spark1

I searched for previous threads and did not find as much as I thought I would.

I found an IPD thread here but had no substance. I checked out ipd's website and they show a rear wheel horsepower increase of 15.9rwhp. That was with a Boxster S Tip. Here is the link: https://www.ipdplenums.com/products/...s/986-boxsters

Curious what any of you have done

Byprodriver

The IPD parts work very well, but I would not expect that much of a power gain. Most of the increase comes from a bigger throttle body witch you can get from a 996. (75mm)

boxster newbie

check out a throttle body replacement, Soler , nevada based i believe. thinking to try one myself.

spark1

looked at their website. Looks like it works on on 2005+

KC-CarGuy

Subscribed. Might be a fun weekend project.

spark1

I think I've thought this out....interested in any feedback.

After gathering as much information as I could about the different intake options I decided to go back to basics to determine what is best for getting the most HP gain (bang) for the buck. I have a 2002 S which is stock except for a full suspension upgrade set up for autocross and a factory replacement engine at 23k miles in 2005 due to IMS failure. It has just over 60K miles (37k on new engine) and runs GREAT but because an alternator issue and a possible AOS issue had me open her up..... I thought this would be a great time to look at upgrading intake and exhaust to capture new HP as well as lost HP.

From what I understand, the most HP increase is going to come from more air during wide open throttle (wot). You can get this in many forms. Turbocharging, supercharging or simply increasing the air intake capacity is the most effective method. This is easier on cars with computers that use the stoichiometry formula that equals 14.7 % air to 1% fuel as the basis for fuel injected cars with computers. I'm older and a lot of my experience is tuning the old fashioned way...carburetors....but I definitely understand both concepts.

While I do not know as fact if Boxsters are programmed to use this 14.7:1 ratio I assume they are. This is usually achieved easily at idle and even through medium acceleration on most modern fuel injected Porsches. Keep in mind EPA standards and MPG ratings.... When you accelerate at wot the system built for good EPA ratings becomes restricted by physics and creates a bottleneck for air and exhaust to enter and exit the stock system.

Bottom line for me was this: More air in....the computer will adjust fuel injection to continue to strive to meet the 14.7:1 ratio. This is the HP increase. The computer will not perform any adjustments to allow maximum exhaust flow. This is the lost HP increase.

After looking at the IPD, the Ben Auto: https://www.uniwerksdesign.com/produ...intake-plenum/ soler and other options including swapping out the plenum and throttle body from a 996.... I decided on Pedro's garage TechnoPower2 kit: http://pedrosgarage.com/Site_2/TechnoPower2_Kit.html for the intake.... They use a 76mm TB and use the stock airbox.

I believe that is going to provide the most HP gain without forced induction. Now to capture lost HP....I am thinking equal length headers and an under-drive crankshaft pully which together should recapture about 10 lost HP.

Edit for incorrect computer reference....I just realized that only '98-'99 MY will adapt to more air because the accelerator pedal is connected to the throttle body and controls the butterfly valve and that 2000+ MY throttle bodys became electronic (E-gas) and the butterfly valve is controlled by the DME module and the ECM module which will not learn and will actually close the butterfly valve and produce a CEL. Bottom line for my 2002, I will also need a tune.

GVA-SFO

Well, I did it, but it seems that we are not getting the same math, or basic information. May be because we are talking about a different model ??

For the math, I think it is easy, the surface of a circle = Pi * R squared (R being half of the diameter)

In my case, (a 2001 Boxster S) the OEM t-Box was 68mm
(oem surface was 3,632 mm2)
The IPD (for a 2001 986 model) intake is 74mm
Surface is eqaul to 4,301 mm2

in my view, I got and increase : (4301-3632)/3632 = 18.4% !

Let me know: do I missed something on the above ???

...I would lik to add : an intake path is a kind of a "chain": the best performance is related to the one of the worse link !

