Boost Timing Issues

[gpr]

Trying to get the timing set correctly, but i ran into a slight issue. Because of the altitude my map reads about 12.3psi key on engine off. The issues are that the columns for Boost VE table and Boost timing table start at 15.2psi, at this point i am already making about 3psi of boost.

This is my first car tuning on boost, but i wanted to remove timing slowly till i got up to full boost ~8psi for now). The problem I'm having is if i pull like 5 degrees of timing out at 15.2 (3psi boost) there is a sudden drop in timing. it is not scaling the timing when moving from table to table like it does moving from cell to cell in one table.

Do i simply pull timing from the high octane table so it is lower when it enters the 15.2psi map reading and is a smoother transition?

People always talk about the timing they have on their engine, but it is at 100% throttle and max boost. How much timing is safe to run at lower rpms and lower boost levels before you hit full boost?

[gpr]

Also is there any collection of tune files for modified vehicles, sorta like the tune file depot site? I'd like to see what other people are doing with their cos5 as far as timing etc... on boosted applicattions

[ferocity02]

I've been using the high-octane table to control timing in boost. It just uses the last column most of the time.

[gpr]

So when not in boost do you use the factory high octane table? then once in boost the last column is the final timing, minus whatever you take out of it in A0010? Also i see people run 12 -15 degree's of timing, i take it that is the timing use at peak boost and is slowly brought down to that as boost increases? or should you set it up at 12 degrees of timing anytime you are in boost?

[johnv]

give us a few more details on your setup.
what sort of forced induction ?
Is engine stock or forged ?
what year ?
have you set up your 2 bar sensor to match the same map reading at key on engine off as your factory Map sensor ?

[gpr]

2002 stock ls1 with head studs and a cam (cam was in car when i got it). Front mount turbo kit with front mounted intercooler. I have a 3 bar map sensor and do have it set to read the same as the old map did at this altitude. it reads about 12.2-12.3 at this elevation with key on engine off.

Oh and I'm running on e85. wanted to be careful turning up the timing so i don't detonate it, don't want to take out the engine. The wastegate spring is 8psi for now. just want to get it tuned and running good then will turn up boost slightly, maybe go to 10psi or so with a boost controller.

If anyone could post their timing table I'd appreciate it. Just like to look at what others are running timing wise.

[gpr]

I've been using the high-octane table to control timing in boost. It just uses the last column most of the time.

So instead of using the Boost timing table, zero it out and control timing with only the high octane table?

I'm guessing once you are off the chart on the high octane table, that it will use the value in the last column at the corresponding rpm?

[ferocity02]

So instead of using the Boost timing table, zero it out and control timing with only the high octane table?

I'm guessing once you are off the chart on the high octane table, that it will use the value in the last column at the corresponding rpm?

Yes that's how it works. So the logic is that you will never use the right-most portion of the high-octane table in a NA application unless it's a big motor. But with bosot you can hit the right side of the table, so the right side of the table is almost like a boost timing table. It's also nice to have your final timing defined on just one table rather than having to subtract values to get your final timing. This is how my tuner set it up for me so I stuck with it. I'm sure using the boost timing table would work just as well and gives you an extra dimension of adjustment. One downside of my method would be that you can't adjust timing vs. airflow once you're over 1.20 g/s. So if you're really trying to optimize your setup then the boost timing table would certainly help.

[gpr]

I went and changed it around to use the high octane table only like you are talking. then i used the boost timing table as a safety net. Put values in to start subtracting timing at boost levels over what my waste gate opens up at. A fail safe if my waste gate or something goes wrong and boost spikes or creeps up to high.

thanks for the help!

[johnv]

Sorry havn't been back here for a week, I run pretty close to NA timing in the high/low oct tables and use the boost timing tables to remove timing in boost.
Maybe hook up a boost gauge and see what MAP reading is when you start to see boost.
Why the 3bar sensor if your only gonna run 10 psi, you should be able to run 15 psi on a 2 bar sensor and have better resolution in your fuel and timing tables than the 3 bar sensor.

Post a tune up and some current logs.