Marti

I have completed my first dyno run with the 928 and was a bit surprised that the power registered this low, it certainly feels quick on the road. As least there is still plenty to come but why this low? 330hp / 290 lb/ft at the crank

I am noticing that the power is not dropping off at peak revs like other dyno print outs that I have seen, not sure if this points to cam timing - only thing coming to mind

S4 89
Standard capacity
Colins cams
928 motorsport merged headers
X pipe
Re mapped with ST and fairly happy with the mapping,
standard inlet manifold has been modified

Mark Anderson

Did you do a baseline before you did the work?

Lizard928

How did you set the camshafts? Have you done a compression test to see what the readings are bank to bank (done hot).
Are there any faults on the ignition monitoring tab? Does it show any retardation per cylinder in that tab?

A baseline of before you start is always good.

Also I cannot remember what valve springs did you use?

Most auto S4s put down between 260-270 whp which is where you are currently.

Mongo

Stock???

Marti

It actually feels a lot better than the standard car but a lot of extra go came from playing with the ST and it certainly feels a lot quicker than before.

The car does have a standard exhaust system, could that be holding it back?

Marti

Does the shape of the power curve point to anything anyone has seen before, Greg, Colin et al

what I am pointing out is that often the curve plateaus by say 5.5 and starts to drop off by around 6.2k where as this is still climbing at 6.5

Marti

I also posting up a further run below, this was the previous run to the final run above.

The difference between the two runs is actually I shifted the flappy opening from 3.4k revs to something like 3.8k revs on the final run after I saw the below effects of the flappy at 3.4k which was putting a hole in the power curve

I plan further dyno runs with a completely stock inlet manifold as a comparison between modified stock and standard stock. I am wondering why power is just climbing and not plateaued off

terry gt

stock exhaust ? that's where your loosing power . 32 RW HP with headers and a duel 2 1/2 exhaust . at 350+ I was loosing power with the injectors wide open . now with proper injectors , there is even more power . 290 was my base RWHP . 91 GT

hacker-pschorr

His post says headers & X-pipe.

76FJ55

Not that I necessarily have any input on where there are gains to be made, but aren't most dyno runs accompanied by an AFR graph across the bottom?

Mongo

Random thought, could the diameter of the primaries on those headers be too small? I'm assuming a good set of headers for these cars use a 1 7/8" primary diameter, not 1 3/4".


Probably a question for both Marti and Colin, but for those cams, are you using stock injectors? Ideally, wouldn't a bigger injector benefit Colin's cams?

Marti

I should have mentioned that the injectors are 30lb so no issues regarding fuel supply. When ST on the road I managed to get the AFR all about target. I am actually pretty happy with the mapping.

I forget the exact size of the header pipes but they are a good size and proven to increase power over stock.

Mongo

I know there are cases where dynos can read power differently, sometimes understating. Typically it's calibration, but most (okay likely ALL) of the time these guys with dynamometers know what they're doing. Next thought is power rating - is it SAE???

In the end, the engine dyno is the most accurate, not a wheel dyno that attempts to calculate power loss through the drivetrain and back into the crank number.

Speedtoys

Ya, some solid ones even automatic in the mid 270s.

Speedtoys

If you have reached the end of the stock ones, yes. Otherwise it would make no difference.

AF chart with a dyno sheet is helpful in "How does this look" discussions.