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EOIT for Gen 3 and overlap

Old 01-11-2018, 01:11 PM
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Default EOIT for Gen 3 and overlap

I have been searching through here and HP tuner and have learned a lot about EOIT but most of it is for Gen IV. The tables and number is different. I tried to back into the calculators but it doesn't make sense.

Fortunately, the Gen 3 is pretty simple. Here is what I did/assumed.

02 Stock cam BTR Stage 2 Turbo (226/232-113+4)
IVO 9.5 ATDC IVO 5 BTDC
IVC 36.5 ABDC IVC 43 ABDC
EVO 37.5 BBDC EVO 53 BBDC
EVC -20.5 ATDC EVC -1 ATDC
OL -30 OL 4

EOIT Boundary stock 6.55
ECT ranges from 2.55 to 5.55 at RPM

So to keep the same valve train dynamics I wanted to adjust the boundary.
6.55*90 ~ 98 = 98 BTDC right? = 262 Boundary
Now subtract the Normal 6.55-5.55 = 1 = 15degrees BTDC
This makes sense? So normal the injection should start around 15 BTDC and complete around TDC or a little later which is still before 9.5 ATDC IVO stock?

New cam is 14.5 earlier (9.5+5) so I subtracted from 6.55 and got 5.58
This backs things up and it worked great. Car idles much better.

I wasnt sure how to handle the overlap but I assumed that if I back it up 14.5 I should always be the same dynamics and the boundary - normal should always put the injection complete before the IVO opens and hence overlap issue goes away? I tried adding the 4 deg overlap back in at 6.0 and it ran ok but didnt sound as great and had more fuel smell.

I left the ECT 5.55 values alone. I tried then looking at EVC closed event delta , 19.5 deg and add that to the ECT but it just ran richer no improvement. I played with + 1,1.2,.5 in ECT and it ran rich or nothing.
but this brought the Boundary close to TDC or in the overlap start I think.
Lowering the ECT some actually helped.

I am confused a little if my logic works or I just got lucky on the 5.58
I am leaving the ECT alone for now.
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Old 01-11-2018, 11:36 PM
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That cam is relatively small, changing the EOIT isn't going to do much if anything for you. That cam should not have any idle issues what so ever with stock EOIT settings if the rest of the tune is done correctly.
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Old 01-12-2018, 08:15 AM
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I understand and I am taking in next week for a pro tune but as I was getting my idle dialed in I want to play. With updated Inj # the car is running well and responding to fuel and idles strong but still sounds to rough and choppy. Same tune just change teh EOIT and it sounds like a different car and the gas immediately stopped filling my garage. I had to run a fan to keep the fumes out before.

My question is not if it works for me but trying to understand the EOIT# in relation to the IVO? The EOIT is listed as ref pulses after (or before?) TDC.

So 6.55*15 = 98 minus 5.55x15 ~ 15 degrees ATDC for SOI start? or is BTDC?

I am trying to understand does the stock EOIT end point of 6.55 occure before or after the IVO?
If before then what I did makes total sense. and avoided half my fuel being in the middle of the 4 deg overlap.
If after then it helped some but injecting closer IVO allowing more time for fuel
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Old 01-12-2018, 11:53 AM
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I keep Boundary the same most of the time and just move the Normal EOIT periods... keeping the stock progression from cold to warm engine and just adding the IVC change after 154 degrees. I'd probably do 6.15 on that motor.

When you change the EOIT like that, you have to go back into your VE table and lean it out in the idle regions. Even my 227/244 115 idles around 33 or so in the 800 column. Which is much much lower than it should be. But that's what modifying the EOIT is doing - it's allowing you to spray and waste less fuel. But you have to play with the 1200 column a lot as it's a transition column... especially in the lower kPa regions (where it will want to be richer with less timing) with those EOIT settings.

