Printable View
So here is the way it is calculated...
EOIT is X lo res periods (B3702) after the boundary (which is typically 6.5).
So...... 6.5 x 65 = 422.5 BTDC
Injector fires 5.5 (stock at normal coolant) after the boundary it means 6.5-5.5 = 1 x 65 Lo Res Periods = 65 BTDC.
Hope this helps.
do I read that as "(6.5ms - 5.5ms)*65deg/ms = 65 deg BTDC" ...? I'm not sure where the 65 comes from (and is it deg/ms...?)...?Quote:
Originally Posted by Highlander
I never said its ms.
Its lo res periods. One period = 65 degrees crank. Its a calibratable value.
Ah, lo res periods, not ms, I see, thanks.
Has there been a consensus on which direction to go with big overlap cams (20*+)? On one hand it looks like the goal is still to put EOT just before IVO. On the other hand there it does seem like a good idea to hold off until closer to EVC.
After listening to a pod cast interviewing Greg Banish, basically whatever slope (cold to warm) the factory is using, for cammed cars you continue with the slope. By this i mean the following, for LS1, the slope increases from cold to warm, therefore 'add' numbers. For E38, the slope decreases from cold to warm, so therefore 'subtract' numbers. For mild cams i start with adding 0.5ms to LS1 and subtracting 20* from E38, it's worked well so far for idle and low speed/rpm driveability.
Thanks for the info.
I want to understand how to use this spread sheet.Quote:
Originally Posted by Gelf VXR
Attachment 22591
Attached is my cam card.
How do I convert to what ever units I need to convert to?
I've been digging back into this lately and notice a discrepancy between the spreadsheet posted in this thread vs others on hptuners. IDK what's right and either way a calculator is only going to get you so close. There's different theories on whether or not it's better to advance the end of injection or delay the end of injection with big cam swaps... I think generally delaying is more well liked based on what I've come across.
Either way, your best bet is to probably do a little trial and error and see what your car likes. I am going to fully warm up the car to keep that variable constant, and then try increasing or decreasing B3702 value in 0.2 increments, datalog idle conditions and see how they look. I'm going to run closed loop, LTFT disabled and look for the setting that gives me lowest fuel trims, i.e. least amount of fuel required to maintain standard 14.7:1 idle. This should translate into what's most efficient for my new injectors, cam timing etc.
I just changed injectors and figured it was good time to dive into this before re-tuning the whole fuel map now. I'm using Deka 80 lb/hr injectors and a B3702 value of 5.35 at operating temp and with reasonable VE table values my fuel trims were +25-30 percent, so something seems off and I want to see the effect that injection timing has before just adding to the VE table. My values were changed to put injection earlier, but now I run a totally different style of injector so the theory of spraying fuel onto a hot valve to evaporate may not work out as well. If I want to delay my injection until after EVC (@ 0.050"), I need a value of ~5.6 or ~6.3 depending on which calculator I want to trust.
If someone has a better technique let me know!
Update, I did what I posted above and tried values of 5.55, 5.8, 6.0 and 6.2. Average idle pulsewidth varied by less than 0.005 ms and fuel trims varies less than 0.5%..... made absolutely zero difference.