# AUDI TT 1.8T-165kW - weak boost in low revs- help please



## sabikeuk (May 28, 2009)

Last week I did some VAGCOM logs and found out that I have huge difference between CPU requested and actual pressure (block 115) especially in low revs (2000-4000).
I have checked all pipes to intercoolers as well however could not find any leak :? . Have tried geniune new N75 and also new geniune MAF - still same - very poor boost in low revs, at peak I have about 1bar = 15 psi but if you check reading from Vagcom you can see that requested boost is much higher than actual.
Below are VAGCOM logs of blocks 003, 115 and 118. N75 is exactly same as before and pressure as well.
Any idea what could be wrong?

'003
Engine RPM Air Mass Flow
/min g/s
1640 9.92
1800 27.08
2000 31.5
2240 38.03
2520 43.11
2760 48.92
3000 59.33
3320 72.81
3640 84.33
4000 105.53
4440 132.14
4840 156.64
5280 168.61
5720 181.11
6040 185.31
6400 188.06
6720 187.5
6920 187.53
7120 173.78
'115
Engine Speed Load Cmd Pressure Press @ Intercool
/min % mbar mbar
2160 84.2 2230 1050
2400 88.7 2330 1130
2640 94 2370 1170
2920 101.5 2350 1230
3240 109.8 2370 1320
3560 118 2400 1440
3920 133.1 2450 1590
4280 151.9 2440 1770
4720 170.7 2370 1990
5200 171.4 2390 2030
5640 167.7 2400 2010
6000 170.7 2300 1980
6320 161.7 2240 1970
6640 151.1 2130 1930
6960 132.3 2050 1970
7120 60.9 990 1920
'114
Spec. Load Load Correction Actual Load N75 Duty Cycle
% % % %
127.1 125.4 12.8 0
127.1 125.4 72.9 87.5
140.6 138.8 77.4 87.5
166.9 165.7 84.2 87.5
178.2 176.1 88.7 87.5
182.7 180.6 91.7 87.5
185.7 183.6 97.7 87.5
188 186.6 104.5 87.5
191 189.6 115 87.5
191.7 192.5 127.1 87.5
191.7 194 142.9 87.5
191.7 195.5 161.7 87.5
191.7 194 169.9 87.5
191.7 192.5 165.4 87.5
186.5 185.1 160.9 87.5
172.9 171.6 155.6 87.5
165.4 164.2 150.4 87.5
159.4 158.2 141.4 87.5
159.4 155.2 142.9 84.7


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## sabikeuk (May 28, 2009)

bump...


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

anybody?


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

bump


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## animaniac (May 26, 2005)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

Have you checked the pvc pipes?
The one under the intake which runs to the T-peice, this pipe also has a one way valve, which allows vacuum under idle to the inlet manifold, but it closes under boost, and the engine fumes get sucked in by the turbo.
You will probably have a split in this pipe, and or the valve is stuck open.


















_Modified by animaniac at 2:25 PM 6-9-2009_


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (animaniac)*


_Quote, originally posted by *animaniac* »_Have you checked the pvc pipes?
The one under the intake which runs to the T-peice, this pipe also has a one way valve, which allows vacuum under idle to the inlet manifold, but it closes under boost, and the engine fumes get sucked in by the turbo.
You will probably have a split in this pipe, and or the valve is stuck open.

















_Modified by animaniac at 2:25 PM 6-9-2009_

Hi thanks for great info, I will try to check it tomorrow . Do you know what type of the valve it is? Can I check it via VAG COM?


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

How can I find out that valve is stuck opened?


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (animaniac)*

The latest update...I have fixed that broken vacuum hose and also found another broken hose (see photo) however I don't feel that it is as it should be. Maybe power increased slightly but it definitely not pushing me down to seat .
Any idea somebody?


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## animaniac (May 26, 2005)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*


_Quote, originally posted by *sabikeuk* »_How can I find out that valve is stuck opened? 

Sorry to reply late, i've been busy, that little valve is just a one way valve.
Ecs tuning sells them $14.42








Best way to test pull the pipe off the manifold and try and blow through it.
As you can see in the pic the black end goes into the T bit and the hose goes on the white part.








