Dynamometer Results Help

[BRSMERC]

I’m really inexperienced with superchargers and engine performance testing in general and ask the following questions about the posted dynamometer results:

-The power and torque increase until the 6000 rpm point and then the speed drops off coincident with a torque and power spike. Can this be explained?
-The power and torque then again rise with speed increase. Can the significance of second speed rise be explained?
-Can a general explanation of the test be given?
-Is the fuel air ratio scheduled with a fixed program based upon sensed parameters – especially the knock sensor?
-Can a supercharged Marauder be cloaked as a grandpa car and show its killer instinct upon demand. What I’m asking – can it be driven as touring vehicle and then let loose once in a while? Right now it is a great cross-country machine and I would hate to ruin that feature?

I would really love to have the muscle car that I couldn’t afford in my youth. Boy, Ford certainly had me bracketed.

Brian

[looking97233]

The pic of the dyno run is first and second gears. The spike is when the car is shifting. Look closely at the bottom of the graph, it shows the rpm of the motor. Don't quote me, but I believe the eaton unit as set up here has a va***e controled by-pass. So when you are driving along steady at part throttle, the intake and output sides of the blower are open to each other, basicly free spinning. Then when you stomp on it, the drop in va***e causes the by-pass to close and thus pressurize the motor.

[mensrea]

I have a question about the dyno results listed on your web page, I assume the 400 number is at the crank? What factor did you use to reach the crank number, it looks like you took rear wheel horsepower (350) X power loss (15%) to equal 400. Is this correct?

What type of dyno did you use, and was it SAE corrected?

Owning a supercharged marauder, I am always on the look out for someone with MORE POWER!!!!

I love the idea of a Do It Yourself kit... maybe it will help sell more Marauders.

[BRSMERC]

Thanks looking97233, it makes sense when you look at the results. After the gear shift, the rpm dropped and then climbed.
An answer seems to lead to another question. Looking at the performance numbers (400 HP @ 5750 rpm and 420 ftlb @ 4250 rpm), it seems that maximum torque and power were picked during the shifting peak. Is this normally how this is done?

Brian

[BRSMERC]

I think Mensrea and myself have similar questions. The stated maximum torque and power don't seem to match the results other than the shifting peak.

Brian

[mensrea]

BRS, exactly...

[LincMercLover]

If they are claiming their numbers on a spike, then that IS NOT a true rating of what their gains are with his supercharger...

[Trilogy-Michal]

Let me straighten some concerns about dyno specs that were posted in Trilogy website.
Lidio who's doing calibration on MM had the car on MD dyno and achieved 358 RWHP @ 6100+ rev/min and 328RWTQ @4970 rev/min. MD dyno results were posted on website.

On Dynojet slightly better number were achieved:
387 RWHP and 350RWTQ. Estimated HP at flywheel is 430HP.

Lidio had MM on Dynojet today and the latest results will be posted soon.

If you'd like to find out more about MM dynotesting please look at Lidio's comment in this forum.

[TripleTransAm]

Originally posted by BRSMERC
it seems that maximum torque and power were picked during the shifting peak. Is this normally how this is done?


Nope. The spike is probably due to an instantaneous sharp increase in rate of acceleration during the gearshift. Think of it as the equivalent of barking the tires on an upshift. The car may not have the cojones to spin the tires at will at that speed by flooring it, but a full throttle upshift at that speed may bring about momentary wheelspin.

I can't tell you guys how many times I've seen this pop up in all the other message boards and email lists I've ever participated in. I really don't know why anyone would bother running a dyno in 1st or 2nd gears... the ratios are not 1:1 and therefore can skew the results due to increased losses in the lower gears. The biggest hassle in running an automatic in 3rd on a dyno is that you have to start the run at fairly high speed to avoid a downshift, but the results are more accurate.

That being said, in order to properly compare with other posted dyno results, it would have had to have been run in 3rd gear. It is my guess that such a run would have shown a peak hp of about 330-340 rear-wheel hp, based on the trends in the posted dyno curves at lower gears. Using a loss of 20% through the drivetrain (which seems to be in line with stock MM dyno curves I've seen), we can estimate a flywheel hp of 415 hp.

I'm fairly confident in this 415hp figure, as it jives perfectly with the 106 mph trap speeds that were posted elsewhere, for a MM with 1 person on board.

[BRSMERC]

This is great. Here is how I see the posted results. As the rpm comes up, the torque converter stalls and the engine is now quite coupled to the rear wheels and a large increase in torque is seen. Torque stays more or less constant but power increases more or less linearly because power is proportional to speed times torque. At the upper speed end, the transmission shifts. The energy stored in the engine at the upper speed when suddenly reduced by the shift is accounted for with a momentary peak in power and torque. Once into second gear, the torque/power relationships repeat until the limit rpm is reached.
Lidio has posted information on this in another part of the forum and indicated that he has just received the resources to repeat the test in third gear.
The new performance results on their Website now seem to make more sense.
I hope you all don't mind teaching and I'll try to be a good student. I have a Piper Arrow with a normally aspirated engine and have studied its performance. I could never afford supercharging in the aviation world, but I am willing to give it a try in the automotive world. Come summer when the Marauder is paid for, I'll take the plunge.

