Cobalt60 Posted June 17, 2009 Report Share Posted June 17, 2009 I believe the problem is due to the fact that the heads are aluminum, and the valves are steel. So I was thinking, maybe the valves are a simple enough design so that custom aluminum ones could be fabricated. This could eliminate any problems caused by the jet valves, while maintaining whatever benefits they have. So the first question would be, is this really feasible? And the second would be, would this work well if the regular valves were replaced with over sized ones? -Chris P Link to comment Share on other sites More sharing options...
strang3majik Posted June 17, 2009 Report Share Posted June 17, 2009 the jetvalves are an emmisions thing. Nothing else....so, there really is no gain or loss to having them or not. Just sounds to me like too much work...lol Link to comment Share on other sites More sharing options...
86TSiGuy Posted June 17, 2009 Report Share Posted June 17, 2009 Is there not some positive effect on fuel efficiency even if considered minor or insignificant. Link to comment Share on other sites More sharing options...
Cobalt60 Posted June 17, 2009 Author Report Share Posted June 17, 2009 So you dont feel that jet valves can help produce more power? Arent the factory horsepower ratings higher for jet valve equipped heads than for non? The jet valves create a swirl effect of the mixture, promoting a better burn. This should at least to some degree improve fuel efficiency and power. Link to comment Share on other sites More sharing options...
PDX87Starion Posted June 17, 2009 Report Share Posted June 17, 2009 If you want to run jet valves... just run them stock. There are many jet valve cars with over 100,000 miles on them with no problems. If your looking for a little more performance...run 1psi more. Thats how we do it with turbo cars. I have had many NA cars and racecars and the thing is with NA cars you have to do 100's of those little things to get more performance. With a turbo, one psi is worth more power than all those little things combined. No need to waist time and money trying to improve the jet valve for more performance. They had no effect on the HP ratings... all the SQ's had JV's, power increased when they upped the boost to 10psi in '88. I'm sure there are ways to improve the egr system too... but why? just use it as is, or eliminate it. Spend time perfecting the timing and A/F for the boost you are running, and you will see much higher gains than messing with the JV's. Link to comment Share on other sites More sharing options...
slydogg Posted June 17, 2009 Report Share Posted June 17, 2009 new jet valves are great, 20 + year old jet valves are not. Link to comment Share on other sites More sharing options...
86TSiGuy Posted June 17, 2009 Report Share Posted June 17, 2009 I believe the primary issue with the jet valves and the most common reason for removal, is that they retain a significant amount of heat from previous cycles, this in turn heat's your incoming air/fuel charge as well as transfers to the head. Perhaps if you fabbed them out of aluminum with a shorter shroud this side effect could be made negligible. Link to comment Share on other sites More sharing options...
Indiana Posted June 17, 2009 Report Share Posted June 17, 2009 (edited) Jet valves run cooler than your exhaust valves. There is no flame traveling through a jet valve. Only cool air enters a jet valve. The jet valves are in the casting that is cooled by the engine coolant same as the rest of the head. The problem isn't that they are steel that's just silly. The problem is when they are neglected and get crusty and stick open. There was some moron on this video above japclassics with quite a few errors in his information and his assumptions were that high boost blows them open. I guess that moron has a motor with no compression as jet valves are only opened when the intake valves are open and that even if they think they are slow the close any compression at all in the cylinders which at just cranking rpms is over 100psi will force them closed. Its when they are stuck open or the screws in the rocker arms come loose and prevent them from closing that there is issues with lean cylinders. If they can stick open that means that duh no air can flow through them either so how does that lean out the cylinder anyway? They can BREAK OFF and that is the big problem. Why do heads crack? Well how many heat cycles does it take a piece or aluminum that is about 1/4" wide x1/4" tall and 3/4" long long to get a crack in it when its right in the center of the combustion chamber and in between the cool incoming air charge through the intake valve and passing out the super heated gases through the exhaust valve in motors that detonate and run extremely hot? Apparently not very many in some cases but it didn't have anything at all to do with a jet valve most times. They get blamed for everything just like balance shafts when its all the owners fault for poor maintenance. It you want to clean them here's what they look like. http://www.b2600turbo.com/jet_valves.htm If you think there was no benefit to the swirl effect then what is a high swirl head and why would anyone at all even want one? Hint #1: Google turbo and high swirl head and see what you find. Hint #2: the GenIII TS Magna uses a high swirl head and piston but maybe only a couple people have figured this out. There needs to be a forged piston made to use in place of those n/a pistons and if there is an aftermarket source for that head we should be using it, that would mean no more modding the Magna intakes rear water port either because a pipe could be made to route coolant from the back it just needs a J turn. and that all started with jet valves and now every one is using balance shafts in 4cyl engines aren't they? Maybe they will use jet valves once again some day who knows Edited June 17, 2009 by Indiana Link to comment Share on other sites More sharing options...
