how many pounds of boost can a 7m handle??
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dubsupra209;1585475 said:
You heard wrong
just look at x-man's car. IIRC 30++ lbs of boost. All stock motor with 700++ HP.
dubsupra209;1585475 said:
Is the elevated air pressure supposed to break off a cam lobe? I don't know what that means.
The question is, how much boost can YOUR motor handle. Miles, etc etc and if its in good shape. Just remember, boost is different for different turbo's. 30 PSI on a small turbo might be the same as 20 on a huge turbo. Just an example.
629.63PSI. If you hit 629.64psi, 2 rods will break, one rod will evaporate, youll melt 3.7 pistons, put a dime size hole in the driver side of the block, 5 valves will shoot threw the valve covers, 2 will go threw the hood and the throttle plate will seize shut.
Be careful and happy boosting!
Be careful and happy boosting!
OneJArpus;1585489 said:
Not to discredit you or say you are wrong or anyone is really, but in my ignorance of the idea please enlighten me as I am only a logical person. Now I am not trying to be cynical or anything I just really am curious.
I have seen many times where people say a large turbo can give as much air on a lower psi as a small turbo. Now in my logical thinking that is not possible. I can see where the larger turbo will be spinning more slowly and give the same psi as a small turbo, lets say a large turbo at 100k rpms has 20psi on a 7mgte, a small turbo at 100k rpm will only give say 10 psi. Ok with that out of the way in logic. To think of what boost really is, its when air in pushed though a restriction or into a container that has volume. In our case the volume is a 7mgte. Now I dont really see where a large turbo vs a small turbo would matter. Now the one thing I can think of are the large turbo will be spinning slower and should have a lower velocity of air, but I dont think that should matter.
Now with all that said, here is what I am thinking would be the difference. Boost is built from air flow going to a restriction, in this case the restriction is the valves and cylinders. The air flows from the turbo through the ic system and into the intake then through the intake valves into the cylinders. The boost is measured on the intake where it is basically stored as it tries to make its way into past the valves. So with the air in the intake storing pressure I dont really see where the difference in the turbo matters, except the air velocity. Now the air velocity I would think would be faster through a smaller turbo, thinking that the faster spinning blades would move the air faster.
Now that velocity may be where the difference comes in. Air in a intercooler system gets hot not because the turbo heats up the air, but instead from the friction of the air compressing and friction between air and the intercooler and intake system. So faster air will be hotter making a difference in volume because cool air is more dense than hot air. But that is the only reason I see and it does make since but I dont know if its enough to explain this exact phenomenon.
X-man - 753 rwhp/589 rwtq - stock internals, gt42 @ 30 psi , 1000's, aem There ya go, stock cams and no porting. Just fuel, boost and a damn good tuner.
Not quite, but you're on the right track. I don't claim to a expert but, the higher PSI in the intake, the more air can be crammed into the cylinder when the valve drops.
So in essence, more boost = more air velocity = more pressure in the cylinder.
Size of the turbo depends on what you want the power band to be. Smaller turbo's, spool faster but sacrifices top end power as the turbo won't be able to keep the pressure up at high rpm's. Bigger spools slower but keeps power in the high rpm's.
And all this is relative to your particular intake and etc.
But, to the original question... "how many pounds of boost can a 7m handle??" It should be, "what boost can my particular 7m handle?"
Hope this helps
So in essence, more boost = more air velocity = more pressure in the cylinder.
Size of the turbo depends on what you want the power band to be. Smaller turbo's, spool faster but sacrifices top end power as the turbo won't be able to keep the pressure up at high rpm's. Bigger spools slower but keeps power in the high rpm's.
And all this is relative to your particular intake and etc.
But, to the original question... "how many pounds of boost can a 7m handle??" It should be, "what boost can my particular 7m handle?"
Hope this helps
FullNelson;1585627 said:
This doesn't mean that there cannot be pressure and flow at the same time, though.
The critical factor that you've left out of your thinking is temperature. A smaller turbo will move a certain mass of air, and cause a certain pressure at a certain temperature.metaphysico;1585599 said:
A larger turbo will move the SAME mass of air, however, it does so at a lower temperature, and therefore, a lower pressure.
