turbo intake explained?

[johnny2quick]

i'm trying to figure out how the intake system works on the '99 GST. can anyone point me to a good internet resource or explain this to me?

[96spyderman]

What info ya lookin for? It's design is pretty simple...
Define what you mean "how the intake system works on the '99 GST"
The basics are ... Air filter-MAFS-intake to turbo-lower intercooler pipe-Intercooler-upper intercooler pipe w/BOV-Throttle Body-Intake Manifold

[johnny2quick]

Originally Posted by 96spyderman

What info ya lookin for? It's design is pretty simple...
Define what you mean "how the intake system works on the '99 GST"
The basics are ... Air filter-MAFS-intake to turbo-lower intercooler pipe-Intercooler-upper intercooler pipe w/BOV-Throttle Body-Intake Manifold

that's something i can understand. i don't understand this: look at the pipe that goes from filter to turbo. it has anpther little pipe coming off of it twoard the BOV. it looks like this pipe is sending air from the turbo to the BOV, which would have air going in 2 directions in the same pipe:
1. from the filter to the turbo
2. from the turbo, back through that pipe, then to the little pipe.

that's what i dont get.

thanks

[96spyderman]

OK... the hose you are talking about is the BOV dump tube for the air that is relieved through the BOV.
OK when the boost is applied to your intake and you let off the gas that pressure needs somewhere to go.. thats what the BOV is for.. The air that has gone past the mass air flow sensor has been registered by the ecu... this is why the air is recirculated back into the intake before the turbo.
I have heard that if you vent this air into the atmosphere you throw off the air fuel ratio or something but others say it's fine.
Aside from the dump tube from the BOV there is 3 other hoses...1-- tube goes to the wastegate actuator solonoid, 2-- tube goes to evap canister, 3-- tube goes to valve cover for crankcase gases to be run through the engine for better emissions...blah blah
Hope this helps and anyone fill in the blanks or corrections if I was wrong...

[johnny2quick]

Originally Posted by 96spyderman

OK... the hose you are talking about is the BOV dump tube for the air that is relieved through the BOV.
OK when the boost is applied to your intake and you let off the gas that pressure needs somewhere to go.. thats what the BOV is for.. The air that has gone past the mass air flow sensor has been registered by the ecu... this is why the air is recirculated back into the intake before the turbo.
I have heard that if you vent this air into the atmosphere you throw off the air fuel ratio or something but others say it's fine.
Aside from the dump tube from the BOV there is 3 other hoses...1-- tube goes to the wastegate actuator solonoid, 2-- tube goes to evap canister, 3-- tube goes to valve cover for crankcase gases to be run through the engine for better emissions...blah blah
Hope this helps and anyone fill in the blanks or corrections if I was wrong...

perfect explanation. i understand that tube now. Now i just want to make sure i have the rest straight.

air goes...
through filter to intake tube
through intake tube to turbo intake
from turbo exhaust to upper IC pipe
through upper IC pipe to IC
through IC to lower IC pipe
through lower IC pipe to throttle body
through throttle body to intake manifold.

that right?
next question... I thought that the IC was there to cool the air down before the turbo becuase the cooler the air is, the denser it is, and that means there's more for the turbo to compress. so shouldn't the air flow be from the turbo exhaust to the throttle body?

[Igovert500]

No, the intercooler is there to 'recool' the air that the turbo has heated. The turbo has condensed quite a bit of air coming in, but in the process, it spins so fast that it gives off tremendous heat...so the IC cools the air that has gone through the turbo already and is heading to the throttle body.

Check this out for more info on it:
http://www.autospeed.com/cms/article.html?&A=0084


This has some helpful diagrams of the entire turbo setup(however it is for a 3000gt vr4, but it may still help in getting an idea how the air flows in your turbo setup).
http://www.rtec.ch/turbo_basics.html

[yoshimitsuspeed]

Originally Posted by johnny2quick

perfect explanation. i understand that tube now. Now i just want to make sure i have the rest straight.

air goes...
through filter to intake tube
through intake tube to turbo intake
from turbo exhaust to upper IC pipe
through upper IC pipe to IC
through IC to lower IC pipe
through lower IC pipe to throttle body
through throttle body to intake manifold.

that right?
next question... I thought that the IC was there to cool the air down before the turbo becuase the cooler the air is, the denser it is, and that means there's more for the turbo to compress. so shouldn't the air flow be from the turbo exhaust to the throttle body?

