max compreesion water injection
max compreesion water injection
(OP)
Trying to get some info. Normally aspirated 87 octane gasoline fueled engine 2 valve wedge chamber dedicted pure water injection. What is the upper limit mechanical compression ratio before detonation threshold. There's a lot been written for artificial aspirated aplications. Blair and Heywood cite some examples but don't seem offer any limit. Vizard reports 18:1 kerosene fueled lab engine. The consenses is that it works but I haven't been able to get my eyes on anything that suggests what # would be optimum. ------Phil





RE: max compreesion water injection
Deck clearance.
Chamber shape.
Chamber, valve and plug finish re surface and sharp edges.
Water circulation and temperature.
Piston top geometry and finish.
Cylinder head material.
Head gaskt fit.
Inlet valve closing pont.
Ignition timing.
VE
Exhaust back pressure and scavenging.
EGR
Valve material.
Oil temperatue.
Valve seat geometry.
Valve spring seat ressure.
Valve fit in guide.
Valve stem seal.
Ring seal.
Oil consumption.
A:F ratio.
Air and fuel distribution.
Air fuel mixture quality.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: max compreesion water injection
Look at this page:
http://www.rbracing-rsr.com/waterinjection.html
Have fun,
Russ
RE: max compreesion water injection
RE: max compreesion water injection
Can you start your tests with say 100 octane and see how much water you need and what park advance you can tolerate. That might save an engine and indicate if you can push further with the low octane.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers for professional engineers
RE: max compreesion water injection
RE: max compreesion water injection
Park advance should obviously be Spark advance. I hate this keyboard.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers for professional engineers
RE: max compreesion water injection
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: max compreesion water injection
Alin
RE: max compreesion water injection
RE: max compreesion water injection
Don't use manufacturer's published recommendations for anything but toilet paper.
Take for instance a traditional small block chevy, flat-top pistons, large-chamber smog heads, 8.5:1. You can run 87 octane all day every day. Swap to modern Vortec heads with smaller chambers, 9.5:1 compression, and still you can run 87 octane all day every day. The simple re-design of the chamber shape makes flame speeds much faster and you can use much less total ignition.
Factor in head alloy, piston configuration, EFI or carb, or any of the factors listed in patprimmer's post and the possibilities are endless. I recall reading an article about a high school shop class that built a chevy 502 with 12.5:1 compression, a 16:1 A/F ratio, and ran 87 octane with no detonation. It was all using a careful manipulation of the factors listed in patprimmer's post.
Sorry to be so vague, but there are just so many factors invovled that its hard to pinpoint. Give two builders the exact same set of parts and they will build two engines that have different detonation thresholds; cam ICL, ignition timing, quench height from the machine work involved, radiator efficiency... too much to predict
RE: max compreesion water injection