: Dyno question



6speeder
02-26-10, 10:56 AM
Hey all: Just bought a 2010 CTS-V and I LOVE IT. I don't know how long I can hold off on modding her. My LS7 Vette is making 572 SAE rwhp.

Anyway.... My V has the 6 speed automatic. What gear are you other auto guys using for the dyno pull as there isn't a true 1:1 gear, third is 1.15:1 and fourth is .85:1?:hmm:

cbloveday
02-26-10, 11:02 AM
4th gear. Make sure you hold down the traction control button until you see "STABILTRAK OFF".

CTSVmapper
02-26-10, 11:08 AM
Your knowledgeable dynamometer operator should know that. For dynojet, an SAE number after the dynorun info, title, name, date, type, location, average gear ratio. ie. 1.20.
In the graph, the operator can insert a listview... this contains the two colored bars that depict two lines if used (ie. Tq and HP)
and beside it have the information.
ie. DYNORUN.001: 76.64F, 25.41 In-Hg, SAE:1.20


If he/she has never changed the setting and runs 1.00 for every car, hoping 4th gear is 1:1 for example. Many if not all numbers will be off.
If its a dynojet.. call 1-800-992-3525 (Dynamometers). If its another, contact their corresponding manufacturer.

whisler151
02-26-10, 11:09 AM
Hey all: Just bought a 2010 CTS-V and I LOVE IT. I don't know how long I can hold off on modding her. My LS7 Vette is making 572 SAE rwhp.

Anyway.... My V has the 6 speed automatic. What gear are you other auto guys using for the dyno pull as there isn't a true 1:1 gear, third is 1.15:1 and fourth is .85:1?:hmm:

That is the issue CadV tried to bring up. It may account for the decrease in hp/tq in auto v. stick numbers. There is no 1:1 in the auto.

But yeah, 4th is what people are using.

GMX322V S/C
02-26-10, 08:05 PM
When my car (auto) was dynoed, they put in 3.71 for the final drive ratio (3.23 x 1.15 = 3.71) and ran it in 4th.

zero26039
02-26-10, 09:35 PM
4th gear. Make sure you hold down the traction control button until you see "STABILTRAK OFF".

I never knew about stab. off. Nice... When your playing with the car on the road whats the best way launch from a stop light? traction control on? off? stab off? sportmode? Thanks

CadV
02-27-10, 03:45 AM
My pulls have been in 4th gear.

Searched a bunch of forums on gearing and this seems to be the answer:

Gears less than 1:1 on a Dynojet = lower power
Gears higher than 1:1 on a Dynojet = higher power

Ive always considered a dyno a tuning tool and I just keep trying to make more power over my baseline.

6speeder
02-27-10, 02:45 PM
Your knowledgeable dynamometer operator should know that. For dynojet, an SAE number after the dynorun info, title, name, date, type, location, average gear ratio. ie. 1.20.
In the graph, the operator can insert a listview... this contains the two colored bars that depict two lines if used (ie. Tq and HP)
and beside it have the information.
ie. DYNORUN.001: 76.64F, 25.41 In-Hg, SAE:1.20


If he/she has never changed the setting and runs 1.00 for every car, hoping 4th gear is 1:1 for example. Many if not all numbers will be off.
If its a dynojet.. call 1-800-992-3525 (Dynamometers). If its another, contact their corresponding manufacturer.

I don't believe that is correct. The SAE:1.20 number is the correction factor from actual rwhp to SAE and is based on the density altitude. Our correctin factor based on the local DA is usually 1.21 to 1.23 in summer because the dyno altitude is 5,500 feet and it does get warm here.

gnxs
02-28-10, 09:52 AM
Ive always considered a dyno a tuning tool and I just keep trying to make more power over my baseline.
+1. :thumbsup:

All I want to see is how my numbers have changed (improved hopefully) after adding various modifications and if my A/F is where I need it to be (although I usually datalog with my wideband for that anyway).