Injector timing - make me feel better on a 2013 CTSV with 2650 / cam

[Random84]

2013 CTSV - the original cam was a 198/216 .480 / .480 122.5LSA. Since I don't have 0.006" values for either the stock or current cam, I was thinking about using the relative delta change in valve events (similar to what Higgs Boson has suggested in a few of the bigger threads on this). Although I've been reading quite a bit, my ECM values don't seem to match very well with the spreadsheet(s) that have been so graciously shared here on the forum.

2013 OEM cam events estimated at:
EVO - 44* BBDC
EVC - 8* BTDC

IVO - 9* ATDC
IVC - 27* ABDC

-17* overlap

Now for the highly modified 2013 with a 400" motor (3.75 stroke, 4.130 bore, 6.25" rods) and a 2650 blower. Cam specs are 234.3 / 252.4, .640 / .648 119LSA

Aftermarket cam events estimated at:
EVO - 69* BBDC
EVC - 3* ATDC

IVO - 2* BTDC
IVC - 52* ABDC

+5* overlap.

So that means my exhaust valve closes ~15* later than the OEM cam, give or take. And my intake vale opens ~13* earlier

I am also running ID1300v2 injectors to account for E85, so my injector PW on 93 pump is relatively short, 0.8 ms at idle. Even at 7k RPM, my IDJ is 50%, so the injector PW duration is around 11ms at 18psi.

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Based on my reading, for low RPM / idle ranges, I could simply change the Injection timing boundary layer by increasing it 20*, to delay EOIT (and thus SOIT) by that amount for a cleaner idle.

My confusion stems from the "Normal EOI Target Adder vs ECT" tables not being constant, of course for cold start - the fuel will presumably take longer to get to a cold cylinder and thus we shorten the EOIT significantly, so the fuel is injected earlier in the cycle?

Current boundary is 520* across the board, but the Normal ECT table ranges from 240* cold to 105* hot, and a 12* Normal RPM adjustment put in there by the previous tuner.

That means, at idle, 520-105-12 = 403* idle SOI at operating temps. That seems right on for a boosted motor?

Cold starts (my biggest issue: fuel smell and seems to stumble), is 520 - 240 - 12 = 268* idle SOI on cold start. Does this pass the "sniff test" for you guys or is it really advanced?

I am just thinking that with the larger injectors, since I primarily run 93 pump, I should advance the EOIT target for cold starts, say closer to 370*, ergo I should reduce the Normal EOIT adder vs ECT in the colder temps significantly?


Suggestions on how to handle E85 vs 93?


Tune and a recent log should be attached.



Stage 2.58 - increased idle minimum airflow_adjusted MAF curve at warm idle.hpt111615 ECM2.58 warm idle and start-stop with clutch in for idle adv.hpl

[Random84]

Another question is: approximately how many degrees of crank rotation should we approximate for fuel to actually reach the cylinder (FRC values) when cold, vs hot?

When hot, I'd guess it's almost instantaneous. But what about cold starts?

[GHuggins]

Slightly off subject, but what tb setup you running? Only reason I ask is because with that blower and cam and rough engine size you should be over 1000 to the tires with about 16 to 18 psi of boost and a 108ish tb

Also with regards to that cam - I hope you made clearance measurements - it's going to get really tight on the exhaust side - SO reliefs, correct pushrods and measurements are an absolute must with those heads and motor.

[Random84]

Slightly off subject, but what tb setup you running? Only reason I ask is because with that blower and cam and rough engine size you should be over 1000 to the tires with about 16 to 18 psi of boost and a 108ish tb

Also with regards to that cam - I hope you made clearance measurements - it's going to get really tight on the exhaust side - SO reliefs, correct pushrods and measurements are an absolute must with those heads and motor.

AllPro heads - the motor was professionally built. I've been daily driving it for around 2-3 years now so I'm coming up on valve spring replacement already. I've just been focusing more and more on trying to get that cold start idle down for appearances sake.

It was 850 at the wheels on 93 pump, before ironically jumping off the dyno... that was a debacle. Always something.

I have stuck with the NW103 primarily because it's a daily (manners), and I really haven't had confidence in the 108/112mm TB offerings that I've seen. I also didn't want to have to deal with "packaging" the larger intakes required in the CTSV, as I have an aftermarket radiator / intercooler and the front of the engine bay is wanting for space.

