No-one is saying gearing increases the amount of power your engine makes, but it increases the amount of power that gets to your WHEELS. The engine only makes 120ft-lbs of torque, well 120ft-lbs can’t move a 2700lbs car, that’s where gearing comes in.
But the fact remains: gear ratios don’t change the power of the engine.(Unless through some resonance issues at certain RPMs/loads) That is my point.
In case you haven’t noticed, chassis dyno’s DON’T measure the power of the engine, they measure the power at your wheels, AFTER it’s been multiplied by your gearing. So obviously it would be susceptible to gearing bias.
A stock Integra actually puts down around 610ft-lbs of peak torque in 3rd gear.
110wtqx1.259(gear)x4.4(fd) = 610
An Integra with the exact same engine but an S1 tranny puts down more like 705ft-lbs to the ground.
110wtqx1.458(gear)x4.4(fd) = 705
That’s all the physics I need to know. Increasing your gear ratios increase the amount of torque(and HP) that your car puts to the ground, and it also increases your acceleration, of course at the cost of your top-speed.
everything you posted is exactly what i was going to post.
I’m not trying to start an internet argument, but if a chasis dyno is to measure power AT THE WHEELS, then I don’t see why it would not factor in gearing, as that’s a big factor of output at the wheels. I do know there are some chasis dynos that are setup through result correction to measure engine power, though.
PS: (yes, it’s a 2L, and I’ve been to the dyno place enough, so i’m sure they won’t mind letting me do a few extra runs. The hard part is remembering to do it :p)
This disagreement is funny… at least you guys havent resorted to name calling, showing the maturity is cool. Its simpler than you all are explaining too.
if you have a 200 hp itr motor, its 200hp no matter what. now, when you add a transmission to this engine, it is going to take away power. NO matter what trans it is in the entire world, (unless this transmission has a engine inside of it), will it make ANY additional power for that motor. a transmission is a way to use the power, it doesnt make any additional power.
now the hp gains you are seeing isnt because of the transmission, its just not robbing your engine of any additional power. you still have a 200 hp engine wether your using a ls or a b16. the fact is probably that your ls trans may have had more miles and the bearings dragged more, or teeth had more drag on them or something to that fact. thats all…
The whole point of your posts is that changing gearing results in a higher reading on a chassis dynometer. This isn’t true. That is my point. It does apply more torque to the rollers in lower gears, but it does it over a smaller speed range, therefore the dyno reads the same hp & torque, regardless of gear. Any other variation is due to differences in drivetrain efficeiency and other engine or enviromental factors.
In case you haven’t noticed, chassis dyno’s DON’T measure the power of the engine, they measure the power at your wheels, AFTER it’s been multiplied by your gearing. So obviously it would be susceptible to gearing bias.
No, they don’t measure engine power directly, but no, they also should not be subject to gearing bias as I explained countless times. The only way that gearing can change the readings is through better/worse power transfer effciency.
That’s all the physics I need to know. Increasing your gear ratios increase the amount of torque(and HP) that your car puts to the ground, and it also increases your acceleration, of course at the cost of your top-speed.
I’m glad you understand how gearing works. If you could just understand how a chassis dyno works, we’d be all set. Now, what you just wrote is true, and I have never claimed otherwise. But I did claim that the gear ratios don’t effect chassis dyno readings. That I stand by.
The concept of the amount brute torque applied to the rollers not changing the readings may be a little counter intuitive, but if you think it through, and see that he added power happens in a smaller speed range, therefore negating the possible power boosting lower gears, it makes sense.
Also, I suspect having a Mustang guy come in and tell you your tuning assumptions are wrong is a bit of a kick in the nuts. It’d be like having some guy come over and tell you how to pleasure your woman. But I’m just trying to clear up a misconception. You guys clearly understand gearing now just take it 1 step further.
That’s because you don’t understand how a chassis dyno works. It measures the difference of roller speed vs time and then plots that against RPM. Lower gears allow you to accelerate the drum(s) faster, but over a smaller speed range compared to a higher gear. Which results in the same reading regardless of gear ratio.
If we followed the math you guys use, and were driving say something with a T56 in it, and had a car that made 100hp & 100ft/lbs of torque, the chassis dyno would see about 300hp & 300ft/lbs of torque, assuming a 1:1 final drive ratio and no parasitic loss. Now as you see it, the chassis dyno would read exactly that, 300/300. Now, we decide to pop it into 6th with a 0.5:1 ratio, according to you guys, the dyno now sees 50hp & 50ft/lbs of torque. Right?
Wrong. The chassis dyno sees 100/100 in any gear (assuming no wheel spin or other extranius variables) because of the speed range that the car can accelerate the dyno drum(s).
PS: (yes, it’s a 2L, and I’ve been to the dyno place enough, so i’m sure they won’t mind letting me do a few extra runs. The hard part is remembering to do it :p)
If you can do this, please do. Hell, if you can do it in first, so much the better.
the tiny variations of drag you are referring to could never account for the huge differences in the dyno,
you’re telling me that in a car where the entire drivetrain loss, form flywheel to pavement, is only about 12%(130bhp dyno around 115whp), that somehow by switching trannies a different tranny with less “drag” will somehow free up 10whp? that’s nearly an increase of 7%, it’s impossible!
If it’s truly random as you seem to think, why are people consistently showing higher numbers in 3rd gear, as well as with the S1 trannies? It’s not just coincidence.
For the guy that said trannies do not make any additional power, you DO NOT get it! Do you understand how gearing works? It multiplies force. It does definately create power. It’s like using a breaker bar, although your arm is still the same strength, the power you put on the bolt see is much higher.
Now as you see it, the chassis dyno would read exactly that, 300/300. Now, we decide to pop it into 6th with a 0.5:1 ratio, according to you guys, the dyno now sees 50hp & 50ft/lbs of torque. Right?
No-ones saying that. These dynos are not perfect, they measure the amount of force at the wheels, they then have to work backwards to figure out how much HP the engine itself is actually making. They give you an approximation of what they think the engine is making.
All we’re saying is that using shorter gears results in higher numbers on the dyno, it’s not a direct relationship, but it definately has an effect. You can claim it “shouldn’t” have an effect all you like, but the bottom line is IT DOES!
There’s a huge difference between “it shouldn’t” and “it doesn’t.” One is theory, other is what actually happened.
You can’t deny all of our first-hand experiences and claim it was all just fluke, by some miracle the more aggressive gears also create less drag.
Maybe your understanding of how a dyno works is not complete, have you ever built one? How can you be so sure you know the inner workings of the dynojet’s?
obviously you’re understanding of how a dyno works is flawed, otherwise these variations we’re seeing would not exist! If everything was truly as you say it is, all gears would give identical readings, with 1-2% variation due to drag, however this is not the case in the real world.
If everything was as you say, there would be absolutely no reason for the dyno operator to choose the gear closest to 1:1 ratio, but again in the real world they always do…I wonder why…possibly to negate GEARING BIAS?? Ya think?
I agree largely. I suspect it is more than tranny drag.
That’s ridiculous, gears can not create that amount of drag, and isn’t it a strange coincidence that everyons sees GAINS when they switch to the SI?
If people get more power after an S1 swap, then the tranny is likely more effecient, or allows the engine to take somewhat better advantage of resonance tuning. Or possibly, there could be be other things as well, like additional part have also been added or there was a more recnt tune up.
As I understand it you claim there are power gains found by switching trannies, and yet it isn’t due to the engine making more power, and it can’t be explained by the parasitic loss of the LS tranny, my total amount of acceleratio over time equation is BS, and to you, physics takes the day off here, and more power results. :bs:
If it’s truly random as you seem to think, why are people consistently showing higher numbers in 3rd gear, as wella s with the S1 trannies? It’s not be coincidence.
I would never claim the power difference is random. Clearly, even identicle new cars cars produce more or less power than others right off the showroom floor, but there is a reason for it. It isn’t a random thing, there are just a lot of variables to consider.
If people are in fact getting more power from 3rd gear than 4th, then it is due to effciency being better in 3rd. As I stated above, if the S1 swap results in more power then it is due to effciency of the tranny.
For the guy that said trannies do not make any additional power, you DO NOT get it! Do you understand how gearing works? It multiplies force. It does definately create power.
He gets how gearing works, but he also gets how dynos and power measuring works. The second part is where you fall down.
No-ones saying that. These dynos are not perfect, they measure the amount of force at the wheels, they then have to work backwards to figure out how much HP the engine itself is actually making. They give you an approximation of what they think the engine is making.
They measure acceleration over time plotted against RPM. They don’t “work backwards”.
All we’re saying is that using shorter gears results in higher numbers on the dyno, it’s not a direct relationship, but it definately has an effect. You can claim it “shouldn’t” ahve an effect all you like, but the bottom line is IT DOES!
So the big differences you alluded to earlier in this message are now minor ones?
Or, you say that there is a relationship between dyno numbers and gear ratios, however it isn’t a direct relationship or one that follows any formula it just exists in the ether? Science and physics be damned?
You can’t deny all of our first-hand experiences and claim it was all just fluke, by some miracle the more aggressive gears also create less drag.
I can, and I will. Further I don’t see a great deal of evidence here. I see 2 guys with a tenuous grasp of physics. Guys who clearly don’t get how power is measured and how a dyno works.
In every honda I’ve ever driven 3rd gear is by far the most beat up gear, so it makes sense that 4th would be creating less drag than 3rd which is by far the most abused gear.
