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Post by arttu on Dec 3, 2013 11:37:51 GMT
Another question.... On a random internet pic i saw the oil return line from the turbo connected inside the sump to the oil pick-up, so that the oil pump "sucks" the oil from the turbo, eliminating the need for a scavenge pump. Is this a good idea? Anyone done it before with good results? No first hand experience but since no one else has commented... As far as I know that is a working solution for oil scavenging. But there is a risk to restrict the pump intake too much and hurt engine lubrication. Several guys on the old forum used this. Mostly with good results I guess but I remember reading some comments about damaged crank bearings. I would recommend to mount the turbo high enough for gravity drain and consider scavenge pumps only as last resort. There should be enough room on that gixxer for proper turbo mounting.
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Post by captain chaos on Dec 3, 2013 12:22:51 GMT
actually it's not so easy. I'm afraid gravity draining will not be enough, some kind of pump will be needed.
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Post by katana on Dec 3, 2013 21:44:16 GMT
This was a method shown in one of the Turbo-Bike mags a good 10-15 years ago. It requires you to add a spring steel flap over the oil pick-up opening in the sump so it bias's oil pull from the turbo then the sump. Its all a bit 'hit & miss' / dark arts IMO. I preferred not to use electric pump so adapted a mechanical pump to be driven off the crank, so even if it sucks the turbo dry and pulls air - it doesn't affect engine oil supply system!
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Post by arttu on Dec 4, 2013 7:18:02 GMT
actually it's not so easy. I'm afraid gravity draining will not be enough, some kind of pump will be needed. Well, I haven't done turbo headers for oil cooled gixxers so I don't know how easy it is. But I'm quite sure it's doable with most of "normal" turbos. There are plenty of turbo gixxers using gravity drain and for example Proboost turbo kits work with gravity drain. Larger turbos like Holset HX35 might be too big to fit high enough unless using some weird arrangement like placing the turbo on side of the engine. Shaft of the turbo needs to be just few centimeters above oil level.
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Post by captain chaos on Dec 4, 2013 8:17:59 GMT
actually it's not so easy. I'm afraid gravity draining will not be enough, some kind of pump will be needed. Shaft of the turbo needs to be just few centimeters above oil level. That's usefull to know, thanks. I'll have a close look next time when i'm near the bike.
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Post by nitro on Dec 4, 2013 13:35:49 GMT
With my Bi-Turbo I had always problmes with gravity drain. Turbos are appr. 15cm obove oillevel and drain hose was 3/4"! Since then I always put a mechanical pump to the crank and never had problems again.
To use the engine ooil pump as scanvange pump is not a good idea IMO. I know some people use this mechod with success. I made a test by fitting my mechanical scavenge pump directly to the turbo without catchtank and breather with a transparent line and it sucks a lot of air! So also the engine oil pump would suck that air IMO.
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Post by captain chaos on Dec 4, 2013 15:08:14 GMT
maybe i didn't explain it clearly, on the pic i saw the oil return line was not connected to the oil pick-up, but the end was just below where the pick-up sucks the oil. But anyway if the oil return line returns mostly air then it's not a good idea to have that air near where the oil pump sucks. Some sort of scavenge pump will probably be needed.
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Post by captain chaos on Dec 5, 2013 19:08:34 GMT
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Post by katana on Dec 6, 2013 10:35:18 GMT
Had a look today, the shaft is around 3cm above oil level. It might be ok. Don't be so sure! The running oil level will drop some but also the actual turbo drain is significantly lower than the shaft centreline! Ideally the drain needs to empty above running oil level so there is no restriction! If not the drain line will be permanently full of oil which will back up the pipe on braking so it could smoke a bit! Its the problem with having the oil cooler at the front - you can't make decent upward bent pipes for the exh. manifold to lift the turbo..........unless you use unequal length pipes?
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Post by captain chaos on Dec 6, 2013 11:18:57 GMT
Had a look today, the shaft is around 3cm above oil level. It might be ok. Don't be so sure! The running oil level will drop some but also the actual turbo drain is significantly lower than the shaft centreline! Ideally the drain needs to empty above running oil level so there is no restriction! If not the drain line will be permanently full of oil which will back up the pipe on braking so it could smoke a bit! Its the problem with having the oil cooler at the front - you can't make decent upward bent pipes for the exh. manifold to lift the turbo..........unless you use unequal length pipes? so what Arttu said earlier ("Shaft of the turbo needs to be just few centimeters above oil level.") is not true? Anyway the headers have been made, the turbo will not be lifted.
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Post by nitro on Dec 6, 2013 16:27:51 GMT
It´s different. I had massive drain problems with 19mm id gravity drain with 15cm above oillevel. I heard from others, they have no probs with a few cm above oil level...
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Post by katana on Dec 6, 2013 18:46:48 GMT
Every build can be different - excess oil in, restricted oil out, etc etc etc. My own install had the shaft sort of near running oil level and was forever backing up and dribbling into the compressor - total PITA! Hence I swapped out the Hahn Racing drain into the sump / pick-up and used a mechanical scavenge. Bonus is no /little drain back on engine off.
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Post by Kristjan on Dec 7, 2013 10:59:46 GMT
I was just thinking... to have good gravity drain from turbo, you would need good crankcase ventilation to avoid pressure inside the crankcase?
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Post by katana on Dec 7, 2013 15:33:27 GMT
I was just thinking... to have good gravity drain from turbo, you would need good crankcase ventilation to avoid pressure inside the crankcase? Yep! More and bigger is better! I've used the std cam cover breather + an additional cam cover one to Dash 10, a Dash 8 one from the oil filler and an additional Dash 10 from centre of clutch cover! But if its high boost you want, you need excessive venting as blow by on the rings is a reality.
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Post by captain chaos on Dec 15, 2013 7:00:05 GMT
Found this info:
"Pressure below the membrane is needed. On the GSXR1100 model 92 with the 40mm carbs you have a seperate “venting” system with external hoses. Those are not suitable to pressurize. I removed that system, plugged the holes and drilled holes from the bellmouth towards under the diafram. When you drill you cross a not used hole. You have to plug that up also to prevent leakage and pressure drop. So it is made like the earlier models: the 36 and 38 mm CV carbs do not have this system."
The holes from bellmouth to under the diafram, what size should they be? Or is that not really important? Don't want to drill too big and f*ck up the carbs.
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