FDNewbie

iTrader: (10)

ok...i looked over a cpl old threads, didnt c anythin really explaining my very simple questions..

1) am i correct in sayin that boost controllers are mainly used to control boost spike, vs. normal boost (wutever psi ur runnin)?

2) if so, are they very effective?

3) i have a PFC..i know you can set the boost usin the commander, and appropriate fuel maps, etc....but would u need a boost controller like the apex unit as well...to control boost spike? cuz i was told by a few ppl that my setup (intake, DP, MP, freeflow exhaust) im bound to get real high boost spike, and blow my engine. so...is that rite? (i dont wanna get a more restrictive exhaust or replace the MP w/ a high flow cat....and from wut i understand upgradin the wastegates will control boost, but not boost spike...)

thanx

DCrosby

I'll say it once, and I'll say it 1000X get a Relief Valve from Greddy or whomever, It's like a BOV, except it opens at a preset amount of pressure, and vents the excess, unlike a bov, that vents pressure when it detects throttle body vaccum....
This whay no matter what you do you have "Insurance" that you won't go past a certain point...

With Boost controller, if improperly set, you can still blow your motor, but I guess you can with the Relief Valve as well, so Stupidity = All bets are off..
But the Relief Valve will be less $$ than the Controller...

FDNewbie

iTrader: (10)

my bad man...dont think i ever read ur post about that. didnt mean to make ya say it 1001 times =)

can u use the relief valve in conjunction w/ a BOV? cuz i have the HKS SS BOV...which i thought was essentially a pull-type relief valve...

and where does the relief valve mount?

thanx

Str8Down

I would like to know about this releif valve as well. Where does it mount, how much does it cost?

FDNewbie

iTrader: (10)

greddy list theirs on their website for $120, + $38 for the adapter...

but that's about all i know
(it's the last thing on the page)
http://www.greddy.com/products/blowoffvalves_frame.htm

911GT2

1. Yes. Boost controllers can eliminate spikes and hold boost at a set PSI.
2. Yes, if set up correctly they are very effective,
3. The Power FC has been known to be a inconsistent boost controller at best. I would suggest another unit solely for controlling boost, such as the GReddy Profec B. Your setup is quite dangerous without an ECU, if I were you I'd stay off the boost, if not stop driving the car until you can get an ECU or at least a boost controller.

FDNewbie

iTrader: (10)

911GT2....thanx 4 the advice and answering the questions

but i do have an ECU..i have the PFC. but im still worried bout boost spike...

so my main issue was..should i get the Profec B (or relief valve) or was i straight

911GT2

Yeah, sorry, I guess I read that and forgot it.

I'd say get the boost controller, better to be safe.

rynberg

IMO, relying on a pop-off valve to control boost is a really, really dumb idea.

1. A boost controller will allow you to actually CONTROL your boost, not just set a LIMIT.

2. I seriously doubt most POVs were designed to be in use constantly so I would worry about reliability.

3. With a POV, your poor turbos are still generating excess boost so they are being subjected to excess wear. A boost controller prevents your turbos from working so hard in the first place.

FDNewbie

iTrader: (10)

rynberg... i feel all wut ur sayin, but w/ reference to my situtation, would it still apply since i already have a PFC...so i have my boost set at a certain level...

alberto_mg

yes it would still apply. to summarize:

- the power fc does a good of control the max boost you want to run, however...
- you will definitely experience boost spike with a totally open exhaust even with the power fc. especially in cold weather. in fact, you have probably experienced it already given the weather in DC.
- you might experience some boost creep with a totally open exhaust in the upper gears (4th, 5th) and at higher rpm. some cars do some cars don't experience creep even with the power fc.

