Dyno Test - low on power, what next..?

[Dom81]

Three runs tends to be more normal (from what I've seen at least) and each run is often marginally better

375 would probably have been acceptable (bearing in mind numerous debates over the years) but you are certainly low. Tyre age & pressure, Aircon left on, oil age, state of air filter etc. all have a bearing on results, but none enough to make a 10%+ difference - it sound's like an airbox flap or vacuum problem. On the dyno plot, is there a steady power increase or do you get a kick at 5.5k?

As well as needing 98RON or above, you get an MPG improvement which almost negates the price increase, so there's no benefit (and a big downside) from using lower octanes

[DazN]

on a regular basis I just use a regular fuel, either Shell or BP.

That could explain a loss of up to 50bhp.

This engine NEEDS at least 98RON to generate the specified power.

I didn't realise it made that much difference.

Me either to be honest, using V-Power the car feels a bit sharper but not a great deal faster or more powerful. It does say 95-98 inside the filler cap.

[DazN]

Three runs tends to be more normal (from what I've seen at least) and each run is often marginally better

375 would probably have been acceptable (bearing in mind numerous debates over the years) but you are certainly low. Tyre age & pressure, Aircon left on, oil age, state of air filter etc. all have a bearing on results, but none enough to make a 10%+ difference - it sound's like an airbox flap or vacuum problem. On the dyno plot, is there a steady power increase or do you get a kick at 5.5k?

As well as needing 98RON or above, you get an MPG improvement which almost negates the price increase, so there's no benefit (and a big downside) from using lower octanes

Tyres were all new under 2,000 miles ago, I also put them all to 40PSI the day before the run and checked them again while cold in the morning before I left.

Aircon was on (I think), as for the oil, air filter etc I'm not sure, oil was changed around 3,000 miles ago, air filter no idea.

He did mention the airbox flap and vacuum could be a problem.

I do get a kick at 5,500rpm.

Dyno attached, page one is power at the wheels, page 2 is at the crank.

[wrekka]

Did unit 20 stay with you whilst the car was at dyno demon? As dyno demon are Subaru Tuners and probably wouldn't know about the RS4 set-up.

[DazN]

Did unit 20 stay with you whilst the car was at dyno demon? As dyno demon are Subaru Tuners and probably wouldn't know about the RS4 set-up.

Yes he did, but Grizz from Unit 20 didn't 'drive' the car while it was on the rollers, one of the Dyno Demon guys did.

I would have preferred Grizz behind the wheel and 3-4 runs really, suppose I should have said something at the time but I've never done a dyno before.

[Dom81]

Looking at the plot, you are getting a kick at the right place, and making good power to that point. It's what happens next, where I would expect somewhere north of 380 based on the line so far, but instead it essentially flatlines. From memory MacRS and Klauster had the same issue at one of the Paramount days - both got fixed, but I can't remember how...

In terms of fuel, I'm no expert but believe the engine adapts over time rather than immediately, so a sudden change of RON might have little or no effect

Suggest you take you name and registration number off the plots, as there's scum about who use info like this...

[DazN]

Name and address removed to protect the guilty!

[PetrolDave]

It does say 95-98 inside the filler cap.

In the hardback manual it says:

We recommend the use of SuperPlus unleaded, 98 RON. In emergencies, use Normal unleaded, minimum 91 RON. Performance and consumption values were calculated using SuperPlus unleaded (98 RON).

So 98 is what should normally be used and is essential when doing a dyno run, 95 can be used in emergencies and will give reduced power, and 91 can be used in "life & death" situations.

[P_G]

A few things to consider and some not mentioned. Daz-RS4, what was used to provide airflow, one fan or a couple / more? And was this in a closed space?

RS4 engines are extremely sensitive to airflow and heat soak, IIRC when we were at Paramount Pippyrips RS made about 10bhp when cooled down than what it did going straight on the dyno after a long drive to Paramount. That and their airflow in and exhaust gas extraction was not the best which affects performance. Also it is on Shoot_44, which is a program tuned for guess what, Subaru's. 44 is descriptive for 4cyl 4WD, essentially turbo charged cars so the figures it records and how it extrapolates them is tuned to a turbocharged car, not a V8. Shoot_8 is no better as it is for GM LSV8 engines and RWD. On Dyno Dynamics roads my RS makes anything between 345 and 370 bhp yet on a Dastek road which learns your cars power delivery prior to recording power delivery gets anywhere from 396 bhp upwards so don't be disheartened.

Running on 98/99 RON fuel will make a difference, also try some Wynns DIP3 Petrol Treatment. But wait and see what Grizz says. It may just need a proper Italian tune!

[davey]

Did unit 20 stay with you whilst the car was at dyno demon? As dyno demon are Subaru Tuners and probably wouldn't know about the RS4 set-up.

They know what they are doing, they have rolling roaded loads of RS's.

[wrekka]

Did unit 20 stay with you whilst the car was at dyno demon? As dyno demon are Subaru Tuners and probably wouldn't know about the RS4 set-up.

They know what they are doing, they have rolling roaded loads of RS's.

Even so, one run is rather unusual? Usually the average of a few runs is taken. The first run to check everything is running correctly etc...

[lengster1]

Sorry but i suspect you have an issue,that graph isnt even the right shape,they dip in the power curve in the midrange and climb steadily after 5500 and thats almost flat,fuel doesnt make anything like 50 bhp difference 10-15 is much more like it.a run in 3rd will not be a full power run on a stock RS4 it needs to be in 4th,either way your car is way too flat in the upper revrange and that carbon build up im afraid,it has the most effect at high flow situation ie high rpm,i have the relevent graphs from mine at various states of tune,de coke will give you top end power back but little difference before 5k to be honest,further tuning porting exhaust cats and re maps will up the power overall by a good chunk,i cant upload my graphs as this site is a pita and overseas also but they have been posted before i believe if you search

[P_G]

Carbon build up? Really? Best to discount the basics first like vacuum pressure, air box flap working, proper petrol, airflow on the dyno etc etc before jumping to that conclusion.

[lengster1]

Basics checked thanks,its got a kick at 5k which strongly suggests it has good vacuam pressure to open the airbox flap! Correct? If poor fuel makes 80-90bhp then i do apologize

[lengster1]

Daz rs4,does it always kick in the higher gears? Or have you had it feel flat like in the earlier gears and no extra induction roar so to speak? The airbox flap has been known to be ill fitting and need a fettle (neckarsulms i think) if it does intermitently kick which you havent said it does.Go on mrc website and look at the power plots and compare yours you will see what i mean.