82 mm throttle body

[ike84]

Hey everyone, I wanted to share some pics of a project I'm finishing up. But first, a little back story...

2 years ago I was in the market for a sports car and stumbled upon a real garage queen - 00 base with 27k miles on it. I snatched it up and had Pat Williams do an IMS replacement for me and have loved the car ever since. Recently I moved to a rural area with wide open back roads and found myself wishing the car had a bit more oomph (mostly in terms of acceleration). So, the quest for more power began.

I know what everyone is thinking at this point "oh boy, not another one of these guys". To that end I will only say that I'm not doing this for racing purposes and I'm not looking to make the car spit flames out the back. I'm a tinkerer by nature and a bit of a scientist by trade so when really studying these cars it seemed to me that there are some obvious points that can changed and possibly improved. Plus, I'm curious to see what will happen lol. So, here we are, with the first part of that mad idea - bigger intake.

Here are the parts, it's really quite straightforward truthfully. Just a bit radical in execution
Early 996 plenum (for cable driven TB)
82 mm throttle body (cayenne turbo)
2 x 45 degree 3.5" silicone intake elbows
A short segment of 3.5" stainless
3.25" MAF housing (identical size to 996 but part is aftermarket Mercedes)
3.5" T shape short ram intake for GM (mostly found on C5 vettes)

Here are the porsche "speciality tools" used
3# mason hammer
4" hole saw and reciprocating saw
Factory jack (thanks porsche)

On to the execution
Gut the intake (drop the motor to do this, you can get the stock box out intact)
Strip the trunk and relocate the ECU a bit to gain slack on the wiring harness
Use mason hammer and jack to deform the cross member downward by 3/4 inch to gain enough clearance
Use hole saw to cut opening into firewall (gasp?!?!) between trunk and engine bay and use reciprocating saw to open up the too of the engine bay enclosure a bit.
Assemble and mount components

There are a few minor things from that point - opening up the wiring harness to get slack on the MAF sensor wiring to reach the new housing, extend the AOS hose to reach new attachment position, trim out the rough opening with rubber u moulding, and knock out the vents in the trunk to provide adequate ventilation.

And now, in the name of "pics or it didn't happen"...

Now look, I'm sure there are gonna be guys who are gonna gripe about not having dyno numbers (they will come but not until later in the project, lots more to come eventually) and criticize for loss of low end torque (which I realize is a very really possibility). But like I said, this is driven by a love of tinkering and a very itchy "what if".

The next step in this madness will be a 2.5" exhaust setup, and then plenty more after that. It's gonna take me a while to work through everything so bear with me, but I promise to keep pics rolling as the progress happens.

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[Muskoka Minute]

Looking Great so far!
Please keep us posted

Cheers!

[ike84]

Originally Posted by Muskoka Minute

Looking Great so far!
Please keep us posted

Cheers!

Thanks Muskoka! Btw I chimed in on your motor situation. My heart goes out to you.

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[itsnotanova]

I stuck a 3.4 intake/throttle body and 3.8 997 exhaust manifolds on my 2.7 rallycross boxster. I can feel that i lost some low end torque but gained higher rpm HP. I'm rarely below 4000 rpm so it works for me. I moved the air filter inside the trunk and I'm surprised at how quickly the filter gets dirty. I've raised the trunk lid in hopes of drawing in more fresh air but I still need to find a way to get more fresh air inside the trunk. The air coming from the rear wheel well is very dirty. Granted I'm racing in dirt, so you should have a lot less than me.

Here's my build thread

6 months to live build thread

[ike84]

Originally Posted by itsnotanova

I stuck a 3.4 intake/throttle body and 3.8 997 exhaust manifolds on my 2.7 rallycross boxster. I can feel that i lost some low end torque but gained higher rpm HP. I'm rarely below 4000 rpm so it works for me. I moved the air filter inside the trunk and I'm surprised at how quickly the filter gets dirty. I've raised the trunk lid in hopes of drawing in more fresh air but I still need to find a way to get more fresh air inside the trunk. The air coming from the rear wheel well is very dirty. Granted I'm racing in dirt, so you should have a lot less than me.



Here's my build thread



6 months to live build thread

Very cool dude! I'm a big fan of your work, I nearly cried when I got to the end of your original build thread .

One idea I had was to utilize the rear wing (I stole the idea from lambo) drill holes in the front face of the wing so that when air hits it it will be directed down and into the trunk. With enough perforations there will probably be plenty of airflow there. The problem obviously is water there, but if it's a dedicated track car I would think it might work well.