I hope this helps...
I see your in the uk, so you can get them from the dealer




_Modified by animaniac at 6:21 PM 6-29-2009_


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## 01ttgt28 (Jun 23, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

i was having problems with boost also shop had to bypass the n75 with manual controoler we tryed ecs race and stock same problem only happend whe i switched to gt2871r and revo stage 3 550 file hope this helps dont buy the ebay on they dont work


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (animaniac)*


_Quote »_Best way to test pull the pipe off the manifold and try and blow through it.

THANKS FOR REPLY,
If I am able to blow through is it fine or faulty?
Anyway my N75 duty cycle is always 87.5% under full throttle – I have seen logs from mapped TT’s but their duty cycle circulate between 70-80% - never was same % as mine is ( I have tried brand new N75 and it was exactly same = 87.5%) – any idea if it is right?

As you could see from my post I have found 2 leaks but problem still persist.







.
Do you think problem in vacuum system could make so low boost (logs are in first post up)?


_Modified by sabikeuk at 3:54 AM 6-30-2009_


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## animaniac (May 26, 2005)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

If you can blow through it it's faulty, because when your blowing on it, thats equivalnt to the turbo presurising the manifold.
Also to check are the brake servo pipe, which runs from manifold to brake servo, this also has a check valve on it, but if that leaked i dont think it would make any difference because the servo is sealed and under vacuum for the brakes to work.
Another pipe to check is the pipe which runs from the throttle to the turbo intake pipe and has a join to the carbon canister, this also has a one way valve which allows the fumes from the carbon thing to get sucked in by the manifold under idle, but once under pressure the valve closes and the fumes then get sucked in by the turbo.
So it's worth blowing on that pipe aswell, in fact blow through any pipe which connects to the manifold, non should allow you to blow through them..
Also a worn diverter valve will cause low boost.

Just to note your saying low boost at low revs, well your going to get low boost at lows revs because
1. your only using partial throttle, and the dv is being sucked open by manifold vacuum.
2. the engine isnt producing enough rpm to spin the turbo enough for sufficiant boost, which is known as boost threshold.
Theres normaly only a boost problem if your getting lower boost at wide open throttle.
It should peak or spike at 20 ish and drop down to the maximum level 1 bar if remapped.

I may not be a boost leak but a worn map sender.


_Modified by animaniac at 6:14 AM 6-30-2009_


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (animaniac)*


_Quote »_Another pipe to check is the pipe which runs from the throttle to the turbo intake pipe and has a join to the carbon canister, this also has a one way valve which allows the fumes from the carbon thing to get sucked in by the manifold under idle, but once under pressure the valve closes and the fumes then get sucked in by the turbo. 

Could you mark where is that pipe(one way valve) on that attached picture please? 

_Quote »_ Also a worn diverter valve will cause low boost. 
 I have an aftermarket DV not Bosch, I didn’t buy it It came with car. I have tried to test it and it hold the air-I believe it is HX hyperboost DV.

_Quote »_I may not be a boost leak but a worn map sender. 
 I am sorry but I have no idea what is “worn map sender” – could you please explain?
Anyway your info is great and very useful for me, thank you very much for help!
Daniel










_Modified by sabikeuk at 3:04 PM 7-1-2009_


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## animaniac (May 26, 2005)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

It's not on your diagram, i've found one








The carbon canister is number 2 and as you can see the pipe runs from turbo intake to throttle and the valve is 21 you also have another number 3 but the turbo is always sucking vacuum so it wouldnt make much difference if the was stuck open, but no. 21 would give you a boost leak.
I took mine off at the throttle and blew in the pipe and mine works ok, pressure built up in my mouth...
I also tested the brake servo valve which is number 8, same again just unlclipped pipe from manifold and blow...
And if the pressure doesnt build up you have a leak..
With regards to the map sender, which measures boost, thats number 17 on your diagram.
That could or could not be faulty, not all faulty senders bring up codes, but you can view the logs and go from there...




_Modified by animaniac at 7:24 PM 7-1-2009_


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (animaniac)*

Thank you again for great info.
I just wonder if any of these valves are faulty wouldn’t I get any fault code? I have scanned ECU and no fault codes at all?
I have done another leak test today but I only was able to pump 15psi, the hoses were full of air anyway but I couldn’t hear any air coming …. I will try to check these valves….no.18 is PCV valve isn’t it?
How about my N75? linear 87.% duty cycle....
I have blown through that pipe where is yellow line - disconnected from TB, is that valve in yellow circle on the picture?










