nycebo

So I'm reading along on 6speedonline and I finally read a thread that contains before and after charts of a dyno pre- and post- modifications to the car (exhaust, chip, etc). Here's the link . The car definitely looks to have gained more horsepower and more torque, though it might be a bit at the expense of a little low end power (below 4500 rpm).

Here's my question: Why do the post-mod charts look so volatile compared to the smoothness of the pre-chip car? Isn't this a bit worrisome to some? Indeed, I have been very interested in adding an intake, headers and adding a chip, but this has me a bit flummoxed (although frankly, I think it's only the chip that is responsible for this behavior). Any thoughts?

P.S. - Included the charts below for your review.

kilrgt

For 6 HP, I wouldnt even get out of bed.....Not worth it IMHO.

lowside67

What I want to know is why on earth does a stock 996 dyno 228hp? Is it possible our drivetrains kill 23% of the power on the 2wd model? That seems a bit high when in most cars you can attribute 15% to drivetrain loss and I like to consider our 911s more well engineered, not less.

TT Surgeon

What's worse, the 228 hp is WITH mods, the 'after dyno' is after just a chip. Think I'll pass on those fancy exhaust parts, stick with fabspeed.

Russ Murphy

>>>>Here's my question: Why do the post-mod charts look so volatile compared to the smoothness of the pre-chip car? Isn't this a bit worrisome to some? Indeed, I have been very interested in adding an intake, headers and adding a chip, but this has me a bit flummoxed (although frankly, I think it's only the chip that is responsible for this behavior). Any thoughts?<<<<

The filtering value is changed on the second chart. Just by looking at the curves it's apparent that the "smoothing" or filtering is different. The first chart would be similar looking most likely if you had the filtering set the same.

It's very hard to increase the peak numbers without some drivability sacrifice. It's not like Porsche engineers don't know what they're doing. About all the headroom for improvement aftermarket tuners have comes from the safety margin built into the Porsche maps for octane variability and engine longevity (I know, I know....85 non RMS...yada, yada, yada).

sharkster

Shrug I'm not sure they know exactly what they're doing... maybe they didn't load it correctly. I've never seen a stock 996 dyno that low to begin with stock?

nycebo

Maybe he changed the filtering in order to get higher peak values. It just seems odd to me that modding the chip offers such marginal benefits to stock. I think freer flowing exhaust (header and muffler) and intake mods on a fuel injected car doesn't really require much else, eh?

As for the lower rear wheel horsepower, the deficit to horsepower at the crank could be due to anything including drivetrain, the dyno itself, lack of optimal airflow to the intake, etc.

nycebo

Sharky, that's not even stock...that's with exhaust and headers and intake, but less the chip.

sharkster

Yeps that's what I was saying.. even stock cars don't dyno that low... Around 240 or so is where they should be stock at worst.

sharkster

Here's a a few 3.6L plots...

http://www.giacusa.com/36_dyno.php?mpid=94

sharkster

And here's a 3.4L
http://www.evoms.com/996%20tuning.htm#996

tinymcoupe

Mustang dyno are known to result lower numbers? This what I hear and don't know if this true but I am throwing it out there.

evo_333

those numbers are really low, something must be off. I've seen bone stock dyno tests at 250

teflon_jones

While the numbers do seem low for the pre-flash car, every 996 has different HP. I've seen 30HP differences in dynos on more than a few of the "same" cars. I don't know how many miles are on this car either. Do they have the engine cover open too? How hot was it that day? There are a lot of questions/answers that could explain why the numbers are so low.

The important part is the very small difference between the two graphs.

evolvedaz

OK here we go fellas. The two different graphs were done here in house at VividRacing. We have an AWD Mustang dyno. Now for those of you that know anything about dynos you will know that Mustangs read lower than a dynojet. Now for the gentlemen that posted the graph from EVOMS, notic what dyno that is on. Yes you are correct, a dynojet. Now our dyno reads low. All dynos are different, none read the same. It is impossible for every one to be the same. I am not going to get into the differences on the 2 dynos but the differences are big and that is why the numbers differ so much. Now on to the smoothing. The first test was ORIGINALLY done using different mustang software than what we are currently and i used a higher smoothing factor but since the original I have stopped using such a high smoothing factor so that i can see exactly how a motor is performing through out the entire power band. We figure that it is better to test real world products and show real world results. The chip made a big difference in the total drivablity of the car, I do recommend it. So if you have any more questions about the dyno numbers or smoothing please feel free to PM me and I can answer any more questions.