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allessence said:
It's not to reduce boost. It's to keep the engine rpms in a range that keeps boost avalible at an instant. The greater the load the more boost the turbo will produce. This is why if you are just idling the car and romp on the gas the boost doesn't really go anywhere once it reaches ambient.
Sorry, I didn't mean that it reduced boost. As you say, it creates a load that lets boost build up. But with a mitsu turbo theres not much need to do it, response at anything over 2500 rpm is decent, at 3k rpm its instant.
 

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Discussion Starter #82 (Edited)
Thats very interesting J;)

I actually understand the spring loaded behavior of air, its something I work with everyday as my co-work has a salad cream cheese addiction, every time he rips an air bomb my leg springs up his backside:lol:

I noticed that some Japanese cars use a resonator on the air intake side, I was confused at first and that it was a sound cancellation chamber to make the intake quiet.

Helmholtz resonators are all around us, the neck of a bottle, the hole in a guitar, the shape of roofs in Turko Russia and the middle east are all Helmholtz resonators without the vents.

The larger the chamber the weaker the damping affect is, the smaller the chamber the stiffer the air spring is which resists the flow, basically on the exhaust side I want to match the total system resonance, so there is no damping and no resistance or impedance to the thermal wave, sound wave or pressure wave.

I have taken care of the thermal wave as the manifold is stone cold and stays cool even in use, I can actually touch it after 5 minutes of use, the long high velocity jets make the turbo spool up faster than before, now I just have to take care of the pressure wave and sonic wave, I don't have my flange plate yet but I have all the 316 piping, it turning into a longer project.
 

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Discussion Starter #84
I wish I had the tubing and a port exhaust flange because I would make a pretty dame good header;)

The 316 piping is to make the turbo exhaust pipe, I need a little more VAS or volume in the first 3 feet of the piping, this makes the airs return or spring effect very weak on the impeller and the first order harmonic resonance will be around 350Hz almost matching the ports sonic signature.



The Harmonic wave bounces up and down and side to side all at once, this is actually called symmetric and asymmetric oscillations, I want to use these to help the sub mach wave behavior, the only problem is heated gas travels at different speeds from sound, its slower, sound travels faster in dense air or anything dense, just as sound travels faster under water or even faster in steel.

All the laws are still unbroken, conservation of energy and momentum, the only benefit is the resonance will assist the pressure wave forward but its the feedback that concerns me right now.

Its similar to a tuba as I will have a 5 inch oval bell mouth on the Turbo flange which will act like a defuser for the sonic wave and expansion wave, it will enter very easily but it can't return as simply, like reversing a mega phone, I have calculated that 16 feet of exhaust will give the correct system impedance, but the big problem is the exhausts open end, it has no baffle or projector, this creates radiation impedance, this open end of the pipe reverses the sound and some of the pressure 180 degrees back into the pipe, thats not what I want.

I must do some more reading to figure what I am trying to say and do, I can feel it, I just can't express it yet:lol:
 

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Discussion Starter #85
Those ATP Turbo people are so slowwwwwwww! How longs it been and I don't have anything! I paid them over a month ago, fookers.

Anyway I have an interesting update, after all my porting on the exhaust side I just put the old gasket on, I never even matched it, it totally slipped my mind:lol: , it must have placed more stress on the exhaust gasket as it blew two weeks ago, it sounds raspy now, I went and got a new Scan Tech exhaust gasket on Friday.

Look at the original gasket, you can see the carbon build up on the gasket from the larger port, I'm running as rich as a dog, my car always has done until yesterday, anyway look at the new gasket below.







The new gasket from Scantech is the exactly the same size as the boring work I did, if this gasket of for my 900 why is it bigger?

I phoned and asked the parts guys if they gave me the wrong gasket maybe for the NG900, he said it will work on all the Saab's manifolds, thats not what I asked him but I realised he didn't know anymore than was on his PC screen.

I can honestly say the turbo was faster on spool up after the boring work, well until I blew the gasket, I have been getting really bad MPG since then so I have been granny shifting, anyway I will trying and get this back on the car tonight, see what happens with no gasket interference.
 

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Very interesting thread... I know nothing about this stuff:eek:... spent the evening reading everything here & trying to get my head around it. Thanks especially 2 Jen... really given me a lot to think about.

Sha: those sound graphs very, very interesting. What software are you using to produce them, if I may ask? It occurs to me that somewhere out there must be simulation software to design/size/shape heads, ports, manifolds etc. Wondering if any engineers in our midsts have heard/seen such stuff... can this be done w/high end CAD software?.

