Top mount vs. traditional - Advantages, Disadvantages?

[Sticky]

I have been curious about why the big numbers on The M50 S50's seem to come from top mounts?

On another site I was reading that there are no real advantages and some disadvantages actually but want to get some input from the guys here.

[Turbology]

It's all about packaging! There are no power advantages per se, the idea is that big boy turbos (read, most anything T4-flanged and bigger) take up a lot of space in engine bays.

Smaller-frame turbos (T25 and T3-flanged) can generally be tucked neatly between the chassis and the head in both longitudinal (BMW) and transverse (EVO etc.) configurations.

So when you want to run a massive snail, chances are it won't fit in the traditional space of the OE exhaust manifold. In that case, flip the flange to top-mount and you have all the room in the world (well at least as much clearance as the hood allows!).

[Sticky]

It's all about packaging! There are no power advantages per se, the idea is that big boy turbos (read, most anything T4-flanged and bigger) take up a lot of space in engine bays.

Smaller-frame turbos (T25 and T3-flanged) can generally be tucked neatly between the chassis and the head in both longitudinal (BMW) and transverse (EVO etc.) configurations.

So when you want to run a massive snail, chances are it won't fit in the traditional space of the OE exhaust manifold. In that case, flip the flange to top-mount and you have all the room in the world (well at least as much clearance as the hood allows!).

Makes sense

[Turbology]

Bimmer Boost Guru Jon @ 666 puts things in perspective...

[Sticky]

I definitely see what you mean... where else would you stick that huge freaking turbo?

Plus... top mount just looks ridiculously cool.

[Turbology]

I definitely see what you mean... where else would you stick that huge freaking turbo?

Plus... top mount just looks ridiculously cool.

You could always remote-mount it a la STS, but I'm not sure how I feel about my turbo hanging a few inches off the ground!


http://www.ststurbo.com/the_technology

[Sticky]

You could always remote-mount it a la STS, but I'm not sure how I feel about my turbo hanging a few inches off the ground!


http://www.ststurbo.com/the_technology

I like that sts provides another options but just have never been a fan of remote mount.

[Turbology]

STS claims the extended length of the charge piping negates the need for an actual intercooler, and that may be so (in low boost applications at least), but I can't help but think that amount of plumbing leads to lag.

[Sticky]

STS claims the extended length of the charge piping negates the need for an actual intercooler, and that may be so (in low boost applications at least), but I can't help but think that amount of plumbing leads to lag.

You would think so, more plumbing than a house.... plus, in places where the natural elements may be an issue I would think there might be problems.

[Turbology]

That's more or less my take on remote-mount, probably just fine in dry, flat places like Texas. Not sure how long it would last in the Tri-State Area.
:razz:

[fundahl]

I've also looked into remote mount solutions but have not found very much dyno information or videos proving their worth vs conventional turbo systems. If they do work well then it would allow for a somewhat easy install for vehicles with limited engine bay space. One thing I would worry about is loss of exhaust energy before the turbine due to less heat and velocity vs "close to exhaust port" setups, which would create less drive across the turbine wheel. Maybe some sort of insulated exhaust system could combat the energy loss.

[Turbology]

STS claims a better "pressure differential" with remote-mounting, and my guess is they base this on several exhaust pulses sequentially hitting the turbine wheel rather than just raw, turbulent exhaust gas direct from the head.

Truthfully, as center cartridge technology improves, the question of lag in a remote-mount set-up may become negligible, though I am curious if that would hold true on smaller displacement applications (of which there are very few, if you notice).

STS's logic...

Benefits of STS Remote-Mounted Turbochargers

Lower underhood temperatures. No need to worry about melting wires, hoses, or other engine components, as with a front-mounted turbo.

Ease of installation. STS turbo systems can be installed in about 8 hours with standard tools and average mechanical ability.

Cooler oil to the turbo. Cool oil is better for both the turbo and engine.

Performance Sound. The turbo acts as a muffler and sounds like an aftermarket performance muffler. Turbo spool and rushing air from the blow-off valve make a unique sound that will turn heads!

No need for major modifications to your vehicle. STS systems are designed to "bolt-on" to factory mounts.

Increased gas mileage. Unlike a belt driven supercharger, the turbo utilizes "wasted" energy leaving your tailpipe. Most of our customers get 1-3 mpg increase in gas mileage compared to their original stock mpg numbers.

Converts back to stock in about an hour.

