legacy motor goes flat around 5000rpm???

[phippzie]

Hey everyone i have a 1990 legacy GT and when im out for a spirited drive boost comes on well and stays there and it accelerates like you would expect it to but as soon as I reach 5000 rpm the motor just feels like it goes flat, almost like its just runs out of puff. Boost gauge still tells me i have a good boost level (14psi) and that doesnt change. Friend of mine said thats just how they are ??? but i dont know so any advice would be great.

[kamineko]

need someone familiar with them to check it out

but ummmmm random guess #1 is the intercooler system working all good? faulty pump? they have a sensor for low coolant eh

[lachlan]

do the fuel filter pronto . and the fuel pump next time you have a spare $150

have you owned or worked on many turbo cars ?

[kamineko]

 lachlan said:

do the fuel filter pronto . and the fuel pump next time you have a spare $150

have you owned or worked on many turbo cars ?

thats a better guess

[titian]

Knock sensor ;) http://www.clubsub.org.nz/forum/index.php/topic,33060.0.html

[phippzie]

This is my first turbo and only had about a month so just trying to sort everything quick. So guys you reckon fuel filter and pump and check the intercooler?

[phippzie]

Sorry titian just saw your knock sensor post. How would I go about doing that? Is it easy enough for DIY or should I get a shop to do it?

[titian]

very easy...takes 20 min. 8)..new one costs around $100 from winger. bound to be a thread here on how too...just not sure where Can do! Box o speights! Just you have to drive to Auck

[phippzie]

Haha that\'d be great but Christchurch is a bit far. Ill do a bit of research and see what I come up with

[titian]

here ya go http://www.clubsub.org.nz/forum/index.php/topic,33590.msg449446.html#msg449446

[phippzie]

Thank you so much man. That\'s awesome! Ill get into it soon as I finish work ;D

[titian]

that suggestion of fuel filter is also a good one.. :)...but usually there is a miss associated with it.

Remember to disconnect ya battery to allow ECU to reset when you change sensor. Leave off for an hour or so.

[phippzie]

Alright so fuel filter knock sensor. Leave the battery off for a while. Think I got everything

[lachlan]

its not something silly like the muffler has collapsed on itself or the air filter is in a similar state ?

can anyone comment on how a stock vf8/10 feels past 5 k anyway ? potentially its starting to sign off eg past its efficiency

but it could be a case of old un loved everything knocking it back 10% and

has it got a flat spot/miss at 5 k but makes good power after that or doesn it just not make much power after 5 k ?

[phippzie]

This is the only one ive driven so don\'t know how others are. It\'s all factory and just replaced air filter and all that. It makes good power up to 5000 but after that just stops pulling

[Marky]

May its not even broken? You might just be getting used to the power delivery, if you\'re not used to a Turbo car they do feel like they fall over up top (and some genuinely just do) I haven\'t driven a stock rs in years but they aren\'t exactly hi revving screamers out of the box

[phippzie]

Yea I was also told the same thing by a friend of mine but it just didn\'t seem right

[BC5RA]

Is it a manual or auto?

[phippzie]

It is a manual. 197ks

[BC5RA]

You\'ll have to be more descriptive in regards to the power drop off. Without driving it; it hard to diagnose.

Assuming it still runs a VF10 or VF8.

It should pull cleanly to 6000rpm at which point you\'ll feel like your flogging it.

At 5000rpm onwards does it just feel asthmatic or is it a much more pronounced drop off? As if it becomes Normally aspirated?

[mattapo]

The last twin turbo that felt flat when the secondary kicked in ended up being the exhaust callapsed.

[BC5RA]

 Trends Car Audio & Alarms - Mattapo said:

The last twin turbo that felt flat when the secondary kicked in ended up being the exhaust callapsed.

It\'s not a gen 2.

[mattapo]

My mistake

[phippzie]

 BC5RA said:

You\'ll have to be more descriptive in regards to the power drop off. Without driving it; it hard to diagnose.

Assuming it still runs a VF10 or VF8.

It should pull cleanly to 6000rpm at which point you\'ll feel like your flogging it.

At 5000rpm onwards does it just feel asthmatic or is it a much more pronounced drop off? As if it becomes Normally aspirated?

I wouldnt know what the turbo is but its still stock if that helps. It feels ashmatic at 5000 like its run out of puff. I havent driven an NA one so i couldnt comment on how they perform in comparision to this. It could just be simply how they are like ive been told. Im planning to modify the exhaust and intake soon anyway so that could help it.

[phippzie]

so progess is now bad. replaced the fuel filter easy anough and went to start on the knock sensor but have discovered a couple perished and split lines in the intake system so now i need to replace them and i still didnt get to replace the sensor! fml