Originally Posted by ike84 (Post 629906)

Instead of raising the trunk lid you could just cut a giant hole in it and mount a scoop over the hole. Kinda the poor man's version of your pic earlier. The aero images of our cars that I have seen show that to be a relatively low pressure area but I'm sure it can't hurt.

Sent from my POCOPHONE F1 using Tapatalk

Originally Posted by itsnotanova (Post 630451)

http://986forum.com/forums/uploads02/aero1613188530.jpg

This "computer generated" aerodynamic picture somewhat shows what I'm talking about. That one line that starts on the hood and flows along the top of the door is close to what I see water spots do on my street boxster after driving in the rain. On my car it takes a sharper turn after the B pillar and flows right above the front corner of the trunk.

Originally Posted by itsnotanova (Post 630494)

http://986forum.com/forums/uploads02...1613312585.jpg
If I stay with the M96 motor, then I was going to use this scoop. By what I could tell from a rough measurement it should fit without too much modification to the roof. I believe it would fit through the rear window and the intake would be just above the top of the roof. About right where the red line turns to blue in the aero pic

Originally Posted by ike84 (Post 630496)

That should do it. I would definitely try to get the horizontal aspect of that as far forward on the roof and possible so that it's not right at the break line where air separates from the roof line. It may be worth it to place some vortex generators in front of it too to keep as much air in their line as possible. How are you gonna duct the air into the inlet from that point though? Are you gonna plumb it to the TB or just use it as a breather for your filters?

Sent from my POCOPHONE F1 using Tapatalk

Originally Posted by itsnotanova (Post 630498)

I was going to turn the intake tube with the TB as far forward as possible. I'm hoping the air filter will fit within the area after the neck.

Originally Posted by itsnotanova (Post 630498)

I was going to turn the intake tube with the TB as far forward as possible. I'm hoping the air filter will fit within the area after the neck.

Originally Posted by ike84 (Post 634034)

Hey woody, question for ya. I've been running now for a few hundred miles on this setup with 996 tune and big exhaust and I noticed that the car now likes to move! More specifically, around 4200 rpm at WOT she pushes me back in the seat, which I don't ever remember happening before. Weirdly though, it doesn't happen every time I pass 4200rom at wot. I can't quite pinpoint what is contributing to this happening (or not happening). I'm wondering if maybe the DME is still figuring stuff out.

I know most of your driving is dirt track, but I'm curious about what your experience has been so far? Big gains at high rpm? Are gains always there?

Btw, how's the shop build going?

Sent from my POCOPHONE F1 using Tapatalk

Originally Posted by itsnotanova (Post 634049)

Every m96 I've driven seems to come alive between 3500-4500 and falls flat after 6000. There does seem to be a bigger jump in power at the 4000 mark with my 996 intake 2.7 rally car than with my 3.4 street car. I don't think it takes that long for the computer to learn and adjust. I have to disconnect the battery on my rally car at the end of the day. Every time I reconnect the battery, the car idles weird for about five minutes but seems to run fine after that. I don't know why you're feeling a jump sometimes and not the other. Aging fuel pump?



The building is going up pretty good for an old man working by himself. I start on installing the sheet metal tomorrow.

http://986forum.com/forums/uploads02...1619251786.jpg

Originally Posted by blue62 (Post 634069)

Ike

I have experienced the same as you in regards to the torque curve around 4200 RPM under WOT or near WOT.

Every now and then it is like there is a little more power.

My car is a 2000S completely stock.

I thought that perhaps my MAF was going bad.

Or that my resonance flapper was hanging up.

But everything checks out ok.

The car runs great.

The only thing I could come up with is:

I can only get 91 Octane fuel.

So my thought is that the DME/ECU is holding back ignition timing to prevent pre-det or knock.

I think when I feel the little bit of extra power is when the ECU/DME is allowing a little more ignition advance.

Keeping my eyes open for some higher octane fuel to test my theory.

