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Old 01-24-2011, 09:10 AM   #1
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Default MS2/3 Injection timing maps for sequential injection

Hi,

as my comment got somewhat drowned at the enhanced groupbuy thread...

There is a neat thread about the problems of injection timing (only for MS2 /MS3 and sequential injection) at msextra.com:

Thread

One of the statements in the thread got my attention:

Quote:
I started out trying to use negative degree values in the table, the engine ran rough and I noticed surges from time to time.
After adjusting the values by adding 720 so all were positive the issues seem to have disappeared.
As the DIYPNP basemap has a fixed timing of -350 I thought, that we should maybe think about using the timing map...

There is a user map posted that looks like that...
(I was so free to copy the map...)



Now I did want to know, if anyone uses the map for injection timing and if so - how does the map look?

I'd like to see your input on this - maybe Ben or Matt can give some help..., and I think the Brain uses that map on his MS3?

Thanks
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Old 01-24-2011, 09:25 AM   #2
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here's what I use.



I might want to alter it slightly, this is based around the idea that you want to have all your fuel at the valve around 10 before the intake valve opens. So I'm using End-Of-Squirt.

NA intake valve opens 5BTDC, so I have it at 375. which is 10 before that. 360TDC + 5BTDC + 10 = 375.

I inject fuel another 10 sooner every 1000RPM or so, stopping at 5000RPM. I did this from reading through out the web as the accept "norm".

In boost I also inject the fuel even soon every few psi.



I didn't do extensive trial and error, but this map help reduce the over VE% by a few points throughout and seems to work well for me.
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Old 01-24-2011, 11:47 AM   #3
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Why is it that the map of the guy over at msextra.com and your map is just the opposite direction?
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Old 01-24-2011, 11:55 AM   #4
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because he fails?

Here's how I understand it. The general rule of thumb is put the fuel 10* before your valve opens so you can 1. not only cool it off, but 2. the fuel has finished injecting and should be fully available for the intake stroke. So at idle I have my map set to putting the fuel at 10* before the valve opens. There should also be more vacuum at idle so it shouldn't take long for a short pulse width to get to the valve within the time it has from open to closed injector.

However, when you increase the rpms, the time from injector open to close reduces AND the pulse width increases. So I tell it to start injecting earlier. This was the fuel should still be hitting the valve JUST while compensating for the reduce milliseconds we are working within for the fuel to reach the intake valve.

I could be wrong, but this is how I understand it. I mean I realize we are squirting about 2-3" above the intake valve, so you could leave it at 375 throughout and call it a day, but I worry that even when set to end of timing, that you could still be injecting fuel too late on the cycle if you do it the way Vicoor is doing it.

Last edited by Braineack; 01-24-2011 at 12:21 PM.
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Old 01-24-2011, 01:00 PM   #5
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I just posted there. I think I wrapped my head around what he was doing and why.
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Old 01-24-2011, 02:20 PM   #6
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So what fixed value do you suggest? 375?
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Old 01-24-2011, 02:37 PM   #7
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probably around that. i think the NB cam is something like 8-10 DBTC for intake valve.
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Old 01-24-2011, 11:52 PM   #8
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I've just tried 375 fixed. Didn't feel any change at all.
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Old 01-25-2011, 09:27 AM   #9
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You wont really feel anything, the idea is being about to manipulate the timing for rpm/load to get a more ideal timing and thus be able to remove fuel from the VE table and achieve the same AFR.

You should notice when seq. vs. batch that the enrichments are much smoother and idle easily to get stable.
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Old 01-25-2011, 12:20 PM   #10
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This is true. I removed tons of fuel but only beyond 200 kpa. That was pretty interesting. The afr's went from 11.5-12 to 10-10.2
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Old 02-15-2011, 01:14 AM   #11
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I am trying to get my head around this. While it makes perfect sense to fire the injector earlier as RPM and/or load increase, I would expect that the benefits of injector timing (and sequential injection for that matter) decreases as the duty cycle increases. Would it matter when you fired the injector at a 70% duty cycle?
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Old 02-15-2011, 04:46 AM   #12
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Quote:
Originally Posted by John151 View Post
I would expect that the benefits of injector timing (and sequential injection for that matter) decreases as the duty cycle increases. Would it matter when you fired the injector at a 70% duty cycle?
You are correct it does reduce in effect as DC goes up, though it'll still have a minor effect, at 70%DC there is still some 'off' time for the injector.

If you were running up to say 95%DC there would be no difference when you fired the injector.
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Old 02-15-2011, 09:27 AM   #13
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like me! my injectors are more or less locked open in high rpms with 15psi.
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Old 02-15-2011, 09:33 AM   #14
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I am wondering if the biggest benefit would be in the middle of the table, typical of say highway cruise? If so, this would be a worthwhile improvement to me since my car sees 40 highway miles per day in the summer (dd).
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Old 02-15-2011, 09:39 AM   #15
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yes. You should also tune it yourself and see where you benefit.

A good way to do this is start with a base timing table and a good VE table. Then alter the map in a specific area and start autotuning. You'll want to watch to see if you are pulling or adding fuel in that area. If you are pulling fuel, you got the timing to a more efficient zone, if adding, you'll wanna revert back.
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Old 02-15-2011, 11:50 AM   #16
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I would also expect that getting the injector timing dialed in would reduce the amount of AE needed as there would be less fuel lingering around and collecting on thee walls inside of the manifold.
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Old 02-15-2011, 11:55 AM   #17
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That is correct. On both of the cars I've tuned sequential on, the throttle response is a LOT better, and I need much less accel enrichment.

I'd already tuned EAE on my rx7, and I had to turn it off to get the VE retuned because EAE was so far off compared to the batch fire settings. I'm going to get back to tuning that very soon though, as the car did drive better with it tuned properly.

Ken
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Old 02-15-2011, 02:01 PM   #18
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Just one other tidbit I hadn't seen mentioned. Minds greater than mine told me that getting the injection done early was good for gas mileage since charge cooling isn't an issue for cruise. An early injection lets it sit around and recycles the heat in the valve/head to help vaporize the fuel before the intake valve opens. Not the best for power, but gets the most out of the fuel.
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Old 03-02-2012, 11:33 AM   #19
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Edit:
Reading comprehension fail.


Does anyone have a tested EV14 550CC injector table?
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Old 03-02-2012, 11:38 AM   #20
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Quote:
Originally Posted by Braineack View Post
Why does your fuel load go to "200%"? How can you have more than 100% fuel load? Dividing by zero?
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MS2/3 Injection timing maps for sequential injection-injection_timing.jpg  
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