Question for an engine guru
11-13-2004, 04:08 PM
#1
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Question for an engine guru
I hear that a turbo will be coming out soon. But I am confused. The manual 8 has 159 ft lbs of torque. If the turbo is added will the torque change aswell. I would assume it would but I don't know much about engines. I can tell you the type of car by looking a headlight and stuff but I am clueless about engines. :D
11-13-2004, 04:35 PM
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LOL. Hehe I guess we have to start with the basics. HP is a function of torque * RPM / 5252. How do you make HP? You increase the torque, or you design the engine to flow more air so it can maintain or create more torque into the higher RPMS. If you make 150 torque at 3000 RPM and can still make 150 torque at 10,000 RPM you are making 85HP at 3000RPM and 285 HP at 10,000 RPM. When you add a turbo you are forcing air into the engine, say your turbo is set for 1.0Bar which is about atmospheric pressure, all things being perfect you are effectively doubling how much air the engine is intaking so basically you are doubling your power (which we generally measure in torque).
Now because of the way a turbo operates, it wont reach its full boost until the exhaust gases are powerful enough to provide it with the ability to force that 1.0 bar of pressure into the engine. Say the point that your turbo reaches 1.0Bar of boost is 3000RPM, based on what I said above, you will be doubling your power, so twice as much torque at the same RPM. Now you are making 300 lb/ft of torque at 3000RPM, using the same formula you are now making 171HP at 3000RPM. Now what will happen is as the RPMS of the engine increase, if you have a very efficient engine in the high RPMs (like the renesis) by 10,000RPM with perfect tuning of all the intake and exhaust runners, porting, etc. you can maintain the same power, however this is where things get complicated since turbo sizing, efficiency, pressure drop, ecu tuning, the ports and intake manifold/exhaust manifold obviously arent all designed perfectly so... if your engine did maintain that 300lb/ft of torque to 10,000RPM thats 572HP
What you were probably thinking is that since a turbo wont be providing full boost till the higher RPM's it would only increase the torque a bit in the higher RPMS. In a engine designed for power in the lower RPMS and not well tuned for the higher RPMS you migh have something more like 200lb ft of torque by 4000RPM dropping off to 150lb/ft of torque by redline, by adding the turbo (a small one) the max torque mgiht be about the same, but instead of the torque dieing off the engine is getting more air to redline thereby keeping the torque around 200lb ft just dropping off slightly, instead of dropping drastically. So if the engine makes 200lb ft of torque at 4000RPM, you are making 152HP at 4000RPM, however if it drops off to 150 by 10,000rpm you have 285HP, so even though your torque went down, you are still making more HP because of the higher RPM. If the turbo maintains the torque instead of dropping off and you have 200lb/ft of torque you are making 380HP at the same RPM but the torque never increased beyond the max torque.
Story in short: You can increase the HP of the engine with a turbo without the max torque ever increasing, however this is pretty rare, and in the case of the renesis the max torque will most likely be increased greatly with a properly sized turbocharger.
Using 10,000RPM as a figure might not be the best to use since most engines redline around 6000-7000RPM but the Renesis is capable of 10,000RPM so with proper tuning etc you have the starting point for something amazing.
