EOI Timing Need Help

[aceperformance]

I am trying to understand EOI Timing in HP Tuners with no luck. I have read for hours and still it makes no sense to me. Is there some formula for this? I see 3 tables (Boundary, RPM, ECT) which do you change? do you increase the number or decrease it? How much?
My cam is 224/236 581/601 on a 114+4. I have the raw fuel smell at idle and my afr's are rock steady at 14.5 with e10.

[Phil@PnP Tech]

EOI = Boundary - (ECT+RPM)

EOI (End Of Injection). This value is 0-720º which represent the 4 stroke combustion cycle. 0 being TDC at the beginning of the intake stroke. 720º being TDC at the end of the exhaust stroke. This value is when the ECM will END the fuel shot for that cycle.

ECT. This is an adder. As engine temp increases, this value falls off. This allows the fuel more time to phase change into a vapor in a colder engine.

RPM. This is an adder. As the RPM increases, this value increases. This allows the fuel more time to phase change into a vapor due to the increase of airflow.

Basically, you want to inject the fuel earlier in a cold engine and inject it earlier as RPM increases



I have the raw fuel smell at idle and my afr's are rock steady at 14.5 with e10.
Is this 14.5 based on E0 with a stoich of 14.67? This would be slightly rich
Or, Is it 14.5 based on E10 with a stoich of 14.11? This would be lean.
Learning to work in lambda is much easier.

It is very common to get a lean reading but still have a rich smell. The oxygen sensor reads oxygen content of the exhaust. If you are getting fuel/air charge short circuiting the combustion due to cam overlap, you will get the fuel smell along with lean reading on a WB.

The factory L76 cam has -29º of overlap (@ 0.050"). The exhaust and intake valves are never open at the same time. This allows the OE calibrations to really increase injection timing without short circuiting the fuel/air charge.


My cam is 224/236 581/601 on a 114+4. This cam has 2 degrees of overlap (@ 0.050"). So now you have some overlap and your intake valve is opening 19º sooner than stock.

The first thing I like to do is adjust the boundary based on the intake valve timing. In your scenario, I would subtract 19 degrees from the boundary table.

The next part is to figure out when the start of the injection happens based on your ECT and RPM. You will need to know injector pulse width (IPW) and rpm. To convert pulse width into degrees of engine rotation = 0.006*IPW*RPM. So at a 725rpm idle with a 3.4msec IPW, the injector will be firing about 15º of engine rotation.

So now you know the end of injection {boundary - (ECT +RPM)} and how long it takes to fire the injector, you can now figure out when the injection starts.

If EOI = 425º and IPW = 15º, the injection will start at 410º

You can build a spreadsheet to start and see when your start of injection happens before the exhaust valve fully closes. To remedy this, you will need to reduce the ECT adder. With your cam, you will need to reduce the ECT adder to about 115º from -40 up to 133 degrees F and stock the rest of the way up.

[STL_G8GT]

Very cool, tweaker, thanks for the help.

[Phil@PnP Tech]

Forgot to mention... If you have removed the catalytic converters, zero out all of the Cat Lightoff tables in Engine>Advance>Cat Lightoff. These tables remove timing during warmup to warm the cats up faster. With reduced timing, not all of the a fuel/air mixture is burned in the cylinder but rather in the exhaust to generate heat downstream. This can skew WB readings as well as produce fuel smell. Once you remove the Cat Lightoff timing modifiers and fix the EOI, recheck your MAF tune in the idle cells. Tweak if necessary and your fuel smell should be greatly reduced.

[aceperformance]

This is what I was looking for. Thanks a lot. Everything else I have read has made me more confused than anything. I have got it now.


Sent from my iPhone using Tapatalk

[blkscooby]

I know how you feel. I spent weeks playing with EOIT with my first cam.

[aceperformance]

when I started playing with eoi timing I started taking the boundary table down. I think it was around 525 to begin with. I first went to 500 and it was much richer in the idle area so I went down until it quit getting richer. It ended up being 475. So you are saying to go back up to 506 and pull my ect table up to 115 from -40 to 133 from upwards of 200? would that not be going the opposite direction? Still trying to understand this stuff. Am I missing something? Should I do nothing to the rpm table.
What I have done now is return everything to stock pull 19 from the whole boundary table and and changed my -40 to 133 ect table to 115 is that correct.

[Phil@PnP Tech]

With your cam, the exhaust valve is closing at 360º. Now that is at 0.050" so depending on your lobe profile, it's probably not fully closing until 385-390º. So you want to shoot for no injector pulse starting before 390º in the idle rpm's.

Now moving the boundary up 19º (decreasing from 525 to 506) is not moving in the right direction but you want maintain the same EOI to Intake valve timing.

Next is to figure out the pulse width of your injectors idle at to know how long they are firing in degrees of rotation. My stock 42# idle around 3.4msec at 675 rpm. Using the equation from above 0.006*3.4msec*675rpm = 13.77º

If you want to maintain at least an injection start of 390, you want to find out what the max ECT adder you can handle.

Injection Start + Pulse Width = Boundary - (ECT + RPM)... 390º + 13.77º = 506º - (ECT + 0º) ---> ECT = 102.23º. Your ECT adder can not exceed ~102º at idle. (This is all assuming your RPM adder is stock at 0º at idle). Look at your ECT table and you will probably have to change to complete table to 102º. Leave the RPM table stock.

Now that you have the EOI timing set, you need to make sure the rest of your tune is good.

First off if you have the cats removed, make all of the tables in Engine>Spark>Advance>Cat Lightoff are set to 0º. These tables reduce timing on warm-up to burn some of the fuel in the exhaust to aid in the heating up of the cats so they can do their job sooner. The delayed timing will show a few points rich on a WB and could produce some fuel smell.

Next, make sure your are idling around 13-18º of advance and your adaptive idles is only swinging a few degrees. MAF only tunes have a hard time keeping a steady air calc when the idle is isolating RPM.

Next tune your MAF again in the idle frequencies.

During warm up, the car will be in Open Loop until the O2's are ready to start providing trim. Depending on the start temp, warmup will be rich and decay until stoich. You will get some fuel smell here but it can be minimized with a good tune. Once the engine warms up, your STFT should be +/-0.5% with a good tune.

Be careful with the AFR gauge. If stoich is set to E0 at 14.67 AFR, even with E10 stoich will be 14.67 on the gauge.

EOI is only part of the solution for a good idle. As you see, there are a lot of other factors. I've seen O2's come on too early and trim bad to bad MAF signals. Good Luck.

[aceperformance]

Thanks for all the help

[blkscooby]

I have a very similar Comp Cam in my new G8 and I don't have raw fuel smell at all. It does have high flow cats though. I haven't adjusted the EOIT at all.

[aceperformance]

I don't have cats The cats will help a lot. I finally got it straightened out last week then pulled the cam. Go figure. It's a good sounding cam though. It will be missed.

[johnbell2]

This is an interesting thread...

Let's say for sake of discussion one goes from the stock 200/208 116.5+0 cam:

IVO IVC EVO EVC Overlap
-16.5 36.5 40.5 -12.5 -29

... to a 218/230 115+3 cam:

IVO IVC EVO EVC Overlap
-3 41 53 -3 -6

If I understand this right, would you go off the difference in the EVC numbers and add 9.5 degrees across the board to the ECT table? If it's the IVO numbers, add 13.5?

[johnbell2]

I think I can answer my own question based on this...

"The first thing I like to do is adjust the boundary based on the intake valve timing. In your scenario, I would subtract 19 degrees from the boundary table."

So, in my case, it would be subtracting 13.5deg from the boundary table as a starting point (change in IVO), which reflects an IVO that's 13.5deg sooner than stock.

I've seen DSteck and others state that the boundary table shouldn't be mucked with, however. So, going by IVO numbers as suggested and the formula:

EOIT = Boundary - (ECT+RPM)

... it appears you would start with adding the IVO difference across the board to either the Normal ECT or Normal RPM tables. Of the two, I'd pick Normal ECT since I'm not entirely sure negative numbers would be supported in the Normal RPM table (assuming E38 tables under HP Tuners).

