High Air Inlet Temp. What should it be

[mytA2]

High Air Inlet Temp. What should it be
Hi
Audi TT BAM engine conversions running a standard engine managment, cold air intake, high flow 100cpi cat.

I'm currently suffering with poor fuel efficency not able to achieve more than 30mpg. I know this is not BAD but surely I can do better.

I have logged in using Vag Com and there is a returning fault code with efficency below threshold but the fuel trims are well within limits at -7% and +3%. Engine runs smoothly throughout rev range.

Engine coolant temps run at 90-100 degC

Now I believe the problem lies with the air inlet temp, even under low boost pressures the air temp soon gets up to 40degC, under higher boost temps get up over 70degC.

I do have plans are to fit a front mount intercooler but I would be grateful if someone could educate me a little as to what the air inlet temps should be.

Many thanks

[Crasher]

What fault code numbers are you getting and in which measuring block and field are you reading the temperature?

[mytA2]

Hi Crasher
Thanks for taking a look. This error code keeps coming back not straight away but 10mins or so. I'm sure this is down to the 100cpi cat but would this effect the fuel ecconomy.

Address 01: Engine Labels: Redir Fail!
Control Module Part Number: 8N0 906 018 CB
Component and/or Version: 1.8L R4/5VT G 0003
Software Coding: 10710
Work Shop Code: WSC 12341
Additional Info: TRUZZZ8N541021076 AUZ5Z0CD295007
VCID: 73EE04D46BC7
1 Fault Found:

16804 - Catalyst System; Bank 1: Efficiency Below Threshold
P0420 - 35-00 - -

Readiness: 0000 0000

For obtaining the Intake Air Temp I have looked in group 004 column 4

For fuel trim group 032.

At the moment I havn't tried recording a graph of the intake air temp but I'll let you know how I get on.

[Crasher]

I wouldn’t think that the temp reading you are seeing is too high, that sensor is in the inlet manifold after all. Your cat seems to be of low efficiency.

[mytA2]

file:///C:/DOCUME%7E1/MALCOL%7E1/LOCALS%7E1/Temp/moz-screenshot-3.pngWell I managed to get a graph, please see attachment

The ambient temp was -1degC.

Intel air temp spiked over 40degC.

Exhaust gas temp spiked over 680degC

Got any ideas??

[Crasher]

Looks OK to me.

[mytA2]

I've been told that the engine managment system when it see's temperatures getting to high, over feeds/increases the amount of fuel entering the combustion chamber in an attempt to control/reduce the temp and protect the engine.

Is this true??

If so, can the inlet air temp activate this protection system??

Many thanks for all your help.

[Crasher]

I have to admit to not being completely aware of the exact parameters in the software, I leave that to geeky types but yes, extremely high inlet temps are not good and are often dealt with by adding fuel and puling back the timing but your peak temps do not seem that high to me.

[mytA2]

I have seen in this thread that there is mention of the thermal protection being related to exhaust gas temperature. (bottom of thread)

http://uk-audis.net/forums/t/2001.aspx

With this in mind and looking at the profiles plotted by my inlet air temperature and the cat temperature its no surprise to see the two have similar profiles.

It's no surprise to see this on the log that I got, but I would like to point out the fact that the ambient air temp was -1 degC. What if the ambient air temp was 15-20 degC, I can only imagine the exhaust gas temp would go over 800degC.

I think I'll try talking one of my work colleges into profiling his Golf GTI's inlet air and cat temps, then I would have somthing to compair mine to.

Wish me luck.

[Crasher]

You have an EGT sensor on your engine.

[mytA2]

Yeah?? am I looking in the correct group and blocks??

[Crasher]

Measuring Blocks 08, Display Group 112, Display Zone 1.

[mytA2]

Ahh. I've not seen that one.

I have a copy of a VAG DBW DATA BLOCKS spread sheet listing groups and columns, and group 112 is not listed!! Thats not to say its not there. I give it a look this evening.

Thanks Crasher.

[mytA2]

Got it, I mean group 112 and the EGT

Managed to see exhaust gas temps upto 790degC. Not high enough to worry about right now, but should the weather be hotter the temps could be significantly warmer.

I really need to get a comparison with a standard car/setup.

I'll try and do the comparison over the same distance on the same day.

[mytA2]

Thanks for the reply.

I have two cars with the 20v turbo engine,

1st 225bhp running with a diesel gearbox so most of the driving is low reving 2300rpm on the motorway at 70mph, and the best I've managed on a journey is 33mpg.

2nd 150bhp running totally standard and most of the time I get 37-38mpg without even trying on a journey. I have seen 44mpg on the motorway when I drop my speed to 65mph at 2600rpm, and that was over a distance of 180 miles. Its hard, but achievable.

Ok! I understand the extra bhp will use more fuel but surely in a car thats 300kg lighter running at lower revs, on the motorway at a constant speed, I should be doing better than 30-33mpg. I'm just left scatching my head at the moment.

[Crasher]

My remapped (210PS) Octavia VRS does dead on 40mpg on a long cruise locked on 70mph. Around town I get 23 driven lightly. My wife’s 2007 model Polo 1.8T GTI (standard) gets less than mine on a cruise, about the same around town.

[mytA2]

Well I thought it was about time I updated my findings and achievements.

I have been able to improve on my past MPG results. Surprise surprise my slightly poor MPG was all down to a slightly heavy right foot.

On a journey of around 120 miles, 50/50 motorway/A roads, avoiding town driving and going from fill up to fill up. I was of cause being very strict with the right foot, managed 42mpg. I never used more than 50% throttle on accelleration and avoided braking as much as possible and useing the gears for slowing down.

I mentioned on a prevous post the issue of the ECU over fueling. Now the ECU looks at the Exhaust Gas Temp, NOT inlet air temp, and subsequently adds fuel to drop the EGT. I have been told from a reliable source that the 1.8T BAM engine/ECU is trying to achive an exhaust temp of 919DegC. If the temp goes to 920DegC it will then FUEL FLOOD to reduce this temperature. During my testing I was well away from this, but the ambient temp was -1DegC.

I have also mentioned inlet temps getting quite high. Now I have read that it is desirable to keep the temp below 40DegC and its dangerous to the engine to go above 70DegC.

Thank you Crasher for all your input and I hope this helps someone in the future.

[Crasher]

My work colleague was moaning about his fuel consumption and had spent hours pouring over the data trying to work out what was wrong. Then last Thursday we went out on an evening trip to the John Deere tractor place at Langar and during the journey both ways (especially the return journey) the warp speed trip uncovered for me the real reason for the poor consumption, drive with ones foot firmly buried in the carpet and the car does tend to gulp the juice!