Round up & reviews ....... Air intakes

Dippy

Registered User
When DTUK launched their tuning box for the CREC engine (which I have) I first took an interest in how the V6T is controlled, based on the Audi study guide (which is dated 2008 but I think it still applies). What I immediately saw was that (in contrast to the engine in my last car - the 2.7 V6 biturbo), there is no mass air flow sensor (MAF). The V6T has a manifold absolute pressure sensor (MAP - G71) and two charge air pressure sensors (G31/G447) as well as associated temperature sensors. The ECU uses theses sensors to calculate the air mass, which is of course the main input for determining fuelling etc. Quote "This air mass is a key input variable of the torque-based engine management system, which determines the injection rate, injection timing and ignition advance angle."

It was this knowledge which made me wonder how the DTUK box, which only connects to the charge air pressure sensor for each bank and the crankshaft sensor, controls fuelling in addition to just fooling the engine into achieving higher boost. I never got an answer for this.

But now it makes me wonder about this idea of using a flap in the intake to affect performance. Another quote from the guide is "The signal generated by the manifold absolute pressure sensor G71 upstream of the throttle valve control module is used to determine the nominal position of the bypass valve. This information is required to set the required charge pressure. This nominal position of the bypass valve depends largely on the pressure level upstream of the supercharger module." So clearly if there is valve in the intake, it can be used to restrict air flow and this will result in a lower pressure at the manifold. G71 will sense this and as per the quote the bypass valve position will change and so will the "required charge pressure".

This is still not totally clear in my mind but based on the words it seems to me that this variable intake could indeed increase low down torque. I am with @xpoweruk that low down torque is not a problem with this engine but I am also with @Fctaff that it would be great to find out if it really does work and by how much since I'll have more torque anyway 'cos I love it! :)
 

xpoweruk

TTTS 8J Smile Machine
Indeed.after looking into things it does seem that the outcome will be interesting.
 

skiptowncat

Registered User
@Dippy

If you look at a log of the v6t, as soon as you mash the go pedal, the bypass closes fully. It may help at part throttle situations but nothing that pressing the pedal more wouldn't already achieve. I concede It could possibly make the bypass close a touch earlier than normal.

In regards to the tuning box, the ecu will control the fuelling based on the volume and temperature of air coming in. It will then use signals from the o2 sensors to adjust accordingly to achieve desired afr targets. As far as I've read, these engines run in full time closed loop.

I'm not slating the intake, I welcome the testing and love a Good technical discussion.
 

Dippy

Registered User
@skiptowncat have you looked at that self-study guide. There's a graph in there that implies that control of the bypass valve is not a simple as you suggest.

My point about the tuning box is that it only taps into the charge pressure and crank sensor (which I assume is only to measure rpm). So by sending signals to the ECU which are less than the actual pressure, the box can fool the ECU into allowing the boost to be higher. However the ECU thinks it is lower and so will calculate lower air mass and hence fuel for less air than is really entering the engine. To me it appears that with such a tuning box the V6T would run lean.
 

skiptowncat

Registered User
@skiptowncat have you looked at that self-study guide. There's a graph in there that implies that control of the bypass valve is not a simple as you suggest.

My point about the tuning box is that it only taps into the charge pressure and crank sensor (which I assume is only to measure rpm). So by sending signals to the ECU which are less than the actual pressure, the box can fool the ECU into allowing the boost to be higher. However the ECU thinks it is lower and so will calculate lower air mass and hence fuel for less air than is really entering the engine. To me it appears that with such a tuning box the V6T would run lean.

Although I'm not 100% sure about how the simos ecu works. I would suspect there is a load target based on rpm's and accelerator pedal position. The supercharger produces a set amount of boost per revolution with the bypass valve opening to control the load.

Regarding the tuning box, if the o2 sensor is showing lean then it will add fuel to make it up. In this case the long term fuel trims would be showing as quite high, maybe you could do a log to confirm this?
 

Dippy

Registered User
I don't have a tuning box! I prefer a 'proper' tune, but have to wait until the SIMOS 16 is cracked.
 

mdmay

Registered User
Did these reviews on the intakes happen. I have a revo intake and it seems to make a great nice but not sure it's any better than the MRC modified airbox

Sent from my ONE A2003 using Tapatalk
 

Lavis89

Well-Known Member
Regional Rep
Not sure tbh. But for people interested in intakes, ECS have released a few new bits, you can buy just the intake tube now which is a much more reasonable cost than the full kit
 

mdmay

Registered User
Does anyone have the detail of what MRC do to the airbox when they modify one? I would like to do a comparison of it versus the revo intake to see what one works better
 

mdmay

Registered User
Interesting thread that. It seems to indicate that the biggest gains came from the modified airbox that the intake system
 

xpoweruk

TTTS 8J Smile Machine
The way I read it , the biggest gains came from the AFE filter.
I think for the full picture the CTS intake pipe with an AFE filter would need to be tested
 

mdmay

Registered User
Does anyone know what is the largest air filter you can buy that will go into the standard airbox

Sent from my ONE A2003 using Tapatalk
 

Fctaff

Registered User
No just as I thought, the negativity here did not sit well.

I continue to test full time, I have done many tests since. They are in Performance Audi magazine and the Audi club Facebook page.

The K&n is for sale, there is a forge intake pipe too. Pm me an offer.
 

ANDYTQ

Registered User
I have the mrc k&n in the stock box with the intake pipe they sell (034),they said for st2 they mod the airbox as well.
 
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