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Discussion Starter · #1 ·
Can anyone tell me what the standard boost pressure on a 225 tt?? just put a boost gauge in and its only boostng at 4psi. and like most of the threads i have read mine hesitates alot in the mid range and then pulls after about 5000rpm!!!!!! the boost pressure stays constant through out the hesitation tho. and i found if i come of the gas to about quarter throttle it clears and picks up as if it over fuelling maybe any ideas?/
 

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welcome to the forum Steve.

standard boost is 0.9bar or about 13psi, some remaps will give >20psi (1.4bar)

The boost sensor on the TT is only good to 2.55bar absolute (1.55bar boost)

Sounds like you might have a boost leak somewhere...probably a split in a hose that opens up under pressure
 

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Discussion Starter · #3 ·
2.55 bar on the boost sensor, sorry but i dont understand i know a little on cars but are you saying the sensors bust or i need to up grade.
cheers. where shall i start checking the hoses theres millions to choose!!!! the boost doesnt fluctuate at all as i would expect with a leak. it stays at 4psi constant never more or less when you accelerate
 

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stevejoy5 said:
2.55 bar on the boost sensor, sorry but i dont understand i know a little on cars but are you saying the sensors bust or i need to up grade.
cheers. where shall i start checking the hoses theres millions to choose!!!! the boost doesnt fluctuate at all as i would expect with a leak. it stays at 4psi constant never more or less when you accelerate
Ok that was confusing additional info... the sensor on a TT which measure the boost for the engine management will only register up to 2.55bar so thats the maximum you can boost to - 1.5bar in 'real' boost since 1bar is atmospheric pressure.

As to your issue... there could be other reasons for hesitation:
coilpacks - the individual ignition coils for each sparkplug - can go faulty and give hestitation under load;
MAF - the Mass Air Flow sensor, tells the engine management how much air is being sucked in so it can calculate the fuel load needed... if thats giving an intermittent or low reading the fueling will go too rich and cause hesitation until the lamda sensors in the exhaust tell the management system to back off the fueling...

but, if your boost is only 4psi I'd say you're looking at a boost leak.. a split in a hose will remain closed until the pressure hits a certain level then will act as a valve so the boost wont increase above that level. The hoses are the big ones to the LH side and back of the engine (the chargepipe - takes pressurised air from the turbo to the LH intercooler), then there is a pipe from the LH to RH intercooler and from the throttle body (front of engine, right hand end of the intake manifold) to the RH intercooler

A picture: the red bits are the pipes mentioned above and/or where common leaks occur on the connections between the rubber hoses and the metal parts
 

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Discussion Starter · #5 ·
Ok ive been out for a good run this weekend and spoke to someone and apparently the boost pressure only goes to full boost in 4th 5th and 6th???? so i took it for a blast and it did go to 10 psi but i was in 4th at around 5500rpm by this stage, i thought it would be at full boost alot earlier? Also ive just been playing and i dont think my sirens working on the car how can i locate it and see if its workin? cos the roof was down today and thought id see what happened if i put my arm in the cockpit. the indicators flashed but no siren and also the interior sensor shut off button doesnt illuminate do you think its linked?
 

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Chip_iTT said:
A picture: the red bits are the pipes mentioned above and/or where common leaks occur on the connections between the rubber hoses and the metal parts
Hi Chip_iTT, sorry for the hi-jack, but you wouldn't happen to have a similar diagram showing possible boost leak locations for the 180 engine would ya? :)

Thanks in advance man!
 

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stevejoy5 said:
Ok ive been out for a good run this weekend and spoke to someone and apparently the boost pressure only goes to full boost in 4th 5th and 6th???? so i took it for a blast and it did go to 10 psi but i was in 4th at around 5500rpm by this stage, i thought it would be at full boost alot earlier? Also ive just been playing and i dont think my sirens working on the car how can i locate it and see if its workin? cos the roof was down today and thought id see what happened if i put my arm in the cockpit. the indicators flashed but no siren and also the interior sensor shut off button doesnt illuminate do you think its linked?
Steve,

Always a good idea to start a new thread for a new question, that way more people get to see it...

Alarm siren is s common issue... they do die, although you normal get 4 beeps from it on starting to indicate the internal batteries are going. Since you didnt mention this , I get the impression this is a relatively new car to you and you haven't heard the siren work at all before.

Siren is in the rear left bodyshell, accessed though the flap in the LH boot wall, although many find it easier to access it through the LH rear light cluster. Its a sealed unit and there's no way to test it, replacement is a £70 part and is an easy DIY job. If you feel clever you can replace the internal batteries... John-H did a great 'how to' at http://www.********.co.uk/ttforumbbs/vi ... 942#792942, but if its been dead for some time it may be too late
 

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lespaul_TT said:
Chip_iTT said:
A picture: the red bits are the pipes mentioned above and/or where common leaks occur on the connections between the rubber hoses and the metal parts
<Pic cut>

Hi Chip_iTT, sorry for the hi-jack, but you wouldn't happen to have a similar diagram showing possible boost leak locations for the 180 engine would ya? :)

Thanks in advance man!
I'll have a look tomorrow...
 

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hi
i was going to ask the same question my self being fairly new to the tt and no nothing so i will ask another question what do the numbers represent it would be good to know the names
thanks
graham
 

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3phase said:
hi
i was going to ask the same question my self being fairly new to the tt and no nothing so i will ask another question what do the numbers represent it would be good to know the names
thanks
graham
This is where you need to invest in a bentley repair manual... :) but have a look here for a 180 and here for a 225
 

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Chip_iTT said:
3phase said:
hi
i was going to ask the same question my self being fairly new to the tt and no nothing so i will ask another question what do the numbers represent it would be good to know the names
thanks
graham
This is where you need to invest in a bentley repair manual... :) but have a look here for a 180 and here for a 225
I've read somewhere that the Bentley manual leaves the APX engines out.
 
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