Author Topic: mk2 GTD boost question (Read 3325 times)

protobob · « **on:** January 14, 2009, 01:00:30 pm »

Hi all

my first post

I have a 90 GTD uk spec mk2 golf (sb code)

when i got the car it was very under powered but VERY cheap and i found the issue to be the wastegate not seating properly like this the car was making max .3 bar boost about 4.5 psi after i fixed this the car will now make .9 bar around 13 psi which is a vast improvment but under hard acceleration it backs off to .5 bar (7 ish psi) and you can feel the car pull back tonight i have screwed in the popoff valve (to make it stiffer) and i will see if that makes any diffrence

as far a i can tell the car is standard

on my brothers 91 GTD this does not happen also it doesn't happen on a GTD jetta we have as a spare

if its not the popoff valve comming in too early would i be right in thinking it would be the fueling. although this seems to happen at any revs over 3K no matter if you change up to lower the revs ( i try not to change up too late ie anything over 4750 ish as the car has now done 211000 miles :!: )

sorry for the long post any ideas are welcome

smutts · « **Reply #1 on:** January 14, 2009, 01:47:03 pm »

Congratulations on joining the club, :wink: .
The normal boost on the SB motor is about 10psi, the pop valve ( black plastic thing on the intake hose) pops at anything above this, 13psi will do this and puke out the pressure till it seats again at about 5-7 ish psi. What you describe is classic for a jammed shut wastegate too.
Good luck in bunging up the pop valve.

205000 miles and chasing at 750 miles a week!

Baixo · « **Reply #2 on:** January 14, 2009, 01:49:15 pm »

stock boost on my stock gtd is 9psi......

MouseGTD · « **Reply #3 on:** January 14, 2009, 01:53:13 pm »

i'm having a boost issue like your first problem, guess i should check my waste gate. any tips on what to look for and how to solve it?

smutts · « **Reply #4 on:** January 14, 2009, 02:03:22 pm »

I only had this happen to me with one of the cars laid up for six months. Wet weather. Think deluge as default setting. The hill not too far from me is on the Ordinance Survey map as "Mount Arrarat" can't think why.
Wastegate presumeably rusted tight. So when driving this happened.
Foot down, surge of extra power for a second or so, muffled "poot!" flat as a fart for a second, then power picks up, surge of extra power for a second & repeat cycle till you get carsick or the wastegate unjams. :twisted:

protobob · « **Reply #5 on:** January 14, 2009, 02:44:38 pm »

the wastegate lever had moved slightly out to the edge of the turbo and the wastegate valve itself was fouling on the casting of the turbo i did try heating the leaver and gently tapping it back in but in the end i got rid of the casting with a dremel type thing it is much better and is seating properly also the actuator (sp) is working although i couldn;t test the pressure at which it opens it does with a gentle blow from the airline :wink:

its just blody annoying when you goto overtake someone and the bloody thing backs off the boost as i said i will check tomorrow with the popoff valve tightened and will let you know if that doesn't work i check the wastegate by blocking it off (while i had the turbo off i replaced the short rubber tube with a longer loop of rubber line for later adding a boost controler

) and i will see what that does

protobob · « **Reply #6 on:** January 15, 2009, 02:02:31 am »

It was the popoff valve

she now boosts to 1.1bar so about 16 psi :lol:

pulls really well very happy

thanks for all your advice

Baxter · « **Reply #7 on:** January 15, 2009, 04:35:59 am »

I find that a piece of 8mm steel tube cut to 20mm in length is perfect for replacing the sping in the blow off valve (I prefer calling it a Blow Off Valve as I just love inuendo!)
:lol:

Author Topic: mk2 GTD boost question (Read 3325 times)

Baixo

Baxter