coryf

A Dynojet can do a "coast down" test. After the peak rpm of the run is reached you put the car in neutral and let it coast back down while it is still recording. When you have let it coast down to a desired drum speed you hit the stop button on the wand to end the recording of the run. On the graph you display "negative hp" which will show what the drive train hp loss is. Its probably not a 100% calculation of drive train loss but gives a very good idea.

powdrhound

I go through about 5 gallons in a 30 min session. I usually start 3/4 full and refuel each time. If I start full then I could do 2 sessions but I don't like to track the car with much less than 1/2 tank.

powdrhound

It seems that 10-12% number is fairly accurate. If you look at the Hp figure on my car and the '15 Z06, both dynoed virtually identical at 590 and 589 with the advantage of cooler OAT going to Chevy. Add 10% to that and you get 649. I would imagine the 650 published figure from Chevy is a certified no BS number and probably a minimum figure for the average production engine meaning that the true average figure is probable 650 or slightly better. 10-12% seems very plausible..

z06801

#'s for the 2015 Z06 seem very consistent with what others have done on them.

jumper5836

sounds like with your setup your burning normal fuel rate.

I have stock k16's so I would see quite a bit of improvement switching to a similar setup as what you have. I was contemplating getting a new Z06 during its second year run once we find out if there are issue's with it and if it will over heat under track conditions.
Sounds like I could save a lot of money just doing some turbo replacements, tune, diverter valves, injecters and intercoolers and get the same hp in my current ride and yet still be well under the weight of the Z06.

powdrhound

The Z06 is not light. It's over 300lbs heavier than my car and I doubt it will be nearly as bulletproof as our cars...

993GT

solid baseline, looking forward to build pics and review
7GT2 gearing will be nice!

Slalom996T

coryf:

Finding the "true" crankshaft torque with a road/wheel dyno

The "coasting method" may be done with a lot of, if not most, different brands of the road/wheel dynometers.

But it is significantly different in order to try to factually measure the trans tax since most areas with friction taxes the torque flow vs a crank dyno in a proper dyno cell.

First of all the might the tax situation not be the same in coasting mode (i.e. only friction torque load) vs the entire transmission being exposed to the full load of engine torque?

Some of the friction areas on the taxing side:

Wheel: Tire temp and pressure steady? Shore value and width of drive tires? Wheels in //?

Bearings: Shape new-old and settings? Viscosity of grease/oil? Temperature of the grease/oil?

Gearbox/diff: Overall shape new-old-blueprinted? Straight cut/spiral cut gears? Viscosity of oils? Steady oil temp? Case flex above a certain torque load resulting in somewhat distorted angles?

If/when testing in acceleration/decelleration mode: Inertia values of the entire transmission as well as the above variables in a steady stable state?

Etc.

Obviously may "the coasting method" be used in evaluations if the above is taken into acconut i.e. constants.

Btw: Seldom will the typical road/wheel dynomometer have a better resolution and repeatbility values below 5% even if being calibrated between each round.

(Oem engineering typically use crank dynocells with resolutions & repeatability valuse below 0.1%.)

Slalom996T

cbracerx

Thanks for posting your experience, the package you are using seems to be an excellent setup for street (91 octane tune) and track (massive controllable torque).

z06801

Hey what's the difference between 2A and 2B fuel and tune? All I know is I can't have it till I have rods

powdrhound

I think typically the 2A kit includes turbos, 5bar fpr, and a tune.

I don't believe it's set in stone but I think the 2b kit generally includes Kevin's zero clearance turbos, injectors, intake mods, and his tune. My car already had the RUF intake manifold and turbo inlet pipes which are very similar to the UMW variety. I think an exhaust is also needed for 2B. You don't need rods if Kevin detunes the output of the turbos down low like he did in my case.

z06801

I have the same GT2hybrid ZC turbos, had to carefully break them in before Kevin would send the 1.2 tuning 5bar fpr, at the same time I did his clutch kit and 70mm Miltek exhaust. I just knew I couldn't get more tuning without additional hardware.

powdrhound

The 1000 mile break-in is painful especially if you don't street drive the car much.

z06801

Like a 8 year waiting for Christmas haha

powdrhound

Engine was removed yesterday and it is currently fully disassembled. No real problems with the engine. IMS thrust bearing showed some wear. Crank thrust bearings also showed some wear due to the clutch interlock (the interlock has recently been removed which allows you to start the car with clutch released just like on all the ROW cars). Rod bearing showed a little distress but nothing major. Valve guides showed some wear. Pistons and liners were like new...