pulley kit and other basic mods comparison

[nikitopo]

Originally Posted by ichitaka05

What I meant was do it on different thread. It's not forbidden topic or anything, but if you wanna go into it, please make a new thread. I can promise you, it'll get pretty ugly... BUT don't take my word for it. Who knows, maybe 86/BRZ owners are more mature and might not go down ugly road.

Ok, challenge accepted. Let's see if the 86/BRZ owners are more mature.


I created a new topic and I am requesting members w/o a pulley kit or a modified flywheel to post timings of a 2nd gear pull. My engine related mods are a pulley kit, a lightweight flywheel, a bigger tb, a '+17 MT OEM exhaust manifold and a basic Cossy stage 1.0 tune (i.e. a bit better AFRs and CAM timings). Some members said in the past that I should not see much or any improvements at all and I throw away my money, so let's compare. It is not the best possible comparison as I don't have timings only with the pulley kit change, but it is better than nothing.

Members should keep in mind that my final drive ratio is 3.727 and it pulls slower on same gear. If they have a 4.1 or a 4.3 fd should do a percentage correction because of the difference. Additionally, the comparison should be kept as fair as possible with a flat road logging and at least a 3/4 fuel tank.


I am doing the start with two times. Members with a shorter fd cannot go up to 102 km/h, so I am posting also a smaller log:




I'm attaching also the Ecutek log file just to not be blamed that I changed the results.

[CSG Mike]

Do a pull with and without. I don't see the debate here.

[Subsonic]

Originally Posted by nikitopo

It is not the best possible comparison as I don't have timings only with the pulley kit change, but it is better than nothing.

I quite disagree, this is much, much worse than nothing, if only for the following mod list:

Originally Posted by nikitopo

pulley kit, a lightweight flywheel, a bigger tb, a '+17 MT OEM exhaust manifold and a basic Cossy stage 1.0 tune (i.e. a bit better AFRs and CAM timings).

Members should keep in mind that my final drive ratio is 3.727

Most agree that a pulley change will only offer a very slight benefit to acceleration times, so small that it would be lost in the noise when comparing even perfectly equivalent cars on the same day on the same road, let alone a totally different car with different spec on a different road, altitude, tyre type wheel size etc ect. Oh my god. Diff ratio too? Jeezus.

If you really want to prove the benefit of your mods you need to conduct a proper test by controlling as many variables as possible. Only then will we still sling shit at you for spending money on your car for a 0.01s to 100 time improvement to the determent of your engine. It's your call though.

I still can't quite believe I have to explain this. Are you a troll?

[Tcoat]

There are no baseline measurements. Nothing that breaks out what has caused what or even if anything was gained at all from each component. Nothing at all to tell us if any of these changes are improving or fighting against each other. Totally meaningless "data" gathered in an uncontrolled and unrepeatable manner.

[gtengr]

The water pump probably consumes ~5 hp or less, and same for the alternator (I assumed 130A, 14.4V, 50% efficiency). I assume you don't want to underdrive those accessories more than around 25% before you risk them not being able to do their job, resulting in max available gains of 2-3 hp.

[Tcoat]

Originally Posted by gtengr

The water pump probably consumes ~5 hp or less, and same for the alternator (I assumed 130A, 14.4V, 50% efficiency). I assume you don't want to underdrive those accessories more than around 25% before you risk them not being able to do their job, resulting in max available gains of 2-3 hp.

The weight of the pulley would not affect the accessories it drives. That would be impacted by a larger diameter or slower engine speed.
If we consider that it somehow did then the 8 ounce weight reduction would really only come into play when the car is out of gear and standing still. Even then it is almost so minor as to be safely deemed insignificant. As soon as the car is put into gear and the engine has to move the drive train and tires against the road the weight of a pulley drops to such a teeny, tiny (the actual technical term) percentage of the mass being rotated that it is only measurable by the maths involved. There is no instrument that could possibly measure that small an impact on the whole drive train and any "it feels faster" statements are just expectation bias.

[Lantanafrs2]

Oh my God

[norcalpb]

What pulley kit? Are we talking all 3?

[gtengr]

Originally Posted by Tcoat

The weight of the pulley would not affect the accessories it drives. That would be impacted by a larger diameter or slower engine speed.
If we consider that it somehow did then the 8 ounce weight reduction would really only come into play when the car is out of gear and standing still. Even then it is almost so minor as to be safely deemed insignificant. As soon as the car is put into gear and the engine has to move the drive train and tires against the road the weight of a pulley drops to such a teeny, tiny (the actual technical term) percentage of the mass being rotated that it is only measurable by the maths involved. There is no instrument that could possibly measure that small an impact on the whole drive train and any "it feels faster" statements are just expectation bias.

I didn't say anything about weight. It's implicit in the term "underdrive" that the pulley rpm is being lowered, which can only be done by changing pulley diameter.

[Tcoat]

Originally Posted by gtengr

I didn't say anything about weight. It's implicit in the term "underdrive" that the pulley rpm is being lowered, which can only be done by changing pulley diameter.

Oh OK. The debate is lightweight pulleys so no sure where the size came in.

[gtengr]

Nah. The debate is the effect of pulleys on acceleration. You were the first person to mention pulley weight, and you did it after my post.

[nikitopo]

I've done this logging twice. The difference was in the range of .01 sec. If the road is level why to have a difference? Diff ratio will give an advantage to the other car, but we know how it works. It is a torque multiplier. If you 're trying to ridiculate the comparison, then you should ridiculate all the 40-60, 60-80 etc. results that manufacturers provide for their cars. It is not a car launch comparison that is also dependent with the way you launch. It is an acceleration test on rolling speed and with a fixed gear.

We are not trying to prove here how much the gains are, but if there are in general any gains at all. If not even a single person doesn't want to post a result (even for a stock car), then it means that you are just hiding behind your finger and for me the topic is closed. From now on I'll discuss if someone post times. Anyone?

[Tcoat]

Originally Posted by gtengr

Nah. The debate is the effect of pulleys on acceleration. You were the first person to mention pulley weight, and you did it after my post.

OK if you say so.

[Tcoat]

Originally Posted by nikitopo

I've done this logging twice. The difference was in the range of .01 sec. If the road is level why to have a difference? Diff ratio will give an advantage to the other car, but we know how it works. It is a torque multiplier. If you 're trying to ridiculate the comparison, then you should ridiculate all the 40-60, 60-80 etc. results that manufacturers provide for their cars. It is not a car launch comparison that is also dependent with the way you launch. It is an acceleration test on rolling speed and with a fixed gear.

We are not trying to prove here how much the gains are, but if there are in general any gains at all. If not even a single person doesn't want to post a result (even for a stock car), then it means that you are just hiding behind your finger and for me the topic is closed. From now on I'll discuss if someone post times. Anyone?

You understand the concept of a controlled test right? Do you have the calibration records for your foot? Did you drive exactly the same track on the stretch of road? Are two pulls really enough to get an average even if your foot was calibrated?
How can we compare other people's data when there is zero commonality between the tests? The whole idea is laughable and prov s nothing. You are the one stating the pulley gives you better acceleration and the onus of proof is on you not everybody else. Show us some data from your car with and without it and forget what everybody else's car can do.