I saw this other post asking the same quesiton.
Other Post asking the same question

Someone was claiming higher numbers come about when the pulls are using 3rd gear. Does this make sense to you? Why would that be?

I think Giles uses 4th gear pulls. Can you explain why you chose that over 3rd gear? I know on a relative basis it doesn't make any difference as long as you use the same gear each time.

I know you guys ponder every angle and I was just trying to understand the thinking.

 

Hmm and I thought the S was supposed to be dyno'd in 3rd, but then again I;m not 100% sure. Either way I'm sure these guys know what they're doing.

Now that you've got a pretty sweet setup are you gonna splurge for gears??

 

It's all about losses in the gearbox and rate of acceleration. Each gear does have very slight difference in loss but the amount is so small it's silly. However, on a roller dyno it is a bigger deal if you think about it. The car accelerates quicker in 1st gear than 4th gear on the road. The same is true on a roller dyno which causes you to fly by the RPM points before the engine has had a chance to settle and generate the power at that RPM. On a roller dyno you would get lower numbers in 1st, higher in 2nd etc. etc. however due to the very slow acceleration time in higher gears it can produce enormous strain on the engine. So ... 3rd or 4th gear are your best choices for a roller dyno.

Now, with a Dynapack it is completely different. You set how long you want the dyno to take during the acceleration and it is completely independent of gear. So with the dynapack it does not matter at all what gear you use. I've proved this to myself several times with my S doing pulls in different gears.

 

Got it. So it depends on roller based vs. Dynapack. The more I learn about Dynapack the more I wonder why more dyno businesses don't go with Dynapack. It seems to do everything but an oil change auto-magically.

Thanks

 

Cost ... a similar power capable Dynapack is 3 to 4 times the cost of the DynoJet. There is a lot of 'tradition' with the roller style dyno's. OEM groups always use a setup similar to the dynapack.

 

I'm thinking test pipe, probably not gears at this point ... that is if Scott can find me / make me one that doesn't take the wonderful, low, throaty, sounds of my Comptech Exhaust that I love and make it sound like a "ricey", whiney, little tin can.

I considered the 4.56 but since its a daily driver and I use 6th gear for good distances on the interstate, I've not gotten to the point yet where I willing to put up with the recurring higher RPM noise especially with the hardtop on right now.

 

If you remove the cat it will just get louder, quite a bit louder actually. Same sound, just more of it

 

With the s2000 the difference between a 3rd gear pull and a 4th gear pull is so small that it won't matter. I've had the dynojet operator do this on different occassions and both times it was litterally a 2hp difference. That can be attributed to normal dyno discrepencies.

 

I stole part of your sig to add to my quotes