Carrera 3.2 tunning w/o a chip?

[911st]

I have been using the custom chip option from SW to get my Air/Fuel ratios to their ideal.

I recommend this as to anyone.

However, I an interested in running in a stock class where I can not change the chip.

How tunable is the 3.2 without a chip? Or, what adjustments do we have access to?

Directly or indirectly.

Here is what I am thinking.

I can run a Cat Bypass.

The adjustments that I know of is the adjustment on the AFM that effects how fast the door moves with changes in air flow.

And, the fuel quality switch on the brain under the drivers seat.

There is also a Calif. smog jumper wire under the seat that is pluged in for Calif cars. I unplugged mine.

Is the flywheel pick up adjustable (timing)?

Is fuel pressure adjustable?

Anything else adjustable?

My expearance and understanding is the AFM dose not effect the A/F's much after around 5200rpms.

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Here is my thought for now:
Put the stock chip back in and dyno the motor for A/F ratios.
Use the fuel quality switch to get the WOT A/F's the best possible from 5k and above first.

If I am running to rich with a stock muffler and cat bypass, I do not know if there is a way to lean it.

For the A/F's under 5K, if needed, might use the adjust-ability of the AFM.

Somone just told me that enrichment fuel is created by a vacuum sensing fuel pressure regulator that when the vacuum level drops, as under WOT, it rases fuel pressure 5 lbs.

I understand that under curse, the O2 circuit is going to try to adjust the A/F back to a lean 14.7/1 or something.

What is stock fuel pressure?

Any other adjustments I can consider.

[84_Carrera]

Top curve is w/ aftermarket (non-Wong) chip, fabspeed cat bypass, muffler bypass, and #2 DME fuel setting (+6% fuel). I'm also running a cone instead of the airbox, though I saw NO improvement with this on the dyno.

[stlrj]

I have been able to tune my 3.2 with different injectors. I'm running a set of saturated GM Multecs right now that make a noticeable performance difference in all rpms. It also seems to address the over rich condition we encounter above 5k.

Just something you might consider too.

Cheers,

Joe

[84CarreraSC]

Cali. smog jumper wire? I'm listening. Yes, I did a search but could not find any relevant info for my 911

[911st]

Joe,

Is it a standard that the Carrera chip is to rich above 5k?

If so this must be the factory's attempt to overcome the short coming of the barn door AFM where its input is no longer usable.

This would give some latitude for muffler mods. That is, more air flow, same fuel, lower A/F's above 5k. Under 5k the afm automatically compensates.

May be why 3.2's respond so well to cat bypass and sport mufflers.

I have a chip tuned for cat bypass & sport muffler. I just have the bypass and did not yet have the sport muffler and the first chip was still to lean above 5.2k. Have not tested the second burn yet.

I dynoed at 217 hp at the rear wheels but the AF was 14/1.

So, is how the chips work mostly from leaning the A/Fs.

84CarreraSC,

There is a wire that sticks out under the drivers seat at the brain. I think it is brown single wire. If it is plugged in to its self, it trigers what ever the special Calif. smog requirement is. I would only guess it keeps the O2 in the loop under more operating conditions, but I do not know.

If you can locate your wire and it is plugged together, you can unplug it. I do not know if I noticed anything as I did it with my chip.

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Can any one confirm it is the fuel pressure reg is how we get enrichment fuel?

Do we have any controll over the fuel pressure?

Does the O2 then dial back the A/Fs until the WOT switch is triggered.

I think the WOT switch take the O2 out of the loop and trigers a different fuel n timming map?

[ischmitz]

I am trying to understand what you want to accomplish. If you want to cheat the classification a modified chip hidden inside the DME is arguably easier than making any modifications to the fuel pressure or timing. It is pretty hard to be detected without sophisticated equipment. You can modify static fuel pressure and/or static timing by messing with the fuel pressure regulator and/or the reference sensor position. But WHY?

The fuel pressure regulator in an EFI setup ensures a constant differential pressure over the injectors. The differential pressure [P(fuel) - P(intake)] defines flow rate when open. The pressure regulator senses intake manifold pressure and adjusts the fuel pressure to make sure the injector flow is always the same for a given opening time. If you use an adjustable fuel pressure regulator you could introduce a fixed offset to the fuel ratio.

A timing adjustment via the reference sensor could be realized. It would require a custom clamp to move the reference sensor. Again, this would be a static offset over the entire RPM and load range.

Howeverm chip tuning is much more flexible and effective - so why bother?

Ingo

[911st]

For me, mods the cheat are not what I would do if I build for the stock class. However, it is interesting to know what we can do to adjust or tune the motor. If the fw sensor were adjustable, it would be open game.

I agree, a chip is the best method for tuning. ( I have a custom Euro Style SW chip done using dyno A/F's w no O2 input.)