Anyone know a resource for calculations used in this process? I'm thinking maybe they are bouncing around inside Jen's vast mental DB of knowledge. :lol:
 

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This just keeps getting better!
How accurate of a sound sig do ya need Sha?
I could Bolt down my Neuman U89, stick an inverer on the car and run a DAT machine on Jennifers backseat!...
If she'll let me:)
 

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jdmckay said:
Very interesting thread... I know nothing about this stuff:eek:... spent the evening reading everything here & trying to get my head around it. Thanks especially 2 Jen... really given me a lot to think about.

Sha: those sound graphs very, very interesting. What software are you using to produce them, if I may ask? It occurs to me that somewhere out there must be simulation software to design/size/shape heads, ports, manifolds etc. Wondering if any engineers in our midsts have heard/seen such stuff... can this be done w/high end CAD software?.

Anyone know a resource for calculations used in this process? I'm thinking maybe they are bouncing around inside Jen's vast mental DB of knowledge. :lol:
Sorry, I had the info around at some point. Puma racing probably has it.

The equations are esoteric. There is like 40 of them. for a NA engine you have ambient air temp. engine size, intake lenght size, port size, CR/air volume, plenum size/volume, temp as the air goes in, temp as the air stops at the intake valve. ETC.

Anyhooo. There are so many varibles it's usually the engine/head manufactures and aftermarket high performance parts makers (edlebrock, etc)
that try to use the equations to the best of their ability only to find the proto type they just spent thousands of money on doesn't flow any better than the one they all ready have on the shelf. This is where the knowledge of a good/long time tuner has it going on. He can take several results and compile the information to make a best guess hypothosis and end up with the results he was hoping for. The equations can be cool and create a starting point but with technology these days just about all the programs about gas flow/hydraulics/sound pulses/gas dynamics etc are done on computers.

This is one of the reasons I'm very curious as to Shadows work. It is like getting a huge 3D picture without having to design and fabricate it myself and still getting all the right info. Plus, it's cooler than ice on a hot summer day on the back of the neck.

The wave harmonics is really a neat tool. In regards to the exhaust pipe:
But, I thought you would want the harmonics/pulse to pull the exhaust energy out/down the exhaust pipe. So you'd be looking for a larger amplitude?

Once flow of a gas or liquid starts it contains enough kinetic energy to continue the pull of the gas/liquid behind it. (kind of like siphoning gas or another liquid) So, with the exhaust you would want a large downpipe exhaust (3") and then smaller once the exhaust reaches a certain temperature since the gas desity (sound wave) is related to temperature. So above the rear axle a 2.5" pipe will technically be flowing (250F)almost the same gas volume as the 3" pipe at 1500F.

The harmonics of course would be ruined by the cat since it would act as a diffuser.
 

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scubasaab said:
This just keeps getting better!
How accurate of a sound sig do ya need Sha?
I could Bolt down my Neuman U89, stick an inverer on the car and run a DAT machine on Jennifers backseat!...
If she'll let me:)
I'd love to do something like that once I get all the bugs worked out. I'm still fiddling with my bov which as failed twice, and would really like to move up to Megasquirt but I don't even own a laptop. I have a pen tablet that runs Win95 but haven't found mega software that is compatible.

Also, I'd like to get my other mods done before any real time is spent with dyno/video time. Even though if I could get some kind of hook up to go to the VD camera for Boost, speed, rpm I'd go for it.

So, Shadowworks when are you going to get everything up and running so I can copy you? Hope, your feeling better and the eboli didn't make you lose any body parts.
 

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Discussion Starter #90
allessence said:
your feeling better and the eboli didn't make you lose any body parts.
The flu has sucked the life out of me, I had it 3 times in a month:(, my boss told me not to come back to work until its completely gone he quarantined me but was kind enough to gave me work to do in the house:lol:

Amplitude is irrelevant believe it or not, we do not want to increase it as that would convert mechanical energy into more sound energy, we want the least resistance which means no increase in amplitude also back boxes allow for so much expansion of gas and this is the main reducer of amplitude but is also the main cause of back pressure as the gas flow is disturbed by expansion and then compression through its output pipe.

I actually don't want a deep exhaust note as the ports do not make a deep sound, any depth in the sound from the exhaust port is from the surrounding air being pushed out the way lowering the frequency and the Doppler shift and this has a knock on affect until its to low to hear or not loud enough to hear, this means energy loss, to shift or compress a sound/frequency higher or lower than the original sound must phase shift, the shift absorbs more mechanical energy.

