16v intake runner dimensions in 240

[fredde_vit_pv]

talking about drivability and short runners,is that whith single or individual flyers(spjäll)?

/Fredde

[Erland Cox]

Patrik menar trottlat, då funkar inte tuningen.

Erland

[Kadett4wd]

talking about drivability and short runners,is that whith single or individual flyers(spjäll)?

/Fredde

Anyone of them.. as long as you got under 1bar absolute pressure the temp and density is in an almost uncalculatable(word?) mode.
And in cruisemode in town, you almost never drive with W,O,T
Well,, at night? maybe when you´re working 'nightshift'.

Have you guys calculated this when under boost by the way?
all the parameters changes at boost to from what is was at 1bar absolute to new parameters with higher temp(not always) but higher density(speed of sound alters, it becomes faster and tune becomes higher in the same runner as the pulses are faster).

You can reach tune in unboosted area in 'lower' rpm and get engine to breathe harder, and by that spool turbo harder.
And when in boost the tune move upwards in rpm... win/win situation.

this is one part of why 'this' camshaft reaches higher rpm in boosted mode than unboosted.

And,, this phenomena is also used when tuning twostroke engines, you can alter speed of pulses in exhaust by alter the heat in the pipe with ignition.
By this you can retard ignition more than normal, to get engine to 'over rev' a bit to reach more topspeed.

[Kadett4wd]

And in individual throttles,, even more out of control.
as you got different pressures on frontside and backside of throttle inside the runner.

[HenrikGM]

Hi Kadett4wd

I think you have a good point.

Pulsetuning on WOT on NA is almost 100kpa abs always, so calculation of lenghts would work here.

Now, with a pressurised engine i will have from 25kpa to 300kpa(or even more).
So tuned lenght is probably allover the place, but in what range?

Most big turbos will make some 120-130kpa much earlier than they will make real boost.

Thought:
If i could hit tuned lenght at say 3000rpm with 130kpa intake pressure i could perhaps make the turbo spool to real boost faster.
On the other hand, some will argue that pulsetuning is of so little relevance below 6000rpm(due to too low speed?) that its not worth any effort to chase it. But then again, with 130kpa the air is more dense than NA, so maybe it works anyway?

Way too many ifs and perhapses....

The real question is more like how do you make sure the power band is wide, while keeping the top end powerfull.
Obviously all parts has to play carefully together. Much easier if it was only top end..

[Erland Cox]

With full open throttle there are huge gains in pulsetuning especially with turbos.
Untuned you get maybe 90% VE and with the right length you can achieve above 110%.
With 3 bars absolute that means from 270 to 330 %.

Erland

[Pacman]

talking about drivability and short runners,is that whith single or individual flyers(spjäll)?

/Fredde

Anyone of them.. as long as you got under 1bar absolute pressure the temp and density is in an almost uncalculatable(word?) mode.
And in cruisemode in town, you almost never drive with W,O,T
Well,, at night? maybe when you´re working 'nightshift'.

Have you guys calculated this when under boost by the way?
all the parameters changes at boost to from what is was at 1bar absolute to new parameters with higher temp(not always) but higher density(speed of sound alters, it becomes faster and tune becomes higher in the same runner as the pulses are faster).

You can reach tune in unboosted area in 'lower' rpm and get engine to breathe harder, and by that spool turbo harder.
And when in boost the tune move upwards in rpm... win/win situation.

this is one part of why 'this' camshaft reaches higher rpm in boosted mode than unboosted.

And,, this phenomena is also used when tuning twostroke engines, you can alter speed of pulses in exhaust by alter the heat in the pipe with ignition.
By this you can retard ignition more than normal, to get engine to 'over rev' a bit to reach more topspeed.

Och där har du tyvärr fel Kadett4wd!
Detta var nåt man trodde funkade på 70-talet. Sen dess har utvecklingen, teknologin och den fysikaliska förståelsen gått framåt. Läs på om ett fenomen som heter kompressibilitet som styr ljudhastigheten i luft.
Ljudhastigheten är INTE tryckberoende...men den är temperaturberoende.
Jag hade forskningspapper på det för några år sen när Erland och jag räknade mycket på insug. Erland satt några nätter och kokte ur innehållet i de rapporterna till nåt som var användbart för motorbyggen och det skrev han sen på sin hemsida.
Läs gärna där vad vi kom fram till: http://www.topplocksverkstan.se/fyrtaktsid2.html

[Kadett4wd]

hmm jag hade för mig jag skrev densitet...
ljudet går fortare i en hög dentistet.. exempelvis vatten.

[Pacman]

Ja ändrar man densiteten med t.ex bränsledimma så påverkas ljudhastigheten...men bara tryck gör det inte.

[Kadett4wd]

nej, men värmd eller kyld luft.. vilket ändras i samband med tryckändring av luft.

[Pacman]

Har du inte intercooler då?

[Erland Cox]

http://hyperphysics.phy-astr.gsu.edu/hb ... uspe3.html

Erland

[hauge]

tycker att det låter konstigt...(det går emot min intuition)

formeln som erland (han brukar ha rätt) hänvisar till ger intrycket av det som påstås.
Men den formeln förutsätter att den "adiabatiska konstanten", gamma är konstant oavsett tryck, vilket jag TROR den inte är.

En annan formel: http://www.engineeringtoolbox.com/speed-sound-d_82.html

Speed of Sound in Ideal Gases:
Since the acoustic disturbance introduced in a point is very small the heat transfer can be neglected and for gases assumed isentropic. For an isentropic process the ideal gas law can be used and the speed of sound can be expressed as
c = (k p / ρ)1/2
= (k R T)1/2 (3)
where
k = ratio of specific heats (adiabatic index)
p = pressure (Pa, psi)
R = gas constant
T = absolute temperature (oK, oR)

Denna formel tar hänsyn till trycket och enligt den är hastigheten tryckberoende


edit: faan: hittade en annan källa där det står att hastigheten inte är tryckberoende, annat än en gnutta pga att luft inte är en ideal gas.
Nu när jag skriver detta så kommer jag ihåg en annan tråd när vi diskuterade ljudhastighet/flöde i kanaler.
Det gällde ljudhastigheten/massflöde vid en strypning. Hastigeten kan inte bli högre än ljudhastighet, men densiteten ökar med ökande tryckdifferens, så man får ett ökat massflöde (men med ljudhastighet).

Alltså ljudhastigheten är inte beroende av trycket/densiteten (annat än en gnutta)

Hauge har gett sig

[Pacman]

Snubblade på detta när jag letade...
http://www2.mech.kth.se/courses/5C1201/ ... Sl-f12.pdf

Ganska tung läsning men en bit ner står det en hel del matnyttigt om ljudhastighet och Machtal.

[Kadett4wd]

Har du inte intercooler då?

Jo givetvis. Men tänk efter lite.
sällan du kommer ned till samma temp som ute.
om du har en luft/luft ic.
säg det är 20 grader ute och 40 i ingångsluften.
då blir det juh en 'dubblering' av värdet i formeln.
så svaret blir givetvis annorlunda.

edit: på den här sidan finns en enkel kalkylator: https://www.brisbanehotairballooning.co ... nsity.html