My car seems to have developed a tendancy to sort of surge "on and off" from around the 6000rpm, as if the ignition is constantly advancing and retarding near the limit. Its quite subtle but its definitely there.
In all other respects it seems fine and boost is OK as far as I can tell. I am seeing 1.2 bar peak dropping to a little over a bar and on WOT in gear accelleration, the boost slaps straight up to 1.2 bar. I do get the feeling that the car has lost a bit of pull up at the limit but that could be in my mind and I wonder if I have only just noticed this and am now dwelling on it (pardon the ignition timing pun...).

Does anyone have any ideas? The car is an STi4 with only Scoobysport DP and BB and panel filter mods and I run it on SUL with OB (converted back from Optimax with O/B about 5 tanks ago)

Neil.

 

BTT (and I can't believe there is no-one with any ideas on this....)

Neil.

 

I'd be fitting an uprated fuel pump if I were you. You may be running weak at the top end ? Unlikely to be the timing IMHO.

 

Andy

Is it possible that the OE fuel pump has lost some performance? The car is coming up to 50,000 miles now.

Neil.

 

In my experience the standard pumps are marginal when new !
If you are holding over 1 bar at full rpm then you may be pushing your luck with it 50k down the line.

You could check it out with a pressure gauge or a lamda sensor.

Mark at Lateral Performance does a reasonably priced drop in replacement that's good for at least 1.8 bar.

Andy

 

Will you put that in writing Andy? I seriously doubt it, unless you've done extensive work elsewhere....Oh, you have

Richard

 

Andy.

Do you have any contact fetails for Lateral Performance?

 

mark@lateralperformance.co.uk - the pump is definitely a good idea.

Richard

 

Thanks guys.

Neil.

 

LOL @ Dowser *Disclaimer* - The pump alone will not permit you to run at 1.8 bar !!!

 

Thanks Andy; I think I'd got that already though...

 

And the fix was........sparkplugs!

I took the old ones out (NGK PFR6Bs)and replaced them with NGK PFR7Bs. The old plugs had a gap of about .85mm; the advised setting is .70mm.
The car now pulls strong and smooth right to the redline in all 5 gears!! (well OK in 3 of them....).
I hadn't realised how the performance had dropped off over a period of time through the plug gap widening so the cure brought a pleasant "new" turn of speed.
Moral is check your plug gap more.

Thanks to Mark at Lateral performance for pointing me in the right direction and not screwing me for a fuel pump that I didn't need; now that's quality service.

Neil.

 

Didn't take you long to get to the bottom of it then Did you check your fueling ok at full rpm ?

 

Unfortunately I don't have an AFR or EGT meter or any difinitive way of checking other than by "feel" and all felt fine to be honest.
I'm not saying that the fuel pump is perfect, just that there doesn't seem to be a problem now?
I'm also guessing that as the engine now sounds and feels smoother there is probably no det or leaning out, but having said all that I'm still open to advice if you have some.

Neil.

 

It is never any harm to put a knocklink on a Subaru, especially an import.

One problem is not always alone - an STi 5 I looked at had boost creep AND a faulty fuel pump together. The combination was deadly, car was already on its second engine.

 

You are quite right John, and a knock detector and AFR meter are things I keep promising myself but never get around to....
How much do they cost these days; any recommendations?

Neil.

 

Speak to BRdevelopments. There are fancy looking new models coming out also.