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dmech

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Everything posted by dmech

  1. Mate, I been engine reconditioning for 47 yrs I've used a lot of mahle pistons, been to many seminars conducted by them per invite from my suppliers. I think you just being the ostrich here
  2. Have seen a few sl and ci piston failures Breaking etc over my 47 Yr in engine reconditioning usually this was addressed by the manufactura or after market. ACL made pistons oem for local vehicle makers. I to have made hyperutectic pistons with slots for race engine that took out to state titles over 2 yrs this was running up 7000 rpm 32 laps, absolutely no probls with pistons. Also another s 6 sedan 2 state titles same engine all of shelf ordinary Rd parts used ACL duralite 060" no speed shop parts used in this engine mod cam ground to my specs by camshaft engineering as that was the only maching that I farmed out. Also a lot ofst stock and modified sedan engines for others all very competitive. I had a datsun 1600 st stock that took out over all points at our club for 3 consecutive yrs this engine was running ACL slotted pistons and often ran up to 9000rpm, yes I did have some valve failures but was able to eliminate them. This car also took out the Brian rose memorial for 2 consecutive yrs ,this car was the smallest engine , competing against 3300cc holden toranas. So I to have had plenty of experience with pistons and I do know what causes the cast piston to break in the jab I have also seen solid slots break and seize in the jab as well, and even one early gen 1 ACL piston which was the only one I had to discard the crank case and 2 con rods also camshaft and some followers. You say you have made pistons,please tell us here on the forum how you would design a piston for the jab ie; material heat treatment cam on skirt skirt type that would fit in jab engine clearance periphery , skirt surface Finnish for the steel n Barrels , taper on skirt, tell us what you know!! Adrian
  3. Ihabe informed glen rf guy of company to get pistons and part numbers. He has since posted pics which have part number on them, check his earlier post
  4. Can't see mahle written on it. Can you provide more detailed pics similar to how glen posted earlier. How about part number may be it will fit the jab , not sure where I will find an injector to suit. BTW it is for Ci engine. But could just throw it in and see, at least that will be more than what happens on forums Adrian
  5. OK nev I agree cast is ok and slotted piston of right design more than adequate. The jab one can be modified To work. If you know pistons , you should be able to work out the problem, it stocks out like dogs balls. You say cast ok, I say to you stop talking about it and find one, or show us a design that WILL Work! I have a modified jab slotted skirt piston 4 of, any one care to try it , do the test under the prolonged worst conditions.. At the Monment we have the mahles straight off the shelf and if fitted correctly with the right rings work well, we have 2 engines that reached 2000 hrs under about the worst conditions and still going good, they more than likely go on for another1000 hrs , however the engine is mandated for complete rebuild at 2000 hrs Adrian
  6. I did inform glen where to get pistons from, and he has progressed from there. These pistons have been available in australia for years.
  7. Forged pistons, so your saying that these won't work in jab engine. I can tell you that the marles that I have fitted have done more than2 thousand hrs in a flying school a craft , this is the same set and there are two other planes getting close to the same hrs, without any problems. We have approx 15 a craft flying successfully with mahles fitted including mine. I have done the hard work and expense to do the necessary engineering to make these work in the jab engine. The trouble with forums there is a lot of hypothetical theories, and arm chair engineers.i have done the engineering and trials and testing with the help of a flying school , about the hardiest test available and this has been on going since 2018. I don't want to hear of people throwing mahle pistons in there planes and then getting on these forums bagging them because they have experienced expensive problems . I was advising glen of our successful use of these pistons by email and pm,s. And don't appreciate it being put on forums At this stage all info I gave to him was for his own use on his a craft. Adrian
  8. just out of interest, it seems that no one actually said or explained what was going on and causing the starter run on. it looks to me after looking at solenoid connections that it was in a latching mode. automotive solenoids often have an extra primary terminal as well as the button terminal , the first terminal goes hot + when the solenoid is activated, this provided to bypass the coil ballast resistor only when starting the engine in certain vehicles, since the diode was connected across these two terminals and if diode was connected wrong way around or shorted it would cause a latching event, which would require the battery to be disconnected to un latch the solenoid. Anyway glad to see it got sorted out
  9. what has happened to the old classifieds , will they return?
