Visited a rolling road yesterday with my 2003 sti ppp. Achieved 246bhp gutted! The stated that my car was running dangerously lean. Not just lean but dangerously! Firstly what could be causing this? Secondly how will I know if I've fixed the issue?
I've also noticed I've got 2 cats fitted?

 

Can you post the graphs? If its leaning out at high revs it could be the fuel pump not being up to the job.

If lean across the range it could be the map, dodgy MAF or a leak in the intake/exhaust somewhere.

Graphs will be a start, but I'd recommend a specialist asap and not so much on boost driving.

I recently had a similar story, 284bhp on a dyno and lean readings. Ended up being fine, just a poorly executed dyno run. Got 320bhp and healthy afr at another dyno.

 

 

It does look a bit all over the place that graph...but is that not the same place another guy had issues with recently?

 

As above try different dyno and compare them

But I would check if there are leaks and MAF at least


Jura

 

How do I go about that?

 

Yes Gaz we went to the same place yesterday.

Im going to Surrey RR to meet Simon JGM where he will do some checks and hopefully tell me it wont cost much to fix . Going on the 2nd Oct Wednesday.

Did ask Pete if he wanted to join as I wasnt satisfied with Austecs customer service and rr but had no reply.

 

Fuel pump or leak in pipes to inlet pipe or inlet pipe split

 

Cheers for the advice guys.

 

Checked the maf today and it was fine. Where would the leaks be coming from. Is it a case of not enough fuel or to much air?
The car drives and pulls well.

 

How did you check the maf? Unplugging it is a myth btw.

Could be either

 

Oh lol that's what I tried.

 

Its unfortunately a mute test.

You need to look for splits in the inlet pipe where it meets the turbo, that the breather pipes are all on and intact.

However seeing as the ppp on the 03 sti involved fitment of a walbro fuel pump and they seem to have a useful life of around 5years, I would assume its the likely issue.

Had to replace a pump on an 02 sti today as noticed as soon as started mapping that it was fubar

Simon

 

Surely if the fuel pump was knackered it wouldn't drive well?

 

Looking at that power graph it doesnt!

It will only fail to keep up on boost and high rpm

 

Ahhh ok. I'm sorry if I'm being a mong but I'm not very experienced with all this. I'll only learn if I as these questions.

 

no issue.

basically in normal driving a lot of the fuel that is pumped by the fuel pump to the engine is passed back to the fuel tank when the fuel pressure reg reaches the desired pressure.
So on idle and criuse a lot of fuel just flows back, on boost the fuel pressure increases as the fuel pressure has a diaphram in it which is altered by air pressure so less returns to the fuel tank and the injectors inject more fuel obviously.. if a pump gets weak then it will drive fine off boost, only on boost the fuel pressure will decrease or stay the same rather than increase and the engine run lean.

Obviously sometimes fuel pumps just fail completely and the engine won't start.

Simon

 

Yep that makes sense. Is the pump fairly easy to change? Bleeding the system etc

 

Yes, took me 30minutes today taking my time but I have changed a fair few.

Brief guide in the help pages on my website - www.jollygreenmonster.co.uk

Simon

 

Thanks a lot simon can you recommend a fuel pump?
Does the system need bleeding afterwards?
Really appreciate the help cheers

 

No self bleeds.

Walbro, rcm, etc

 

Only 5 years, really?

Is that specific to the PPP upgrade ones, or just Walbro in general?

 

http://bit.ly/1b7zNrK
This one?

 

yes

 

general

 

Best think about changing the one in my car, it's been in coming up on 8 years.

Cheers for the info, Simon.

 

if your not pushing much above standard power its probably okay.. but worth a check

 

I had a fuel pressure gauge and a wide band afr gauge fitted to my car. Two gauges often overlooked but they saved my engine when my fuel pump was playing silly buggers.
I could actually watch the fuel pressure drop off as the car approached max boost. Without them I'd of not known there was a serious issue.

 

Was that in reply to me, Simon?

Mines only about 100 BHP over standard, that's not much.