stage 2 upgrade ozz

[elff]

There is a post with 4 Dyno charts from 4 GMPP tuned cars on the same day on the same dyno.
2 cars had Dejon IC Pipes, CAI and Aftermarket Exhaust
2 cars had stock IC pipes and airbox

All 4 cars pulled within 2hp of each other and real close on ft-lbs
Avg at wheel
264.5 hp
323 ft-lbs

Considering the car is rated at 260 hp and 260 ft-lbs at the crank from the factory in stock form
GM's claim for your performance upgrade seems to be dead on with 290 hp at the crank

It also showed that the tune isn't customized for the aftermarket parts and pretty much ignores them.

On the same day, we did see any Automatic have trouble getting an accurate Dyno and their numbers yielded almost identical results to the above post.

Side by Side spirited driving next to that same Automatic showed that it had almost the exact same power, so while I don't know the exact reasons as to why, I fully believe the Dyno was not displaying accurate numbers for the Auto

[Steve244]

Perhaps the dyno software is throwing out results it detects were not achieved while in 4th gear (close to 1:1).

Since downshifting can't be eliminated on an auto, maybe the curve represents the transmission characteristics as much or more as the engine output. If peak power is achieved in 3rd, and it downshifts at the same axle speed and torque as before the tune, the dyno may be ignoring (or unable) to measure the true peak ether before or after the tune. Or were they able to overcome downshifting? (edit) Even in 4th, without locking out the torque converter I think there are too many variables to get a meaningful peak output figure.

I'm curious enough to drop $50 for a power test locally. We'll see. Too bad I have no "before picture."

(edit) On second thought I think I'll skip the dyno; I don't think it's easy to get meaningful results. This page seems to indicate dyno'ing an automatic transmission equipped car is more an art than a science:

For cars equipped with automatic transmissions or special torque converters, some finessing is required.

[Flash's Owner]

Always ALWAYS be cautious about trusting any dyno information on an automatic trans car.

[I1ULUZ]

Originally Posted by Flash's Owner Always ALWAYS be cautious about trusting any dyno information on an automatic trans car.

Care to explain your post in more detail? What exactly do you look for when you think the dyno is not displaying the true output of an engine and drivetrain loss?

What would a high rpm stall loose converter look like on a graph? Or a tight converter like in a diesel truck? How would a auto vs manual compare in another sports car lets say a C6? Would the graphs be very different or really close in shape?

Have you ever had one of your vehicles on a chassis dyno? Have you dyno'd an auto Solstice? If so please share your graph. Even make a comment about what is right/wrong with my graph.

I look forward to learning from an expert GM Engineer. You do work in the Powertrain Division right?

[Steve244]

I think this is part of the answer (which is about what I intuited above. Pretty good for a software engineer):

ABOUT DYNAMOMETER READINGS AND HIGH STALL TORQUE CONVERTERS There is a misconception and a lot of misinformation about the poor vehicle performance numbers that are generated by testing a car with a high stall torque converter on a dynamometer. Most people that are not familiar with how a torque converter operates will automatically think that the torque converter is inefficient. This is totally false and the following facts are why you should not believe the dynamometer numbers while using an unlocked high stall torque converter. All late model dynamometers have a software program that commands the loading and speed of the vehicle over a certain period of time while making a test pull. The software used in these dynamometers is setup to be used with a locked 1:1 connection between the engine and the rear wheels, such as using a standard shift transmission in 3rd gear or when an automatic transmission has the torque converter clutch locked. When an unlocked high stall torque converter is used to make the pull and the dynamometer software has not been changed to allow for the fluid coupling differences the dynamometer readings will all be bogus. For instance, the low rpm torque readings will be high due to the torque multiplication of the torque converter being run in partial stall. Likewise, the high rpm torque readings will be low due to the long period of time the dynamometer takes to allow the torque converter to transition from partial torque multiplication to a hydraulic locked condition. The only cure for this phenomenon is to rewrite the dynamometer software to prevent this from happening. Torque converters with a low STR or low stall are not as adversely affected by this phenomenon. The high rpm transition problems never occur when the vehicle is being driven or raced normally. Therefore, worrying about what the dynamometer numbers are is a total waste of time. If your dynamometer operator refuses to alter the software to give correct readings then the only things you can do is (1.) lock the torque converter clutch and do the testing, (2.) use the readings you get with an unlocked torque converter as a baseline and continue to tune the car like normal until you get the best numbers remembering these are just numbers and not the actual horsepower and torque or (3.) use a dynamometer shop that gives you the service you deserve for your hard earned money. The only really true test of the performance of a vehicle is to take it to the track and see what ET and MPH the car will run."

