Considering a 2015 model, things to consider - Page 4 - Mercedes GLA Forum
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post #31 of 38 Old 09-30-2018, 12:12 PM
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Originally Posted by RevItUp View Post
@Medtech: I'll be keeping my GLA45 stock for a long time, but could you provide a link to the product you are talking about for the westech filter/intake? I'm curious to see where the MAF sensor is in relation to these parts you've replaced. As you hinted, air flow is critically important anywhere near the MAF sensor. If the speed of air is changed it could disrupt the factory tune, and not necessarily for the better. Also, I've had experience tuning cars with aftermarket intakes and have tried to scale and tune some intakes and they just aren't fully tune-able... Any sort of change of bend of air movement, etc., can introduce turbulence which can do different things at different rpms and it can cost power (as the ecu dials back timing in certain rpm ranges where it sees oddities). Plus, in general, for cars that aren't otherwise modded with aftermarket down pipes or turbos, I'm a pretty staunch believer that a filter or intake is nearly never a bottleneck to air flow and it's more of a sound mod than a power mod, but just my opinion.
Sure, the link is below. As you can see in the comparison photos the OEM has a significant bottleneck. In fact I would have to call it extreme. Now, was that done only because they had to make an existing merc airbox work or was there more to it? The MAF location does not change a bit. Is the depth the same (meaning did wiestec add a little spacer)? Not sure.

I would have to guess that the speed of incoming air would have to be changed, hopefully in a good way.

FWIW I haven't noticed any negatives. But then again how much is an air filter really going to change by itself.

For those new to cars. An air filter is definitely not a power mod, don't let anyone tell ya different. I think Weistec is pretty up front about this, since they explicitly state that the max gain (all of 10hp) would only be possible with all the other mods in place (de-cat, BOV, and ECU). And of course, that 10hp may come at a point in the power band where it's essentially wasted.

Weistec M133 Air Intake System - Intake - 2015-Present (X156 / M133) - GLA 45 - GLA - Mercedes-Benz - Products
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post #32 of 38 Old 09-30-2018, 12:23 PM
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Originally Posted by Shadofax View Post
I would say YES, so long as it's doing a good job with filtration. A stock filter is what $ from a dealer? The best I can find online is about $50 and if I'm supposed to do this annually, it won't be long and the reusable has paid for itself. Then add that Weistec estimates 5-15 gains in power and torque, so if you assume 7 or so each that just adds to the value, now you're at 362/340 roughly. I have not looked closely down into the turbo inlet...I do see that this comes with a different tube that is almost 2x's the diameter, but does it shrink down to go into the turbo inlet anyway? Because then I would not see any benefit, but if stock you have that smaller inlet and then it gets big again going into the turbo, then I would see this as likely removing a restriction.
The tube that goes from air box to turbo stays 5" all the way, but yes the actual turbo inlet is definitely not 5". I don't have actual numbers, but I'm guessing around 3-4". I guess the next question would be whether or not the OEM air box adapter (that looks like a rocket nozzle) would direct a nozzle of air that would reach over 12" to shoot strait into the turbo inlet. Otherwise air just gets choked down, to then open up, and get choked down again.
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post #33 of 38 Old 09-30-2018, 03:15 PM
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Okay first since someone asked about the factory filter... as for the air filter on the GLA45, Mercedes replaced mine last week as part of the B-1 service. The total was $133 ($65 for the filter and $68 to install it). Yeah, $68 to install an air filter. WTF.

Anyhow, I haven't spent any time under the hood of our AMG but from those pics is that the MAF sensor just an inch or so from the air filter? My concern with this replacement piece is that it will move the same amount of air but through a greater space, so the speed of the air would appear to be less, which the car would interpret as a disconnect in load versus what the MAF is sensing vs the other inputs.... which would throw off a lot of the factory tune I'd bet. My other concern is that the AMG engineers intentionally put that little venturi/restriction in to make the air flow uniform at any engine speed, acceleration or deceleration and that just having that whole piece open like that negates that piece of engineering. My sense on this car is that this sort of stuff is rigorously engineered, and probably with tighter tolerances and a more aggressive factory tune than a lot of other vehicles. I think this mod will have unintended consequences although I can't say what.

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post #34 of 38 Old 10-01-2018, 01:28 PM
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Okay first since someone asked about the factory filter... as for the air filter on the GLA45, Mercedes replaced mine last week as part of the B-1 service. The total was $133 ($65 for the filter and $68 to install it). Yeah, $68 to install an air filter. WTF.

Anyhow, I haven't spent any time under the hood of our AMG but from those pics is that the MAF sensor just an inch or so from the air filter? My concern with this replacement piece is that it will move the same amount of air but through a greater space, so the speed of the air would appear to be less, which the car would interpret as a disconnect in load versus what the MAF is sensing vs the other inputs.... which would throw off a lot of the factory tune I'd bet. My other concern is that the AMG engineers intentionally put that little venturi/restriction in to make the air flow uniform at any engine speed, acceleration or deceleration and that just having that whole piece open like that negates that piece of engineering. My sense on this car is that this sort of stuff is rigorously engineered, and probably with tighter tolerances and a more aggressive factory tune than a lot of other vehicles. I think this mod will have unintended consequences although I can't say what.
Honestly Rev, you could easily be right. In fact I would say 50/50 at this point. What I need to do is to drive down to Weistec (or maybe call) and ask them these questions to see what they say. These guys seem to know what they are doing. However, there isn't much on their website about details on the development process on this mod.
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post #35 of 38 Old 10-05-2018, 07:10 PM
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no mfg will give you those details. If you want to know it, you need a simple a/b test on a dyno to see exactly what happens at the wheels, open or closed.