Now because of the way a turbo operates, it wont reach its full boost until the exhaust gases are powerful enough to provide it with the ability to force that 1.0 bar of pressure into the engine. Say the point that your turbo reaches 1.0Bar of boost is 3000RPM, based on what I said above, you will be doubling your power, so twice as much torque at the same RPM. Now you are making 300 lb/ft of torque at 3000RPM, using the same formula you are now making 171HP at 3000RPM. Now what will happen is as the RPMS of the engine increase, if you have a very efficient engine in the high RPMs (like the renesis) by 10,000RPM with perfect tuning of all the intake and exhaust runners, porting, etc. you can maintain the same power, however this is where things get complicated since turbo sizing, efficiency, pressure drop, ecu tuning, the ports and intake manifold/exhaust manifold obviously arent all designed perfectly so... if your engine did maintain that 300lb/ft of torque to 10,000RPM thats 572HP
What you were probably thinking is that since a turbo wont be providing full boost till the higher RPM's it would only increase the torque a bit in the higher RPMS. In a engine designed for power in the lower RPMS and not well tuned for the higher RPMS you migh have something more like 200lb ft of torque by 4000RPM dropping off to 150lb/ft of torque by redline, by adding the turbo (a small one) the max torque mgiht be about the same, but instead of the torque dieing off the engine is getting more air to redline thereby keeping the torque around 200lb ft just dropping off slightly, instead of dropping drastically. So if the engine makes 200lb ft of torque at 4000RPM, you are making 152HP at 4000RPM, however if it drops off to 150 by 10,000rpm you have 285HP, so even though your torque went down, you are still making more HP because of the higher RPM. If the turbo maintains the torque instead of dropping off and you have 200lb/ft of torque you are making 380HP at the same RPM but the torque never increased beyond the max torque.
Story in short: You can increase the HP of the engine with a turbo without the max torque ever increasing, however this is pretty rare, and in the case of the renesis the max torque will most likely be increased greatly with a properly sized turbocharger.
Using 10,000RPM as a figure might not be the best to use since most engines redline around 6000-7000RPM but the Renesis is capable of 10,000RPM so with proper tuning etc you have the starting point for something amazing.
Last edited by Kari; 11-13-2004 at 04:40 PM.
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11-13-2004, 06:30 PM
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Originally Posted by Kari
LOL. Hehe I guess we have to start with the basics. HP is a function of torque * RPM / 5252. How do you make HP? You increase the torque, or you design the engine to flow more air so it can maintain or create more torque into the higher RPMS. If you make 150 torque at 3000 RPM and can still make 150 torque at 10,000 RPM you are making 85HP at 3000RPM and 285 HP at 10,000 RPM. When you add a turbo you are forcing air into the engine, say your turbo is set for 1.0Bar which is about atmospheric pressure, all things being perfect you are effectively doubling how much air the engine is intaking so basically you are doubling your power (which we generally measure in torque).
Now because of the way a turbo operates, it wont reach its full boost until the exhaust gases are powerful enough to provide it with the ability to force that 1.0 bar of pressure into the engine. Say the point that your turbo reaches 1.0Bar of boost is 3000RPM, based on what I said above, you will be doubling your power, so twice as much torque at the same RPM. Now you are making 300 lb/ft of torque at 3000RPM, using the same formula you are now making 171HP at 3000RPM. Now what will happen is as the RPMS of the engine increase, if you have a very efficient engine in the high RPMs (like the renesis) by 10,000RPM with perfect tuning of all the intake and exhaust runners, porting, etc. you can maintain the same power, however this is where things get complicated since turbo sizing, efficiency, pressure drop, ecu tuning, the ports and intake manifold/exhaust manifold obviously arent all designed perfectly so... if your engine did maintain that 300lb/ft of torque to 10,000RPM thats 572HP
What you were probably thinking is that since a turbo wont be providing full boost till the higher RPM's it would only increase the torque a bit in the higher RPMS. In a engine designed for power in the lower RPMS and not well tuned for the higher RPMS you migh have something more like 200lb ft of torque by 4000RPM dropping off to 150lb/ft of torque by redline, by adding the turbo (a small one) the max torque mgiht be about the same, but instead of the torque dieing off the engine is getting more air to redline thereby keeping the torque around 200lb ft just dropping off slightly, instead of dropping drastically. So if the engine makes 200lb ft of torque at 4000RPM, you are making 152HP at 4000RPM, however if it drops off to 150 by 10,000rpm you have 285HP, so even though your torque went down, you are still making more HP because of the higher RPM. If the turbo maintains the torque instead of dropping off and you have 200lb/ft of torque you are making 380HP at the same RPM but the torque never increased beyond the max torque.
