Getting 10psi Boost on a NA engine...

[LETZRIDE]

So, how many of you guys are familiar with designing manifolds? In all seriousness, I have been reading about designing them and tunning them...apparently it is possible to actually get up to 10 psi boost on a NA engine through intake manifold tunning. Apparently, the way I understand it is: The air waves coming into the cylinders are similar to sound waves or water waves, in the way in which they will amplify each other when they collide. If you tune the intake runners so that this wave hits just as the intake valve is closing, rushes back, then gets hit with the next wave of air coming down...it forces air into the cylinder as the intake valves opens up.

The trick is getting the air to be forced in at some point when that intake valve is open...


By doing this, you are getting the volumetric efficieny to over 100%...

The only thing is, you'll only get this boost for a limited about of rpm range...


Discuss...and I want a good technical discussion...I don't fully understand the concept yet, I am still reading about it...I'd like to learn a little more about this...

[97rs4life]

Re: Getting 10psi Boost on a NA engine...

not sure how you can get boost if nothing is pushing the air in. An engine sucks air in no matter the intake, something would need to be pushing the air to see boost numbers. Velocity can be changed due to the intake and can be higher with different designs, but you are not pushing air when NA.

I am not getting this boost idea I guess that you are thinking of. Just don't see how it is possible

[venom3300]

Re: Getting 10psi Boost on a NA engine...

sounds like u need an engineering degree to even know where to start on making this work.... and im not sure i would call it "boost"

also i dont think air moves in waves, i think you can change velocity with different angles/openings to produce a more efficient intake.

[LETZRIDE]

Re: Getting 10psi Boost on a NA engine...

well...I was reading it in a tunning book...I'll nab the name of it tommorrow incase anyone might be interested...I might not be fully explaining it that well...since like I said, I don't fully undertand it myself...

But from what I am getting, the overlap in your cam would create a positive and negative pressure... there are a bunch of calculations I'll post up tommorrow for intake runner length etc...it all plays a key role.

but the positive and negative pressure create somewhat of vacuum...there was something about getting an extra rush of air through the exhaust valve and it going through the intake valve...as well as this extra wave of air being forced in...

I know that you have to tune the manifold through resonation in order to make it happen...since you intake valve is open only for a fraction of a second...the rush of air has to be timed for that exact opening, or a portion of the opening.

I'll post a bit more on it tommorrow as I read a bit further...I'll have the book infront of me to, so I can maybe relay the info a bit better...

This is not for the stock manifold btw...this is you would have to build your own, with different size intake runners/plenums to make this work...

[Fondle]

Re: Getting 10psi Boost on a NA engine...

it seems like if this was possible it would have been done before, but hats off to you for trying this if you do

[97rs4life]

Re: Getting 10psi Boost on a NA engine...

yea get the name of the book for us if you could. I already been playing with intakes as I am running the holden intake on my car now. Curious to see what they are trying to get at.

I think your boost terminalogy may be the incorrect word to describe what you are researching though.

[RadRacer]

Re: Getting 10psi Boost on a NA engine...

Definitely possible, but the amount of research, work, and the fact that just the slightest build up of carbon or grime would negate the effects are probably the reason why it's not being widely used.

[LETZRIDE]

Re: Getting 10psi Boost on a NA engine...

it seems like if this was possible it would have been done before, but hats off to you for trying this if you do

Apparently it is used on alot of "high-reving" race cars...it is possible to get it for a car that only turns 5000rpm according to the book...its just a very small band...so you could get "up to" 10 psi (depending on how well you set this up) from maybe 5000-6000 or 6500 for us... small band yes, but none the less...would be a fairly nice power boost. Plus, I know when I am racing, because of the stall, I stay at 5000rpm or higher...

I think your boost terminalogy may be the incorrect word to describe what you are researching though

They say 10psi above atmospheric pressure... I assumed that was boost?

Apparently there is a video somewhere of some supercar running N/A with a boost gauge on the salt flats, and it shows it hitting 10psi. I haven't seen or been able to find the video, so don't hold me to that...

Just throwing out some interesting info I've come across and trying to get a better understanding of it...To me I can kinda see how this could work...only because I picture something similar to sound waves amplifying each other...
Plus, this seems like a pretty credible book...I'll try and get some more/clearer info tommorrow...

[Cammy98]

Re: Getting 10psi Boost on a NA engine...

im also very interested to see this as well.

Water waves, sound waves, and gas(atmospheric air) waves all act very differently. water and sound need a source, and we all heard of pressurizing water and amplifying sound however those two need a source. Air is all around us I cant imagine an engine (which only acts like a vacuum due to the combustion process) forcing more air in without external assistance.

[ssms5411]

Re: Getting 10psi Boost on a NA engine...