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[itsnotanova]

Originally Posted by ike84

Very cool dude! I'm a big fan of your work, I nearly cried when I got to the end of your original build thread .

One idea I had was to utilize the rear wing (I stole the idea from lambo) drill holes in the front face of the wing so that when air hits it it will be directed down and into the trunk. With enough perforations there will probably be plenty of airflow there. The problem obviously is water there, but if it's a dedicated track car I would think it might work well.

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Who or what is lambo? I've been thinking some kind of scoop too. Just enough scoop to pressurize the trunk to keep dirty air from entering elsewhere inside the trunk. Any water that would enter would leak out the bottom of the trunk and shouldn't be able to enter the motor.

[husker boxster]

Originally Posted by ike84

knock out the vents in the trunk to provide adequate ventilation.

Could you elaborate on this a bit? Where is your cold / fresh air coming from?

[ike84]

Originally Posted by husker boxster

Could you elaborate on this a bit? Where is your cold / fresh air coming from?

For now I've punch out the two vents in the rear of the trunk on the sides. These were there to vent the trunk when it heated up and communicates with the area where the stock muffler was located. If this isn't enough I can remove those popouts on the trunk floor to achieve the same effect. What I will ultimately wind up doing is using ABS to fabricate a dedicated "trunk space" and wall off all the intake components, which I am going to route down and out of those knockouts to twin turbos mounted below. With two young kids and a third on the way though, that part of the project is still quite a ways away lol.

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[NewArt]

Wow! You guys have taken this to a whole other level! Very cool!

[ike84]

Originally Posted by NewArt

Wow! You guys have taken this to a whole other level! Very cool!

Thanks man! I'm a huge fan of your videos! The series you did on your lowering springs gave me the info I needed to install my coilovers, and your intake videos were super cool. I was sad to hear you toasted the motor but I'll bet your loving the 987. How does is compare to the 986? Ever find yourself wanting to go back?

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[NewArt]

Originally Posted by ike84

Thanks man! I'm a huge fan of your videos! The series you did on your lowering springs gave me the info I needed to install my coilovers, and your intake videos were super cool. I was sad to hear you toasted the motor but I'll bet your loving the 987. How does is compare to the 986? Ever find yourself wanting to go back?

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Yeah, I was reviewing one of my videos and, you know, I do have rather a soft spot for that `04... I'm just glad that Vanessa, a racer chick, decided to buy it. More track days to come! :dance:

[ike84]

So today I got to test my AFR guage. Its actually a solenoid controller from innovate motorsports that integrates a Bosch wide band afr sensor. What I saw was rather interesting (and a bit concerning).

On startup at idle, AFR was running 15.1-15.3! Too lean! Under light loads this would fluctuate back down 14.5-14.9. At higher loads this would go lean again, 14.5-15.3. At WOT it dropped way rich, down to 10.5-11.3.

Interestingly, with foot off gas, it would peg lean (over 22).

Numbers in the drive home were a little less lean but Instill saw 15+ a fair bit of time.

I can explain the WOT richness - switching into open loop, the computer is fueling a 3.4L engine. Even with the biggest air intake in the world that ****************s just not gonna match up on a 2.7

The closed loop operation afr bothers me though. I would assume that with as sophisticated as our computers are (combined with what I perceive to be a general cover-your-ass approach from Porsche in regards to performance aspects of this car) that the computer would shoot for 14.7 or less at all times. I was really quite shocked to see 15+ so much.

With that being said, if the computer is gearing the fueling to hit a target above 14.7, I think that may be just one more piece of the puzzle as to why we see issues like bore scoring, overheating, etc.

I did have my battery disconnected this weekend so maybe it just needs a few days to relearn short term trims again.

Anyway, I'll keep things updated over the next few days to see if things change much.

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[blue62]

Originally Posted by ike84

So today I got to test my AFR guage. Its actually a solenoid controller from innovate motorsports that integrates a Bosch wide band afr sensor. What I saw was rather interesting (and a bit concerning).

On startup at idle, AFR was running 15.1-15.3! Too lean! Under light loads this would fluctuate back down 14.5-14.9. At higher loads this would go lean again, 14.5-15.3. At WOT it dropped way rich, down to 10.5-11.3.

Interestingly, with foot off gas, it would peg lean (over 22).

Numbers in the drive home were a little less lean but Instill saw 15+ a fair bit of time.

