Boost fluctuations

[kineticz]

Hey,
Sometimes I've noticed in the top three gears, boost hits 0.4bar max, and on the odd occasion it hits 0.6bar which is what I'd expect for a Cupra 1.8t 180.

What could cause this variation in boost performance? Why don't I see a consistent 0.6 bar?


Thanks all

 

[olliep]

i worked 0.6 bar to be about 8.702psi and 0.4 to be 5.80psi. if i'm right, both sound too low?!?!?! i thought 9.5 - 10 psi was the norm (0.65bar). It could be a boost leak, in that case i cant help. however what you described sounds alot like when my boost guage hose split. hopefully thats all it is. where is your guage hose running? mine was going over the turbo, constant heating and cooling not only changed it from clear, to brown, made a very very fine split. i now run it past the air box, to the right of the bonnet lifter and under the skuttle panel.

it was an intermittent issue at first as the pipe had to be the right temp to open up.

(assuming you are talking about a guage reading and not vag-com or something)

 

[kineticz]

I thought 7psi was standard mate?

From another site: 'Factory boost is around 7 psi I believe. Relatively mild boost which gives the stock 1.8t with its small K03 turbo excellent throttle response, and a nice flat torque curve which has earned it high praise in the automotive world.'

Or is that for the 150hp Golf GTI engine? :S

My gauge pipe is running down to underneath the glovebox, then up and across the windscreen, then into the gauge mounted on the A pillar.

HTH

Cheers

 

[olliep]

yeah i think ko3 = 150bhp(i.e. golf), 'ko3S' = 177bhp (i.e.- 180 LC)
ko3's' is slightly larger

mine is not mapped however i get 9.5-10psi prettymuch consistantly.

 

[olliep]

"and when the car is accelerating it can read a peak of anything between 8 and 12PSI, and it should hold around 6-9PSI."

i stand corrected, maybe theres more variation than i thought. the above is from pabs info base site on scn and he's a man that would know alot more than I!!

 

[kineticz]

Mine has the KO3 with 180hp as it's one of the earlier Cupras (when it was named the 'Sport').

Looks like I'm within that bracket then

BUT I have a decat and downpipe fitted, and I've been told I should get around 2psi increase??

 

[LEE69]

yeah i think ko3 = 150bhp(i.e. golf), 'ko3S' = 177bhp (i.e.- 180 LC)
ko3's' is slightly larger

mine is not mapped however i get 9.5-10psi prettymuch consistantly.

Same as mine.

 

[kineticz]

One thing I have thought about, is that the gauge when not in use doesn't sit on 0, it sits just below it. Is this normal or would it affect the accuracy of the reading?

Something isn't right

 

[LEE69]

Yeah if it is under it will read under, depends how much though it is under.

 

[olliep]

as above. to be fair, few aftermarket guages (or oem ones for that matter) will be accurate. sorry about the dodgy ko3/s info. i thought we had the same engine

 

[kineticz]

It's ok lol. Well I've got vagcom (albeit the freeware version) so is there a way I could access one of the blocks to measure boost pressure more accurately?

The vacuum measurements go down 0.1,0.2, 0.3 etc down to 1. The needle sits on 0.1 when on standby. Is it this figure I should add to get an accurate reading from the gauge, or is it simply the distance of the needle from the 0 mark that I should add?

Cuz if I add a mere 0.1 to my current 0.4bar, obviously that isn't a big increase. But if I add the actual distance, it would easily show 0.6/0.7 bar and I'd be alot happier with that.

Hope that makes sense hehe

It's weird because when I bought the gauge, the needle was dead on 0 but since using it, it sits below 0.

 

[olliep]

i would say 'no' to that last bit, as with most guages, th further up the scale the less accurate and so your could be adding completely the wrong figure. i.e. 3mm at the bottom of the guage might transpire to be equal to 6mm at the top. i cant reallly explain that very well at all. when engine is off is the needle on '0' i.e. right inbetween vac and boost? on the guage.

i cant help with vag-com at all but there is a vagcom section here somewhere

 

[olliep]

sorry about the 0 question... didnt see the last bit as i read it in hotmail... i'd see if anyones got a guage that you can borrow to try, or buy one at halfors and take it back afterwards or something. sounds from that like guage is naccked

 

[kineticz]

Ok mate well i'll see if I can check the pressure via vag com first and will post my findings here. I'm sure the MAP sensor reads the pressure so maybe I can access that

 

[kineticz]

Right not had a chance to scan it yet but one thing I have noticed, is on moderate driving if I put my foot down it will hold at the 0.5 bar, but say I've been thrashing it for a bit and put my foot down, it'll only show 0.4 until I let it cool down and go for a drive again.

Does this give any clues?

 

[kineticz]

Well chaps, who'd have guessed it, there was a hole in my boost gauge tubing lol

Gauge now showing 0.7 bar

 

[LEE69]

Nice easy fix!

 

[kineticz]

Nice easy fix!

Yup looks like I pierced it with a screwdriver when I was feeding it through the bulkhead

 

[Punch IT!]

So tell me does your boost peak at 0.7bar and stay there or does it peak higher and drop to 0.7 bar? Mine is a KO3s and its remapped. Mine peaks at about 1.3bar but then it sits at 1bar till over 4500revs then it starts to fall down to about 0.6bar? Is this normal anyone

 

[kineticz]

Sounds like a very harsh remap instead of a smooth one through the rev range.

Mine peaks at 0.7 then drops slightly to 0.6 and stays there past 4500