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Measuring engine blowby

 
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skylinegtrhr



Joined: 14 Oct 2009
Posts: 51
Location: Croatia

PostPosted: Sun Oct 20, 2013 3:28 am    Post subject: Measuring engine blowby Reply with quote

Hi
we didn't do this still so can anyone point me in procedure or give any link about it?

I notice that some of You are using King Instruments blowby meters, so what type should be recommended for V6 3l engine (VG30DETT Z32 ) and what testing procedure should be (how much time , rpm etc) and of course what results should be good ( this engine has JE pistons 2618 with gap set for Circle Track / Drag Race spec) so that we know that rings breaking in is over .

Many thanks for any suggestion .
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Power-Tripp



Joined: 26 Nov 2008
Posts: 441
Location: Deep South, AL, USA

PostPosted: Wed Oct 23, 2013 9:13 am    Post subject: Reply with quote

Blow-by is for engine builders and break-in. It tells you how well the cylinders are sealed up. If you didn't build the engine, and tightly control everything related to ring seal, then it is not going to tell you anything worthwhile.

I have been using two different King flow meters (4 or 8 SCFM maximum, graduated in .25 SCFM) for close to two decades. Before then, I didn't have a clue as to how well cylinders were sealed up - I could only guess. With a flow meter, you will quickly see where you were wrong - and how wrong you were. I have been waiting for the Performance Trends digital unit to pick up RPM, it is close, but not quite right - http://performancetrends.com/Blowby_CFM_Flow_Sensor_Meter.htm

Test at WOT at peak torque rpm, as well as peak engine speed (for ring flutter). (If you can log blow-by with the Performance Trends unit, then things change.)

I have seen really good iron block 8L+ V8 engines show less than 1.5 SCFM. I have also seen them show 5 times this amount. The same goes with L4 engines or V-Twins. Keep good records for similar engines and work to get the least amount possible. Each .25 SCFM is harder to get, but pays bigger dividends. And stay away from detonation or all work is wasted.

The engine displacement, block and bore material, hone work, piston clearance, ring type/gap/seating, natural or forced induction, etc. all play into blow-by SCFM at a given engine speed and load. Without testing blow-by, you have no clue as to how well a given engine is sealed up via machining, parts selection, and break-in procedure.

Iron blocks are better than aluminum ones.
Steel sleeves are better than Nikasil.
A good hot hone job is immensely better than a normal performance hone job. This is even more important with aluminum blocks/sleeves than with iron.
Bore plates are a must.
Ring packages are far from the same.
Break-in is all about seating the rings.

I hope this helps.
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skylinegtrhr



Joined: 14 Oct 2009
Posts: 51
Location: Croatia

PostPosted: Wed Oct 23, 2013 1:34 pm    Post subject: Reply with quote

Many thanks for Yours advice and answer.
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Warpspeed



Joined: 05 Jun 2006
Posts: 549
Location: Melbourne

PostPosted: Wed Oct 23, 2013 3:02 pm    Post subject: Re: Measuring engine blowby Reply with quote

skylinegtrhr wrote:


I notice that some of You are using King Instruments blowby meters, so what type should be recommended for V6 3l engine (VG30DETT Z32 ) and what testing procedure .

On difficulty with turbo engines will be separating ring blowby from turbo blowby.
Both the compressor and turbine leak air into the centre bearing section when under boost, and what drains back into the sump is not just oil, but foam that contains a lot of air volume.

If you want to measure just the ring seal with your DETT engine, you will probably need to isolate the turbo oil drains from the sump for a very short period of time while you take a measurement.

There are simple gas flow meters used in industry (and medicine) that consist of a glass tube with a very slight taper, into which sits a plastic ball. Gas flow up the tube causes the ball to rise, and you can read gas flow directly from a vertical scale.
It's just a case of finding something with a suitable range which is commonly scaled in litres per minute.
http://img.alibaba.com/img/pb/678/436/377/377436678_620.jpg


Last edited by Warpspeed on Wed Oct 23, 2013 3:11 pm; edited 1 time in total
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nfn15037



Joined: 22 Dec 2005
Posts: 271
Location: New England

PostPosted: Wed Oct 23, 2013 3:06 pm    Post subject: Reply with quote

Power-Tripp wrote:
Blow-by is for engine builders and break-in. It tells you how well the cylinders are sealed up. If you didn't build the engine, and tightly control everything related to ring seal, then it is not going to tell you anything worthwhile.

I have been using two different King flow meters (4 or 8 SCFM maximum, graduated in .25 SCFM) for close to two decades. Before then, I didn't have a clue as to how well cylinders were sealed up - I could only guess. With a flow meter, you will quickly see where you were wrong - and how wrong you were. I have been waiting for the Performance Trends digital unit to pick up RPM, it is close, but not quite right - http://performancetrends.com/Blowby_CFM_Flow_Sensor_Meter.htm

Test at WOT at peak torque rpm, as well as peak engine speed (for ring flutter). (If you can log blow-by with the Performance Trends unit, then things change.)

I have seen really good iron block 8L+ V8 engines show less than 1.5 SCFM. I have also seen them show 5 times this amount. The same goes with L4 engines or V-Twins. Keep good records for similar engines and work to get the least amount possible. Each .25 SCFM is harder to get, but pays bigger dividends. And stay away from detonation or all work is wasted.

The engine displacement, block and bore material, hone work, piston clearance, ring type/gap/seating, natural or forced induction, etc. all play into blow-by SCFM at a given engine speed and load. Without testing blow-by, you have no clue as to how well a given engine is sealed up via machining, parts selection, and break-in procedure.

Iron blocks are better than aluminum ones.
Steel sleeves are better than Nikasil.
A good hot hone job is immensely better than a normal performance hone job. This is even more important with aluminum blocks/sleeves than with iron.
Bore plates are a must.
Ring packages are far from the same.
Break-in is all about seating the rings.

I hope this helps.


Great info, thanks for sharing your experiences. One question though, how would one measure blowby flow on an engine with a dry sump? In the past, I have used a MAP sensor for crankcase pressure monitoring and for setting up the inlet orifice. I will have to buy one of these sensors and experiment.
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