elistian

Just woundering what would actuall happen if your turbo manifold cracked other then leaking exhaust?? Would you loose boost??

Second question is why is it better for the exhaust to be hotter going into the turbo?? Like why do people get there manifold ceramic coated or wrapped in that wrapping to keep the heat in??? Wouldnt it be better to be cooler??

imported_zhu

The answer to your first question is yes you will loose boost. Beacuse its the exhaust gas that turns your turbo's compressor and with less exhaust gas, the turbo will not spin as fast and therefore not produce as much boost.

imported_b16turbohatch

as for the heat question the reason we wrap the manifold is because it gives off sooooo much heat and the inlet for the turbo where the air goes in is right next to it and you want that air as cold as possible.

TheModFather

hotter air takes up more room effectively making the turbo feel like MORE air is going through.... thus spooilng it faster!

cee_mon

100%...

On a side note:

DISCLAIMER
I dont know how true this is, but i heard that hotter gases travel fast and spool the turbo quicker if the heat is trapped inside.
Anyone confirm or discredit this, please post as iam wondering aswell.

scarlemthug

yes hotter air will spool the turbo faster because there is more enegry there. IF your manifold cracks you will loose pressure aswell you may have boost spiking awell depending on the size and location of the crack/hole.

bbarbulo

iTrader: (2)

hotter gasses do flow faster, so we can assume limited turbo volume (which it is) that it would create higher gas velocity and therefore faster spooling. how much faster I dunno....

on another note, i finally located my exhaust housing, and took it to HTC today to have it ceramic coated.

HAPPY

FYI Guys

... turbos are not winwheels...they do not spin on "air"

Turbo's are heat scavengers, and make boost do to the huge heat difference between the two sides of the turbine (one being hot and one being cold)

dingus88

^^WTF?? exhasut gasses spin the turbine wheel which then in turn spinns up the air to above atmospheric pressure etc.. Heat scavenger...??..lol

and your turbo will spool liek a dog and nto hold boost with a cracked manifold

dingus88

oh ya they call it the hot side cause it get's red hot (literally) from teh hot gasses and the cold side because it doesn't have 1800 degree's going threw it and it blows "colder air" if you will.

imported_ERTW

PV=nRT from the universal gas law... higher temperature gives you higher pressure, therefore higher gas velocity. if you cool the gasses, you lose volume and pressure, and those two are what you want to spin the turbine

dingus88

I think you guy's have the right idea but the wrong idea at the same time....the fact that the gases are hot dosent' move **** it's the fact that the piston is pushing the gases out at high velocity

bbarbulo

iTrader: (2)

werd.... it's the fact the gasses have a set path over the turbine that makes it build speed, and since it shared a common shaft on an oil bearing with the compressor side, the compressor is shaped so it sucks in fresh air and compresses it...

imported_zhu

http://www.beesandgoats.com/boostfaq/g2icturbo.html

HAPPY

You trying to laugh at my zhu? Nice site btw...it's good for someone with basic to no knowledge of a turbo system.

You boys need to read some more. I'll try to make this sound/read "simple"

In the absence of heat, turbos would not do their job. It is the heat in a turbo that creates two pressure systems. It is the difference in these two pressure systems that FORCES the air to want to move from the hot side (high pressure) to the cold side (low pressure) of the turbo (and then off to the intercooler and so on). It is this transfer of energy that is responsibe for spinning the shaft at great speeds.

Granted, it is the airflow from the head that is responsible for getting it all going, but the airflow is not intended to power the system, merely to act as a vehicle to get the heat in there.

So...I stand by my statemant that turbos are not pinwheels.

HAPPY

Oh, and someone brought up header wrap. Header wrap is intended to keep exhaust gas temps high heading to the turbo.

<sarcasm> No why would that be if you want cold air when it gets to the TB? Why keep the temp up? </sarcasm>

spazio10

The ideal gas law is P=(nRT)/V
thats awsome that we actually have some use for this chemistry crap eh?

if the turbo were placed further away from the heat source would the air not cool and slow down like that dumbass from utah with the turbo under the rear bumper.
this would create huge turbo lag with less response time. and poor efficiency.

bbarbulo

iTrader: (2)

ok... HAPPY I hear what you're saying. I understand what you're saying....

however, I don't 100% agree (but I do to a degree... turbo is better/more efficient )

but if that is as you say it is... then explain how a Paxton or Vortech supercharger works... the superchargers that are basically pulley-driven turbo compressors (so the exhaust side is replaced with a gear set and then belt driven).

HAPPY

Well, rather than using heat to generate crazy RPM, these blower systems use different pulleys diameters. You only need to think of your simple 10-speed bike to understand this one.

bbarbulo

iTrader: (2)

see, that's not right. heat is only a very small part of the equation. the majority of boost comes in fact from the exhaust pulsing over the blades. it's got little to nothing to do with the EGTs. Cuz what you're saying right now is the higher the EGT, the higher the boost pressure will be, which is not at all true. Boost pressure is dependant on exhaust volume/velocity. This is why equal length turbo headers are the bomb, cuz they keep the exhaust pulses (waves if you will) hitting the turbo at even intervals where as a log style would make it (and take the # of periods as the pause between pulses) .......1.3......4.2.......1.3......4.2..... and so on. Cuz the firing order is 1-3-4-2 and 3 and 2 are closest to the turbine, so their exhaust waves would reach it sooner since 1 and 4 have a longer path tho travel. Get what I mean... and equal length would make it ..1..3..4..2..1..3..4..2..1.. etc.... also, by what you're saying is that equal length headers would (b/c of their increased length) would be LESS efficient since they dissipate MORE heat than a smaller log manifold would... therefore that would be bad.

my example of the turbo to s/c comparison was to say... BOTH work the exact same way, except one uses an exhaust driven turbine to power the compressor, and the other uses a gearset to step up the speed from the pulley... neither has much at all do with the heat generated... heat is more or less an unfortunate byproduct of compressing any fluid. In fact, more of the heat in a turbo happens from compressing the air, than actually gets transferred from exhaust cuz the velocity is pretty high so any cu ft of air doesn't hang out in the turbo very long at all. In fact, most turbos move about say..... ~600ish cfm (cubic feet per minute) 600 cf/m /60 sec/min so that's 10 cu feet of air per second.