We are always a 14.7 atmospheric pressure some altitudes less or more, the only way to create PSI is something forcing more air in to the intakes and cylinders. A cam changes the lift and how much air flow is going into the combustion but still it just sucks air in being N/A and no positive air is moving since nothing is pressurized. If you change the vacuum down too much the car won't run , stock is like 18-22 vac, with my cam it is 16-18 vac, when you get down to like 10 your car won' t be starting. Guys with big drag cams can use a Vac. pump to keep the vac. down to where it will run. Our cars have a vac. canister next to the horns under the battery.

[auto666]

Re: Getting 10psi Boost on a NA engine...

i believe hes refering to resonance tuning you can do this for the intake and exhaust "boost" is not what you get but the air does flow in pulses in an engine and if you make your runners the right diameter and length for the rpm you want max power at you will get a significant boost in power there how ever only there and depending on what rpm and the specifics of you design you can acctually hurt power through revision else where in the power band most engines are designed with the intake tuned at peak hp while the exhaust is tuned to peak tq doing this helps to smooth out the power band and give you a nice flat tq curve

[auto666]

Re: Getting 10psi Boost on a NA engine...

just a bit more; to do this properly takes an extreme amount of work and calculation everything is important in figuring out the math from the lift and duration of the cam to the quench of the combustion chamber and compression ratio, valve size, port diameter everything!

[auto666]

Re: Getting 10psi Boost on a NA engine...

We are always a 14.7 atmospheric pressure some altitudes less or more, the only way to create PSI is something forcing more air in to the intakes and cylinders. A cam changes the lift and how much air flow is going into the combustion but still it just sucks air in being N/A and no positive air is moving since nothing is pressurized. If you change the vacuum down too much the car won't run , stock is like 18-22 vac, with my cam it is 16-18 vac, when you get down to like 10 your car won' t be starting. Guys with big drag cams can use a Vac. pump to keep the vac. down to where it will run. Our cars have a vac. canister next to the horns under the battery.

you have a mass air sensor you could remove you map and start it with 10 psi in the intake as long as you fuel and map curves are good for it. with that said old school carbed application need a certain amount of vacuum to run propperly or the carb wont be providing the propper a/f ratios to run

edit: hince idles of 2000rpm+ on raced out carbed engines

[flamingchicken]

Re: Getting 10psi Boost on a NA engine...

We are always a 14.7 atmospheric pressure some altitudes less or more, the only way to create PSI is something forcing more air in to the intakes and cylinders. A cam changes the lift and how much air flow is going into the combustion but still it just sucks air in being N/A and no positive air is moving since nothing is pressurized. If you change the vacuum down too much the car won't run , stock is like 18-22 vac, with my cam it is 16-18 vac, when you get down to like 10 your car won' t be starting. Guys with big drag cams can use a Vac. pump to keep the vac. down to where it will run. Our cars have a vac. canister next to the horns under the battery.

i think the vacuum pump you are refering to is actually used to lower crankcase pressures for increased performance.

as far as the vacuum goes that "is required" for the car to run, as long as the sensors are getting proper readings, (IE-air is going to still be sucked in at a certain volume past the maf sensor) then the air that is acutally at the intake port can be whatever pressure it wants, to a certain extent, because fuel will need to be matched to the volume of air in the cylinder for a proper burn (not too rich, not too lean)

I have always wanted to figure out some sort of "air injection" system that can be installed in the intake ports to, basically, inject bursts of air that will lower the drag on the piston caused by the resistance of air to flow.

I can see how intake tuning can result in better flow, but as for waves created by air, i just cant wrap my brain around it.

[LETZRIDE]

Re: Getting 10psi Boost on a NA engine...

Ok, the name of the book is "Motorbooks Workshop: How to tune and modify engine management sytems" Its by Jeff Hartman...has a ems computer screen on the front behind a ford focus.

The stuff which I am talking about is Chapter 12 and runs from page 116 to 121

So, lets see if I can explain this a tad better using the book...

as the exhaust valve opens "an acoustic pulse (+) goes down the pipe at the speed of sound." This wave will go on to enter the atmosphere and trigger a negative pressure wave that travels back up the pipe. The low pressure waves that you get (if you have tuned it right) will help to suck out the last of the exhaust gas.

The wave also contines to travel up the intake port and into the tuned intake manifold runner where it again meets the atmosphere.

"At this point the powerful wave is once again reflected back as the positive pressure wave traveling back down the intake runner. If the length is correct, the remianing energy is expended, propelling extra charge into the combustion chamber just as the intake valve closes.

Power increases are commensurate with multi-psi positive boost pressure."

Now it goes on to say that this would be for a very narrow band...for instance, our cars would only get this from maybe 5000-6000 or 6500 rpm... which is great if you have a stall converter and racing, because you will be up at that rpm all the time just about...

It also goes on to mention that you should be tapering the intake ports to help increase velocity and such...

I got to read this over another couple times atleast, I'm still trying to understand it myself...I probably shouldn't of tried to explain it as sound waves earlier either, I was just trying to convey how I'm kind of comprehending whats going on. Sound and water waves are just what I associated this with, and with whats going on...sorry if that confused anyone...