Best way to do it is to do Real Time Tuning (if you have a Custom OS) and you can just take the 800 column and lean it out 2% at a time (or do it with the VCM bi-directional controls) until you get it to stable idle without adaptive spark on. You'll see how much EOIT allows you to lower the VE in those regions.
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Old 01-12-2018, 12:54 PM
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Yes that is what I did basically after adjusting EOIT.
My question still is how does this relate to EOIT and valve events and where are the SOIT/EOIT in relation to the overlap.

the IVC is about 19 deg longer then stock. The normal ECT table is 5.5 144F+
So adding 1.2 to the 5.5 number. I guess is same as shifting boundary 1 back?
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Old 01-12-2018, 04:42 PM
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I don't know everything about the Normal/Boundary relationship. I don't think anybody knows for sure on the Gen III. Just a lot of conjecture based on what people have witnessed and what Bluecat found in the GM PCM driver for how it looks at the 720 degree cycle with regards to reference points in those tables.

I've just found that moving normal later aligns well with a longer IVC. It does allow for a lean out and cleans up some of the gas smell.
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Old 01-13-2018, 06:35 PM
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Stock boundary should be 6.50.
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Old 01-13-2018, 06:46 PM
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According to my spreadsheet, EOI of 6.5 would be 386 degrees after TDC compression, while IVO would be 328.5 degrees after TDC compression. Accuracy not guaranteed, and I'd hate to have to figure out (again) how this was derived.

EDIT: used wrong cam numbers before, fixed now

Last edited by patSS/00; 01-13-2018 at 06:54 PM. Reason: wrong numbers
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Old 01-13-2018, 07:14 PM
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So far along in the thread and I STILL haven't figured out what EOIT is.... someone tell me please?
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Old 01-13-2018, 07:30 PM
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believe it's end of injector timing, big cams can generate an issue relative to fuel trims/limited gen 3 pcm memory parameters when tuning
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Old 01-13-2018, 07:37 PM
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Makes sense! Thank you!
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Old 01-15-2018, 10:00 AM
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Pat I am still confused. EOIT is 15deg/pulse. so 15x6.55 = 98deg AFTER TDC which is the text in HP Tuners.

so is that 98deg + 360 or + 0 either way it is 98 deg ATDC

then my IVO is 9.5 AFTDC stock so EOIT is ~ 89deg after IVO opens.
the normal is 5.55 ~ 83deg so 89-83 5 degres.

So SOIT is at best 5 degrees AFTER the IVO opens?
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Old 01-15-2018, 01:40 PM
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Originally Posted by Jim Cuff View Post
Pat I am still confused. EOIT is 15deg/pulse. so 15x6.55 = 98deg AFTER TDC which is the text in HP Tuners.

so is that 98deg + 360 or + 0 either way it is 98 deg ATDC

then my IVO is 9.5 AFTDC stock so EOIT is ~ 89deg after IVO opens.
the normal is 5.55 ~ 83deg so 89-83 5 degres.

So SOIT is at best 5 degrees AFTER the IVO opens?
First off, the calculation I used came from a long post on the hptuners forum, by some guy who experimented with EOIT numbers and came up with a formula, and there's a long thread debating it, and I don't have a link sorry but I'm sure you can find it. So for EOI I've got: -784+((boundary+normal)*90). For normal=5.55 that's 300.5 after TDC compression which is 59.5 BTDC intake. The IVO is just the cam number at .006 "advertised", which for example is 29.5 BTDC for the cam I'm looking at at the moment. So as long as EOI is before IVO you're good, since you don't want gas sprayed directly into the cylinder. If I try normal=6.5, I get EOI is 386 after TDC compression, which is 26 *ATDC* intake, which is after IVO for that cam, so not good. As for the finer points of changing "normal" below 6.5, check that thread.
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Old 02-08-2018, 11:50 PM
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Originally Posted by patSS/00 View Post
First off, the calculation I used came from a long post on the hptuners forum, by some guy who experimented with EOIT numbers and came up with a formula, and there's a long thread debating it, and I don't have a link sorry but I'm sure you can find it. So for EOI I've got: -784+((boundary+normal)*90). For normal=5.55 that's 300.5 after TDC compression which is 59.5 BTDC intake. The IVO is just the cam number at .006 "advertised", which for example is 29.5 BTDC for the cam I'm looking at at the moment. So as long as EOI is before IVO you're good, since you don't want gas sprayed directly into the cylinder. If I try normal=6.5, I get EOI is 386 after TDC compression, which is 26 *ATDC* intake, which is after IVO for that cam, so not good. As for the finer points of changing "normal" below 6.5, check that thread.
This is correct. It was from bluecats write up on EOIT. I've used this with success. Leave the boundary alone, and solve for x where x is your exhaust valve closing (if that is your target). This is all up for a lengthy debate on what time actually works as far as when to spray IVO? EVC? Hard to say really... GM targets the back of a closed intake valve (300.5*)

