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post #1 of 5 Old 08-27-2007, 11:48 AM Thread Starter
 
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Turbo engine questions (SC28)

Hi all, I'm a new member here!

I have some problems with reliability and I am running out of ideas. The engine is turbocharged and has nearly 300 hp, so it wears quite fast anyway, but I am hoping for some improvements

Conrod bearings are having a hard time and yet again #3 bigend failed. I read that this is quite regular place to fail, so is there anything I could do to fix it? Also, stock rods seem be on a fine line and I have problems searching for beefier parts. Seriously, SC28 can't be too old for aftermarket parts??

Is there something I could do to improve the oil flow, like gearing the pump to spin a bit faster? What about the oil strainer, I heard it can cause problems too? Mods to oil pan or other stock parts, aftermarket stuff etc, I'm all ears.

Thanks in advance guys!
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post #2 of 5 Old 08-27-2007, 11:31 PM
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Re: Turbo engine questions (SC28)

Is the engine stock with a turbo or has it been built from scratch for turbo work specifically? 300hp (measured at the crank or tyre?) is well over double the original designed power of around 125 at the crank. If you're measuring it at the tyre you're almost triple what the engine was designed for and it's probably running close to self-destruction anyway.
I've never built a 300hp bike motor myself but rod bearings usually fail because something else is wrong which throws out the bearing clearance disrupting its ability to soak heat away into the rod and then the bearing overheats and comes apart.
Assuming you are ensuring all clearances are spot on when you're building it (bearing crush is going to be critical in this engine) I can only suggest trying heavier rods. If you can't buy some you can certainly get some made to your own spec. The 893 is an old engine to begin with so I'd be _at least_ running brand new OEM rods with that sort of horespower. Boosting a motor by these sorts of percentages could cause any number of hard to sort problems. Even the cases themselves could be flexing when the plugs fire :-)
I'd be hesitant to increase pump speed by much due to possible cavitation but a higher-volume pump might be an option.
You could possibly drill an oil jet into a gallery and spray oil directly at the bigends to try to keep them cooler. Maybe also try a much deeper sump for more capacity and a bigger and/or additional cooler to cool the oil down as much as possible before putting it back into the engine. I'd also run an oil temperature sensor.
Are the rods or crank pins ovaling at all?
Are the insides of the engine blueing from excessive heat?
Under what circumstances are the bearings failing?

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Last edited by bladeracer; 08-27-2007 at 11:38 PM.
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post #3 of 5 Old 08-27-2007, 11:43 PM
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Re: Turbo engine questions (SC28)

Something else just occurred to me. With that sort of power your acceleration is going to be quite brisk :-)
Your oil may be running to the back of the engine every time you twist the throttle and starving the pickup. You might want to baffle the sump and modify the pickup to ensure it is always well covered in oil.

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post #4 of 5 Old 08-28-2007, 4:31 PM Thread Starter
 
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Re: Turbo engine questions (SC28)

Cylinders and head have been built with attention and it has a lockup clutch. Crank and conrods are stock. Dunno about horsepower, to my knowledge the guy who dynoed it uses rwhp numbers. A lot of power in either way

The rod bearing went at full throttle and high RPM. I got a hint from a guy who builds killer Busa's that bearings need to have a bit more clearance, otherwise they overheat and spin. Conrod failures have always been related to valve problems, but I am still tempted to try bigger rods. I am hoping they would help with bearing problems too, or would they?

I just eyeballed the oilpan for a long time, deepening it would quite a job.. Is there any guesses how low the oil surface goes at high RPM? Is it common for pump to run dry if oil level is on the low side?

I'll find out about crank bearing surfaces later, I'm going to take some parts to a machine shop tomorrow. They haven't overheated.

Looks like all my oilpumps are shot, so I have to get a new pump anyway. Is there bigger volume pumps on the market? Also, any glues of aftermarket conrod manufacturers would help. Carrillo rods have been suggested somewhere, but Carrillo doesn't have SC28 rods in their catalog.
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post #5 of 5 Old 08-30-2007, 1:12 PM Thread Starter
 
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Re: Turbo engine questions (SC28)

OK, Falicon sells conrods. I still haven't found oilpump. What about bigger Blades, do they have bigger oilpump and if so, does it fit SC28?
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