Boost loss due to L/t
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03 e55
Boost loss due to L/t
How much boost will I lose after installing a more efficient L/T header and race cats setup? Will the loss of boost equate to power loss? Do most people swap to a larger pulley to compensate for the boost lose?
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Boost will go down because the engine becomes less of a restriction ( boost is a sign of restriction, not power ). How much will it go down I don't know, but you'll more power regardless.
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As was stated in the other response, boost will go down but power will go up with the LT headers. This is a good thing. The supercharger isn't working as hard and will produce less heat. Less heat is definitely a very positive added benefit when trying to avoid heat soak.
Tom
Tom
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2005 E55
As was stated in the other response, boost will go down but power will go up with the LT headers. This is a good thing. The supercharger isn't working as hard and will produce less heat. Less heat is definitely a very positive added benefit when trying to avoid heat soak.
Tom
Tom
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2005 E55 AMG
But what do you know....you're buying a bimmer. LOSER.
Last edited by GT-ER; Apr 23, 2011 at 11:31 AM.
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From: Puerto Rico
2005 E55 AMG
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As was stated in the other response, boost will go down but power will go up with the LT headers. This is a good thing. The supercharger isn't working as hard and will produce less heat. Less heat is definitely a very positive added benefit when trying to avoid heat soak.
Tom
Tom
The S/C is mechanically driven, the ratio of S/C rpm to engine rpm is fixed by their respective pullies and ratio. So, while the S/C is spinning at the same rpm (for a given engine rpm) both pre and post LT, since the amount of post-S/C restriction has gone down post LT install, it (the S/C) doesn't have to fight as hard to reach that same rpm. So, arguably, it isn't working quite as hard... and, as mentioned earlier, heat-generation drops as well.
As for the part about the S/C working harder to hit the same boost... this isn't a turbo motor - the S/C isn't trying to hit any specifc boost target. The S/C won't hit the same boost, because, again, it's mechanically driven and those ratios are set (unless you change the crank pulley, S/C pulley, or both).
Boost goes down because restrictions/bottlenecks have been mitigated. CFM, however, doesn't... that's the key.
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2005 E55
+1, well said.
The first part is debateable, IMHO. The second part is wrong.
The S/C is mechanically driven, the ratio of S/C rpm to engine rpm is fixed by their respective pullies and ratio. So, while the S/C is spinning at the same rpm (for a given engine rpm) both pre and post LT, since the amount of post-S/C restriction has gone down post LT install, it (the S/C) doesn't have to fight as hard to reach that same rpm. So, arguably, it isn't working quite as hard... and, as mentioned earlier, heat-generation drops as well.
As for the part about the S/C working harder to hit the same boost... this isn't a turbo motor - the S/C isn't trying to hit any specifc boost target. The S/C won't hit the same boost, because, again, it's mechanically driven and those ratios are set (unless you change the crank pulley, S/C pulley, or both).
Boost goes down because restrictions/bottlenecks have been mitigated. CFM, however, doesn't... that's the key.
The first part is debateable, IMHO. The second part is wrong.
The S/C is mechanically driven, the ratio of S/C rpm to engine rpm is fixed by their respective pullies and ratio. So, while the S/C is spinning at the same rpm (for a given engine rpm) both pre and post LT, since the amount of post-S/C restriction has gone down post LT install, it (the S/C) doesn't have to fight as hard to reach that same rpm. So, arguably, it isn't working quite as hard... and, as mentioned earlier, heat-generation drops as well.
As for the part about the S/C working harder to hit the same boost... this isn't a turbo motor - the S/C isn't trying to hit any specifc boost target. The S/C won't hit the same boost, because, again, it's mechanically driven and those ratios are set (unless you change the crank pulley, S/C pulley, or both).
Boost goes down because restrictions/bottlenecks have been mitigated. CFM, however, doesn't... that's the key.
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2005 E55
Supercharger is making the heat from the speed of the blades spinning.it made the same boost going into the intake.you loose psi un the manifold because of boost blowby going out the exh valve from freeing up the flow.
The blower has worked just as hard and like you said its mechanically driven.
You are confusing that boost psi is the cause of heat when its all about the rpms of the supercharger spinning that causes the heat.
run a 220mm pulley and no headers at all on your car,the boost in the manifold will be about the same as stock boost but the blower will be 10,000 rpms over its limit and melt down with one 1/4 run
A supercharger efficiency map is made up of rpms and volume flow for a specific psi
heat/boost will be the same at a givin rpm,they dont tell you you need xyz headers on the car when reading it.
