| View previous topic :: View next topic |
| Author |
Message |
Raize
Joined: 18 Sep 2013
Posts: 181
Location: Scotland
|
 Posted: Sun Apr 14, 2024 3:09 am Post subject: Ignition Timing Map |
 |
|
Anyone have any comments on whether this would be a good ignition timing map for a N/A 2.0 with boost? Assume AFRs are done properly, Euro compression ratio, and intercooling. |
|
| Back to top |
|
 |
Cedric
Joined: 27 Aug 2004
Posts: 2609
Location: Sweden
|
|
| Back to top |
|
|
Raize
Joined: 18 Sep 2013
Posts: 181
Location: Scotland
|
| Posted: Sun Apr 14, 2024 5:06 am Post subject: |
|
|
UK 99 RON which would be equivalent to USA 95 |
|
| Back to top |
|
|
924RACR
Joined: 29 Jul 2001
Posts: 8806
Location: Royal Oak, MI, USA
|
| Posted: Sun Apr 14, 2024 9:38 pm Post subject: |
|
|
US-spec 931, but here's my ignition map (from the Megasquirts experts thread):
I'm not sure why you would want such high advance of 52 on high vacuum/rpms?
The low RPM values around 6-8 degrees control the idle speed, with the very high advance at 600rpm to keep the car from stalling.
I have actually massaged things a bit since the above was posted, but this should give a decent baseline... there were a few discontinuities that needed to be sorted, mainly I think it was the progression from the 45 to the 80kPa line, and from 1500-2000rpm - that was a bit of an abrupt jump, so driveability around 2000rpm and light throttle in stop-and-go traffic got pretty jumpy and unpleasant.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
|
| Back to top |
|
|
924RACR
Joined: 29 Jul 2001
Posts: 8806
Location: Royal Oak, MI, USA
|
| Posted: Sun Apr 14, 2024 9:52 pm Post subject: |
|
|
Update - posted my latest maps, so linking from the Rennlist thread... tuned for US 93 octane gas (though far from the limit, I have a WBO2 sensor but no knock sensor and haven't run on a dyno, just street tuning).
Boost is set at 14psi...
You can see the difference in the ignition map for smoothing vs. the previous one. Much happier and smoother in stop-and-go traffic at 2000rpm.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
|
| Back to top |
|
|
Raize
Joined: 18 Sep 2013
Posts: 181
Location: Scotland
|
| Posted: Sat Apr 20, 2024 9:53 pm Post subject: |
|
|
Thanks for the data.
Couple questions:
1. You have all your timing in at 2500 RPM from 85 KPa upwards. I was going with the stock Porsche ignition curve being all-in at 3000-4000rpm, are they too conservative?
2. What's the purpose of the retarded timing below 3500 RPM at high vacuum (55 KPa and upwards)? I understand the 6 and 8 part is for idle control, is the 16-25-30 just smoothing?
3. Is it generally knock-limited or MBT-limited with the gas you run? |
|
| Back to top |
|
|
924RACR
Joined: 29 Jul 2001
Posts: 8806
Location: Royal Oak, MI, USA
|
| Posted: Sun Apr 21, 2024 9:24 am Post subject: |
|
|
| Raize wrote: | Thanks for the data.
Couple questions:
1. You have all your timing in at 2500 RPM from 85 KPa upwards. I was going with the stock Porsche ignition curve being all-in at 3000-4000rpm, are they too conservative? |
I'd say so. But I'm tuned for much better octane too. Plus we have better controls, more precise, more complex and reliable, etc.
| Raize wrote: |
2. What's the purpose of the retarded timing below 3500 RPM at high vacuum (55 KPa and upwards)? I understand the 6 and 8 part is for idle control, is the 16-25-30 just smoothing? |
Exactly.
| Raize wrote: |
3. Is it generally knock-limited or MBT-limited with the gas you run? |
I'm not knock limited or anything of the sort; this is a conservative tune that doesn't run to the limit, since I haven't dynoed or run any knock detection.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
|
| Back to top |
|
|
Raize
Joined: 18 Sep 2013
Posts: 181
Location: Scotland
|
| Posted: Sun Apr 21, 2024 7:48 pm Post subject: |
|
|
| 924RACR wrote: |
I'm not knock limited or anything of the sort; this is a conservative tune that doesn't run to the limit, since I haven't dynoed or run any knock detection. |
That's good to know. The only data I have for my car is that on 99 octane (USA 93) it starts to lightly knock at 36 degrees timing and on 97 octane (USA 91) it starts to lightly knock around 32 degrees timing, at 120 KPa.
The NA obviously has higher compression than the 931 so would need less timing because of that. But equally, it has a worse combustion chamber shape that requires more timing than the 931.
Also not sure if there's a pressure level where the engine will just knock because of the high-ish 9.3:1 compression ratio and no amount of ignition timing retard will change it, and what that pressure would be for an intercooled NA running premium gas. |
|
| Back to top |
|
|
924RACR
Joined: 29 Jul 2001
Posts: 8806
Location: Royal Oak, MI, USA
|
| Posted: Mon Apr 22, 2024 9:11 pm Post subject: |
|
|
I'm surprised that your motor will knock that easily. Doesn't seem right, perhaps it wants some clean-up in the combustion chambers?
We also have an NA racecar, with a basically stock NA head on it, used to run 9.5:1 compression with stock cam, 93 US octane, and no problem running up to 42 degrees of compression (max power) as long as the fueling's good.
So on that latter point, how is your fueling, do you have a wideband?
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
|
| Back to top |
|
|
Fifty50Plus
Joined: 28 Feb 2008
Posts: 1356
Location: Washington DC area
|
| Posted: Mon Apr 22, 2024 11:38 pm Post subject: |
|
|
What Vaughan said above. I had the same thing (9.5:1 with 93 Octane) at 41 degrees and ran a CO of 12.6-13.1 with no knock. Now we both have 11:1 compression engines (I'm running 100 Octane) and a bit less advance with no knock.
_________________
1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car |
|
| Back to top |
|
|
Raize
Joined: 18 Sep 2013
Posts: 181
Location: Scotland
|
| Posted: Tue Apr 23, 2024 5:50 am Post subject: |
|
|
I have 14-14.5 AFR so it's not ideal.
Will be reducing this to around 12 soon. Should be able to pick up some more timing with that change. |
|
| Back to top |
|
|
Fifty50Plus
Joined: 28 Feb 2008
Posts: 1356
Location: Washington DC area
|
| Posted: Tue Apr 23, 2024 7:13 am Post subject: |
|
|
12 is too rich unless its turbocharged...
_________________
1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car |
|
| Back to top |
|
|
Cedric
Joined: 27 Aug 2004
Posts: 2609
Location: Sweden
|
| Posted: Tue Apr 23, 2024 5:20 pm Post subject: |
|
|
| Raize wrote: | I have 14-14.5 AFR so it's not ideal.
Will be reducing this to around 12 soon. Should be able to pick up some more timing with that change. |
12,7 at n/a for max power and then lower as boost goes up,how much depending if you use a supercharger or turbocharger.
One thing here, never use any ones ignition map other than for reference to build a rough map, things can be a bit different between setups for a multitude of reasons, start a bit conservative and work yourself up.
_________________
1980 924 Turbo
www.instagram.com/garagecedric/ |
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
924 FAQ (Technical)