Or, I think, when you look at this type of inprovement you should also look at the diameter and shape of the "long" intake tube between the t-Box and the the air filter.
And go for a performance air filter.
In my side, onthe intake path, I use an AFe filter, an IPD performance intake tube, an OEM 74 mm Porsche t-Box and an IPD plenum.
When I did this, I did not put the car on a dyno, but simply went back to Laguna Seca, and the lap time difference between "before and after" was in the range of a 2 sec gain

But, to make this comment more accurate, let's do not think intake only but thinking exhaust too:
When you look at the exhaust path, if you remove the exhaust header of a 986 and have some kind of design sensibility, you should get an opinion close to mine, i.e.: The OEM exhaust header of a 986 is probably the WORSE parts (looking with a performance eye) that you can find in a Boxster !
I do not think there are words to explain correctly this !

So I faced another problem : I'm absolutely NOT a "I make noise - look at me me" guy. (I do not need to have the others looking at me to be happy.) So, I bough a competition (tuned tubes) exhaust header, and modified it, by adding catalytic converters (the good one). I also I changed the secondary cats (no ECU measures at all on these ones) and also put "good" ones there !
Note that I kept the rear OEM muffler, as I did not found any that would be lighter (another gain that I'm interested on !), and I did not want something that would make more noise !

And this is how, I got the best results out of my brave M96.
Note that I was curious enough to leave everything is place and put back in place the OEM ehaust header: this was a DRASTIC downgrade ! the feeling before - after was kind of day and night !
Sure after few days, I went back to my "Home designed" exhaust header !

..my 2 cents on this very interesting 986 Air flow path analysis !

spark1

Your math is correct. Thank you for the input. You have the IDP system with a 74 mm TB and you have (exhaust modifications as well) noticed a significant 2 second gain on lap time and I gather from what you said that you do not have a "tune" (which is actually remapping the ECU AFR). What I was attempting to say was that only MY '98 and '99 can bolt on the new plenum and TB and get maximum benefit and beginning with MY2000 you need to remap the ECU to get maximum benefit of the newfound air surplus. I'll do my best to explain

Beginning in model year 2000, the Boxster base and the S came with a Bosch DME ME 7.2. The new DME uses a solenoid to open the throttle valve (versus previous years was opened by the gas pedal). Also introduced was a new "resonance flap" (a butterfly valve like the throttle valve) which is controlled by the DME. The ECU has pre-programmed (mapped) numbers for air to fuel ratios (AFR) based on the expected volume flowing through intake system based on a 68MM TB to expect AFR to be 14.7:1 at idle. This number is the stoichiometric number for AFR as most powerful and efficient mixture. This number is very achievable at idle but not as the rpms increase. Ideally you would want that number throughout the powerband but it is not physically possible so the engineers programmed the ECU of what numbers to expect based on the stock setup, Keep in mind that the ECU knows how much air is getting in because of the the MAFS measures the volume of air hitting it. The ECU knows the size of the intake tube, so multiplies the amount of air hitting the MAFS by the area of the tube to calculate the total volume air being ingested. There are three modes of operation the ECU has programmed numbers based on stock configuration- idle, discussed previously, closed loop and open loop. Idle and closed loop have preset fuel values called trims. Closed loop, or low load as it is often called, is part throttle, medium rpm operation. the car isn't working too hard. you are cruising along. MAFS measures air ECU looks up the appropriate amount of fuel to add in the mapped fuel trims, O2 sensors checks products of combustion in the exhaust to make sure everything is burning properly and, if not, either adds or takes away ('trims') fuel (these trims are initially short-term fuel trims - STFT - which become long term fuel trims-(LTFT) if they stay consistent over a period of time). this check by the O2 sensor is what makes it a 'closed loop' operation. Open loop is also called high load, or wot (wide open throttle). this is when the engine is hot, under load, banging against the rev limiter. the ECU switches to open loop based on a number of considerations; rpm (high) temp (hot) throttle position (ie, throttle is wide open but rpms are down - you are lugging the engine or going up a hill or something and ecu will go to open loop). The ECU adds more fuel The idea is that the extra fuel helps keep things cool, and prevents a hot, hard working engine from detonating. There is no feedback on whether you are hitting the target AFR or not - the ECU just calculates how much fuel to add based on MAFS reading and expected airflow (stock setups) through the intake.

GVA-SFO

Thanks, I fully understand your (extremely good) explanations.

