3rd gear pulls on dyno or 4th gear pulls which is better?
05-30-2004, 06:37 PM
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3rd gear pulls on dyno or 4th gear pulls which is better?
i was just curious about what the tuners prefer when on the dyno? i had really bad wheel spin in 3rd pulls and even in 4th gear pulls but not as bad. why do some people choose 3rd over 4th on the dyno? is there any pros/cons to one or the other?
05-30-2004, 06:53 PM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (NextelBuddy)
Honestly, this is going to depend on the trans. The reason every other automaker other than Honda (and Mitsu if I remember correctly) are dynoed in fourth is because the ratio is 1:1. There is no more torque multiplication in 4th and up. Usually.
On the Honda trannies, 4th gear isn't 1.00:1. on an ITR for example it's 1.107. Third would be 1.458 and fifth is 0.848. LS gears and the GSR gears are different as well, but to my knowledge, not one of them are 1.00.
To put it in perspective, imagine if your car made 100ft/lbs of torque at the crank. Dynoing in 4th would show 110.7ft/lbs (100x1.107). Dynoing in 3rd would show 145.8ft/lb (100x1.458). Everyone who saw your dynochart would say "WOW!! look at that killer-diller torqueriffic beast!!" but all you did was dyno in a lower gear. If torque readings aren't important to you, you could just as well dyno in 5th and not have a problem with it - from a traction standpoint. Just as long as you keep it consistent.
On the Honda trannies, 4th gear isn't 1.00:1. on an ITR for example it's 1.107. Third would be 1.458 and fifth is 0.848. LS gears and the GSR gears are different as well, but to my knowledge, not one of them are 1.00.
To put it in perspective, imagine if your car made 100ft/lbs of torque at the crank. Dynoing in 4th would show 110.7ft/lbs (100x1.107). Dynoing in 3rd would show 145.8ft/lb (100x1.458). Everyone who saw your dynochart would say "WOW!! look at that killer-diller torqueriffic beast!!" but all you did was dyno in a lower gear. If torque readings aren't important to you, you could just as well dyno in 5th and not have a problem with it - from a traction standpoint. Just as long as you keep it consistent.
05-30-2004, 10:02 PM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (1316130057)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1316130057 »</TD></TR><TR><TD CLASS="quote">Honestly, this is going to depend on the trans. The reason every other automaker other than Honda (and Mitsu if I remember correctly) are dynoed in fourth is because the ratio is 1:1. There is no more torque multiplication in 4th and up. Usually.
On the Honda trannies, 4th gear isn't 1.00:1. on an ITR for example it's 1.107. Third would be 1.458 and fifth is 0.848. LS gears and the GSR gears are different as well, but to my knowledge, not one of them are 1.00.
To put it in perspective, imagine if your car made 100ft/lbs of torque at the crank. Dynoing in 4th would show 110.7ft/lbs (100x1.107). Dynoing in 3rd would show 145.8ft/lb (100x1.458). Everyone who saw your dynochart would say "WOW!! look at that killer-diller torqueriffic beast!!" but all you did was dyno in a lower gear. If torque readings aren't important to you, you could just as well dyno in 5th and not have a problem with it - from a traction standpoint. Just as long as you keep it consistent.</TD></TR></TABLE>
so the tuner would have to know which tranny your using to determin the correction factor?
Reason I ask is because my first dyno runs were done in 3rd gear, and when I retuned my dyno runs were done in 4th gear (different shop)..power reading are different but thats probably due to the better tuning.
On the Honda trannies, 4th gear isn't 1.00:1. on an ITR for example it's 1.107. Third would be 1.458 and fifth is 0.848. LS gears and the GSR gears are different as well, but to my knowledge, not one of them are 1.00.
To put it in perspective, imagine if your car made 100ft/lbs of torque at the crank. Dynoing in 4th would show 110.7ft/lbs (100x1.107). Dynoing in 3rd would show 145.8ft/lb (100x1.458). Everyone who saw your dynochart would say "WOW!! look at that killer-diller torqueriffic beast!!" but all you did was dyno in a lower gear. If torque readings aren't important to you, you could just as well dyno in 5th and not have a problem with it - from a traction standpoint. Just as long as you keep it consistent.</TD></TR></TABLE>
so the tuner would have to know which tranny your using to determin the correction factor?
