looking for 300+ hp
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at 8psi, almost every turbo on one of these cars is going to be operating with the wastegate partially open.
The wastegate partially open implies that the exhaust gas flow from the motor exceeds that necessary to generate 8psi of pressure.
With a crappier flowing charge pipe / throttlebody setup, the wastegate will simply open a little less (making the turbo work harder) to reach similar pressure levels.
For a naturally aspirated motor, there is no turbo. A scavenging header can help make good use of exhaust pulses. A set of tuned ITBs or an intake tuned to a specific frequency / RPM can help stuff more air in the motor. There isn't a magic air pump to cram more air in there when you fuck up some minor detail like there is with a turbo car.
Turbos aren't free - they rob the motor of VE in order to spool and feed air. You forget that exhaust gases bypassed by a WASTEgate are exactly that - wasted energy that COULD be easily used to work the turbo a little harder in the case of crappy flowing stuff.
That is a more clear and concrete example of what I spoke of above.
I think I am speaking to ROI / point of diminishing returns / cost effectiveness more than absolute theoretical best thing. If given the choice of spending $300 on rods or $300 on a bling spec intake manifold, I'm going to take the rods and crank the boost up twice as high as it was before. If I had a massively ported head, I'd want to match it with a higher flowing manifold. (I'm trading my B18A manifold for a Skunk2 when I put the ported head on)
It might be a good study to examine the flow of stock intake manifolds vs. stock heads...
The wastegate partially open implies that the exhaust gas flow from the motor exceeds that necessary to generate 8psi of pressure.
With a crappier flowing charge pipe / throttlebody setup, the wastegate will simply open a little less (making the turbo work harder) to reach similar pressure levels.
For a naturally aspirated motor, there is no turbo. A scavenging header can help make good use of exhaust pulses. A set of tuned ITBs or an intake tuned to a specific frequency / RPM can help stuff more air in the motor. There isn't a magic air pump to cram more air in there when you fuck up some minor detail like there is with a turbo car.
Turbos aren't free - they rob the motor of VE in order to spool and feed air. You forget that exhaust gases bypassed by a WASTEgate are exactly that - wasted energy that COULD be easily used to work the turbo a little harder in the case of crappy flowing stuff.
That is a more clear and concrete example of what I spoke of above.
I think I am speaking to ROI / point of diminishing returns / cost effectiveness more than absolute theoretical best thing. If given the choice of spending $300 on rods or $300 on a bling spec intake manifold, I'm going to take the rods and crank the boost up twice as high as it was before. If I had a massively ported head, I'd want to match it with a higher flowing manifold. (I'm trading my B18A manifold for a Skunk2 when I put the ported head on)
It might be a good study to examine the flow of stock intake manifolds vs. stock heads...
Joseph Davis
Member
Wrong.
Your point is not well taken, because it is not what it seems.
In turbocharging, you manipulate pressure differential to acheive your desired cfm - cfm *is* horsepower. As long as you are on your compressor's efficiency island, it cares not one whit if you make your desired cfm at 8 psi or 12 psi, and neither does your engine.
Flow restrictions bolted to engine A result in less power - a good example of this is a log manifold versus something with a long, smoothly transitioned collector. Especially given how runners on the log manifold don't evacuate each cylinder evenly... taking average AFR for all four cylinders results in leaning one cylinder out when it comes time to push some limits. Is this due to the amount of boost you run? No, but the amount of boost you run may be a sympton of just such a thing happening if you don't have your head removed from your ass, and can't look at the big picture.
There's a lot of stuff going on here; how cam timing combined with manifold pressure manipulate dynamic CR... the same thing with cam timing and TIP on cylinder evacuation... etc... that influences your net result. You can say truthfully, and with much applause from me, that the setup on GSR B makes more power more reliably than other setups for that engine, but you cannot say higher boost numbers are bad to sell more headwork and fancy valvetrain. There are loopholes to that statement in practice, in day to day application, and in the physics dictating how things work behind the dyno plots and PR releases.
Bottom line, if my bottom end is capable of supporting X amount of power, I can achieve it with a stock unported head just as well as a fancy ported item. I have to run higher boost to do so. So what?
Brad Z (sound familiar?) told me the current record for a stock LS head is 850 whp. It was, of course, perched on top of a bottom end that could hold it. That right there sold me on not worrying about flow numbers or boost numbers (or $2000+ dropped into your cylinder head) as long as my flow is balanced, and what I bolt to the engine is well thought out.
Citizen_Insane
Senior Member
You also have to realize though, that running more PSI in exchange for a poorly flowing head is putting unnessisary strain on the whole system.
you missed the man's point.
