ammuscleftw

Is it ok to run a flat say 28* on the timing table? Isnt this the way old school motors ran? would this just affect the fuel mileage and emmisions.. or are there other reasons the stock table has such high numbers in the lower vacuum areas as well as the low numbers in the low rpm / high vacuum area... Just a curious question..

Gh0st

iTrader: (3)

you don't do that

ammuscleftw

lol i expected that response... but why is my question. On the older motors the timing was set at one number mechanically.. correct? just wondering what the difference was and why the tables jump around so much on a fuel injected car.

5_02ls1

iTrader: (20)

i tried this awwhile back and the car was really sluggish at part throttle......if your wanting a milder timing curve look at the ls6 tunes......but putting all colums and boxes to one set number the car will drive like crap,,,,,

ammuscleftw

ok thats what i thought.. that part throttle would suffer. Thats what i was looking for was someone who has tested this and the outcome. Im assuming that this is why they are not set mechanically at one number any longer either and you get the added benefit of better control of fuel economy ect...

JDMC5

iTrader: (3)

Old cars didn't run that way. They had a mechanical and/ or vacuum advance.

Engines likes more timing at high vacuum/ low load because the a/f charge is less dense therefore the burn rate is slower. (there are other reasons but thats the basics)

ammuscleftw

that makes sense thanks for the info, i was curious and was sure there were good reasons it was set this way and have never really seen anything posted on this.

Rocko350

Also take note that as an engine reaches its power potential it needs less timing to complete the burn cycle. Many inadvertently have too much timing and too much fuel. The timing curve will have a high at peak torque so to speak and a low(er) swing when the engine reaches peak hp.

JDMC5

iTrader: (3)

N/A engines are at their peak efficiency at peak torque. More efficient combustion requires less timing. As the engine revs past peak torque more timing is needed because efficiency (and cylinder pressure) is dropping and rpms are increasing (the piston trying to "run away" from the flame)

FYI......the dense a/f mixture of Forced induction/ high compression and the swirl effect (mixing) of efficient cylinder heads all require less timing also.


So the moral of the story = timing (on an N/A engine) is dependent on rpm and efficiency. You have to remember on an FI engine heat becomes a big factor on how well it will tolerate ignition timing.

Someone correct me if I left something out.