VAGCOM logs - very low boost in low revs

[sabikeuk]

As you can see I have a huge difference between requested and actual boost and also N75 is on 87,5%. Does somebody know what it means?

'003		
Engine RPM	Air Mass Flow	Throttle Opening

/min	 g/s	%
2120	34.44	87.8
2480	43.31	94.5
2920	56.69	99.2
3360	74.14	100
3920	102.28	100
4520	137.36	100
5120	166.25	100
5760	184.72	99.6
6360	191.39	100
6720	122.28	36.1
4880	10.36	8.2
3120	8.11	6.3
4000	8.89	6.7
3080	7.69	6.3
2760	6.64	5.5

'115			
Engine Speed	Load	Cmd Pressure	Press @ Intercool

/min	%	 mbar	 mbar
1960	48.1	1130	1020
[b]2200	86.5	2290	1110
2640	92.5	2410	1200
3080	103	2390	1290
3560	118	2440	1460
4120	139.8	2510	1710
4680	166.2	2430	1990
5320	169.2	2420	2090
6000	166.2	2340	1960
6520	157.1	2190	1930[/b]
6200	12	1010	1420
4280	12	1010	1060
2680	13.5	1010	1050
3720	12.8	1010	1040
2960	12.8	1010	1040

N75
2000	30	87.5	1040
2320	28	87.5	1150
2800	27	87.5	1230
3240	26	87.5	1340
3760	26	87.5	1550
4280	26	87.5	1780
4920	27	87.5	2060
5560	28	87.5	2050
6160	30	87.5	2010
6680	32	87.5	1990
5520	32	0	1140
3760	33	0	1050
2120	34	0	1040
3160	35	0	1040
2880	35	0	1040

Edited 16 May, 2009 by mannyo
make the table more legible.

[martziniuk]

What car is it? Looks like the n75 is jammed or receiving the wrong signal.

[sabikeuk]

What car is it? Looks like the n75 is jammed or receiving the wrong signal.

Hi, it is AUDI TT 1.8T (225BHP). Yes you are right N75 measuring are strange but I have changed N75 for brand new from audi and measuring are exactly same ....any idea?

[martziniuk]

Does it have a remap, if so who by?

[sabikeuk]

Does it have a remap, if so who by?

I bought it like this so I have no idea and I think so because cmd press is about 2500 mbar = 1,5 bar, stock is about 1 bar!

By the time I have changed N75, MAF, did 031,032 logs for boost leak but everything seems fine...

[martziniuk]

possible DV leak? Weak wastegate spring?

[sabikeuk]

possible DV leak? Weak wastegate spring?

I have hyperboost DV 1 year old. Could a faulty n249 do this?

[cheezemonkhai]

I'd suggest that you have a remap or a tuning box which has not taken into account that a turbo can't produce a lot of boost at low revs.

It doesn't matter if i ask for 1 squillion bar of boost below say 2000 rpm, there simply isn't going to be enough exhaust gas to give me that amount of boost. A turbo works off exhaust gas and at low revs there isn't much of this flowing to spin up the compressor to deliver the requested boost.

IMHO I'd be looking at the amounts requested at low revs and considering if they are feasible with the exhaust input to the turbo and the turbo's specification.

Also I may be missing something, but surely 2500 millibar = 2.5 bar not 1.5 bar.

If a standard car provides 1bar boost on turbo at 2000rpm then asking for 2.5 times that from the same turbo just isn't going to happen.

[ap0gee1978]

Also I may be missing something, but surely 2500 millibar = 2.5 bar not 1.5 bar.

If a standard car provides 1bar boost on turbo at 2000rpm then asking for 2.5 times that from the same turbo just isn't going to happen.

Depends if it's 'absolute' or 'gauge'!

[martziniuk]

So at peak its pulling just nearly 1.1 bar. I'm not familiar with what the k04 usually pulls on a remap but that isn't a disaster. Are you running any other mods which could restrict air flow like an FMIC or crappy air filter?

[sabikeuk]

Depends if it's 'absolute' or 'gauge'!

Yes exactly 2500 - 1013 atmosferic press = about 1500mbar = 1,5 bar

[sabikeuk]

I'd suggest that you have a remap or a tuning box which has not taken into account that a turbo can't produce a lot of boost at low revs.

It doesn't matter if i ask for 1 squillion bar of boost below say 2000 rpm, there simply isn't going to be enough exhaust gas to give me that amount of boost. A turbo works off exhaust gas and at low revs there isn't much of this flowing to spin up the compressor to deliver the requested boost.

