Hello all im new hear and very interested in the Z. i have my Z picked and as well as all the parts that i want to get. The only thing that is stoping me is that i have to sell my car right now first. Anyways, im new to the hole turbo thing and i was wondering what it sounds like on a car. When i get my car im going to get the Greddy TT kit and was wondering if anyone knew where i could hear what the BOV sounds like? is it loud? is it quite? and why do people change the ones that you get from the kits, like what is the purpose? thanks for all your help.

 

the greddy TT kit doesnt come with one originally and there is argument on wether or not you need one at that boost level.. I'd get one just to be safe.. It sounds like a loud high pitch whistle... You can hear it from inside the car with your windows up. I have nothing to compare though since its my first and only turbo'd car i have. Other kits make different sounds... Im not sure where to get the sound files... but you should know that everyone always asks me what the hell that noise is...

 

wait the bov does come with the kit. 2 of them unless im mistaken. but let me ask you this. is a wastegate and a BOV the same thing? and thenyou said you may not need one at that Boost what do you mean by that?

 

im sorry.. i didnt know what terms you knew or not..

A wastegate regulates boost pressure and there are two of them, one for each turbo. Your wastegates will open at a certain boost pressure depending on where you set it. This is primarily when your foot is on the accelorator.

When you take your foot off the gas, your throttle plate closes, but the turbos are still spinning trying to put air into the engine causing air to rush backwards towards the turbos and spin them in the other direction or slow them down. This weakens the turbo.. this is known as compressor surge. so what a Blow off Valve does is let that surge of air escape before messing with the turbos. the BOV is only in effect when you take your foot off the gas and usually makes a noise you can hear a whistle or phssst shound or whatever they designed it to make. as soon as you step on the gas again you dont need the BOV anymore because the throttle plate opens up letting air back in the engine.

What i meant by the boost level is to think of it like this... At the stock boost setting the kit comes with... they feel that the surge of air is not strong enough to really do any damage to the turbos.. so they didnt include a BOV... the higher you set the boost pressure.. the more you need one... but i mentioned you should get one anyway... because any surge of air rushing back at something spinning in many thousands of RPM's (compressor in the turbo) cannot be good for it..

That is why you see people buying BOV's they arent changing them... they are getting them.

 

Correct.

Although, doesn't the wastegate have to do more with the RPM's than how much the accelerator is pressed/depressed? You can downshift and raise the RPM's and not even touch the accelerator.

Also, there is a "bypass valve" that's basically the same as a BOV although it let's the air out back into the intake system. On BOV's, if the air is released after the MAF, the engine will run rich for a second or so due to the air being measured and then it dropping some of the air it had already accounted for.

 

ok i am kinda of getting this. So what comes with the kit is a wastegate. so when i buy the kit i should purchase a BOV correct? If so then what one do i go with? does it really matter or are they all the same? and i would have to get one for each turbo right? once again im new to all this and and trying to teach myself alot but it helps when people explain it for me.

 

One wastegate per turbocharger, yes. Yes, I think you should. Many have went with the GReddy Type-S, now there is a model that is called GReddy Type-RS (most recent BOV) and is supposed to be "better", i'm not sure how. Here is a link though: http://www.cipmotorsports.com/grtyrsbovit.html It does matter which one you go with, some make different sounds, and I believe some are rated for a certain amount of HP. I believe you would only need one for the Greddy since it goes 2-1 out/inlets for the GReddy FMIC so you only need one for one pipe after the intercooler, so one total.

Also, I believe another company makes something that sounds similar to the HKS SSQV BOV (HKS Super Sequential BOV), it makes a rattle snake sound, I think Tial makes one that sounds similar to it, but there are only two if i'm not mistaken. They have a unique sound compared to other BOV's, just something to consider.

 

Greddy has discontinued the Type S and now the "new and improved" Type RS is out. I had a group buy on the Type RS recently and can still get you a good deal if you're interested.

Here is a pic and some verbage about the bov:

Greddy introduces the RS their new blow off valve. Equally as innovative as their Type S blow off valve which is one of the most popular unit which is used by enthusiasts worldwide. The RS features a lower profile as far as height and has a 40mm opening which is 4mm bigger than the Type S. For installation, the same flanges can be used that fit the Type S.

Key Features:

Eight discharge ports that draw in surrounding air.
Features a 40mm hard anodized valve for increased airflow and durability.
High quality diaphragm and short stroke which significantly increase response.
Optional discharge adapters for rerouting discharged air.
Dual spring system which promotes response and allows for high boost pressures.

 

lol sorry nis... i wasnt trying to be perfect.. just easy to understand the basics..

Also GTP, nis mentioned MAF.. that stands for mass air flow (sensor) its a black tube you should be able to see running up towards the big silver plenum on top of your engine its only a little section of it.. inside is a sensor that detects... well.. your airflow... and adjusts fuel accordingly.

Good write on the bypass valve too nis...
Yep GTP you need one wastegate per turbo and one BOV recommended for each.. in the greddy kit in this case they all lead to one pipe.. so like nis said... you only need one BOV... for stock use... i think you can get most of them out there... but stick with the HKS or Type-s or RS now from greddy... they are both good to use with this system... if you start thinking about other ones then you open up a new bag with spring strength dependent on boost and diameter of piping and all stuff like that.. stick with those or ones you hear about on these forums... they all make cool noises so i wouldnt worry too much about it.

 

Yeah, just making sure he understands it right though, don't want people going around quoting general info that more knowledgable people will "tear" them up on.

D'oh, forgot that.

Thanks, that bit of info is courtesy of miaplaya and mystik 350z, interesting thread: https://my350z.com/forum/showthread....hreadid=110755

Agreed.