Injector timing

Tuning concepts, methods, tips etc.

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Dennis_Zx7r
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Re: Injector timing

Post by Dennis_Zx7r »

By decreasing the number you're actually delaying the injection, resulting in less time until the intake valve closes again, if you're looking at it cycle by cycle.
Assuming you use start of pulse, the MS will automatically spray into the open valve if the PW gets large enough it is the injection duration and you only set the angle when to start it.
Note that injection timing cannot extend DC% beyond 100% at any time and that the timing gets less important the higher DC% gets.
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billr
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Re: Injector timing

Post by billr »

Note that injection timing has no effect on the injection pulse duration; nothing you do with the timing can increase the "window" for injection, cannot squeeze more flow out of an injector.
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Re: Injector timing

Post by Yves »

I've found advantages and disadvantages with injection timing in my setup
- at low(er) rpm it is advantageous to have the injection earlier so that the fuel gets more time to atomize due to intake heat.
- at higher rpm this effect plays less of a role due to more turbulence and the added disadvantage that the fuel tends to pool on the intake floor due to the amount of fuel injected at those rpms and during a subsequent decell getting sucked through and stays in the exhaust were it burns the next time the cylinder fires ok.

My setup however is a bit atypical in terms of injection angle.
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Re: Injector timing

Post by Djovani_jr »

How does the ms3pro consider intake?

360-540 or 360-180?
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dll67
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Re: Injector timing

Post by dll67 »

Your gonna love this ... The ms3 will take an input of anywhere from -360 to 720 ... I'll admit, understanding the 720 cycle and knowing exactly what to put in for a number .. its a chore with little reward... Some setups will benefit more than others.
. The ms3pro should be the same, but who knows.
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Re: Injector timing

Post by billr »

360-180

On timing, all numbers are BTDC and "0" is the TDC between compression and combustion strokes
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Re: Injector timing

Post by Djovani_jr »

billr wrote:360-180

On timing, all numbers are BTDC and "0" is the TDC between compression and combustion strokes
Thanks. it seems to be true!
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martin2day
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Re: Injector timing

Post by martin2day »

Hello,

i want to tuning my injector timing too.
As written in this posts i also think if i want to inject earlier i have to increase the numerbers in the Injector timing table.
As it is count in BTDC of the ignition event.

But now i see the video of Andy Whittle:
https://www.youtube.com/watch?v=DLcsaLWKZMk

He test the injector timing and he is count on the other direction?!
If i want to inject in the open intake Valve... if i do it like the posts here i have to set it up lower... for example 270°.

If i look at Andys chart...
injection.png
injection.png (614.27 KiB) Viewed 1521 times
The Inake Valve Event is at an higer Value than 360.... 400 and more....

So what is right... ? :-)

Please can someone help?

Thank you so much
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Re: Injector timing

Post by whittlebeast »

Yep, I blew that part. The result of the test by using the methods in the test would result the same either way, so I never changed it. My bad.
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Re: Injector timing

Post by KenAdkison »

My wife and I have been checking into hotels smelling of fuel from our hair & clothes and eyes burning.

Spraying into the open valve with 420 across the board lowered our auto tuned VE by about a third and although it sounds and runs about the same we no longer stink. This indicates we were blowing significant fuel through the overlap. The WBO2 only measures oxygen and seems to have a hard time recognizing the unburnt fuel.

We have a 1800cc MGB, with a relatively mild cam and motor with parts matched for touring and mid range. I hope to find a way to pay for some dyno time to test things as I have no idea what the best numbers are for my combination.
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Re: Injector timing

Post by arnold »

Do you have siamese ports?
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Re: Injector timing

Post by hotrodf1 »

KenAdkison wrote:My wife and I have been checking into hotels smelling of fuel from our hair & clothes and eyes burning.

Spraying into the open valve with 420 across the board lowered our auto tuned VE by about a third and although it sounds and runs about the same we no longer stink. This indicates we were blowing significant fuel through the overlap. The WBO2 only measures oxygen and seems to have a hard time recognizing the unburnt fuel.

We have a 1800cc MGB, with a relatively mild cam and motor with parts matched for touring and mid range. I hope to find a way to pay for some dyno time to test things as I have no idea what the best numbers are for my combination.
I've been fiddling with injector timing too, but I'm a bit confused by your post.

Are you saying you have 420 degrees in the injector timing table across the board? If so, I thought that was an earlier event then 360. So shouldn't that mean that you are actually spraying fuel onto the closed intake valve (which some say will help atomized the fuel before it's pulled into the cylinder). I believe this is the thought of the OEMs (with probably not much / no cam overlap though).

