Engine Management!
uk3:
Thread Starter
THE HAMMER
Joined: May 2002
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Q. Can I do sequential injection with MegaSquirt?
A. There are two common sorts of injection:
Throttle body injection - usually one or two injecotrs for the whole engine
Port injection (aka. Multi-Port) - one injector per cylinder
Then there are three common modes of injection timing:
batch - all injectors fire at once, but not timed to any specific cylinder event,
bank - ½ the injectors fire at once, then the other ½, and so on, but not timed to any specific cylinder event,
sequential - each injector fires at a specific point in the 4-stroke cyle for each cylinder (i.e., 8 independent timing events)
Throttle body injected cars are usually batch or bank fire, simply because of the geometry. Most port injection set-ups before the mid-1990s were bank fire as well (including GM Tuned Port Injection for the 305/350).
Sequential injection requires:
at least as many injectors as you have cylinders, with one dedicated to each cylinder (i.e., not a 4 injector TBI on a 4 cylinder).
as many injector drivers as you have cylinders,
and also requires a camshaft position sensor (a crank sensor is not adequate for a 4-stroke cycle engine).
However, sequential injection does not necessarily mean you are injecting into an open intake valve all the time. The intake valve is only open less than 30% of the time in a typical 4 stroke engine. Once you are trying to produce more than about 25% of maximum HP your injectors are firing for longer than the intake valves are open. If your maximum HP is correctly calibrated to a safe 80% duty cycle, your injectors are injecting well over 50% of the time on closed valves.
MegaSquirt has just two injector drivers (that can handle up to ten injectors each), and no provisions for a cam sensor signal, so it would be difficult to make it into a sequential injection system.
The benefits of sequential injection are that:
you may get slightly better mileage and lower emissions at low engine speeds,
you can tune each cylinder's fuel amount independently (if you know how).
The effect on maximum horsepower is generally negligible.
A. There are two common sorts of injection:
Throttle body injection - usually one or two injecotrs for the whole engine
Port injection (aka. Multi-Port) - one injector per cylinder
Then there are three common modes of injection timing:
batch - all injectors fire at once, but not timed to any specific cylinder event,
bank - ½ the injectors fire at once, then the other ½, and so on, but not timed to any specific cylinder event,
sequential - each injector fires at a specific point in the 4-stroke cyle for each cylinder (i.e., 8 independent timing events)
Throttle body injected cars are usually batch or bank fire, simply because of the geometry. Most port injection set-ups before the mid-1990s were bank fire as well (including GM Tuned Port Injection for the 305/350).
Sequential injection requires:
at least as many injectors as you have cylinders, with one dedicated to each cylinder (i.e., not a 4 injector TBI on a 4 cylinder).
as many injector drivers as you have cylinders,
and also requires a camshaft position sensor (a crank sensor is not adequate for a 4-stroke cycle engine).
However, sequential injection does not necessarily mean you are injecting into an open intake valve all the time. The intake valve is only open less than 30% of the time in a typical 4 stroke engine. Once you are trying to produce more than about 25% of maximum HP your injectors are firing for longer than the intake valves are open. If your maximum HP is correctly calibrated to a safe 80% duty cycle, your injectors are injecting well over 50% of the time on closed valves.
MegaSquirt has just two injector drivers (that can handle up to ten injectors each), and no provisions for a cam sensor signal, so it would be difficult to make it into a sequential injection system.
The benefits of sequential injection are that:
you may get slightly better mileage and lower emissions at low engine speeds,
you can tune each cylinder's fuel amount independently (if you know how).
The effect on maximum horsepower is generally negligible.
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Last edited by Slash; Dec 29, 2004 at 01:28 AM.
Thread Starter
THE HAMMER
Joined: May 2002
Posts: 5,184
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Originally posted by John
so is MS batch fire?
so is MS batch fire?
I know its bad. And i understand it dosent allow for trimming each cyl. My sds was batch fire as well I think. What is really what brings it back? esp when teh price is so cheap?
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My 2.3 has 76 lb/hr injectors running in batch fire mode and no IAC at all. It fired right up in the coldest weather we've had and ran pretty smoothly with my foot holding it at 1k RPM for 20 seconds before settling into an 800 RPM idle.
So why do I need sequential again?
So why do I need sequential again?
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g45 m1l34g3 4|\|d d|21v4b1l17y. 7u|\|1|\|g f0|2 HP 15 345y, 1f 7h475 4ll 17 \^/45 7h3|\| h0|\|357ly c4|2b5 4|23 7h3 \^/4y 70 g0. 7h3 5|220, f0|2 3><4mpl3, h45 b33|\| k|\|0\^/|\| 70 |2u|\| l34|\|3|2 1|\| 0|\|3 cyl1|\|d3|2 4f73|2 4dd1|\|g 4f73|2m4|2k37 1|\|74k3 m4|\|1f0ld, 45 much 45 5% m0|23 41|2fl0\^/ g035 70 7h47 cyl1|\|d3|2. 1|\| 7h47 1|\|574|\|c3, 17 3v3|\| b3c0m35 4 |23l14b1l17y 155u3. 1'll 571ck \^/17h 53qu3|\|714l, 7h4|\|k5.
slow
Joined: Dec 2004
Posts: 57
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If you only care about WOT and are OK with doing crude things like hold your foot on the gas for 20seconds before the car will idle, and run 5% richer accross the board to make up for an airflow imbalance, I'd say just forget the standalone, ditch the EFI all together and install a carb... beacuse it sounds like the kind of stuff I do when I tune my brother's dirt bike. 
Last edited by BOOST JUNKIE; Dec 29, 2004 at 08:26 AM.