Reason I ask is because my first dyno runs were done in 3rd gear, and when I retuned my dyno runs were done in 4th gear (different shop)..power reading are different but thats probably due to the better tuning.
05-31-2004, 12:12 AM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (1316130057)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1316130057 »</TD></TR><TR><TD CLASS="quote">Honestly, this is going to depend on the trans. The reason every other automaker other than Honda (and Mitsu if I remember correctly) are dynoed in fourth is because the ratio is 1:1. There is no more torque multiplication in 4th and up. Usually.
On the Honda trannies, 4th gear isn't 1.00:1. on an ITR for example it's 1.107. Third would be 1.458 and fifth is 0.848. LS gears and the GSR gears are different as well, but to my knowledge, not one of them are 1.00.
To put it in perspective, imagine if your car made 100ft/lbs of torque at the crank. Dynoing in 4th would show 110.7ft/lbs (100x1.107). Dynoing in 3rd would show 145.8ft/lb (100x1.458). Everyone who saw your dynochart would say "WOW!! look at that killer-diller torqueriffic beast!!" but all you did was dyno in a lower gear. If torque readings aren't important to you, you could just as well dyno in 5th and not have a problem with it - from a traction standpoint. Just as long as you keep it consistent.</TD></TR></TABLE>
So are you saying that the torque numbers from the dyno sheets isn't a true and "near" accurate reading? For example, the dyno reading said 200 torque, would the true torque only be about 150(depending on the tranny and gear)?
On the Honda trannies, 4th gear isn't 1.00:1. on an ITR for example it's 1.107. Third would be 1.458 and fifth is 0.848. LS gears and the GSR gears are different as well, but to my knowledge, not one of them are 1.00.
To put it in perspective, imagine if your car made 100ft/lbs of torque at the crank. Dynoing in 4th would show 110.7ft/lbs (100x1.107). Dynoing in 3rd would show 145.8ft/lb (100x1.458). Everyone who saw your dynochart would say "WOW!! look at that killer-diller torqueriffic beast!!" but all you did was dyno in a lower gear. If torque readings aren't important to you, you could just as well dyno in 5th and not have a problem with it - from a traction standpoint. Just as long as you keep it consistent.</TD></TR></TABLE>
So are you saying that the torque numbers from the dyno sheets isn't a true and "near" accurate reading? For example, the dyno reading said 200 torque, would the true torque only be about 150(depending on the tranny and gear)?
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05-31-2004, 11:45 AM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (b16ahybrid)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b16ahybrid »</TD></TR><TR><TD CLASS="quote">
so the tuner would have to know which tranny your using to determin the correction factor?
Reason I ask is because my first dyno runs were done in 3rd gear, and when I retuned my dyno runs were done in 4th gear (different shop)..power reading are different but thats probably due to the better tuning.</TD></TR></TABLE>
Right. The dyno facility would have to know the gear ratio to give you an accurate number.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by _Endless_ »</TD></TR><TR><TD CLASS="quote">so only torque reading will be affected and not hp?</TD></TR></TABLE>
No, it will affect horse power output readings. The curve will look almost identical, just higher up. The reason for this is (here comes one of my infamous "Unorthodox Theories") Horse Power from a dyno stand point does not really exist. Horse power is a calculation that really has no force to be felt. It just illustrates how the car is using the torque that it makes. Higher HP = more efficient use of the twisting force known as torque. I know a lot of people are probably throwing things at their monitors right now, but consider the reality of the situation: On a typical dyno, there is a roller. What causes the roller to move? The rotational force from the tires. that's torque. So...what device on a dyno measures HP? None. An engine only produces one output, which is torque. HP is just a completely arbitrary number. You could make your own measurement and call it what ever you want and base it off of torque as well. Observe:
At 100ft/lbs of torque at 6000rpm = 171.3hp and look!! it's also 424.3 Bp (Bigboost Power).
