230

 

Andy

 

P.S, the EFI fitting I discussed above may be a better choice if lookinmg for more hp, though I say that with only passing comments to base it on. Nothing that quick phone call with Wayne wouldnt solve

 

 

[turboplanner]

Going step by step from Nev's post, assuming that's done, the exhaust question depends on how efficient the gas flow is now and whether the pulses could be timed so they suck gas out and thereby provide more efficiency and a power boost.

 

If this has already been done by the designer, then forget it.

 

If not, then the two key features are what Nev mentioned, layout and heat disposal.

 

If the layout has curved bends with few obstructions, then tuning can be limited to adjusting the ends of the pipes.

 

Removing sprigs ribs, blueprinting gasket flanges etc and adjusting the lengths can give you a solid push in the back, HOWEVER:

 

Extracting more power then using more power will shorten life cycle

 

Mistakes (too much heat, suck back etc which can be joked over with a race car beside the road, can't be tolerated on aircraft)

 

I'm not going any further with this except to say that this is a possible avenue for a qualified developer.

 

 

[Thx1137]

No worries. Thanks guys. I expect we don't really want to do much to it so I will probably just have to live with and plan for it.

 

I am already losing 10 kilos so I can add a bit more fuel (gives me a reason to diet). No way I am losing more for climb performance!

 

Steven.

 

 

[slartibartfast]

You could change the prop for one that climbs better - obviously you would trade some cruise speed for it though.

 

 

[skybum]

It is not a simple task swapping from hydraulic to solid lifters. Cam must also be swapped over.

 

 

[Guest Andys@coffs]

You could change the prop for one that climbs better - obviously you would trade some cruise speed for it though.

There is the prop they use for glider towing, I believe the loss of cruise speed is between 5 and 10kts, however "going up" is something you notice rather than something you wish for

 

Andy

 

 

[Vev]

Steve,

 

I did a couple of simple things to my 160 to get it to perform a bit better.

 

1. I fitted a ground adjustable prop and made sure I could get 2900 rpm static run up and 3000 on take off and climb. Letting the engine rev really makes a difference.

 

2. Fitted NGK Iridum plugs .. these seem to give me may be 25 rpm more on static.

 

3. I wraped the exhaust in bandage .. not completely sure if this made a huge difference but it did helped keep the temps down.

 

4. Fitted the recommended richer jets in the carby

 

In my experiance the adjustable prop is the go .... the trick is to let the engine rev and develop the HP. You hold higher revs on cruise but the Jab Engine guys tell you that's a good thing.

 

Cheers

 

Jack

 

 

[turboplanner]

3. I wraped the exhaust in bandage .. not completely sure if this made a huge difference but it did helped keep the temps down.

This is where I got nervous Jack. Before I did that I would have put at least 4 or 5 pyrometers in the engine bay for before and after testing to ensure hot spots didn't migrate up or down the pipe and cook something. In a car you can say "that didn't work", up there you won't need a sentence.

 

 

[Vev]

G'day Turboplanner,

 

Re exhaust bandage.

 

I had spoken with a number of experts as well as had quite a bit of feedback from a few on this forum before I tried it. In addition to this I ran an oil condition monitoring programme and did an oil test every hour to track the impact for 50 hrs to look for wear metals and oxidation levels ... I also shared the results with a couple of very good engineers that have a lot of experiance in this area. I persoanlly didn't run temp probs in the engine compartment but a lame in SA did and reported the temp reductions on this site.

 

It's now been in place for a bit over 200hrs and i'm still doing condition monitoring ever 25 hrs and not seeing anything to be concerned about, however I am enjoying a lower engine bay temp which is kinder to all things electric.

 

Btw... I also reported the mode to the RAA to put it on the record.

 

As I said ... If i had to pick one performance improvement I would do the adjustable prop hands down.

 

Cheers

 

Jack

 

 

[jetjr]

Hydraulic lifters engines were problematic for a long while, leaving many to doubt the benefit of the change and pushing back to solids which are a known quantity, but I think with the newer cam and development the hydraulic types are working OK

 

Ive got solids and happy with adjustments as they rarely need much just a check

 

Exhaust, latest 6 cyl setup with single large outlet is a tuned type supposably adding a few HP. ($1800 so had better do something good)

 

Wayne does know about injection but as its only permitted on 19 reg AC as well as him being very busy he isnt interested in setting them up but may help getting you on the right track

 

 

[wizzard1964]

I've heard that the solid lifter motors have a bit more grunt, mine has solid lifters.

 

the later model jabs have bigger exhausts than my sk2200, and bigger carbies.

 

Speak to Donny in the Jabiru engine shop, no-one knows more about them... hes got a hot 2200, the prop idea is the most economical, Maybe use course prop in Winter, fine prop in Summer? . . . WG