86TSiGuy Posted June 17, 2009 Report Share Posted June 17, 2009 So the issue with the 12v head is that the jet valve contributes to thermal fractures in the casting? And this is due to the jet valve being cooled at a different rate than the head itself? Aside from failing to close which is a fixable design issue. Link to comment Share on other sites More sharing options...
Bill Hincher Posted June 17, 2009 Report Share Posted June 17, 2009 I have never seen such hog wash, ( not you guys but Mitsubishi) well maybe once, when Honda came out with their CVCC in 1975 ( controled vortex combustion chamber for you Mits guys) they stated that the small inlet valve opened just before the cylinder fired and that created a swirl ( vortex) in the cylinder well, that would mean that the inlet valve would have to open while the cylinder was in compression the truth was that the small inlet valve was put into the head to aviod using high enegy ignitions on lean engines before emmissions the proper fuel air ratio was 12.5 to 1 because emmission rules required a 14.5 to 1 ratio you had to have a better burn for the lean mixture think of it this way, early engines with ignition points and condensers needed the choke on cold engines because it grouped the fuel molicules in a denser pattern so it could run before the cylinder head had enough heat built into it to burn the leaner mixture that was switched to when the choke came off well, when the manufacturers went to the 14.5 to 1 ratio's they had to burn this much leaner mixtures and what they did was use the spark plug to fire the small rich mixture from the small inlet valve that in turn would burn the leaner mixture brought in by the main inlet valve completely, it was a chain reaction of fuel molicules being burned at a rapid pace what in the world would the engineers need to seperate lean air inlet from the main inlet valve mixture for? it makes no sense, its just a substitute for a high energy ignition Link to comment Share on other sites More sharing options...
Cobalt60 Posted June 18, 2009 Author Report Share Posted June 18, 2009 http://www.jsae.or.jp/autotech/data_e/9-9e.html http://www.sae.org/technical/papers/780007 http://www.adclassix.com/a3/78mitsubishiengines.html "...MCA-JET system, essentially a third “jet†valve in the combustion chamber that opened with the intake valve to feed a very lean mixture of fuel and air into the combustion chamber when the engine was at low speed with the throttle nearly closed. This leaned the fuel-air mixture and caused more swirling in the combustion chamber for better burning and gas mileage. At higher engine speeds, air going through the jet valve moved slower (it went faster than the speed of sound at idle) and normal combustion took place." Link to comment Share on other sites More sharing options...
PDX87Starion Posted June 18, 2009 Report Share Posted June 18, 2009 Yeah so if you want a cleaner burn and better mileage at cruise keep them, but there is no need to try and re-design them to work better or longer. A new or re-man stock jet valve head put on today will outlast about a 100 other 22 year old parts. Most people get rid off them because they feel they aren't needed and its easyer to get rid of them than to make sure they are working 100%. You can also get better mileage by driving slower and have cleaner emissions by having two or more brand new catalytic converters. But whats the point in that? These cars 4 cylinder muscle cars, not econoboxes. Link to comment Share on other sites More sharing options...