This really is a simplistic view of how it works, but going in depth into the actual physics behind it is ... well, long and tedious. One of the guys with more patience might chime in and explain, but it's summer, a lot of those guys are out enjoying their car and won't be surfing much until this fall.
Nosechunks;1585545 said:
"Jonah Taylor Laugh HAHAHAHAHAHAH COUGH COUGH FLEM FLEMCOUGHHAHAHAHAFELEM HAHAHAHA BURP " !!!! That laugh is copy righted and don’t forget the V-Tech Sticker that will add the .01 lbs of boost to make it act like the flux capacitor to generate 1.21 Gigawatts to see some serious shit!!!
metaphysico;1585599 said:
To Expand for Grim..........
The difference between a larger and smaller turbo is the efficiency of the compressor wheel to move air threw the particular housing.
Most of the heat in the air discharged from a compressor housing is because the air is physically smaller in volume, not from the turbo being hot. Using 15PSI as a rounded atmospheric pressure, compressing air to 15 PSI would double its temperature from being smaller in volume alone. The reason for this is because there is now double the BTU's of heat contained in half the given volume of air thus making the temperature double whatever it was.
The rest of the heat is from the action of compressing, Nothing is 100% efficient. Turbochargers use centrifugal force to move air. Air has a mass, its little but it still has mass. When the compressor wheel turns the air is "flung" to the housing where it exits. The air drawn in is drawn in by filling the space left by the exiting of the "flung" air. This is the reason turbochargers suffer greatly from an inlet restriction. If theres no air to replace the "flung" air, there is no air to "fling". The Impeller speed will actually rise as there is no air in its way to slow it down, Think hand over a house vacuum hose.
When the compressor wheel is turning at a high rate of speed there is friction between the compressor wheel and the air, and the air and the compressor housing. This friction of the compressor wheel "Beating" the air threw the compressor housing also adds to the heat of the discharged air (action of compressing)
All turbos have an efficiency range. This range is where speed of the impeller and the pressure output of the air are matched and efficiently move threw the housing with the highest airflow VS heat generated ratio. The larger the turbo, the more air it can efficiently flow before the wheel speed or housing size create a restriction resulting in friction and heat.
Most all turbocharger flow rates are rated in Pounds/Minute . This is because CFM does not account for density. One Cubic Foot of air at 30 degrees F is much different then one Cubic Foot of air at 90 degrees F.
Carburetors can be rated in CFM because no matter what the ambient temperature (density), the same CFM (volume) will flow threw them at WOT.
The reason a larger turbo will make more power at a lower boost pressure is because the larger turbo will move more air more efficiently then a smaller turbo.
The Larger turbo will move 60LBs/Min of air into a motor at 20 psi, while a smaller turbo will move 50LBS/MIN of air into a motor at 20PSI.
The reason for this is the temperature of the air going into the intake manifold with the larger turbo will be 80 degrees F, and the temperature of the air going into the intake manifold with the smaller turbo will be 110 degrees F.
Thinking about that more will show since both turbos are creating the same boost pressure there is the same resistance to flow. Overall CFM (volume) to the intake manifold may be exactly the same between the two turbos. Since the temperature is different the density of the air is different therefor the Mass of air (and fuel) being consumed by the engine is different, thus the power output of the engine is different.
Its alot of physics and probably some thermodynamics in action. Its actually pretty cool when you think about it, Or maybe im just a nerd. :biglaugh:
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Like it has been stated, more psi doesn't always exactly translate to more power. A better question is "How much power can the 7M handle?", in which case the answer is how ever much you can afford. An even better question is "What do I need to make X amount of power?", or are you wondering how much a stock 7M can handle? A fresh one can put down 400hp at the wheels: http://7mpower.com/7m_buildup.shtml.
GrimJack;1585636 said:
Actually the last paragraph I wrote covered that. So my assumption was correct in that its just a air temperature change caused by the different turbos (taking out the factors of spool time and max spool velocity ect).
Thx for the description NoseChunks.