Brian

[TripleTransAm]

Originally posted by BRSMERC
As the rpm comes up, the torque converter stalls and the engine is now quite coupled to the rear wheels and a large increase in torque is seen
....
At the upper speed end, the transmission shifts. The energy stored in the engine at the upper speed when suddenly reduced by the shift is accounted for with a momentary peak in power and torque.


First, a side note: the converter 'stalls' when the output is zero, just like a plane stalls (no lift) at a given airspeed (input). Also, at full stall, the converter will multiply torque up to 2-3X depending on design, so the low RPM output may be incorrectly enhanced. In other words, it will look like the engine puts out much more torque at the stall point or slightly above. By the time the output speed of the converter is matching more or less the input speed, the multiplication will have dropped off to 1:1 (ie. no more torque multiplication once the rear wheels are underway 'enough'), this is the point you refer to quite correctly as 'coupled to the rear wheels'. That's why you can't trust a dyno plot for an automatic at points around and below the converter stall speed.

As for the power peak during the upshift, the dyno is measuring the rate of accelerating a drum via the rear wheels (usually). As you say, the stored kinetic energy in the motor will try to keep it moving at the same speed at the shift, but this would entail an instantaneous higher speed (because of the new ratio). But the rear wheels are also resisting changing their speed... the weakest link will break. In this case, it's much easier to slow the engine down than break the tires loose, but a combination of the two might result in a 'jolt foward' during the upshift, or in extreme cases, breaking traction momentarily. The dyno will see this as "holy cow, all of a sudden the speed of my drum jumped a good deal, but now it's back to accelerating at the previous stable rate".... <--- result: a synthetic 'peak' in your torque curve (and power is just a mathematical result of torque and RPM, anyway, so that is also affected).

A good example is riding your 10 speed bike, really pedaling like mad at a lower gear, then slapping the shifter(s) into the highest gear possible. CHUNK, your pedaling will instantaneously slow down. If you were REALLY strong, you might have overpowered the tire's grip and have spun the tire!

[TripleTransAm]

Originally posted by TripleTransAm
First, a side note: the converter 'stalls' when the output is zero, just like a plane stalls (no lift) at a given airspeed (input). Also, at full stall, the converter will multiply torque up to 2-3X depending on design, so the low RPM output may be incorrectly enhanced.


A good link:
http://www.victrans.com/multiplication.html

[Lidio]

Now that I was able to remove the 118mph speed limiter from the Trilogy MM, I took it back to a local Dyno jet again. I made two pulls in 2nd gear and two pulls in 3d gear. The numbers with the higher HP and TQ were achieved with the 10 psi pulley and the lower number were with the 8.5psi set up. As most will notice the 3d gear pull did come in a little lower in HP then in 2nd gear pull.
Also for some reason the dyno guy couldnt make the graph's show engine rpm only MPH. But I did pull it up to about 6200 on all pulls. And for some other reason the torque in second gear didnt show till a little bit into the run, no explination from any one at the dyno. Also note how the torque is up very quick in the run and in the mid range area.

Also the 2nd gear pulls made alomost the exact same HP as it did several weeks ago. This is after lots of drag strip abuse and plenty on the streets as well. I thought this was a good sign of repeatablilty and the engine holding up very well. I've posted with this message the new 3d gear pulls and have attached a link to both 2nd and 3d gear pulls on my web server.

http://www.alternativeauto.com/lidspix/MM2ndGear.jpg

http://www.alternativeauto.com/lidspix/MM3dGear.jpg


Thanks

[TripleTransAm]

Originally posted by Lidio
As most will notice the 3d gear pull did come in a little lower in HP then in 2nd gear pull.


But now we can compare apples to apples and MMs to MMs. ;)
To be honest, I totally forgot that the speed limiter can play havoc with getting dyno plots for 1:1 gear on some cars. :(

Nice numbers! I'm not familiar with the dyno software, but some seem to be able to output RPM, some only put out MPH. No big deal... the dyno operator has to enter in the proper conversion numbers in order to obtain the engine RPM, which is how it calculates the hp from the torque readings obtained from the spinning drum. And since we know hp = torque x RPM / 5252, that means hp and torque are equal at 5252 RPM exactly.

So when you look at the dyno plots, the point where the hp and torque curves cross will ALWAYS be 5252 RPM. From the curves, that looks to be about 114 mph, so for every mph increase on the posted curves, it's an RPM increase of 5252/114 or 46.07 rpm/mph, more or less due to the converter slippage, for
third gear only.

For example, you said you ran to 6200 RPM. On the chart, the plot goes all the way to about 137 mph... so 137 mph x 46.07 rpm/mph = 6311 RPM... pretty close, so we know we're on the right track.

At the low end, it looks like you punched it at 2900 RPM in 3rd gear. Did you have to modify the PCM programming to keep the MM from downshifting at that speed when you nailed it?

Judging by those curves, I'd say the motor's putting out about 450-460 hp at the crank with the high pressure. About 430-440 at the crank with the lower pressure setup.

As I said, nice numbers!