I can explain the WOT richness - switching into open loop, the computer is fueling a 3.4L engine. Even with the biggest air intake in the world that ****************s just not gonna match up on a 2.7

The closed loop operation afr bothers me though. I would assume that with as sophisticated as our computers are (combined with what I perceive to be a general cover-your-ass approach from Porsche in regards to performance aspects of this car) that the computer would shoot for 14.7 or less at all times. I was really quite shocked to see 15+ so much.

With that being said, if the computer is gearing the fueling to hit a target above 14.7, I think that may be just one more piece of the puzzle as to why we see issues like bore scoring, overheating, etc.

I did have my battery disconnected this weekend so maybe it just needs a few days to relearn short term trims again.

Anyway, I'll keep things updated over the next few days to see if things change much.

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Ike
That all seems like pretty normal numbers to me.
A couple of things to keep in mind:
14.7 fuel air ratio is not what the engine needs under all conditions to perform best.
An example is WOT.. it should go rich. Heavy engine load requires a richer condition.

Foot off the gas your getting 22: exactly you don't need fuel in the air to coast. your getting 22 because you don't need fuel under that condition but the engine still pulls in air.
Hell you don't need spark. Some modern day engines cut off fuel and spark all together under off throttle conditions. An AFR sensor will see all air (or nearly so) under off throttle conditions.

Another thing: 14.7 fuel to air is the ideal ratio for Catalytic Converter performance.
Not engine performance under all conditions.
On a modern day computer controlled engine the primary function of the DME/ECU system is "Catalytic Converter performance, engine performance is secondary.

The DME/ECU under closed loop conditions constantly fluctuates the fuel air mixture above and below the 14.7 fuel air ratio. That is why O2 sensor signals constantly fluctuate in a sine wave. The DME/ECU sort of looks for an average under closed loop conditions.

[ike84]

Originally Posted by blue62

Ike
That all seems like pretty normal numbers to me.
A couple of things to keep in mind:
14.7 fuel air ratio is not what the engine needs under all conditions to perform best.
An example is WOT.. it should go rich. Heavy engine load requires a richer condition.

Foot off the gas your getting 22: exactly you don't need fuel in the air to coast. your getting 22 because you don't need fuel under that condition but the engine still pulls in air.
Hell you don't need spark. Some modern day engines cut off fuel and spark all together under off throttle conditions. An AFR sensor will see all air (or nearly so) under off throttle conditions.

Another thing: 14.7 fuel to air is the ideal ratio for Catalytic Converter performance.
Not engine performance under all conditions.
On a modern day computer controlled engine the primary function of the DME/ECU system is "Catalytic Converter performance, engine performance is secondary.

The DME/ECU under closed loop conditions constantly fluctuates the fuel air mixture above and below the 14.7 fuel air ratio. That is why O2 sensor signals constantly fluctuate in a sine wave. The DME/ECU sort of looks for an average under closed loop conditions.

Hey blue,

Thanks for the response. That's interesting about the sine wave pattern, which is exactly what I'm seeing. That seems a bit less efficient than a "hold steady" approach at control but maybe it's more effective to continually correct.

That's also interesting about the cutting off of spark while coasting. It makes sense to do so for fuel economy, as long as the alternator keeps spinning to keep up with current load demand.

The reason the lean tendency was surprising is just the excess heat and likelihood of detonation under those conditions. I see your reasoning though that if the motto is "emissions first, engine second" then it makes sense to do so.

With that being said though, the numbers on my drive this morning were much more centered around 14.7, especially while cruising under moderate load. I really wonder if the short term trims just needed 20 miles to adjust the mixture. I suppose 20 miles of lean isn't too bad considering the detonation sensors/ignition retard built in to the dme.

I think it's fascinating to learn more about how these computers actually do their job. Unfortunately, Bosch me 7.2 is kinda like this black box with very little info about the logic and processes involved. I don't think I've seen a single thread on this forum which is technically detailed regarding this (beyond basic principles of open/closed loop, short/long term fuel trims). I can't even find a good one on nefmoto, which is probably the best site on the web for that type of info.

Anyway, for me the enjoyment will have to be postponed. Looks like I'm leaking oil from the passenger side bank. Probably plug tubes, I should have replaced them when I changed the plugs and coils over the winter. Back on to the stands we go!

