Where are you picking up the RPM signal?

 

This was done about 3 months ago on a Mustang dyno. We were dynoing just to tune, and not for bragging numbers. My highest run was done with the car cooled off, at 9psi, in 3rd gear. The final tune was for 12.5psi, but the car was fairly hot by then, so the numbers were lower. My mods at the time were greddy turbo, boost controller, rp supercat, and rb exhaust.

 

If anyone has, or if future runs can gain the BSFC (brake specific fuel consummtion) numbers for a dyno run, I believe it would be invaluable information.

I know the rotary supporters in aviation would deeply appreciate the data. There is much debate about real fuel use in the rotary, and little fact. It's seems generally agreed that the rotary is somewhat ineffecient in lower rpm, and that Mazda way richened the fuel curves is some places to control cat temps, but there is just no data to go with it.

BSFC numbers @ 75% peak HP and peak HP would be great.

Additionally, there is an arguement floating around that essentially says the increased "p" of an FI motor decreases it's BSFC, thus making a FI motor more effecient. Nice theory, but this too requires BSFC data to prove.

Finally, there is some evidence that "lean of peak" use at cruise has a major impact (reduction) on fuel consumption. If a 25% reduction of highway MPG was available to you, would enough interest be in play (if data was had to support it. again we need BSFC..) to entire fuel management maps to have an "economy" mode? LOP for highway droning, best power A/F for "performance". I suppose LOP might do in a cat...



Any help is appreciated.

Thanks.

dan

 

I have seen BSFC figures published in a historical book on RE development, but I can't recall them, except to say I believe they were "favourable".

Cheers,
Hymee.

 

This dyno was done just behind Silvereight's last run. The only change to my car since the previous dyno posted is the warranty work for hard starts and flooding issues which means new battery, starter and spark plugs. I gained about 5hp off of the new plugs. This graph does not compare between this run and the last run shown on the dyno graph posted but it does show a one of the runs made on the same day as my previous dyno graph posted.

 

Here's my Dyno.

Bone stock '05. On '05 equivalent R flash. Note: I'ts FLYWHEEL HP and torque is in Nm. This is a European Dyno.

 

Oh dear. That will stir up the proverbial hornets' nest. Performed on a Chassis Dyno I assume?

Cheers,
Hymee.

 

Yessir!!

It was a 4WD-able dyno. The guy told me the rollers could apply brake force and that they used them to calculate powertrain loss (Don't ask me to explain it )

As a matter of fact, Wheel HP is not comon in Europe. Dyno figures are flywheel all the time.

Interesting FACT: I reset the ECU and totally disconnected the DSC, mysteriously the (ABS) light came on. The guy at the dyno told me all RX8s do that, it's because the front wheels aren't turning.... ECU pulling timing back at the dyno anyone

Hope I stirred the hornet's nest a little...

 

yeah, its normal for the ABS light to come on, until the car is driven for a short bit. What does that Nm translate to in HP, my convert program wont do that conversion?

 

That is because you can't. Nm is measure of TORQUE, and HP is a measure of POWER.

And just as I suspected, the FW power was not actually measured. You can only measure flywheel power on an engine dyno. What the operator has done is to measure the power at the wheels (a true measurement), then "calculate" (estimate) what it is at the flywheel based on some assumptions relating to drive train losses.

Cheers,
Hymee.

 

that is what i thought, Nm is torque, oh well. Stupid americans we are.

 

What the guy told me is different. He does not calculate any type of loss. The Dyno does.

After the pull, the guy pressed the clutch pedal and let the wheels and the rollers deccelerate. With that, the machine gets the frictional losses in the drivetrain, according to the decceleration ratio detected.

I assume the machine knows the weight of the rollers and their decceleration ratio from a given RPM ratio. I f you include the transmission of the 8 turning at the same speed an get it deccelerates at the same rate than the rollers alone= zero frictional loss and so on. It must calculate a tranny loss ratio that applies to the wheel curve.

That's what they said

 

...and I must, add, for what I know, a lot of european dynos are like this one.

 

Here's what the engineer at the Dyno shop e-mailed me:


The Dyno measures WHP with its sensors during acceleration. That curve is registered.

Right before engine cutoff, the clutch is depressed and the car is allowed to deccelerate to the exact speed the acceleration process started with.

Decceleration is measured like acceleration, with sensors. This decceleration is tranny loss, wheels...

The more it deccelerates the bigger the losses will be. That's measured very accurately, just like acceleration.

Both losses and WHP are added to get engine power.