  10. Hi nev what do you think of those specs I gave you?. Would like to hear your comment
  11. Hi nev, got some measurements from an old barrel wear marks yesterday from a gen3 jab piston exits the barrel spigots by 20.12 mm [792"]. Piston we are using exits by [ .204" ] measured from bottom of oil groove . Skirt engagement of jab piston 25.9mm [ 1.019"], piston we are using 31.5mm [1.241"] [ oil ring groove higher up] all measurements are at bdc . the piston we are using is a light weight forged piston with a more resilient material , strong as, but comes with its own set of problems as well, but at least no breakups after a 1000 hrs and inspection indicates they could be used again. dmech.
  12. nev I will look at measurements on piston over the week end. High sill and flex does work if their working environment is engineered correctly , as it does in the holden v6 ,However not in a jab. You might say the same about high carbon steel and flex, like valve springs for instance , set them up wrong and they break to. The pistons are designed to flex but they have limitations , like most things metal. The piston does come a considerable way out of the cyl. spigots as you suggest, however there is very little angle load as it is bdc . I and others here ,are using a different piston to the jab, whi we are using different pistons , not sure how they would go on the jab pistons , we had these made in the u.s and quiet expensive , but worth every cent I reckon. ch is lower sill. content .about 10% the jab piston is hyper sill content and hardened to t6 t5 would be better which is what acl used to use. However a small mod to the present pistons will sort the cracking problem.
  13. Thank's for info one-track, just an article I read inside a dc3 on display at the Mareeba air port QLD. Was just outside a repair facility there . That was 15 yrs ago.
  14. I read some where , I think it was at Mareeba airport, that the Russians copied and made more dc3 s than the original manufacturer never paid a cent for license or copyright .
  15. Hi Nev Not my rod length/ stroke ratio , that's the ratio used in the jab engine and with piston offset of .020" the wrong way around . The piston was designed for a longer rod, as used in the holden v6 nearly 2:1. I would never build an engine with a cr/str ratio of 1.5:1 in a light crank case. I have been involved in engine reconditioning [now retired] for the last 46 yrs and had a lot of contact with ACL tech dept. during that time especially in regard to race engines that I was involved with, I used to use their off the shelf pistons and brgs etc. ,while others were using special forged pistons and other expensive components from speed shops. I could build an engine for around$700-$1500 , while others were spending4-5 times that . We won a lot of races including several state titles & classics , with a lot of different makes of engines over a period of more than 10 yrs , all with normal every day parts supplied by ACL, not once did we have a piston or brg failure. had lot of respect for their parts. With regard to the slots , I absolutely know for sure ,that it is not a factor or cause of the piston failure in the jab engine, also the rod length is not a part of it either , the pistons are brittle because of the high silicon content and the frozen in solution heat treatment, so the slot is beneficial,, as it allows the somewhat thin skirt to spring/flex , it also controls the heat flow from the crown into the skirt, thus having an effect on the expansion characteristics .
