Timing/fuel question

[TheBac]

If a tune has max pulse of 3100us and 28* max timing with stock injectors, would a similar tune with 30% injectors have a pulse of ~2200us and timing in the low 20s/high teens? Is that how it works?

Just asking so I can try to understand.

Been trying to figure out which timing table is the "main" table, too. A, B or C? The explanations that EFI puts in dont necessarily tell how or when a table is used. How do you know which one to modify?

 

[ZeroGravity58]

Timing table C is your main table. A is only used in very high altitudes. I always put the same timing table for both B & C and leave timing table A stock. Personally 3100 US and with 28 degrees timing is to low. I run a 2600 PW and 28 degrees max timing at 3800 RPM with 30 overs. But i dont claim to be a expert tuner either...Hope this helps

 

[TheBac]

Thanks ZG. B and C. I dont think my truck has ever seen 3800rpm racing. Most of the time, the trans shifts between 3250 and 3500.

I still have a stock turbo, too. I have to account for that, dont I?

 

[ZeroGravity58]

Yes C is the main one used at low altitudes. A is a very high altitude table. Im pretty sure most change both B & C to the same table so that at certain altitudes the truck doesnt bounce back and forth between two diffrent timing tables. 28-30 degrees is pretty good at that RPM. But diffrent tuners will tell you diffrent things. Some like high timing some dont. So far ive had good luck with my setup. I have over 20 passes at the track in the 11's

 

[wdino73]

I make A,B,C the same, that's just what I've learned, I'm running 45 overs with 85over cp3, at wot, i'm at 2450 pw an 28*, act rail prs. is between 23400 -24100, I don't hava a rattle, but I've got alot to learn, so this is going to be a very good thread unless some educated D.A. screws it up.... In my humble opinion...

 

[ripmf666]

B and C are changed in my tune. mine is at 2475 and around 34 deg timing and made 582 rwhp on Daves dyno but could not get it to load the twins.

 

[TheBac]

Cool. Ive got a decent idea where to start. Scary as it may seem, Im going to try to write a tune myself. Just want to start out conservative and find out what does what....but had to know where to start.

 

[wdino73]

Cool. Ive got a decent idea where to start. Scary as it may seem, Im going to try to write a tune myself. Just want to start out conservative and find out what does what....but had to know where to start.

I think everyone should try to write there own,, That's why this site is here for us to share what we've learned an know with each other, I know I don't know alot an I've broke alot of stuff, but I know what works now
If I can give u some advise, keep your stock tune handy an use it as a reference that's what I do...Good Luck, I'll try to help u if I can I'm working with limited brain power though:rofl:
The people on this site that know what to do an what works had to learn the same way from the begining...and for the most part they will help u I know they did me, so I feel responsible to help when I can just because of the help I've received....

 

[SteveFord]

I'd probably start with 2200-2400us of max pulse and max of 24-26 for timing. How you bring the fuel in along with timing will help spooling. I always thought the idea of bigger injectors with a stock turbo was to be able to bring the shot in later to keep cylinder pressure in check and help chase the piston down with the fuel burning rather than shoting it in to early and having it fight on its way up and cause higher peak cylinder pressures. You should get more of a complete burn and clean up the smoke better with the bigger injectors over stock ones. Guess it's all about what your really after... a max effort all out tune or a good powerfull tune that you can daily drive with no worries.

 

[TheBac]

Steve....you know me....what do you think Im going to do? :rofl:

Dino, something I was told when I first bought EFI was to save my stock tune in at least three places...just in case. I follow that advice, even though the OS is in the tuning library.

 

[SteveFord]

Steve....you know me....what do you think Im going to do? :rofl:

Dino, something I was told when I first bought EFI was to save my stock tune in at least three places...just in case. I follow that advice, even though the OS is in the tuning library.

Going for that 11 second stock turbo fuel only slip I want to see you do it:thumb:

 

[wdino73]

Steve....you know me....what do you think Im going to do? :rofl:

Dino, something I was told when I first bought EFI was to save my stock tune in at least three places...just in case. I follow that advice, even though the OS is in the tuning library.

No, what I mean is have it on your computer, an sometimes I'll do a split screen with the stock tune an the tune I'm woriking on , an use the stock tune as a ref, looking at how GM did it,, see I'm alittle slow until I get in my truck.... LOL

 

[TheBac]

So I modified B0720 and B0721 with a max of 2400us from 110mpa on up, and left all the rest of my fuel tables alone. Everything lower than 10mm3 is stock.

Then I went into Timing B and lopped 25% off everything higher of 60mm, and 20% off all lower than that, with timing at 3600rpm (the highest Ive ever seen on my truck) of 26.9*. Copied that table to Timing C, and left all the other tables alone.

Went out for a test drive and scared the crap out of myself. The truck spun in 1st, and barked the tires in 2 and 3 and boost came on almost instantly. Wow, never done that before.

I should probably take out more timing. Maybe another 10% might be wise?

 

[ZeroGravity58]

that timing doesnt sound to high to me. Right about where im at.

 

[SteveFord]

run it and see where the egts are at when you hit x mph. Take a few degrees out and see if it gets hotter or stays the same. I think your ok for max timing but if it runs the same with a little less than you can adjusted from there. What you really need to do is take her to the track!!!!

 

[SteveFord]

Also being you have a better rod now I wouldn't be as worried about the timing if the motor isn't "loud".