Variable boost

[Firefly]

Hope somebody can give me some clues....I\'ve got a completely stock \'94 3rd gen and my first 1000 miles were perfect.  Over the last 1000 I\'ve been losing some power, mostly over 6,000 rpm, but 2nd boost is just generally a bit variable.

Strange thing is, it is fine in 1st and 2nd gears (although going to the line in 2nd has once or twice got me quite a lot of wirl and hiss, that lasted a minute or so after boost).  First it was losing power between 6,000 and the red line in 3rd.  Got to 6,000 perfectly, then just faded, every extra rev taking that much extra time, \'till it finally got there.  More recently the 2nd boost seems to be just generally sluggish - sometimes it spikes around 6,000 revs then goes again, which other people have experienced.

Sometimes it is perfect and leaps up to the line in every gear!    

Anybody got any ideas.....

[iaint]

Sounds like the either a dead hose (leak in the vacuum system or collapsing intercooler pipe or a dodgy solenoid.  Get it along to someone who knows the setup and it should be simple enough to sort out.

Iain

[Firefly]

Cheers for that - I was hoping that the 1st thought would be for a simple solution, seems a common problem.  Should be able to get it looked at in the next couple of weeks.  If I have no joy, I\'ll be back asking for other ideas!!
I\'m getting a new stainless back box on Saturday - don\'t expect that to make any odds - but somebody shout if a free-flowing substitute for the standard box has any dangers.  has a single-splitting to twin final pipe instead of two little pipes, but should be a similar flow.

The thought of constant high performance is great!!  Fingers crossed.

[Firefly]

Just remembered that I never posted the solution! Common problem this variable boost, in my case was caused by pressure build up in the exhaust - had a staight downpipe put in place of the front cat to fix it (W.G.T.).

Now the boost works great all of the time.  

Every now and again it screams at high revs (which it had done  before) - hope I am not going to have problems with the centre cat breaking up now!

[Andyp]

how much was ya downpipe dude? who makes it too do ya know?

[eatmyrx7dust]

Whilst fiddling with pipes and referiing to internet.....

Check.
Top of \'Y\' pipe (where the two outputs from the twins join and then feed to the top of the intercooler. Very Common.
Also check 1" pipe which feed the input side of the BOV. If you can turn it, its too loose... replace spring clips with jubilees.
HKS make a hard pipe replacement for the top and bottom of the intercooler and mazda made a metal \'Efini\'  Y pipe replacement with a flange instead of jubilee connector.

You will find that  \'94\' third gen pipework will have degraded substantially.

I\'ve replaced all mine !!!!

I\'ll go and take some piccies and post them.

Adrian

[eatmyrx7dust]

I know the intercooler looks a bit tatty.....but look a the shiny bits !!

[eatmyrx7dust]

A full engine bay spread.

[Firefly]

Nice pics Adrian - Useful to refer to when the fear of pipes comes.  Fingers crossed It\'ll be a while.  Perhaps the pipes fairy will fix mine while I\'m down the pub.

As for downpipe prices - no idea who made my pipe - it is a wide bore pipe that came part used for, from memory about £70, but there was a good deal of labour time on top.

Not much technical knowledge there I\'m afraid!
Paul