_Modified by sabikeuk at 10:07 AM 7-2-2009_


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

I have also unplugged hose which goes from N75 to actuator and connected pump to it, set 1psi on pump and started pump. In half sec pump stopped and actuator rod moved immediately. However when I looked to pump there was 27 psi :? .....when I unplugged pump rod moved back. 
Does it mean that actuator hold 27psi and it works properly?

Anyway I have decided to test again my DV. I pushed the piston of the valve upwards against the spring (it moved without restriction). Then with the piston pushed fully up, with the spring compressed, I placed my finger over the top nipple to form a
seal. see photo 1








Then I released the piston, keeping my finger in place but piston moved about 5 mm down - see photo 2








After I removed my finger from the nipple, at which point the piston travelled another 2 mm back and made noise (shoot).








Here is re-assembled DV - I don't know what type is it - it was on the car when I bought it.








I have tested it maybe 10 times with same result. Dost it working properly or is it faulty?


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*


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## HidRo (Sep 19, 2003)

Search for pressure test, and build the pressure test thingy...
Test your system to see if you do have an extra leak.
Sounds a bit like it...


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## sabikeuk (May 28, 2009)

*Re: (HidRo)*

I have done a pressure test yesterday, was able to pump up to 15 psi but couldn't hear/see any leaks







. Hoses were full of air and hard to push so I assume I haven't got a boost leak.


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## dbn23quattro (Apr 8, 2008)

*Re: (sabikeuk)*

You can look at block 32 to see if its a leak. If your multiplicative trim is in the -5% range or less then you probably have a leak somewhere, and if its in the + range then its not a leak. Keep us updated because I'm currently having the same problems as you, but I haven't been able to run any logs yet


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## sabikeuk (May 28, 2009)

*Re: (dbn23quattro)*


_Quote, originally posted by *dbn23quattro* »_You can look at block 32 to see if its a leak. If your multiplicative trim is in the -5% range or less then you probably have a leak somewhere, and if its in the + range then its not a leak. Keep us updated because I'm currently having the same problems as you, but I haven't been able to run any logs yet









Are you definitely sure that if -5 or less it means a leak? I have read this:"If Fuel Trims are Negative more than 5% in the load range there is a very good chance that there is a leak after the turbo.".
Anyway my 032 block:
Idle Value	Part Throttle Value
TIME 
/min	STAMP	%	%
1960	0.4	0.4	-4.7
2280	1.71	0.4	-4.7
2680	3.02	0.4	-3.1
3120	4.22	0.4	-3.1
3600	5.53	0.4	-3.1
4160	6.75	0.4	-3.1
4840	7.98	0.4	-3.1
5480	9.26	0.4	-3.1
6120	10.56	0.4	-3.1
6600	11.79	0.4	-3.1
So in under load it is - 3.1%, when I released gas it was -4.7%.


_Modified by sabikeuk at 7:19 AM 7-4-2009_


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## JettaRed (Aug 14, 2000)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

The piston on your dv should have moved all the way back and closed off the side opening completely. Only under vacuum, such as between shifts, should it open to allow boost to be diverted into the turbo intake hose. If it's staying open, then that's your problem. Try a different DV.


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (JettaRed)*


_Quote, originally posted by *JettaRed* »_The piston on your dv should have moved all the way back and closed off the side opening completely. Only under vacuum, such as between shifts, should it open to allow boost to be diverted into the turbo intake hose. If it's staying open, then that's your problem. Try a different DV.

To be honest I don't understand what you mean....do you think is my DV faulty?
Anyway I have done some logs today and in high revs 5500-6500 I heard strange voice







like rally car has ...."hhmmmhhmmmmm" it happened under WOT and also when I released gas pedal ....







so far so bad.....


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## dubinsincuwereindiapers (Jan 16, 2008)

*Re: (sabikeuk)*

x2.. stick your stock dv back on and see if it gets better


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## sabikeuk (May 28, 2009)

*Re: (dubinsincuwereindiapers)*

unfortunately I haven't got original DV because I bought car like it is now with this DV already installed on.