The only other thing I noticed is you got the IC pipes backwards.

air goes...
through filter to intake tube
through intake tube to turbo intake
from turbo exhaust to lower IC pipe
through lower IC pipe to IC
through IC to upper IC pipe
through upper IC pipe to throttle body
through throttle body to intake manifold.

Might come in handy when ordering parts or somethin.

[joemathews]

Originally Posted by johnny2quick

air goes...
through filter to intake tube
through intake tube to turbo intake
from turbo exhaust to upper IC pipe
through upper IC pipe to IC
through IC to lower IC pipe
through lower IC pipe to throttle body
through throttle body to intake manifold.

Yea, you have the upper and lower IC pipes reversed...think of the air as going clockwise if you are looking at the car from the front.

Also, the intake air goes into the turbo inlet, but NOT out the turbo exhaust. The exhaust housing is completely separate from the intake housing.



Here are two turbos--you see the shiny silver sides on the left are the intake sides, the darker sides on the right are the exhaust sides. The housings are completely separate except for having a shaft between them that connects the two turbine wheels.

So, the intake air enters the compressor side of the turbo through the inlet, and exits through the outlet at the lower intercooler pipe Remember that this is all happening because exhaust gas is spinning the hell out of the other side of the turbo!

[johnny2quick]

awesome guys. i think this answers all my turbo questions/ for now
also, does the intake tube have fins inside of it where the MAFS is? i know it does on my celica. i assume if it doesn't, then aftermarket intake manufacturers prolly don't put it in there.

[johnny2quick]

Therefore the bigger the boost of the compressor the more the wastegate opens and the less boost will be produced. But less boost means closing the wastegate more and therefore more boost will be produced

can someone explain this in a little more detail? this sounds like it's going in a direction that might make sense, but isn't there yet

[spyderturbo007]

Originally Posted by johnny2quick

Therefore the bigger the boost of the compressor the more the wastegate opens and the less boost will be produced. But less boost means closing the wastegate more and therefore more boost will be produced

can someone explain this in a little more detail? this sounds like it's going in a direction that might make sense, but isn't there yet

I am kind of confused as to what you are saying, but I will explain what I think I understand about the wastgate part of the turbo. Ok, the exhaust gas enters the "hot side" of the turbo after exiting the combustion chambers. It spins the compressor wheel on the "hot side" which is attached to the compressor wheel on the "cold side", or intake side. The spinning compressor wheel pressurizes the intake air as it spins, thereby creating boost. The exhaust gasses, after spinning the "hot side" exit through the o2 housing. The turbo is a positive feedback device, i.e. the faster is spins the more boost it makes, the more exhaust gasses are produced, the more boost it makes, etc. Until everything flys apart. In order to regulate the amount of boost produced there is a wastgate to allow extra exhaust gasses to bypass the "hot side of the turbo" thereby controlling the boost pressure. You have to think, that at 6000 rpm, there is a lot of exhaust gas produced compaired to 1000 rpms. If all of that exhaust gas was allowed to pass over the "hot side" compressor wheel, I have this funny feeling something bad would happen .

So to summarize: When the turbo builds a preset amount of boost the pressure from that boost opens the wastegate and regulates the amount of exhaust gas passing over the "hot side" compressor wheel. This is why an MBC works, it is a ball and spring (normally) that is placed between the BOV and the wastgate. It "tricks" the wastgate into thinking that there is less pressure than there really is, thereby delaying the opening of the wastegate. So bada bing.....more boost. I hope this helps and I hope I didn't mess anything up!

[johnny2quick]

thanks spyderturbo

[spyderturbo007]

No problem, I hope that helped!!

[johnny2quick]

with the stock system, i understand the BOV to direct extra pressure (from the throttle closing) back into the intake because the MAFS has already metered that air, so the engine needs it to run correctly.

what if the MAFS was moved to the UICP, just before the intake manifold, and the BOV actually blew the extra air off into the atmosphere?

what effects would this have on the engine in terms of HP and A/F ratio?
also, would this make the engine work harder to create boost or would it make it easier?

thanks

[BoostedSpyder]

that would be a MAF, not a MAS.

the MAF is mounted behind the BOV and has the ability to meter massive flows of air, compressed with a 'hot wire'. the wire is hot and based on the amount of air needed to 'carry' off heat, it can calculate airflow.

placing the MAS in that spot would disrupt the airflow so much that it would be like stuffing the pipe with cotton.

AFR would be calculated on what the ECU sees from the air metering source.

a MAF is less restrictive, so theoreticaly you can pull more air = more HP.

i have been finding out that you can hack the 2g MAF to death practiacaly, and compensate with the SAFC [or any fuel tuning/logging setup], so my MAF thoughts were squished.