source

[I1ULUZ]

That might be true on something like a Mustang brand dyno that use an eddy brake to control the load on the engine. The dyno I was on was not being used in that fashion. It's used when a tuner is trying to do the whole spark and fuel maps on the dyno vice on the street.

And IF you had ever seen a high stall converter car dynograph you will remember it. It starts off very high on the left and falls off quickly to the right. Would not be low like mine. Have you ever driven a car with a high stall? Check out Chevy | Camaro | Firebird Reviews, Performance Parts, Modifications - LS1Tech.com for graphs of cars with a high stall converter. Start off looking at the 11 sec or quicker cars, those are the ones that are running mid to high stall speed converters.

Due to CAFE standards you won't see a loose (high stall) stock converter in ANY car. "Torque converters with a low STR or low stall are not as adversely affected by this phenomenon." So what was the point of your post again?

I bet you stayed at a Holiday Express last night, good job on using Google So I take it you have never been to a dyno much less had a car on one?

[Steve244]

hahahha you got me.

According to your own posts (that I've been following carefully) they haven't sussed being able to keep it in 4th or locking the torque converter. A nice smooth curve like that doesn't indicate any shifting or torque slippage. What gives? Must be the software.

Looking at the local dyno experts website, they appear to be two guys with a dyno. Not engineers of the soft or hard kind. It seems they allow anyone to use their machine for $50 and they'll fiddle things to make it work with an automatic. I'm sure your guy is much more knowledgeable.

[I1ULUZ]

Originally Posted by Steve244 hahahha you got me. According to your own posts (that I've been following carefully) they haven't sussed being able to keep it in 4th or locking the torque converter. A nice smooth curve like that doesn't indicate any shifting or torque slippage. What gives? Must be the software. Looking at the local dyno experts website, they appear to be two guys with a dyno. Not engineers of the soft or hard kind. It seems they allow anyone to use their machine for $50 and they'll fiddle things to make it work with an automatic. I'm sure your guy is much more knowledgeable.

Go spend the $50 (not bad for 3 or more pulls most places charge more some double that) and jump on the dyno and let us know what they say is happening from your wife's car readings compared to what GM says the kit should be producing. I am sure they measure AFR and boost. That would show if it's just my car or all auto's. You don't just use one box to test your software on before you say it's good to release to everyone. Greater the number of samples, better the data is when you are done. Also ask them how much rwhp difference there is between doing a pull in 3rd and 4th. Even have them do it to see the results. Maybe they know how to keep it in 4th where my guy does not. It's sad that VW gave our old 2005.5 TDI Jetta the ability to be shifted manually where this "sports" car can't. I bet when this trans was in the BMW's they gave the driver a way to command what gear to use.

What brand/model of dyno do they have? If it's a Mustang dyno save your money, it's really a waste of time and money. Also have them use SAE correction factor and smoothing on 0. Or copy the data from the pulls and shoot it to me so I can view it on DynoJet's software so I can compare it directly with my pulls. Maybe something will show up, my AFR might be leaner.

I know you are not the only one watching my posts about GMPP Kit dyno results and what GM is going to say.

[I1ULUZ]

Steve

Your post got me thinking and looking around, I noticed my graph compared to a Cobalt SS graph with an aftermarket tune on it, that my engine takes much longer to richen up than the Cobalt. The PCM does control the HPFP on our engines, so it could be a software error. And I have been told via a PM that GM changed something between the early 07's and 08 MY. Maybe it didn't get changed in the auto GMPP tune.

I hope my new Dashhawk will show a low high pressure fuel pressure reading.

Now I am going to look around for other manual graphs to see when the PCM commands a richer AFR.

I doubt if this is a hardware issue otherwise it would set a DTC.