86TSiGuy Posted June 18, 2009 Report Share Posted June 18, 2009 For me the whole point to a 4 cylinder muscle car IS getting better fuel efficiency than an 8 cylinder muscle car... Link to comment Share on other sites More sharing options...
Maxzillian Posted June 18, 2009 Report Share Posted June 18, 2009 I thought about it a number of times, but felt I could only gain 1-2 mpg. Seeing as how my car is leaned more towards toy, I settled on the more robust (and cheaper!) non jet valve head. Link to comment Share on other sites More sharing options...
Indiana Posted June 18, 2009 Report Share Posted June 18, 2009 But you are missing something here, there was no reason to put a jet valve head on the turbo motor. The carbureted intake manifold had AIR going to the jet valve but the turbo motor has air AND fuel going into the cylidners and no what ever that comment about 12v and jet valves doing what ever that isn't true. You look at all those "non" jet heads and everyone of them is from the same casting that the jet valve head is from just they didn't bore out a hole and put in the valve. So this is Hog Wash? ok if you say so, no there are already too many assumptions about this motor that have been passed around far too long. You've seen videos of the inside of the combustion chamber haven't you? You see the air entering the cylinder past the valves and how it behaves and think that there is no use hitting it from the side with a small directed stream of air will do nothing? Its right beside the spark plug, actually helps cool the plug too. http://www.b2600turbo.com/images/stockjetvalves.jpg http://www.b2600turbo.com/images/stockjetvalves01.jpg http://www.b2600turbo.com/images/stockjetvalves02.jpg Hummm now where is the jet valve passage in the throttlebody? Its not the same purpose at all for the "lean" part in a turbo motor because its mixed with fuel because its down in the large chamber after the throttleplate and is a tube that runs over to the head and feeds through the same passage cause its the same head a carbureted motor uses. So saying that it leans out cylinders in a turbo motor is really false its just that if they stick open the motor runs like crap and you can bet htat's not the only issue with the motor at that point, like dirty injectors and raw fuel laying in the intake and that passage clogged. http://www.b2600turbo.com/misc%20gallery/injmixer.jpg The small hole by each port leads into that bore the jet valve goes in to. That curved cutout in the intake flange is where all the jet valve air flows. How many morons do you suppose that love RTV put that on intake manifold gaskets and have those half clogged up and blame rich and lean conditions on such BS as the intake design? TOO MANY http://www.b2600turbo.com/images/IM000469.JPG That opening at the top near the runner for #2 is where the jet valve air/fuel mix enter that path way in from the turbo intake manifold. That lower slightly larger opening is the EGR passage and if you want to know how the #2 and #3 may runner hotter than you should blame that pathway of exhaust gas that runs back through the head over to the intake for the EGR to use NOT jet valves. http://www.b2600turbo.com/images/IM002341.JPG If I don't have it backwards, that one on the left is EGR and the other in the jet valve passage and that's a cut away of the middle of the intake manifold where the throttlebody bolts on http://www.b2600turbo.com/images/IM002332.JPG This is the underside of the intake, the upper tube is the EGR and the one behind and just below it is the jet valve passage http://www.b2600turbo.com/images/IM002340.JPG It won't matter anyway nobody is going to start believing that jet valves are going to help do anything. Some moron 25 years ago already decided they were crap and has been passing that around since and now everyone repeats it. Most all of what is passed around about this motor is from the trucks and the FWD models anyway and that started way before there ever was a Starion. Now add that up with the jet valves missing, the wrong spark plugs (yes you are mostly all using the wrong spark plug), a water jacket full of rust sediment and an over boosted motor with dying cooling fans and if a head gasket blows or the head is cracked someone always places the blame in a direction away from their self. Jet valves get the blame first don't they? Link to comment Share on other sites More sharing options...
patra_is_here Posted June 18, 2009 Report Share Posted June 18, 2009 i think jet valves are pretty awesome., combined with MPI i bet you could get many benefits. Link to comment Share on other sites More sharing options...
