In the interest of balance, I found this,
May change your minds!!
I especially laughed at the "stuffed some rags in the intake " part !!
Rather a crude and simple way of making all this sound like bo**ocks !
It has been suggested that significant airflow can be gained by removing the MAF pre-screen, so I decided to test that theory with VAG-COM air flow measurements. I did 3rd gear runs, both with and without screen, on the same stretch of road, and the tests were within 15 min of each other. The car was at full operating temp for both tests (i did some driving around before testing.)
In both cases the curves basically matched each other and leveled off in the 250-260 g/sec range at higher RPMs. In fact if anything, WITH the screen gave a measurement of a couple grams higher at some RPMs.
Now I also have an AWE intake. Interestingly enough my g/sec graph mysteriously matches donps in the K&N filter testing article, esp. at higher rpms. Both of us level off at just under 260 g/sec. Coincidental? Maybe, he likely has different mods on his car, the test conditions were different, etc. so no comparison can really be made. Still, I wish I had enough ambition to put my stock filter back in and retest to see if the AWE intake really makes 25g/sec difference... i.e. does my car really only flow 230 g/sec with the stock filter???
As one more test I stuffed a rag into the snorkel inlet behind the grille, significantly choking it down to a small gap where air could get through. I would say it blocked a good 60-70% of the narrow rectangular inlet which isn't very big to begin with. Even in this test it lowered the MAF intake by only 10 grams/sec (it still hit just under 250 grams/sec). However turbo lag was definitely more noticable. Still, this shows that unchoking a major restriction only added 10g/sec. Again, and the AWE intake adds 25 g/sec? Nothing against their intake, I think it is the most ideal setup you could have.
But I have to wonder if ANY intake/filter solution out there is going to add noticable power gains.
2000 6-spd
Interesting.......veeeerrrry interesting
Superb - great counter-stroke.....as you say: this really does make it all sound like b0ll0cks! I read this and thought it may be of interest
Extract taken from http://www.gnttype.org/techarea/turbo/intercooler.html
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).
Extract taken from http://www.gnttype.org/techarea/turbo/intercooler.html
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).
S4B5 Avant
I feel I must add that I was involved in motorsport for many years and in both racing and rallying, engine power outputs are regulated by the fitting of "restrictors" on the inlet to the turbo or (in single-seater racing) the inlet to the airbox. The dia. of which was fixed and measured at pre-race scrutineering.
Also japanese motorbikes were de-powered to meet government limits by a restrictor fitted before the throttle butterfly.
In all these cases power is limited by a physical part blockage of the inlet tract. Obviously a throttle is in fact a variable restriction which governs power. Quite where a fine wire mesh fits in I am not so sure!
It's all similar to the exhaust system, de-catting, pipe bore, single/dual etc. etc. and gasflowing heads, airboxes, filters etc.
There is an optimum point which is sufficient for one particular setup and after that it's all very minimal. Every little bit helps to combine into the most efficient system, it's a case of erradicating the most inefficient parts and improving them to the standard of the most efficient parts.
I reacon the biggest effect of all is.......placebo, but if you're happy then that's the main thing !! For sure, more noise = more power & more speed!! (doesn't it?)
Also japanese motorbikes were de-powered to meet government limits by a restrictor fitted before the throttle butterfly.
In all these cases power is limited by a physical part blockage of the inlet tract. Obviously a throttle is in fact a variable restriction which governs power. Quite where a fine wire mesh fits in I am not so sure!
It's all similar to the exhaust system, de-catting, pipe bore, single/dual etc. etc. and gasflowing heads, airboxes, filters etc.
There is an optimum point which is sufficient for one particular setup and after that it's all very minimal. Every little bit helps to combine into the most efficient system, it's a case of erradicating the most inefficient parts and improving them to the standard of the most efficient parts.
I reacon the biggest effect of all is.......placebo, but if you're happy then that's the main thing !! For sure, more noise = more power & more speed!! (doesn't it?)
This is all really good stuff!
My thoughts?
(1) Dr-Al's first post merely confirms that de-meshing the MAF is a good thing to do when you read it properly (as far as i'm concerned)
(2) Quote: "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)" That's pretty definitive (again, as far as I'm concerned) and proof enough for me!
(3) Quote: "So you can see how just by reducing the pressure drop we can lower the temperatures while still running the same amount of boost." Also pretty explicit......
(4) I always had some doubt in the back of my mind that the boost gauge tap from the IM accurately reflected the actual boost output from the turbos.....and that article confirms it.
Nice find MCB!
Looking forward to the Doc's response.........
My thoughts?
(1) Dr-Al's first post merely confirms that de-meshing the MAF is a good thing to do when you read it properly (as far as i'm concerned)
(2) Quote: "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)" That's pretty definitive (again, as far as I'm concerned) and proof enough for me!
