[QUOTE=Supercharged FC;10169905]So here's my map. I'm not near the surge line especially at high RPM were my issue occurred. (See circle) I was running a T04E 57 trim with a 1 A/R turbine housing. [QUOTE]

Oops here a pic that works (hopefully)

https://www.rx7club.com/attachment.p...1&d=1282185618


[Quote=Slides;10170638]
Logic fail.

If the BOV is hooked up in the conventional fashion diaphragm reference post throttle and the throttle sticks the BOV will not open, [Quote]

I did not think I had to explain this.....
If your throttle is stuck open so much you don't have vacuum it would not matter if you had a turbo or not your engine would accelerate. I always had vacuum in my manifold when I let off the throttle.

Throttle plate are not a perfect seal, my plates where held open about 1/4 inch when they stuck.

If it happen to me it could happen to someone else.

I've had the same Garrett, plain bearing, non water cooled, turbo on my engine, *without* a BOV for 140 000ks (85 000+mls) running 15psi and it is just as tight, with no slop in the bearing today as it was when I bought it.

You better put one on now you're hurting the longevity of your turbo!

...wait:scratch:

no wait. you need more proof then that. Some people are very thick.

ha so tonight I was out cruising in the 7 with this hot blonde. She had never been in it before. When I shifted or let off the throttle she would make little fluttering sounds and say "I love the sound effects!" She didn't even know or ask what kind of car she was in or what was making the sounds...

I took another friend out in the 7 a couple nights ago. He's not a hardcore car guy but he's got a mildly modified 90s turbo Volvo. He asked me "Where can I get that blowoff valve???" I told him I didn't have one and he was incredulous. "Wait... so how did you get that super sequential sound?" I said "The air comes back out the inlet of the turbo and it makes that sound." The conversation left him a little confused.

Pics of the blonde or it didn't happen!

Attachment 711135
This mod gets the Hot Blonde® seal of approval

Manlaw confirmed!

Aw your telling me the hot blonde didnt know the difference between mad tyte jdm wheels or some sportmax/rotas...lol

This thread just won!

so i look at it this way and hear me out. Now i know diesels have no thottle plate/throttle body ect... but i have worked on some high horse and stock diesel trucks with a intake on them and i can tell u that when u horse around on them and let off after full boost yea can hear the flutter from the turbo and its actually easier to get the effect on a manual. I have seen some 700hp cummins twist two small shaft turbo's from the back spool and that just from the shock from the instant back spool of 50 psi lol. So the customer put a large shaft turbo in the truck and everything is fine now. But where i am getting at is these trucks are not having any problems so far, And there are tons of diesels out there with no problems with back spool

Trots I'm starting to see a growing trend, anytime pics or blondes comes up you're all over it!! It was a nice change of pace today in class though, when I was scrolling through this thread, I did the 'double scroll' I guess we'd call it, scrolling down to the last post and then you wonder what picture just went shooting up your screen...I scrolled up, and I probably will after posting this.

...back on topic

If the blonde likes it then we all should do it.

Come to the lounge now and Pm us some of the good pics of her :)

Youtube video showing the compressor wheel of a turbo with no blowoff valve as the throttle is released.

http://www.youtube.com/watch?v=mciE5...eature=related

so apparently "dosing" is a term for running without a BOV, a "dose pipe" is a turbo inlet pipe on a turbo without a BOV, and a "dose" is a high pitched flutter.

And here is a video of "true compressor surge" under WOT (not when letting off the throttle) on a Skyline

http://www.youtube.com/watch?v=nCj6Spwl1CU

At about 1:00 on this video you can see the horsepower and boost pressure oscillating like crazy. It looks like they are operating the brake to hold 4000rpm (look in the upper left corner, you can barely see it). Under those conditions it has pushed the turbo out of its efficiency range.

[QUOTE=arghx;10187568]Youtube video showing the compressor wheel of a turbo with no blowoff valve as the throttle is released.