After that, it's a matter of observation / smell / logging and tweaking until you're happy, I assume...

[Phil@PnP Tech]

The change in IVO is only used to calculate the new boundary numbers. Once you have the new boundary numbers established based on your new cam, its time to adjust the ECT adder.

Changing the boundary is probably not going to net a real noticeable difference in your tune. I just do it solely based on maintaining injector to IVO timing.
Modifying the ECT table is where you are going to notice a difference. Here is an example...

EOI = Boundary - ( ECT + RPM)
@ 750 RPM with ECT at 25ºF with 3.5msec IPW
Boundary = 500º
ECT = 245º
RPM = 0º
EOI = 500 - (245 + 0) = 255
IPW(in degress) = .006 * 3.4msec * 750rpm ~ 15º

So now you know when the injection will end and how long it takes to inject the fuel, you can come up with an Injection start time. 255º - 15.3º = 240º

So now you know there is fuel in the intake runner starting at 240º. Now look at your overlap. In my cam, the intake valve opens at 360º but the exhaust valves doesn't close until 362º. There is 2º of rotation (@0.050") where the fuel that was injected back at 240º can short circuit past the combustion chamber and right out into the exhaust. (the fuel smell). So what do you need to do to fix this?? Get the injection start time after 362º where we know fuel is only being injected when the exhaust valve is closed.
Now you need to back calculate... it's pretty simple start of injection we calculated was 240º and we need to get it to 362º. So by reducing the ECT Adder value 122º (362-240). We will calculated a start of injection past our exhaust valve closing.

Now there are a bunch of values that change and you need to keep track of how the EOI changes through ECT and RPM ranges. Focus on changing the ECT value for best results.

[realcanuk]

I have used DSteck's EOI spreadsheet to do the calc's with great success. You might want to try that.

[johnbell2]

Thanks all... I've looked at DSteck's sheet and I must be dumb as a brick, because I simply can't figure out what it means lol... obviously much more to learn in this area.

[STL_G8GT]

Thanks all... I've looked at DSteck's sheet and I must be dumb as a brick, because I simply can't figure out what it means lol... obviously much more to learn in this area.


Try pming him, or dsxtuning on facebook... He might not reply quick, but he'll usually get around to it.

[johnbell2]

tweaker47, how are you getting your injector pulse times? In other words, this number:

IPW(in degress) = .006 * 3.4msec * 750rpm ~ 15º

[Phil@PnP Tech]

You can log IPW in the scanner. I used 3.4msec as an example as that's where my stock injectors idle at. Larger injectors will have a shorter PW at idle.

[johnbell2]

ah, right, of course... thanks, I have logs for that and I see 3.4 ms at 750 idle warm as well.

[johnbell2]

OK, here is what I get with DSteck's calculator (attached in zip file) for the following:

- 750rpm and 3.4ms injector pulse time (15.3deg pulse duration)
- EVC @0.050 = -3 (vs. -12.5 stock) = difference of 9.5 (using @0.050 number of -3 in DSteck's sheet for the Exh Close entry)
- IVO @0.050 = -3 (vs. -16.5 stock) = difference of 13.5 (to be subtracted from the Boundary table values, using (520 - 13.5 - 0) here)
- no changes to ECT or RPM tables (screen cap from HPT attached in zip file)

I've also included the Cam Math sheet for my current cam vs. stock to demonstrate the differences (my cam's IVO event is at 363deg in the 720 cycle). Anything I'm missing here? Any help appreciated!

[Phil@PnP Tech]

You dont have any overlap so, yes I would leave the ECT tables alone. From what I can tell, everything looks good to me.

[johnbell2]

thanks much, tweaker47... I'd figured all I should be attempting was a subtraction of the IVO difference from boundary, appreciate you checking my work!