(3) Quote: "So you can see how just by reducing the pressure drop we can lower the temperatures while still running the same amount of boost." Also pretty explicit......
(4) I always had some doubt in the back of my mind that the boost gauge tap from the IM accurately reflected the actual boost output from the turbos.....and that article confirms it.
Nice find MCB!
Looking forward to the Doc's response.........
Deus ex machina
Price ranges massively.
Units - Second hand range in price from just over £100 to about £300 a pair. You'll still need shrouds and pipe work to fit them. Shrouds ~ £50 APR pipes ~£190
Labour - no idea
Flow is everything. One thing to be aware of in turbo pipework is not to make the volume between the turbo and IM to large or lag will increase.
Units - Second hand range in price from just over £100 to about £300 a pair. You'll still need shrouds and pipe work to fit them. Shrouds ~ £50 APR pipes ~£190
Labour - no idea
Flow is everything. One thing to be aware of in turbo pipework is not to make the volume between the turbo and IM to large or lag will increase.
Mark
No response required - it all makes sense. However I was really surprised by the following:S4TAN wrote:Looking forward to the Doc's response.........
So I checked it -The difference in turbo outlet temperature between 23 psi and 17.5 psi is about 40 deg (assuming a constant efficiency)!
The absolute pressures involved are 2.59 Atm and 2.21 Atm respectively. The final temp of a gas (in Kelvin - subtract 273 to get C) after adiabatic compression is calculated as follows (Excel formula):
Tf =POWER(E1/D1,1/(A1/B1))*C1
Where:
A1 = Heat capacity of gas at constant volume (air = 20.84 J mol-1 K-1)
B1 = Gas constant (8.314 J mol-1 K-1)
C1 = Initial Temp (25 C = 298 K)
D1 = Initial pressure (1 Atm)
E1 = Final pressure (in Atm)
If you plug in the values, you get a 27 C difference in the 2 scenarios. Not quite 40 C, but still pretty significant!
Wrecked on 9 Oct 2007: 1998 Cactus Green S4, 710N DVs, Boost gauge (in custom A-pillar/dash mounting pod), cruise control retro-fit, Parrot 3200 Colour Hands Free, RS246.com sticker
I'd go as far as saying "I see no harm in doing it, there may be a small improvement" (you can print that if you like).S4TAN wrote:I'll take this as an official "Dr-Al Seal Of Approval" then
You got that right. In my case I see no point chasing the odd HP here and there when I could get a massive 45 more all in one fell swoop. I just need to win the lottery before I book my place at MRCS4TAN wrote:but i bet you still won't be de-meshing your MAF though will you!)
Wait, what am I thinking, it's £100Million on Friday. How long is the waiting list for a Bugatti Veyron? An extra 720 BHP for a cool ~£830k
Wrecked on 9 Oct 2007: 1998 Cactus Green S4, 710N DVs, Boost gauge (in custom A-pillar/dash mounting pod), cruise control retro-fit, Parrot 3200 Colour Hands Free, RS246.com sticker
In my case I have to chase the "odd HP here and there" as i've already had the MRC custom map treatment, plus pre-cat gutting, Milltek cat-back, K&N + mutilated air-box, HX DV's, Bosch Platin plugs etc blah - the next big step for me would be bigger turbos and i/c's and no cats, bigger injectors etc etc but alas i can't afford that! The next lot of spare cash i get to spend on my car has to go on brakes i'm afraid as they are a wee tad inadequate (to say the least) for the car's current power..... 
Plus the de-mesh costs bugger all - so as i stated in an earlier post: the cost/benefit analysis of doing this was a no-brainer........
Plus the de-mesh costs bugger all - so as i stated in an earlier post: the cost/benefit analysis of doing this was a no-brainer........
You crack me up Doc - gracious to the bitter end.......I'd go as far as saying "I see no harm in doing it, there may be a small improvement" (you can print that if you like).
Deus ex machina
oh i have a set of RS4 IC's and maybe shrouds and even some pipework..but 1st i need to see if the intended purchaser still wants..if not you will find them for sale in the classifieds.. 
GARTH ROAD MOT CENTRE LTD
Unit 2 1-7 Amenity Way Garth rd Morden Surrey SM4 4AX
Exhausts,Clutches,Diagnostics,Tyres,Servicing and Air Conditioning
Opening soon is our new motorcycle Mot bay
020 83353032
Unit 2 1-7 Amenity Way Garth rd Morden Surrey SM4 4AX
Exhausts,Clutches,Diagnostics,Tyres,Servicing and Air Conditioning
Opening soon is our new motorcycle Mot bay
020 83353032
Who is online
Users browsing this forum: No registered users and 42 guests