Everything has a natural resonance, a simplified example is, if you hold a rope in your hands and make waves in it, the longer waves in the rope makes it feels very heavy as your lifting the rope and bring it back down, your input is large, if you make lots fast waves it will be heavy again as more energy is required to maintain the number of waves, now there is a certain number of waves in a length of rope that matches its resonance and this is when the rope feel very light almost weightless.

The frequency of waves that make the rope feel super light will be its natural resonance, half of it's weight goes up and the other half goes down making it almost weightless, it requires very little energy to maintain this resonance as impedance is always super lower at system resonance.

The above example is what I'm trying to do with my exhaust, I want the exhaust system to become a self excitation tube of the engines resonance, the only problem is I can't do any of this work until I get the turbo plate and gasket back on, I hope I can get this done in the next two weeks.
 

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Oh, I perfectly understand the rope mechanics. Makes perfect sense.

Would every system(engine/components) be different?

I wouldn't have a clue of where or how to start something of this magnetude. Can't wait for you results.

Thanks again. J

Sorry to here your still in the dumpster.
 

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Sha,
Won't the resonance of the exhaust system change as engine rpm changes. I'm guessing that since the frequency of the engine pitch changes with RPM (kind of like a tone generator) if you want that perfect in phase, additive effect, you'd have to change the length of the exhaust piping as rpm changes. Like when you run a tone generator through a set of drivers and place them apart at a distance that either makes them silent (perfectly out of phase) or twice as loud (fully in phase)...
I think I need a hit of windowpane to figure this out!:cool:
I haven't built a control room in about 10 years, so my brain is math impaired!;oops:
 

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Discussion Starter #93 (Edited)
allessence said:
Would every system(engine/components) be different?
Yes! your very right, every component has its own resonance because of its shape, density and mass, I just realised something on the back of your question;)

If the valve springs were resonance matched at certain speeds they would open and close almost by them selfs or with very little resistance to the cams, that would be great for fuel efficiency and power, that would probably need a computer controller to make the best use of such a spring as we would not be able to hold the engine speed with our foot when a computer could make it move up to the cycle spacing of the resonance was.

I can imagine an engine that would have power gaps and power spikes, lets say idle at 1000 rpm, then 1250rpm if that is one of the resonance frequencies, then 1500rpm, 1750rpm, 2000rpms and so on, not great for racing but great for power once in the groove.

Basically if we can make the atomic structure resonate a few things can happen, it can brake its bonds and fall apart like glass, the singing lady breaking glass does not break it by screaming, all she has to do it hit the right frequency and the glass would shatter into a fine dust

or

it becomes weightless due to some kind of scaler wave interference, its called the Hutchison effect IIRC but I actually believe it was know by Tesla almost 80 years ago, any objects mass is neutralized once in resonance so in theory you could lift anything no matter how heavy, if they could resonant the engine as a whole without making it fall apart all the metal parts would be weightless so in theory the combustion would have to be a few thousand percent more efficient:lol:

The smartest most efficient engine would be one that used a resonator and a stimulator, thats similar to what the polyphase electric motors are, which are 97% efficiency, something compression engines can only dream of.



You can see the cool little webpage that has the rope resonance model, you can change the amplitude and move the slidder around, this gives a basic idea about resonance and the picture below shows a few harmonic orders that can be had in an open pipe.

http://www.ngsir.netfirms.com/englishhtm/StatWave.htm

 

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Excellent, you are familiar with Tesla and his work and concepts.
What an amazing man eh?
I loved reading about all his work and it still twirls around in my brain all the time as I look at the world.
Funny you mention about my stirring your brain, because last night I was thinking about additive principles and shaking things apart.:lol:
What you say is right though and if we could figure a way to have ceertain frequencies locked into a computer for running at optimal performance options...
My head is spinning with ideas:eek:
Now I'll never sleep!!:lol:
Hey Sha,
Do you have trouble sleeping?
I often do as I am creating all sorts of things simultaneously in my mind and during the quiet hours as I try to sleep, it's much worse!;oops:
 

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allessence said:
Sorry, I had the info around at some point. Puma racing probably has it.

