Analyse my Dyno charts, help find my problem

[gtrbubba]

...
The problem was the volumetric efficiency increased because of a less restrictive exhaust and also some intake mods, this means that for the same PSI the turbos had to deliver a much higher volume of air to keep the same boost level througout the rev range...

On the surface, this comment makes no sense (and can be misleading for those who read it at face value), if you kept the boost at the same levels as before the intake/exhaust mods the mass of air moving through the system will be identical at any given RPM, unless you somehow had a dramatic change in intake charge temperature.

I have a feeling that what you're really trying to say is the mods allowed the turbo(s) to maintain the previous (otherwise OK) boost level much longer through the rev range than the system was normally capable of, and that pushed the intercooler beyond it's heat rejection capabilities.

Talking about "volume" and turbos is a little ambiguous, as what it's all about is mass of air moved per unit of time. The "volume" of the engine never changes! (higher RPM; more air molecules moved through the system per second).


Just an observation...

[frankiman]

here, i just traced (hurray for power point) the AFR, Boost, Power and Torque all on the same graph

AFR and Boost are using the left Y axis
Power and Torque the right Y axis

[Skym]

Can see around 5250rpm where A/F ratio slightly dips and boost level increases. 12.0:1 A/F ratio seems to be the sweet spot with that engine. Although I would run it richer for longevity of ceramic turbo's. With 400hp at all 4 wheels, stock turbo's probably would be running out of puff.

Another thing to take into account is intake temp compensation, as stock GTR ECU has the capability to adjust to high intake temps. Stock GTR ECU has IAT (Intake Air Temp) sensor.

[frankiman]

turbos are N1s by the way

and the tune was done on only 2 the rear wheels

with the loss of a propulsion type system (15%), peak power is 408/0.85=480

[gtrbubba]

turbos are N1s by the way

and the tune was done on only 2 the rear wheels

with the loss of a propulsion type system (15%), peak power is 408/0.85=480

Good graph; notice your bump in boost around 5200 and a correspondingly lower torque? Something weird is going on there! The timing is being backed way off (detonation or something). A subtle change in mixture probably wouldn't make that much of a difference.

There must be a confluence of events going on there, the ECU is upping the boost, yet apparently retarding the timing! Weird...


Also, be very careful when using "magical" loss ratios like 15% when attempting to get a flywheel horsepower. Load-based (torque) gearface losses are trivial when compared to other losses (like tires, fluid, and bearing friction).

For example, if you were to remove your turbos, the overall frictional losses on the dyno would stay nearly identical, yet according to your calculations, the resulting losses, from a roughly 120HP NA engine, would be 18HP!

You simply cannot say that it's a 15% loss for RWD. The losses are not proportional to power.

A simple coast-down on the dyno will give you a pretty good idea of what your actual losses are, and it's completely irrelevant how fast the dyno roller got up to speed to measure the coast-down losses.


Before someone pipes in about inertial losses, that's why dyno pulls are done in 4th gear usually, as that allows the dyno run to last long enough that inertial drivetrain losses are a tiny fraction of the total, and not relevant, unless you have 750+ HP!


What fun...


Addendum: Taking it at face value, your calculated drivetrain losses of 72HP equals 53,690 Watts. Do you have any idea how much heat that would be? (frictional losses are mostly heat, and a bit of sound)

Take 540 (yes, five hundred and fourty) 125W incandescent light bulbs, put them in a small space and turn them on! Are your transmission and tires generating that much heat?? No, I thought not...

FYI, a typical car has 60MPH road losses of around 20HP, most of which is aerodynamic.

[RBdreamer]

Don't know if this was mentioned or not, but how are the EGT's ?

[frankiman]

no idea, didn't monitor that