E55amg/FD3S

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?

GT-ER

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.

shardul

iTrader: (1)

Well said gtr. It will make more power with less boost. But to answer your question about 1.5psi

TMC M5

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

skratch77

The supercharger is working just as hard my friend,if anything its working harder to hit the same boost with a larger pulley.

GT-ER

I think he meant by leaving the oem pulley. But the SC will work just as hard regardless, the pressure/temperature being produced after it exits the SC is the only thing that changes.

But what do you know....you're buying a bimmer. LOSER.

skratch77

Hey I still have a faster e55 then most of u guys

GT-ER

Until monday.

skratch77

Whats monday have in plan for you?

GT-ER

Aren't you selling on monday?

skratch77

Ohh I thought you we're going to the track on Monday.

GT-ER

Not till I get some real tires. My 1st and 2nd are pretty useless at the track with my current setup.

c32AMG-DTM

+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.

lightningfast7

Nailed it... Thanks for saving me the time to explain. Haha! Think you explained better than I could have anyways.

skratch77

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

TMC M5

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

mikey33

I say LT's = More Power

That is the extent of my knowledge

skratch77

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.

TMC M5

I am going by my experience with my supercharged CTS-V. On a CTS-V headers will drop boost between 1.5 and 2 psi. My car lost 1.6psi with Kooks headers mated to high flow cats, but I picked up 19rwhp at its peak. The IATs dropped about 5% over my pre-header IATs (before my pulley swap). I am not sure why you haven't experienced the same. Also, there is a ton of good info out there on the impact of supercharger mods in the Mustang Cobra/GT500 community. It shouldn't matter what make it is...although if the intercooling system is highly inefficient, that could result in significant differences. I wouldn't think that the 55K's intercooling system is that bad.

Tom

MBH motorsports

generally speaking, about 1psi or so in boost drop. Good thing is you make more power on less boost.

E55amg/FD3S

Thanks for all the responses!

BlownV8

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.

c32AMG-DTM

+1

Eloquently stated, thank you.