I can tell you how much hp is being generated at any RPM if you tell me the torque at that rpm, and I can also do the same with the completely made-up unit of power now known as Bp. The conventional Dyno calculates hp the same way. It dosen't measure hp, it calculates it just like I did. To illustrate this, anybody here give me a torque reading at an rpm and I'll tell you exactly how much hp the car was making.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turtle-eg »</TD></TR><TR><TD CLASS="quote">So are you saying that the torque numbers from the dyno sheets isn't a true and "near" accurate reading? For example, the dyno reading said 200 torque, would the true torque only be about 150(depending on the tranny and gear)?</TD></TR></TABLE>
That depends on how accurate you see as "near accurate". I see any gear ratio that's not 1.00-1.01 as inaccurate. The accuracy will depend soley on the gear ratio.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman »</TD></TR><TR><TD CLASS="quote">well you can input the gear ratios and all that jazz into the dyno software so it can accurately calculate power output.</TD></TR></TABLE>
True, but most shops have a "set it and forget it" gear ratio approach. Hopefully the one in question isn't too lazy to do it, or still remembers it or even still, dosen't say "Hey..I'm taking your word that this is the accurate ratio. What if it isn't?! Now leave me alone, Im trying to finish my lunch."
so the tuner would have to know which tranny your using to determin the correction factor?
Reason I ask is because my first dyno runs were done in 3rd gear, and when I retuned my dyno runs were done in 4th gear (different shop)..power reading are different but thats probably due to the better tuning.</TD></TR></TABLE>
Right. The dyno facility would have to know the gear ratio to give you an accurate number.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by _Endless_ »</TD></TR><TR><TD CLASS="quote">so only torque reading will be affected and not hp?</TD></TR></TABLE>
No, it will affect horse power output readings. The curve will look almost identical, just higher up. The reason for this is (here comes one of my infamous "Unorthodox Theories") Horse Power from a dyno stand point does not really exist. Horse power is a calculation that really has no force to be felt. It just illustrates how the car is using the torque that it makes. Higher HP = more efficient use of the twisting force known as torque. I know a lot of people are probably throwing things at their monitors right now, but consider the reality of the situation: On a typical dyno, there is a roller. What causes the roller to move? The rotational force from the tires. that's torque. So...what device on a dyno measures HP? None. An engine only produces one output, which is torque. HP is just a completely arbitrary number. You could make your own measurement and call it what ever you want and base it off of torque as well. Observe:
At 100ft/lbs of torque at 6000rpm = 171.3hp and look!! it's also 424.3 Bp (Bigboost Power).
I can tell you how much hp is being generated at any RPM if you tell me the torque at that rpm, and I can also do the same with the completely made-up unit of power now known as Bp. The conventional Dyno calculates hp the same way. It dosen't measure hp, it calculates it just like I did. To illustrate this, anybody here give me a torque reading at an rpm and I'll tell you exactly how much hp the car was making.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turtle-eg »</TD></TR><TR><TD CLASS="quote">So are you saying that the torque numbers from the dyno sheets isn't a true and "near" accurate reading? For example, the dyno reading said 200 torque, would the true torque only be about 150(depending on the tranny and gear)?</TD></TR></TABLE>
That depends on how accurate you see as "near accurate". I see any gear ratio that's not 1.00-1.01 as inaccurate. The accuracy will depend soley on the gear ratio.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman »</TD></TR><TR><TD CLASS="quote">well you can input the gear ratios and all that jazz into the dyno software so it can accurately calculate power output.</TD></TR></TABLE>
True, but most shops have a "set it and forget it" gear ratio approach. Hopefully the one in question isn't too lazy to do it, or still remembers it or even still, dosen't say "Hey..I'm taking your word that this is the accurate ratio. What if it isn't?! Now leave me alone, Im trying to finish my lunch."
05-31-2004, 11:47 AM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (Muckman)
well, ive always dynoed 3rd gear, simply because there is less stress on the motor over 4th.
basically the pull is shorter, a 4th gear pull puts tremendous stress on all moving parts for a longer period of time.
thats the way i look at it.
my 4th and 3rd gear pulls were always consistent to each other with Tq and hp.
3rd just takes the load off sooner.
basically the pull is shorter, a 4th gear pull puts tremendous stress on all moving parts for a longer period of time.
thats the way i look at it.
my 4th and 3rd gear pulls were always consistent to each other with Tq and hp.
3rd just takes the load off sooner.
05-31-2004, 01:45 PM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (1316130057)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1316130057 »</TD></TR><TR><TD CLASS="quote">Right. The dyno facility would have to know the gear ratio to give you an accurate number.
