Guys guys look :p

[DJTricky]

true that he is lol but i cant get a really accurate dyno pull until i get that tranny fixed, if i go WOT in 2nd gear it pops out into first :/ so that pull was made in first and i tryed in 2nd but it didn't work and it slips

 

[95TwinTT]

If you are doing a dyno pull in 1st gear on a 4L60e, I think you have to divide the results by the gear ratio, or 3.06 :1

The dyno's are expecting a pull in 3rd gear or 1 ro 1 ratio.

If you did pull in 2nd gear, divide by 1.65

They also generally track torque along with hp. 5200 rpm's is where they should cross.

Sounds like you are having fun though.

 

[foreverfalcon40]

JESUS F/'N CHRIST! GOOD FOR YOU!

I HAVE ALOT OF WORK AHEAD!

Hope I get close to 400 with my S/C set-up.

---------- Post added at 09:18 PM ---------- Previous post was at 09:18 PM ----------

I stop at 500hp is good for me on a DD anything after that I would get a new DD which is what I plan to do.

 

[Justin]

If you are doing a dyno pull in 1st gear on a 4L60e, I think you have to divide the results by the gear ratio, or 3.06 :1

The dyno's are expecting a pull in 3rd gear or 1 ro 1 ratio.

Transmission gear is irrelevant, as there is no such thing as a 1 to 1 ratio. You still have gearing occurring at the differential as well as the tire diameter to roller diameter. The tach reference must be established, either via induction pickup (dyno then computes hp based on roller speed relative to engine speed) or derived via tire height at xx rpm.

Dynojet operators tend to use 3rd gear because it allows a much, much slower ramp rate on an inertia dyno than 2nd gear would. On a loaded dyno, it does not make any difference. I use 3rd gear (or 4th on a manual) only when the tractive effort (torque multiplied by gearing) is high enough that it wants to climb off of the rollers.

 

[95TwinTT]

I have to say, your off the reservation on this one.

I have never heard of any serious horsepower or torque information being considered that was not acquired from a dyno running in the 1 to 1 rpm range, meaning one revolution into the trans to one revolution out.

Granted there is a gear ratio for the rear end and tire sizes to consider, but they are real time, real world scenarios that are always the norm.

I know there are other applications for solving drive-ability issues, like holding specific speeds under load, but I would like to know what dyno establishment uses first gear for a normal test.

DJ, was just having some fun but his tranny was fried, so he didn’t have 3 and 4th gear. Tell you what, lets wait until DJ gets his tranny fixed and then see if he gets the same results in 3rd gear on the same dyno. We are in the same town, so I can go sit in on the test.

That would prove that you are correct if he hits 500 hp.

 

[TIM Z]

I have to agree, ive never heard of final dyno results bieng done in 2nd gear.

 

[Justin]

I have to say, your off the reservation on this one.

I have never heard of any serious horsepower or torque information being considered that was not acquired from a dyno running in the 1 to 1 rpm range, meaning one revolution into the trans to one revolution out.

Granted there is a gear ratio for the rear end and tire sizes to consider, but they are real time, real world scenarios that are always the norm.

I know there are other applications for solving drive-ability issues, like holding specific speeds under load, but I would like to know what dyno establishment uses first gear for a normal test.

DJ, was just having some fun but his tranny was fried, so he didn’t have 3 and 4th gear. Tell you what, lets wait until DJ gets his tranny fixed and then see if he gets the same results in 3rd gear on the same dyno. We are in the same town, so I can go sit in on the test.

That would prove that you are correct if he hits 500 hp.

IF I'm so wrong, do tell me how, mathematically, don't just spout about how things are done this way because that's the way they've always been done. By that logic, we should still be sacrificing virgins to appease the Gods.

Dyno development of tunes is an integral portion of my business and I have tuned vehicles in second, third and fourth gear with comparable results.

Now, with this DynoJet dyno, chances are you will see differing numbers because of the lack of capabilities of such a simplistic unit, but it has nothing to do with the gearing of the transmission, it's entirely due to the rate of acceleration of the roller. Strap it down to a dyno dynamics or mainline, set the engine ramp rate to an equivalent value for both 2nd and 3rd gear, you'll see comparable results. Tractive effort (force applied at the tire surface) will be significantly different between the runs, but engine power will be comparable.

Here's some more reading material as well:
http://www.factorypro.com/magazine/dynojet_dyno_inflated_hp_reason.html

 

[95TwinTT]

I’m sure you do a great job of tuning in different gears, but not at wide open throttle. Maybe you could start a new fad. It would save a lot of wear and tear to not have to run the vehicle up to 130 mph. You could keep the pulls under 40 mph.

We should hit the pause button here and wait until DJ has his tranny back together. I’m sure he would be more than happy to try again.

As you say, this may be a “simplistic dyno” and may offer differing numbers. If so, it probably is also not able to set up for a first gear pull.

Either way, I’m in no hurry. We can wait until then. Keep your powder dry.

 

[Justin]

I’m sure you do a great job of tuning in different gears, but not at wide open throttle. Maybe you could start a new fad. It would save a lot of wear and tear to not have to run the vehicle up to 130 mph. You could keep the pulls under 40 mph.

We should hit the pause button here and wait until DJ has his tranny back together. I’m sure he would be more than happy to try again.

As you say, this may be a “simplistic dyno” and may offer differing numbers. If so, it probably is also not able to set up for a first gear pull.

Either way, I’m in no hurry. We can wait until then. Keep your powder dry.

Actually, I do tune in 2nd gear at WOT on all trucks under 450rwhp (due to tendency to climb off of the rollers). Running an extended cab pickup at 6000rpm in third gear is just asking to throw a driveshaft. If anything, I will often dial in part throttle from 1200-2400rpm in 3rd or fourth to reduce the tractive effort and yield a smoother operation, then lock the torque converter and command 2nd gear for wide open throttle, running from 1500rpm-redline over a 4-5 second span of time (typically). That said, I usually don't care at all about the numbers shown, I tune til the point of optimization and focus more on any percentage change than anything else.

The DynoJet can handle first gear just fine, the problem is that since the ramp rate is not controlled (the simplistic aspect), the engine will tach out in a second or less as the roller speed needed for 5000rpm is very low. Since the dynojet "measures" power based on acceleration, this shorter pull has much lower resolution than a longer, higher gear pull, which may contribute to variance, especially if the RPM reference is taken from wheel speed at a fixed reference point.

 

[Nickleahy23]

Actually, I do tune in 2nd gear at WOT on all trucks under 450rwhp (due to tendency to climb off of the rollers). Running an extended cab pickup at 6000rpm in third gear is just asking to throw a driveshaft. If anything, I will often dial in part throttle from 1200-2400rpm in 3rd or fourth to reduce the tractive effort and yield a smoother operation, then lock the torque converter and command 2nd gear for wide open throttle, running from 1500rpm-redline over a 4-5 second span of time (typically). That said, I usually don't care at all about the numbers shown, I tune til the point of optimization and focus more on any percentage change than anything else.

The DynoJet can handle first gear just fine, the problem is that since the ramp rate is not controlled (the simplistic aspect), the engine will tach out in a second or less as the roller speed needed for 5000rpm is very low. Since the dynojet "measures" power based on acceleration, this shorter pull has much lower resolution than a longer, higher gear pull, which may contribute to variance, especially if the RPM reference is taken from wheel speed at a fixed reference point.