88 Carrera dyno results! chip vs. no chip

[Steve W]

Recently, TomTurtle on this board, performed some controlled dyno tests on his immaculate 88 Carrera Clubsport prechip and post chip, and sent the results to me. The results may be of interest amongst those of the prochip vs. anti chip circle. The tests runs were performed on Dynospot Racing's Dynojet 248H in San Jose, California. In an attempt to gather the most accurate dyno results for comparision, Tom initially installed the stock chip along with the factory cat to establish a base run for the stock configuration. The only other mods to his car are a sport muffler and a cone style air intake filter, which remained on the car during all test configurations. This base run is outlined in red in the below chart. Tom then took off the cat and replaced it with a Dansk premuffler, and replaced the stock chip with a standard 911Chips performance chip for 91 octane, the same chip that Pelican sells in their catalog. The car was then redynoed and the result is displayed as the blue line in the chart. Nothing else was done to the car in between runs and all runs were performed under identical conditions.

With the stock chip, the Clubsport attained a maximum of 199 rear wheel hp at 5900 rpm. Assuming a 15% transmission loss (dividing by 0.85), this would equal 234 engine hp. After installing the premuffler and installing the performance chip, the engine developed 212 rwhp, or 249 at the engine. This works out to a difference of 15 engine hp. What is interesting to note is the 22 rwhp gain at 6200 rpm, or 26 hp at the engine. The new peak at 6200 is consistent in all dyno runs of different 3.2s with the chip, as opposed to the stock peak at 5900, which is where Porsche rates it's maximum hp as shown in the owner's manuals. Several people have actually commented how the power seems to rise endlessly out to the 6800 rpm rev limiter, as opposed to the stock chip which seems labored after 6200 rpm or so.

So where is all the power coming from? Well, a little comes from the premuffler, but the majority comes from programming the optimum air/fuel ratios in the chip, for which the factory programs way too fat in the upper rpm zones. Optimized ignition timing also helps, however timing is not increased all that much, working conservatively with 91 octane pump gas. For example, at 5000 rpm, ignition timing at full throttle in the performance chip has only been increased by 2 degrees over factory.

It is also interesting to note that the power curve of this car after chipping is only about 6-7 hp short of James Achard's 87 Carrera with 1 5/8" headers, straight out race mufflers and a chip. SSIs with a dual out sport muffler should be somewhere in between.

3.2 L Dyno Results *gasp*





tabulating the data:

[Yargk]

Nice. I've been wanting to get a chip for my BMW...

[dickster]

steve,

i respect the work you have done and the reputation you have earned on this board but i have to disagree (well, depending on what "little" means!).

i would guess that probably third/half that increase came from the cat swap. that is based on my own experience and dyno runs.

maybe i'm wrong.

its a pretty impressive result nonetheless but it would have been interesting to see like for like comparisons.

[Wavey]

With all due respect, dickster, I think you'd have to experience driving the car both ways to appreciate the difference. I did the Dansk premuffler and sport muffler together on my Carrera, and got a nice little boost. But Steve's chip definitely made a bigger difference. The dyno provides hard numbers for comparrison, and I agree, it would be good to see what a run with the original cat would yield. But the chip does more than the numbers would indicate - as has been said many times here, it really wakes the car up, from idle through full throttle. I've been running this setup for about 18 months and I'm still amazed at how the power is always right there whenever you crack the throttle. It reminds me of how our Saab Turbos feel when they're on boost, or a twin turbo RX7 I drove for a while.

That being said, I think it's also an issue of doing all 3 things together. The chip alone isn't going to provide as much as it could with the exhaust mods. But I believe the bulk of the increase comes from the chip.

Thanks for providing more hard evidence, Steve! Of course now you have created another stage for Loren to blather on about detonation and how we're all going to blow up our engines.

[Jgordon]

why not just do another test without the premuff, or with for both chips? Seems like the debate is still open for people to disagree. Identical conditions and equipment would put one side of the argument to rest.

[Wil Ferch]

$$$$ and time ....

Also, although it may be of academic interest...most people either do the 2-3 things ( chip, premuff, performance exhaust)..or none. Most don't just do a chip.

Point well taken, though, that it would lay a lot of specific unknowns to rest.

--Wil

[JeremyD]

And isn't the oem club sport chip a little more agressive than the stock 3.2 chip?

[Wavey]

It's just the same thing as the later Carrera "58" chip with a higher RPM limit. I've run them all and nothing compares to Steve's chip.

[dickster]

wavey,

appreciated, but we're talking dyno numbers here - thats what steve referred to.

thats a great increase on that dyno sheet - imho more of that is attributable to the pre-muff than steve gives credit. i'm guessing around 10hp came from the cat swap.

diont get me wrong, i'm a fan of steve's and have thought about buying one of his chips.

howabout steve donates a chip and i get it dynoed on my car with my current setup (already dynoed) and i'll take it back to the same place?!!

[89911]

Having run on the dyno twice and scheduled for at least another 2 runs, $$$$ does come into play. The dyno out here will let you do unlimited runs for $150/hour. When you start removing extremely hot pipes in a hurry, things get hazardous. I've got two runs using everything the same except for the chip and there is a 15hp difference. I also believe the more "hot rodded" your engine (3.4 higher compression, twin plugs, 20/21 cams) the more you can realize over proper fuel air ratios with the ideal settings. The difference may be closer to a 25hp increase or more from my intial overly rich runs. I'll have some hard data after some further fine tuning.

