Need help understanding ignition timing

[morris]

Hi folks I was hoping someone could help me understand if, when and how you know you need to adjust the timing in an FI engine.

I am talking 1uzfe here, I have succesfully run 10psi on the engine with just an SAFC2 and larger injectors. Thta was with a Supercharger, now I am moving to a Turbo setup, I am wondering if I can still just use fuel managment. I need to know at what point do I have to start worrying about spark timing. How do I know if I need to start dealing with spark timing.

Thanks

 

[Lextreme II]

For the safe side. I run 1 degree retardation with 1 psi. So, i am retarding about 14.7 degrees with my current setup.

 

[chrisman]

lextreme is right, a good, safe starting point is about 1 degree for every pound of boost-when boost comes on.. but like you, i have FI on the 1uz, and have just run extra fuel..
although i have not run FI on the 1uz for a long time, i have noticed that the factory ecu will try and keep things on the safe side by retarding the timing.. or so i think-anyway..
we should get some more people to chime in on this..

 

[poid]

on the Honda i use 0.7 per psi retardation. But i am going to drop that to no change up to about 3psi, 0.25 degrees per psi to 5 psi and 0.6 up to 10psi. I would use the same on the 1uz

1 degree is a little on the high side IMO but is certainly safe

Also, the SAFC has the effect of advancing timing under boost (in the low boost range on MAP sensored cars in any case, i am not familiar enough with MAF sensored ECU's yet)

 

[morris]

So am I correct in understanding that there is no way to measure the need to add a device that will retard timing. You simply use a rule of thumb from .25 degree to 1 degree of retard per PSI of boost. If this is the case what is everyone using to retard timing, I have only seen the split second unit so far. It is supposed to do timing as well as fuel.

It is also my understanding that the 1UZ can retard timing, if it starts to sense pinging for instance from low octane fuel, I believe I read that it will retard timing to compensate for the lower octane fuel.

I'm sure it can only retard so much otherwise there wouldnt really be a need for an aftermarket timing computer would there?

Anyone have any idea how much timing (boost) the Engines timing Ecu can handle before we have to go to an aftermarket timing computer?


And thanks I am learning quite a bit.

 

[MaxPower]

The rule of thumb above is for a factory system that is designed for a specific boost level or in the 1UZ case is NA and does not expect boost. On a aftermarket ECU you can tune to whatever timing you want, just have to be very careful on how much.

Iam not sure on the knock algorithm of a 1UZ ECU but in a Delco system there is a maximum retard value (around the 10-11 degree mark depending on ECU) that the ECU can remove from the overall timing. It removes varying amounts of timing depending on knock counts, lots of knocking = lots of timing removed. The down side to the Delco knock sensing is the way it tests to make sure the sensor works - it dumps in 10 degrees of timing and checks for knock, if it gets none it trys again with 20 degrees. It does this at any time, light or heavy loads. The problem is u have just detonated the engine on purpose. Masking the error code disables this knock test routine but the code then skips the actual knock sensing routine. Newer models sense the resistance of the sensor instead which is much safer.

On a turbo car it is very important to tune with NO knock counts as it damages things very quickly. Best bet is to follow the above advise, however too little timing and the EGT's (exhaust gas temps) go through the roof. An overall timing of 5 to 15 degrees on mild boost (6 to 15psi) at WOT would be about as high and low as youd want. Obviously more boost on a stocker the less overall timing - as the advise above dictates.

 

[chrisman]

THIS is what tunning is all about.. getting maximum cylinder pressure at a certain time during the the power stroke.. things like getting a bad batch of gas can affect this--as well as bad tunning.. even outside air temp which affects the air density can affect the tunning of your car..
the oems have gone to great lengths to try and get it right--but usually stay on the conservative side of things.. a couple of degrees can make some power, but can also give you some probs..in any case, you should LEARN about your cars ecu and what it does.. then decide how to proceede..

 

[Lextreme II]

I think being on the safe side. 1 degree per psi. After that, you can do more fine tuning to miniminize timing and increase power. However, to start i think its a safe terrritory.

 

[morris]

so if we are tuning, how do you know to take out more or less timing, what do you use as an indicator? Lets say you start at 1 degree per psi, we know we can get more power if we reduce the amount of retard. Well if we are in deed tuning then we want to reduce the amount of timing that was taken out to make more power. How do I know what is a safe amount?

 

[poid]

what tends to happen is that if you are on a dyno, you'll see at some point that adding more timing no longer increases the amount of power you are getting. So for a safe tune, then drop it back a couple of degrees from that and you should be OK

 

[morris]

Thanks that answers my question nicely.

 

[morris]

okayy followup question.


do you just set the boost at X and then adjust the timing based upon that boost setting or do change both timing and boost trying to get more and more hp.

 

[Lextreme II]

Here is an example of Fuel Control (Map A)

Note:
10 is neutral
Less than 10 is decrease fuel
More than 10 is increase fuel

Here is an example of Timing Control (Map B)

Note:
0 is neutral
More than 0 is retarding timing by degree

This unit is activated by both rpm and pressure.

 

[Zuffen]

Morris,

If I were using a turbo I'd start on a lowish boost and get it running then increase the boost and work the ignition out as I went.

It depends if you were looking for max power by pushing the threshold of detonation or not.

If supercharging it's too hard change boost so you start with full boost and conservative timing and again slowly work your way toward the threshold of detonation.

 

[morris]

Lex that is a heck of a map, I am assuming that you have to spend a lot of time on the Dyno to set that up in the computer, it sounds like an expensive undertaking. Do you set up the map at every 1000rpms and then the computer fills in the rest or do you have to test and adjust the settings for every 500rpm? Is that the split second timing and fuel unit software you are showing


Zuffen thanks for the response when I finish up the forged low comp engine I think I will start at a safe boost level and then adjust timing, like you suggested, I cant afford the more aggressive approach of maxing timing and maxing boost. With my luck something would break. But 20psi or so should get me whree I need to be without being to agressive on the timing.

I would love to push it a little on my current engine but with the high mileage I am nevous that it wouldnt hold up to much more than 8-10psi. Even though the leak down and compression tests all check out.

 

[Lextreme II]

The boost and RPM increments are preset, but values are set by many ways. Auto or manually. You can increase or decrease by percentage or auto fill along with manual input.