<snip>

Anyhooo. There are so many varibles it's usually the engine/head manufactures and aftermarket high performance parts makers (edlebrock, etc) that try to use the equations to the best of their ability only to find the proto type they just spent thousands of money on doesn't flow any better than the one they all ready have on the shelf. (...)
Are you sure of this, or just a guess? (Don't misunderstand, I'm not criticizing.)

I don't know any of this definitively. I am a programmer, however. Stuff I "model" is biz related, but I know a lot of guys who do the same for mechanical apps. I'm certain that software has been written to handle valve & manifold size/shape, expansion chamber, surface conditions etc etc. I just don't know if it's under lock & key in some GM tower, available to public in some form, or (???).

What makes it of interest to me... it seems acoustics are 2nd cause. 1st cause is ignition spark & subsequent expansion processes... these actions generate the acoustics. Ablility to CAD these shapes/surfaces seems very predictable to me, and given state of technology something beyond guesswork, I'm quite sure.

This guy built a pretty hot Astra GSi 16v MK3, and mentions use of CAD in designing his turbo (Lysholm 1600 twin-screw) setup, all the kinds of things discussed in this thread.

This is one of the reasons I'm very curious as to Shadows work. It is like getting a huge 3D picture without having to design and fabricate it myself and still getting all the right info.
I agree, it is cool and very intrepid. I also agree acoustics provide a usefull map. I'm not sure, however, it provides "all the right info". I suspect it provides only some-of-right-info. I also suspect it provides some reflections that may not point to baseline first cause(s).

And again, I'm not trying to be critical. This just makes sense to me.

I got a '91 2100 & turbo sitting in corner of garage, just getting my feet wet w/knowledge base to make decisions on how I want to rebuild it & w/what parts. My only experience rebuilding motors was w/'70s era motorcylces, a time preceeding computers. I'm hoping to arm myself w/more precise, reliable info this time around.

If I were to follow your suggested moniker (eg: girlwholikestogofast), mine would probably be: guywhousedtogofastandhasticketstoproveitbutnowwantsgoodlowendpoweronmountainroadsandsomedecentgasmileage. :cheesy:
 

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porting

I was reading about head porting and some guy was using jb weld glue and filling in spots... and he was against polishing...his theory was that roughness cause troubled air which atomized fuel better.
 

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At one time my first statement was true about spending tons of money on a design only to find it doesn't work any better than what's on the shelf. It still happens today. Look at the GM generation of SAAB engines. They have failures that would never had happened in a real saab engine. Bad pistons, oil/lube problems. sticking valves. etc.

Anyhow, even with all the technology out there for the most part once something is designed it usally has to start with someone having a clue as to what works and what doesn't since She/he is the one who is asked about and it's his/her knowledge that goes into the program.

Lets face it: Basics state, long runners better low end, short runners better top end. the pulse wave for the best response for a V4 is a joined pipe 104" from valve face. Hence Y pipe on single port heads, Dual port heads it's 18" for the dual to y and then seperate pipes all the way back. This was done by a formula. Like a said I don't have the formulas anymore. But this is from memory.

So, the wave harmonics are very important to power in a particular rpm range. There was a project engine that had varible exhaust header lengths and intake lengths, they found the by adjusting the lenghts of the intake or exhaust they could create power anywhere they wanted to but again it wasn't consitant over the entire range. So, they designed a continuously varible system of intake and exhaust headers, valve timing and they found the power band stayed much more constant at any rpm range. Was a prototype.

On the flip side of this they also designed a varible geometry transmission. Basically it only used like 2000rpms of engine power (max torque) and would stay in gear but the gear was varible in size. As max launch power was needed it simply became a very small drive gear large output gear. Once up to speed the gear would become very large and the output gear would become very small. Or is it the other way around. Anyhow, the engine is always in Max power. And completely varible so it's the transmission that changes size/shape and the rpms remain constant.

Theres serveral models out now and if memory serves are called CVT's. Constant varible transmissions.

The technology has been around since 1790 though with varible belt drives. Though physically changed by hand screw. By 1840's the unit was starting to use fly wieghts to have automatic adjustment. Of course it was the size of a VW.

anyhow, What Sha is talking about make great sense but the acoustics for the entire RPM range would have to me homogenized (for a lack of better words) to get the greatest benefit.

So, This is what I have learned. Which seems to be the most constitant information. Exhaust port size has lots to do with exhaust gas velocity, and sonic pulse. etc. When these things are changed so it where the max torque is and where the the turbo spools.

Sha, chime in? I'm still waiting for your results to clarify or nullify my info and to futher my education.
 
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