CFM (Airflow) = power
It doesn't matter if you sit at 8psi and 500 CFM or 12psi and 500 CFM - as long as you're not pushing your turbo outside of its efficiency range, you'll make the same amount of power with the same amount of airflow.
Power is stress.
For example: my LS motor will be under more stress at 8psi with the ported head than 8psi with the stock head because the ported head will flow more air, and airflow NOT pressure level = power
CFM (Airflow) = power
It doesn't matter if you sit at 8psi and 500 CFM or 12psi and 500 CFM - as long as you're not pushing your turbo outside of its efficiency range, you'll make the same amount of power with the same amount of airflow.
Power is stress.
For example: my LS motor will be under more stress at 8psi with the ported head than 8psi with the stock head because the ported head will flow more air, and airflow NOT pressure level = power
saturn_boy96
88 C1V1C 53D4N DR1V3R
so basically you're all saying find the biggest turbo you can afford and run the lowest boost setting possible and be happy with that. 
MikeBergy
Blah blah blah....
big turbos = lots of lag. Plus, at lower boost levels, the turbos are not operating in their peak efficiency ranges. Just look at the compressor map of the turbo, see if the airflow and psi is what you are looking for. If not, then look for a different turbo, it's called planning ahead. Just throwing parts together will not necessarily help your motor out. You need to size your system and tailor them to your expectations of the motor.
saturn_boy96
88 C1V1C 53D4N DR1V3R
turning up the psi will also increase the amount heat generated by compressing the intake air. this inturn will bring you closer to the detonation threshold which will have to be countered with more fuel.
i think what jeff is saying is that two motors with the same turbos can make extremely different amounts of power when not tuned correctly and that making more power does not necessarily mean more wear on the motor.
obviously a turbo motor that is running very lean will not make as much power and will break much faster.
yes, and we are trying to correct him. power == wear.
granted if one of the motors is not tuned for shit... its will probably blow first. but he said that motor A and B both tuned.
i'm really not trying to be argumentative, but just trying to correct some misinformation. and i understand how to read compressor maps, i understand that you need to be running a turbo in its efficiency range, we are assuming that both turbo A and B are running efficiently.
and no one said that you should go out and buy the biggest turbo you can and run low boost on it. i don't see how you are getting that from this thread. here we are discussing power vs psi vs wear.
saturn_boy96
88 C1V1C 53D4N DR1V3R
i was reading into what you were saying, basically make the most power at the lowest psi which you guys are saying will cause the lowest wear, right?
no, thats what the IB guy is saying. the rest of us are saying that the PSI doesn't really matter as long as you are in the turbo's effeciency range. the POWER OUTPUT is what wears the motor. doesn't matter if you are running 8psi on a bigger turbo or 12psi on a smaller turbo... if both are making 300hp, and both are tuned and running effeciently, they will have the same wear.
saturn_boy96
88 C1V1C 53D4N DR1V3R
i think what he was originally saying is that with the right parts and right tuning you can make substantiallly more power without anymore wear on your motor.
he is saying that by being able to run your motor at lower boost levels and make the same amount of power your motor will last longer.
That was a feeble attempt at an argument saturnboy.
boost levels have shit to do with motors lasting longer. As long as your turbo is in its efficiency range, you are golden. Engine forces correlate with engine failure, and engine forces are directly related to power output. There is no lasting longer from lower boost levels if power is not equal too.
boost levels have shit to do with motors lasting longer. As long as your turbo is in its efficiency range, you are golden. Engine forces correlate with engine failure, and engine forces are directly related to power output. There is no lasting longer from lower boost levels if power is not equal too.
power is power. boost is a useless number to anything other than your map sensor.
wether its 50 psi to get you 200 whp or 5 psi, the motor is still seeing the same power- and power is what breaks the parts.
now, the 50 psi is un feasable, cuz its just throwing in uber amounts of heat.
i'm all for large turbo + lag + lower boost.
its a cooler charge, its more streetable... and you will keep decent highway mileage, cuz you won't be in boost at 65 mph in 5th gear
wether its 50 psi to get you 200 whp or 5 psi, the motor is still seeing the same power- and power is what breaks the parts.
now, the 50 psi is un feasable, cuz its just throwing in uber amounts of heat.
i'm all for large turbo + lag + lower boost.
its a cooler charge, its more streetable... and you will keep decent highway mileage, cuz you won't be in boost at 65 mph in 5th gear
liquid00meth
Senior Member
I agree with the CFM guys....
The one way to judge how much force is on your engine is to simply look at how much air/fuel is exploding in the cylinder. Regardless of any externally measured numbers, or the psi, or the flow of the pipes, all you simply have to do is look at how much fuel is combusting. More fuel = more force, less fuel = less force.
