Planet 9

I had baseline dynos done at two locations on my totally stock CS. A Quaife TBD was installed, and the car was dynoed again (no change). The Softronic SRP and software flash were installed, and the car was run for a weekend on the track at a DE using 100 octane gasoline (8 gallons 104 octane race gas at the track, plus 4 gallons 93 octane pump premium).

The car was put on the dyno again at both locations, still with 100 octane fuel.

Results, first shop:





This demonstrates why I had the dyno done at two shops. This shop does fine mechanical work and has a good reputation, but they did not impress me with their dyno work. This dyno showed no change in power with the SRP, flash and 100 octane fuel. Runs 1 and 3 were totally stock, runs 4, 5, and 6 were after TBD install. Runs 7, 8, and 9 were after SRP and DE weekend.

Results, second shop, on Dyno Dynamics rig, using their typical test protocol:





Horsepower increase was 22 hp (240 vs. 218), torque increase was 7 ft-lb (200 vs. 193). All gains were above 4000 RPM, with LOSSES in lower RPM ranges.

Results, second shop, using 6-cylinder shootout mode:





Horsepower gain was 16 hp (245 vs. 229) and max torque was unchanged at 205 ft-lb. Gains were above 5000 RPM, with LOSSES in lower ranges.

Second shop is a very precise, technical speed shop. They do not do Porsche work (no axe to grind, nothing to gain or lose). They do primarily VERY high horsepower Japanese cars, typically with forced induction and nitrous injection.

Comments:
1. This is definitely a TRACK modification. Look at the substantial improvements at 7000 RPM. You can really feel the car pulling strongly all the way to redline. This translated into better lap times, and a difference you could really feel.
2. If you drive on the street, and your enjoyment comes from racing away from stoplights, according to my results you will be SLOWER(*** SEE POST 31 FOR UPDATE ***). Make your decisions according to how you drive and what you enjoy.
3. Even if you dyno your car, you may not be able to tell if you are improving or harming its performance. There is a little sticker on every gas pump, indicating that it has been compared to a recognized standard. That is how you know you really get a gallon of gas. As far as I know, the only certification program for dynos is done by Dyno Dynamics, and that is only in Australia. The ability to compare dyno results is otherwise non-existent, as far as I can tell. Even if you are just trying to use a shop to judge relative improvement, you are at the mercy of their test operators, equipment calibration (or lack thereof) and equipment quality.
4. My car is still choked by the stock exhaust. Capristo is on the way, will install and run for a weekend at the track and then dyno again. Next DE is September, though, so don’t hold your breath…

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....its even SAFETY YELLOW! What could be more practical???

I have the IPD plenum and the Softronic tuning with a Milltek catback. I installed the plenumn, exhaust, and the tuning in that order. Several months in between each. I didn't notice a huge difference with just the plenumn, but when I installed the Milltek the car really woke up. It seemed like you needed to improve both the incoming and exiting flows at the same time. They really seem to work well together. The tuning was just gravy on top at that point.

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Nov 16, 2007 build:
'08 CS Midnight blue metallic--6 spd
Black sport seats, Delete model designation
Fire extinguisher,Floor mats, Sport steering wheel

I wouldn't worry too much about what looks like losses below 3000 rpm, dynos are notoriously inaccurate below 3000 rpm and much of it depends on how the operator puts their foot into it or not. Is this the same plenum and throttle body for the Cayman S which comes from the GT3? If so, then I'm not surprised that on a 2.7L Cayman that it simply is capable of flowing more air than the engine can handle. I also concur that once you free up the exhaust you should see some improvements across the board. Interesting that one dyno shop shows no gain and another one shows gains, just goes to show you how you can't compare dynos between shops (which people always try to do here) or between cars, etc. Good to have a record for yourself to compare future mods against, and that's really what you should use it for.

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K-Man S

Very interesting, thanks for posting. Its amazing that the Dynojet can bearly measure any difference. A 10% high reading seems to tie in with other peoples charts.

Just further discourage me from relying on dyno results.

The plenum is the one Scott at Softronic is selling. It is a Porsche part, but I do not know where it comes from.

My car is the 3.4 litre S model.

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....its even SAFETY YELLOW! What could be more practical???

Thanks VERY much for your post. Great data points to consider.