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (animaniac)*


_Quote, originally posted by *animaniac* »_If you can blow through it it's faulty, because when your blowing on it, thats equivalnt to the turbo presurising the manifold.

Have tried today and I could blow through it so probably it is fine.

_Quote, originally posted by *animaniac* »_Another pipe to check is the pipe which runs from the throttle to the turbo intake pipe and has a join to the carbon canister, this also has a one way valve which allows the fumes from the carbon thing to get sucked in by the manifold under idle, but once under pressure the valve closes and the fumes then get sucked in by the turbo.

Also tried and couldn't blow through it.


_Quote, originally posted by *animaniac* »_Also a worn diverter valve will cause low boost.

Upper is my DV and how I test it .... 
Also have done another leak test up to 15 psi and could find any leaks. (Before I didn't tight one clips on the hose to IC and I was able to pumo only 12 psi and could hear air = I assume that if I couldn't hear air at 15 psi = there is not a leak.....










_Modified by sabikeuk at 4:10 PM 7-4-2009_


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## JettaRed (Aug 14, 2000)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*


_Quote, originally posted by *sabikeuk* »_
To be honest I don't understand what you mean....do you think is my DV faulty?


The piston should completely close off the side hole when in boost. Vacuum pulls it open. When boosting, it should be completely closed.
Yes, your DV is faulty. Replace it with a stock 710N dv or just replace the spring. Forge sells springs and rebuild kits.


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (JettaRed)*


_Quote, originally posted by *JettaRed* »_
The piston should completely close off the side hole when in boost. Vacuum pulls it open. When boosting, it should be completely closed.
Yes, your DV is faulty. Replace it with a stock 710N dv or just replace the spring. Forge sells springs and rebuild kits.

It is not a Forge I am not sure if I can use Forge spring, I have remapped car so stock 710N is not very good idea....


_Modified by sabikeuk at 4:12 PM 7-4-2009_


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## JettaRed (Aug 14, 2000)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*


_Quote, originally posted by *sabikeuk* »_
It is not a Forge I am not sure if I can use Forge spring, I have remapped car so stock 710N is not very good idea....


What brand is it? The forge spring will probably work. There is nothing wrong with the 710N, especially if you want a diaphragm DV--works as well as an APR1 I had. The 710N is stock on the TT225.
So, either spend $135 for a forge 007P or get a 710N. What are you supposed to be boosting to?


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (JettaRed)*


_Quote, originally posted by *JettaRed* »_
What brand is it? The forge spring will probably work. There is nothing wrong with the 710N, especially if you want a diaphragm DV--works as well as an APR1 I had. The 710N is stock on the TT225.
So, either spend $135 for a forge 007P or get a 710N. What are you supposed to be boosting to?

I don't knowwhat brand, got it with my car







.
I believe 710 will fail soon on mapped TT, I supposed to boost 1,5 (22psi) bar but only getting 1 bar (14,5 psi). 
Block 115 
115
Engine Speed Load Cmd Pressure Press @ Intercool
/min % mbar mbar
2160 84.2 2230 1050
2400 88.7 2330 1130
2640 94 2370 1170
2920 101.5 2350 1230
3240 109.8 2370 1320
3560 118 2400 1440
3920 133.1 2450 1590
4280 151.9 2440 1770
4720 170.7 2370 1990
5200 171.4 2390 2030
5640 167.7 2400 2010
6000 170.7 2300 1980
6320 161.7 2240 1970
6640 151.1 2130 1930
6960 132.3 2050 1970
7120 60.9 990 1920


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## animaniac (May 26, 2005)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

With regards to the dv your testing the vacuum port and thats working ok because it holds.
But i can't tell if the valve is fully closing, to test blow through the dv, if air comes out the other end then that will cause a boost leak and will allow the air to recirculate.
I had major boost leaks on my 1999 golf 1.8t (agu) splits in pcv pipes and the dv was very worn, and no fault codes came up, obviously due to it not having a map sensor, if it did have a map sensor it would know plenty of air's passing the maf but the boost is too low and would throw a low boost fault.


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## JettaRed (Aug 14, 2000)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (animaniac)*


_Quote, originally posted by *animaniac* »_
I had major boost leaks on my 1999 golf 1.8t (agu) splits in pcv pipes and the dv was very worn, and no fault codes came up, obviously due to it not having a map sensor, if it did have a map sensor it would know plenty of air's passing the maf but the boost is too low and would throw a low boost fault.

