does it matter what gear i dyno in. i have already done it i only got 97.5 i done it in 3rd gear. is this right or ami doing something wrong. they also couldnt get a good tach sig so they ran it off of wheel speed

What transmission? 4th gear is usually the closest to 1:1 which is what you want.



Tinkles

2003 Cavalier 1SV
Bagged and Blown

You have two LN2 cavs in your profile with nothing but bolt ons. That sounds about right.


2010 Honda Fit LX

How did they not get a good tach signal?'

But yeah, 4th gear is usually the best for dynoing. But you'll hit the speed limiter so you won't see numbers all the way to redline. (no biggie with that lightly modded of a car).

3rd gear usually throws it off a tad, but you consider less wear on the engine because you're not holding it at WOT for so long.





www.gmscf.com

They need to test in 4th gear on a manual tranny and the tach signal can be taken as the did, but they need to set the cylinder count to two cylinder, since each coil feed two cylinders and fires twice as often. An experienced dyno shop should know this, as many GM vehicles came with the DIS ignitions.

May car has been run in 3rd gear for all of my pulls and I have been to 2 different dyno shops. Maybe for fun when I get on the dyno in a few weeks again I will run the car through 4th to see if it changes anything.

It all depends autos are a little harder to lock in and the dyno reading can be sporadic but every auto cavy I've ever seen dynoed has never had a problem. And what gear for the transmission all depends how many gears you have. You almost always want to dyno in the gear closest to overdrive because like tinkles said you want that 1:1 ratio.

These are the differnt transmission ratios for the closest gear to a 1:1 ratio.

Isuzu MK7 MJ1: 4th gear is 1.03:1 on the LN2s and 0.93:1 on the LD9s
3Sp/TH125C/3T40: 3rd gear (D) is 1:1
4sp/4T40E: 3rd gear (3) is 1:1
Getrag F23-M86: 4th Gear is 0.98:1

So I think my car has an F23, its a 2000 LD9. Wondering how/what changes would occur with doing dyno pulls in 3rd rather than 4th?

I did 2 pulls in 3rd and 1 in 4th at the bash. First pull in third was the highest, second pull in third and the pull in 4th were both real close to each other.



Paying someone to install parts and bragging about it being fast, is like watching someone bang your wife and being proud to raise their kids.

thanks for the info ill try 4th gear next time. i have i think just about every bolt on i think what else cani do to get some more out of this thing besides p&p the head i dont want to tear it dow quite yet

As I tell everyone, get a spare cam and head (whole motor might be easier/cheaper) P&P the head at your own pace and get the cam reground. Call you favorite cam grinder and have them spec a profile for you. Regrinds typically don't cost but about $150 (unless you get JBPs, which is just an overpriced regrind!) Surface the head and get the Cometic 0.030" head gasket to help up the compression. You'll need to do the adjustable roller rocker arm conversion to properly adjust the valve train. Finally get it tuned from a knowledgeable tuner, preferably with a dyno.