The wrench work to make that happen is somewhat prohibitive. To say nothing of the cost of buying dyno time on two separate days.
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post #36 of 38 Old 10-06-2018, 04:52 AM
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Originally Posted by RevItUp View Post
Okay first since someone asked about the factory filter... as for the air filter on the GLA45, Mercedes replaced mine last week as part of the B-1 service. The total was $133 ($65 for the filter and $68 to install it). Yeah, $68 to install an air filter. WTF.

Anyhow, I haven't spent any time under the hood of our AMG but from those pics is that the MAF sensor just an inch or so from the air filter? My concern with this replacement piece is that it will move the same amount of air but through a greater space, so the speed of the air would appear to be less, which the car would interpret as a disconnect in load versus what the MAF is sensing vs the other inputs.... which would throw off a lot of the factory tune I'd bet. My other concern is that the AMG engineers intentionally put that little venturi/restriction in to make the air flow uniform at any engine speed, acceleration or deceleration and that just having that whole piece open like that negates that piece of engineering. My sense on this car is that this sort of stuff is rigorously engineered, and probably with tighter tolerances and a more aggressive factory tune than a lot of other vehicles. I think this mod will have unintended consequences although I can't say what.
Ok, I sent your question to Weistec and this is the answer I got back:

"That is not a maf sensor. It is a pressure sensor that is used to make sure there is pressure change between the filter and the turbo inlet as that is needed to verify operation of the crankcase ventilation system. If there is too great a pressure change, there will be a CEL, if there is no pressure change, there will be a CEL. That's essentially all it is there for.

It has nothing to do with measuring airflow for calculating load. None of the modern mercedes turbo cars even have a MAF/Mass Air Sensor. Their control functions are torque based, not load based. The ECU targets a specific torque not a specific load. The ECU knows what torque its making based on fueling, boost, ignition timing, and air temperature as well as many other less commonly known variables and adjusts accordingly to meet targets.
Best Regards,
Staff Weistec staff"


I definitely learned something!
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post #37 of 38 Old 10-06-2018, 08:45 AM
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^^ That's great info! That really negates most of my concerns. I wonder if other manufactures are turning away from MAF sensors. For cars with them (which was most of what was produced prior to 2010 or so for sure), the great majority of the tune is based off what the MAF sensor is reading. That's the #1 reason by I've been a staunch pessimist for aftermarket intakes in most cars that are otherwise stock.

Alleviating that concern mostly, I'm just left wondering why AMG would choose to put a bottleneck on power with a piece of plastic at the beginning of the whole system. I really don't think they would introduce a bottleneck there.. .just doesn't make sense why they would. Would a big intake help once a car had a downpipe, aftermarket tune, and turbo? Yeah you bet. But I am still highly suspicious that this piece ALONE would have any benefit on an otherwise stock car without some sort of compromise elsewhere.

Great info, @Medtech!

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post #38 of 38 Old 10-12-2018, 10:38 PM
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Originally Posted by RevItUp View Post
^^ That's great info! That really negates most of my concerns. I wonder if other manufactures are turning away from MAF sensors. For cars with them (which was most of what was produced prior to 2010 or so for sure), the great majority of the tune is based off what the MAF sensor is reading. That's the #1 reason by I've been a staunch pessimist for aftermarket intakes in most cars that are otherwise stock.

Alleviating that concern mostly, I'm just left wondering why AMG would choose to put a bottleneck on power with a piece of plastic at the beginning of the whole system. I really don't think they would introduce a bottleneck there.. .just doesn't make sense why they would. Would a big intake help once a car had a downpipe, aftermarket tune, and turbo? Yeah you bet. But I am still highly suspicious that this piece ALONE would have any benefit on an otherwise stock car without some sort of compromise elsewhere.

Great info, @Medtech!

Keep in mind, it has been floated in prior posts that the pipe smallness may have something to do with directing air faster into the turbo inlet. I guess "the bigger the pipe" the more air can be moved through it, but there are limits, you will only take in so much air based on intake tube and filter. Smaller pipe with same airflow would increase velocity into turbo. And you're working with a paper filter. Granted it is a totally different box/filter than the standard 250 which I think has the flat filter. But there is still a limit to how much that intake into the box, and the standard paper filter, will flow. Now if you go to the weisetec filter that should be more free flowing, perhaps it can take advantage of this with larger tube.


I agree with everyone though, the gains would be on the low side of what is suggested, you aren't going to see the 15hp or whatever they mentioned just from this since they also mention there other upgrades, it's more toward the 5HP or so side.
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