Yeah, I'm kinda surprised he hasn't gotten a low boost fault code.


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (JettaRed)*


_Quote, originally posted by *JettaRed* »_
Yeah, I'm kinda surprised he hasn't gotten a low boost fault code.

Any idea why?


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (animaniac)*


_Quote, originally posted by *animaniac* »_With regards to the dv your testing the vacuum port and thats working ok because it holds.
But i can't tell if the valve is fully closing, to test blow through the dv, if air comes out the other end then that will cause a boost leak and will allow the air to recirculate.
 I am pretty sure it is staying close....

_Quote, originally posted by *animaniac* »_I had major boost leaks on my 1999 golf 1.8t (agu) splits in pcv pipes and the dv was very worn, and no fault codes came up, obviously due to it not having a map sensor, if it did have a map sensor it would know plenty of air's passing the maf but the boost is too low and would throw a low boost fault.
 My manifold press in idle is 270mbar any idea if it is right? Can I measure vacuum via VAG COM?


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## JettaRed (Aug 14, 2000)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*


_Quote, originally posted by *sabikeuk* »_ I am pretty sure it is staying close....
My manifold press in idle is 270mbar any idea if it is right? Can I measure vacuum via VAG COM?

at idle, it should be in vacuum. does 270 mbar represent vacuum? for example, 1000 mbar is 0 psi? It also matters whether you have the a/c on or not.


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (JettaRed)*

yes it should be like 1000mbar is 0psi, so if manifold press is only 270mbar (A/C off) it is about 7.973 in Hg but what I know it should be about 20 in Hg....


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## JettaRed (Aug 14, 2000)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

That would imply a vacuum/boost leak. Have you actually done a smoke test? Smoke machines are $$$, so you probably need to take your car to a mechanic. You connect the machine to a port on the intake manifold, say the fpr nipple or some other nipple, and pump smoke into the engine. Then you look to see if the smoke starts coming out somewhere.


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (JettaRed)*


_Quote, originally posted by *JettaRed* »_That would imply a vacuum/boost leak. Have you actually done a smoke test? Smoke machines are $$$, so you probably need to take your car to a mechanic. You connect the machine to a port on the intake manifold, say the fpr nipple or some other nipple, and pump smoke into the engine. Then you look to see if the smoke starts coming out somewhere.

Do you still think that I could have a leak somewhere? Do you think smoke spray from ebay + leak tester will make a trick? I pumped 15 psi and couldn't hear it.



_Modified by sabikeuk at 8:08 AM 7-5-2009_


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

The N75 shouldn't be at a constant figure like that across the whole range.
In theory, if the requested boost isn't achieved, the N75 should close the wastegate more, to allow the requested to be met. But the N75 value isnt changing. Could it be by "****" map-chip?


_Modified by sabikeuk at 12:18 PM 7-6-2009_


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

I have heard strange voice from engine "again" - yes again, I heard it before...it happened in higher revs about 5500 revs under acceleration or if i released gas...it is like "whhhooooo".....any idea?
Update...I was driving car today at 5-6000 rpm, kept rpm in these revs and that voice is very load under gas and also when I released gas....it is like if I have leaky exhaust but I don't ...similar like world rally cars have...











_Modified by sabikeuk at 2:33 PM 7-7-2009_


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

Hi guys,
I just have found out that position of nut on the rod actuator is different on my TT and the other TT with same engine……Another TT has nut from end of rod to outside of the nut 16 mm however I have only 10 mm!!! 

Could it cause a problem????









_Modified by sabikeuk at 1:08 PM 7-10-2009_


_Modified by sabikeuk at 1:09 PM 7-10-2009_


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## sabikeuk (May 28, 2009)

*Re: AUDI TT 1.8T-165kW - weak boost in low revs- help please (sabikeuk)*

I have moved these 2 nuts on actuator rod (it took me 1 hours to move them 6mm!!!) but it worth ....now I have boost from 2000 rpm, car pushing like never before and I am very happy so far ....
I hope it solve the problem....
Thanks anyway to all of you who tried to help me!!!
Daniel


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