In situ measurement of swept volume 2

[SincoTC]

I have been asked by a colleague who is involved in club-level motor racing, if there is any instrumentation or method of measuring the swept volume of an engine cylinder "in situ", such that it can easily be carried out by a scrutineer, to see if it complies to the regulations without tearing the engine down?

I could only think of using a burette to introduce a benign light oil through a spark-plug hole at TDC until it spills, and then checking the amount added to spill at BDC, however, he wants to be able to check horizontally opposed engines too, so that rules that method out.

Any ideas? Thanks for any suggestions!

 

[drwebb]

"Cartridge starters were very common to start both piston and jet engines - but the pressure from the cartridge did not go into the engine's cylinder."

I never understood the tech details around that climactic scene in the 1965 "Flight of the Phoenix" until now. Much more effective than the equivalent in the 2004 remake. But I guess Jimmy Stewart had more experience than Dennis Quaid doing scenes where he was running out of bullets. Amazing the tidbits one picks up on this board . . .

 

[BigVlad]

Jimmy Stewart knew plenty about aeroplanes.

 

[SincoTC]

That's right, he flew B-24 Liberator bombers out of the UK during the War, nice luxurious plane by comparison to others of the time, electic nearly everything, including engine starting.

Trevor Clarke. (R & D) Scientific Instruments.Somerset. UK

SW2009x64 SP3.0 Intel Core i7 2.94Ghz, 12Gb Ram, NVIDIA Quadro FX3700 Driver: 6.14.11.8246
SW2009x64 SP3.0 Intel Core 2 Duo 3.17Ghz, 8Gb Ram NVIDIA Quadro FX3700 Driver: 6.14.11.8246

 

[thruthefence]

To clarify what I mean by the "motoring" incident I described, the prop made quite a few revolutions before the startled technician removed the air coupling from the plug adapter. Maybe it would have come to a stop on it's own, after the air pressure was removed. I know it scared the hell out of the guy doing the test, and as noted, could have easily killed someone.

 

[larrylcoyle]

thruthefence,

I hate to disagree but if you have ever tried to run a leak down test on a motor which is basically what you are describing here it will not work. All of the engines I have tested all stop at BDC and do not continuously spin as you suggest. Have you ever tried and substantiated this on a automotive performance engine?

Larry

Larry Coyle
Managing Partner
Cylinder Head Engineering, LLC
De Soto, KS 66018

 

[Compositepro]

Perhaps a compression release feature on the engine would allow motoring with compressed air.

Back to the original subject, I think that with appropriate tools it should be possible to simply measure the bore and stroke through the spark plug hole.

 

[SincoTC]

Hemi,
I like the plastic idea, but you'd still have to close off the valves at BDC. Also, if a matreial with the necessary properties already existed I'm sure Disney would have made a movie about it. It would be great stuff though!

Compositepro,
Depending on the position and orientation of the plug hole, measuring the stroke could often be achieved relatively easily. However, I feel that measuring the bore that way would be rather like a "ship in the bottle" trick, unless someone out there knows of some clever little ultrasonic or laser device that could do it?

 

[Lou Scannon]

Agreed, the valves would have to be closed at BDC. Depending on the engine, this would be more or less easy to do after removing the valve cover.

 

[patprimmer]

With cams acting directly on buckets, there is no way to disable valve opening without removing the cam drive or the cam. By removing the drive but not the cam you risk valve damage, especially on a race engine.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[thruthefence]

Larry, never on an automobile engine, however, I have a project coming up in my 'side business' this next month, where I plan on attempting the "motoring experiment" on a A TCM IO-550 aircraft engine, 6 cylinder, horizontally opposed, 550 CID. As I stated before, the air source was quickly removed ( in a state of panic, I'm sure ) and what I have described as 'motoring' could indeed have been the engine 'coasting down' AFTER the air source was removed.I was about 30 feet away from the incident, and sometimes eyewitness testimony is not really that accurate. One thing I am sure of, is that the engine in question spun 'with vigor' many times. It did not hit BDC & stop. Perhaps the technician, realizing his mistake pulled the coupling at the correct moment to allow the prop to spin over from inertia.

 

[HDS]

The techs in Formula SAE use a spring load bore gauge that goes in through the spark plug holes. Then it springs out and either touches the walls or doesn't. I think it is a standard meteorology tool. It was like an adjustable go/no-go gauge. Stroke is measured with a depth gauge that has spark plug threads on one end. The crank is then turned by hand from TDC to BDC. I think I have seen similar tools used in many other racing series. All very straight forward (no calculations more complicated than the volume of a cylinder).

The gas dispalcement type tests are clever but would indeed be made inaccurate by any leaks of the piston rings ect. They would also require everything to be at stable temperatures because any heat transfer to and from the gas would influence the pressures.

I have heard of all kinds of imaginative ways to cheat on such tests like having one cylinder smaller than the others. of course the side effects might be more trouble than they are worth....

 

[HDS]

I did some more searching and found timing gauges that are a dial indicator with a spark plug threaded bade. One thing they mention is that some spark plugs are at an angle and you need different adapters for them.