BrazilBoy Posted June 18, 2009 Report Share Posted June 18, 2009 But you are missing something here, there was no reason to put a jet valve head on the turbo motor. The carbureted intake manifold had AIR going to the jet valve but the turbo motor has air AND fuel going into the cylidners and no what ever that comment about 12v and jet valves doing what ever that isn't true. You look at all those "non" jet heads and everyone of them is from the same casting that the jet valve head is from just they didn't bore out a hole and put in the valve. So this is Hog Wash? ok if you say so, no there are already too many assumptions about this motor that have been passed around far too long. You've seen videos of the inside of the combustion chamber haven't you? You see the air entering the cylinder past the valves and how it behaves and think that there is no use hitting it from the side with a small directed stream of air will do nothing? Its right beside the spark plug, actually helps cool the plug too. http://www.b2600turbo.com/images/stockjetvalves.jpg http://www.b2600turbo.com/images/stockjetvalves01.jpg http://www.b2600turbo.com/images/stockjetvalves02.jpg Hummm now where is the jet valve passage in the throttlebody? Its not the same purpose at all for the "lean" part in a turbo motor because its mixed with fuel because its down in the large chamber after the throttleplate and is a tube that runs over to the head and feeds through the same passage cause its the same head a carbureted motor uses. So saying that it leans out cylinders in a turbo motor is really false its just that if they stick open the motor runs like crap and you can bet htat's not the only issue with the motor at that point, like dirty injectors and raw fuel laying in the intake and that passage clogged. http://www.b2600turbo.com/misc%20gallery/injmixer.jpg The small hole by each port leads into that bore the jet valve goes in to. That curved cutout in the intake flange is where all the jet valve air flows. How many morons do you suppose that love RTV put that on intake manifold gaskets and have those half clogged up and blame rich and lean conditions on such BS as the intake design? TOO MANY http://www.b2600turbo.com/images/IM000469.JPG That opening at the top near the runner for #2 is where the jet valve air/fuel mix enter that path way in from the turbo intake manifold. That lower slightly larger opening is the EGR passage and if you want to know how the #2 and #3 may runner hotter than you should blame that pathway of exhaust gas that runs back through the head over to the intake for the EGR to use NOT jet valves. http://www.b2600turbo.com/images/IM002341.JPG If I don't have it backwards, that one on the left is EGR and the other in the jet valve passage and that's a cut away of the middle of the intake manifold where the throttlebody bolts on http://www.b2600turbo.com/images/IM002332.JPG This is the underside of the intake, the upper tube is the EGR and the one behind and just below it is the jet valve passage http://www.b2600turbo.com/images/IM002340.JPG It won't matter anyway nobody is going to start believing that jet valves are going to help do anything. Some moron 25 years ago already decided they were crap and has been passing that around since and now everyone repeats it. Most all of what is passed around about this motor is from the trucks and the FWD models anyway and that started way before there ever was a Starion. Now add that up with the jet valves missing, the wrong spark plugs (yes you are mostly all using the wrong spark plug), a water jacket full of rust sediment and an over boosted motor with dying cooling fans and if a head gasket blows or the head is cracked someone always places the blame in a direction away from their self. Jet valves get the blame first don't they? Man after reading all that........I WANT MY JET VALVES BACK....... Link to comment Share on other sites More sharing options...
Bill Hincher Posted June 18, 2009 Report Share Posted June 18, 2009 look real close at your diagram you are telling me that the air inlet valve is creating a swirl in the POWER STROKE of the engine! that means the intake valve has to be OPEN when the cylinder is under pressure, it cant happen! the ONLY time the intake valve is open is on INTAKE stroke soooooooooooooooooooooooooo??????????????? what is the income fresh jet air gonna do??????????????????? is it gonna swirl on the pistons way down on the intake stroke and lay on top of the piston and swirl???????????????????? Link to comment Share on other sites More sharing options...
nathan89quest Posted June 18, 2009 Report Share Posted June 18, 2009 (edited) Wow, I never thought I'd read so many different opinions one jet valves. P.s. Mine were bad when I eliminated mine. 13 year of not running and one stuck. Edited June 18, 2009 by nathan89quest Link to comment Share on other sites More sharing options...