Later on a correction factor is applied in order to comply with ISO or CEE standards. It has to do with temp and barometric pressure, not the actual dyno run.

 

I'm not bashing you, just the mis-information you have been fed by the dyno operator. I know it is common practice for that technique to be employed, especially in Europe. The theory behind calcuating drivetrain losses based on inertia decelleration is flawed IMHO.

http://www.pumaracing.co.uk/coastdwn.htm

Cheers,
Hymee.

 

Hymee,

Despite the tech info you can provide, I deeply respect your opinion. I don't personally know you, but you seem to be a reputed professional.

You may probably have a point but, since all dynos around here tend to do the same thing, we tend to take them right and base our comparisons on the obtained data.

Cheers,

Miguel

 

Miguel,

No worries mate. I'm sure all the dyno operators will dispute my opinions, and the "findings" reported by Puma race engines.

This is how I like to think of it: The power measured at the wheels is real, and that is what the car is making where it counts - at the tyres. If you want to know what the flywheel horsepower really is, use an engine dyno. Thankfully, I have access to both, and I'm getting ready for some engine dyno time real soon

Cheers,
Hymee.

 

PLEASE do post them

I'd really like to see what a stock renesis can do, as well as a twin screw supercharged one

 

Jusy my 2 cents:
If the systems being incorporated in Europe weren't close to accurate it would eventually be evident in the disparities of actual engine dyno figures and calculated dyno figures.

 

.49 to .50 lb/hphr would be expected from a fuel injected peripheral ported rotary with the injectors properly located and properly timed in the upper rpm ranges. This is clearly not as good as the best of piston racing engines but not bad either.
Playing with the right components our folks were able to reduce exhaust temps from 1950 deg F to 1600 at wide open throttle and you can breathe deeply close to the exhaust without passing out or getting teary eyed for what that's worth.
I would imagine a 0 overlap rotary (Renesis) could have much better numbers than these with tuning.
I hope that helps a little.

 

I've been observing european flywheel dyno numbers for more than 15 years. Estimated engine power output according to those dynos has never been erratic and, therefore, put into question by anyone.

A a matter of fact dynos have always managed to come up with ballpark figures. Let me give examples:

Nissan 350 Z (300 HP): 292 Hp
Honda s2000 (2.0 Liter model): 230 Hp
Mazda Rx8: 217 Hp

The only thing they really emphasize on is using 1:1 gears for the pull.

My pull was in fifth gear.

 

So isn't 217 about 20HP on the low side? Or am I missing the point.

Cheers,
Hymee.

 

What I am trying to underline is the accuracy of the measuring method.

The Rx-8 in Spain is supposed to have 231 Hp. I managed to get 218, the mag I'm quoting 217 and another one I have read managed to get almost 226 Hp, all of them below the advertised Flywheel HP. The renesis also seems to be down on power in Wheel Hp, so both measurements seem to be consistent with each other.

No dyno in Spain has ever gotten more than 226 Hp from the Renesis. Although, the 350Z seems to be pretty close and the S2000 unit they tested was off by 10 Hp. Even the 280 Hp 350Z got 276 HP.

STis and EVOS have managed to actually make the advertised HP if not improve it a little. (Test mules with a little more boost anyone )

The FD was advertised as a 241 Hp car back in 1993. The dyno got 243.

N/A cars sometimes fall a little short of the advertised HP, once in a blue moon some do a little better, while some of them just put out what they claim.

The biggest rip off is Turbodiesel test mules. The manufacturers ruthlessly boost them up so most of the time they usually are up by 20 HP.

Turbocharged gasoline cars manage to stay on track.

I am really looking forward to see what the renesis does in your engine Dyno

Cheers,

Miguel

 

The RX-8 was tested using the old SAE standard- which allowed the removal of all the accessory pulleys from the engine during the 'at the crank' test. Many manufacturers did this on many vehicles. The new SAE standard removed these loopholes. Look at the RX-8's output under the new SAE rules.

 

Here's my latest set of dyno's.

The one dated April 3, 2006 was done after I had my coils replaced and I installed a set of Racing Beat plug wires. You can see some improvement on this chart from my previous one of where I had plugs replaced.

The other two dyno's are from April 17, 2006. These are dyno's taken after I installed the Agency Power underdrive crank pulley. One of these dyno charts is what they are using for their marketing (with my permission) incase you noticed a similarity from the one on their webpage. Definately see and feel some power down low. Minor peak power gains but the torque is definately improved. The pulley got me into the 190hp range. I may get some more hp after I install an exhaust since I am still running stock.