let me see if i can spell this out clearly for you...
boost spike is bad b/c when you jump on the gas at low rpm especially with an open exhaust (mid pipe), the primary turbo will spike up to whatever psi level it can hit. given that your exhaust is totally unrestricted (no cat), that psi level is probably upwards of 15-20psi. if your power fc is tuned to run 15-20 psi, this is ok (kinda) b/c you will have enough fuel to support the necessary air/fuel ratios to run that psi level. when you don't have the correct air/fuel ratios, the engine runs lean and detonates and poof! there go your apex seals. you only need this to happen one good time b4 your engine blows.

given your questions, i doubt you've been tuned for that level. also, running the stock turbos on high psi (over 12psi) for extended mileage will help to decrease the life of your turbos.

i understand that a properly setup boost controller will help control spike and creep. i don't have one yet so i can't say with 100% certainty. however, i do know that with my setup i did see a spike approaching 13-14psi on the primary turbo. i quickly let off as i don't want to blow this baby...

vchacon

I have to agree with the others here regarding the PFC. I plan on getting one soon, before I open up the intake, and have been reading up on them. They seem to have a bit of trouble controlling boost spiking and creep.

I'm thinking of doing the following:
https://www.rx7club.com/showthread.p...hreadid=242324

I like the setup... anyone see any downside to this other than it's a manual controller.

alberto_mg

the downside to a manual boost controller is that you need to adjust based upon the temperature outside. On a cold morning, you will run more boost than a warm afternoon. given that you are in cali and the temps are more moderate there, it might not be an issue. research it a bit.

vchacon

Yeah, I think that was the only downside I could see but being in So Cal might not be too much of a problem. I was thinking of doing the home depot version just to test it for a while through the next month or so.

vchacon

Forgot to say thanks, alberto_mg, for the reply

FDNewbie

iTrader: (10)

hey guys

thanx 4 the explanation and suggestions. much appreciated =)

DCrosby

Relief valve is more safe than a Boost Controller, since even if you have a boost controller if the wastegate is too small to divert enough exhaust to stop the turbine blades from accelerating you have boost creep which a boost controller will not solve, cause it can only open the wastegate all the way and that's it it's a mechanical limitation. Get the wastegate ported (opened up more) if you want to elliminate that factor.

As for the brilliant insight on the BOV, you are incorrect the BOV is meant as a relief valve under negative manifold pressure and is typically open all the time under vaccum. Have you ever fed positive manifold pressure to a BOV ?? It snaps shut ! This is an entirely different animal, this (Relief Valve) opens up if it sees more than a preset amount of Positive manifold pressure (Boost) and unlike the BOV (Relief Valve) stays shut under vaccum. The Relief Valve mounts on any metal intercooler pipe.

Think of it like this, the BOV = Security Device for compressor surge, and operates at -manifold pressure only.
Relief Valve = Safety device that prevents too much boost from getting into the engine and leaning out your fuel.

they're opposite sides of the same coin... the advantage of a relief valve is that you don't have to port the wastegate since either boost creep or boost spike will open up the valve to vent excess pressure and keep your engine safe... (And it's designed to do ONLY that job)

I do belive Greddy sells a valve that'll do both, but I've always hated all in one solutions, the cost less in the short run but if you have to replace one you're buying a whole new one as opposed to the thing that's broken.

And I also have A HKS SSQ as well.... on top of the Relief Valve

-DC

DCrosby

That's cool, wasn't directed at you !

I've tried to say something to a number of posts (10-20) that have asked about boost creep with a MP and what can be done... your toughest obstakle is going to be to find a Metal Pipe... You Might have to get a greddy elbow, or fab one (aluminim pipe) in-between the rubber parts... either pre or post IC, makes no difference, the only thing you might think about is it important to cool air, you're going to vent ? Probhably not, so best place IMHO is before IC an Effini Y pipe will do fine...

