Forge Dump Valve

[twign]

Hi,

I own a Mk4 Golf Gti Turbo.

I recently had a N75J valve fitted coupled with a remap that should have had it running approx 20psi boost producing 200bhp. However (just my luck) something's wrong, it's not holding boost, and according to my boost guage i'm only getting to about 14psi. As a direct result I guess, according to a RR I had down last week, it's only producing 170bhp.

Prior to the remap, I had a Baileys dump valve. When accelerating, I used to hear a hissing, and I also noticed that on half throttle the dump valve wasn't always closed. To 100% be sure my boost loss wasn't down to the dump valve, I coughed up for a Forge (yellow spring).

Now i've been doing some research, and i've read a few posts on this forum saying that the hissing sound indicates the dump valve spring is on the way out??? Would someone please confirm this for me? Because with the Forge fitted....I still hear a hissing, and so i'm still NOT 100% sure that i'm not loosing boost through the dump valve.

Also, I've read some threads about backwards fitting of these dump valves. Could this have anything to do with it? And why would anyone fit one backwards on purpose? Because does this not hinder the operation of the dump valve??

Any help would be greatly appreciated. I've spent £400 between the remap and the dump valve, and I've still not seen the increased performance that i'd expect...so i'm beginning to sulk! lol.

Many thanks

Twign

[raceboy]

If you haven't already I'd ask the same question here.......

http://uk-mkivs.net/forums/38.aspx

A lot more MkIV specialists to answer the question there.

[somouk]

It could be something like a split boost hose that you can hear hissing.

Boost problems are notoriously difficult to track down as you can normally only find them under load.

Don't knwo why you had a new N75 though, very rarely need to replace them!

Mart

[twign]

Hi,

Thanks for the info.

Well from what I can make out, the Golf GTi Turbo has the N75 from standard.

However, the guy who did my remap said that by fitting the N75J from the TT...the card would hold boost for about 2-3psi longer, therefore giving you a few extra BHP and a sort of 2nd 'boost' towards the end of your revs.

I don't know how much truth there is in that...but the car does feel quicker with the N75J fitted. Just nowhere near as quick as it should be. 170bhp is a bit quick....200bhp is quick! There's a noticeable difference between the 2...and it's just not living upto expectation as it stands.

Had it in at garage this weekend. He got no fault codes...and couldn't find a leak anywhere. Don't really know where to go next with it. Feel like selling the bloody thing in all honesty.

Many thanks

Twign