My results are similar : my cam opens the intake valve at 30 BTDC, so I started with 360 + 30 = 390 and then added 5 or so every so often. The car seems to run smoother, idle is more stable, etc. Haven't noticed a whole lot in the VE table as far as changes needed though. I haven't tried too much higher yet to see if there is a diminishing effect at some point, or where that might be.

But your post has me curious whether i advanced my injector timing or retarded it :?:
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Dookie454
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Re: Injector timing

Post by Dookie454 »

I've been playing with Injection Timing for a while, there are Injection Timing spreadsheets avail to help you ball park what you need to do, but these are setup for GM OEM ECU's, you can still use them to figure out what is best. They were made to help with non-real-time tuning ECU's where you have to flash, scan, analyze, and repeat which takes forever, and other problems arise from this which is due to the time delay between changes, flashing, and logging.

In the end, easiest way to do it is get your car running great with stock settings, setup an AFR correction histogram, and see where you are, then simply add 150ish to the timing value, and watch your Correction change as you change the Injection Timing value. What you are looking for is richest fueling (Correction removing as much as possible), without changing the VE table. What this means is your burning more of the fuel that you injected, rather than spitting it out of the exhaust.

For example, on my LS3 Camaro, I drove for 40mins, came back home and idled in the driveway. I had 360 (or whatever stock was) I was at 14.7afr at idle, with about 102% Correction (adding 2% fuel). Then I changed the value to 500, and instantly my correction started going negative, settling around 98%, still at 14.7AFR.

What this means, is more of the injected fuel was burnt. Usually a combo of more evaporating on the hot intake valve, and less being pushed out of the exhaust in raw liquid form. Keep adjusting those values to see what works best for your combo. If you have a larger ovelap cam, then the low rpm random missfilre may tend to skew your AFR readings, but still you should see an overall change in AFR correction.

Yes, you want as much time on the hot intake valve as possible, to evap the fuel since evaporated fuel burns better than liquid fuel droplets.

You can try to calculate the numbers, but with the Megasquirt real time tuning, you really don't have too. Adjust the Injection Timing values and watch the AFR change. Then, you can also look at the Histogram you setup. Mine went from majority 102% correction in most areas, to 98% correction in most areas, which means it's using less fuel to create the same AFR, sending less unburnt fuel out of the exhaust. You will notice a change in exhaust smell also, less "raw fuel" smell. Larger overlap cams will benefit the most from this type of tuning.

UPDATE: Another plus, is I've had my LS3 Whippled, 10psi for years now, and i know that no knock (according to oem ecu) is normal. At most, I might get 0.3deg knock retard on a WOT run. Well, since installing the MS3 on fuel only, running same AFR, for about 3 months now, I've been noticing a pretty regular 2-3 deg knock retard on a WOT run. Since changing the Injection timing from 300's, to 500's, It seems to have removed the knock retard I was getting on a WOT run! This is interesting sfuff for sure.

I dont know if the MS3 is timed the same as the stock ECU, but the stock ECU was around 520 degrees for timing as well.

https://forum.hptuners.com/showthread.p ... -Requested
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Re: Injector timing "Balance"?

Post by hotrodf1 »

Thanks for the info and experience there.

The comment about large overlap cams benefitting the most from early injector timing is interesting.

I did some reading from another guy that was apparently a drag racer and no stranger to large amounts of cam overlap, and he actually claimed opposite theories. His theory is that when the intake valve opens, you will have some amount of charge that goes directly out the exhaust valve (since exhaust is flowing out and the overlap essentially opens up a pass through I guess), so by actually ending the squirt later in the cycle, you had less chance that the first part of the intake charge would be wasting fuel out the exhaust. He also said that you'd have less of a fuel smell, since you'd reduce the amount of unburnt fuel sent direct out the exhaust.

So I tried it both ways, though I haven't advanced as far as 500 degrees (that seems like a lot, but I'll try that soon.) My cam is 224/224 @ .050 with 114LSA, so not real big, but still a lot more overlap than a stock"ish" cam. When I had the timing advanced to 400 or so, it seemed like cold starts were terrible. I actually thought I had a problem somewhere. When I changed the timing back to 360 the problem seemed to go away. I guess the theory would be the cold intake valve didn't do very well at evaporating the fuel until the engine was warmed up. The other thing I noticed was that with timing advanced my accell enrichment was WAY off (too lean). So then I went the other way, and am currently about 348 degrees, and it seems much happier there. Cold starts not a problem, and the accell enrich is right back fine again. I was surprised to say the least!! I haven't taken it further just yet to see where the diminishing return begins.

