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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Anyone else want a thicker intercooler..and larger oil cooler?



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      04-21-2007, 11:27 PM   #23
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Here is the question of the day.

Larger intercooler means more air mass (obviously).
Is there any way to set a PROcede to recognize the larger air mass?
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      04-22-2007, 12:01 AM   #24
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changed it back :mad: :mad:
thank god.
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      04-22-2007, 01:08 AM   #25
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Hey S,
Do the Sept 7th ButtonWillow day with BMWCCA Central chapter.
I'll get the day off and we'll hit the track together.
You're not an instructor for BMWCCA, just Audi club right ?
I need to have a BMWCCA instructor sign me off to solo......

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      04-22-2007, 06:31 AM   #26
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raider why did you changed your avatar from that amazing girl to some tools nipples

ur screen name is Montego335 spelled backwards...
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      04-22-2007, 10:08 AM   #27
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Originally Posted by 533ogetnom View Post
turbo lag comes from the amount of time for the tubo to spin up not the amount of time for the turbo to pressurize the piping after its spun up

go look at the TT vettes w/ rear mounted turbos and enough piping to plum my house
yeah but you will begin to lose boost pressure with a larger and larger intercooler... greater volume = less pressure.

I guess what I am really saying is that people better be careful with intercooler mods to avoid over-sizing it and actually hurting performance.
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      04-22-2007, 10:24 AM   #28
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While I do want a bigger intercooler, the fact is that getting a bigger intercooler should correspond to the gain in power that you're putting out. Otherwise, yeah it actually does lower performance a lil bit. Unless I'm wrong about that?

Pressure Drop

Another aspect of intercoolers to be considered is pressure drop. The pressure read by a boost gauge is the pressure in the intake manifold. It is not the same as the pressure that the turbocharger itself puts out. To get a fluid, such as air, to flow there must be a difference in pressure from one end to the other. Consider a straw that is sitting on the table. It doesn't having anything moving through it until you pick it up, stick it in your mouth, and change the pressure at one end (either by blowing or sucking). In the same way the turbo outlet pressure is higher than the intake manifold pressure, and will always be higher than the intake pressure, because there must be a pressure difference for the air to move.

The difference in pressure required for a given amount of air to move from turbo to intake manifold is an indication of the hydraulic restriction of the intercooler, the up pipe, and the throttle body. Let's say you are trying to move 255 gram/sec of air through a stock intercooler, up pipe, and throttle body and there is a 4 psi difference that is pushing it along (I'm just making up numbers here). If your boost gauge reads 15 psi, that means the turbo is actually putting up 19 psi. Now you buy a PT-70 and slap on some Champion heads. Now you are moving 450 gm/sec of air. At 15 psi boost in the intake manifold the turbo now has to put up 23 psi, because the pressure drop required to get the higher air flow is now 8 psi instead of the 4 that we had before. More flow with the same equipment means higher pressure drop. So we put on a new front mount intercooler. It has a lower pressure drop, pressure drop is now 4 psi, so the turbo is putting up 19 psi again. Now we add the 65 mm throttle body and the pressure drop is now 3 psi. Then we add the 2.5" up pipe, and it drops to 2.5 psi. Now to make 15 psi boost the turbo only has to put up 17.5 psi. The difference in turbo outlet temperature between 23 psi and 17.5 psi is about 40 deg (assuming a constant efficiency)! So you can see how just by reducing the pressure drop we can lower the temperatures while still running the same amount of boost.

I have seen some misunderstandings regarding intercooler pressure drop and how it relates to heat transfer. For example, one vendor's catalog implies that if you had little or no pressure drop then you would have no heat transfer. This is incorrect. Pressure drop and heat transfer are relatively independent, you can have good heat transfer in an intercooler that has a small pressure drop if it is designed correctly. It is easier to have good heat transfer when there is a larger pressure drop because the fluid's turbulence helps the heat transfer coefficient (U), but I have seen industrial coolers that are designed to have less than 0.2 psi of drop while flowing a heck of a lot more air, so it is certainly feasible.