And here is a video of "true compressor surge" under WOT (not when letting off the throttle) on a Skyline

[QUOTE]

Thanks for the videos. It's hard to explain compressor surge without people thinking of engine surging.

http://www.youtube.com/watch?v=11ksv...eature=related
here is a turbo about to blow up lol!!!!! See turbos can handle this

/\ /\ /\ = I ran 3 years at 30psi held (about 25-30k hard miles or so) with no BOV and no worries on a T3/4.

^^Im with you on that one Supercharged, unless someone can show the numbers to back it up, dont believe it.
CBR now uses a BOV on his race car, after having told me not to other with them (I fitted one anyway).
The theory behind a bov make a lot of sence, so unless actual test show they arent needed, and so long as every factory turbo car i have seen under the bonnet of uses one, ill use one on my street car.

Its a bit different with a car that doesnt usualy close the throttle until the end of a run down the track

Arghx, do you have any notes from BW on their development of the EFR turbos, specifically why they chose to run an incorporated BOV?

I alluded to this in the other EFR turbo thread. So, does this look familiar?

https://www.rx7club.com/attachment.p...1&d=1289955369

Sorry, I am pretty dense. What does it resemble?

Well I'm upto 22 months with no bov. The original turbo with probably 20 of those months is on my shelf. No thrust play. Side to side feels normal.

My question is, if I want to BOV. Not because I need to. How do I get the bugger to seal underload unconditionally but also open on light lifts that induce surge with a small T3/T4 size turbo.

Light spring.

The only limitation is you have to work out the diaphram to underside (ie intake pipe sealing face) piston ratio if it isn't 1:1 & to compensate for intercooler pressure loss if it is before the intercooler (for it to hold shut WOT) as the post throttle pressure could be 2-6psi less than pre intercooler.

If it is just in front of the throttle you should be able to get away with a half pound spring.

Else if you have a sealed unajustable unit, I guess you would go the other way and run it just after the compressor so that the pressure differential was greatest post throttle vac ref vs compressor outlet provided it wasn't leaking on load, i guess you could tape a whistle to it or something to make sure it wasn't leaking at peak load.

That's the factory recirculation valve/diverter valve/blowoff valve on a VW/Audi 2.0T engine. The turbo is made by BorgWarner and the recirculation valve is pretty similar to what the EFR turbos have. You can see this one for the 2.0T uses electronic actuation like Ford Ecoboost recirculation valves, but BW has had the pneumatic design (similar to what's on the EFR) for longer. The BW EFR turbos are using recycled designs from 6+ years ago. Just like there's nothing new about a twin scroll inlet with dual internal wastegate passages.

As for the efficacy of the design, well I don't have any lab tests. It seems to me though that it would be the best air bypass valve design because it is relieving pressure right before the compressor wheel so the wheel won't brake as much. In my mind if you are going to have a blowoff valve this style of integrated recirculation would be the best one to have.

BMW has the best design though because they go around the problem altogether. The N54 twin turbo engines do have more traditionally designed recirculation valves but they actually keep the throttle open during shifts. Yeah, you heard me, they don't close the throttle between shifts.

https://www.rx7club.com/attachment.p...1&d=1289964622

The BMW N55 engines don't have a throttle valve at all. Gasoline direct injected engines don't need throttles. In 5 to 10 years there will be very few gasoline engines with throttles. Mazda has had unthrottled direct injected rotary engines in labs for decades.

At this stage. I'm going to call my intercooler pressure drop .14bar 2psi @ 5000rpm, .3bar at 7000rpm. The known error is a spring that assumes 1:1 EMP:IMP.

Expected high exhaust manifold pressure.

IAT sourced in air pipe is 45degC after 3 gears @100% throttle, from a steady state of 30degC cruising.


So slides, an engineer would make a BOV with a larger diaphram surface area than piston surface area, to remove the problem is blowing open?