But I need to do some more testing for sure to re-verify what I "thought" I saw.

So maybe there are two opposing "forces" here? More advanced timing = better fuel evaporation on hot intake valve, but more fuel out the exhaust. Contrast with later timing = less [nicely atomized] fuel out the exhaust, but less evap on the intake valve. Which then brings me back to some kind of balance, probably 360 degrees, right where I started!?!? :lol:

More testing and reading required . . . :RTFM:
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Re: Injector timing "Balance"?

Post by Dookie454 »

hotrodf1 wrote:Thanks for the info and experience there.

The comment about large overlap cams benefitting the most from early injector timing is interesting.

I did some reading from another guy that was apparently a drag racer and no stranger to large amounts of cam overlap, and he actually claimed opposite theories. His theory is that when the intake valve opens, you will have some amount of charge that goes directly out the exhaust valve (since exhaust is flowing out and the overlap essentially opens up a pass through I guess), so by actually ending the squirt later in the cycle, you had less chance that the first part of the intake charge would be wasting fuel out the exhaust. He also said that you'd have less of a fuel smell, since you'd reduce the amount of unburnt fuel sent direct out the exhaust.

So I tried it both ways, though I haven't advanced as far as 500 degrees (that seems like a lot, but I'll try that soon.) My cam is 224/224 @ .050 with 114LSA, so not real big, but still a lot more overlap than a stock"ish" cam. When I had the timing advanced to 400 or so, it seemed like cold starts were terrible. I actually thought I had a problem somewhere. When I changed the timing back to 360 the problem seemed to go away. I guess the theory would be the cold intake valve didn't do very well at evaporating the fuel until the engine was warmed up. The other thing I noticed was that with timing advanced my accell enrichment was WAY off (too lean). So then I went the other way, and am currently about 348 degrees, and it seems much happier there. Cold starts not a problem, and the accell enrich is right back fine again. I was surprised to say the least!! I haven't taken it further just yet to see where the diminishing return begins.

But I need to do some more testing for sure to re-verify what I "thought" I saw.

So maybe there are two opposing "forces" here? More advanced timing = better fuel evaporation on hot intake valve, but more fuel out the exhaust. Contrast with later timing = less [nicely atomized] fuel out the exhaust, but less evap on the intake valve. Which then brings me back to some kind of balance, probably 360 degrees, right where I started!?!? :lol:

More testing and reading required . . . :RTFM:
Yes.. I think hitting the valve when cold is causing your cold start problems, in that case, you can probably change the crank RPM back to 360? Not sure how my oem ecu handles cranking, I didnt see a table for that. OEM ecus (GM anyway) use a calculated Intake Valve Temp fueling table, this is what sets your cold engine fuel, it's not using Coolant Temp anymore, and this is why (optimized fuel burn by injection timing on a hot engine, but on a cold intake valve, it needs more fuel than the normal injection timing).

The main point is to limit the amount of push out of the exhaust valve on a boosted low overlap combo by ending the squirt before intake valve opens, if possible. Since many of us with these LS3's end up boosted, as in my case. Strategy would be different with non-boost, large overlap, it would be more important to end before intake valve opens. I noticed I didnt say that in my original post! End Squirt before intake valve opens is usually the goal! So that is the same as what you said. Only way to really test if it works would be run down the drag strip a bunch of times, change the injection values, see if your AFR changes. These people who test this on a dyno swear they see 20-50hp gains in most cases as well. I can tell you, with 360, mine feels slower, and I get more knock but knock retards timing, so who knows. I'll keep an eye on the knock, for sure. I havent seen any in the 2 days I've been running this 500ish timing.

I dont know how accurate that timing number is, really. I'm sure it can be accurate, probably depends on your trigger wheel setup. On my setup, 58x crank with the 4x cam, maybe it's pretty accurate? Maybe I should say "phased". Maybe different combo's have different phasing.

When you noticed the cold starting problems, did you have less fuel required to maintain AFR setpoint? I didnt notice a change in transients at all, just about 5% less fuel required to maintain AFR.

This may also play into the reason why you dont want your injectors going past 80%, because then they will be open all of the time, intake valve open, closed, etc. Correct? Any chance at minimizing fuel blowing out through the overlap area is gone.