[GHuggins]

So your still running a stock intake? Yeah the 108 does require some work - you have to put Nick's Tb motor in it to make it handle the airflow and run a special kind of rubber 130 elbow to mate it to a K&N cai... After that it looks amazing and handles fine. Set the tune up right and even drives as good or better than OE setup.

I assume those dyno numbers are with the old cam? Also assuming the 2 to 3 years part was with the old cam? That new cam is going to require measurements be taken... Those numbers are really low for the setup and 93 if your running the boost.

As for your injection timing. You REALLY need to find a way to either run lower fuel pressure at idle to open that pulse width up or spend a lot of time getting it precise by trial and error. That's going to be your biggest trouble maker.

[Random84]

Greg,

I've had this motor and cam running for 2 years as a daily (15k miles plus). It idles at around 820 RPM very well, but you're right - lowering FP for higher resolution would be a good idea. It's a manual, so I haven't had to fight it very much.

Here's what I'm thinking:

Boundary kept at 520 stock - though I debate moving it to 540* for the larger cam
Estimate 25* rotation for fuel propagation into the cylinders at low RPM in cold air.
I want to target the EV closing (or slightly past), or at ~385* crank rotation (EVC 23* ATDC).
Account for any adjustments in the Normal RPM table, if needed.

Ergo, for EOIT my normal vs ECT modifier table should be 110* in cold start temps.


I need to to figure out injector PW in terms of degrees of rotation for higher RPM to "center" the SOIT/EOIT over peak piston velocity?

ETA: 1 to 1.2ms at idle - ~15* rotation
~12-13ms @ 7K RPM is ~155* rotation

[GHuggins]

Don't target PPV for idle or below 2000ish rpms - you'll wind up losing a lot. Your correct in retarding and then increasing open loop tables for colder temps. You'll also want to lower fuel pressure to something around 45/48 without vacuum. Also your going to find once switching to e85 your going to want to advance your boundary up to something around 505ish - possibly even 500, so you might want to go ahead and target something like that now.

[Random84]

My understanding is that ethanol has a faster flame front (ie burns "faster") and requires less timing advance.

But it also requires ~30% more fuel volume.

So why would I want to advance the EOIT and narrow the start of injection window relative to EVC at low RPM, and PPV at high RPM?

Is the assumption that ethanol will not be as atomized, and thus take longer to reach the combustion chamber?

[GHuggins]

You've got one very important factor going into your injection timing and although cam events and the blower are both important and must be thought of while setting up your injection timing, they are not the "biggest player"... Your "biggest player" is actually going to be your injector size choice and coinciding very small pulse widths. For this your going to want to target as much cylinder vacuum without fuel going out the exhaust as possible while still utilizing the boost airflow on the back side to really get the atomization and mixture going, so right around exhaust valve being fully closed is when your going to want to inject it particularly at idle to 1400ish rpms then ramp up towards a 575 boundary by redline to better target and utilize ppv then.....

My own personal findings with alcohol is this - advanced injection timing it burns better and drives more smoothly. Plus it always seems that when you advance the timing a touch - your gas to alcohol trims better match one another with changing stoichiometric values.

Inevitably your going to have to play with things and see what your setup likes, but I "think" you'll find retarded when cold, then close to stock if not advanced when hot will wind up being the winner...

[Random84]

Thanks for your help, Greg - I know you've been doing this a LONG time.

relatie to my cam, the OEM injection settings were so early that I think I was actually injecting fuel into the open exhaust valve on cold starts (with that 240 degree retard they like to throw in there). My first drive to work today showed a massive improvement in smoothness and cold start; it was really remarkable and now I'm pissed I put this off for so long.

I also got something close to my cam specs at 0.006 so I'll play around with them some more. The whole retarded / advanced terminology can get confusing... so I like to draw pictures.