Something like this work for figuring out where to set the normal table:

EVC (event) + 784 / 90 - 6.5 = normal

It works fine for me. Mine is at 370* currently.
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Old 07-06-2018, 03:33 AM
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Originally Posted by patSS/00 View Post
First off, the calculation I used came from a long post on the hptuners forum, by some guy who experimented with EOIT numbers and came up with a formula, and there's a long thread debating it, and I don't have a link sorry but I'm sure you can find it. So for EOI I've got: -784+((boundary+normal)*90). For normal=5.55 that's 300.5 after TDC compression which is 59.5 BTDC intake. The IVO is just the cam number at .006 "advertised", which for example is 29.5 BTDC for the cam I'm looking at at the moment. So as long as EOI is before IVO you're good, since you don't want gas sprayed directly into the cylinder. If I try normal=6.5, I get EOI is 386 after TDC compression, which is 26 *ATDC* intake, which is after IVO for that cam, so not good. As for the finer points of changing "normal" below 6.5, check that thread.
Could you please explain EOI before IVO? With my cam the intake valve opens 51 BTDC and exhaust closes 53 ATDC so by using this formula will I be spraying into an already open intake valve?
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Old 07-12-2018, 02:37 PM
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I believe the basic idea is that factory calibrations, which are built around cams that have virtually no overlap, try to spray on the back of a hot intake valve, which improves fuel atomization.
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Old 07-18-2018, 07:38 PM
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Originally Posted by toolbag92 View Post
Could you please explain EOI before IVO? With my cam the intake valve opens 51 BTDC and exhaust closes 53 ATDC so by using this formula will I be spraying into an already open intake valve?
I wouldn’t suggest just going off your valve events as a sole means of setting this and forgetting it. A lot of factors are at play dynamically inside the chamber. Remember that this is the end of injection. This of course takes time to complete, and is measured in milliseconds. Also, on a gen III there is no compensation for RPM. So what works at idle may not be desirable at WOT. Best bet is to move your normal table up a little at a time until you get the results you want. As Jake mentioned earlier, most people usually do this to clean up the raw fuel smell you get from lots of overlap. You can go too far, so be careful as to how much you adjust this value. I’ve read that some guys are in the 390* range on their engines, but that was way too much for mine. Mine seems to like 370*, and runs well there with a lot less fuel in the air. Every engine is different though, so this is purely up to how much time you want to spend on it.

As as far as this question goes, it plays into transient fueling, and atomization on a hot valve. This is stated in the previous response. There are many factors here on a modified engine though. Airflow, valve events, heat soak, injector size and so on add to the problem. You can however use your IVO as a start point and go from there. If you’re doing this to correct a lean or rich spike on your VE, look into transient fuel. Remember, any adjustments on EOIT will affect the transient fuel calculations, obviously.
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Old 01-07-2019, 10:38 AM
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Just curious on what table in EFI live are we adjusting b3701?
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Old 01-07-2019, 12:36 PM
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B3702 Injector Timing. FYI - the EFILive table is in mSec's and not reference periods as in HPT's. FWIW - I "think" they are the exact same tables in the actual OS, just that EFILive chose to scale them as ms's and HPT's is in reference periods. If you are wanting to play with it, just scale what has been discussed in this thread and adjust accordingly before making the changes in EFI Live.
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