Yes, the beauty (and the great fact) of having an ECU on a car engine, is to be "able" to have the engine ingesting a stoichiometric gas mix pretty much on all the (rpm) bandwith, on any altitude, ..and on on any barometric pressure.

In the past, with a carburetor engine, I think we could only have been lucky if we would have had a verry narrow band of usage were we would have an engine ingesting a stoichiometric mix !!, and this on a good day, with a barometric pressure that was "matching" the current Weber tune.

To be back on on such case, I admit, that I did not realized that having a DME 7.2 changed also that chain of computations for the mix and this with a more complete set of sensors, or, good for me to read your good text.

(For an small period of my life I had one of the early 996 (a 99), and then, short time after that, I had (for 11 years) a 2002 996. At the time of the change, I remember that my perception of the difference between the two engine was huge. After some talks about that, I learnt at that time that one of the reasons was that the 996.2 was equipped with Variocam Plus, i.e.: dynamic angle change of the intake cams in a progressive way all over the rpm range, when the earlier 996 had only 2 or 3 steps of angles of the intake cams. (It was what I kept on mind as main differences between ME 5.7 and 7.2 !!)
In my perception, I remember that I got the feeling that the torque (sure, the power, as power = torque * rpm !) was a lot more efficient !
(My "differenciation" between Torque and Power perception is like "I feel torque", at the instand of placing the demand of Power (accelerator) and I "feel Power", when that demand have been delivered !!
For sure this is quite "arbitrary" as the two specs are directly connected !)
By the way, I would be curious to have comments about how to perceive the "feeling differences" about Torque and Power ?

All to say that it would be great to to do a "reflash" to fully optimize the described hardware changes, but frankly, this could be bring some very serious problem for the smog checks. May be you read that recently California are working to have during smog check, a verification if the ECU of the car tested still have the original map !! (If I understood right, this could be done with the creation and the reading of the checksum of the ECU firmware. Not an easy task, I even do not know if there is a PID that can bring this data out via the OBD port ???
Anyway, I think, to play this game, I would think that you better have 2 ECU (from the same generation), and be able to do some "checks" by interchanging them. I never tried this "sport" so, I'm not sure it is doable !
I know that the VIN is at least into one EEPROM located in the gauge display unit, but, I would not be so surprised that it could be also located in the ECU ? (If yes, then, what's up if the two VIN do not match ?) And, I never read if the ECU, could be "over"writed with another VIN too ?
To be honnest, after thinking about the potential effects, I was not for getting more efficiency by reflashing my OEM ecu !!

Anyway, this is an extremely interesting topic, were most probably very little information is known by the "common audience" and drivers.

spark1

Yes it is. And thank you for contributing and adding useful information. I was not aware of the proposal to check the ECU for tuning changes. I do know that recently California has cracked down on enforcing the rule that smog stations put Boxster tops in service mode and Open the top service panel above the engine and look for??? I decided that I’m going to move forward with the IDP kit first. Then after I put on equal tube length headers and the under drive pulley attempt a tune

Carlton Bale

You can install a 996 tune into your ECU to accommodate the increased airflow. Here are the instructions. It should retain all emissions checks.

http://986forum.com/forums/diy-proje...-row-tune.html

GVA-SFO

@ Carlton Bale, Do you mean by that, that exchanging the OEM 986 ECU, against an OEM 996 (same gen, i.e.: ME 7.2) ..would do the "trick" ??

Carlton Bale

You don’t even need to swap the ECU. You can install the 996 tune file on the 986 ECU using the PC-based Porsche technician tool.

The 996 tune has higher mass air flow and fueling targets, but otherwise is mostly identical.

GVA-SFO

Very interesting point !

Well, I do not know how much it cost to either get the tool and the files to be able to load it.
But, looking at ebay, I can see that a 996 ECA can be found for US$ 280 !
see for example : eBay item number 124883660790

This seems to be at least a complete risk free try, were one can very easily check and "compare" the results !

GVA-SFO

Very interesting point !

Well, I do not know how much it cost to either get the tool and the files to be able to load it or have it done by a tech.
But, looking at ebay, I can see that a 996 ECu can be found for US$ 280 !
see for example : eBay item number 124883660790

This seems to be at least a complete risk free try, were one can very easily check and "compare" the results and be able to easily "walk back" !