Thoughts????

Originally Posted by ike84 (Post 634075)

Woody is right that in general the torque curves for the 2.7 and 3.2 don't start to peak until past 4k. I had never noticed the "kick" at 4200 before I did my intake and exhaust mods though. That's definitely interesting that your stock s does the same thing.

At first I wondered if it could be variocam switching over at different points depending on throttle and load but from everything I have been able to find that it always a fixed transition at 5500rpm. I posted recently about this topic but I haven't gotten any responses yet.

I have read similar comments about the timing but I'm not sure about it. I think that the base tune has ignition advanced to as early as stuttgart deemed "safe" and the only adjustments the dme will make is to pull timing if knock is detected. I've not seen any documentation that the dme will advance timing further if the fuel is higher quality. I've also not ever read that the dme will advance timing beyond the base map under specific circumstances such as wot or rpm threshold.

With that being said, you could be right that at a high enough rpm and load the timing becomes such that 91 will knock and then the timing gets retarded. I run 93 but it's the same tank that's been sitting since before I started all this work last fall, so I'll be curious to see what happens with the next fill up.

The other thing I wondered was the fuel maps in regards to open vs closed loop. Woody and I are running the 996 tune on 2.7 and 3.2 motors, respectively, and we should be encountering rich conditions when the dme flips to open loop mode. I would think that I should be so rich in open loop mode that it would probably hurt performance, where woodys probably wouldn't be effected much. I don't know of any way to actively monitor what mode the dme is running in though, unfortunately.

Sent from my POCOPHONE F1 using Tapatalk

Originally Posted by ike84 (Post 635575)

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.

Sent from my POCOPHONE F1 using Tapatalk

Originally Posted by blue62 (Post 635601)

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.

Originally Posted by blue62 (Post 635626)

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.

Originally Posted by ike84 (Post 634075)

Woody is right that in general the torque curves for the 2.7 and 3.2 don't start to peak until past 4k. I had never noticed the "kick" at 4200 before I did my intake and exhaust mods though. That's definitely interesting that your stock s does the same thing.

At first I wondered if it could be variocam switching over at different points depending on throttle and load but from everything I have been able to find that it always a fixed transition at 5500rpm. I posted recently about this topic but I haven't gotten any responses yet.

I have read similar comments about the timing but I'm not sure about it. I think that the base tune has ignition advanced to as early as stuttgart deemed "safe" and the only adjustments the dme will make is to pull timing if knock is detected. I've not seen any documentation that the dme will advance timing further if the fuel is higher quality. I've also not ever read that the dme will advance timing beyond the base map under specific circumstances such as wot or rpm threshold.

With that being said, you could be right that at a high enough rpm and load the timing becomes such that 91 will knock and then the timing gets retarded. I run 93 but it's the same tank that's been sitting since before I started all this work last fall, so I'll be curious to see what happens with the next fill up.

The other thing I wondered was the fuel maps in regards to open vs closed loop. Woody and I are running the 996 tune on 2.7 and 3.2 motors, respectively, and we should be encountering rich conditions when the dme flips to open loop mode. I would think that I should be so rich in open loop mode that it would probably hurt performance, where woodys probably wouldn't be effected much. I don't know of any way to actively monitor what mode the dme is running in though, unfortunately.

Sent from my POCOPHONE F1 using Tapatalk

Originally Posted by new986owner (Post 635738)

Edit. Just sent Ike PM on ROW tune)

Could you kindly advise where to get a 996 ROW tune to upload to a 01 3.2? I am trying to complete the process and have the new TB, but got a cayman intake plenum which doesn’t fit. I think I need a 996 C4S plenum. Pardon my ignorance.


Sent from my iPhone using Tapatalk

Originally Posted by ike84 (Post 635914)

Hey man, I just saw this post. I pm'd at the end of the week, hope you got it. Why doesn't the cayman tb fit? Good luck!

Sent from my SM-T595 using Tapatalk