JMortensen Posted November 3, 2003 Share Posted November 3, 2003 I seem to vaguely remember a science project in 8th grade or so where we took a straw in a glass of water, and blew past the end of the straw with compressed air, and watched the water go up. I can't remember the name for it. I looked a bit on the internet, and the only effect I could find that I thought was even remotely similar was siphoning, but I don't think that that is the correct term for why this works. It's like the gas in a carb though. Think about your old SU's. Was there enough engine vacuum when you were driving to suck the gas out of the nozzles? If you stopped the air flow, and just put those carbs in a case filled with vacuum, would the gas fly out of them? No. What pulls the gas out of the nozzles is the air rushing by them and into the motor. There is no vacuum in your exhaust. There is velocity in the exhaust gas. It's counterintuitive, but this idea does work. I'm done trying to convince though. I'm just going to do it and let you all know what I think when its done. Probably have an update on that for everyone in the spring time when I drive the Z again. Jon Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 3, 2003 Share Posted November 3, 2003 Okay... one other point I'm confused about though How is there vacuum present in the exhaust manifold? I mean... to me it seems that the exhaust is always pressurized. So I would think that the exhaust would always be trying to push it's way back into the hose that tees off into the intake and exhaust' date=' and if there was a check valve there, it would just always be forced shut by the exhaust pressure... wouldn't it?[/quote'] Venturi effect. Quote Link to comment Share on other sites More sharing options...
TimZ Posted November 3, 2003 Share Posted November 3, 2003 Venturi effect. Close, but no bananna. Bernoulli's Principle. 8) Basically, a gas or fluid moving across a surface exerts decreasing pressure on the surface as it's velocity increases. And now, once again it's time for me to play Devil's Advocate. The Bernoulli argument is moot as far as connecting to the intake vs. exhaust, as it would apply in either location (air moves in the intake too), and the static pressure at the intake will almost certainly be lower than that in the exhaust. It doesn't matter if there is a 'vacuum' in the exhaust per se (or intake, for that matter), only that the pressure at the crankcase vent is lower than that inside the crankcase. Gasses and fluids ALWAYS flow from high pressure to lower pressure - they don't have a choice. I'd be very surprised if either of these setups were capable of generating lower than atmospheric pressures in the crankcase at WOT. The goal is just to get the pressure as low as possible. The crankcase definitely does generate high pressures, but I'm pretty sure that blowby gasses are the dominant effect, rather than the pistons moving up and down - as far as i can tell, this would tend to just shuttle the air around inside the crankcase, rather than compressing it appreciably. Also, as far as the resistance from air pressure argument goes, this assumes that the air is somehow pinned in place inside the crankcase and cannot move with the crank. Ganted there is most likely considerable turbulence in the crankcase which would add additional drag, but I doubt that the effect is all that severe. One advantage that I do see would be that this setup would probably still do a reasonable job of evacuating the crankcase, and would keep vaporzed oil out of the intake, which would be a plus. All that said, I do still pay attention to trying to keep the crankcase pressure as low as possible, but I am just a bit skeptical that connecting the vent to the exhaust vs a conventional vent to the intake will make any measurable difference, especially not 20hp. Maybe 20hp vs plugging the crankcase completely and letting it pressurize... Quote Link to comment Share on other sites More sharing options...
johnc Posted November 3, 2003 Share Posted November 3, 2003 With some of the more sophisticated windage setups in dry sump engines you do get close to sealing the crankcase into sections under each piston (or combination) between the crank throws. But, I seriously doubt anyone this board possesses such an engine. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 3, 2003 Share Posted November 3, 2003 Venturi effect. Close' date=' but no bananna. Bernoulli's Principle. 8) .[/quote'] I stand corrected ....but can I have my banana back anyways? Tim Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 3, 2003 Share Posted November 3, 2003 Duh. Thanks for pointing out my contradictory argument. Feeling a little stupid here... The few people I've talked to that have done this have said that it works, but they have claimed 20hp. I am not expecting to get that big an improvement, my gut tells me that is a little unrealistic. I agree that this is better than routing to the intake, since you aren't sending crankcase fumes and oily crap back into the intake manifold. Especially in a case like mine when running triples, where it is a PITA to route the PCV to every runner on the manifold. Jon Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 3, 2003 Share Posted November 3, 2003 So is it agreed then that this will give SOME improvement? I wasn't expecting 20hp either... I mean, my friend said he got this trick from guys who are driving pure race cars, probably with a lot more hp to begin with, and probably higher revving than my engine... so maybe for THEM it's worth 20hp. But... even if it's only worth a few hp at all... some noticeable improvement over just leaving the crank and valve cover breathers open to atmosphere (which is how mine is set up now) then I suppose it is worth doing. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 3, 2003 Share Posted November 3, 2003 TIM!!!! nice pic in your sig... the car done????? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 4, 2003 Share Posted November 4, 2003 TIM!!!! nice pic in your sig... the car done????? http://www.hybridz.org/phpBB2/viewtopic.php?t=27591&highlight= Quote Link to comment Share on other sites More sharing options...