FDNewbie

iTrader: (10)

<< And I also have A HKS SSQ as well.... on top of the Relief Valve >>

u wouldn't happen to have a pic, would ya?

sub-zero

FDNewbie, Make sure You have enough fuel ( good fuel pump,clean filter, or even upgraded fuel injectors will help) Make sure Your maps You are using are right for Your setup and even add a bit of fuel if You are unsure in the PIM settings. I would worry more about Your AFR`s more then spiking boost levels with the PFC. What boost levels are You expecting? With an open exhaust I would upgrade the injectors and Your pump for sure and dont worry about running a decent amount of boost if Your engine is healthy. Also keep it cool and things should be alright. Are You running non seq.?

sub-zero

Plus that releif valve will spin the **** out of Your turbos if that is what Your using to control boost?

rynberg

Exactly, but Dcrosby is ignoring the points I brought up....

FDNewbie

iTrader: (10)

Subzero...

i just changed my fuel filter, got a supra fuel pump, upgraded the injectors 850s (pri) and 1300s (sec).

the engine actually has low compression...im expectin it to go blow soon enough. so that's the other thing, i wanna make sure when it does go, i got everythin ready to take good care of my new engine. last thing i want is boost spike on the new one...

un4tunately, the guy i bought the car off of was runnin the car w/ intake/DP/MP/exhaust and no fuel management, and boostin 13psi. and that's w/ stock IC too. yes, that's prob why the engine has low compression lol. rite now i have the PFC makeshift tuned for 11 or 13 psi... but imma get it tuned right soon. it's not a real pressin issue at this point since im not drivin my baby durin the winter... but im tryin to get everythin 2gether and set for springtime...

oh...and no the turbos aren't parallel. im still sequential (does it make a diff? w/ respect to boost spike, etc?)

DCrosby

If you're NOT PORTING the wastegate, this is the ONLY way of safely running a MP, the boost controller can not prevent boost creep, and it seems to be a temporary solution for him, since he seems to see that once he's upgrading / "Leaning" on one system he needs to upgrade the rest, which is fine, but you want something inexpensive, and functional, while he gathers money to remove his turbos and gets his wastegate ported, on top of that, once he has the wastegate ported, he now has a safety device that can prevent any mechanical failure he encounters later on with boost spikes, or mis adjusting a "Home Depot" Boost Controller, you're trying to make a point similar to saying why use a bigger core rad (koyo), if you're never going racing, cause you want the added safety of knowing that you can run through the desert, and not "Sweat" the water temp...

Besides, what do you have against a Relief Valve ?? You're adding security, and yes would posibly run a couple of rpm's higher on the turbo, what about all the RPM's you waste when you get on the throttle and then let off and the BOV lets go of all that boost you built up and possibly intercooled !? Nobody's crying about BOV's runeing your turbo, because compressor surge is worse... so is boost creep...

DCrosby

I'm not ignoring you, I just think you're not fully informed what a controller will do for you.
The controller has a Map Sensor, that reads the boost, fine.. and if you spike, it'll throw open the wastegate, which deverts the exhaust to the DP instead of the turbo. So if the wastegate is allready open all the way, it has just run out of options, opened up the wastegate no further. Since it's at it's mechanical limits, and the compressor starts to add more boost to the intake, which in turn causes more exhaust to escape .... To the wastegate which can only divert so much and more and more starts getting into the compressor side of the turbo, causing... Boost Creep.... nothing your boost controller can solve since the wastegate is OPEN all the WAY !!!

So you have to port the wastegate or break the circle... but if you're really that thick headded, go ahead, and try it on your car and let us know how a MP with a Boost Controller to controll boost creep works for you.

I personally will admit, that I have not used this system as I am in the middle of a rebuild, but as others, I did some research as well as talking to my mechanic about knock controll, and boost issues, or "Insurance" on getting as much performance out of my car, with as much safety to prevent mechanical or user error from blowing my motor... I Personally am getting my wastegate ported, and I'm adding a Relief Valve, and I have a boost controller as part of my ECU system, so I'm personally going to employ all 3 safety measures, making damn sure that boost spikes, and creeps are not part of my future...

-DC