I think with the calculator, and rule of thumb, is to basically try to stop injection as your intake valve opens, if possible. Depending on injector size, that wont be possible especially on high boost, large fuel load.
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Re: Injector timing

Post by Dookie454 »

To sum it up, my findings:

Goal:
1) Find the richest value, that would mean most fuel is being burnt.
2) Try to end the injection event before the inlet valve opens at lower RPM
3) At higher RPM, that is less important as turbulence helps atomize the fuel, but at the same time:
4) At hgher RPM try not to squirt fuel while the exhaust valve is open during overlap,

So for me, Boosted, stock cam with little to no overlap, I've achieved #1 and #2, and see ~5% less fuel required. I did that by watching AFR Correction at idle, changing the timing value. 500ish was my number at idle.

Since I don't have much overlap, #3 and #4 are less important until I change cams. But still 500isu seems to work for me, as it reduced my AFR Correction the same 4-5%, and it seemed to get rid of my knock, running the same now as it did on the oem ecu.

If I change cams, with overlap. likely I'll have to reduce the upper RPM timing values.
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Re: Injector timing

Post by Dennis_Zx7r »

Dookie454 wrote:In the end, easiest way to do it is get your car running great with stock settings, setup an AFR correction histogram, and see where you are, then simply add 150ish to the timing value, and watch your Correction change as you change the Injection Timing value. What you are looking for is richest fueling (Correction removing as much as possible), without changing the VE table. What this means is your burning more of the fuel that you injected, rather than spitting it out of the exhaust.
A MS setup usually uses Multiply MAP. This means that if you affect the MAP reading with your injection timing changes, you greatly affect the injected fuel although you may have the same VE. For example if your MAP reading changes from 50 to 53, 6% more fuel is injected. Therefore I think you shouldn't look at EgoCorr but rather PW after EgoCorr has stabilized, if your goal is efficiency.
This is assuming you have a constant differential fuel pressure unaffected by MAP changing over the cycle (invalid assumption for very low Duty Cycles or ITBs).
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Re: Injector timing

Post by hotrodf1 »

Dookie454 wrote:To sum it up, my findings:

Goal:
1) Find the richest value, that would mean most fuel is being burnt.
2) Try to end the injection event before the inlet valve opens at lower RPM
3) At higher RPM, that is less important as turbulence helps atomize the fuel, but at the same time:
4) At hgher RPM try not to squirt fuel while the exhaust valve is open during overlap,

So for me, Boosted, stock cam with little to no overlap, I've achieved #1 and #2, and see ~5% less fuel required. I did that by watching AFR Correction at idle, changing the timing value. 500ish was my number at idle.

Since I don't have much overlap, #3 and #4 are less important until I change cams. But still 500isu seems to work for me, as it reduced my AFR Correction the same 4-5%, and it seemed to get rid of my knock, running the same now as it did on the oem ecu.

If I change cams, with overlap. likely I'll have to reduce the upper RPM timing values.
Wait a minute - With a larger cam, I presume the intake valve will open earlier - if your goal is to end the squirt before the intake valve opens, shouldn't that mean you need to increase your value (make it earlier as well)???? Sorry, just trying to sort through the logic as I learn. I'm used to carbs, LOL. No injector timing there.
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Re: Injector timing

Post by BlueCuda »

This has been an interesting read. I have a large overlap cam in a NA combo and while it runs and drives great the fuel smell is bad. I have a tunnel ram and the manifold is all fuel stained like it had a carb on it. What I believe is that at low RPM the fuel is getting blown back into the manifold due to the overlap and that of course makes a mess of distribution. This thing will idle just fine as lean as 17:1 but the fuel smell is still really bad at idle. I am sure during the overlap there is probably some fuel making it into the exhaust as well. Of course as the RPM gets higher and the cam starts to work all is well.

I haven't played with the numbers a ton but I will try a few of the methods from here this weekend and see what I can find out. I have a large enough injector I think at low RPM and low load it can be timed to spray only while the valve is open and after overlap. I can't for the life of me wrap my head around the numbers enough to know when that will need to be. I want to minimize the fuel blown back into the intake due to reversion and minimize the fuel that makes it out the exhaust during overlap. Maybe I am asking for to much :mrgreen:

I attached my cam card if anyone cares to see what is going on there. My Dad has a good relationship with the tech guys at comp I am going to see if he will email them about this and see if they have any input also.
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Re: Injector timing

Post by BlueCuda »

I just looked at a friends project that came with a base tune. Its a Stinger Performance MS3 for a fox body mustang. The base tune was called "347 with huge cam". The injector timing table they have in the base tune starts at 550 and reduces to 400 after 3500 RPM. His car doesn't have as much cam as mine but it certainly smells cleaner at idle. I have been reducing numbers the few times I have messed with it so I am going to try increasing them.

Food for thought.
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