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Thread: #6

  1. #1051
    Join Date
    12th February 2004 - 10:29
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    bucket FZR/MB100
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    Henderson, Waitakere
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    The Honda CB125T has a new home. Bit of a shame we didn't manage to run it on a track with the new 150cc kit. Hopefully it will be at the next Tokoroa round.

  2. #1052
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    12th February 2004 - 10:29
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    Back working on the Yamaha FZR twin. I had a suspicion about the fuel pump. I had to turn the adjustable fuel pressure regulator until flow was stopped to get only 2.8bar pressure. I tried an original regulator but it was a faulty one and fuel pressure was only going to 1bar. Eventually swapped out the fuel pump for one on loan from Rob and straight away had more flow at the lower pressure by the looks of the bubbles scooting round in the clear portions of the fuel lines. With the rising rate regulator I was able to easily increase fuel pressure over 3bar whilst maintaining plenty of flow. With the manifold input open to ambient I've set the pressure to 3bar. With the engine running the fuel pressure should drop down but when it pulls boost the pressure should increase which is what I want. This has been another good exercise to remind me about measuring everything.

  3. #1053
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    12th February 2004 - 10:29
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    I'm still not happy about the fuel pressure. I was doing work on the bike today and ran the pump. The pressure was going over 3bar despite when I last ran it having it set to 3bar. I adjusted it easy enough but it casts suspicions on pressure regulation so I'll be keeping an eye on it. I might even log fuel pressure using a spare analogue input. The main thing I was looking at today was the cause of oil seeping out around the cam cover. I suspect the problem is an oversupply to the head. I did have the banjo bolt in the head with the roughly 1mm restrictor hole. I didn't have a problem with the other engine with or without the turbo. What I suspect is that due to only having half the head all the oil is being supplied to the remaining side and it is simply too much. Greg had a similar problem and hopefully has gotten around it by adding a drain. As an experiment I added a 2nd restricted banjo bolt to the crankcase end of the feed pipe. I'll try it tomorrow probably. The turbo supply line has a 1mm restrictor in it to reduce the flow to the turbo. The main man in Greenlane Speed Shop informed me it would be required back when I bought the supply line for the turbo. I have a gauge on the main oil supply gallery and the pressure is sitting around 60psi. I find it surprising how the supply needs to be restricted. There is a small restrictor in the crankcases as well but I think that is to stop all the oil falling through the gearbox bearings leaving non for anywhere else. My turbo Z1 has a 7mm restrictor on the oil pump outlet in an attempt to gain a bit of pressure to the turbo. In that case I'm pretty sure it still only goes to about 5psi. that pressure feeds the galleries that go to the head for the cams so it really doesn't seem that a whole lot of pressure is required, as long as it is fed to the bearings. I may end up tapping the end of a banjo bolt and fitting a soldered up carb jet and fit that to the head.

  4. #1054
    Join Date
    3rd February 2004 - 08:11
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    1982 Suzuki GS1100GK, 2008 KLR650
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    Wallaceville, Upper hutt
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    Ball bearing turbo or plain bearing? I have no experience with ball bearing turbo but I would expect you would want as much (within reason) pressure and volume to a plain bearing turbo as you can get, as long as you have a big enough drain to get the oil back to the crankcase. Likewise with the head if they are plain bearing cams, get the oil out of the head and back to the cases. Smokey Yunnick wrote a book about "Tuning the small block Chev" which had a lot of good info about oil flow through an engine and how little is actually required in the bearings and how to get it back into the the sump, away from the crank and how much parasitic drag oil will add to anything rotating
    it's not a bad thing till you throw a KLR into the mix.
    those cheap ass bitches can do anything with ductape.
    (PostalDave on ADVrider)

  5. #1055
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    13th June 2010 - 17:47
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    The oil drain on mine is from just below the top edge of the head casting down to the flat plate covering the unused half of the cases. Return is well away from rotating pieces.
    Mike's problem is only temporary. Once the turbo is back on it, the excess oil has somewhere to go and the head doesn't overfill.
    Because mine is running unblown and there is a definite lack of drainage capacity I added the drain.

  6. #1056
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    12th February 2004 - 10:29
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    Both turbos are plain bearing. The guy at the speed shop was pretty definite about restricting flow to the turbo. He said too much would cause a problem draining and oil would seep past the seals and cause problems. With the 1mm restrictor in the turbo oil feed line the pressure at the turbo can't be very high given the probable reasonably free flowing bearings of the turbo. So far that side of things hasn't been a problem. The Z1 turbo is probably only getting maybe 5psi. Supposedly the old Rajay turbos were very tolerant of low pressure oil supply. Ball bearing turbos would need hardly any oil I imagine, especially a watercooled version. They'd be similar to aviation turbines in that regard, maybe.
    On the Yamaha twin both the head and the turbo are fed from the main oil gallery. I currently have a gauge on that and see 60psi. The head is fed from the oil gallery via an external line. Normally one banjo bolt has a restrictive orifice of about 1.1mm. In my case, with the turbo fitted, the banjo bolt that screwed into the main oil gallery is a free flowing double fitting. The restrictions are in each supply line, to the head and the turbo so each restriction saw 60psi from the gallery and reduced flow. Neither will have an effect on the other as any flow diverted from the main gallery will be compensated by the pressure bypass valve in the bottom of the cases which will maintain the oil pressure by reducing the bypass to compensate.

