Trots*88TII-AE*

iTrader: (11)

I got you now Arghx. It certainly isn't uncommon for the aftermarket to hype up "new" products that are lightyears behind the OEM, just look at our selection of fuel injectors.

The no-throttle DI engines are pretty neat.

blue87

iTrader: (2)

A big part of theproblem with aftermarket parts is they are designed for a broad range of vehicles etc. The computer logic and processing horsepower necessary to make new systems like DI, with twin independent VCT, variable lift, etc require countless engineering hours, engine dyno mapping, DOE and lots of computer modeling just to control, and all of this with proprietary software and hardware. This is affordable by an OEM becuase they spread the development cost over thousands/millions of vehicles. To get to an OEM level on a single custom vehicle it would literlaly cost you millions of dollars.... I always think it is funny when an aftermarket "chip" company or whatever claims to be better than OEM.. maybe in one aspect but as with everything there are tradeoffs...

pointless rant over...

Yes I agree Direct injection is very cool, there are many things you can do with DI that are not possible with port injection, like use fuel as knock control without going pig rich, multiple injections per cycle, near instant response...

Slides

Yes, or rather, throw it in the bin , or experiment with intake side boost control if it was a roller bearing turbo & space was tight.

Jobro

iTrader: (2)

I could have easily done intake side boost control. In fact it would have been easier not harder. I heard the argument 'do/did formula 1 cars use it' and then decided it was flawed.

Zero R

iTrader: (1)

"true compressor surge" Both of those videos actually show compressor surge, one however is more damaging than the other due to load on the turbine being greater.

~S~

RotaryEvolution

iTrader: (30)

on MAP based cars the MAP sensor is constantly reading your intake pressure past the throttle body, so any residual pressure in the system or passing the throttle body is already being compensated for.

thewird

iTrader: (8)

^ Also, detonation can't happen without fuel. Injectors being shut off != less fuel, its equal to no fuel. When injectors shut off, its not like they shut off mid duty, they only stop injecting next cycle so the previous cycle has the correct amount of fuel and the following cycle has none.

thewird

muibubbles

iTrader: (36)

sooo, im kinda reviving this..

I dont know if i believe no bov is better than a bov but, it seems like its mythical. id run a bov just because thats whats familiar to me. BUT i dont have one at the moment and my car is almost about done. I have to break in my motor so i wont really see boost so will i be okay if i drive around a few miles without a BOV? (remember i wont be going into boost)

arghx

iTrader: (3)

It will be fine, especially because you are not boosting and because the FD doesn't have a MAF sensor. I've been going 2 years without one now.

vosko

iTrader: (4)

5 Years and multiple cars for me

ZipRex

iTrader: (2)

Just a little thanks for reviving the thread so I saw it and read through it. Thanks to arghx for being a guinea pig and keeping us up to date on his adventure. Kinda nice to get to the end and see it doesn't really matter.

Indian

iTrader: (1)

good read... take it for what its worth http://www.autospeed.com/cms/article...estions&A=1457

97SupraTwinTurbo

iTrader: (8)

Real simple, if you can shift very quickly without lifting you don't need a bov. If you need to lift & your shifts are not as quick as an F1 then a bov is needed to stop turbo surge & damage to internal bearings, etc.

It might not happen in 1 day but turbo failure will eventually occur. It is not for emissions, horsepower increase, or mythical sales figures, these are facts. In order to keep the turbocharger spinning while in between shifts or in neutral after it has been in boost, pressure needs to be released if a throttle body is present. This is a fact!

Slides

If that is the case, why in the **** when people actually ran bush/thrust bearing turbos with post turbo throttles without ignition retard or cut/fuel cut shifts in endurance race cars running much lower trim large diameter high PR setups in teams with massive budgets did they not use these valves?

So have you instrumented even one car with turbo tacho, pre throttle pressure sensor and such and actually logged what happens?

Pressure pre-throttle rises very slightly, but being a centrifugal compressor, unless you have run it into choke, it will only support around the same pressure ratio (and when flow reduces into the turbo there is less intake depression and hence a slight increase post turbo as PR stays the same) at any given rpm regarless of flow rate until if falls into surge.

Turbos don't turn backwards & shaft/compressor interface loading is much higher on load. The only issue you might have with a bush/thrust turbo with very loose tolerances is axial vibration.