More room under the hood. Future repair work or modifications will not require the expense of removing the turbo system to allow access to engine components.

Lowest Intake Air Temps. Low IAT's equate to more horsepower per pound of boost than any other forced induction option. STS intake piping provides built-in intercooling. Add the optional intercooler, and IAT's drop even further.

Approximately 500F lower turbo temperatures. Eliminates the need for a turbo-timer, which allows the engine to run after the car is shut off in order to cool down the turbo and prevent oil and bearing damage.

Denser exhaust gasses drive the turbo turbine wheel more efficiently.

Turbo is exposed to ambient air rather than underhood air. Allows for better cooling of turbo components.

No need for expensive headers, mufflers, or exhaust systems.

Turbo is closer to the tail pipe outlet. Provides a better pressure differential across the turbine wheel which promotes better flow across turbine.

Better weight transfer. Increases traction because the bulk of system is mounted in rear of vehicle rather than up front.

Less noise and heat in the passenger compartment.

[milkt]

top mount versus remote mount?

[GG///M3]

top mount versus remote mount?

How about twin turbo. 1 mounted on top, and other on the bottom. BAMM

[milkt]

How about twin turbo. 1 mounted on top, and other on the bottom. BAMM

Very helpful input.

[highboostingm3]

Top mount has many disadvantages actually and few advantages. I will name a few pros/cons:

Pros:
-fabulous oil drain.
-easy to swap turbos in comparison.
-easy to work on your turbo, DP, oil feed/drain...
-it looks pretty darn cool.

Cons:
-Lots of heat.
-Fitment can be rough the bigger the turbo and some denting might need to happen for clearance.
-Limited to 3" DP with the e36 unless you really configure the manifold/wastegate setup in a way where you can somehow squeeze bigger.
-If a cop actually asks you to pop you hood it is sort of a dead giveaway.
-Nearly impossible to run draw-through MAF on e36 (now that TRM has sick blow-through that's not really an issue anymore)
-Barely enough room for a tiny air filter.
-A/C lines need to be rerouted and customized.
-could get in the way of your shroud and puller fan setup.
-might have to relocate your radiator overflow tank or get the euro one.
-could melt your valve cover unless you switch to a metal one (which I believe are only OBDI with the oil cap in rear which some dislike)
-up until now with the OBX manifold becoming available in top mount you had to go custom to achieve it which is $$$$.
-there are no "kits" available which means you are going all custom.

So my guess is that those who are willing to look past all the Cons above in order to have a schweet turbo when they pop the hood and ease of oil drain etc., they aren't afraid to pony up some more caysh and go with a bigger turbo and built motor for the bigger numbers because...well hey they like to GO BIG!

[Sticky]

Top mount has many disadvantages actually and few advantages. I will name a few pros/cons:

Pros:
-fabulous oil drain.
-easy to swap turbos in comparison.
-easy to work on your turbo, DP, oil feed/drain...
-it looks pretty darn cool.

Cons:
-Lots of heat.
-Fitment can be rough the bigger the turbo and some denting might need to happen for clearance.
-Limited to 3" DP with the e36 unless you really configure the manifold/wastegate setup in a way where you can somehow squeeze bigger.
-If a cop actually asks you to pop you hood it is sort of a dead giveaway.
-Nearly impossible to run draw-through MAF on e36 (now that TRM has sick blow-through that's not really an issue anymore)
-Barely enough room for a tiny air filter.
-A/C lines need to be rerouted and customized.
-could get in the way of your shroud and puller fan setup.
-might have to relocate your radiator overflow tank or get the euro one.
-could melt your valve cover unless you switch to a metal one (which I believe are only OBDI with the oil cap in rear which some dislike)
-up until now with the OBX manifold becoming available in top mount you had to go custom to achieve it which is $$$$.
-there are no "kits" available which means you are going all custom.

So my guess is that those who are willing to look past all the Cons above in order to have a schweet turbo when they pop the hood and ease of oil drain etc., they aren't afraid to pony up some more caysh and go with a bigger turbo and built motor for the bigger numbers because...well hey they like to GO BIG!

Very helpful, very nice overview, and very well done.

You even managed to do even do it without any riddles or any inside jokes.

[highboostingm3]

Very helpful, very nice overview, and very well done.

You even managed to do even do it without any riddles or any inside jokes.

Thank you. You are absolutely welcome! It is tough to refrain from any riddles or any inside jokes, but I somehow pulled through.