Supermodel Dyno
#17
USMarine
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Originally Posted by FlyingDog
I think every sate has at least 1 muff diver. In VA I've seen MUPHDVR, MUFFDVR, MUFDIVR, and MUFDVR.
#18
Sharkaholic
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Originally Posted by bigs
OK. Stupid question time from a SC newbie here.
One of you guys help me out here. Why do the HP and TQ curves both start out 1,000 rpms later in the SC run than they did in the NA run?
One of you guys help me out here. Why do the HP and TQ curves both start out 1,000 rpms later in the SC run than they did in the NA run?
Bigs has nothing to due with the S/C, it is just a matter of when the dyno operator hits the data record button.
#19
Racer
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Let me see if I can answer a few questions.
The HP and TRQ lines don't intercept because the before and after HP are in the top frame and the before and after TRQ are in the bottom frame. We were starting the runs at 2500 RPM but with the SC we started at 3500 RPM. This was the first day I have driven the car since the install, so I guess we didn't miss any bolts.
Car setup. Stock engine with 151K, never rebuilt. Otte X Pipe(made by Tom Cloutier), in place of cats. RMBP. Kenne Bell Twin Screw with Intercooler. 66mm pulley making about 7lbs boost. Lots of race upgrades, but you don't care about that. Always been a strong car.
The HP and TRQ lines don't intercept because the before and after HP are in the top frame and the before and after TRQ are in the bottom frame. We were starting the runs at 2500 RPM but with the SC we started at 3500 RPM. This was the first day I have driven the car since the install, so I guess we didn't miss any bolts.
Car setup. Stock engine with 151K, never rebuilt. Otte X Pipe(made by Tom Cloutier), in place of cats. RMBP. Kenne Bell Twin Screw with Intercooler. 66mm pulley making about 7lbs boost. Lots of race upgrades, but you don't care about that. Always been a strong car.
#21
Three Wheelin'
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Those are very nice numbers, but something is not right.
The first thought which must cross anyone who's 'in the know' must be, why are these numbers so much higher than the other twin-screw dyno sheets? For those who study various dyno sheets of similar hardware configuration, one learns what the trends look like; likewise, since one learns the trends, it becomes rather easy to spot the outliers, and this dyno is one of those cases.
So why did the dyno report such an outrageously high number with respect to the other 928 twin-screws?
Take one look at the 'Red' SAE correction factor: 1.16
..whereas the 'Blue' SAE correction factor is 1.01, a much more reasonable number.
Just for kicks, let's 'un-correct' the 'Red' peak horsepower number, and then use the 'Blue' SAE correction of 1.01 to see what the rwhp would hypothetically be.
First we'll find the 'non-corrected' rwhp number:
Non-Corrected rwhp = rwhp / (SAE correction factor)
Non-Corrected rwhp = (471.74 rwhp) / (1.16) = 406.67 rwhp
Now let's find the 'corrected' rwhp using the 'Blue' correction of 1.01:
Corrected rwhp = (Non-Corrected rwhp) x (SAE correction factor)
Corrected rwhp = (406.67 rwhp) x (1.01) = 410.74 rwhp
The 'hypothetical' 411 rwhp is a much more reasonable number given the trend set by previous 928 twin-screw dyno runs.
So what happened? Why did the 'Red' dyno get a *HUGE* 1.16 SAE correction factor?
Look at Red's barometric pressure: 26.10 in-Hg. You may say, 'What's the big deal?' The 'big deal' is, the lowest barometric pressure EVER RECORDED in the Western Hemisphere was 26.84, and that was during Hurrican Camille in 1969! Go here and see for yourself:
http://www.geocities.com/hurricanene/gulfcoast.htm
So unless the car was dyno'd during a hurricane more powerful than the most powerful hurricane all-time, Hurrican Camille in 1969, it is IMPOSSIBLE for the car to be dyno'd with a barometric pressure of 26.10, and that barometric pressure was used to come up with the correction factor of 1.16.
The punch-line is, that dyno run for whatever reason has an invalid SAE 'Correction Factor'. The good news is, the dyno sheet itself provided us with enough clues to solve the 'mystery'. If it were me, I would go talk to the dyno operator/owner and see what's up with their equipment.
Interestingly enough, here's a recent post discussing whether dynos provide reliable results:
https://rennlist.com/forums/928-forum/214013-aftermarket-cam-grinds-for-4-valve-motors.html
The first thought which must cross anyone who's 'in the know' must be, why are these numbers so much higher than the other twin-screw dyno sheets? For those who study various dyno sheets of similar hardware configuration, one learns what the trends look like; likewise, since one learns the trends, it becomes rather easy to spot the outliers, and this dyno is one of those cases.
So why did the dyno report such an outrageously high number with respect to the other 928 twin-screws?
Take one look at the 'Red' SAE correction factor: 1.16
..whereas the 'Blue' SAE correction factor is 1.01, a much more reasonable number.
Just for kicks, let's 'un-correct' the 'Red' peak horsepower number, and then use the 'Blue' SAE correction of 1.01 to see what the rwhp would hypothetically be.
First we'll find the 'non-corrected' rwhp number:
Non-Corrected rwhp = rwhp / (SAE correction factor)
Non-Corrected rwhp = (471.74 rwhp) / (1.16) = 406.67 rwhp
Now let's find the 'corrected' rwhp using the 'Blue' correction of 1.01:
Corrected rwhp = (Non-Corrected rwhp) x (SAE correction factor)
Corrected rwhp = (406.67 rwhp) x (1.01) = 410.74 rwhp
The 'hypothetical' 411 rwhp is a much more reasonable number given the trend set by previous 928 twin-screw dyno runs.
