[Diy_efi] Timing Advance Curve?

[Dave Dahlgren]

Help me here. How can you reach the ping limit before the torque limit. If it
pings you are at the torque limit for the fuel you are running. Are you saying
that if you had better fuel it would not ping and therefore make more torque.
Seems nonsensical. I have tuned the Mazda Miata engine for SCCA GT racing.
Granted we had good fuel but as a restricted engine best power on a water brake
dyno was at around 32 degrees. You could put more in it but no power came out.
Why bother carrying a load of timing if it does not make the torque meter go up.
It might have a couple of more degrees in first and second gear only but that
would probably be the end of the mapping changes from the dyno. From the years
of dyno time I have logged you could always slowly add timing to the point the
power did not go up if you added a degree or two more it stayed the same and any
more it goes down. The place in my mind to stop is the point where it adds no
more power not the place where it makes no difference. You can always add a
little in the lower gears to make the car snappier and then still be fine for a
top gear pull on a long straight.
Dave

"Geddes, Brian J" wrote:
> 
> I was already thinking that what you describe below was true - good to get confirmation.  I'm running a '90's designed 6-cylinder turbocharged engine (6G72, Mitsubishi 3000GT VR-4) with over 1 bar of boost, so I'm guessing that I'll reach the ping limit at boost well before the torque limit.
> 
> - Brian
> 
> Further a few words to timing advance. Engines of newer conception (4V, =
> central spark plug, CR~11) will have at loads lower than 50-70% their =
> best advance before "pinging". At full load, knock limit is always the =
> best.
> 
>                 --- so long ---, klaus.
> 
> There also remains a problem with late model 4valve engines in that some of
> them hardly detonate at all! I have seen Mazda MX5 (Miata) engines on the
> dyno which don't ping, or at least give no indication of pre ignition
> audibly with well over 40 deg advance, WOT and max. torque. The only
> indication was a drastic reduction in power.
> 
> I have also seen one F3 engine builder destroy dozens of Mitsubishi engines
> (4G63 I think) before they got the timing right. Part of the reason was that
> the dyno guys had trouble figuring out where the ping limit was. Then when
> they installed the engine and it was subjected to ram effect through the air
> box, Kabang! Admittedly, these engines run air restrictors and CR's in the
> region of 13:1, so getting the ignition map right is an art form in itself.
> 
> The really clever engine builders (Neil Brown, Speiss Tuning) use the method
> prescribed by Klaus. But the cost of the test equipment is horrific.
> 
> Just a word of caution for anyone trying this theory with modern 4valve N/A
> engines, that's all.
> 
> _______________________________________________
> Diy_efi mailing list
> Diy_efi at diy-efi.org
> http://www.diy-efi.org/mailman/listinfo/diy_efi
> 
> _______________________________________________
> Diy_efi mailing list
> Diy_efi at diy-efi.org
> http://www.diy-efi.org/mailman/listinfo/diy_efi


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi