I was told that if your in 5th gear, going 80mph and than you are below 4k rpm’s then thats a stock tranny but if your going 80mph in 5th gear and your at 5k than you have short geared tranny. I have an S1 tranny but I couldn’t tell what was what until I was told this…these short geared tranny’s suck when on the freeway but thats when you would swap in an LS 5th gear.
my buddy has a jdm gsr with skunk2 intake manifold stock intake box stock header and test pipe and greddy exaust and hes putts down 172 at the wheels
:hmm: :hmm: are you sure at the wheels? He has to have a more mods than that
I have dyno’d my car with my YS1 and then with a S1 and there is a good gain of ~10whp and ~10lb-ft.
you can also dyno in 2nd gear, opposed to 4th gear and get more favourable results, so i fail to see how that is true.
Then you fail to grasp how the dyno works. It is true that you will be applying more torque to the dyno, and this will accelerate the drums faster, however it will not accelerate them to the range in speeds.
For example, if an engine is geared 1:1 with a tire, depending on RPM range and tire size the engine might accelerate the drums from 30mph to 90mph in 10 seconds while it revs from 2000-6000rpm.
Now assuming no loss in the driveline, the same engine geared 2:1 should accelerate the drums from 15mph to 45mph in 5 seconds while reving from 2000-6000rpm. So it takes half the time to get through the RPM range but the drums have only accelerated 30mph, versus 60mph in the 1:1 example.
Now if you follow me so far you may begin to realize that the power and torque produced by the engine is exactly the same regardless of the gear ratio. You can’t run super deep gears and transform your stock motor into a 900hp motor. It doesn’t work like that. Even if you dyno in 1st gear.
Now a chassis dyno measures power to the wheels. Now that I have hopefully made my point that gear ratio doesn’t effect power readings, you may deduce that the increase in power that you may get switching trannies has nothing to do with the gear ratios. It can have something to do with the effciency and parasitic drag of the trannies.
*You may see some difference in automatic equiped cars in different gears due to the flash characteristics of the torque converter, but that should not be an issue with manual transmission cars.
Now, to address your claim of getting better results in 2nd gear, I suspect that there are other variables at play that would seem to make the power curve seem better.
Also, I’m not saying that a tranny swap won’t improve performance, I’m just saying that changing the gear ratios does not make your engine have more power.
Nice logical explanation. Could not have done it better!
Power is developed in the engine. Everything else just takes away from it. So changing gear ratios cannot “give” more power. Changing trannies can help reduce the amount “taken away” though.
No you guys are both wrong, it depends on the type of dyno, some dyno’s calculate your gearing on the fly, others don’t
On a dynojet I did back to back 3rd and 4th gear runs and I changed nearly 10whp by dynoing in 3rd,
Of course changing trannies can give more power, power originates at the engine but it is multiplied many times over by the gear ratios and final drive, the higher the ratio the more torque you make at the wheels.
Why do you think dyno operators always try to dyno in the gear that is closes to a 1:1 ratio?
You guys can argue logic all you want, but we’re all telling you with real life experience that we’re gaining power by dynoing in higher gears, or swapping in higher geared trannies, that’s why it’s so important that I always dyno my car in the same gear as my baseline, otherwise there’s nothign to compare to, you get totally different readings.
Alot of people dyno in 3rd gear to get better results, even though 4th is closer to a 1:1 ratio.
couldnt clutch slippage cause a difference in the reading?
i thought this because i suspect people put in a new clutch when changing the transmission… could be changing from old to new clutch :hmm:
that wouldn’t explain why i can dyno 3rd&4th back to back and get completely different results,
like I said it depends on the dyno, I’ve argued with people about this before, some people have dynoed their cars in different gears and gotten nearly identical reading, for some reason they think this is the way all dyno’s work.
But from my experience, and obviously that of more than a few other people, changing gear ratios has a dramatic impact on the amount of HP shown by the dyno. This was on a Dynojet 3000,
I also used a dynapack dyno, but didn’t try different gears, however from what I’ve been told the dynapack calculates gearing completely differently. The dynopack doesn’t even connect a lead to your spark plug wires, so I have no idea how it even knows your RPM let alone what gear you’re in, I think they have each vehicles gear ratio’s hardcoded in…
anyways…the dynapack gave me around 133at the time, the dynojet in 4th gave me about 135, and the dyno jet in 3rd gave me 146whp or so.
Well, if that is what you are convinced of then I’m not going to try and argue with you. However I personally remian doubtful that the laws of physics cease to apply when your car graces the dyno.
when you say ‘jdm gsr’ are you talking B18C? stock specs on the B18C are 180 Hp and 128 Tq (i think the tq # may be off a bit not sure)
so, is the stock Hp and Tq not based on amt put to the wheels?
honestly im confused . with my B18C and my mods i have been told by a few people that i should be around 190-200 Hp. i do have numerous modifications and what not thou…
ok, so im just confused and am looking for a bit of clarification
The JDM GSR comes stock with 178hp. As he said about 15% is lost to the wheels, which puts him at about 153hp. With only adding intake mani and exhaust, its hard to understand a 19hp jump. I would say hes prolly putting down about 165hp.
I’m not going to say who’s wrong and who’s right, but i know i’ve dyno’d in different gears and trannies with my car and achieved different results. As scooby said, it maybe dependant on the type of dyno, or it may be dependant on other factors.
IMO, if a chasis dyno is supposed to measure power AT the wheels, then in order to be as accurate as it can for the street, shouldn’t it take gear ratios into account anyways? (unless the chasis dyno was setup to provide an accurate interpretation of only engine output only, and not include drivetrain loss)
then maybe you can explain this:
here’s my dyno, untuned 404cams, stock bottom end, back to back, 2 runs in each gear, 3rd vs. 4th, 3rd gear gave me an extra 5whp and 6ft-lbs of torque.
then explain to Eclypz that he didn’t actually see a 10whp gain when switching trannies, tell lazerplanes he also didn’t see a 13whp gain when switching to higher gear ratios.
According to AWE-Tuning:
“Gearing: a chassis dyno is susceptible to gearing bias. More power can be produced on a dyno graph by simply running the test car in a lower gear. Dyno operators should pick the trans gear that is closest to a 1:1 ratio to avoid gearing bias. This ratio is 4th gear in most cars.”
Your argument doesn’t hold any water, sorry.
OK, if you want to use a third party source, here is one from chassis dyno shop. This is the Dynojet testing procedure and not some Audi enthusiast site’s opinion:
Your vehicle can be tested in one gear, or in all of its gears. Theoretically, the results should be the same regardless of what gear is used because the increased torque in the lower gears is cancelled by the decreased speeds. In the real world, there are always differences between the gears, and the differences can be explained by a number of factors. Because of nasty things like friction and inertia, different gears always have different amounts of drag, and the greater the reduction or increase in the gearbox, the greater the drag. A low gear may fly the engine through the rpm range so quickly that it never has a chance to build up any helpful intake and exhaust resonance that those header engineers spend so much time trying to achieve. Fifth gear may be spinning your drivetrain so quickly that significant increases in gearbox drag are created. Third and fourth gears are usually favorites for finding your actual horsepower, and testing all of the gears is a useful method for discovering problems in your drivetrain. Many dynamometer operators go right for the gear that is the closest to a 1:1 ratio as it has the lowest drag in the gearbox and therefore the highest horsepower reading (usually) on a vehicle that is properly sized to be tested on this dyno.
This test procedure also offers some answers to part 2 of your question on why the numbers are better in certain gears. I can’t say this enough, the difference in gear ratios has nothing to do with engine power produced. Your car does not gain 50hp because you are in 1st gear. An engine may get some benefit through an RPM resonance at a certain RPM point, but that RPM point will exist regardless of gear, and is instead dependent on engine load. The ratios make no difference unto themselves. Only the parasitic loss of the transmission and the gears account for the difference in reading. (And possibly tuning/enviromental factors (Temp, ambient air pressure, humidity, etc changes))
My arguement is simple physics and as I said before: the rules of physics do not cease to apply. Contrary to your opinion physics tends to “hold water”.