So what happened? Why did the 'Red' dyno get a *HUGE* 1.16 SAE correction factor?
Look at Red's barometric pressure: 26.10 in-Hg. You may say, 'What's the big deal?' The 'big deal' is, the lowest barometric pressure EVER RECORDED in the Western Hemisphere was 26.84, and that was during Hurrican Camille in 1969! Go here and see for yourself:
http://www.geocities.com/hurricanene/gulfcoast.htm
So unless the car was dyno'd during a hurricane more powerful than the most powerful hurricane all-time, Hurrican Camille in 1969, it is IMPOSSIBLE for the car to be dyno'd with a barometric pressure of 26.10, and that barometric pressure was used to come up with the correction factor of 1.16.
The punch-line is, that dyno run for whatever reason has an invalid SAE 'Correction Factor'. The good news is, the dyno sheet itself provided us with enough clues to solve the 'mystery'. If it were me, I would go talk to the dyno operator/owner and see what's up with their equipment.
Interestingly enough, here's a recent post discussing whether dynos provide reliable results:
https://rennlist.com/forums/928-forum/214013-aftermarket-cam-grinds-for-4-valve-motors.html
Last edited by Lagavulin; 07-09-2005 at 03:30 PM. Reason: A crappy sentence.
#22
Racer
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Can't answer why the settings are different. I will stop by the dyno next week and ask. Andy Keel was working with me at the dyno (more like I was looking over his shoulder), and I am going to his local dyno next week. We will see if the number jive.
#24
Three Wheelin'
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Originally Posted by Shane
Just so happens that there is a Hurricane in the works and He does live in Alabama. Could still be off some but maybe not.
http://www.weather.com/weather/local...om=search_city
#25
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Derek 86.5: "Arent the torque and HP curves supposed to intersect at 5250 rpm?"
They do.
Top chart is HP, bottom chart is torque.
If you look at each chart they're in the same spot at 5250rpm, about 410 hp/lb-ft.
They do.
Top chart is HP, bottom chart is torque.
If you look at each chart they're in the same spot at 5250rpm, about 410 hp/lb-ft.
#26
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Lagavulin: Good eye for detail bro.
Corrected for atmo pressure at SL the correct baro reading is 32.16, so it's safe to say the above dyno runs are wildly optomistic.
Hence my problem with dynos.
It's obvious that using the same multiplier for both runs he still made gobs more power than stock though.![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
Take it to the dragstrip and then use the ET/Trap formulas of your best runs and average the two. You'll know within about +/- 5hp how much you're actually effectively using.
Corrected for atmo pressure at SL the correct baro reading is 32.16, so it's safe to say the above dyno runs are wildly optomistic.
Hence my problem with dynos.
It's obvious that using the same multiplier for both runs he still made gobs more power than stock though.
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
Take it to the dragstrip and then use the ET/Trap formulas of your best runs and average the two. You'll know within about +/- 5hp how much you're actually effectively using.
Last edited by m21sniper; 07-09-2005 at 04:22 PM.
#27
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Originally Posted by Lagavulin
No, I don't think so: current barometric pressure is 30.02 in.
http://www.weather.com/weather/local...om=search_city
http://www.weather.com/weather/local...om=search_city
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#28
Racer
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It was also 105 degrees in the shop. I think it was discussed and decided not to correct for biometrics, but I will have to check. I plan on going to Atlanta next weekend to finish tuning, so I will have another shops dyno results. I am curious to see the difference myself.
#29
Three Wheelin'
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Originally Posted by m21sniper
Lagavulin: Good eye for detail bro.
![thumbup](https://rennlist.com/forums/graemlins/thumbup.gif)
Corrected for atmo pressure at SL the correct baro reading is 32.16, so it's safe to say the above dyno runs are wildly optomistic.
Hence my problem with dynos.
Hence my problem with dynos.
Using your reasoning, the next time you get a flat tire, are you going to forgo using rubber-based tires, and install wooden-spoked-wagon-wheels instead because they'll never lose any air? I don't think so since you'll examine why you got the flat, and subsequently avoid construction sites and their nails lying all over the place. It's the same thing with this dyno: all the clues were right there.
It's obvious that using the same multiplier for both runs he still made gobs more power than stock though.
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
![Cheers](https://rennlist.com/forums/images/smilies/beerchug.gif)
Take it to the dragstrip and then use the ET/Trap formulas of your best runs and average the two. You'll know within +/- 5hp how much you're actually producing.
#30
Drifting
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I totally agree....
Dynos have much less variables, and they can be corrected.
There are far too many factors in a drag race. Vehicle weight, driver weight, driver skill, tire type, tire diameter, track conditions, etc... It's impossible to correct 1/4 mile times to accomodate those factors. But a dyno chart is pretty easy to compare... It will show what power you have, then it's just up to you if you can use it properly, and actually get good times...
Dynos have much less variables, and they can be corrected.
There are far too many factors in a drag race. Vehicle weight, driver weight, driver skill, tire type, tire diameter, track conditions, etc... It's impossible to correct 1/4 mile times to accomodate those factors. But a dyno chart is pretty easy to compare... It will show what power you have, then it's just up to you if you can use it properly, and actually get good times...