"</TD></TR></TABLE>
Interesting, The shop that tuned my car never even asked what tranny I was running. They probably figured a 1:1 ratio for 4th gear.
"</TD></TR></TABLE>
Interesting, The shop that tuned my car never even asked what tranny I was running. They probably figured a 1:1 ratio for 4th gear.
05-31-2004, 03:31 PM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (b16ahybrid)
It doesn't matter what gear you dyno in because the dyno does not know what gear you are in.. It doesn't care either.. All it knows is how fast you accelerated from Xmph-Ymph and your rpm's.. Dynojet's record horsepower and calculate torque always for a 1:1 ratio...
The reason you spin in the lower gears on the dyno is because effectively you are putting more torque down through the gears.. of course it doesn't say that on the screen though cause your torque is always calculated for a 1:1 ratio.
The reason you spin in the lower gears on the dyno is because effectively you are putting more torque down through the gears.. of course it doesn't say that on the screen though cause your torque is always calculated for a 1:1 ratio.
05-31-2004, 04:36 PM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (DIRep972)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DIRep972 »</TD></TR><TR><TD CLASS="quote">It doesn't matter what gear you dyno in because the dyno does not know what gear you are in.. It doesn't care either.. All it knows is how fast you accelerated from Xmph-Ymph and your rpm's.. Dynojet's record horsepower and calculate torque always for a 1:1 ratio...
The reason you spin in the lower gears on the dyno is because effectively you are putting more torque down through the gears.. of course it doesn't say that on the screen though cause your torque is always calculated for a 1:1 ratio.</TD></TR></TABLE>
This is correct.
The reason you spin in the lower gears on the dyno is because effectively you are putting more torque down through the gears.. of course it doesn't say that on the screen though cause your torque is always calculated for a 1:1 ratio.</TD></TR></TABLE>
This is correct.
06-01-2004, 06:54 AM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (DIRep972)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DIRep972 »</TD></TR><TR><TD CLASS="quote">It doesn't matter what gear you dyno in because the dyno does not know what gear you are in.. It doesn't care either.. All it knows is how fast you accelerated from Xmph-Ymph and your rpm's.. Dynojet's record horsepower and calculate torque always for a 1:1 ratio...
The reason you spin in the lower gears on the dyno is because effectively you are putting more torque down through the gears.. of course it doesn't say that on the screen though cause your torque is always calculated for a 1:1 ratio.</TD></TR></TABLE>
How is that possible? The timing lead clips onto an ignition wire and the torque is read from the roller/drum. If you put down more torque it wil calculate more hp as a result. I don't see how it would calculate an absolute reading.
The reason you spin in the lower gears on the dyno is because effectively you are putting more torque down through the gears.. of course it doesn't say that on the screen though cause your torque is always calculated for a 1:1 ratio.</TD></TR></TABLE>
How is that possible? The timing lead clips onto an ignition wire and the torque is read from the roller/drum. If you put down more torque it wil calculate more hp as a result. I don't see how it would calculate an absolute reading.
06-01-2004, 07:24 AM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (1316130057)
Something to consider is that the effects of a lighter flywheel and such will be more so in the lower gears, so you'll probably show a little more power in the higher gears. Either way the gear ratios will never be close to 1:1 because nobody's mentioning the final drive which will bump even a <1:1 to probably around 4:1
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1316130057 »</TD></TR><TR><TD CLASS="quote">The timing lead clips onto an ignition wire and the torque is read from the roller/drum.</TD></TR></TABLE>
Do they clip stuff onto your ignition wire? If they do then they can see your rpm and so the software can calculate your gear ratios. That's probably why they don't ask what transmission you have.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1316130057 »</TD></TR><TR><TD CLASS="quote">The timing lead clips onto an ignition wire and the torque is read from the roller/drum.</TD></TR></TABLE>
Do they clip stuff onto your ignition wire? If they do then they can see your rpm and so the software can calculate your gear ratios. That's probably why they don't ask what transmission you have.
