j/w bc it didnt spin the tires at all. usually second is completely useless

It spins badly in 2nd when it's colder outside

One of my previous cars was a 83 Callaway turbo rabbit gti. A small amount of rabbits were sent to Callaway for a turbo charge setup. It included a big t4 turbo external wastegate and intercooler. It did not come with a bov. It was like that since 83 and it had countless miles on it with same turbo. I finally ended up selling it in 2001 and the motor and turbo were all in good condition.

From this experience I’m probably not going to run one on the rx7

im suprised were still talking about this. Blow off valves are a waste of time.

I will not be using a BOV on my new setup, this thread is motivating

No Bov? wtf it sounds like you're running one lol

haha i hear it too.. wicked surge. im going to try the no bov theory tomorrow see if i notice any change in response between shifts.. im replacing my turbo soon anyway


but another thing to consider is most stock turbo cars with no bov have very small compressors.. maybe having no bov does not cause much damage simply because the compressor is not big enough and less momentum to cause any damage to blades and bearings. most of us on the other hand are running compressors a lot bigger and have a lot more momentum when they hit a wall of air when throttle is snapped shut.. which may cause more damage?

My turbo has an actual flutter sound when it surges though..doesn't sound like a bov like his

The sound changed a lot when I switched air filters. I had a 4" inlet 3.5" length shorty filter (same one that is in that thread). After some careful measuring I realized that I could fit a 7" long cone filter so I switched. After that the sound of pressure relief changed a lot. There's a small amount of flutter at part throttle low boost but that's it.

Bizzare how you can hear a chuff on your car with no BOV? Where would a chuff come from, i mean a flutter makes sense, but?!

Ive ran maybe 10 cars with no BOV and they all chatter, makes no sense for them to do anything else.

My FC chatters like crazy, but no damage in nearly a year so far, and runs pre-comp water injection and prior to that it ran for ages with no air filter- literally ALL the things people claim will kill your turbo, lol.

Ill try and get a video before next weekend.

Here's a quick vid of mine running no BOV if anyone is interested...
http://www.youtube.com/watch?v=BSSuppCnFWw

Mine kinda sounds like that with my little Greddy RS BOV lol.

thewird

I'm just curious, and maybe this has been covered and i didnt see it, but y are bov's evened used, and are the stories of turbos coming from together just wives tales?
is it just precautionary?
are these breaks from 20-30psi systems?

and in my case; would it be appropriate to run my car minus bov?
its stock internally, but im going to be running t04e w/ .82 a/r about 8-10 psi,
also has 3'' ex. from housing back, 2.5 intercooler piping. 550 1's and 750 2's and rtek 2.1
(just a quick rundown)

i'm just very intrigued by this and ARGHX's word is pretty influential to my build.

I wouldn't consider running without a BOV unless the turbo is ball bearing. I remember reading somewhere where there was information about the Garrett turbo's and they specifically mentioned that the non-ball bearing units will not last without a BOV long term.

thewird

IMHO, from experience, thats not true.

Almost the only turbos ive seen break easy with no BOV were garrett gt series, as seemingly they had fairly thin shafts compared to other turbos. As the only fails I could 100% say were no-bov related were shafts snapping, which ive seen a few times on GT35Rs.

Ive ran 30psi boost for at least 12 thousand pretty damn hard road miles on a non-bb garrett t3/4 turbo with no damage, 25psi on another slightly smaller garrett non-bb, and know countless other that have done similar too.

Its always a risk and a complex issue you can never be sure of. But ive always (for 10yrs now) had perfect luck with big boost and no BOV and know countless others in same situation, so personally, i never bother with them.

Don't know if its true but I remember reading it a while ago. It didn't say the non-bb's would break, only not last as long as the bb counterpart. I'll see if I can find anything on it tomorrow.

thewird

I am running a Garrett T04R (non ball bearing) which I purchased used off this forum. Most of the turbos people use on Rx-7's "big shaft" turbos, not the smaller "standard shaft" As for ball bearing vs journal bearing, I can't really say whether it makes a difference.

I stopped using a bov on my 87 TII after I installed my E6K. No air flow meter no problems.


http://www.autospeed.com/cms/article...estions&A=1457
Is there any performance gain to a blow-off valve?


"We've tested one on a manual gearbox performance car run at Winton Raceway. I think it was running 1 minute 40s back then, but it would lose 2 seconds a lap putting the gobble-gobble valve on. When you look at data acquisition, what you find is - as you change gear - the blow-off valve dumps all the pressure built up through the intercooler and pipes. It then goes back to zero manifold vacuum when you get back on the throttle, you have to build all that boost back up.

"The fact that people think that they keep the turbo spinning is a problem. The people that suggest this have never had an engine on the dyno and never had a turbo tacho in their hands. What people don't realise is, when you shut off the throttle, you shut off the air supply to the engine - this shuts off the exhaust gasses coming out of the engine. When there is no exhaust flow, there is no energy to keep the turbine spinning - the turbo slows down at an alarming rate.

"If you change gears at quite a good speed, you can actually get a boost spike on changes; if you're trying to hold a constant 30 pounds, when you do a racing change you'll get 32-33 pounds when you crack the throttle open again. If everything's working well, you've got a full head of stream waiting to go into the throttle as soon as it's opened.

"I've done this on a rally car and it was quicker through every timed section without a dump valve. You'll never hear a World Rally Car going pssshhht because they don't use a dump valve - you get the woof-woof-woof noise instead."

I'm getting closer and closer to removing my blow off valve lol.

thewird

What more proof could anyone have.

I think it's important to remember that none of us are running a MAF sensor, so there are no potential driveability issues to worry about due to a messed up airflow signal.

OEM has MAP, not MAF, sensor, right? Mine is OEM (whichever that is). Am I OK to run bov-less?

FD uses a MAP sensor only (Bosch D jetronic style, aka speed density), FC uses a vane-type volume airflow sensor (Bosch L Jetronic style) for load calculation although it does have a factory MAP sensor as well. Only the Rx-8 has a factory mass airflow sensor.

damn that sucks, make sense but sucks..
Rtek needs to hurry up and update to get rid of the maf!

Actually, away from the reliability issues (or lack of IMO), we did some timed with and without a BOV performance tests this time last year on a 400bhp SR20 engine running 1.5bar boost BUT still with the AFM, so it was actually making the car stutter between gearchanges without a BOV.

BUT even with that issue messing things up hugely (i mean the stutter was audible and even visual watching the car, the 20-80mph time (with a ultra close ratio box, starting in 1st and ending in 4th) was 0.7 of a sec faster with no BOV.