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  #1  
Old 24th March 2008
blunk_blind blunk_blind is offline
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Default AMM mod - Anyone ever ruined their AMM because of this

I just removed my grilles from the AMM, and i notice quite the difference in achiving speed between 145-170km, i love this mod, however has anyone got a rock or something in there AMM??

K
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  #2  
Old 24th March 2008
brownie brownie is offline
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If a rock got into your AMM then a broken AMM would be the least of your worries once the rock enters your engine.

For that reason, some folks like to keep the rear screen.
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  #3  
Old 24th March 2008
SaabStory60 SaabStory60 is offline
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Why is it better to keep the rear screen instead of the front? If you kept the front then it would protect the AMM and turbo/engine the rear screen only protects the turbo/engine.
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  #4  
Old 24th March 2008
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The screen protects the compressor on the turbo and helps swirl in the AMM, thats it, I personally don't think it will give more power.
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  #5  
Old 24th March 2008
brownie brownie is offline
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Quote:
Originally Posted by SaabStory60
Why is it better to keep the rear screen instead of the front? If you kept the front then it would protect the AMM and turbo/engine the rear screen only protects the turbo/engine.
I think the idea is to keep at least one of the screens for protection. It makes more sense to keep the front one, you're right. I think you'd have to have a good imagination to consider screen removal to be a real performance modification, though.
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  #6  
Old 25th March 2008
blunk_blind blunk_blind is offline
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Quote:
Originally Posted by brownie
I think the idea is to keep at least one of the screens for protection. It makes more sense to keep the front one, you're right. I think you'd have to have a good imagination to consider screen removal to be a real performance modification, though.
I swear to you guys, that was the only engine mod i did that entire day. I noticed a difference at high speeds. Before I would have to wait for it to hit 160 (which is sad i know) Now I have to wait for it to hit 180 (which is still sad, but better)

what are teh chances of a rock actually getting into the AMM??
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  #7  
Old 25th March 2008
beckzach05 beckzach05 is offline
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Quote:
Originally Posted by blunk_blind
what are teh chances of a rock actually getting into the AMM??
Depends, how often are you going underground with it? Seriously though, if your air filter/inlet are in the stock location, I think you'd be pretty hard pressed to get a rock..

The guys over at turbobricks (volvo performance forum) remove the rear screen from their AMMs also. Anybody have dyno access that can check a before-and-after scenario with this?
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  #8  
Old 25th March 2008
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The two screens on the AMM cause the largest two pressure drops in the inlet system of a car (far more than is caused by the airfilter), so removing them is of benefit (look for the Autospeed articles covering negative pressure). However, without the screens there is danger of damage to the AMM and not just from road debris, also screwdrivers and the like if the car is being worked on and the mechanic is carless with the tools.

Depending on what has been done with the airfilter and its position the lack of the front screen may cause issues with the AMM not registering the airflow correctly at low engine speeds and the car not drive as well as a result.
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Old 25th March 2008
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Quote:
Originally Posted by Alex
Depending on what has been done with the airfilter and its position the lack of the front screen may cause issues with the AMM not registering the airflow correctly at low engine speeds and the car not drive as well as a result.
i think youre quite right with that one mate. i removed the front screen from the AMM and my 900 didnt like it all that much it would cough, miss and splutter every time i took off normally/slowly

hey do you know if the LH2.2 AMM's have an air temp sensor in them?
is it possible to have too colder intake air? cos my 900 seems to run like crap when its cold unless i really gas it and get it into high RPM's

EDIT: by cold, i mean cold weather, not cold engine
one thing i will not do is thrash an engine when its cold

Last edited by ludichris001; 26th March 2008 at 07:04 AM.
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  #10  
Old 25th March 2008
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Someone (Widde?) tested an AMM for flow with and without the screen, and found the grilles to be a significant restriction. I have had mine removed for probably a year or so with no problems. Although I always keep a spare in the trunk, so I'm not too worried about breaking it.
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  #11  
Old 27th March 2008
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Question

hey just a quick one,

i was in the process of fitting a new turbo a couple of days ago, and took the AMM off of the intake for the turbo and clamped it straight to the TB, so basically it was running N/A. the problem i found was that when i stomped the pedal to full throttle, it would try to rev up but wouldnt go above 1500RPM. it would just splutter and missfire and knock, like its starving for fuel.
there is no vacuum, leaks and i am running tubo injectors and a 3 bar FPR, i tried an N/A ECU but it made no difference. is this supposed to happen? or could it be related to the AMM?