Story in short: You can increase the HP of the engine with a turbo without the max torque ever increasing, however this is pretty rare, and in the case of the renesis the max torque will most likely be increased greatly with a properly sized turbocharger.
Using 10,000RPM as a figure might not be the best to use since most engines redline around 6000-7000RPM but the Renesis is capable of 10,000RPM so with proper tuning etc you have the starting point for something amazing.
Now because of the way a turbo operates, it wont reach its full boost until the exhaust gases are powerful enough to provide it with the ability to force that 1.0 bar of pressure into the engine. Say the point that your turbo reaches 1.0Bar of boost is 3000RPM, based on what I said above, you will be doubling your power, so twice as much torque at the same RPM. Now you are making 300 lb/ft of torque at 3000RPM, using the same formula you are now making 171HP at 3000RPM. Now what will happen is as the RPMS of the engine increase, if you have a very efficient engine in the high RPMs (like the renesis) by 10,000RPM with perfect tuning of all the intake and exhaust runners, porting, etc. you can maintain the same power, however this is where things get complicated since turbo sizing, efficiency, pressure drop, ecu tuning, the ports and intake manifold/exhaust manifold obviously arent all designed perfectly so... if your engine did maintain that 300lb/ft of torque to 10,000RPM thats 572HP
What you were probably thinking is that since a turbo wont be providing full boost till the higher RPM's it would only increase the torque a bit in the higher RPMS. In a engine designed for power in the lower RPMS and not well tuned for the higher RPMS you migh have something more like 200lb ft of torque by 4000RPM dropping off to 150lb/ft of torque by redline, by adding the turbo (a small one) the max torque mgiht be about the same, but instead of the torque dieing off the engine is getting more air to redline thereby keeping the torque around 200lb ft just dropping off slightly, instead of dropping drastically. So if the engine makes 200lb ft of torque at 4000RPM, you are making 152HP at 4000RPM, however if it drops off to 150 by 10,000rpm you have 285HP, so even though your torque went down, you are still making more HP because of the higher RPM. If the turbo maintains the torque instead of dropping off and you have 200lb/ft of torque you are making 380HP at the same RPM but the torque never increased beyond the max torque.
Story in short: You can increase the HP of the engine with a turbo without the max torque ever increasing, however this is pretty rare, and in the case of the renesis the max torque will most likely be increased greatly with a properly sized turbocharger.
Using 10,000RPM as a figure might not be the best to use since most engines redline around 6000-7000RPM but the Renesis is capable of 10,000RPM so with proper tuning etc you have the starting point for something amazing.
11-13-2004, 10:22 PM
#6
Turbos blow!!
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Kari. Thank you. I did understand the majority of what you said. I am still new to the engine part of cars. I want a turbo but I don't want to void any type of warranty. I want Mazda to make the 8 with the turbo. However that might not happen. I now understand how turbo and torque go hand and hand. Thanks a lot. I appreciate it. You gave excellent info for me. Anytime I have a question I will come to you. Again thank you
11-14-2004, 11:23 AM
#8
Mentalhealth is overrated
Originally Posted by Kari
LOL. Hehe I guess we have to start with the basics. HP is a function of torque * RPM / 5252. How do you make HP? You increase the torque, or you design the engine to flow more air so it can maintain or create more torque into the higher RPMS. If you make 150 torque at 3000 RPM and can still make 150 torque at 10,000 RPM you are making 85HP at 3000RPM and 285 HP at 10,000 RPM. When you add a turbo you are forcing air into the engine, say your turbo is set for 1.0Bar which is about atmospheric pressure, all things being perfect you are effectively doubling how much air the engine is intaking so basically you are doubling your power (which we generally measure in torque).
