Gus

I am looking for a little timing feed back - Running VEMS with a VARIORAM - and am having a little trouble dialing in the timing for the set up. I am bouncing around 300HP with this timing, but when driving the car hard the oil temp runs rather high. If i back off and keep RPM in the 5000 range the temp will lower to normal race temp range. Here is a picture of the current IGN Table that I am running. One thing that I have noticed is that in the higher RPM range I am more advanced than the stock timing for a 964/964 Cup and a 993 by 3 to 4 degrees. If you run a MOTEC, a VEMS or another ECU what IGN timing settings are you running??

-nick

I would start by setting your 100 (kpa I assume?) line to match the stock 964/993 WOT profiles. They're up on Steve W's site: http://911chips.com/ignition.htm. He has part throttle maps up too, but I don't know how load converts to kpa. Unless you assume 100kpa=100% load and 0kpa=0% load and draw a straight line. Then dyno-tune from there. If anything, you need much more advance at WOT. Timing should increase as load decreases. Where do the vems maps originate from? And are there any additional corrections to those numbers (for air temp, head temp, etc)? And is the tdc offset that you probably need to feed into vems confirmed to be correct?

For temperatures, might be worth monitoring egt while you start the tuning process. AFR is good?

Gus

Nick - Thanks for feedback - I have the full throttle timing settings for stock 964, 964 Cup and 993. Can't find info on 993 Varioram.
Will take your suggestion of plotting timing from the 3D display rom Steve's sight- Think this will work as a good start point. The load conversion could be a little issue but looking at the diagram it appears that there are 50 units of load compared to the 30 to 110 MAP Ign Chart - So each load unit is equal to 1.6 MAP units ( I hope so ) Will plot and see what comes out - Do not have any other timing variables loaded that would have effect on final timing out.
AFR is an auto tune and have EGT just need to get to dyno and do some test -
Thanks for help
G

-nick

Sounds like a good plan! Keep an eye on cht and iat temperatures while you're adjusting too. I don't have the numbers in front of me, but motronic pulls somewhere around 3 degrees at high intake temps. I think that the timing vs cht map only serves to increase timing during warmup.

Look forward to hearing how it works out!

prschmn

I think Nick is right on about temp vs timing. But keep in mind ign timing effects exhaust temp
and not so much oil. Oil temps more dependent on load and I'm wondering if you just need more cooling there.

Gus

Looked at and have built a new IGN table from what I could pull from Steve Wongs 3D and Full Throttle table plots. But am concerned about the relationship between the #D table data and the Full Throttle plot. IF you look at the full load on the 3D Chart ( the lines to the left ) starting at the lower RED at 58 LOAD/800?(RPM) and and compare that line to the FULL Throttle Chart - There are differences . If you look at the 3D chart from about 3100 to 5000 RPM is in the Green 20-30 IGN Advance range. If you look at the Full Throttle IGN Timing Chart(FTC) the only time that the timing is in this range is 2600 to 3700 RPM ( all numbers SWAGS, but close) But in the FTC from 3700 to 5000 RPM you are closer to 15 IGN Adv is is Quite different from the 3D Chart readings. So in trying to compare all this to come up with a starter IGN TABLE which way should you lean - less advance or more??? See table -

Gus

Here are some other IGN tables that I have/had developed over the past to compare

Gus

Hmmmm!!! That is an Excel sheet - here is a PDF

Gus

That did not copy correct - too many pages Hopefully here is a single

-nick

Hi Gus,
Steve's numbers are pretty similar to what I read out of the chip maps. The rpm scale on the PT map is different from the WOT map, and they have a different number of rpm point. So translation between them is less obvious. The WOT map can be thought of as the values for next PT load row after load=58.

Here are the numbers directly from the maps, from the last 964 chip revision ending in 7006. Sorry about the formatting.

