compressor outlet elbow help

[Kronic_420_Haze]

i bought a 1 3/4" Compressor Outlet Pipe from dejontool and it didn't come with the pressure fitting on it. is there a way i can still install this part with out the fitting or is there a easy way to add one on with out it causing a boost leak.... i have no boost controller yet would that help solve the problem if i installed one? thanks

 

[99gst_racer]

So, let me get this straight.... You were using the stock j-pipe and now you upgrading to one w/o the little vac nipple, right?

Easy fix. Take that vacuum hose that used to run to the j-pipe, and tap it into the BOV's vac line. It is the same pressure source, so it will work just as it did before.

 

[CyberEye]

I just drilled and tapped a hole in my j-pipe and threaded in a 1/8" npt pipe fitting

 

[Kronic_420_Haze]

so i T it into the top line from the bov.. thanks

 

[99gst_racer]

so i T it into the top line from the bov.. thanks

Yes, that is the quickest and easiest way of doing it.

 

[skelly]

...Take that vacuum hose that used to run to the j-pipe, and tap it into the BOV's vac line. It is the same pressure source, so it will work just as it did before.

Minor correction: it will work, but it's not exactly the same pressure source. The nipple on the compressor outlet represents non-intercooled, compressor-outlet pressure. The line that feeds the BOV is not only intercooled (lower pressure), but also subject to vacuum conditions of the intake manifold. The compressor outlet nipple NEVER sees vacuum where the one on the IM sees both vacuum and boost. So long as the wastegate's diaphragm can't be damaged by applying a strong vacuum source then you're in good shape. A check valve wouldn't resolve this either because you need the wastegate signal to pressurize and de-pressurize which reiquires bi-directional flow.

 

[99gst_racer]

Minor correction: it will work, but it's not exactly the same pressure source. The nipple on the compressor outlet represents non-intercooled, compressor-outlet pressure. The line that feeds the BOV is not only intercooled (lower pressure), but also subject to vacuum conditions of the intake manifold. The compressor outlet nipple NEVER sees vacuum where the one on the IM sees both vacuum and boost. So long as the wastegate's diaphragm can't be damaged by applying a strong vacuum source then you're in good shape. A check valve wouldn't resolve this either because you need the wastegate signal to pressurize and de-pressurize which reiquires bi-directional flow.

Very interesting.... Thanks.

 

[Kronic_420_Haze]

so then i shouldnt use that aftermarket elbow without the fitting.. i have a stock 1G bov if that matters

 

[oldman]

Minor correction: it will work, but it's not exactly the same pressure source. The nipple on the compressor outlet represents non-intercooled, compressor-outlet pressure. The line that feeds the BOV is not only intercooled (lower pressure), but also subject to vacuum conditions of the intake manifold. The compressor outlet nipple NEVER sees vacuum where the one on the IM sees both vacuum and boost. So long as the wastegate's diaphragm can't be damaged by applying a strong vacuum source then you're in good shape. A check valve wouldn't resolve this either because you need the wastegate signal to pressurize and de-pressurize which reiquires bi-directional flow.

Very interesting read, I read this earlier and it got me thinking. Do not take this as anything but a technical discussion.

1. I would tend to think that pressure and volume should stay consistant, regardless of what the temperature is. The temperature change should only affect the density. Since density = mass/volume, what really changed is the mass/amount of air. I tend to think the 1-2psi usual pressure drop is probably caused by the length of travel and other factors like leaks.

2. The actuator does not require vacuum to close. It requires a certain amount of pressure to open and keep it open, as soon as the pressure drops under that requirement, it's the spring that closes it, not vacuum. The mbc will prevent vacuum from reaching the actuator/wastegate in any case.

Again, I'm not challenging you or calling you out in any way. In fact, I'm only about 80% sure on what I said in part 1, let's make this a constructive discussion.

 

[Lilni]

nope pressure increases if the temperature increases. use the combined gas law. thank you conceptual chemistry

 

[oldman]

use the combined gas law.

It's been a while, review please.

 

[tstkl]

lets see... what is the equation.... i know there are 5 numbers, ones a constant....

nrt=pv

thats it i believe

number of molecules times some constant times temperature = pressure times volume...

as temp increases either n decreases, or p or v increases...also after the intercooler there is a small pressure loss as mentioned above... so there will be a difference, but im sure it will still work, if not use the stock unit til you get a mbc....

 

[skelly]

While I don't know any of the theoretical formulae, I think I can explain how it works:

You should know that convection is a process in which warm air rises through cooler air. It rises because the cooler air is more dense and it displaces the lesser dense air which has nowhere to go but "up". What makes warm air less dense is the fact that the molecules become excited and spread apart from one another as they gain energy from heat. The more space between the molecules, the less dense the mixture. It is this very spacial expansion between molecules that gives rise to pressure as temperature increases in a confined space.