06-01-2004, 08:06 AM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (Lsos)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Lsos »</TD></TR><TR><TD CLASS="quote">
Do they clip stuff onto your ignition wire? If they do then they can see your rpm and so the software can calculate your gear ratios. That's probably why they don't ask what transmission you have.</TD></TR></TABLE>
Yup. Clicks right on like a timing light does. I still don't see how this would let them predict your gear ratio just based off off your engine's RPM though.
Do they clip stuff onto your ignition wire? If they do then they can see your rpm and so the software can calculate your gear ratios. That's probably why they don't ask what transmission you have.</TD></TR></TABLE>
Yup. Clicks right on like a timing light does. I still don't see how this would let them predict your gear ratio just based off off your engine's RPM though.
06-01-2004, 08:53 AM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (1316130057)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1316130057 »</TD></TR><TR><TD CLASS="quote">
Yup. Clicks right on like a timing light does. I still don't see how this would let them predict your gear ratio just based off off your engine's RPM though.</TD></TR></TABLE>
Yeah, I guess they would have to know the size of the wheels...
Yup. Clicks right on like a timing light does. I still don't see how this would let them predict your gear ratio just based off off your engine's RPM though.</TD></TR></TABLE>
Yeah, I guess they would have to know the size of the wheels...
06-01-2004, 09:11 AM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (1316130057)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1316130057 »</TD></TR><TR><TD CLASS="quote">
Yup. Clicks right on like a timing light does. I still don't see how this would let them predict your gear ratio just based off off your engine's RPM though.</TD></TR></TABLE>
it also measures the speed of the rollers. i know cause i can get my graph based on mph or rpm.
if you have rpms, and you have mph, you should be able to figure out the EXACT ratio.
the tranny is not the only thing in the calculation. you have your 1:1 (or any other ratio) in the tranny, then rim size, and finally tire size.
Yup. Clicks right on like a timing light does. I still don't see how this would let them predict your gear ratio just based off off your engine's RPM though.</TD></TR></TABLE>
it also measures the speed of the rollers. i know cause i can get my graph based on mph or rpm.
if you have rpms, and you have mph, you should be able to figure out the EXACT ratio.
the tranny is not the only thing in the calculation. you have your 1:1 (or any other ratio) in the tranny, then rim size, and finally tire size.
06-01-2004, 09:14 AM
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The dyno doesn't predict the gear ratio, nor does it matter the gear ratio.. It calculates power as if you didn't have a transmission at all.. Thats what the 1:1 ratio means.
The dyno has a roller that is a given mass. You accelerate this roller from xmph-ymph.. The roller has a specified diameter that tells you distance. It takes how long it took u to accelerate the roller of a given mass a certain distance and it finds HP.. (work/time) Then it takes the RPM information from your car and calculates the torque... The Roller doesn't record torque, it can't "feel" anything.
The dyno has a roller that is a given mass. You accelerate this roller from xmph-ymph.. The roller has a specified diameter that tells you distance. It takes how long it took u to accelerate the roller of a given mass a certain distance and it finds HP.. (work/time) Then it takes the RPM information from your car and calculates the torque... The Roller doesn't record torque, it can't "feel" anything.
06-01-2004, 09:41 AM
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Like DIRep972 said,
I've seen dyno graphs where the RPM pickup wasn't working correctly and they couldn't record torque. Wouldn't that mean that torque was being calculated and HP was being recorded?
I've seen dyno graphs where the RPM pickup wasn't working correctly and they couldn't record torque. Wouldn't that mean that torque was being calculated and HP was being recorded?
06-01-2004, 11:04 AM
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Re: 3rd gear pulls on dyno or 4th gear pulls which is better? (Lsos)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Lsos »</TD></TR><TR><TD CLASS="quote">
Yeah, I guess they would have to know the size of the wheels...</TD></TR></TABLE>
Wheel diameter plays a part in a cars overall 'effective' gear ratio though, as far as MPH:RPM goes. As long as the dyno knows your engine RPM, it can measure accurately without you having to type in any transmission ratios, because it also knows your MPH.
Yeah, I guess they would have to know the size of the wheels...</TD></TR></TABLE>
Wheel diameter plays a part in a cars overall 'effective' gear ratio though, as far as MPH:RPM goes. As long as the dyno knows your engine RPM, it can measure accurately without you having to type in any transmission ratios, because it also knows your MPH.
