Jim Michaels

The Tech Q&A on the "air restrictor" plate removal was in the July Pano (page 61). Scott Slauson (PCA Boxster/Cayman tech specialist) responded that the plate is a baffle rather than a restrictor, and that he got the same dyno hp with the plate out that he got with it in; with both the stock 3.4 Cayman motor and a 3.8 transplant motor. However, several who have removed the plate have reported very noticeable butt dyno performance/power gains, in addition to an enhanced induction sound. Only Ken Smiley (K-Man S on caymanclub.net) has posted before-after dyno numbers, and he reported a 13 rwhp gain from plate removal; that's a 4.4% hp gain (anyone who can feel that difference has a very precise and sensitive butt dyno). There's little need to continue to argue this point, however. True believers can enjoy the free hp gain they feel, while non-believers can just leave their plates in place. Apparently neither side can be won over by argument, or by empirical evidence that's contrary to their beliefs. I've seen no evidence to back the claim that the plate actually restricts the air flow through the air guide; not even for the 3.8 engine transplant.

Chris C.

Thanks Jim for the additional clarity! BTW, we were just engaging in collegial discussion here

I'd be interested if I knew it generated "only" the 13 hp!

Jim Michaels

Chris: I agree re the civility of the discussion here, and I appreciate that. I'd remove the plate in a flash too, if I thought it would produce even half that much hp, even if my numb butt couldn't feel it.

Tahoe M3

Here's a follow-up question. Were the dynos done with a fan blowing into the intake? Strange question, perhaps, but I think it makes a lot of difference. I think this mod has a lot more potential to make a difference on a moving car than it does on a stationary one.

When the car is sitting there, the intake tube is pressurized 1 atm, as it should be, whether the restrictor plate is there or not. On the other hand, if the car is moving, there is a potential for a "ram-air" effect of pressurized air moving directly into the intake (or being deflected away if the restrictor plate is present). Could make a huge difference on dyno gains or lack thereof.

jrok

As a side note to this discussion I spoke with John Lewis (from the Porsche Driving Experience) last month at the Kentucky Region PCA driving event at Putnam Park. He was checking out my car because he was amazed that I had stuffed 305/30-18 Hoosier GAC's on 11" rims in the back of my car.

As we were talking about my other mods he noticed the silver mesh I installed behind my intake grill to catch stuff and we talked about the restrictor plate/noise baffle/rain guard/cigarette catcher mod for a few minutes.

He told me that to increase the performance of removing that plate that I should also intall the Cayman grills because they had shown to be 15-20% more effective at funneling air into the intake space because of thier vertical profile and overall shape. He said that as the air travels along the side of the car the vertical fins actually divert some air into the intake space in sort of a crude ram-air effect.

I have been busy driving in NASA at Putnam Park, Mid-Ohio and Autobahn the last few weeks but this is definitely on my to do soon list.

As far as the removal of the grill, which is a major pain in the fingers, look up at the bottom of the horizontal slats with flashlight to see how the locking clips go together, then you'll understand how to spread them down and open to get it to pop off. I also used a shop rag behind the grill to hold the grill away from the car so it would not re-clip while I was working my way down.

hope this helps. good luck with it.

[EDIT] - while typing out this post the one above about ram-air was posted which was spot on about moving air while driving according to Mr. Lewis.
________________
jrok
2005 987 Boxster S
1996 993 C2 Cabriolet *** FOR SALE ***
*** Black/Black/Cashmere, only 18,000 miles ***
*** Fabspeed mufflers, Cat by-pass, Tips, Fabspeed open side intake, BMC ***
*** Real Factory Euro RS front splitters, WM Front strut tower brace, Alu-pedals ***
*** Still have ALL original factory parts from new ***
click here for a 993 picture. PM me if interested -- (I need a racecar)

Jim Michaels

Good point on the moving air, Tahoe. The before/after/before/after (do it twice) dyno tests should be done with, and without, fan-blown air down the side of the car. I'm not sure that would simulate driving at speed, but it might be close enough. I'm also not sure who would be willing to go through a complete dyno test in an ABAB experimental design. I also read somewhere that the vent fins serve to move sufficient air to the proper place behind the plate.

cvazquez

I removed my restrictive plate and feel the difference on the butt dyno. I would never consider placing the plate back on. Extremely happy with the mod and K&N air filter. Also, love the sound of the intake... the Boxster is no longer starving for air after the mod.

drcollie

Engineers at Porsche would never leave 15 HP sitting on the table for simple air venting. Think about it. They spend thousands of dollars in engineering to get 1 HP out of an engine and maintain reliability.

Butt dynos are highly affected by sensory input (noise, intake and exhaust). Always have been.

Before I would remove mine, I'd what to see what a new air sensor costs. Probably not cheap.

cvazquez

Understand your concern, but your missing out. I have not heard any issues with the air sensor after taking off the restrictor plate. The air cleaner is high inside the air-box compartment, so I can't see why the air sensor would be damaged by the removable of the restrictor plate. IMO

renvagn

Great discussion. I am just beging to crawl around the 987 and noticed several nicks in the trailing edge of the air intake cover. I am wondering how much water would be drawn in to the air filter if the baffle was removed?

cvazquez

I was stuck driving in a rain storm after the restrictor plate was off and had no issues whatsoever. My average speed was 75 miles per hour on hwy 95 for (4) hours.

cvazquez

Forgot to mention that you'll need to drive the Boxster approx 100 miles for the ECU to learn the engine is getting more air-flow. You do not have to drive the vehicle for the entire 100 miles non-stop. It's an accrual mileage to get the real benefit.

BoxsterG

I have some things left over from my '05 987 S that I want to give away if anyone is interested. 987 Grills and restrictor plate, Amber Side markers, aftermarket Air filter (given to me by freind but is new and unused), and some other small tidbits. I dont forsee me needing these anytime in the near future and dont want them to go to waste. It appears that we will be obtaining a Panamera as opposed to another 987 S. Please PM me if you are interested.

drcollie

I really don't think I'm missing out at all. Here's the dyno pulls over at Planet 9. Like I said, Porsche would never leave that much free HP on the table for want of simple airflow:

http://www.planet-9.com/cayman-boxst...-snorking.html

cvazquez

I believe the numbers from the dyno pulls since they did not run the vehicle for approximately 100 miles for the ECU to reset. At first I did not feel the difference, but after a long trip to Tampa and back really felt the difference. The boxsters throttle response is so much smoother, plus I can feel the car pull nicely. With the restrictor plate I felt the vechicle gasping for air. Additionally, I changed the airfilter to BMC the same day the restrictor plate was taken off...

I can feel the difference, and it's not my imagination.