I thought the oem club sport chip only raised the rev limit. I did a dyno run with a fabspeed cat pipe and a dual out B&B and came up with 203 at the wheels. I've since put in a SW chip. I'm scheduled for a dyno run next month. The chip being the only change, this should tell what the SW chip will yield. I'll keep you all posted. The car is an'85 euro Carrera with an '87 28 pin ecu.

Wavey beat me to it.

[krichard]

Why not run the test with the exact same setup only changing the chip? I don't understand why anyone would think this is a fair comparison.

[RickM]

My guess is that 1/3 of the gain is from the premuff. I was hoping for a mere chip swap on the test. In any case, this substantiates what we've known all along.

[Crachian]

Finally some good hard data. THANKS. (by the way, what ever happened to those guys in Virginia who were planning an A-B dyno comparo)

As someone who runs the stock chip and is considering buying one from Steve, I want to know:


Is leaning out the A/F at the higher RPMs dangerous?

Why did the factory do it that way?

[BURN-BROS]

I agree with dickster, post identical engines with a chip swap.

Aaron

[Lorenfb]

"i would guess that probably third/half that increase came from the cat swap. that is based on my own experience and dyno runs." - Dickster

Dickster is right on! This test still doesn't determine the real contribution of the chip.
Again as usual, inconclusive results supported by many others' "feelings".
Hypothesizing results doesn't count!

"Also, although it may be of academic interest...most people either do the 2-3 things ( chip, premuff, performance exhaust)..or none. Most don't just do a chip." - Wil

Wil, I think the snow has finally melted in N.Y., so you should be able now
to do your dyno run as promised.

"Is leaning out the A/F at the higher RPMs dangerous?"
Why did the factory do it that way?" - Crachian

The Porsche factory didn't setup the 3.2 to run too lean or rich.
When setup properly per the factory specs, the 3.2 runs at near
to optimum air/fuel ratio.

Possible causes of an incorrect A/F ratio:
1. improperly setup air flow meter
2. bad O2 sensor
3. incorrect fuel pressure
4. bad temp sensor
5. bad WOT switch

Note: At all RPMs other than WOT, the O2 system will attempt to maintain
an A/F ratio of 14.7 even though the DME chip attempts to richen the A/F
ratio to a lower value. This assumes that the O2 system is functioning
properly. Also, during fast acceleration the O2 system has some lag which
skews the A/F ratio. Although the ideal A/F is 12.6 for max torque, values
between 11 and 15 yield little in torque changes.

[Wavey]

What did I tell you - here's Loren again with his big boner.

[Steve W]

On the cat vs. no cat debate. Guy's I didn't perform the tests and it's more than I can ask from someone to perform, especially since I didn't conduct the tests. However there's already more than sufficient data comparing a dyno run using a cat vs. removing the cat on 3.2 that's posted on my website for the past year. Take a look at the following:

These are two dyno test performed on a full stock 87 Carrera with the stock 28 pin 1267355358 chip. The first dyno run is with the cat on the car. The engine develops 186 rwhp, which corrected works out to 219 at the crank, very close to the factory quoted 217:



The owner then replaced the cat and installed an European premuffler. The peak hp has then increased to 193 rwhp, a 6 rwhp increase (7.5 flywheel), however, the gain is mostly at the peak at 6000 rpm. A portion of this gain came from a slightly leaner afr from the increased flow on top, so the true gain of a premuffler is more like 5-6 if the afrs are equal. However, if you look carefully, there is almost no gain below 5500 rpm.:



This pretty much concurs with another test on this 88 Carrera. Below are runs with a cat vs. removing the cat and installing the Dansk premuffler:




You can see about a 6 rwhp gain just at 6200, and an approximate 4 hp gain right between 3800 and 4300. Area under the curve is what matters and makes a real world difference, which is why the chip make most of the gain.

Below are tests performed by Bernd Andritzky on his U.S. spec 89 Carrera. This car is chipped on both runs. The first run displayed is with the stock cat. The second run is with a premuffer in place of the cat. Again you can see that there is very moderate gain below 5500, and approximately 5-6 hp gain after 6000 rpm:

with stock cat:




with a premuffler in place of the cat:

[Steve W]

Originally posted by Lorenfb
"
The Porsche factory didn't setup the 3.2 to run too lean or rich.
When setup properly per the factory specs, the 3.2 runs at near
to optimum air/fuel ratio.

Possible causes of an incorrect A/F ratio:
1. improperly setup air flow meter
2. bad O2 sensor
3. incorrect fuel pressure
4. bad temp sensor
5. bad WOT switch

Note: At all RPMs other than WOT, the O2 system will attempt to maintain
an A/F ratio of 14.7 even though the DME chip attempts to richen the A/F
ratio to a lower value. This assumes that the O2 system is functioning
properly. Also, during fast acceleration the O2 system has some lag which
skews the A/F ratio. Although the ideal A/F is 12.6 for max torque, values
between 11 and 15 yield little in torque changes.

Loren: you have no clue. Stick to what you do and post some hard data before you continue to post misinformation based on your assumptions.

Well, I must leave now, so I'll leave it all to you to duke it out for the rest of the day. Have fun.

[JeremyD]

may the force be with you Steve!