So, at any given time, and given that the car is tuned perfectly, the amount of CFMs that you push into the cylinder on any given intake stroke will give you an accurate representation of the forces on your parts. (which will all quickly change with RPM, and which also can be affected by the static compression of the motor). But lets not be nit pickey about it. I think it's settled that the CFMs are where to look.
The one way to judge how much force is on your engine is to simply look at how much air/fuel is exploding in the cylinder. Regardless of any externally measured numbers, or the psi, or the flow of the pipes, all you simply have to do is look at how much fuel is combusting. More fuel = more force, less fuel = less force.
So, at any given time, and given that the car is tuned perfectly, the amount of CFMs that you push into the cylinder on any given intake stroke will give you an accurate representation of the forces on your parts. (which will all quickly change with RPM, and which also can be affected by the static compression of the motor). But lets not be nit pickey about it. I think it's settled that the CFMs are where to look.
Import Builders
Senior Member
all I have is one thing to say, because its obvious I can't change some people's minds on many topics.
Whoever says, and I mean whoever...that using a smaller turbo and boosting more to make 300 WHP is better than using a larger turbo boosting less and making 300 WHP is better is flat out:
insane. and wrong. ( no offense guys)
And the motor boosting higher is wearing more than the motor boosting less making THE SAME POWER>
BECAUSE:
It generates more HEAT. Heat causes wear, big time.
So I conclude, that a motor making 375 WHP with 10 PSI is wearing less and lasting longer than another motor making ONLY 300 WHP boosting 15 PSI.
(at the same compression level) we are talking about using the same pistons in both motors.
The less boosted, more powerful motor is going to wear less.
Its people that say otherwise that are really spreading misinformation. More pressure=more heat. more heat=more wear more wear=rebuild sooner.
I am not sure who is going to argue more heat equals more wear and tear. But I guarantee people will.
Thats why we have republicans and democrats, for comparison..(example) They are never going to agree on some things, even when the facts completely support 1 side.
more boost with same compression motor = more heat.
With everything being equal, I believe this is a scientific fact.
I argue the facts, or try to. So let me know if there are any questions. Looks like I have to write more. That turbo article was like 11 pages typed! and yeah, I understand, there is information left out thats somewhat important.
its going to go in my book
A full book on everything I learned. From tuning, to breaking in motors, to pistons to turbo's.
Thanks for the input guys, and thanks ndogg, I will be more clear next time.
Whoever says, and I mean whoever...that using a smaller turbo and boosting more to make 300 WHP is better than using a larger turbo boosting less and making 300 WHP is better is flat out:
insane. and wrong. ( no offense guys)
And the motor boosting higher is wearing more than the motor boosting less making THE SAME POWER>
BECAUSE:
It generates more HEAT. Heat causes wear, big time.
So I conclude, that a motor making 375 WHP with 10 PSI is wearing less and lasting longer than another motor making ONLY 300 WHP boosting 15 PSI.
(at the same compression level) we are talking about using the same pistons in both motors.
The less boosted, more powerful motor is going to wear less.
Its people that say otherwise that are really spreading misinformation. More pressure=more heat. more heat=more wear more wear=rebuild sooner.
I am not sure who is going to argue more heat equals more wear and tear. But I guarantee people will.
Thats why we have republicans and democrats, for comparison..(example) They are never going to agree on some things, even when the facts completely support 1 side.
more boost with same compression motor = more heat.
With everything being equal, I believe this is a scientific fact.
I argue the facts, or try to. So let me know if there are any questions. Looks like I have to write more. That turbo article was like 11 pages typed! and yeah, I understand, there is information left out thats somewhat important.
its going to go in my book
A full book on everything I learned. From tuning, to breaking in motors, to pistons to turbo's.Thanks for the input guys, and thanks ndogg, I will be more clear next time.
MikeBergy
Blah blah blah....
Acknowledging that all other things being eqaul, I'd like to know how a less boosted engine is going to make more power.
Psi = Psi, measured at the manifold. It doesn't care if there is a small turbo or a giant one, psi is psi. You increase the psi, you are going to flow more air into the motor, all other things being equal, period, until you reach the flow limits of your motor. There is no way that a less boosted motor is going to make more power than a more boosted motor, all other things being equal. If you have come across such a case, I'd like to know. And you build an engine to handle a certain power rating, not boost level. And I am talking a tuned motor, all detonation issues aside.
Import Builders
Senior Member
euqal block wise and head wise. Not turbo size.
Turbo size different, different PSI will make different power.
Turbo size different, different PSI will make different power.
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