Batch firing injectors causing engine damage or bad AFR ?

[defrag010]

I was thinking of the effects a 4 cylinder engine has with batch firing injector pairs. That would mean that the injectors would fire on the exhaust stroke of the opposing cylinder. Wouldn't this be bad on the engine as far as either washing your rings out or dumping the injected fuel out the exhaust to screw up the AFR?
I know that a wasted spark ignition, which is similar, can't cause any damage, but dumping full amounts of fuel in the engine without combustion surely Does have an affect on it.

[defrag010]

Aaah... I totally forgot about the intake valves being closed on the exhaust stroke. duh on me.

Something in the back of my head is still telling me that batch firing injectors is a bad idea, though. I know that the underside of your valves commonly are red hot upon a high engine load, but what about when the car is first started and there isn't enough radiant heat to evporate the gas?
I guess that the material of the valve would play a role in this, also. Stainless valves have a lower heat transfer than most stock valves, so they won't be as hot on the stem side of the valve as would a stock steel alloy valve.

I guess the only thing I'm worried about is if people are having problems with batch firing injectors on their engine.

[efahl]

I guess the only thing I'm worried about is if people are having problems with batch firing injectors on their engine.

Well, let's see. I believe the majority of OEM installations through
the mid '80s to early '90s were batch, so with US auto production on
the order of 10 million a year, I'd guess that worldwide production of
batch-injected motors is somewhere north of 100 million vehicles. If
it didn't work, we probably would have heard about it by now.

--
Eric Fahlgren http://www.not2fast.com/

[defrag010]

that being unbeknown to me, what are some cars that are batch injected?

both of mine, a 1996 ram and a 1990 talon are multiport injected, so i didn't think there were any batch injected cars from any manufacturer.

[TT350chevelle]

Just because your engine is multiport, doesn't mean it is sequential. As far as GM goes, in 1994 OBDII or EEPROM computers were first used in the Corvette and F Body Cars. This was the 1st year for Sequential port Injection in these cars. So every MPI system (Tuned Port Injection) prior to 1994 was some form of batch fire setup.More here: http://www.fuelinjection.com/

Brad J.

[danman]

My 97 Escort is setup with sequential electronic fuel injection, which depends on a camshaft position sensor. Just for giggles one day, I unplugged the sensor, forcing the stock ECU to run batch fire since it has no idea which cylinder's intake valve is open. Here's the results so far:

- it took a couple days for the ECU to fully adjust
- starts quicker now
- better fuel mileage now
- no noticeable loss in power, even from 1000rpm and up
- slight rpm dip from idle at the instant my foot touches the gas pedal. This will stall the motor if I'm engaging the clutch at the same time. As long as I let it get past that split second dip, I can almost dump the clutch and it will pull away just like it did running SEFI.

This is after 1 week, 650 miles mixed highway/city driving. Cold start temps have been down to around 0 degrees F.

For that little tradeoff of the rpm-dip, I think I'll leave it this way until I convert to megasquirt.

[Tyler Townsley]

1990-95 ZR1 Corvettes (Lotus designed DOHC V8 wasted spark) are sequential and OBD1.

Tyler

Just because your engine is multiport, doesn't mean it is sequential.As far as GM goes, in 1994 OBDII or EEPROM computers were first used in the Corvette and F Body Cars. This was the 1st year for Sequential port Injection in these cars. So every MPI system (Tuned Port Injection) prior to 1994 was some form of batch fire setup.More here: http://www.fuelinjection.com/

[flyguyeddy]

ah yes, the LT5. what a beauty! i wouldnt mind having that engine in the back of my fiero.......

[edmcguirk]

Even sequential injection isn't really sequential all the time. The intake valve is only open about 25% of the time in a 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 over 50% of the time on closed valves.

ed

[64Vair]

I was thinking of the effects a 4 cylinder engine has with batch firing injector pairs. That would mean that the injectors would fire on the exhaust stroke of the opposing cylinder. Wouldn't this be bad on the engine as far as either washing your rings out or dumping the injected fuel out the exhaust to screw up the AFR?
I know that a wasted spark ignition, which is similar, can't cause any damage, but dumping full amounts of fuel in the engine without combustion surely Does have an affect on it.