Pressure drop is important because the higher the turbo discharge pressure is the higher the temperature of the turbo air. When we drop the turbo discharge pressure we also drop the temperature of the air coming out of the turbo. When we do that we also drop the intercooler outlet temperature, although not as much, but hey, every little bit helps. This lower pressure drop is part of the benefit offered by new, bigger front mount intercoolers; by the Duttweiler neck modification to stock location intercoolers; by bigger up pipes; and by bigger throttle bodies. You can also make the turbo work less hard by improving the inlet side to it. K&N air filters, free flowing MAF pipes, removing a screen from the MAF, removing the MAF itself when switching to an aftermarket fuel injection system, the upcoming 3" and 3.5" MAFs from Modern Muscle, these all reduce the pressure drop in the turbo inlet system which makes the compressor work less to produce the same boost which will reduce the turbo discharge temperature (among other, and probably greater, benefits).

What about my Intercooler?
Wondering if your intercooler is up to snuff? The big test: measure your intercooler outlet temperature! When I did this I got a K type thermocouple, the thin wire kind, slid it under the throttle body/up pipe hose and down into the center of the up pipe, and went for a drive. On an 80 to 85 deg day I got a WOT temperature of 140 deg, for a 55 to 60 deg approach. That tells me that I need more intercooler. If I can get the temperature down to 100 deg, the air density in the intake manifold goes up by 7%, so I should flow 7% more air and presumably make 7% more hp. On a 350 hp engine that is 25 hp increase. On a 450 hp engine that's a 30 hp increase. Damn, where's my check book…

Another check is pressure drop. Best way to check it is to find a pressure differential gauge, which has 2 lines instead of the single line a normal pressure gauge has. It checks the difference between the 2 spots it is hooked up to, as opposed to checking the difference in pressure between the spot it is hooked up to and atmospheric pressure, which is how a normal pressure gauge works.

Hook one line of the gauge to the turbo outlet and one to (preferably) the intercooler outlet. The turbo outlet/intercooler inlet pressure is easy, just tee into the wastegate supply line off the compressor housing. It would be nice to get the intercooler outlet pressure directly, but there's no convenient spot to hook up to. Hooking into the intake manifold (such as via the line to the boost gauge) is quite convenient, but gives the total pressure drop: intercooler + up pipe + throttle body. That'll give you a pretty good idea though.

Instead of the differential pressure gauge you could use 2 boost gauges, one in each spot, but then you have to worry about whether both gauges are calibrated the same, try to read both at the same time while driving fast, etc AND you may spring (ie, ruin) the gauge on the turbo outlet since when you close the throttle you get a big pressure spike that your normal boost gauge never sees.

If you find more than 4 or 5 psi difference between the intercooler inlet and intake manifold (and I'm just giving an educated guess here, you'd probably want to refer to one of the intercooler manufacturers for a better number) then I would suspect that a larger, lower pressure drop intercooler would offer you some gains.
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      04-22-2007, 10:44 AM   #29
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I don't think a larger intercooler can lower performance or create lag (even doubling the volume of the stock IC is nothing compared to the CFM coming out of the turbo), but I'm not sure it will help performance. What kind of IATs are proceed cars seeing? If it's only 25-30 degrees above ambient then it's probably not worth it.
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      04-22-2007, 11:26 AM   #30
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Originally Posted by kujo View Post
Hey S,
Do the Sept 7th ButtonWillow day with BMWCCA Central chapter.
I'll get the day off and we'll hit the track together.
You're not an instructor for BMWCCA, just Audi club right ?
I need to have a BMWCCA instructor sign me off to solo......

kj

I have taught for BMW club at Sears back in 2001 or 2002...
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      04-22-2007, 11:27 AM   #31
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Quote:
Originally Posted by ArmyBimmerDude View Post
While I do want a bigger intercooler, the fact is that getting a bigger intercooler should correspond to the gain in power that you're putting out. Otherwise, yeah it actually does lower performance a lil bit. Unless I'm wrong about that?

Pressure Drop

Another aspect of intercoolers to be considered is pressure drop. The pressure read by a boost gauge is the pressure in the intake manifold. It is not the same as the pressure that the turbocharger itself puts out. To get a fluid, such as air, to flow there must be a difference in pressure from one end to the other. Consider a straw that is sitting on the table. It doesn't having anything moving through it until you pick it up, stick it in your mouth, and change the pressure at one end (either by blowing or sucking). In the same way the turbo outlet pressure is higher than the intake manifold pressure, and will always be higher than the intake pressure, because there must be a pressure difference for the air to move.

