MB

If it was plugs, it would have to be a complete misfire on one cylinder to lose that much power. Filter would have to have a hedgehog stuck in it

Like I say, I wouldn't go spending money on a problem until you've done some basics. Unless they need doing anyway...

As long as the AFR was right, and it's not pulling *massive* timing (ask Romain to look at your AEM - but i'm sure he will have) I think it could be mechanical or setup as AJ says.

MB

Quite common on MAF based cars, can happen on MAP based cars too but less likely as the sensor isn't in the air path like a MAF.

If the MAP is screwed you should be able to see the load voltage doing funny things on the AEM, but it would also show on the AFR reading...

Suits

Yes, good call on the basics, thats the plan anyway.

The AFR was good (12/12.5) and Ro did take a look at the AEM with nothing being obvious.

Im thinking it could be to do with the brakes........

martin j

Tyre pressures? Same straws different suggestion.

Suits

Tyres were at 30PSI, not different enough to warrent such a loss though.

s2konroids

Probably a red herring, but an AFR of this value is far too low an N/A S, should be running in the low 13's, 13.1 seems a sweet spot. Generally most N/A cars should be run in the range of 12.7 to 13.2AFR, the S is no exception.

MB

Yep it's on the rich / safe side, but not sure if the AFR has always been the same between the runs where it's reportedly lost power?

Suits

It may well have been a touch higher to be honest, at the time I wasn't paying that much attention to it.

I just gave it a quick glance to make sure it wasn't anything critical.

This is current AFR, (It's the lighter blue plot), like you say, it's nearer 13.

Suits

It should have stayed the same, yes, it's not been adjusted between the runs .

richmc

I remember reading somewhere they up the tyre pressure to run a dyno, can't remember why or to what pressure, I know nothing about dynos, this just stuck in my head.