PT load 58.6
rpm= 520 800 1120 1440 1600 1760 2080 3000 4000 4480 5000 5480 6000 6520
adv= -6.8 1.5 1.5 6.8 9.8 12.0 17.3 22.5 19.5 13.5 13.5 15.0 15.8 17.3

WOT map
rpm= 800 1000 1480 2000 2480 3000 3480 4000 4480 5000 5480 6000 6240
adv= -3.0 0.0 6.8 15.0 18.0 21.0 22.5 16.5 14.3 13.5 14.3 15.0 15.0

A couple others:

IAT Adv Retard Correction
degC= 20.0 36.7 53.3
advcorr= 0.0 -2.3 -4.5

CHT Adv Warmup Correction (I haven't tested this one, but it looks correct)
degC= -40.0 -6.0 58.7
advcorr= 21.0 5.3 0.0

I would only use these for a rough starting map in your pressure vs rpm table. There are a number of motronic timing correction maps that I haven't figured out the purpose of, which could come into play and change these base PT and WOT maps. Does vems have any knock feedback?

Also, varioram will increase the engine VE in the rpm range that it benefits but it would still show up as 100kpa (throttle wide open). You'll want to back off the timing, compared to the non-vario maps, in the range where vario is known to boost the torque.

Does vems calculate and populate a VE table? The VE at WOT would be interesting to see!

JasonAndreas

There is no easy way to directly convert between volumetric flow and absolute pressure. It's possible to hubble telescope your engine if you treat the 964/993 correction maps as throttle maps, the UOMs are all wrong.


The partial throttle maps are actually partial load maps (volumetric flow) and do not correspond 100% to throttle input (the above 58 number -from your screenshot- is incorrect, the horizontal axis corresponds to the maximum permissible fuel quantity for a fully combustible mixture in the engine as measured in milliseconds (You could derive a function for converting to cm3/min based on an idealized fuel injector but I haven't done so nor did I ever see one in any of Bosch's AFM patents). The 964 takes the derivative of the AFM signal to correct for partial to full and full to partial load transitions which is kinda like a relative throttle input but not really. If you are driving downhill with the throttle open halfway with the engine turning 3000RPM the ECU is not going to read values from dead center of the 2D table...




What are you using for feedback when you adjust timing? MBT happens at a ignition angles a few degrees before knock with 93 octane (USA) at intake temps below 90F in a 964 engine.

Use the auto-tune as a base and then add extra fuel where you need to cool things down. That is what Porsche did and what some aftermarket tuners seemed to have removed from their offerings.

Raceboy

If you run premium fuel there will be no knock until 27-28 degrees. We tested both types on the dyno on 964 engine. Over here regular is 95 (91 in US) and premium is 98 (93 in US).
Best power was at around 24-25 degrees at full throttle (100 kpa) over that power was dropping and before that too.

If you run too retarded ignition then you get hotter engine actually.

964/993 engine TDC vs missing tooth angle is 84 degrees if trigger tooth is set to 0.

Gus

Raceboy- So what you are recommending is an ignition timing of 24 -25 degrees advance in the range of 90 to 100 kpa at 6000 to 6500 RPM -
This does not match up with the 964 and 964 Euro Cup timing in that range of 16-17 (964) to 18-19 (Cup). See above posted charts first post "full throttle"pdf.. Are or were you running a retard setting else where in the program that retarded timing given certain condition??

Raceboy

Not just 6000 and up but from 3000 and up.

And what makes you think that factory cars were tuned to the max?

That is the whole reason behind standalone system, or chipping etc, you can tune the engine to have maximum output, not factory specified output.

At lower loads/cruise angle should be even more advanced to compensate for longer burn time of leaner mixture (remember, flame front moves at constant speed, it slightly depends on fuel used, boost etc but not much).

This was tested on the dyno, it is not just guesswork.

If you want I can send you a good ignition table but please verify that your TDC after the trigger value is correct in Primary trigger settings (84 degrees and Trigger Tooth set to 0).

Gus

Raceboy - YES, please send me a IGN timing table for 964. I am attaching copy of current timing just as a FYI. I am running a Varioram but do not believe that this has any significant impact on timing.
I have a Question on the VEMS ECU though - I can connect to the VEMS ECU when my engine is not running. But, shortly after I start the engine I will loose connection to the ECU. If I try to use the Auto Tunning it will just freeze shortly after I start to drive. The same when I try to make a LOG. Once in a while it will work for a little while as long as I do not get into higher RPMs. But there is no trouble connecting if the engine is OFF. I also have the LED display and it works fine, once I start engine it will display OK then after a while it will start to show all kinds of strange information, and then go blank or display only 2 solid lines.
Any IDEAS on what the issue could be - I have checked all serial connections and grounds, but since all is good until engine starts I am thinking there is some kind of interference coming from engine when it is running.