Now because of the way a turbo operates, it wont reach its full boost until the exhaust gases are powerful enough to provide it with the ability to force that 1.0 bar of pressure into the engine. Say the point that your turbo reaches 1.0Bar of boost is 3000RPM, based on what I said above, you will be doubling your power, so twice as much torque at the same RPM. Now you are making 300 lb/ft of torque at 3000RPM, using the same formula you are now making 171HP at 3000RPM. Now what will happen is as the RPMS of the engine increase, if you have a very efficient engine in the high RPMs (like the renesis) by 10,000RPM with perfect tuning of all the intake and exhaust runners, porting, etc. you can maintain the same power, however this is where things get complicated since turbo sizing, efficiency, pressure drop, ecu tuning, the ports and intake manifold/exhaust manifold obviously arent all designed perfectly so... if your engine did maintain that 300lb/ft of torque to 10,000RPM thats 572HP
What you were probably thinking is that since a turbo wont be providing full boost till the higher RPM's it would only increase the torque a bit in the higher RPMS. In a engine designed for power in the lower RPMS and not well tuned for the higher RPMS you migh have something more like 200lb ft of torque by 4000RPM dropping off to 150lb/ft of torque by redline, by adding the turbo (a small one) the max torque mgiht be about the same, but instead of the torque dieing off the engine is getting more air to redline thereby keeping the torque around 200lb ft just dropping off slightly, instead of dropping drastically. So if the engine makes 200lb ft of torque at 4000RPM, you are making 152HP at 4000RPM, however if it drops off to 150 by 10,000rpm you have 285HP, so even though your torque went down, you are still making more HP because of the higher RPM. If the turbo maintains the torque instead of dropping off and you have 200lb/ft of torque you are making 380HP at the same RPM but the torque never increased beyond the max torque.
Story in short: You can increase the HP of the engine with a turbo without the max torque ever increasing, however this is pretty rare, and in the case of the renesis the max torque will most likely be increased greatly with a properly sized turbocharger.
Using 10,000RPM as a figure might not be the best to use since most engines redline around 6000-7000RPM but the Renesis is capable of 10,000RPM so with proper tuning etc you have the starting point for something amazing.
Now because of the way a turbo operates, it wont reach its full boost until the exhaust gases are powerful enough to provide it with the ability to force that 1.0 bar of pressure into the engine. Say the point that your turbo reaches 1.0Bar of boost is 3000RPM, based on what I said above, you will be doubling your power, so twice as much torque at the same RPM. Now you are making 300 lb/ft of torque at 3000RPM, using the same formula you are now making 171HP at 3000RPM. Now what will happen is as the RPMS of the engine increase, if you have a very efficient engine in the high RPMs (like the renesis) by 10,000RPM with perfect tuning of all the intake and exhaust runners, porting, etc. you can maintain the same power, however this is where things get complicated since turbo sizing, efficiency, pressure drop, ecu tuning, the ports and intake manifold/exhaust manifold obviously arent all designed perfectly so... if your engine did maintain that 300lb/ft of torque to 10,000RPM thats 572HP
What you were probably thinking is that since a turbo wont be providing full boost till the higher RPM's it would only increase the torque a bit in the higher RPMS. In a engine designed for power in the lower RPMS and not well tuned for the higher RPMS you migh have something more like 200lb ft of torque by 4000RPM dropping off to 150lb/ft of torque by redline, by adding the turbo (a small one) the max torque mgiht be about the same, but instead of the torque dieing off the engine is getting more air to redline thereby keeping the torque around 200lb ft just dropping off slightly, instead of dropping drastically. So if the engine makes 200lb ft of torque at 4000RPM, you are making 152HP at 4000RPM, however if it drops off to 150 by 10,000rpm you have 285HP, so even though your torque went down, you are still making more HP because of the higher RPM. If the turbo maintains the torque instead of dropping off and you have 200lb/ft of torque you are making 380HP at the same RPM but the torque never increased beyond the max torque.
Story in short: You can increase the HP of the engine with a turbo without the max torque ever increasing, however this is pretty rare, and in the case of the renesis the max torque will most likely be increased greatly with a properly sized turbocharger.
Using 10,000RPM as a figure might not be the best to use since most engines redline around 6000-7000RPM but the Renesis is capable of 10,000RPM so with proper tuning etc you have the starting point for something amazing.
