Disappointing Dyno

[ashleyg]

I attended a ford rsoc dyno day in the old RS4 last weekend and was quite surprised with the result.
After being asked for a prediction, I pitched what I thought was a lowball of 380hp; it was carbon cleaned around 4K ago, has a panel air filter, milltek sort cats and non res system. However it hasn't been mapped.
I'm quite happy with how it drives and seems to pull well.
It posted a mere 349hp.
I got it home and found there to be a vacuum hose leaking quite badly at the power flap valve at the airbox. I've removed this and blanked it. The car feels much better but I'm not sure it's all the way there. Is there anything else I should be looking at?

The sports cats have been on for around 18 moths without a problem but twice in the last month I've had a MIL light and codes for warm up cat efficiency low on both banks 1 and 2 twice and codes for secondary air injection flow low, banks one and two once.

Looking at the dyno print out the torque starts to tail off at 3700rpm and takes a steady decline as the revs build.
The dyno op, whilst not a specialist also wasn't an idiot and suggested a problem with the variable cam timing, is that possible?
I would like to think that there wasn't enough vacuum to hold the flaps fully open, restricting the inlet and reducing the VE is the revs increased.

Any thoughts on where to go from here would be appreciated

[FaisalJ]

If you're anywhere near MRC Tuning (even if you're not) I'd consider getting over for a £82 health check on the dyno.

Vacuum issues can cost you a lot of power.

Get a stage 2 map while you're there

[bam_bam]

Re: Disappointing Dyno

Welcome to B7 ownership.

[R1RS4]

Why not stick it back on the dyno as you have found a serious vac leak, they say it as much as 30/50 BHP that puts you about right

[MikeFish]

Yep, all of the above.

[ashleyg]

I was planning to have it dyno'd again, just wanted to see if there was anything else to check beforehand.
I have always planned to take it to MRC but thought they were on the south coast. A quick Google has shown them only to be a hundred miles away.
I need to make the decision about what inlet manifold I want before I have it mapped though.

[PaulT]

If you found vacuum leak in the hoses connected to the air box power flap actuator or relay then very likely this would also impact the operation of the inlet manifold flaps as there would be insufficient vacuum in the system.

Lack of operation of the manifolds flaps and power flap will have big impact removing all the kick at 5500rpm. It will just feel flat at higher revs.

The power flap is the end of the vac line, plugging the leak there should have fixed the inlet manifold flap operation which will have improved situation a lot. But power flap will remain inoperative (closed all the time), it should open at high revs to provide more air. You can test by taping power flap into open position and going for a run - remove air box top and filter, then apply some tape to power flap to hold it open in the inlet, reassemble and try it out. NOTE: as power flap draws warm air from behind aux rad, this is ok at higher speeds but is detrimental at low speeds due increasing inlet temp, so not recommended to fix it open permanently.

You can test power and manifold flaps operation using VCDS, it is very easy - there is procedure referenced in FAQ thread at top of B7 forum.

[ashleyg]

Ooooops; I removed the power flap from the airbox completely when I found the leaky pipe.
I had a look at the procedure for testing the tumble flaps after sorting the leak and they seem to have a full range of movement. I've ordered a hand vacuum pump and plan to see if the system will hold vacuum, working through it progressively if it doesn't.
I was a little concerned about what he said about the variable cam timing, is it an issue with these?

[PaulT]

My (limited) understanding is variable cam timing issues are rare - i was worried on this a few months ago as i got a couple of cam timing faults logged and all the timing gear is very inaccessible on rear of engine. However i had vac leaks and faults appeared to be secondary.

Do you have VCDS? (If you dont recommend you should get it - very useful) You would be able to read fault codes and see if there were any setpoint not met faults for the cam timing.

[ashleyg]

Yes I have full VCDS. Only codes I have had were for secondary air injection and warm up cat efficiency.
I see that there's an inlet for sale in the classified section. Is it worth going for a stage 1/2 manifold before I get it mapped?