  16. because of the jab engine design!, pin does not exit the cylinder on a Lycoming . Piston has to be slab sided on a jab. to fit down into crank case , the jab is very compact compared to Lycoming and jab has a much shorter conrod , conrod stroke ratio of approx. 1.5:1, the engine [vn v6 that the pistons were designed for] has a cr stroke ratio of 1.98:1 nearly 2:1. Generally the shorter the cr/stroke ratio the more offset on the pin. The holden v6 piston has an offset of .020", another vehicle I looked at [ Toyota] with similar c/r/stroke ratio to the jab has an offset of.080".how ever in the jab case it has nothing to do with the cause of piston breakage. I don't know what the ratio is on the Lycoming but it looks quiet long , I have one in the workshop at the moment , I will measure it tomorrow. The jab engine is what it is ,and we have had to work with its design to overcome the piston issues , at the moment we have two engines that have just achieved 1000 hrs without breaking pistons ,and these engines have seen some hard work and run only on 95 mogas. these engines have been stripped down for top end o/haul as mandated by jab. otherwise were running fine. The pistons are almost as good as the day we installed them 1000 hrs ago. These are being crack tested and I'm sure they can go another term. Over the last 2 yrs we have tried another ring package ,[ that we had made], in 2 other engines one a 6 cyl, which has now done 200 hrs over 2 and abitt yrs and in all that time has only put about 25cc of oil in the catch can. I need to mention before I go, the slot in the piston has nothing to do with the pistons breaking up. We have not tried jabs hd piston, which looks like a reincarnation of the old acl piston in shape at least, doubt metallurgy is the same. ACL made good pistons, pity they had to close up.
  17. "Solid" I take it, you mean no slot plenty of petrol trucks run slotted /split skirt pistons . They used to work hard, from memory nearly always overloaded back in those days. Jabiru uses an auto piston and can be made to work ok in the jabiru engine .
  18. when I did my automotive mechanical engineering and for the last 45 yrs that I have been actively involved in it , a split skirt referred to a vertical split with a hole drilled each end , similar to the old Bedford truck was an example .The opening under the oil ring was referred as a slot . Which as most mechanics will say it is to allow oil to drain , however that is not its main purpose . I know why these pistons are cracking, and how to rectify it. The heavy duty pistons because of its design will crack in a gen 3 and more likely cause cylinder problems in a gen 4 eventually. I know of a gen 3 fitted with hd pistons that seized with in3 hours, was just curious whether any one has had good results with hd in a gen 3.
  19. nev, are you referring to the slot under the oil ring. dmech
  20. not directly to me but im told it did , not about the cracking though , my comment, because I know it happens and have seen several engines with cracked pistons in all cylinders.
  21. Has anyone fitted the new gen 4 piston in a gen 3 with any success . I'm told the gen 3 piston is no longer available. probably because of skirt's cracking.
  22. Was just a by product of changing to a different type piston, piston change wasn't intended for increased power. Piston were changed to prevent piston break up which seems to have worked, this project has cost us a huge amount of money and time , we are now working on a ring pack to complement this piston and we have had some amazing results so far with one engine 3300 has done over 130 hrs and absolutely no oil in the bottle, bottle is bone dry, we havnt striped this engine to see how cylinders are going ,[ owner wont allow us ] but I hope to bore scope cylinders next week
  23. Sorry did not reply earlier , we went on nbn wireless , nothing but trouble since. All the pistons , except for one set , were VR pistons. the other 4 were Silverlite brand, we tried these because they had a lot more material in the skirt area where the VR pistons were cracking, they only made 130 hrs before cracking , they cracked from the oil ring slot downwards and inwards, where as the VRs cracked from the bottom of the skirt upwards and inwards. We had 2 sets of VRs only made around 260hrs each with about 8 hrs difference between them. We are experimenting with another piston , and have close to 1000 hrs on one set and 700 on another set, but not without some problems, which I think we have now overcome, how ever there has never been any signs of cracks, and produce more power
  24. Sorry Jim 188 , didn't mean to blast any ones ears , if that's what it means. Sounds like your very close to this a/craft , can you tell me , did the A.T.S.B. establish the cause of the piston breaking up?. Camit pistons were from same manufacturer as the jab ones [pre valve relief]. mine reached 260 hrs with no problem at all temps were always good, good power very little oil consumption ,then without any warning a piston broke up. I'm asking the question because I have established the cause of the pistons breaking up . We have repaired one of those engines , which has over 800 hrs so far with out any problems , should easily make 1000 hrs ,is often used on 40 plus days. hi ambient temps are not a factor in the cause of these piston break ups, in fact they are beneficial, cool days are a factor though. The piston problem just dose not happen after just one or to events ,but fatigue over a long period of events over time.
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