Blow Off Ventil i funkcije
Poslato: Ned Jan 13, 2013 7:11 pm
Sad cu da ispadnem glup a koja ce uloga blow off-a? Samo da sisti ili utice na perfomanse?
Forum Alfa Romeo klub Srbija
https://arcs.org.rs/forum/
kilson napisao:U kombinaciji sa map senzorom je ok jer map meri trenutni apsolutni pritisak u usisnoj grani i samim tim ECU momentalno odredjuje koliko goriva je potrebno. I pored toga, za standardne (fabricke) nadpritiske je suvisan i bolje je imati bypass ventil (ista stvar koja za razliku od BOV-a, visak pritiska vraca u granu ispred kompresorskog dela) ali ljudi vole da sikce...
Ako sam dobro skapirao blow of i bypass su slicna stvar samo sto bypass ima dodatnu ''cev" koja bi nazovimo visak vazduha vratila pre turbine u cilju da je ne koci pritisak vazduha koji nije prosao zbog zatvorenog leptira? Da li bi ovo mogao da bude upgrade koji bih rasteretio turbinu?Dora napisao:To je sekundarna misija i posledice jesu te što si napisao ali su minorne. Primarna misija je da spreči "naduvavanje" turbine kad se pusti gas. Kod punog gasa sve ide u jednom pravcu, prema motoru, kad se naglo zatvori leptir onda nastaje problem, vazduh koji je krenuo naleti na zid i vraća se nazad i stvara se prevelik pritisak u tom delu koji zaustavlja turbinu, "koči je", što predstavlja problem kad se odmah zatim dodaje ponovo gasa a turbini treba dva dana da se zaleti.
A blow-off valve is designed to prevent compressor surge on turbo-charged engines. Compressor Surge occurs when the engine's THROTTLE PLATE is suddenly closed, giving the Charge from the Turbo compressor, no where to go. So the blow-off is plumbed in somewhere between the Compressor's outlet and the Engine's Throttle body, allow unwanted Boost Pressure to be vented to Atmosphere or Intake stream before Compressor inlet. So, that being said, it should be obvious why most modern Turbo-charged, direct-injected Diesel Engines would have no need for a "blow off valve". A diesel engine is controlled by fuel, thus not requiring it to have a "intake air throttle plate". In a diesel engine, all mixing of FUEL/AIR occurs in the Combustion Chamber, by design the Diesel operates in EXCESS AIR situations, it can pump up to 600X times more air than it needs @ low idle. A Diesel builds peak power and Manifold Boost when UNDER-LOAD, so when you cut fuel to that engine while under load, the Manifold boost still has a place to go since the engine is still pumping air. The manifold boost tends to drop off quickly since it is being displaced by the cylinders, and since the turbine drive pressure will be less as well. This is why diesels provide higher levels of engine braking over petrol/gas engines as the amount of air to be compressed is still the same as if the engine was running at full speed and Jake brakes and other compression braking systems raise the engine braking performance even higher again.
Exceptions Occur
A few diesel engines of the past few years have used a throttle plate, mainly as part of some solutions in order to meet new diesel emissions standards. this is another topic really. I'm an off-road diesel tech, so I'm not really familiar with these light-duty/automotive diesel that utilize the throttle plate, so I won't say for sure if they would benefit from a Blow off valve.
Exceptions also occur in Modified applications where turbo shaft speeds and drive pressures are MUCH higher. Turbo failure is a well known side effect of pushing a turbo to it's limits on a diesel engine. Proper turbo charging can avoid these problems, but sometimes it isn't practical or affordable. So the compromise is to program a BOV into the TPS or APPS or with a micro switch to solve the problem.
Ako sam dobro skapirao blow of i bypass su slicna stvar samo sto bypass ima dodatnu ''cev" koja bi nazovimo visak vazduha vratila pre turbine u cilju da je ne koci pritisak vazduha koji nije prosao zbog zatvorenog leptira? Da li bi ovo mogao da bude upgrade koji bih rasteretio turbinu?
Zavisi kako je nastelovan i kvalitetan blow off. nece sve da ode u atmosferu uglavnom do pritiska zadatog oprugom, nece u vakum, samo ce nadpritisak biti ispusten do neke granice.način da ode u atmosferu je isto lošiji jer u tom slučaju se gubi pritisak u cevi
Navedi fabricki setup sa AFM-om gde se nadpritisak ispusta u atmosferu?JaMaL napisao:kod starijih motora koji nemaju map jedino je i moguce ispustiti u atmosferu... ispustiti iza afm klapne je lose, ispred klapne jos gore
Krsten bypass ventil bi trebao da vraca sve preko 0.4 Bar jer je pritisak preko 0.4 Bar sa zatvorenim leptirom kritican za turbinu.JaMaL napisao:kod recirkulacionih ispustice sve, jer se vraca nazad ispred turba, kod boljih atmosferskih mozes ih nastelovati.
Leptir kod JTD/JTDm nije leptir gasa, već služi samo za gašenje... Inače, neki "rasteretni" ventil bi imao ulogu čak i kod turbodizel motora sa VN turbinom, ali ne u napred opisanim, već u drugim situacijama i sa drugom funkcijom...Sone Bg napisao:Sve jasno iz teksta, ali covek koji je ovo pisao kaze da se ovo odonosi na dizel motore koji nemaju leptir gasa JTD ga ima (samo moram da proverim da li on sluzi samo za gasenje ili se zatvara pustanjem gasa, ako je ovo drugo u pitanju ovo bih moglo da se primeni na JTD-u)
Manji je problem što je uređaj nelinearan... Praktično nerešiv problem je "inercija" celog sistema (mehanika) i tu ne pomaže nikakav procesorski hardver nove generacije.Gumetina napisao:... jako nelinearnog uredjaja zvanog turbo... ... tek sa upotrebom motorole mpc5XX generacije koja ima ozbiljnu procesorsku snagu...