I figured since a couple of us were clogging up someone's thread, that it would be beneficial to start a thread discussing the pro's/ con's and theories behind advancing or retarding ignition timing and the effects it has on spool time. Ill go first :
Advancing the ignition timing increases cylinder pressure, which in turn increases the velocity and volume of exhaust flow into the turbine. It also increases the power output of the engine (prior to boost onset) to increase rpm's 'quicker'.
I believe that retarding the ignition timing in an attempt to increase exhaust temperature doesn't compare as exhaust flow and 'non boost' power are sacrificed.
Heat can be increased in either theory with leaning out the afr's, and I see where, with retarding the timing, a leaner afr 'could' be safely reached for more heat and possible power......

 

Oh god....

 

Ha.... figured id get everyone's opinion....... heat vs pressure... waiting for atomic to chime in

 

come on now guru. everyone knows timing is good, just depends how brave u are on how high to put it under the curve

 

Yes... that is my whole core with it. We were having a dicussion with atomic in another thread and he is under the impression that retarding ignition timing spools turbos quicker than advancing the timing simply due to heat

 

Best way to find out is get the car on the brake and start trying different strategies.

 

I was just messing with you.

I've found with automatics timing, timing, timing and leaner AFR's get the turbo to spool with heat, more cylinder pressure and exhaust velocity all at once.

With manuals dumping fuel and retarding timing in a no load application(clutch dis-engaged on the line) builds boost better from everything and everyone I've ever listened to talk about turbo's and spooling with manuals.

Will retarding timing and relying on heat spool a turbo? Probably, but the question is...how quickly? How long does it take for it to finally build enough heat just waiting on that one component to help it spool?

I dunno, but I know I'd rather use increased cylinder pressure, increased exhaust velocity, increased heat from leaning the mixture out all together at once to build my boost and get up and spooled quickly as in 3-5 seconds at the most from footbrake spooling to on the transbrake hitting the two step limiter waiting for the tree to drop not 3-5 seconds on the footbrake then bumping in to the beams, then grabbing the transbrake waiting for the tree to drop.

There are a million ways to skin a cat, but most cat skinners use timing timing timing and lean afr's, and some....once they have their spool limit boost met(footbrake) will retard the timing as a way to build more boost as sometimes once you get a certain amount of boost built at the rpm you have your spool limit set at(footbrake) it will flat line at that rpm and won't build anymore. To build more they retard it once they have 5-9psi built and good shaft speed to move the combustion process out of the cylinder and into the hot manifolds where the fuel then lights off closer to the turbine creating more boost.

 

I also use timing to increase boost and for me in a turbo application,(M6) I have tried to run it rich and it still had lag but if I leaned it out, with timing, the response was pretty good..

 

Was that on the starting line at the track or already under load moving down the road?

 

Correct. You can't really pull timing on an auto car as you need the timing to get you up on the brake the higher and faster that you can get on the brake, the better your chances of being at target boost when the tree drops. I do like to richen it up once you hit the 2 step in order to get that raw fuel igniting in the hot pipe to get the turbo sizzling fast.

 

He would be wrong.

Tuning and engine with abnormally low timing will just make it lethargic and slow whether n/a or boosted

the only time low timing assists spool is when the exhaust valve is still open. But that's a totally different scenario altogether.

 

Seems self evident that running overly rich will only make it harder for the engine to climb up through the rpms. And for racing-only applications it would seem to me that you'd want to get it light off good because in some cases you could be running some seriously cold spark plugs with barely any gap.

 

This is off the line, actually on a roll is easier at least for me...If a maf car you have to manipulate the scaling of the maf in the kpa range off the line, you also need to get into the PE tables because of % TPS that controls the fuel, % TPS that goes into the PE mode ect. I mean its just not plain and simple, it does take time to get it correct....

 

Martin is on point.

 

You have to understand Boost vs Load and Load vs Boost, Completely different..

 

LOL I know a little about tuning myself...thanks for the lesson though

 

Not ******* you, just info on what worked for me, A lot of people will say Boost is Boost, as you know, thats not true....

 

I was just kidding really.

No hard feelings here!

 

with out question the best way I have found with my clutch car is to pull all the timing out of it when I have the clutch pressed in. I have boost in an instant when I pull 20* of timing...

 

But again, this may work at the track, but how does it feel in a DD world when you don't hammer it at every light...