Exactly....

 

Steve,

After riding in your car I would say this reading is off. Take it to a rear wheel only dyno, most everyone agrees to a 15 percent loss on those. My guess is around 515 rwhp divided by .85 would get you 605 at the fly.

 

I looked around for a good article that discusses dyno testing, and found the following by Steve Dinan: Dynamometer Testing and the Modern BMW Engine

If here's the summary from the end:

 

Judging from that dyno the TT lost about 23% of its power to its wheels. I dunno what the correction factor for a AWD TT is but that aint too bad.

Do you have any dynos of a stock TT on a dynojet?

 

I saved this old one. . . think it was a mustang?

 

So, when are you guys going to start measuring your car's performance in the real world rather than racing with a dyno chart? (I know that some on this thread already have) This would eliminate all the variables you are arguing about. Is the reason you are trying for high HP numbers to go faster or just a "feel good" thing? The fact is, you can make your car's dyno results anything you want. Let's see if you can transfer it to the pavement.

 

I had my stage 4 GT2 dyno'd on the same machine. The first run showed around 430hp. I was disapointed. Then the owner of the shop came in and had 4 big industrial fans positioned. 1 for each intercooler, one on the front radiators, and one blowing down on the motor. The next 2 runs showed 518 hp at wheels! Its all in the setup.

 

Cool. So is it diffucult getting around town towing those four fans? I mean, based on your results, you need to artificially cool the intercoolers, radiators and engine compartment in order to claim those numbers..right?

I guess if you only drove on roads where there was a 200 mph+ cool breeze all the time, you wouldn't need the fans.

 

the purpose of the fans is to fake real world situations- when driving u get xxx amount of cooling- something you do not when when standing still.
just my opinion.

 

and the fans still won't come close to duplicating the flow you would get while the car was running on the road IMO

 

Why would he need to drive around town with them? The fans are used to simulate wind resistance on a car driving under normal conditions. They are also not creating 200mph winds. Have you ever been on a dyno? Sure as hell doesn't sound like it. The only reason I use a dyno is to tune my standalone without having to concentrate on driving. If you want a measure of your cars power, take it down the strip.

 

Using a dyno to compare apples to apples if fine and quite often is accurate inasmuch as it shows a "difference". But to claim XXX HP and that some how this will translate equally to the pavement...well, that's just not the way it works. I understand the use of the fans. (and it's NOT to simulate wind resistance). It keeps the coolant cooler, then intercoolers cooler and the the intake air cooler. This is what overstates the real power of the engine every time.

So you take your car out of the garage and drive around town for 30 minutes until the engine is fully warmed up. It's a beautiful sunny 75F out and there is a long, straight road in front of you with no cops and no cars. What is cooling your radiator, after coolers and intake temps when you are ready for takeoff? Would the temperature of these things be higher or lower now that you don't have fans blowing all over them?

Fact, on a sunny 75F day with the car moving less that 30 mph, your engine compartment temps are more than 40F above ambient temperature, making a nice warm throttlebody for your air to pass through. Is this higher or lower than the intake temperature when you are below 30 mph on the dyno with those carefully calibrated fans blowing on the engine with the trunk lid open?

Fact: Your coolant temperature is at least 15F cooler when driving 80 mph versus sitting stopped in 75F temperatures. Is your coolant temperature higher or lower than when you are sitting on the dyno idling your car with a fan blowing over the radiators?

Fact: Without air movement, your intercoolers quickly absorb the intake heat and climb quickly in temperature. This directly effects the temperature of the intake air. Is this higher or lower than the intake temperature when you are sittiing on the dyno with those carefully calibrated fans blowing on the coolers?


The point is, running fans at full speed on the above componants artificially increases your measure power output. If you could some how have the fan duplicate what the air movement would be at all speeds, then you might be closer to true REAL power.

So, I guess if your want the results you got on the dyno to transfer to the pavement, you'll have to continue towing the fans around and make sure you only drive on cloudy days.

 

You say some really stupid things!
Obviously you have not been to the dyno.

 

Hey Buddy? How come you never posted the ACTUAL performance figures for your car? Several months ago you promised us some numbers after your rebuild. I know that 6speed is more for the "bling" crowd, but I am sure you have timed specific speed ranges. Why not share them with us?

I have seen you post some numbers, but they ALWAYS have some excuse as to why they wern't better. You know the ones..."I missed 2nd gear", "one of my hoses fell off", :too much wheel spin", etc. How about some numbers without excuses? Or maybe your dyno results don't translate to the pavement?

And, yes, I have dynoed many cars over the years, including my liitle 3.4. 996. On that car, I have charts showing anything from 356RWHP all the way up to 434rwhp. I wonder which figure is correct?

 

I would also like to see some dyno numbers (not b/c I don't believe the numbers are fake but I am really interested in high hp cars). In addition, 6speed is far from a BlING forum, some of the highest HP numbers (for 996TTs) come from 6speed members.