Doobie52

iTrader: (23)

I’ve searched and read extensively and it seems there are 2 divided camps on this issue; before the intercooler and after it. I understand the logic behind both arguments. Before the intercooler will vent hot air before it passes through the intercooler, keeping the intercooler cooler and therefore reducing the incoming air temperature. I also understand closer to the throttle body after the intercooler as not to send a shockwave of air through the system when the throttle blade closes. My question is, for the average 500-600 horsepower turbo car, which is better? Does is not really matter at that power level? Is there anyone out there who’s tried their BOV in both positions and saw a difference with some data to back up a better placement? Any answers would be greatly appreciated.

killernoodle

Doesn't matter in the least. Put it where it fits, looks nice, and is easy to work on.

The argument that it needs to come before the intercooler to vent hot air is stupid.

123quattro

Put it wherever it fits best. I always shoot for closer to the throttle.

smokinHawk

iTrader: (48)

a lot did it before the intercooler as not to pressurize the IC to much when the throttle body close and make the IC burst.
now you know all the issues so chose which one you are more concerned about.

slow67

iTrader: (2)

My personal theory is, I put it closest to the turbo, as its main job is to protect it.

NicD

iTrader: (7)

Turbo cars, wherever really works fine. Blower cars with BOVs/Bypass valves put it before the intercooler so it's not heat soaking.

killernoodle

Your personal theory is just a theory.

The speed at which pressure equalizes in a system is damn fast. Its not like you will have 15psi at one end of a 3" diameter pipe and 5psi at the other end for an extended amount of time. The pressure will equalize in a fraction of a fraction of a second.

There are some formulas here if you want to read up on the subject.

http://www.air-dispersion.com/msource.html The first one is what you want to figure out.

You don't hear about guys with rear mounts blowing up their turbos with a BOV at the front of the car for this reason. The pressure differential between the outlet of the turbo and the throttle plate is negligible. You could probably barely tell the difference if you were to put a boost gauge on both the start and finish of the charge pipe and compare them simultaneously.

To the superchager comment:
How are you heat soaking if you aren't actually compressing any air with the valve open? The compression of the air is what generates heat, not the fact that it flows through a supercharger. Charles gas law.

I_Need_Land

iTrader: (12)

killernoodle layin down the law in this thread

playtoy

iTrader: (5)

If your that concerned with it run two bov's, one before and one after the inner cooler.

pwrtrip75

iTrader: (8)

As close to the turbo as you can get....because that is what it is there to protect.

NicD

iTrader: (7)

I can see how if you didn't have any real experience and instead just relied on general physics laws you would think that. In real life you can watch the intake air temp jump pretty heavily with the BOV after the intercooler when free reving the motor because after all the supercharger is still compressing air and pushing it through the pipes/intercooler, etc even though it's not "building boost" into the motor since the BOV is open. This is pretty simple and easily verified by anybody who has tried both with a sensor right after the intercooler.

stevieturbo

It's quite staggering that nobody has mentioned the ONLY important aspect for BOV placement.

Which is before the MAF assuming you are still using one. ( ie between the compressor and MAF, but not too close to the MAF )

NicD

iTrader: (7)

The question was about any potential benefits of putting the BOV before or after the intercooler and that's it. It shouldn't be surprising that people are talking about the question and not bringing up something completely unrelated like the MAF location.

stevieturbo

Yes, but placement before or after an intercooler makes absolutely no difference whatsoever so is completely unimportant..

Bobsmyuncle

iTrader: (32)

On a blower, defanitly before the intercooler. Ive felt the air from a blower just at idle and it's still hot air.

On a turbo, closest to the tb as possible. Thts where it will build pressure first. but there might b a small gain in anti-heat soaking by having it before the ic. But only when making back to back runs.

killernoodle

I have plenty of real experience.

The supercharger is definitely NOT compressing air if the bypass valve is open. Thats like saying the air coming off a desk fan is significantly warmer.

If you are worried about heat soaking the intercooler from bypass air, then you have a crappy intercooler. At speed and when not making boost, the intercooler should return to normal operating temperature in a couple seconds.

The simple fact is, the BOV should go wherever it is best packaged. You can put it literally wherever you want, wherever it looks nice, or wherever it is easiest to work on. On a MAF system, however, you should put the BOV before the MAF so you don't get false readings.

NicD

iTrader: (7)

Absolutely correct, when it's revved up you can certainly feel the heat and if you rev it hard it can get really hot.

No you apparently don't otherwise you wouldn't say the crap you are saying. Put your hand in front of a blower and rev it, that's hot air and it can be quite a bit hotter than ambient because of how the air is compressed by the compressor wheel just to move it whether it's free flowing or not.

killernoodle

"Put your hand in front of it and rev it" sounds super scientific! Is that where you are getting all of your data?

Air is NOT being compressed by the compressor if it is not building boost. The pressure differential is tiny when the blower isn't hooked up or when it is bypassed. A boost gauge would read 1atm with the bypass open, so NOTHING IS BEING COMPRESSED. What you are feeling is the heat from the worked blower transferring to the air flowing through it.

In any case, BTUs you are feeling are incredibly insignificant compared to the BTUs generated and transferred to the charge air when you are actually making boost. This small amount of heat is EASILY transferred to the atmosphere by any intercooler, even a small one. The intercooler probably gets more heat input from the hot radiator radiating heat behind it than the bypass air from a hot supercharger

NicD

iTrader: (7)

Actually I initially mentioned the intake air temp sensor as an easy way to monitor it by watching the IAT readings go screaming upwards even when the BOV is open is pretty simple data, but I mentioned feeling it with your own hand is pretty easy too and something anybody can do if they don't have a scan tool.

So now it's making heat even though it's not building boost? make up your mind. Oh BTW a compressor wheel is not like a fan blade, worst comparison ever.

Actually the intake air temp sensor after the intercooler (yes with the BOV open and the engine revving) greatly disagrees with you. I'll give an example, sitting there revving the motor at the starting line staging the car will show a big increase in IAT readings right before you even leave with the BOV wide open.

Something like this is so stupid simple that anybody can test and see the results yet you keep arguing like you are correct. The facts remain, revving a blower up without "building boost" still produces quite a bit of heat that will drive up IATs even through a good intercooler with no airflow going through the front of it.

I am done arguing with you over the internet, anybody can feel it for themselves or use a scan tool it's very easy.

Inspector12

iTrader: (29)

Exactly! Done both and befor the intercooler was a lot cooler especially on my street cars. On the turbo car it was after, but never changed it up to try it the other way so no real data on the turbo car.