  7. #1057
    Join Date
    3rd February 2004 - 08:11
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    1982 Suzuki GS1100GK, 2008 KLR650
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    Another useful book of information is by Hugh MacInness, who was the inventor of the Rajay version of the floating turbo bearing.

    I have this book somewhere and pretty sure it doesn't say anything about restricting flow TO the turbo, only making sure that the drain is correctly sized and unimpeded as, in his words, the oil coming out "looks like dirty whipped cream and flows about the same"

    https://www.amazon.com/Turbochargers...95861356&psc=1
    it's not a bad thing till you throw a KLR into the mix.
    those cheap ass bitches can do anything with ductape.
    (PostalDave on ADVrider)

  8. #1058
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    12th February 2004 - 10:29
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    The original turbo I bought was a Rajay. I was going to put it on an XS1100 in about 1979. Things changed and it ended up on my McIntosh Z1. Z1s have a roller bearing bottom end and the oil falls through the bearings with practically no hindrance. It only proves how little oil is actually needed for the cam bearings. IIRC the oil pressure was something like 2-3psi at 3000rpm. With the restrictor it raised pressure for the turbo at the expense of restricting flow to the rest of the motor. If you were silly enough to connect a light to the pressure switch, the light would be blinking at you every time you opened the throttle and most of the way down the back straight at Puke. Despite this there were no obvious problems with supply to the cam bearings. I have got a baffled deep sump. The baffle is hinged and only restricts oil movement to the rear.
    Depending on the restriction of the IHI turbo bearings there may not be much in the way of oil pressure at the turbo. There will be plenty of oil, as much as can pass through a 1mm hole at 60psi.

  9. #1059
    Join Date
    3rd February 2004 - 08:11
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    1982 Suzuki GS1100GK, 2008 KLR650
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    Getting a little off topic here but WRT cam plain bearings - KLR650s also have a full rolling element bottom end and can run on an oil mist, much like a two stroke. The cams are plain bearing and will fail to the point of killing the cylinder head while the bottom end just keeps on going, for some time after the motor runs out of oil, which it is wont to do because of marginal piston ring design coupled with insufficient drain back holes behind the oil ring. A lot of thought and effort has been out into reducing the crank supply (it gets far too much, which ends up on the cylinder walls, which the rings cant deal with, so it gets pushed up into the combustion chamber and burnt - so the engine runs out of oil) and increasing the cam supply by drilling out the banjos of the head oil feed pipe. The crank oil is reduced by a restrictor in the crank feed,which also help keep the oil pressure up (so the cams can have more)

    So I would take exception to your statement about the amount needed for the cam bearings.

    In the case of the KLR, a modified Chev 350 piston fixes the oil problem by 1/much better rings and 2/ much bigger drainback holes.The added capacity (685) doesn't hurt either.

    Sorry for going on a bit.
    it's not a bad thing till you throw a KLR into the mix.
    those cheap ass bitches can do anything with ductape.
    (PostalDave on ADVrider)

  10. #1060
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    13th June 2010 - 17:47
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    In this case Mike's not wrong about the cam bearings. The 250 heads have roughly the same total bearing area as an FZR1000 but the spring loads are about 1/6 as high. The bearing load/area is very, very low.
    The cam oiling is also very good. The cams are hollow and oil is fed into them with holes at each journal.

  11. #1061
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    18th May 2007 - 20:23
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    RG50 and 76 Suzuki GP125 Buckets
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    .
    This talk about turbos is interesting. As the rules for F4 now allow <70cc turbo two strokes. I have a small turbo and a <70cc cylinder for the RG engine......... .... what to do!!

  12. #1062
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    4th December 2011 - 22:52
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    Yamaha XJ750 1982
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    South Africa
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    Quote Originally Posted by TZ350 View Post
    .
    This talk about turbos is interesting. As the rules for F4 now allow <70cc turbo two strokes. I have a small turbo and a <70cc cylinder for the RG engine......... .... what to do!!
    Sim it, quite an interesting rabbit hole to venture into....

  13. #1063
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    12th February 2004 - 10:29
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    What to do seems pretty obvious to me.

  14. #1064
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    12th February 2004 - 10:29
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    holes with rabbits in them, worms in a can, they both come to mind when thinking about a turbo 2-stroke. May as well throw in fuel injection as well.

  15. #1065
    Join Date
    12th February 2004 - 10:29
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    Fired the bike up this arvo with the main fuel map axis set to TP/Revs. After an initial reluctance to get going it seemed fine and was quickly tuned to have reasonable lambda readings at the ranges where it was running. It was very snappy on the throttle. I still need to adjust the 0% throttle settings above idle rpm as it goes very lean. Carburetors do the exact same thing so I'm not too worried from an engine protection perspective. I need to do it at the lower rev range before I start finessing the cold start enrichment which are all % increases of the base value in the fuel map. Throttle Position(TP) is way easier to tune than MAP on this engine. Idling at about 4,000rpm it has about 70-80 kPa manifold pressure(MAP). The MAP immediately goes to 100kPa when the throttle is blipped which is normal atmospheric. The only time MAP drops below 70kPa is when the throttle is closed above idle rpm. It's easy to see why cold engines get abysmal fuel economy. The enrichment percentages are large. Once over the initial startup, which sees something like 200% increase in fuel, it settles to something like 45-50% extra "post-start" which decreases over about 4 seconds, and settles on about 20% extra for warmup which decreases as the cylinder head warms up. Short trips where the engine doesn't really warm up are going to be bad for economy.

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