The difference in pressure required for a given amount of air to move from turbo to intake manifold is an indication of the hydraulic restriction of the intercooler, the up pipe, and the throttle body. Let's say you are trying to move 255 gram/sec of air through a stock intercooler, up pipe, and throttle body and there is a 4 psi difference that is pushing it along (I'm just making up numbers here). If your boost gauge reads 15 psi, that means the turbo is actually putting up 19 psi. Now you buy a PT-70 and slap on some Champion heads. Now you are moving 450 gm/sec of air. At 15 psi boost in the intake manifold the turbo now has to put up 23 psi, because the pressure drop required to get the higher air flow is now 8 psi instead of the 4 that we had before. More flow with the same equipment means higher pressure drop. So we put on a new front mount intercooler. It has a lower pressure drop, pressure drop is now 4 psi, so the turbo is putting up 19 psi again. Now we add the 65 mm throttle body and the pressure drop is now 3 psi. Then we add the 2.5" up pipe, and it drops to 2.5 psi. Now to make 15 psi boost the turbo only has to put up 17.5 psi. The difference in turbo outlet temperature between 23 psi and 17.5 psi is about 40 deg (assuming a constant efficiency)! So you can see how just by reducing the pressure drop we can lower the temperatures while still running the same amount of boost.

I have seen some misunderstandings regarding intercooler pressure drop and how it relates to heat transfer. For example, one vendor's catalog implies that if you had little or no pressure drop then you would have no heat transfer. This is incorrect. Pressure drop and heat transfer are relatively independent, you can have good heat transfer in an intercooler that has a small pressure drop if it is designed correctly. It is easier to have good heat transfer when there is a larger pressure drop because the fluid's turbulence helps the heat transfer coefficient (U), but I have seen industrial coolers that are designed to have less than 0.2 psi of drop while flowing a heck of a lot more air, so it is certainly feasible.

Pressure drop is important because the higher the turbo discharge pressure is the higher the temperature of the turbo air. When we drop the turbo discharge pressure we also drop the temperature of the air coming out of the turbo. When we do that we also drop the intercooler outlet temperature, although not as much, but hey, every little bit helps. This lower pressure drop is part of the benefit offered by new, bigger front mount intercoolers; by the Duttweiler neck modification to stock location intercoolers; by bigger up pipes; and by bigger throttle bodies. You can also make the turbo work less hard by improving the inlet side to it. K&N air filters, free flowing MAF pipes, removing a screen from the MAF, removing the MAF itself when switching to an aftermarket fuel injection system, the upcoming 3" and 3.5" MAFs from Modern Muscle, these all reduce the pressure drop in the turbo inlet system which makes the compressor work less to produce the same boost which will reduce the turbo discharge temperature (among other, and probably greater, benefits).

What about my Intercooler?
Wondering if your intercooler is up to snuff? The big test: measure your intercooler outlet temperature! When I did this I got a K type thermocouple, the thin wire kind, slid it under the throttle body/up pipe hose and down into the center of the up pipe, and went for a drive. On an 80 to 85 deg day I got a WOT temperature of 140 deg, for a 55 to 60 deg approach. That tells me that I need more intercooler. If I can get the temperature down to 100 deg, the air density in the intake manifold goes up by 7%, so I should flow 7% more air and presumably make 7% more hp. On a 350 hp engine that is 25 hp increase. On a 450 hp engine that's a 30 hp increase. Damn, where's my check book…

Another check is pressure drop. Best way to check it is to find a pressure differential gauge, which has 2 lines instead of the single line a normal pressure gauge has. It checks the difference between the 2 spots it is hooked up to, as opposed to checking the difference in pressure between the spot it is hooked up to and atmospheric pressure, which is how a normal pressure gauge works.