Had the opportunity to install the Capristo system, had a track day, post DE dyno with SRP and Capristo (Dyno Dynamics Shootout Mode):



Stock CS is in red, 229 HP, 205 ft# torque (max).

Blue is SRP only, no other breathing improvements, 245HP, 204 ft# torque (max), but big improvement at redline, +21 HP, +14 ft#.

Green is with Capristo added for better breathing (headers, free flow cat and exhaust) - WOW. HP goes to 266, torque to 218 ft#. Gains are solid across the whole RPM spectrum, but at redline improvement over stock is 40 HP, 42 ft# !!

Next up is probably de-snork and free flowing filter, along with Softronic's new version 3 software for free flowing exhaust systems. More news as it develops...

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....its even SAFETY YELLOW! What could be more practical???

Those are very nice gains!! But shouldn't the baseline RWHP be something like 265 or so??? 229 is more what I'd expect for a Cayman, not a Cayman S...

Now you're talking, and once you get the new file, the one written for cars with free flowing exhaust, you are likely to see even more.

Just goes to show you that the intake system is not really the weak spot. The exhaust is. Once the exhaust restriction is removed, then you will get the most from the intake modifications.

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Gator Bite
PCA Cayman Register Advocate

I assume (hope) that my car left the factory with 295 HP just like everyone elses. I am using the dyno results just to see if I am making progress, or making the car slower. By having all tests done by the same dyno, operator, using the same methods and correction factors, I am confident that I have had very nice gains in HP and torque.

Trying to compare different machine and operator results is filled with the potential for errors. It would be satisfying (but meaningless) to say that I have 340 HP. What I can say with confidence, is that I have about 37HP more than when I started....

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....its even SAFETY YELLOW! What could be more practical???

The Dynojet is the absolute standard that everyone in the industry goes by. I wouldn't rely on the other dyno system that the other shop used. It's probably some no name brand that came on the market in the past 10 years. Dynojet has been around for decades, I would trust the guy with the dynojet more than the other one. It's so simple to use, but they calibrate their software and hardware to the nth degree. Dynojet makes dynos for motorcycles as well so they have the knowledge to precisely measure horsepower no matter how small the engine is. Just because something is "cheaper" but basically does the "same" thing doesn't mean it's better or as good.

I will easily put a Mustang Dyno up against a Dynojet in terms of accuracy and capabilities, they aren't cheap either, more than $120K for a 4 wheel drive version. My local Dynojet dyno requires an inductive wire to be placed around the #1 cylinder spark plug wire, the Mustang dyno plugs directly into the OBDII port and reads directly from the car's computer, guess which one I think is more accurate?

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K-Man S

Accuracy only counts if it is repeatable when discussing dynos. Absolute numbers mean nothing except to compare changes which of course count on repeatability for accurate judgements.

If the Dynojet is so accurate, why is it indicating 229 RWHP for a car that produces 295 FWHP?????????

Ok

Couldn't help myself in editing the attached in relation to the 'ten year' comment! A comparison of 911 vs Cayman?

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GT Silver CS
1980 Honda CBX
2004 Suzuki SV1000
2006 Subaru Legacy
2002 Honda Insight

If I am reading the charts correctly, there is significant loss at the low-end of the torque curve between stock and SRP. Why is that the case?

The stock car has a flapper valve in the plenum that opens and closes at specific rpms under the control of the engine management computer. The purpose of the valve is to vary the intake system resonant frequency, so that there is a good match of the intake system resonant frequency with the engine speed over a wider range of speeds than would otherwise be possible.

So the flapper valve helps mid-range power. However, it also provides a significant blockage to the flow, and this hurts power at high rpms. Evidently, Porsche felt that the trade-off in reduced high-rpm power in exchange for better mid-range power was worthwhile.

Both the Softronic Race Plenum (SRP) and the IPD plenum eliminate this flapper valve to improve breathing at high rpm, and increase maximum power, and give up the benefit of the flapper valve for mid-range power. It's a trade that I'm happy to make, but it may not be right for everyone.

I don't think you can ever look at the bottom end of a dyno chart from any dyno and consider it 100% accurate as the way the car is spun up on the dyno can throw off readings at the low end. There is no RPM range on the graph so I don't know what the RPMs were but I usually discount anything under 3k on most dyno charts, too much variability and dependency on a specific test to make judgements from.

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K-Man S