boosting funny

[nick s]

hi guys, got a problem with my cupra. it's fine for accelerating now and again, but sometimes when i accelrate from 1st gear, flat out through all the gears, i lose all boost in 3rd and 4th temporarily, then it comes back and you can really notice it, just randomly stops boosting completely around 4-5000rpm sometimes for a second or two then comes back?! i fitted a forge FMIC and full blueflame system on sunday, and it is still doing it as i thought it might be heatsoak. i5 doesn't do it all the time though. just sometimes when i've been giving it some for about 5 - 10 minutes at night on quiet roads.

i'm getting my k03s and re-map all done in a couple of weeks and obviously i'm worried it might do it with that. any ideas guys? thanks.

 

[PhilW]

What DV are you running?

 

[nick s]

Forge 007DV

 

[pdcupra]

checked all your hoses for leaks?

 

[claudefrog]

any split hoses?

 

[Damo]

If it's none of the above (check these 1st), then it could be your N75 valve.

 

[PhilW]

I'd check the DV first to make sure its not sticking.

 

[pdcupra]

if its an intermittent problem its probably more likely to be something like what phil suggested..

 

[Forbez]

What TIP are you running? Because IIRC the standard ones can collapse under load, causing a similar issue.

 

[Damo]

Dogy N75 valve can be imtermitttent as well. Runs fine 1 minute, goes haywire the next.

Agreed tho, check DV first.

 

[nick s]

ok, how do i check if the DV is sticking?! i have only had it on there for about 2 weeks it's brand new.

also, i have the standard TIP at the moment, but i have a samco one, ready to go on when the K03s is put on.

my mate has removed his N75 valve i think. he said that stops the DV cutting boost or something?

 

[Damo]

Remove DV. With a pen, push the piston up from the bottom. Cover the top nipple with your finger. If it shuts it's faulty, if it holds open, it's ok. Check the 'o' rings on the inside as well to make sure they're in place.

Doubt your mate removed the N75 valve. More like the N249 valve.

 

[Forbez]

Its in here, how to test it mate:
http://www.forgemotorsport.co.uk/valve_service.pdf

 

[PhilW]

^^^^ Thats worth doing to check if its leaking.

See if the piston inside slides up and down nicely with grease inside.

 

[nick s]

thanks for that guys. i will have a check. as i say it's very intermittent and only happens very occasionally!

N249 valve. that was it. what does it actually do when you remove that?

 

[Damo]

N249 valve. that was it. what does it actually do when you remove that?

In true technical terms I'm not sure , but before mine was removed my car used to go into limp mode under full load at low rpm's quite frequently (this was after the K03S conversion), now it's removed, limp mode no longer happens. Searching will no doubt reveal what it's all about as it's been covered quite alot in the past.