My goal, would have to be to get the most out of my motor using adjustable systems on the motor. I would not replace the fuel presure reg with an aftermarked. (Yes it is easyer to just fib about a chip).

Sounds like the MO for 3.2's is that they run rich after 5K.

Do we have any adjustability over this. In my case a cat bypass will lean it some. The only other stock method to flow more air would be to look at the air filter. The stock one is tough to beat so that is a dead end unless somone wanted to take the risk and run w/o or put a screen in there.

Again, the way to address a to rich condition above 5k would have to be with making the car breath better unless we can dial down fuel pressure.

If for some reasion, all systems are functing correctly and it is lean up top, then the fuel quality switch seems to be the way to dial in more fuel.

After the over 5k is dialed in, then I guess looking at the AFM as a potental adjustment is a possibility.

If I understand correctly, we will not be effecting curse A/F's as the O2 loop will readjust back to 14.7/1.

May not be legal for me but one other possability that comes to mind is to play with the senser inputs. The flywheel is just one. Motor temp is used by the CPU to modify the fuel maps. If the temp senser (s ?) read hot, timing is backed off. There are also clamps' that can be used on things like the O2 signel.

Unpluging the 02 or jumping the WOT switch might fit into this catigory.

So, other than the idle air bipass, fuel quality switch, AFM spring tension, is there anything else we can adjust?

[stlrj]

Does stock class allow different injectors?

[911st]

Not sure about changing injectors. Are you thinking I could go smaller, then tune around them?

[stlrj]

Originally Posted by 911st

Not sure about changing injectors. Are you thinking I could go smaller, then tune around them?

Possibly. However, these Multecs I'm using come standard on GM V6 engines with displacements of 3.1 to 3.3 liters at fuel pressures of 41 psi. Our 3.2's run at 29 psi.

That could be the reason they work so well on my 3.2 since they seem to be so well matched.

Just something to keep in mind.

[Zeke]

What minimum weight in the class and how far off are you? This is cheap HP. How well do you drive? A good schooling and lotsa seat time is not so cheap, but results in better lap times. What else are you allowed to do? R compound street tires? Man, a well set up car is much easier to drive and drive fast. Get up on that wheel! You don't need no stinkin' horsepower.

[911st]

Milt,

It is a points system and I want to keep the mods under 100points.

I wanted to go with R compond tires for 50 points.
I already have a LSD which is 15 points.
Was thinking 22/29 torsion bars for 30 points.
Then 5 points for removing the cat.

Optionally, I can go with non R tires and save 25 points.
Could stay with stock springs and sways but with sport shocks, and save 30 points.

Then I can spend the savings on brake cooling, chip, sport muffler, spoilers, and some weight reduction (lighter seats, RS door pannels, glass bumpers...

My thought is that R tires and springs will make the bigest contribuition to lap times.

So again,
sticky street tires w stock suspention and a bunch of mods like spoilers, brake cooling--or--
mostly stock with R tires & stiff suspention with no spoiler, chip and about 10 less HP?

[Zeke]

I guess it depends a lot on the track(s) you will be running. Here's my take: I had a '71 S with a very tired motor. Compression on no. 6 was a wish, that's all. However, I set it up with matched t-bars and shocks, with an appropriate up grade on the sways, not to mention Elephant bushings (which should not add any points). Tyson Schmidt took it out at Willow and was beating up on people that maybe should have been a little faster, or were surprised at the little S crowding them. Can Tyson drive? You bet, and he got everything out of the ol' Ragamuffin that was to be had.

I say it was all in the suspension and the driver, it sure wasn't wholesale HP. And then I put on the R tires.

[911st]

Ya, they ding me for hard bushings and ER's.

I agree, it is more the car. A lot of us seem to put thousands into making the car marginally better when the same spent on driving lessions and track fees would make us faster yet.

What 100 points of the following would make for the most enjoyable and fastest car?

Mod Points:
25 pts, sticky street tires, say Dunlop Direzza Sport Z1 Star Spec
50 pts, R type tires, say Toyo R888
5 brake cooling
5 master brake cylinder
5 brake ballance
10 calapers
5 smaller battery
5 relocated battery
10 full race seats
5 adjustable race seats
5 light weight interior
5 air removed
5 factory rear spoiler
10 light spoiler
5 glass rear hood
20 gears
15 limited slip
5 cat bipass
5 air housing mod
5 chip
5 higher rp
5 sport exaust
30 torsion bars
5 plastic bush
20 sway bars
5 strut bar
20 non stock bumper
10 non stock glaizing

My thought is

Toyo R888's, LSD (I have), cat delete, torsion bars.

I would run good pads & high temp fluid.

This means passing on a rear spoiler, brake cooling, chip, sport muffler...

If I gave up the R tires and or the 22/29's I could go for the other goodies.