It would be silly to say to someone that going from a 168 pulley to a 180 with long tubes will lower there intake air temps.
ps the supercharger gets a break when you free up the intake path with no restrictions like the use of say a carbon air box with filters
The blower has worked just as hard and like you said its mechanically driven.
You are confusing that boost psi is the cause of heat when its all about the rpms of the supercharger spinning that causes the heat.
run a 220mm pulley and no headers at all on your car,the boost in the manifold will be about the same as stock boost but the blower will be 10,000 rpms over its limit and melt down with one 1/4 run
A supercharger efficiency map is made up of rpms and volume flow for a specific psi
heat/boost will be the same at a givin rpm,they dont tell you you need xyz headers on the car when reading it.
It would be silly to say to someone that going from a 168 pulley to a 180 with long tubes will lower there intake air temps.
ps the supercharger gets a break when you free up the intake path with no restrictions like the use of say a carbon air box with filters
Last edited by skratch77; Apr 23, 2011 at 05:04 PM.
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Tom
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2005 E55
You have to look at each mod in isolation. I never said changing a pulley wouldn't create more boost and heat. The addition of the headers to a car that already had a pulley swap is going to result in some lower IATs at the same RPM as when it didn't have the headers. Who cares how hard it would need to work to hit the same boost level? That is completely meaningless unless you plan to do other mods to increase your engine's redline. It is more relevant to compare hp and boost at a certain RPM when adding the headers.
Tom
Tom
Id like to read up on how the temps will drop and see where you are coming from.
think of it this way,the blower made the same psi.1.5 lbs off boost snuck by the chamber and out the tail pipe.The boost was made at one point or another.You can play with cams to get that lost boost back in the mid range but suffer top end power.
That is why your a/f gets leaner with headers,the tail sniffer is seeing more air that got blown by without burning.
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From my data logging going to headers with no cats the temps were spot on before and after.
Id like to read up on how the temps will drop and see where you are coming from.
think of it this way,the blower made the same psi.1.5 lbs off boost snuck by the chamber and out the tail pipe.The boost was made at one point or another.You can play with cams to get that lost boost back in the mid range but suffer top end power.
That is why your a/f gets leaner with headers,the tail sniffer is seeing more air that got blown by without burning.
Id like to read up on how the temps will drop and see where you are coming from.
think of it this way,the blower made the same psi.1.5 lbs off boost snuck by the chamber and out the tail pipe.The boost was made at one point or another.You can play with cams to get that lost boost back in the mid range but suffer top end power.
That is why your a/f gets leaner with headers,the tail sniffer is seeing more air that got blown by without burning.
Tom
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Pressure is the main cause of heat but the type of supercharger will also affect the intake temps too. More efficient superchargers produce less heat. However, the more boost pressure the hotter the charge. Air gets very hot when you put it under pressure.
Headers reduce boost and make more power by flowing air more efficiently than the stock exhaust manifolds. An engine is an air pump. The faster you can get air in and out the more power you will make. If you can make the heads flow more efficiently, the engine will make more power and there will be less boost. Boost is the measure of an engines inability to flow air from forced induction.
Headers reduce boost and make more power by flowing air more efficiently than the stock exhaust manifolds. An engine is an air pump. The faster you can get air in and out the more power you will make. If you can make the heads flow more efficiently, the engine will make more power and there will be less boost. Boost is the measure of an engines inability to flow air from forced induction.
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Pressure is the main cause of heat but the type of supercharger will also affect the intake temps too. More efficient superchargers produce less heat. However, the more boost pressure the hotter the charge. Air gets very hot when you put it under pressure.
Headers reduce boost and make more power by flowing air more efficiently than the stock exhaust manifolds. An engine is an air pump. The faster you can get air in and out the more power you will make. If you can make the heads flow more efficiently, the engine will make more power and there will be less boost. Boost is the measure of an engines inability to flow air from forced induction.
Headers reduce boost and make more power by flowing air more efficiently than the stock exhaust manifolds. An engine is an air pump. The faster you can get air in and out the more power you will make. If you can make the heads flow more efficiently, the engine will make more power and there will be less boost. Boost is the measure of an engines inability to flow air from forced induction.
Eloquently stated, thank you.
