Yes, but when you want to experiment with different values... it helps to know if you're even in the ballpark.Originally Posted by aaronc7
What are your cam specs?
Yes, but when you want to experiment with different values... it helps to know if you're even in the ballpark.
What are your cam specs?
226/230 113 +2. IIRC, IVO 357* and EVC 359*. I did use the calcs to get in the ballpark, there is just a discrepancy in the one posted here vs most others on hptuners. Either way I saw virtually no difference in fueling by retarding injection timing by up to ~60* which I find surprising, but it's what the data says.
Yeah, but think about where that ~60* is.
5.55 is 60*BTDC
6.2 is TDC
Hmmm.... your comparing spraying on a closed valve to spraying on a closed valve. I wonder why it didn't make any difference?
The correct way to calculate EOIT was figured out experimentally by Bluecat about 8yrs ago.
https://forum.hptuners.com/showthrea...OI-fuel-timing
Enjoy!
The calculator actually said I should go to about a ~6.3 value, I guess perhaps I should actually try that as it would be slightly after TDC. I have read that thread and understand the formula. Even in this thread there seems to be some disagreement on the formula and 'reference period', but the bluecat thread was the most conclusive thing I've come acrosss
edit: A value of 6.3 should start the inj pulse at 360* and end at 368". I'll try values of 6.3, 6.4 and 6.5 and see if it makes any difference
Last edited by aaronc7; January 16th, 2019 at 05:30 AM.
Bluecat proved experimentally how injection timing is calculated. I don't understand why some people on this forum have other ideas, but Bluecat's formula is correct... and contrary to what some people on this forum think, a reference pulse is actually 90 degrees. You can use the same principle to calculate Gen4 EOIT. The main differences being that Gen4's use crank degrees and they calculate backwards from the boundary where Gen3's calculate forward from the boundary... and yes, the stock timing is the same for both.
Thanks for your comments and thoughts, I'll follow up my little experiment. With these new injectors, I am needing pretty high idle VE values, so I have been digging into injector data to include this timing stuff, before proceeding further.
Well, I did the same test for 5.55, 6.2, 6.3 and 6.4. I dialed in my VE table so trims were spot on with the 5.55 settings. I had identical results again across the board for all injector timing values. Average fuel trims varies about a couple tenths of a percent and IBPW by .005 or so on average. Perhaps my cam is just mild enough and does not have have enough overlap to see benefit in this.
That's exactly right.
I can see that you like to experiment and find things out for yourself, rather than just accepting what some random idiot tells you on the internet... which is why I helped you down the path to what might seem like a dead end, but at least now you know how to calculate EOIT and you've proven to yourself that spraying later doesn't have any benefit with your cam.
The real benefit is for pure race cams... and the benefit shows up as a reduction in ET over the 1/4 mile.
You are right that I don't like to just accept whatever I read online as fact...actually so much misinformation that just gets parroted and before long everyone is an expert and it's a 'fact'. What's interesting is over on hptuners forums you see plenty of guys who have a cam with similar specs to mine and claim this made a big difference, etc. Maybe faulty test measures, I made sure IAT/coolant/oil temp were as consistent as possible.
Either way, I'm glad to have worked thru this and press on with the tune.
reminder to self: brush up on eoit calc.
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