Given so many of the BOV alarmists actually want their cars setup with ignition cut rev limits or 2 steps i find it hilarious as if anything is going to overload the turbo bearings, ignition events in the exhaust manifold will.

******* retards

97SupraTwinTurbo

iTrader: (8)

Compressor surge:

The surge region, located on the left-hand side of the compressor map (known as the surge line), is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur. When referencing a compressor map, the surge line is the line bordering the islands on their far left side.
Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself.
Common conditions that result in compressor surge on turbocharger gasoline engines are:

* A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
* The outlet plumbing for the bypass valve is too small or restrictive
* The turbo is too big for the application

arghx

iTrader: (3)

Interesting to read that from someone with a forum name of 97SupraTwinTurbo, an engine that was engineered to compressor surge under full load right off the showroom floor (with a warranty!). That's what happens to the No. 2 turbo on the 2JZ when the intake air control valve and reed valve are shut during prespool. The Rx-7 and Cosmo also compressor surge under full load; Mazda has provided detailed documentation on this. It helps improve spool of the No. 2 turbo. I have the documents to prove it; see https://www.rx7club.com/3rd-generation-specific-1993-2002-16/comparison-rx-7-13b-rew-supra-2jz-gte-sequential-turbos-960727/ and I can also email them to you. A turbo can withstand sustained compressor surge under full load for a limited time without damaging anything; both Mazda and Toyota used that principle in the design of their sequential turbo systems.



As I've said in this thread all along, I don't fully have a dog in this fight. I wouldn't say I'm for or against air bypass valves and I've run with and without them. But deleting a blowoff/bypass valve isn't going to blow up your turbo, not in this kind of application. I don't consider the compressor wheel stalling under deceleration as 'true' compressor surge, because there are basically no exhaust gases driving the turbine. The main thing that affects the speed of the compressor wheel between shifts is the bearing design; we all know that ball-bearing turbo maintains compressor speed much better.

THE.RATH

This was a good read haha!

Slides

There is a massive difference between a couple of tut tuts on throttle off with no exhaust energy and running 30-40% of full power exhaust flow energy into a loaded compressor with a missmatched cold/hot side combination when it comes on in the midrange. As evidenced by the fact that manufacturers are still using parallel sequential systems, you have to run the secondary turbo in surge up to a point so that when it is allowed to flow it has the wheel speed to sustain the pressure in the intake system.

StavFC

I love how people with no experience of it will tell people with countless years of exeprience that they are wrong and a load of cut n paste 2nd hand info is their proof.

Theory and reality are very different.

Ive got first hand experience of the reality, about 10 years worth, countless cars, inc a 23psi rotary, a 25psi old pushrod blow thru beasty, and a 30psi 4pot, all used hard on roads and circuits too, not a few quick runs up a strip, and I know what breaks and what doesnt. Dont think 10yrs worth counts as me being 'lucky'

Uwan

iTrader: (4)

Im not jumping on either side of the fence here. I currently live in Okinawa Japan and I drive a JZ100 Chaser with a single turbo 1jz. I dont have a blow off valve and its been that way since the previous owner. Its a common thing here on island for the locals to run with no blow off valves. Car still pulls strong.

Mindphrame

Interesting!

My first car was an '88 Chrysler Conquest TSi. Stock it didn't have a BOV, nor did it recirculate to the best of my knowledge. Extra pressure just went backwards through the turbo / intake. I really do miss the ol' compressor "surge" sound. Hell of a fun car, and damn quick too. Did end up replacing the turbo at ~98k miles, though its failure was due to a cracked oil line.

1FAASTFD3S

iTrader: (33)

Ive been running no Bov on my Greddy T78 setup for over a year now, the turbos response is very quick between shifts and is showing no adverse effects..

indio84

iTrader: (7)

shoot i think i will try this

pito13b

iTrader: (3)

Arghx, thank you for posting this up and experimenting, along with the others who are doing it. I am in the process of upgrading my intercooler and piping. With my current setup I am getting "surge" at low boost since my BOV can't respond to my low vacuum. I have been running like this for 2 years. I was actually going to try to cure this by using a synapse valve. Thanks to this thread I can save that BOV money and get some new injectors while cleaning the engine bay up even more!

Only problem is I think I am a ricer since I have a "dose" pipe! My intake runs to the nose of the car.

http://youtu.be/JUGOkyJbJpw

shetlen

iTrader: (2)

Very informative thread. Looks like I'll be saving a lil more money by not buying a BOV for my build.