crank case pressure control
04-04-11, 07:41 AM
#26
Racing Rotary Since 1983
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"So can I use the PCV nipple on the filler neck and the factory vent nipple on my middle iron and run them both to a catch?"
perhaps i am misunderstanding you but...
the primary reason that oil catch cans get filled is they are only venting one side of the motor. if you vent both sides then you always have a unobstructed breather and therefore any crankcase pressure is free to vent so nothing will push the oil up and out.
the typical "vented" FD has a breather only on the driver's (left) side. great for left hand turns but worthless for right hand turns.
vent both sides. Mazda was righteous enough to even supply the vent hole for single turbo setups
also, cap the additional vent hole.
howard
perhaps i am misunderstanding you but...
the primary reason that oil catch cans get filled is they are only venting one side of the motor. if you vent both sides then you always have a unobstructed breather and therefore any crankcase pressure is free to vent so nothing will push the oil up and out.
the typical "vented" FD has a breather only on the driver's (left) side. great for left hand turns but worthless for right hand turns.
vent both sides. Mazda was righteous enough to even supply the vent hole for single turbo setups
also, cap the additional vent hole.
howard
04-04-11, 11:37 AM
#27
Mine just happened to be eliminated to begin with. It can easily be done without eliminating the OMP and has been done on another car since mine. I have also seen a breather line coming right out the front of the front cover about halfway up.
Venting the other side is especially easy on FD's or Cosmo engines as they can use the rear oil return line on those engines, of course only if they have gone with a single turbo setup.
Venting the other side is especially easy on FD's or Cosmo engines as they can use the rear oil return line on those engines, of course only if they have gone with a single turbo setup.
04-04-11, 11:47 AM
#28
No matter how simple the solution really is, people on this forum will continue to make a mountain from a molehill over this simple issue. What doesn't help either is guys who don't track their cars offering solutions to a problem they don't really understand or offer a real fix for.
Sure, they may have solved the problem when encountered on a dyno or doing straight-line pulls but that does not address the entire problem and certainly does not fix the issue under all circumstances.
For people who don't push their cars while cornering this may be fine but otherwise:
Vent the other side of the engine.
Sure, they may have solved the problem when encountered on a dyno or doing straight-line pulls but that does not address the entire problem and certainly does not fix the issue under all circumstances.
For people who don't push their cars while cornering this may be fine but otherwise:
Vent the other side of the engine.
04-05-11, 10:12 AM
#31
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Okay sounds easy enough. So just tap the block off plate for the rear oil return seem sthe easiest. Is there any way to use the block off plate for the OMP?
Yes the early ones did have a nipple on the middle irons. I questioned it the first time I seen it myself.
Yes the early ones did have a nipple on the middle irons. I questioned it the first time I seen it myself.
04-05-11, 04:34 PM
#32
Yup, vent both sides of the motor and it works perfect... after about 5 track events on R888's I have only accumulated about 2oz of oil.
I used an adapter similar to pic below for the unused rear oil drain, a 3/8" brass 90 degree barb fitting, 3/8" Goodyear fuel injection hose and a small Jazz catch can pictured below. One side of catch can goes to stock oil filler neck and the other side of the catch can goes to the fitting on the block. DONE!
(hose not connected in yet in this pic...)
I used an adapter similar to pic below for the unused rear oil drain, a 3/8" brass 90 degree barb fitting, 3/8" Goodyear fuel injection hose and a small Jazz catch can pictured below. One side of catch can goes to stock oil filler neck and the other side of the catch can goes to the fitting on the block. DONE!
(hose not connected in yet in this pic...)
04-06-11, 11:01 PM
#34
My.02. I actually think the rear turbo return line is a poor choice since all the oil sloshes towards the back under acceleration. Under acceleration your under boost for the most part. When this happens the oil is already filling the rear hole. Then you have the crank case pressure that forces the oil up the line to the catch can. I think if you simply move the turbo return to the rear and use the front return as the vent, you can possibly eliminate any of these filling problems. If oil can't reach a point of entry, it can't fill a line therefore working it's way to the catch can will be a non-issue.
04-19-11, 10:13 PM
#35
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My.02. I actually think the rear turbo return line is a poor choice since all the oil sloshes towards the back under acceleration. Under acceleration your under boost for the most part. When this happens the oil is already filling the rear hole. Then you have the crank case pressure that forces the oil up the line to the catch can. I think if you simply move the turbo return to the rear and use the front return as the vent, you can possibly eliminate any of these filling problems. If oil can't reach a point of entry, it can't fill a line therefore working it's way to the catch can will be a non-issue.
With your .02 cents added has anyone tried this method to see if it's worth running a longer drain line?
04-20-11, 06:55 AM
#36
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This seems like a great idea but due to the degree of difficulty and the limited space under there , I elected to use the rear port , after some testing I'll decide which I will stay with .
04-20-11, 10:23 AM
#37
My.02. I actually think the rear turbo return line is a poor choice since all the oil sloshes towards the back under acceleration. Under acceleration your under boost for the most part. When this happens the oil is already filling the rear hole. Then you have the crank case pressure that forces the oil up the line to the catch can. I think if you simply move the turbo return to the rear and use the front return as the vent, you can possibly eliminate any of these filling problems. If oil can't reach a point of entry, it can't fill a line therefore working it's way to the catch can will be a non-issue.
Guy
04-23-11, 08:15 AM
#38
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Hello all , I completed the install and there is no sign of oil anymore !!! thank you all for the great advice (as ususl!) I am now thinking of placing another vent line on the front cover , any more pics or write up of this mod would be greatly appreciated !!
Thanks again !!
Thanks again !!
05-03-11, 07:54 AM
#40
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Hello all , I completed the install and there is no sign of oil anymore !!! thank you all for the great advice (as ususl!) I am now thinking of placing another vent line on the front cover , any more pics or write up of this mod would be greatly appreciated !!
Thanks again !!
Thanks again !!
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