TimZ Posted November 4, 2003 Share Posted November 4, 2003 Venturi effect. Close' date=' but no bananna. Bernoulli's Principle. 8) .[/quote'] I stand corrected ....but can I have my banana back anyways? Tim Seeing as how I spelled 'banana' wrong, I guess so... That is a nice pic, btw. Quote Link to comment Share on other sites More sharing options...
Thumper Posted November 4, 2003 Share Posted November 4, 2003 This sounds interesting but I am alittle confused on that I thought the pcv valve is a one way valve designed to not let air out. If that is the case then any tube connected on it would not be able to remove any air. But if this was put on the valve cover ventilation tube then it would work. So if you installed this you would run a tube, with a one way check valve letting no air go into the valve cover, to the exhaust manifold somewhere on the downpipe. How does this sound to you guys? Quote Link to comment Share on other sites More sharing options...
Guest BigWhyteDude Posted November 4, 2003 Share Posted November 4, 2003 the pcv valve is disigned to let air out but not let any back in it is a one way valve though PCV=Positive Crankcase Ventalation: meaning it vents to the outside atmosphere. Quote Link to comment Share on other sites More sharing options...
Thumper Posted November 4, 2003 Share Posted November 4, 2003 So the pcv stops air from going into the intake manifold but lets it come out of the crankcase. I new it would not let air out of the intake manifold. So u would cap that manifold off and run two hoses one off of the crankcase and the other off of the valve cover breather into a t then into the exhaust manifold. Basically what bastaad525 said awhile ago Thanks for explaining it for me. So who is going to try this first Let us know your results turn out even if its a butt dyno result. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 4, 2003 Share Posted November 4, 2003 Well I am soon to be a member of Jack Stand racing I think... I've got a bunch of stuff to do to my car. I'm definitely doing this, but you all probably won't get a report from me until spring. Also, looks like I am changing out my MSA header for a Nissan Comp unit, so I probably won't have anything like verifiable results... Jon Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 5, 2003 Share Posted November 5, 2003 Anyone got any recommendations as to what check valve to use or where to get a part like that? I dont want to buy that kit... this is something that I could easily do myself if I described the setup right. I just have to reopen the pipe that used to run to the EGR valve (had it welded shut) and run my hose to that... should do the trick, right? I'm also thinking of using a stock PCV valve as my check valve... Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted November 5, 2003 Share Posted November 5, 2003 Blow over the top of a straw that's inserted into a glass of water - the water will begin to rise up the straw if you do it right - that's how the suction is created. The engine picks up power because there's less pressure in the crankcase to fight when the pistons are coming down the bores etc.. I think if you peruse th eJegs catalog you'll even find a kit to do this - I've mostly seen it on circle track racers and whatnot, less so on drag cars <shrug> Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 5, 2003 Share Posted November 5, 2003 yeah... not gonna spend $$$ on a kit though when i can do it myself easily... unless there is something I'm missing??? Is there anything in that kit that makes it necessary/worth buying? I mean all I need are three hoses, a tee, and a one way valve right? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 5, 2003 Share Posted November 5, 2003 I think there is something to the shape of the "straw" piece that comes in the kit. I don't know that for sure, but it looks a lot like the tubes in a 4 bbl... BLKMGK, you must have come in on this topic a little late... Read back a little bit. I think I made all the same points almost word for word. Jon Quote Link to comment Share on other sites More sharing options...
Ron240zxt Posted November 5, 2003 Share Posted November 5, 2003 Hello, Just curious were you heard of this information from, Reason being there was talk about this around the shops in Chatsworth and just curious who might of mentioned this... Thanks Quote Link to comment Share on other sites More sharing options...
CruxGNZ Posted November 5, 2003 Share Posted November 5, 2003 Ron, This topic has been on two other websites that I know of at the same time as well. Seems to be a hot topic lately. !M! Quote Link to comment Share on other sites More sharing options...
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