So now 3rd isn’t effcient? I’m so confused. Oh I see. You are saying that 3rd gear has more friction, so ergo the difference in the dyno curves should be actually that 3rd has lower power but due to mechanical advantage, the results of 3rd gear pulls are actually higher? So I would assume if you had a brand new tranny, 3rd would outright rape 4th right?
I’m kinda repeating myself over and over again. I wish there was a mechanical engineer in the house.
Let me one last time to see if I can put this in terms that a 4 year old can understand:
You are riding your trike. You encounter a hill. You have 2 options:
grunt like a Mofo and really put your back into the pedaling.
gear down and make pedaling easier, but a lot more.
In either option 1 or 2 you will have to use the same amount of energy. The gearing doesn’t matter. I mean damn, this isn’t rocket science.
what you don’t understand is the Dyno is not a perfect measuring tool. Let me repeat…the Dyno is not a perfect measuring tool…
It uses computer software to calculate your horsepower. One variable it uses in this equation is the force, which is directly related to your gear ratio.
Changing gear ratios skew the results, even though it’s not actually changing the output of the engine.
In our cars using the higher gears seems to show about a 10whp gain on the dyno, hence the original comment that the original poster is probably using an LS tranny, because his should be higher,
so, i’m done arguing, you seem to think I don’t understand the logic behind measuring hp, which isn’t true, I’m saying the chassis dyno is an imperfect tool that can be skewed up OR down by changing gear ratios.
Do a web search and you’ll see many discussions on this, apparently in corvettes they lose 10-15whp on the dyno when they switch to a more aggressive gear set. It’s the oppsite scenario as here, but it’s further proof that the chassis dyno is definately affected by the gear ratios. http://forums.corvetteforum.com/showthread.php?p=1550092185#post1550092185
-another 6 people who saw a major difference in dyno readings when changing gear ratios, if you’re counting
work = (force) X (distance object is moved)
power = (amount of work)/(time it took to do work)
We can all agree that “power” does not change - it is at some fixed value determined by the engine. It is also a fact that when dyno tests are done, it takes a certain amount of time for the rollers to spin 1000 times, and that amount of time changes depending on what gear is used. (i.e. 5th gear run would take longer to turn the drum 1000 times than 1st gear.)
Now looking at the engine crank… the engine transforms thermal energy (gasoline explosions in the combustion chamber) into mechanical energy (a force on the crank) via the pistons. There is a certain amount of force exerted on the crank. Ideally, that force varies directly with engine RPM. That same force is then manipulated (multiplied) by gears. BUT, the amount of “work” done MUST remain the same. (i.e. for a 2:1 gear ratio, the engine MUST turn 2 times to get the wheels to turn once) So if you double the “force” through gears, the distance the object can be moved is only half.
Now power is measured by dividing the amount of time it takes to move that said object. If the object is to be moved in half the time, the power MUST be doubled. Correct?
Taking this and applying to the dyno, where the drums are measured in number of rotations (distance) in a given amount of time, “power” MUST remain constant in ANY given gear. In a perfect system (no losses), a 2x force multiplier “SHOULD” be able to move the object the same distance in half the time given the SAME power output.
But because in real life, the system is NOT perfect and there are losses in force transfers between gears, you’ll get power readings that are different as measured from the crank to the wheels. This is apparent in that WHP is lower than Crank HP.
The argument that one gear can “produce” more HP than another is an argument in semantics. I will stand by the statement that one gear will induce LESS parasitic losses than another.
“IF” you were able to measure EVERY little piece of parasitic power loss, from thermal buildup in tranny fluid to thermal buildup in the tires, you SHOULD be able to find that the power as measure at the wheels is the same REGARDLESS of the gear ratio used.
To say that one gear ratio produces more power is implying creation of energy. Last I checked, laws of conservation of energy remain intact. (Ever play pool? ← best example of conservation of energy/momentum.)
I’m sure we’re all thinking the same thing, but the words are just coming out wrong.
Nobody is saying gearing will magically give the engine more power. nobody is saying the laws of physics are untrue either.
What we are getting at is from our personal experience, we’ve noticed gearing will skew the results on the chasis dyno…why? i don’t know, because i don’t design or assemble dyno’s.
All i know is this:
with a LS tranny, doing back to back runs, a 3rd gear pull gave me a higher ouput than 4th gear.
my 4th gear pull with my S1 tranny gave me a higher output than my LS did in 4th gear.
maybe the dyno i’m using is messed up…maybe not.
either way, i’ll try to squeeze in a couple extra runs on the dyno next week (appointment is for next THUR). Keep in mind that i’m going on the dyno for tuning, so it’ll have to be time permitting. If i can’t do a 3rd gear run (possible traction issues), then i’ll do a 5th gear vs. a 4th gear comparison.
hehe. i dont know who is right/wrong here but it sounds like orangestang has got it. from what i DID pay attention to in science class in highschool, it only seems right that gearing would have no effect on power to the wheels. i really like comparison to the bike. dont matter what gear you’re in, the same legs with the same amount of power are pushing the pedals, reguardless of how fast you are going.