06-01-2004, 12:16 PM
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Re: (DIRep972)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">The dyno doesn't predict the gear ratio, nor does it matter the gear ratio.. It calculates power as if you didn't have a transmission at all.. Thats what the 1:1 ratio means.
The dyno has a roller that is a given mass. You accelerate this roller from xmph-ymph.. The roller has a specified diameter that tells you distance. It takes how long it took u to accelerate the roller of a given mass a certain distance and it finds HP.. (work/time) Then it takes the RPM information from your car and calculates the torque... The Roller doesn't record torque, it can't "feel" anything. </TD></TR></TABLE>
Had to do some re-interpeting, but it makes sense now. Thanks. But.....that only explains how a dyno calculates torque. If you had a higher ratio you'll spin the drum with more force and skew the results, no?
The dyno has a roller that is a given mass. You accelerate this roller from xmph-ymph.. The roller has a specified diameter that tells you distance. It takes how long it took u to accelerate the roller of a given mass a certain distance and it finds HP.. (work/time) Then it takes the RPM information from your car and calculates the torque... The Roller doesn't record torque, it can't "feel" anything. </TD></TR></TABLE>
Had to do some re-interpeting, but it makes sense now. Thanks. But.....that only explains how a dyno calculates torque. If you had a higher ratio you'll spin the drum with more force and skew the results, no?
06-01-2004, 01:06 PM
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Re: (1316130057)
Transmission's trade torque for mph. And all RPM's coincide w/ a certain mph right? So if the dyno knows what RPM you have @ Y-MPH, then it basically already knows your total effective gear ratio. (tire dia. + final drive + gear ratio X RPM = MPH)
Modified by DIRep972 at 3:16 PM 6/1/2004
Modified by DIRep972 at 3:16 PM 6/1/2004
06-01-2004, 01:42 PM
#24
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Re: (1316130057)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1316130057 »</TD></TR><TR><TD CLASS="quote">Had to do some re-interpeting, but it makes sense now. Thanks. But.....that only explains how a dyno calculates torque. If you had a higher ratio you'll spin the drum with more force and skew the results, no?
</TD></TR></TABLE>
Yes, it will pick it up as being more torque, so that's why ideally it knows your gear ratio so it can figure out what the real value is.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1316130057 »</TD></TR><TR><TD CLASS="quote">Wheel diameter plays a part in a cars overall 'effective' gear ratio though, as far as MPH:RPM goes. As long as the dyno knows your engine RPM, it can measure accurately without you having to type in any transmission ratios, because it also knows your MPH.
</TD></TR></TABLE>
I'm still confused about this, even though I started it.....you could be going 30mph at 3000rpm or 30mph at 6000rpm with the same gear ratio, depending on the size of the wheels. So, it can't really tell you gear ratio without more information. It can tell how much force the wheel is putting out, but in order to figure out torque at the wheels it still needs the wheel size or gear ratio...
but something doesn't seem right with that too....am I wrong here? I guess i need to think about it more...
</TD></TR></TABLE>
Yes, it will pick it up as being more torque, so that's why ideally it knows your gear ratio so it can figure out what the real value is.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1316130057 »</TD></TR><TR><TD CLASS="quote">Wheel diameter plays a part in a cars overall 'effective' gear ratio though, as far as MPH:RPM goes. As long as the dyno knows your engine RPM, it can measure accurately without you having to type in any transmission ratios, because it also knows your MPH.
</TD></TR></TABLE>
I'm still confused about this, even though I started it.....you could be going 30mph at 3000rpm or 30mph at 6000rpm with the same gear ratio, depending on the size of the wheels. So, it can't really tell you gear ratio without more information. It can tell how much force the wheel is putting out, but in order to figure out torque at the wheels it still needs the wheel size or gear ratio...
but something doesn't seem right with that too....am I wrong here? I guess i need to think about it more...
06-01-2004, 04:03 PM
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Re: (Lsos)
basically you guys are saying that if you dyno in third and fourth gear back to back, the numbers in third will always be higher?
Has anybody test proven this?
It's a given in third gear you will have more torque and therefore it should register higher on the dyno but somehow I am not sure it actually does in most cases.
Has anybody test proven this?
It's a given in third gear you will have more torque and therefore it should register higher on the dyno but somehow I am not sure it actually does in most cases.