We prefer not to do 4th gear pulls on customer cars. 4th gear pulls can be very hard on a car because of the heat generated. Our huge fan can only do so much. When you are actually moving then it's a whole different story.

 

ughh, give me a reason why it doesn't apply? you're saying there's no difference at all in volumetric efficiency between a torque multiplier of 1.343 and 1.030? like i said, 4th is just for accuracy.

i don't really care if the pulls are done in 3rd or 4th, just as long as it's documented so people comparing numbers know what's up. you can argue the difference is trivial, but it's good measure to state. dynos are all just for comparing apples to apples.

 

No, I said before that I don't know the answer and was suggesting that reading from one manufacturer manual to compare to another doesn't seem like the best way to get an answer. And it was documented... it was stated that it was a 3rd gear pull. As for arguing if it's trivial, well I don't know enough to do that but maybe it can be revisited

 

okay, my bad. that was a weak claim on my part. it was taken in the wrong order. the claim is that 4th gear is most accurate, THEN you look to a manual for why. since whatever brand measures the same thing, they all follow the same or similar limits to the system of measurement. i didn't mean to imply that 4th gear is the best or correct because the manual said so. it was more like the claim of using 4th gear is correct and for it to be said in a manual is support, albeit a weak one at that.

 

Like I said I am still new to some of this, so out of curiosity, where does the torque multiplier come from? I'm guessing it is the formula that the dyno uses to determine torque or is it related to the gear ratios of the car being tested?

 

it's just 3rd and 4th gear. i didn't feel comfortable just saying 3rd and 4th without quantifying cuz then someone is gonna end up asking "what's the dif?" anyhow, since 3rd and 4th go through the rpm band with different total times, 4th is gonna see a higher volumetric efficiency since it has more time in between valve open and close to suck in more air, thus making more power per combustion.

 

^listen to this kid...he knows his stuff

 

That's really interesting, I didn't know that. Why exactly in 4th are the valves open longer? I mean, I understand that it's probably because the valve timing is programmed like that but I don't understand the reason for being set up like that. I try to make it a point to get answers about anything I don't know and this is definately one of those. Is there a post or a resource that goes into this more?

 

www.howstuffworks.com <(/=== the best...

so say you're in 3rd with a ratio of 1.343. the rpms come up quicker because the torque from the engine is multiplied by 3rd gear, and then multiplied again by the final drive. so since the final drive is 3.722(i think), then whatever the engine is putting out is multiplied by about 5(1.323 x 3.722). although volumetric efficiency is lower, it'll pull the car faster since torque is multiplied so much.

when you switch into 4th, which is around 1.030, it comes down to about less than 4 times the engine power. it makes it a little harder for the engine to pull the car so it climbs the rpm slower. but since it is slower, then the time between valves opening and closing is lengthened allowing more air to come in, thus making more power.

so 3rd will pull with less VE because of the torque multiplied. 4th will make more power because of a better VE. all the gears are for is so that the car gets off the line, always have ample torque at certain speeds, and give the capability of a higher top speed. if you only had one gear that would be tall enough to get the car off the line, you'd only have a top speed of what, 20-30 mph?

and pulls are done in 4th because it's the closest of a 1:1(engine rpm to tranny rpm) ratio. this leaves no torque multiplication and gives an almost true power output from the engine. since the final drive is constant among all gears, it is factored out. final drive can be calculated by tire size, mph, and engine rpm if you have a 1:1 ratio.

 

^I am confused^ I am totaly down for a reflash though.

 

haha, me and Rhyzin actually had a discussion about this in PMing because I didn't want to devert the thread, if you want some better examples PM me and I'll tell you some different ways of understanding the same information. I still have to go in and work with them to do more tuning and I know some people up in Indy that would be interested in flashes for the WRX so hopefully they can work that out

 

you ain't kidding. i pulled 109whp with a lot more mods...on a dynojet.