Maxzillian Posted June 18, 2009 Report Share Posted June 18, 2009 Bill: If you look at the diagrams, it shows the jet valve closed during the compression stroke. What it illustrates is that the "vortex" induced during the intake stroke continues during the compression stroke. Personally, I'd rather use the jet valve ports for something more useful... like direct injection! Link to comment Share on other sites More sharing options...
strang3majik Posted June 18, 2009 Report Share Posted June 18, 2009 the PO of my car decided it was neccesary to remove the jet valve studs from the rockers, but leave the valves in. Not sure if its bad to run it that way...but, has been for a while now. Also...just curious, but, if you put a non jet valve head on, with the stock intake....wouldn't it technically make some of the fuel/air get trapped in the jet valve passages, and cause uneven flow? So, in other words, decreasing performance? Link to comment Share on other sites More sharing options...
mikec Posted June 18, 2009 Report Share Posted June 18, 2009 "Swirl" happens when the intake valve is open and the piston is moving down, drawing it air+fuel mix. The angle of the intake port & piping is such that the air+fuel mix is "aimed" in the chamber such that it'll naturally circle around as those Mitsu diagrams posted by Indiana show. At low RPMs though there isn't much "suction" created by the downward moving piston so the air velocity is low... not a whole lot of mixing happens... so the heavy fuel molecules often condense/separate from the air mix. That leads to uneven combustion in the chamber - loss in MPG, loss in performance, horrible emissions. The jet valves introduce a second air stream to "stir the pot" basically - keeping the air+fuel mixed better for a better/cleaner burn. At higher RPMs the piston is sucking in air rapidly so the air+fuel stays mixed pretty well on its own. "Squish" is another term you'll hear/read about: that's when the piston is on the upstroke (compression stroke). Round crescent shaped cutouts in the piston and/or cyl head shove the air+fuel around to help mix it more. Various shapes have been tried over the years - that's one reason modern engines are more efficient and can run a higher compression ratio: they're better at keeping air+fuel mixed and getting a more consistent, more even, burn. Port fuel injection - i.e. mixing the fuel close to the piston, compared to mixing it well upstream in a carb or throttle body/injection mixer setup - helps because there is less time for the fuel to condense/separate in the first place. mike c. Link to comment Share on other sites More sharing options...
Bill Hincher Posted June 18, 2009 Report Share Posted June 18, 2009 the diagram shows the jet valve causes swirl on and during the compression and the power stroke, this is impossible if you read the description next to the diagram you will see a much different meaning in a carefully worded description saying its an air fuel mixture that comes into the inlet valve not just air ( we must not pay Honda royalties) the intake valve is only open during the intake stroke, the swirl motion would follow the piston down on intake and lay on top of the piston crown, which is a totally usless excersise so when the piston starts its compression stroke ( the cylce after the intake event) all your swirl is lost, the compression event alone will distort any swirl because its compressing the volume Its the shape and position of the piston, combustion chamber and spark plug that create swirl on the power stroke yes dummy intake valves are bad in a good cylinder, because on the intake down stroke, the piston can develop enough suction to draw it open and ingest unwanted air causing a lean condition Link to comment Share on other sites More sharing options...
slydogg Posted June 18, 2009 Report Share Posted June 18, 2009 i think we covered jet valves, now what spark plug should we all be installing? Link to comment Share on other sites More sharing options...
86TSiGuy Posted June 18, 2009 Report Share Posted June 18, 2009 i think we covered jet valves, now what spark plug should we all be installing? X2 Also, I like that this forum almost got a little heated over jet valves. My kind of people, tell you what. Link to comment Share on other sites More sharing options...
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