More Dyno Analysis

Having spoken to one of the guys who tested my car I have more information to add. It seems that analysing these plots is more complex than I had thought.

1) The Dyno

The performance figures were definitely measured at the wheels – they didn’t do a deceleration run.

Their rolling road is one of the newest and most sophisticated in the UK.

The single-roller design is more efficient that dual rollers. This reduces the amount of transmission loss.

The transmission loss is exponential with revs. At low revs the losses are small, so at 3000rpm there is only a few lbft difference between wheel and flywheel torque. This would agree with my peak torque being close to that achieved by Scaero (see Saabscene thread).

HLM have one of the largest cooling fans used in UK dynos. Combined with it being a cold day this should allow a high-power run.

2) Comparison

Comparison between results from different dynos on different days is difficult.

Power isn’t solely limited to boost – Air to Fuel ratio is an important factor and needs to be known for both.

The most powerful point for the engine isn’t necessarily when boost is higher, but when the turbo is working at its most efficient speeds.

Due to the cold ambient air temp and very big fan, the intake air temp may have been dense and cold, therefore allowing more advanced timing and high power with less boost.

Perhaps if the intake was warmer, greater boost would be needed for the power? I am not sure what my engine would do in the situation.

3) Where to go from here

One of the dyno testers felt they detected a misfire, however the other tester didn’t and I haven’t noticed it. The DI casette is 8 years and 110k miles old. The car is currently booked in with WMSS next week to take it for a test drive. I am now not sure if I should still go ahead with this or wait until March when I intend to have a service and other work done.

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