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[blue62]

IKE
Most people tend to think that the O2 sensor signal drives the DME/ECU.
But what really happens is the DME/ECU drives the O2 signal.
The O2 signal on these cars operates between a low of around .1 millivolt to a high of about .950 millivolts. Stoichiometric or 14.7-1 is at .450 millivolts.
So the DME/ECU goes a little rich to drive voltage down then goes a little lean to drive volt up. Constantly. The DME/ECU uses the response from the O2 sensor as feedback (closed loop) info to determine fuel requirements or fuel trim to drive the O2 sensor signal.. Which in the end is about Catalytic Converter performance.

Stoichiometeric or 14.7 lbs. of air to 1 lb. of fuel is the ratio at which there is exactly enough molecules of air to combust ever molecule of gas.
So 14.7-1 produces an exhaust that is most easily cleaned by the Catalytic converter.
To rich (excess gas molecules) Cats plug up. to lean(excess air molecules) Cats burn up.

But 14.7-1 it is not the ratio at which fuel air burns the coolest or produces the most power.
That is why you see a richer mix at WOT or high load and leaner mix at idle or very little load.
Engine performance needs vrs Cat converter needs.

Most of the time cars are operated in the lower end to middle of the cruise range as far as engine load goes. That's why you see the air fuel ratio closest to 14.7-1 in that range. 14.7-1 meets engine needs and Cat needs equally in that range.

The shutting off of fuel and or spark at off throttle conditions does save fuel but it is more about pollution.
With the constrains put on automobile manufactures by the EPA everything (as far is engine performance goes) is about pollution control. Performance (power) or fuel mileage is secondary.
EPA restrictions are the biggest reason you can get more power and sometimes fuel economy from an after market tune. It is also why after market tunes are illegal in some states.

[ike84]

Originally Posted by blue62

IKE

Most people tend to think that the O2 sensor signal drives the DME/ECU.

But what really happens is the DME/ECU drives the O2 signal.

The O2 signal on these cars operates between a low of around .1 millivolt to a high of about .950 millivolts. Stoichiometric or 14.7-1 is at .450 millivolts.

So the DME/ECU goes a little rich to drive voltage down then goes a little lean to drive volt up. Constantly. The DME/ECU uses the response from the O2 sensor as feedback (closed loop) info to determine fuel requirements or fuel trim to drive the O2 sensor signal.. Which in the end is about Catalytic Converter performance.



Stoichiometeric or 14.7 lbs. of air to 1 lb. of fuel is the ratio at which there is exactly enough molecules of air to combust ever molecule of gas.

So 14.7-1 produces an exhaust that is most easily cleaned by the Catalytic converter.

To rich (excess gas molecules) Cats plug up. to lean(excess air molecules) Cats burn up.



But 14.7-1 it is not the ratio at which fuel air burns the coolest or produces the most power.

That is why you see a richer mix at WOT or high load and leaner mix at idle or very little load.

Engine performance needs vrs Cat converter needs.



Most of the time cars are operated in the lower end to middle of the cruise range as far as engine load goes. That's why you see the air fuel ratio closest to 14.7-1 in that range. 14.7-1 meets engine needs and Cat needs equally in that range.



The shutting off of fuel and or spark at off throttle conditions does save fuel but it is more about pollution.

With the constrains put on automobile manufactures by the EPA everything (as far is engine performance goes) is about pollution control. Performance (power) or fuel mileage is secondary.

EPA restrictions are the biggest reason you can get more power and sometimes fuel economy from an after market tune. It is also why after market tunes are illegal in some states.

Blue, thanks for the knowledge brother. Always more to learn about this stuff. I've been working through an automotive textbook to get a better understanding of different systems and this convo definitely put the fuel chapter next on my list.

I will say that the last drive I took (15 miles home) the afr stayed 14.5-14.9 the whole time during closed loop operation. I guess the stfts really did play into that. Which I think is interesting because it implies that the dme is programmed to run lean until it can dial in 14.7 more precisely, or that this setup provides more air than the stock 996 setup (less likely since the MAF should be able to dial this in precisely without the help of the fuel trims). Thinking this through though it may just represent a difference in MAF housings since I am using a 3.25" diameter honeycombed pipe from a BMW V8 intake - same diameter as the 996 but maybe with fewer curves in the piping I am flowing air more efficiently.

I'll have the battery unhooked while replacing the plug tubes so I'll be curious if it goes back lean for the first drive after that.

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[ike84]

Just wanted to.give an update - I logged my intake temps this morning and they're pretty hot. I have no idea where this data is compared to an OEM setup (maybe someone with a data logger can help out there) but I would like to see this way cooler. More work to be done!

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