if i ran between 10-15psi on my 99z24, would i have to retard the timing at all or will it be fine
well, i was just reading some info on the megasquirt pages about timing, and boost, they recommend .3 degree change for every 1Kpa above atmosphere. so, if atmosphere is about 100 kpa, then for every kpa above it, you would retart timing .3 degrees.
using google's converter, 10 psi is 68.9 kPa so, 68.9 kPa * .3 = about 20 degrees retard. Now, this is all just what i read. I can't confirm if for our cars, it needs it, or if the ecu will take car of it for us. but, this is suppose to put you close, and then u'd need to tune from there. so, for about 10 psi, you'd need about 20 degrees retard.
Can anyone else confirm or deny this? I'm curious to hear some actual insight from people who do their own timing.
There is no right answer, it is all about your setup. Basically, if you arent knocking(detonating) then you dont NEED to retard it at all. But, to be safe you can retard it a bit. It all depends on your motor and setup, and what fuel you are using. Hell, run 130 octane and advance the timing 20 degrees
There are many times when the engine will knock and you won't know it from behind the wheel. When knocking is bad enough for you to hear it, then it's really bad. Waiting until you hear knock is not the best way to help your engine live a long and happy life. Adding boost means increasing cylinder pressure, which means decreasing the time it takes to burn the air:fuel mixture, which means retarding timing.
Short answer, I wouldn't even try it without changing timing. 2 degrees timing retard per 1 psi boost is a number that I've used before, too.
-->Slow
I know what you are talking about slow, your deffinatly right, any smart person would take some timing out of it if they were boosting, I was just clearing up the fact, you dont NEED to take timing out, its not a necessity, it only depends on how safe you want your setup to be, and whether it is actually knocking. The sole purpose to taking timing out of it is so it doesnt pre-detonate.
So on stock compression and higher than 10psi, like 14psi retarding the timing will help prevent it from knocking. Doesn't the heat also rise??? Someone told me you can melt stock internals with higher than 7psi in a cavalier on 91 gas.
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Someone told me you can melt stock internals with higher than 7psi in a cavalier on 91 gas.
You can melt stock internals with 0 psi on 91 gas if the tune is wrong. The combination of stock compression and 14 psi will be much more sensitive to a bad tune than lower compression or lower boost. With forged internals, if you make a mistake you may get a second chance, But with that much boost on a stock internal engine you'll be pretty lucky if you get another shot.
-->Slow
So if your ecu is calibrated how much boost can you take on stock internals, theoretically?
I have the ability to recalibrate my stock ecu, i'm just worried about boosting it unhealthy-wise for the track. Our boost on normal in town will be between 4-7 boost.
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So if your ecu is calibrated how much boost can you take on stock internals, theoretically?
Theoretically, there's no definite answer.
Depends on the fuel you use.
Depends on the condition of the engine.
Depends on how long you'll be applying boost for.
Depends on how you drive.
Depends on intercooler and turbo efficiency.
Depends on the cylinder heads.
Depends on the oil pressure and volume.
Depends, depends, depends.
I feel I'm pushing things with 8 psi non intercooled on a used 1994 2.2 OHV and 87 octane fuel. I spent a bunch of time to work out a cal that would let the car live. Any increases in boost and I'll be moving up to higher octane fuel, maybe add an IC.
BTW, lived in Hardin SE of Billings for 5 years. Brought a Chevelle back that had spent many years in Glendive. I intend to move back maybe to Whitefish/ Kalispell some day.
-->Slow
Pull timing and be smart. Bottom line.
I pulled zero timing at 15psi on my stock motor and it was just fine... but I was running overly rich (never got a chance to dynotune it)...
In all honesty 2 degrees per psi is a bit much... but every motor is different. The only way to truly get an idea is to hook the car up to a scanner and run it on the dyno and watch the knock sensor and adjust your timing accordingly. To be safe it never hurts to pull too much timing, it mostly just costs power.
I'm not talking pull 20 degrees for 5 psi either. Pull a few degrees to be safe but get it up on a dyno with a scanner and see where you're at and tune accordingly. Ideally you don't want to have to drown out the motor with too much high octane fuel to combat knock... pulling a tidge of timing and running the appropriate air/fuel mixture is your optimal setup.
Oh and keep in mind the temperature when you tune, please. A hotter day will have a hotter combustion chamber so always give a bit of leeway for the motor to compensate on stupidly hot days.... we can't always control every variable but we certainly can keep them in mind when we tune.
Good luck.
-Chris-
-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
Chris hit that one on the dot^^^^
don't forget that every degree of timing advance also increases cylinder pressure.... and there is a point where more advance will continue to make more pressure (and more stress on parts) without any measureable power gain. So just because the stock computer isn't pulling timing at your current settings, and isn't detecting knock, doesn't mean that your timing is "good".
Since all of the J engines were tuned for 87 octane, that gives a good bit of leeway for boost on stock timing with 91 or 93 octane... For 5-6 psi, i don't think I'd worry about timing as long as you have a turbo thats well matched to the engine, and a good intercooler. Once you start getting up above that, a moderate amount of timing retard is probably in order.
I think that this is where most J-owners go wrong when they start boosting a motor... It seems that everyone is so hard-up about a/f ratio and seem to completely forget about timing... Obviously a/f ratio is important, but timing runs a very close 2nd, too close to just ignore it entirely while trying to make 300 hp out of a motor with a timing curve meant for 140 hp on 87 octane....
Arrival Blue 04 LS Sport
Eco
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Megasquirt
'Nuff said
Scarab I totally agree with you, and I neglected to mention what you pointed out so thank you for that.
Not only are most J-tuners hard-up on airfuel ratios, they totally forget how a motor works... beating the hell out of the motor with too much fuel robs it of power, wastes gas, and wears parts prematurely.
The biggest problem with these motors is that people forget the most important thing of all: combustion chamber temp. Sure you can drown it with fuel but... if you get the fuel right and the timing is not right, the temp in the combustion chamber will be way up... ideally this is why people tell you to tune with both a Wideband A/F and an EGT... because you need to find both of the sweet spots for both of those categories.
Ideally I'd rather pull too much timing and run a better airfuel ratio (10.1:1 is a freaking joke).... I can always slowly advance timing and see how things are. The minute the knock sensor starts to pick up knock though you have to realize that you're not just 1-2 degrees too far advanced, you're quite a few degrees too far. So back it up and be safe.
People on this site are blowing built motors or detonating the hell out of them without really knowing. I am seeing so many built motors making weak #'s and the reason isn't the parts... it's the lack of tuning and tuning knowledge. I wish we had a better resource for our PCM's but all I can say is get a concept of how other platforms handle tuning and carry over whatever basics you can and get to know the specifics of our PCM's and how they handle things.
You will be pleasantly surprised with 15-20 whp / psi efficiency if you get it right.
-Chris-
-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