Assuming you aren’t attempting to use some enviromental correction factor, and are dealign with raw data, and the dyno is working correctly, it is a perfect measureing tool. It can almost perfectly measure the power produced to the drums in that exact time and place, with that exact setup.
All the dyno needs to measure hp and torque is a formula, a tachometer on the drums, a clock, and a known weight of the drum(s). If all these work, then it is as close to a perfect measurement of power to the wheels as you can get in that enviromental/engine variable situation.
It uses computer software to calculate your horsepower. One variable it uses in this equation is the force, which is directly related to your gear ratio.
OK, I think we are getting to the part where you are unclear. It measures the amount of force applied to the drum by comparing the amount of drum acceleration vs the time it took to accelerate. It isn’t like they position a big spring on the drum and see how far it stretches.
Changing gear ratios skew the results, even though it’s not actually changing the output of the engine.
No. It doesn’t. Not unless there is some other factor at play like engine/tranny effciency.
In our cars using the higher gears seems to show about a 10whp gain on the dyno, hence the original comment that the original poster is probably using an LS tranny, because his should be higher,
It is not due to gear ratio change. Would you argue then that 2nd should pick up another 10hp? ANd, then first another 10? Until finally you 140hp engine is making 150 @ the wheels in 1st? I can’t beleive you guys think my logic and math sucks.
so, i’m done arguing, you seem to think I don’t understand the logic behind measuring hp, which isn’t true, I’m saying the chassis dyno is an imperfect tool that can be skewed up OR down by changing gear ratios.
OK, so now you conclude that 3rd gear doesn’t add any power and the difference is dyno error? Well I have to admit, that could be true, the operator may have used some kind of incorrectly applied correction factor or something. This exactly one of the types of interveneing factors I’ve been rambling about for the last 3 pages of posts.
What I don’t get is in the first part of your response you stick to your original flawed arguement that gear ratios change power, now you seem to be blaming it on an “imperfect dyno”. Which is it?
I’ll guess it is the option that allows you to wriggle out and save face.
Do a web search and you’ll see many discussions on this, apparently in corvettes they lose 10-15whp on the dyno when they switch to a more aggressive gear set. It’s the oppsite scenario as here, but it’s further proof that the chassis dyno is definately affected by the gear ratios.
-another 6 people who saw a major difference in dyno readings when changing gear ratios, if you’re counting
I never once denied that there may be differences. Effceiency between gears, ECU changes, differences in resonance tuning in the intake and exhaust can all play a role. But as I have said in practically every post: It isn’t the ratios themselves changing output!
I don’t get it. I mean, the link you just gave even supports my point. Countless time you guys said that an “aggressive” gear set gives more power. Now you link me to something that contradicts your point? I’ll save you the embarassment of actually quoting all the times you were wrong.
Based on my original expereinces, i saw many examples of people, including myself, gaining power on the dyno by changing their gear ratios. Based on that I concluded that increases in gear ratio skewed your dyno results upwards.
Now that I’ve read the corvette post I had to re-evaluate my opinion, because these guys are actually losing power while moving to larger gears. All I can say now is that altering the stock gearing skews the results, but whether it increase or decreases, and how much so, seems to be specific to the applciation, as well as the specific model of dyno.
Either way it shows that gearing can have a dramatic impact on chassis dynos, if the gearing is not the cause of these differences, then why did representatives from Dynojet admit that the problem existed, and claim it would be fixed in the post-2005 models?
The Dynojet people themselves have admitted their dyno has some problems, why can’t you?
My main problem with your claim that the difference is due to friction losses are these: #1 - the difference are much too big to be attributed to such tiny factors as incresed friction on the gears. In other words, there’s no way a drivetrain that only has 12% loss, can gain 7% of it’s power back by simply using a more efficient gear.
#2 - the results are repeatable, everyone who is throwing the S1 trannies, and seeing a change, is seeing a positive gain. All the corvette guys that are using the 4.10 gears, and seeing a change, are seeing a negative change. Factors like gear efficiency are not constant, so the changes should not be consistent and repeatable, but they are.
#3 - The Ys1 and S1 trannies are nearly identical, they are literally impossible to tell apart form the outside, for the most part the gears inside are interchangeable, so I don’t see how the S1 can be so drastically “more efficient”
But I’m just trying to clear up a misconception. You guys clearly understand gearing now just take it 1 step further.
I always wondered how a dyno worked.