Injection Timing Help

[benno25]

Hi,
I'm having some problems understanding some of the injection timing spreadsheets that people have posted up in other threads and are unsure as to what values to use?

My car is an LS3 with an LS1 pcm and has a comp cams 227/243 113lsa cam in it. Specs found here
http://www.compcams.com/Company/CC/c...csid=1427&sb=0

Currently my boundary is set to 6.5
Normal and Makeup tables have maximum values of 5.55 in them.

Can someone help as to what values I should be changing these to?

Thanks
Benno

[Higgs Boson]

Change Normal and Makeup to 6.1 and see how it works.

[benno25]

I changed the normal and makeup values to 6 and slowly increased them up to 6.6
I found my AFR got richer and richer up to about 6.4 so I set my normal and makup values to 6.35
The car seems a little more responsive but is hard to tell and it sounds a little better at idle in my opinion.
I still have lots of bucking under 2000rpm so will have a play with timing in the light load areas and see how it goes.

Cheers
Benno

[Higgs Boson]

You should also retune your VE and MAF.

[benno25]

I'm running open loop SD and have tweaked VE to get AFR's close to where they should be.

Whats the norm for getting rid of bucking these days? I've heard a lot of people add timing and have also heard of people reducing timing heaps in the low load areas to help settle things down?
Also what kind of AFR's do people find help? I find I get a fast kind of bucking if the car is too lean in one area. If not I seem to get more of a surging type of bucking if that makes sense?

Cheers
Benno

[Higgs Boson]

First get your timing set to one value (like 22 or 25 or 29 or something that works for your car) in and all around your idle cells. Smooth that little timing island into the rest of your map (and make sure your timing map is smooth in general).

Then get it idling at stoich.

[benno25]

I have so far tryed running around 22-25 degrees timing in the low rpm low load areas and didn't have any luck, car still bucked and surged like crazy.
I then dropped the timing to around 17 degrees and things seem a little better. I can now drive along in first at 1800rpm however anything below that starts bucking/surging. It does seem a little better than previous though.
Also when lifting off the throttle and letting the car slow down, it will start bucking like crazy once at about 1600rpm or less.
I think my fueling may be a little inconsistant in these areas so will check this from the log later and clean things up a bit and see how it goes.

Cheers
Benno

[benno25]

Also, just remembered I have never done a case learn on this new motor so will try and do one of them and see if it helps things.

Cheers
Benno

[Darkstang5887]

I'm having all the same problems as you, try playing with the throttle cracker, follower

[benno25]

I'm having all the same problems as you, try playing with the throttle cracker, follower

I'm not sure how the cracker and follower are going to help? I'm trying to elimate this bucking and surging at a constant load and rpm. I can't see the difference between holding a constant 5% throttle cruising with the IAC closed up, or 3% throttle with the IAC open more due to different cracker and follower settings? Hope that makes sense.

I tend to think its just a matter of having the correct amount of timing, fuel and injection timing to smooth things out or minimise it?

I may be missing something here though so appreciate hearing what others have found works.

Cheers
Benno

[LSxpwrdZ]

Judging by the cam spec's you gave I'm guessing the intake centerline is around 109-110? If so that gives an EVC point of around 366-367*. That point is where I start from on all tunes and it's seemed to have worked wonderful on all the car's I've been working on. The physics don't make sense as to why it would run better but if you think about it this way, the fuel being delayed on injection nearly 67* crank rotation then it sheds some light on keeping some of the fuel from escaping out of the exhaust during overlap which is what causes bucking and fuel smell. It makes sense that the fuel mixture get's richer when you are keeping that fuel in the chamber instead of letting it excape out of the exhaust. So a person could almost keep adding small increments to normal and makeup tables until they reached the maximum rich point and leave it there. Like I said I've been using the EVC point at .050" and it's been working great for me.

My spreadsheet gave me a starting point with that camshaft of around 6.5 boundary and 6.29 in the normal and makeup tables.

[benno25]

Judging by the cam spec's you gave I'm guessing the intake centerline is around 109-110? If so that gives an EVC point of around 366-367*. That point is where I start from on all tunes and it's seemed to have worked wonderful on all the car's I've been working on. The physics don't make sense as to why it would run better but if you think about it this way, the fuel being delayed on injection nearly 67* crank rotation then it sheds some light on keeping some of the fuel from escaping out of the exhaust during overlap which is what causes bucking and fuel smell. It makes sense that the fuel mixture get's richer when you are keeping that fuel in the chamber instead of letting it excape out of the exhaust. So a person could almost keep adding small increments to normal and makeup tables until they reached the maximum rich point and leave it there. Like I said I've been using the EVC point at .050" and it's been working great for me.

My spreadsheet gave me a starting point with that camshaft of around 6.5 boundary and 6.29 in the normal and makeup tables.

Correct, intake centreline of 109 degrees.
I will try slowly bumping up the normal and makeup tables and see if I get any less bucking or see if the AFR changes further.

Cheers
Benno