Hook one line of the gauge to the turbo outlet and one to (preferably) the intercooler outlet. The turbo outlet/intercooler inlet pressure is easy, just tee into the wastegate supply line off the compressor housing. It would be nice to get the intercooler outlet pressure directly, but there's no convenient spot to hook up to. Hooking into the intake manifold (such as via the line to the boost gauge) is quite convenient, but gives the total pressure drop: intercooler + up pipe + throttle body. That'll give you a pretty good idea though.

Instead of the differential pressure gauge you could use 2 boost gauges, one in each spot, but then you have to worry about whether both gauges are calibrated the same, try to read both at the same time while driving fast, etc AND you may spring (ie, ruin) the gauge on the turbo outlet since when you close the throttle you get a big pressure spike that your normal boost gauge never sees.

If you find more than 4 or 5 psi difference between the intercooler inlet and intake manifold (and I'm just giving an educated guess here, you'd probably want to refer to one of the intercooler manufacturers for a better number) then I would suspect that a larger, lower pressure drop intercooler would offer you some gains.

too much reading man
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      04-22-2007, 11:42 AM   #32
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That text says that larger, lower pressure intercooler would offer gains.

If temps are decreased and pressure drop is less than stock, then the power goes up, of course.
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      04-22-2007, 12:19 PM   #33
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I would be so interested in a bigger Intercooler, but a more efficient one. If the one we have is very efficient allready, then there would be no sense to me on changing it, however, having one that looks much better (the cheap plastic) would be great. It would be really nice to have a better finish on the pipes .
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      04-22-2007, 12:36 PM   #34
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Components have to be matched. Tiny turbos feeding a larger front mount intercoolers could be a mismatch if the pressure drop offsets your cooling effect.
The larger intercooler requires more air to fill it, the tiny turbo spins harder to generate the same net effect. The air coming out of the turbo is now hotter due to the higher boost needed to compensate for the pressure drop from a larger intercooler.
You are fighting an issue of diminishing returns once you leave the turbos volumetric efficiency "sweet spot"
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      04-22-2007, 01:13 PM   #35
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ur screen name is Montego335 spelled backwards...
how long did you stare at it for? i want the other avatar back :mad:
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      04-22-2007, 01:27 PM   #36
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Quote:
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Components have to be matched. Tiny turbos feeding a larger front mount intercoolers could be a mismatch if the pressure drop offsets your cooling effect.
The larger intercooler requires more air to fill it, the tiny turbo spins harder to generate the same net effect. The air coming out of the turbo is now hotter due to the higher boost needed to compensate for the pressure drop from a larger intercooler.
You are fighting an issue of diminishing returns once you leave the turbos volumetric efficiency "sweet spot"
Typically best aftermarket intercoolers are better than stock getting temps lower while being able to maintain pressure drop at stock level. Now if you have tiny turbos at the edge of their efficiency range and push even more boost, you generate higher temperatures and you need larger intercooler to get the temps down. If you have big turbo, it provides high flow easily without pushing and boosting it. The temps stay low and there is not much need to increase intercooling efficiency.

In case of 335, the boost is low to begin with, thus the OE intercooler manages ok. A better intercooler could manage even better, especially if increasing boost.
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      04-22-2007, 09:02 PM   #37
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Quote:
Originally Posted by Dr_Dirt View Post
Components have to be matched. Tiny turbos feeding a larger front mount intercoolers could be a mismatch if the pressure drop offsets your cooling effect.
The larger intercooler requires more air to fill it, the tiny turbo spins harder to generate the same net effect. The air coming out of the turbo is now hotter due to the higher boost needed to compensate for the pressure drop from a larger intercooler.
You are fighting an issue of diminishing returns once you leave the turbos volumetric efficiency "sweet spot"
listen to this one! He is sharp.

You can listen to me too... I am a mechanical engineer who flows and compresses gas for a living.

If you mismatch your intercooler size to your turbo, you will either reduce the pressure of the gas heading into the intake side of the engine or, as said above, you may increase lag in your system due to the fact that your turbos now have to discharge gas into a larger area.

It is a law of diminishing returns.... you really need to optimize the system and bigger is not necessarily better.
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      04-23-2007, 03:13 AM   #38
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Intercooling capacity needs to matched. But matched to what? It needs to be matched to the inlet temps. The more heat, the more cooling helps. Each degree down is more hp. If temps are low, the need for intercooling is low.
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