Hi,

After some help for a friend. We put his 55 plate STi Type UK on a Dyno Dynamics rolling road yesterday, it made 262.5 bhp with peak boost of 1.4 bar however the AFR's dropped off the scale below 10:1 as it reached peak boost.

The car is standard except for a dump valve, but it seems to be strangely rich. Even my focus RS only gets down to 10.2:1 and its well known that these run rich for cooling purposes.

If its normal then fair enough but just want to be sure before we start the power increases.

Cheers

Paul

 

subaru's are always set to run a tad rich from factory

 

Here's the stock fueling table for that year car, answers your question.

 

Thats really helpful thanks. It does look as though it is over fuelling but will check against the print out when my mate gets back from Afghan.

Cheers

Paul

 

The actual AFR may well not stack up against the desired AFR in the fuel map. It sounds quite normal really, but every car is different. 1.4bar doesn't sound very standard to me though.

 

The car has got an unknown exhaust from the cat back and a dump valve. It was this way when he bought it. When I drove it I thought it pulled well and I suppose that boost spike would make it feel that way.

I could check for a dawes device or fit a boost gauge to it to see if it pulls 1.4 bar on the road during normal driving. Hows the boost controlled on the Impreza does the ECU monitor it and adjust it accordingly?

Its supposed to be my dodgy ford thats a pain in the ****.

 

Do you have the AFR graph, there may well be nothing wrong with it. Without seeing that I can't comment, the fueling table is rich on boost and boost onset. In my limited experience so far, the cars I've looked at tend to be slightly richer than the values in the fuel table(stock).

The boost is a closed loop system controlled by the ECU.

 

The print outs are in his car but I cant get them until he gets back from Afghan in a few weeks. Once he is back I'll get him to scan them in and post them up.

Cheers for your help.

 

Yes.

The ECU, via info supplied by its many input sensors, controls the duty cycle of the BCS (boost control solenoid) - it's the brass coloured cylindrical thing bolted to the driver's wing (unlesss they look different on New Ages? ).