ashutt

This morning my cousin and I dynoed our cars using a Dynapack 5000 load bearing dyno machine. It hooks to the hubs of the rear weels. It doesn't use a roller system like the dynoJet. I have no knowledge of either system but the shop indicates that a load bearing dyno is more accurate than a system like the dynoJet. The temp was about 52 degrees, Bar. was 25.26 and is the altitude is around 4500 ft.

2005 997 Porsche Carrera S
My cousin went first. He has a 2005 997 Porsche Carrera S (stock it is rated at 355 HP & 295 TQ). He has a six speed manual. After his best run, he was putting about 278 to 280 to the wheels. That would be about 333 hp at the crank (using a 20% calculation for drive train loss). That means on this dyno with the high altitude and other factors, he was about 22 hp under the Porsche claims (however, there are numerous east coast dynos showing this car at 355 actual sea level testing). All of his pulls (5) were consistent within 5 HP.

2001 CLK55 AMG
I went second. I have a 2001 CLK55 AMG with a SpeedTunningUSA chip upgrade. It is configured for 93-94 octane. Let me just start by saying that the shop had a much harder time configuring my car to run correctly on the dyno since it is an automatic and the ESP can't be fully shut-off.

Even after I turned off the ESP using the switch inside the car, it still cut in and wouldn't let the car perform correctly on this load bearing dyno (hooked directly to rear wheel hubs). So we pulled fuse 24 and 37 (for ESP) in the engine bay on the drivers side- which triggered the ESP, BAS and ABS warnings. However, this allowed the car to rev up smoother to redline of 6,400. Please note that according to the user manual on page 216, that with these three malfunction indicators "only partial engine output will be available." I am not sure this was the case for me but it is possible I experienced some power loss- I wouldn't think so but I didn't see the timing map either.

Regardless, we went forward with the dyno runs. We manually shifted using 3rd and 4th gear to reach the highest dyno numbers. The best pull came on run 3 which was 303 Hp SAE to the wheels at around 5,2000 RPM. The shop indicated that this would be about 364.3 to the crank (using a calculation of 20% for drive train loss). My other runs varied from about 290 to the 303 to the wheels but admittedly it was hard for them to get consistent linear graphs because of the downshifting of the car under load. They were not happy with this issue, so they didn't charge me.

The shop thought the car was very strong and a 302 in that area was pretty good. The air/fuel ratio was about 13.0 (which I believe is on the leaner side). They also thought it would pull higher numbers if we could figure out how to not allow the car to downshift under load. If anyone knows how to avoid this, please let me know so I can have it retested.

So, it appears that the car has at least a 22 hp gain [342 hp stock to crank vs 364 now] with the addition of the Green Filters and the SpeedTuningUSA chip and possibly more if we can get the car to function properly on the dyno.

I see that Chappy has stock 304 to the wheels at a lower altitude- that is great! I wonder what a chip upgrade would test for you at sea level?

deyainrdy4ds

nicee thanks for the update on the results...

btw tho...wen i had the BAS ESP warnin comin up for sum reason that i dont even kno...it did feel like i had less power but im not totally sure...

CLKCLK

Thanks for the update.

Anyway the chip does work. That is all what I want to find out so all the mistery about the car will record the ship behavior to the original is cleared. I am looking forward to modding mine too.

Thanks!

Josh K

FYI a load bearing dyno isn't more accurate than a dynojet (probably why dynojets are the industry standard)

Also, you can't really base a hp increase off of an estimated crank number vs. a manufacturer's estimated hp.

why?

Not all cars make the advertised power. Some make more, some make less. The variation can be as great as.............20hp.

Not trying to be negative and I sincerely hope you're enjoying your new toy, but for future reference, the only way to know if your car made any gains is to get it dyno'd before and after each modification at the same facility (preferably with a/f monitoring as well so you can make sure that's good)

ashutt

Here is what I have been able to discover, the dynapack is closer in design to an engine dyno and it gives more flexability in how you can use it. The dynojet is pretty simple in comparison. If you want to see what the big companies use look up Rototest- which are expensive- they start at about $80,000. The dynojet ($30,000) is cheap compared to the dynapack ($90,000). Rototest and Dynapack operate on the same theory.

Just because more shops have DynoJet doesn't mean it is more accurate. I would assume more shops could purchase a $30,000 dyno machine than a $90,000 one. This could influence the amount in the market. There are certainly more Toyotas and Hondas in my state than Mercedes but I would be hard pressed to assume that makes them a better car.

DynoJets read whp and use engine rpm to calculate torque. The Dynojet really has no way of simulating vehicle load at speed. This is because, once you get the rollers rolling, it takes virtually little HP from the car to keep it there. I understand a shop can purchase an eddy pack for the dynojet which will permit you to load up the wheel while running the car on the dyno, thus simulating what it would be like to try and keep a car moving on the road, but the reason you hardly even see the eddy pack on a dynojet is because it costs $15,000.

Basically, track racers in our area use the Dynopack because it allows you to tune better. I actually devoted more time to this research on the Internet and I believe you will find that the DynoPack is more expesive (consequently less common) for a reason. This is the same reason I bought my CLK55.

Here is a good link: http://member.rivernet.com.au/btaylo...Equipment.html

I have not used a DynoJet so I don't claim it is a less accurate product, but I have my suspicion after researching the technology further. In any case, it really is no big deal either way. I am sure I will dyno on a DynoJet in the future for fun.

Josh K

I think you're a bit confused with regard to horsepower and how a dynapack works.

Dynojets do not read horsepower. Horsepower has nothing to do with keeping the rollers rolling, and hp/torque are not independent measurements - horsepower is a mathematical function of power in relation to time.

Horsepower=(TorquexRPM)/5252

Torque is rotational force - what a dynojet (and a dynapack) measures. The RPM the torque is being achieved at is also easily measured via the vehicle's spark plug wires or VSS. The rest is math.

The dynapack functions in a similar way, it simply doesn't use an inertia roller. The dynapack does not simulate vehicle load at speed. The packs place a load on the hubs and the car's torque is calculated based on how it overcomes that load - basically a roller without the roller/inertia. A simulation of true road conditions would have to include many things: rotational mass (wheel/tire/brake combos) as well as the car's mass, and things that no dyno can replicate such as wind resistance and the drag coefficient of the car.

Sure the dynapack has benefits: they allow you to test torque/hp at part throttle and it's a little easier to test repeatedly through specific RPM ranges (without having to look at a full run graph). They also get rid of the roller so they're quieter, shops that don't have the space for an above ground dynojet (or cant get the permits to sink a roller) can have an option, and they're great for testing 4WD cars. Many track racers drive 4wd cars and/or tune with the assistance of datalogging software that tracks fuel curves over many throttle percentages/rpm and for this, yes the dynapack is more convenient, but for the testing that you were having done, you were not getting a more accurate result than you would have with a dynojet.