tuning programmable engine management systems

[911st]

Originally Posted by 911st

Could that be built in by the Porsche to test the knock sensor?

Again, do you think the 67 deg advance could be a test of the knock sensor. If that dose not trigger it nothing will.

Further, it could be that if this dose not get triggered, it might enable a limp home mode to protect the motor.

I recall reading that the Porsche cars of that area took a set depending on the fuel quality used. It took several tanks to good fuel to take a new set unless you did something like disconnect the battery.

[scarceller]

Originally Posted by 911st

Again, do you think the 67 deg advance could be a test of the knock sensor. If that dose not trigger it nothing will.

Further, it could be that if this dose not get triggered, it might enable a limp home mode to protect the motor.

I recall reading that the Porsche cars of that area took a set depending on the fuel quality used. It took several tanks to good fuel to take a new set unless you did something like disconnect the battery.

I doubt it, I simply think I may be looking at a wrong map in the chip. I really need to dig into the 993 chip to be certain. For now please do not trust those 993 ign maps. I trust the graphs on Steve's site much more.

[drb930]

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[scarceller]

I have one stupid question I should have asked way earlier about the 993 car:

How many teeth are on the crank? I must be certain because the number of teeth are part of calculating the timing values from the raw data in the maps.

I assumed 129 teeth as in the 84-89 Carrera but if I'm wrong all the timing numbers would be off.

[safe]

I'm 90% sure that the 964/993 has a common 60-1 timing wheel instead of the stupid 129+1 carrera arrangement.

[safe]

Sorry, 60-2, now I'm 100%

The flywheels sold for 3.6 conversions has the 60-2 configuration.

[scarceller]

Originally Posted by safe

Sorry, 60-2, now I'm 100%

The flywheels sold for 3.6 conversions has the 60-2 configuration.

Safe,

This changes everything! I will need to figure out the new timing formula for the 964/963 cars. 60 teeth is very different than 129!

It will take some work and time to figure this new formula out so are you 100% on the number of teeth?

Thanks

[safe]

Originally Posted by scarceller

Safe,

It will take some work and time to figure this new formula out so are you 100% on the number of teeth?

Thanks

Yes.
http://www.patrickmotorsports.com/part/659/

[scarceller]

OK, so we have 60-2 teeth on the flywheel.

Anyone know what the base ignition timing spec is at idle fully warm for the 993? Should be around 0deg to -5ATDC. Knowing this would help figure out the formula.

[safe]

No answer to your question but where is what I found in the workshop manual about the 60-2.

The manual I have had nothing to say about idle timing...


1. Speed and reference mark sender
The DME is combined with an inductive
sender for engine speed and reference mark
detection. For this purpose, a toothed ring
gear is machined onto the flywheel. This ring
has a total of 60 teeth. Two of these teeth are
replaced by cutouts to generate the reference
mark signal. The reference signal is set at 84.
BTDC.
The air gap between the sender and the
flywheel ring gear is adjustable and must be
1.0:t 0.2 mm.

[safe]

Googled and found on the website of our "all time favorite pelican".

Porsche 993 MAF & DME System Data:
RPM Ignition Timing
Idle 3.5
1000 13
2000 32
3000 35
4000 38

The ignition timing is in degrees advance BTDC.

http://www.systemsc.com/tests.htm

[scarceller]

Thanks for getting me the # of teeth on the 993 flywheel.

I figured out the timing formula and found the right maps, here they are:



Looks much better, I check my numbers (ballpark) against this site:
http://911chips.com/ignition.htm
And I trust this stite

[EPorsche]

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[911st]

A lot less advance than I expected. Fuel must bun extremely fast at the 993's compression.

My 10.3/1 2.8 twin plug MFI motor we ran about 24-25 deg total advance.

[scarceller]

Originally Posted by 911st

A lot less advance than I expected. Fuel must bun extremely fast at the 993's compression.

My 10.3/1 2.8 twin plug MFI motor we ran about 24-25 deg total advance.

Yup, they back off on ignition at higher RPMs.

[psalt]

Fuel must bun extremely fast at the 993's compression.

The burn rate does not vary with compression. If these numbers are correct, to me they mean they traded off high speed power, for part throttle fuel efficiency. They are running mid/high 30's BTDC at cruise rpm/load, which gives a better indication of the burn rate of the chamber. They are running the 11.3 compression for mpg and retarding the full power output, because a 993 has more than enough performance for more then most users.

[scarceller]

Safe,

Would like to know if the the 964 also uses 60-2 teeth on the flywheel? I think you mentioned it does.

Thanks.

[safe]

Originally Posted by scarceller

Safe,

Would like to know if the the 964 also uses 60-2 teeth on the flywheel? I think you mentioned it does.

Thanks.

Yes, it does.

[dfink]

OK so what is the consensus. Do I need to update page one with the proposed targets for the cruise. Looking for suggestions here.

[scarceller]

Originally Posted by dfink

OK so what is the consensus. Do I need to update page one with the proposed targets for the cruise. Looking for suggestions here.

For cruise maps we need to talk about them in 2 parts: PT Fuel and PT Ignition

For Ignition I would simply start with the 89 Ignition maps, we know they are safe for single plug engine as they are factory.

Fot PT fuel:
0-25% load I'd shoot for 14.2AFR if the car can handle it (not to lean)

25%-60% at 60% 13.5AFR tapering to 14.2 at 25%

60% - 80% 13.5AFR at 60% tapering to 13.0 at 80%

80%-100% by the time you hit 100% you should be at WOT fuel setting 12.8 to 13.0
at 80% about 13.0 to 13.2

The idea is to keep lo-load at best fuel economy 14.2 then taper to 12.8 for WOT, start tapering gradually then get more aggressive after 50% load.

If you look at the 89 PT fuel map you will see this is how the factory also did it