[realcanuk]

OK, here is what I get with DSteck's calculator (attached in zip file) for the following:

- 750rpm and 3.4ms injector pulse time (15.3deg pulse duration)
- EVC @0.050 = -3 (vs. -12.5 stock) = difference of 9.5 (using @0.050 number of -3 in DSteck's sheet for the Exh Close entry)
- IVO @0.050 = -3 (vs. -16.5 stock) = difference of 13.5 (to be subtracted from the Boundary table values, using (520 - 13.5 - 0) here)
- no changes to ECT or RPM tables (screen cap from HPT attached in zip file)

I've also included the Cam Math sheet for my current cam vs. stock to demonstrate the differences (my cam's IVO event is at 363deg in the 720 cycle). Anything I'm missing here? Any help appreciated!

If my memory is correct Dave suggests using the events at .006 with the calculator.

[johnbell2]

he also says don't muck with the boundary table, but... here we are

[Phil@PnP Tech]

he also says don't muck with the boundary table, but... here we are
Here is a quote from Greg Banish that he posted on HPT's forum awhile back:
"In the OEM world, we almost always INJECT AGAINST A CLOSED VALVE to improve evaporation and reduce bore wash. The warm valve does a darn good job of evaporating fuel, given a little bit of time. If you actually look at a log of injection time vs crank angle and valve timing, you would see that at idle and part load, the injection is completed some amount of time prior to inlet valve opening. This time for evaporation gives better overal mixing when port velocity would be otherwise low, which in turn leads to better emissions and torque output."

This is why I change boundary angle. GM has put a lot of time calibrating the end of injection vs. valve timing event. When you change a cam, it's not quite apples to apples in all aspects but I like to at least match the injection to valve timing events (not just at idle either). Decreasing the boundary angle is really moving in the wrong direction when your overall goal is increase the start of injection to miss the open exhaust valve. You address that in the ECT adder table.


If my memory is correct Dave suggests using the events at .006 with the calculator.
I would say .006" events is a more conservative approach. Depending on a lobe's ramp speed, the difference between 0.050" and 0.006" events could be a swing of 30 degrees. Now I don't have any hard data that says X% of short circuit flow is diminished by the 0.050" event, but just my general thought of how low the flow is at 0.050", I would say it's not going to net a huge difference. If you aren't happy with the 0.050" values and you have 0.006" data, try it and see if you net better results.

[johnbell2]

on a Comp LXL lobe (my exhaust), ramp from 0.006 to 0.050 is 52deg...

basically it's a difference between me putting -3 or 23 as the value for EVC in the sheet... a decent swing in DSteck's results if you plug that in

[Phil@PnP Tech]

DSteck's math and my math are the same. I personally think his spreadsheet can be misleading if you don't really understand the values it is generating. One can get caught up in trying to make the whole table all green when really, the values plugged in just for that specific RPM, IPW, and Boundary. Try upping the RPM and IPW and see how it changes.

The whole point of adjusting EOI is to simply delay the fuel charge until the exhaust valve is closed so it can't short circuit combustion with a focus on the idle RPM's. Ignore boundary and ECT and compare as if their values gave you start of injection based on 0.050" and 0.006" exhaust valve events. One is starting at -3 and the other is 23. Based off Banish's comment I mentioned, I would much rather have my injection start at -3º than 23º

[realcanuk]

DSteck's math and my math are the same. I personally think his spreadsheet can be misleading if you don't really understand the values it is generating. One can get caught up in trying to make the whole table all green when really, the values plugged in just for that specific RPM, IPW, and Boundary. Try upping the RPM and IPW and see how it changes.

The whole point of adjusting EOI is to simply delay the fuel charge until the exhaust valve is closed so it can't short circuit combustion with a focus on the idle RPM's. Ignore boundary and ECT and compare as if their values gave you start of injection based on 0.050" and 0.006" exhaust valve events. One is starting at -3 and the other is 23. Based off Banish's comment I mentioned, I would much rather have my injection start at -3º than 23º

All valid points I am sure. I only made adjustments in the idle area (Dave also suggests that is what he meant the spreadsheet for). I am not the type to spend too much time experimenting. My car runs great with the values generated, so I didn't really go further. There may be room for improvement. I really don't understand EQIT very well which is why I the spreadsheet works for me.

Any thoughts on numbers ... cam is 226/246 .610/.637 119+3