IMHO I'd be looking at the amounts requested at low revs and considering if they are feasible with the exhaust input to the turbo and the turbo's specification.

Also I may be missing something, but surely 2500 millibar = 2.5 bar not 1.5 bar.

If a standard car provides 1bar boost on turbo at 2000rpm then asking for 2.5 times that from the same turbo just isn't going to happen.

To be honest I don't know, I bought that car like it is now, just have done vagcom log a few weeks ago and it looks like that it is remapped because cmd press (requested by ecu) is about 2200-2500mbars (1,5bar) in compare with standard TT 225 which have about 2000mbars (1bar) in peak.

What I know is that I have seen logs from another remapped TT's and they looks very differnent - please see attached file. As you can see at revs about 2600 rpm he has actual press 1730 but I hava only 1200 = 0.2 bar:confused:.

Another issue I just found is that in higher revs around 4-5000 rpm I can hear strange voice like "HHUUUUU" as well when I put gas off - any idea? It is like from the exhaust but I am not sure...:(

[sabikeuk]

So at peak its pulling just nearly 1.1 bar. I'm not familiar with what the k04 usually pulls on a remap but that isn't a disaster. Are you running any other mods which could restrict air flow like an FMIC or crappy air filter?

K04 remapped supposed to pull about 1,5 - 1,6 bar, 1 bar pulls standard TT 225bhp.

I have nearly new induction kit BMC CDA....FMIC is standard.

[martziniuk]

When you let off does it sound like the DV releasing pressure? If you have the original DV you could try that to see if it helps. If it sounds like it's coming from the exhaust another option maybe Possible cat collapse,this would create back pressure and stop spool up.

[sabikeuk]

When you let off does it sound like the DV releasing pressure? If you have the original DV you could try that to see if it helps. If it sounds like it's coming from the exhaust another option maybe Possible cat collapse,this would create back pressure and stop spool up.

I have aftermarket DV - I think HX hyperboost (on the photo), Yes I can hear releasing voice but I am not sure if it is from Induction kit or from DV:rolleyes:?

How can I check via vagcom that cat is collapsing?

Edited 26 May, 2009 by sabikeuk

[martziniuk]

It will be the DV echoing down to the induction kit. Is that the noise you were talking about when you said it sounded like it came from the exhaust?

[sabikeuk]

It will be the DV echoing down to the induction kit. Is that the noise you were talking about when you said it sounded like it came from the exhaust?

Hmmmm.......It is hard to say but it could be possible?....but I can hear somethink like .....psssstttt.... when I change gear and I can hera it in e.g. 3000 rpm but that another voice is much different and louder....could it be this echo from DV to induction kit? Is there something wrong?

[martziniuk]

The psssttt will echo down the pipes to the filter when you change gear and let off, they should sound the same. You need to assertain what other noises you are hearing.

[sabikeuk]

The psssttt will echo down the pipes to the filter when you change gear and let off, they should sound the same. You need to assertain what other noises you are hearing.

Okay, I can hear pssssst every time when I let off gas (when I change gear).

But that another sound is in higher revs and it is like thunder..HMMMMMM….like if I have a small hole in exhaust. It’s occur only when system is under boost, I mean if I din’t drive a car before and try to revs engine up to 6000 rpm with no gear I can’t hear it but when I drive I can here it in high revs during accelerating or if I just revs the engine with no gear up to high revs.

Could it be TURBO?

[martziniuk]

check around the turbo and manifold for leaks, especially the 3 bolts on the turbo. These engines sometimes have a habit of undoing the bolts.

[cheezemonkhai]

I take it your dump valve is a recirc valve?

I'm still taking a punt that the vag com oddities are just a remap askling for more than can possibly be delivered.

[sabikeuk]

check around the turbo and manifold for leaks, especially the 3 bolts on the turbo. These engines sometimes have a habit of undoing the bolts.

Turbo is behind an engine, I haven't got clue how to get there...?:confused:

[sabikeuk]

I take it your dump valve is a recirc valve?

I'm still taking a punt that the vag com oddities are just a remap askling for more than can possibly be delivered.

Yes I have HX hyperboost dump valve.

Have you seen my post with log from another TT? It hase very different actual boost in revs 2000-4000 if you compare with mine:cool:, so I have very very low boost in that revs and in a peak I have 1 bar what is standard TT.

[martziniuk]

Turbo is behind an engine, I haven't got clue how to get there...?:confused:

From underneath, put on a ramp or axle stands.

[sabikeuk]

From underneath, put on a ramp or axle stands.

I was under the engine today but there is no chance to get Turbo, there is axle and I could not get there....:orb_yuck: