Gear swap and HP loss on dyno??
04-17-2002 | 04:20 PM
#1
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Gear swap and HP loss on dyno?? I tried searching for this but nothing came up that I could see. I know it's been posted before but if someone could enlighten me. What is the cause of HP loss on the dyno when going to a steeper gear?
Thanks
Brian
<small>[ April 17, 2002, 09:18 PM: Message edited by: HntrGrnZ ]</small>
Thanks
Brian
<small>[ April 17, 2002, 09:18 PM: Message edited by: HntrGrnZ ]</small>
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01 NBM Z28- A4 w/3.23s, TSP Black Lid, Hooker Catback, Pacesetter Headers w/ORY, ASP Pulley, Ported Throttle Body, TSP Torq. v3(231/234) Camshaft, TCI 4400, PRC Stg 1 Heads
Texas Speed & Performance
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01 NBM Z28- A4 w/3.23s, TSP Black Lid, Hooker Catback, Pacesetter Headers w/ORY, ASP Pulley, Ported Throttle Body, TSP Torq. v3(231/234) Camshaft, TCI 4400, PRC Stg 1 Heads
Texas Speed & Performance
www.texas-speed.com
(806) 866-0734
04-18-2002 | 09:58 AM
#2
Re: Gear swap and HP loss on dyno?? Brian,
Higher ratio gears will give you lower chassis dyno numbers for a strange, but logical reason. In essence, the DynoJet calculates hp based on the time it takes to spin up the 2800lb roller assembly. It's basically work divided by time and rpm. Think about this: If you car is at idle in neutral and you stab the throttle, it will take time to accelerate to redline...let's say 1.1 seconds. Now let's say it takes 8.2 seconds for your car to accelerate the DynoJet from low speed to top speed with 3.23 gears and 7.3 seconds with 3.73 gears. Dyno printout says 355 rwhp with 3.23 gears and 346 rwhp with 3.73 gears...why?
Think aabout this: In the 8.2 seconds it takes to spin the rollers with 3.23 gears, it would still take the motor about 1.1 seconds to overcome its own inertia (idle to redline). There's about 13.4% of the work used just to accelerate the motor itself. With 3.73 gears, the time to reach redline decreases to 7.3 seconds. Divide the 1.1 seconds into the 7.3 seconds and you will see that overcoming the internal engine inertia costs 15.1% of the work with 3.73 gears. There is less hp available during this time period to spin the rollers so the DynoJet will read a slightly lower hp figure. Make sense, or did I lose you?
BTW, you have mail.
Higher ratio gears will give you lower chassis dyno numbers for a strange, but logical reason. In essence, the DynoJet calculates hp based on the time it takes to spin up the 2800lb roller assembly. It's basically work divided by time and rpm. Think about this: If you car is at idle in neutral and you stab the throttle, it will take time to accelerate to redline...let's say 1.1 seconds. Now let's say it takes 8.2 seconds for your car to accelerate the DynoJet from low speed to top speed with 3.23 gears and 7.3 seconds with 3.73 gears. Dyno printout says 355 rwhp with 3.23 gears and 346 rwhp with 3.73 gears...why?
Think aabout this: In the 8.2 seconds it takes to spin the rollers with 3.23 gears, it would still take the motor about 1.1 seconds to overcome its own inertia (idle to redline). There's about 13.4% of the work used just to accelerate the motor itself. With 3.73 gears, the time to reach redline decreases to 7.3 seconds. Divide the 1.1 seconds into the 7.3 seconds and you will see that overcoming the internal engine inertia costs 15.1% of the work with 3.73 gears. There is less hp available during this time period to spin the rollers so the DynoJet will read a slightly lower hp figure. Make sense, or did I lose you?
BTW, you have mail.
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2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
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2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
04-18-2002 | 10:27 AM
#3
Re: Gear swap and HP loss on dyno?? Patrick:
that's an interesting theory.
Has anyone measured rear end fluid temperature change on a 20 - 120 punch with 2.73 gears versus 3.73s? It would be interesting to see if there is any mechanical effect. If the 3.73 fluid got hotter, then some HP would be convertered to heat.
that's an interesting theory.
Has anyone measured rear end fluid temperature change on a 20 - 120 punch with 2.73 gears versus 3.73s? It would be interesting to see if there is any mechanical effect. If the 3.73 fluid got hotter, then some HP would be convertered to heat.
04-18-2002 | 03:32 PM
#4
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Re: Gear swap and HP loss on dyno?? What does work represent?
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01 NBM Z28- A4 w/3.23s, TSP Black Lid, Hooker Catback, Pacesetter Headers w/ORY, ASP Pulley, Ported Throttle Body, TSP Torq. v3(231/234) Camshaft, TCI 4400, PRC Stg 1 Heads
Texas Speed & Performance
www.texas-speed.com
(806) 866-0734
01 NBM Z28- A4 w/3.23s, TSP Black Lid, Hooker Catback, Pacesetter Headers w/ORY, ASP Pulley, Ported Throttle Body, TSP Torq. v3(231/234) Camshaft, TCI 4400, PRC Stg 1 Heads
Texas Speed & Performance
www.texas-speed.com
(806) 866-0734
04-18-2002 | 05:47 PM
#5
Re: Gear swap and HP loss on dyno?? Work is horsepower. A scientific explanation would take a few pages.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
04-19-2002 | 03:57 PM
#6
Re: Gear swap and HP loss on dyno?? Come on Patrick, I have some time this afternoon for some reading. Knock yourself out. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
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04-19-2002 | 05:37 PM
#7
Re: Gear swap and HP loss on dyno?? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> What does work represent?
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Work is the physical transfer of energy between systems.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> Come on Patrick, I have some time this afternoon for some reading. Knock yourself out. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The latter quote represents the absence of work. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Work is the physical transfer of energy between systems.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> Come on Patrick, I have some time this afternoon for some reading. Knock yourself out. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The latter quote represents the absence of work. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
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04-19-2002 | 06:49 PM
#8
Re: Gear swap and HP loss on dyno?? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Ragtop 99:
<strong>[QUOTE] The latter quote represents the absence of work. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">LMAO! light schedule today <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
<strong>[QUOTE] The latter quote represents the absence of work. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">LMAO! light schedule today <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
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