First off, AWE tuning is a dyno operator since 1995, do you think calling them an “Audi Enthusiast’s Website” bolsters your point? They seem like a MUCH more professional company than the link you posted. It’s nice when people can avoid making dumb exagerations to try and prove their point. But anyways…
You honestly believe that I gained a consistent 5whp and 6ft-lbs of torque because my 4th gear has more “drag” than my 3rd gear? Because the other “factors” mentioned in your article don’t apply, 3rd and 4th are so similar that the points regarding drastic differences in engine speed creating “resonance” and “gearbox drag” are not applicable.
So that leaves us with gear “drag” to account for a relatively huge increase in power, nearly 4%. There’s no way.
Also explain how Eclypz, a member who has always been very straight-up about his set-up, and posted dyno’s for us to see, gained 10whp by switching from a tranny with a 1.259 3rd gear, to a 1.458. I don’t think he’s lying.
Are you going to claim that the “drag” was so much less on the new tranny that he gained 10whp? These are basically identical trannies, with different ratios, how can the drag from a transmission results in such drastic differences?
ALso I doubt any site that makes claims like this:
"Many dynamometer operators go right for the gear that is the closest to a 1:1 ratio as it has the lowest drag in the gearbox and therefore the highest horsepower reading (usually) on a vehicle that is properly sized to be tested on this dyno. "
4th gear gives you the highest readings??? Everyone knows that it a very common practice for people to dyno in 3rd gear in order to make their dyno #'s more impressive. I’ve never seen 4th gear give higher readings than 3rd, 4th gear gives you more ACCURATE readings as it’s closes to a 1:1 ratio, it does not give you higher readings. So I take the BRISTOL DYNO guys with a grain of salt.
The problem with Phsyics, when I took it, was that what you had on paper almost never actually happened in the real world. Despite how il-logical it might seem, in the real world these dyno’s are showing more HP by using trannies with higher gear ratios.
We’re telling you from experience, and real-world experience trumps theory every time.
you know what? I’m actually going to the dyno again next week to tune my new setup.
I usually do 4th gear pulls, but i’ll do a couple of 3rd gear pulls and see what happens (hopefully traction won’t be a problem in 3rd).
sweet man, I can’t wait to see your new numbers 2litre right??
I don’t know if the dyno operator will let you, but just for pure shits and giggles, you should try a 2nd gear pull, maybe we’ll see that 2nd and 4th are both less than 3rd, or maybe 2nd will be the highest…I’m curious…
Are they an audi/german car enthusiast based business website? Yes. Do they own a dyno? I dunno, sure. They do seem to have a slicker looking website. I guess that means they know more than the people writing the dyno operation procedure. How silly of me.
You quoted a 3rd party source to make a point, I quoted one to make a rebuttal. If that makes me dumb, then I guess I’m not skilled in how to defend my point.
I guess “You get higher readings in a lower gear just because damnit.” arguement is pretty compelling after all.
We’re telling you from experience, and real-world experience trumps theory every time.
I’m not denying that you got better readings from 3rd gear than you did 4th. In fact, I have no doubt in my mind you are telling the truth. 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. Up until seeing this thread I would have thought this was indisputable.
I can’t give you a concrete reason why you got better results in 3rd than you did in 4th. I wasn’t there. I can’t magically look inside your specific engines & trannies. I can’t see the sensor outputs and what the ECU was doing.But if you want to beleive that you have magic trannies that somehow add power, then fine. Your tranny has magic 3rd gear rocket boosters that are powered by pixie dust.
Physics always applies. The only thing that can alter results is an unseen variable. And that is what I’m saying is causing the difference in your results. I can’t say definatively what it is, but I’m certain it is what causes the difference in your results. Not the differring ratios.