could someone shed some light on the situation please

(LH2.2 on 8vT - custom job btw)

cheers!
chris.
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  #12  
Old 27th March 2008
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Quote:
Originally Posted by TheRedBaron
Someone (Widde?) tested an AMM for flow with and without the screen, and found the grilles to be a significant restriction.
Air does not flow well through a mesh. Easy to test - blow on the back of your hand, then try it with the mesh.

The AMM's calibration is based on those screens beign present in the airflow. Removing them will make a difference, but what exactly? Without measurements from sensors it's all speculation.

In particular, I'd be interested to see with-screen and without-screen AFR plots.
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  #13  
Old 27th March 2008
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Quote:
Originally Posted by Matthew
Air does not flow well through a mesh. Easy to test - blow on the back of your hand, then try it with the mesh.

The AMM's calibration is based on those screens beign present in the airflow. Removing them will make a difference, but what exactly? Without measurements from sensors it's all speculation.

In particular, I'd be interested to see with-screen and without-screen AFR plots.
Yeah, I've thought about that before, I'd imagine that the increased turbulence of the air would lead to the AMM reading more mass than actually present, and a rich condition, but obviously this is just speculation.
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  #14  
Old 27th March 2008
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And could explain the perception of the car feeling quicker without the meshes. Engines with a leaner fuel mix feel more torquey because the mixture's burns quicker.
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Old 28th March 2008
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Quote:
Originally Posted by Matthew
Air does not flow well through a mesh. Easy to test - blow on the back of your hand, then try it with the mesh.

The AMM's calibration is based on those screens beign present in the airflow. Removing them will make a difference, but what exactly? Without measurements from sensors it's all speculation.

In particular, I'd be interested to see with-screen and without-screen AFR plots.
Autospeed did measure the pressure drops, but as far as I know there aren't any power figures for pre/post meshes.
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  #16  
Old 28th March 2008
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Quote:
Originally Posted by Matthew
Air does not flow well through a mesh. Easy to test - blow on the back of your hand, then try it with the mesh.


Quote:
Originally Posted by Matthew
The AMM's calibration is based on those screens beign present in the airflow. Removing them will make a difference, but what exactly? Without measurements from sensors it's all speculation..
I honestly think the mesh is part of the AMM design, its function I believe is to help eddy and disturb the airflow into the side channel in the AMM, the platinum wire is tucked into small side channel, its not right in the middle of the AMM main pipe, so what is it measuring? its not a true Anemometer so its not measuring direct airflow or speed.

Why does it have two mesh screens when only one is needed, the wire is so far away from anything that could reach it, this is why I believe its part of the AMM system as well.

From what I understand the platinum resistor is constantly heated and the resistance in ohms is measured, the resistance changes with the airflow over the platinum resistor, if less air cools down the AMM wire, then the resistance is higher simulation a lean condition, there is no way for me to direct more air into the channel safely so I can't test the higher airflow over the wire making a cooler wire, or rich condition theory, the variable resistor that allows me to alter the impedance of the AMM is part of the platinum wire circuit, the voltage and current into the wire is constant, the only variable is the resistance with airflow over it.
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  #17  
Old 28th March 2008
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Quote:
Originally Posted by ShadowWorks
the platinum wire is tucked into small side channel, its not right in the middle of the AMM main pipe
It is on LH2.2 cars. Lucas CU14 AMMs have the filament in the side channel.
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  #18  
Old 28th March 2008
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Quote:
Originally Posted by Matthew
It is on LH2.2 cars.
Same on 2.4!
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  #19  
Old 28th March 2008
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Wasn't sure! We never got LH2.4 here.
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  #20  
Old 28th March 2008
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Quote:
Originally Posted by Matthew
Wasn't sure! We never got LH2.4 here.
Lucky you!
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