Which gear to dyno at?

Reply Subscribe

Thread Tools

Search this Thread

Jan 4, 2006 | 04:34 PM

#21

DayBlueZ

Registered User

iTrader: (13)

Joined: Apr 2005

Posts: 1,949

Likes: 0

From: B'ham Al

The only effect the 3.5 has is on MPH. I lost about 4 in 3rd. 3rd is where you should dyno.

Jan 4, 2006 | 05:16 PM

#22

Cannysage

New Member

iTrader: (29)

Joined: Dec 2004

Posts: 7,374

Likes: 1

From: SO_CAL

most people dyno at 4th.

Jan 4, 2006 | 05:39 PM

#23

Mr_pharmD

Registered User

iTrader: (48)

Joined: Sep 2005

Posts: 1,397

Likes: 1

From: KaLi

Quote:

Originally Posted by DayBlueZ

The only effect the 3.5 has is on MPH. I lost about 4 in 3rd. 3rd is where you should dyno.

Hey bro, did u notice any rasp with your mod combination? I have almost the exact mods except I went with the kinetix HF cat and I'm getting some rasp around 2-3K rpm. Do u know if I take out the aftermarket y pipe and replace it with stock one that the rasp should go away? Also does the y pipe make a big difference bc I'm quite fond of the pw I have now and I'm afraid replacing it back with stock y pipe will feel slower

Jan 4, 2006 | 06:54 PM

#24

trey.hutcheson

Registered User

iTrader: (2)

Joined: Jun 2005

Posts: 244

Likes: 0

From: Birmingham, Alabama

Quote:

Originally Posted by Alberto

What!? In what gear? Im assuming you mean 5th because thats what we are discussing. 287hp model Z's top out at 142mph in 5th at fuel cut with stock redline. Now add 500rpm's higher with the same gearing and your trying to tell us that they can hit 159mph in 5th? With only 500rpm's more? I highly doubt it. Seeing as how 5th at 7100rpm on my car was around 150....

I can't speak for DaveO, but the speed limiter for the g sedans, even the 05 6MT's (revups), is 145. I've dyno'd in 5th and was unable to reach redline due to the speed limiter.

Jan 4, 2006 | 07:36 PM

#25

Alberto

Cranky FI Owner

iTrader: (14)

Joined: Mar 2003

Posts: 34,715

Likes: 8

From: DMV

Quote:

Originally Posted by trey.hutcheson

I can't speak for DaveO, but the speed limiter for the g sedans, even the 05 6MT's (revups), is 145. I've dyno'd in 5th and was unable to reach redline due to the speed limiter.

Ah ic that would make sense, I didnt understand that. So the revups have a lower speed limiter? Thats odd....

Jan 4, 2006 | 07:44 PM

#26

bigbri

Registered User

Joined: Apr 2005

Posts: 2,059

Likes: 0

From: CALI

You have to dyno in 5th to get your true whp dyno numbers a lot of mags dyno in 4th or 3rd to show higher numbers....if I dynoed in 3rd I'd have 700 whp...

Jan 4, 2006 | 08:25 PM

#27

DaveO

Sponsor

Joined: Jun 2003

Posts: 268

Likes: 0

From: SoKal Desert

Quote:

Originally Posted by GAaaAR

So your saying my AT should dyno at 3rd gear?? I kno readings are higher at 3rd gear, but would it be less accurate since its not a 1:1 ratio?? Also would my 3.5 differential affect the readings?? and maybe i dont have a 1:1 ratio anymore at 4th gear???

GaaAR,

The 3.5:1 rear gearing changes the overall gear ratio but not the AT's internal ratios. Unless it's locked up, the torque converter varies the overall gear ratio regardless of the "gear" (or clutch pack) that's engaged. I've witnessed around 200 350Zs/G35s dyno and base my recommendations and opinions on these observations.

DaveO
G35 Editor
Sport Z Magazine

Jan 5, 2006 | 05:53 AM

#28

trey.hutcheson

Registered User

iTrader: (2)

Joined: Jun 2005

Posts: 244

Likes: 0

From: Birmingham, Alabama

Quote:

Originally Posted by Alberto

Ah ic that would make sense, I didnt understand that. So the revups have a lower speed limiter? Thats odd....

It appears that the sedan is the only model limited to 145. The coupe reaches 155, as proven by klumzee.

I assume the limiter is *not* 145 for the z.

Jan 5, 2006 | 05:56 AM

#29

trey.hutcheson

Registered User

iTrader: (2)

Joined: Jun 2005

Posts: 244

Likes: 0

From: Birmingham, Alabama

Quote:

Originally Posted by bigbri

You have to dyno in 5th to get your true whp dyno numbers a lot of mags dyno in 4th or 3rd to show higher numbers....if I dynoed in 3rd I'd have 700 whp...

That's a blanket statement and not necessarily true. Dynojet dynos, for example, automatically correct measured torque for gear ratios. It achieves these corrections by comparing engine revs against *drum* revs; meaning it is actually calculating a "to the drum" gear ratio. This way, you could conceivibly dyno in any gear on a dynojet and be within one to two percent accurate of your 1:1 gear.

I have had my car dynod on a single dyno in 3rd, 4th, and 5th. I have seen variances of up to 8 to 10 hp/torque, but that's very small compared to the variances of the torque multiplier effect of the gears.