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2005 Pontiac GTO
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Discussion Starter #1
Before I swap in the LS3 heads and intake, I'm making a couple dyno runs on Monday to see where I'm at for a baseline. Power mods are X-air intake, JBA shorty headers and catted mid-pipes, and Pypes H-box muffler and axle back. I've ordered HP Tuners so I can pull the data (they also have a wideband O2), plus make some changes to the trans programming before I go.

I'm thinking about reducing the 3-2 WOT shift point down to around 50 mph to catch more of the mid-range power/torque data. When I dyno'd my '87 Camaro several years ago, it wouldn't downshift into 2nd above 50 mph, so I was able to pull from 3200 rpm up to 6400 rpm. I read the sticky on A4 tuning, but wanted to see if this sounds reasonable. With the stock torque converter, is it safe to lock up the clutch for the run or leave it unlocked?

Thanks,

Greg
 

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Im sure if you want a consistent run, locking it in third is the proper way. Im sure the tuner has done it a million times and would be the person to ask.
 

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I'm going to get two dyno pulls on Wednesday. Report back with your numbers.
 

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Discussion Starter #5
I only needed to make 2 runs to get consistent numbers (graphs were almost identical). Made nearly 355 rwhp and 417 lb-ft of torque, but the numbers (particularly torque) are suspect as the engine RPM scale is way off, with my engine data shows him starting around 3400 rpm revving it out to 6335 rpm. Stock hp peak is at 5900 rpm, mine might be around 5500-5600. I think the dip in the middle is the TCC unlocking, I need look at the data a little more. Definitely need more PE fuel up to 4000 rpm, and timing started at 22 degrees and maxed out at 26, so that can come up a little.

Comparing the HP Tuners data to my tune, I'm having trouble translating MAF data of lb/min in the data log to "Cylinder Airmass (g)" for the main spark table in the tune. For instance, I'm hitting 40 lb/min in the MAF data but the spark table goes from .08 to 1.36 g (maybe g/sec). Injector duty cycle is 77%, we'll see if I need the LS3 injectors after the head/intake swap, but I'll also have to find the injector tables for them. Only 1 incident of knock retard taking out .5 degree of timing.

Greg
 

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.5 one incident = no problem in my book.
Little more juice down low like you said and you can really have some fun with the timing. Sweet.
 

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Discussion Starter #7
Im sure if you want a consistent run, locking it in third is the proper way. Im sure the tuner has done it a million times and would be the person to ask.
I had changed the shift programming, but he locked it in 3rd anyways and it worked well.
 

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Discussion Starter #8
I exported the dyno numbers into Excel, and reduced the torque numbers while increasing the RPM scale to approximate what the actual graph should look like. By comparing certain points on the time scale, I could correlate that to the HP Tuners data to see what the actual RPM should be. 376 lb-ft of torque is more reasonable than 417 lb-ft to the rear wheels. I kept HP the same numbers since it matched up very well with my Camaro that pulled similar (although slightly less) numbers.

Edit: removed the PDF and converted it to a JPG.
 

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Discussion Starter #10
I asked about it before they started the dyno runs, and the guy said they use the gear ratio. I figured out later that the gear ratio is fixed (at the wrong ratio) so RPM is calculated from MPH. Having the wrong gear ratio threw off the RPM scale, so I was able to correct it to get more-accurate numbers (see post #8).
 

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Yeah thats what I figured. Anytime I've ever seen the dyno "calculate" gear ratios it comes out like garbage.

With the torque being so far off I wouldn't be surprised if the shop hasn't kept up with the corrections. Most shops don't know how to do anything but WOT pulls and don't question big numbers.
 

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Discussion Starter #12
I'm probably going to find another dyno to go to. Amazingly, this place was one of the recommended shops by the local Holden FB group I'm on. On one hand, I want back-to-back comparisons at the same dyno, but since my first results were skewed, it probably doesn't matter. At this point, I'm mostly interested in the A/F ratio since I can tune the spark vs. knock retard on the street.
 

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Lots of places with good reviews but not working dynos. Doesnt surprise me at all. I went to 5 places in central Florida before finding one with working load cells. A lot of them even believed their dyno had them working but didn't. This always resulted in an argument then a refund.

Inertial dynos are "OK" but if you can't simulate the actual weight of the car and aero drag you are leaving accuracy on the table. This could result in a great tune on the dyno but not so great tune on the street.
 

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Lots of places with good reviews but not working dynos. Doesnt surprise me at all. I went to 5 places in central Florida before finding one with working load cells. A lot of them even believed their dyno had them working but didn't. This always resulted in an argument then a refund.

Inertial dynos are "OK" but if you can't simulate the actual weight of the car and aero drag you are leaving accuracy on the table. This could result in a great tune on the dyno but not so great tune on the street.
Did i ever tell you... that i wuv'd u...

(I keed)

Seriously this makes me want to get my own dyno and do crap myself.
 
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