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11-15-2004, 11:17 AM
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So Kari, a turbo makes it, like, go faster, yeah? :D
But seriously...
You can also think of power as a measure of how quickly you are delivering the torque. Obviously, more torque (push) in a shorter time means the car will accelerate faster.
So for better performance you can either have more shove, period - which will be a higher torque figure. Or you can have the same about of shove delivered over a shorter period of time - which will be a higher power figure.
Obviously if you do both you have a monster - big Ferraris have > 400lb-ft AND > 500bhp.
The other thing to consider in all this is gearing - you can use gearing to convert big power into the feel of big torque, at the expense of revs. If you are geared to "fake" big torque you need more revs to reach a high speed.
This is the secret of the RX8 (and the S2000)... it has "only" 130some lb-ft but it's delivered through a short gearbox. So, it outperforms a lot of cars with 200+ torque figures. Those other cars would have peak power at 5-6k revs rather than 8-9. This is why the 8 can -almost- keep up with a 350 even though the gap in engine stats looks huge on paper.
But seriously...
You can also think of power as a measure of how quickly you are delivering the torque. Obviously, more torque (push) in a shorter time means the car will accelerate faster.
So for better performance you can either have more shove, period - which will be a higher torque figure. Or you can have the same about of shove delivered over a shorter period of time - which will be a higher power figure.
Obviously if you do both you have a monster - big Ferraris have > 400lb-ft AND > 500bhp.
The other thing to consider in all this is gearing - you can use gearing to convert big power into the feel of big torque, at the expense of revs. If you are geared to "fake" big torque you need more revs to reach a high speed.
This is the secret of the RX8 (and the S2000)... it has "only" 130some lb-ft but it's delivered through a short gearbox. So, it outperforms a lot of cars with 200+ torque figures. Those other cars would have peak power at 5-6k revs rather than 8-9. This is why the 8 can -almost- keep up with a 350 even though the gap in engine stats looks huge on paper.
11-15-2004, 03:29 PM
#13
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Originally Posted by zevans
So Kari, a turbo makes it, like, go faster, yeah? :D
But seriously...
You can also think of power as a measure of how quickly you are delivering the torque. Obviously, more torque (push) in a shorter time means the car will accelerate faster.
So for better performance you can either have more shove, period - which will be a higher torque figure. Or you can have the same about of shove delivered over a shorter period of time - which will be a higher power figure.
Obviously if you do both you have a monster - big Ferraris have > 400lb-ft AND > 500bhp.
The other thing to consider in all this is gearing - you can use gearing to convert big power into the feel of big torque, at the expense of revs. If you are geared to "fake" big torque you need more revs to reach a high speed.
This is the secret of the RX8 (and the S2000)... it has "only" 130some lb-ft but it's delivered through a short gearbox. So, it outperforms a lot of cars with 200+ torque figures. Those other cars would have peak power at 5-6k revs rather than 8-9. This is why the 8 can -almost- keep up with a 350 even though the gap in engine stats looks huge on paper.
But seriously...
You can also think of power as a measure of how quickly you are delivering the torque. Obviously, more torque (push) in a shorter time means the car will accelerate faster.
So for better performance you can either have more shove, period - which will be a higher torque figure. Or you can have the same about of shove delivered over a shorter period of time - which will be a higher power figure.
Obviously if you do both you have a monster - big Ferraris have > 400lb-ft AND > 500bhp.
The other thing to consider in all this is gearing - you can use gearing to convert big power into the feel of big torque, at the expense of revs. If you are geared to "fake" big torque you need more revs to reach a high speed.
This is the secret of the RX8 (and the S2000)... it has "only" 130some lb-ft but it's delivered through a short gearbox. So, it outperforms a lot of cars with 200+ torque figures. Those other cars would have peak power at 5-6k revs rather than 8-9. This is why the 8 can -almost- keep up with a 350 even though the gap in engine stats looks huge on paper.
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