[GHuggins]

I started with degree wheels and hand drawing in my tdc, ppv, ivo, evo, evc, ivc valve and piston events compared to the calculated injection time window - this was illustrated on a very old write up I did on the subject way back when. Like you - I have to see it myself then do the testing to confirm my thoughts

Oh, and I think you meant (with that 240 degree advance they like to throw in there for cold starts to get the fuel atomization going) vs the retard you said AND you are correct - with blowers and bigger cams - the fuel goes right out the exhaust, which is why I stated "will find it better to be retarded when colder and OEish to slightly advanced when hot"

This was created by guys on here to simplify and incorporate all of the missing data from that original degree wheel... The cam in it isn't yours, just a general representation...

[kingtal0n]

which is why I stated "will find it better to be retarded when colder and OEish to slightly advanced when hot"

Dear sir, please help,

I would like some clarification because I sense conflicting terminology,

earlier you said target PPV for hot, which would be retarded
And for colder we should be advanced to well before PPV but when the EVC, so advanced but not OE advanced

I feel like we are mixing up the retarded and advanced terminology,

would you pls take a min to verify that when you say retarded you mean later and not sooner? PPV is retarded, and OE is advanced, etc...?

[GHuggins]

Retarded is later. I think what is being misinterpreted is the fact that the numbers don't flow in the same manor in the tune itself and that is causing the confusion...

ECT and RPM - higher numbers = more advanced - i.e. sprayed sooner or in the case of the ect table a longer time on the intake valve to vaporize at colder temps
Boundary Tables - higher numbers = more retarded - i.e. sprayed later...

If you look in that spreadsheet - it illustrates the basics of how I retard the injection timing as rpms increase - although this illustration is WAY TOO Retarded up into the rpms and WAY TOO advanced in the lower rpms - you can see where it starts to spray too soon during overlap then it has too much spray time too late in the higher rpms - too much fuel staying in it's "raw" form not being atomized - your looking for a mixture "whole other subject on it's own" of raw to atomized for the octane increasing effect...

[kingtal0n]

Ahh the gen4 strikes again. Thank you for clearing that up I never tuned a Gen4 ecu trying to just learn what I can from the sidelines. Didn't realize they pulled a reversal like that.

sorry if the topic of injection timing is beat to death. I also understand the risk of telling people to do something a specific way and they might do it incorrectly and still blame you for the result. In case it isn't obvious everything we discuss (telling other people reading) is all just a theory of optimization and use at your own risk. At the end of the day we are all accountable for our behaviors- actually some genes probably influence and can lead to some strange side effects I guess without it really being our fault for having those options in the environment due to some protein structure. C what I did there

[NotSure]

Retarded is later. I think what is being misinterpreted is the fact that the numbers don't flow in the same manor in the tune itself and that is causing the confusion...

ECT and RPM - higher numbers = more advanced - i.e. sprayed sooner or in the case of the ect table a longer time on the intake valve to vaporize at colder temps
Boundary Tables - higher numbers = more retarded - i.e. sprayed later...

If you look in that spreadsheet - it illustrates the basics of how I retard the injection timing as rpms increase - although this illustration is WAY TOO Retarded up into the rpms and WAY TOO advanced in the lower rpms - you can see where it starts to spray too soon during overlap then it has too much spray time too late in the higher rpms - too much fuel staying in it's "raw" form not being atomized - your looking for a mixture "whole other subject on it's own" of raw to atomized for the octane increasing effect...

I have been playing around with the injection timing spreadsheet on and off lately, though it is difficult to measure any difference on the road. I don't know who put the suggestions in that spreadsheet at the bottom of the "DOCs" tab, but it states:

"Above 4500 rpms, aim for EOIT-FRC 15-20 degrees before IVC" for blower motors, and "EOIT-FRC at least 20-30 degrees before IVC" for NA.

It would seem that with the longer duty cycle at WOT and high rpm, that it would be OK to allow EOIT-FRC to get somewhat close to IVC, since the spraying is already going on way before the intake valve is even open? More spraying is going on with the intake valve open than would be with an advanced (lower boundary number) injection timing, and you still have the compression stroke to mix things up a bit.

The example ZL1 cam in that spreadsheet has the EOIT-FRC not too much after peak intake valve lift, but waay before the "15-20 degrees before IVC" suggestion in the spreadsheet. Just trying to get my head around it all.

[GHuggins]

They just start leaning out when you push it that far and losing power. Too much un-atomized fuel vs atomized... A lot of those recommendations were from my early recommendations on it - since learned better