You may recall that one of the properties of intercoolers as found in forced induction systems is that of "pressure loss". Pressure loss occurs for two reasons:

1) on a poorly selected/designed IC it occurs because the internal airflow passages are not sufficiently large to flow as much air as is being supplied. This results in a bottle-neck situation with high pressure building on the input side and lower pressure on the output side. If the output side were to open up into a static sized, sealed container, eventually the output side would indeed equalized to the pressure of the input side. But in a constantly moving forced induction system this situation never arises, so the situation is simply seen as a pressure reduction through the intercooler.

2) on a well selected/designed IC it occurs because the heat of the air being forced into the input side is being transferred to the walls of the internal passages and carried away by ambient air blowing by the external cooling surfaces. The resulting temperature reduction ends up yielding a pressure loss on the output side because the air is more dense at the output than it was at the input.

If you take these things and add them all up, you can in fact cheaply increase the boost of a turbocharged system by feeding the wastegate signal from an intercooled location rather than from a non-intercooled location because it allows the output side to come up to the full operating pressure required to open the wastegate. Otherwise the higher pressure of the compressor output will open the wastegate sooner.

This effect will be more or less pronounced on various intercooler setups with varying pressure loss through the intercooler. On my last project I was running a T04E through a Starion 16-fin intercooler and only saw 1/2PSI pressure loss through the intercooler, so there wasn't much to gain. But I have heard of some cars seeing 1-5PSI drop that would definitely benefit from this.

Ya dig?

- SK

 

[oldman]

Very nice reply. I've decided to dig up my college physic book, took me about an hour last night to find it , and after speaking to a friend of mine who is an expert on physics, this what I came up with which is pretty much what you just said.

pv=nrt

since volume (v) is constant, what is subject to change is pressure (p) and number of molecules (n).

In theory (what I've stated in #1), the pressure should stay the same and the only change should be n (amount of air). However, in a real life turbo situation things are not so simple. There are several things that will cause a pressure drop.

1. Intercooler's cooling capacity exceeds the flowing capcity (cfm) of the turbo causing pressure drop because the turbo is unable to pump in enough air or quickly enough to make up for the difference in in temperature.

2. The cfm of the turbo exceeds the cfm of the intercooler causing a bottle neck effect like you stated above.

In conclusion, the efficiency of the intercooler is not the only factor that determines the amount of pressure drop, the efficiency of the turbo plays a big role as well. One thing for sure though, you were right (on the subject of pressure drop anyway. ) and I was wrong. Good discussion.

 

[Kronic_420_Haze]

if i install a MBC then can i install everything the right way and not have to have the fitting?

 

[99gst_racer]

Yes, I agree; very good discussion.
I too have noticed that in the real world, many situations dont agree with theory.
I am currently tee'd into my BOV vac line for my wastegate pressure source. Tomorrow, I am going to pull my compressor cover and drill and tap it for a vac. fitting. This thread has sparked my curiousity as to if it will make any kind of noticable difference. I'll keep you guys posted.

 

[oldman]

if i install a MBC then can i install everything the right way and not have to have the fitting?

You should be fine even without a mbc with taking the pressure source from the BOV/intake hose, there is no need for you to tap a new hole on the J-pipe. Paul is just doing it cause he has nothing else better to do.

 

[ZachM31]

pv=nrt

nice to see someone using equations (the ideal gas law) that i learned in school... i learned it in chemistry though. maybe i should stop saying "when's this going to be used in real life" from now on.

 

[99gst_racer]

Paul is just doing it cause he has nothing else better to do.

 

[olmytsi]

I hate chemistry and all that gas law stuff so im not gonna read thru that stuff. So what is the conclusion here? Using the line t'd off the bov is bad or harmless?

 

[tstkl]

nice to see someone using equations (the ideal gas law) that i learned in school... i learned it in chemistry though. maybe i should stop saying "when's this going to be used in real life" from now on.

eh hem.... i said it first... , i dont care whatever

i believe we desided that its harmless....if anything it will help your proformance cuz its the actual psi going to the throttle body, not the psi the turbocharger is making...

 

[skelly]

I hate chemistry and all that gas law stuff so im not gonna read thru that stuff. So what is the conclusion here? Using the line t'd off the bov is bad or harmless?

I will never understand people who have an aversion to knowledge.

 

[steve]

Just keep in mind that people set their MBC based on boost gauge readings. So the notion of decreased temp or IC pressure drop pretty much fall out of the equation.

I don't like the long hose involved from the manifold to BOV to MBC.

Steve

 

[oldman]

Just keep in mind that people set their MBC based on boost gauge readings. So the notion of decreased temp or IC pressure drop pretty much fall out of the equation.

I don't like the long hose involved from the manifold to BOV to MBC.

Steve

I hate you but you're absolutely right.

 

[firebirdvert305]

these compressor outlet pipes really make a difference on stock piping? Will u see or feel any gain? Also if i swap to a 2g TB elbow as well...which piping would i need to use so my UICP will fit the elbow?