Sequential fire, or bank fire, on a dyno produce about the same horse power. Most race cars are bank fire. For a 4 cylinder, you have only one bank, so batch fire would be fine. So far as the comment about if an intake and exhaust valve are both open, that happens all the time on each cylinder, it is called overlap. On a stock cam, the overlap is very small, and only a very few crank shaft degrees. This is done to help get all the exhaust gasses out of the cylinder. With a care cam, the overlap can be quite large, and cover a lot of crank shaft degrees. On a top fuel dragster, the amount of overlap is 72 degrees at .050 lifter rise! That is a BUNCH. Compare that to my car, with a mild street cam that has -8 degrees @ .050, (44 degrees @ .020).
Also, heat is not needed to vaporise the fuel, that is what the injector is there to do. In race cars all sorts of things are done to keep the intake and A/F cool. If you count on heat to vaporize your fuel, then you are going to increase your tendency to detonate, and will have to retard your timing, which will add heat to the motor, .... The air in the intake does not sit still. Even when the valve is closed, the air in that port is either moving toward, or away from the closed valve. This is where "ram tuning" coes in, and explains why motor cycles have such short intake runners, and some cars longer ones. Motor cycles run high RPM. Because of this the runners are shorter, so when the valve closes, the air piles up on the closed valve until it reaches high enough pressure, then it is pushed back away from the valve toward the lower pressure at the other end of the port, until the pressure at the base of the valve is then the low point, at which time the air changes direction and heads back to the valve. in a perfect world, the air will stack up on ht eback side of the valve again, and just as it is getting ready to move away, the valve opens and it charges the cylinder. Obviously, the higher the RPM, the shorter the runner needs to be to allow this to happen. Look at the 225 slant 6 engine from Mopar. The engine was slanted to improve torque. How does slanting the engine improve torque??? By allowing longer intake runners, so the "ram tuning" effect happens at much lower RPM levels.
See, it is really all very simple!

[64Vair]

I got a screen saying that there was an error and my post did not post. When I went back to look at the thread, it posted several times. Sorry about that! If an admin could delete the extras, and then this post, that would be cool. Of course, I know they are busy, and probably have lives outside this board, darn!

[flyguyeddy]

i believe the european escort turbo series II and I use a bosch k-jetronic setup, which if i can understand it enough, fires an injector all the time, reguardless of valve opening and crank position. like a hose. i think that the air meter is like the valve on the hose. so if you are worried about batch/bank fire, dont. its not worth the trouble to sit and think about. believe me, i have pondered it with my motorcycle, its a moot point.

my 87 ford EXP had batch fire from the factory. it ran fine

[MegaScott]

This thread is a Classic, Eric's post about the 100million US vehicles built with batch fire injection still cracks me up-

defrag010 wrote:
I guess the only thing I'm worried about is if people are having problems with batch firing injectors on their engine.

Well, let's see. I believe the majority of OEM installations through
the mid '80s to early '90s were batch, so with US auto production on
the order of 10 million a year, I'd guess that worldwide production of
batch-injected motors is somewhere north of 100 million vehicles. If
it didn't work, we probably would have heard about it by now.

--
Eric Fahlgren http://www.not2fast.com/

This is all true, and a conservative number, this is just US production, wordwide production is somewhere near 3-4 times that amount.

[lapuwali]

Yes, K-Jet was used on millions of Volkswagens, Porsches, and Mercedes in the 70s and 80s, and K-Jet isn't just batch, but pumps fuel in continuously while the engine is running. Works fine.

L-Jet was used on millions of European cars, and a licensed copy of it was used on millions of Japanese cars, from 1980 well into the 1990s, and it's batch fire. It also works just fine.

Megasquirt is also hardly the only batch-fire aftermarket EFI out there. Most of the aftermarket ECUs are batch or bank fire. Almost none of them do full sequential. Also, as has been pointed out many times, there are very few (if any) production EFI systems that are full sequential throughout the rev range. At max load, even sequential systems have the injectors open 80% of the time just to get the required fuel into the engine. So, one could make the argument that there are almost NO actual sequential injection systems in use. They're all batch once they're at WOT.

[keithmac]

Yep, I converted my car from K-Jet (Constant Injecton System), to Digi1 (Batch fire) to MS on bank fire.

People slated the k-jet for flowing fuel all the time but being hydraulic the throttle responce was perfect, just not that much use for forced induction and the air flap looks restrictive (allthough good for 200+bhp on a tuned n/a 2l 16v).

Only good thing about sequential injection may be better exhaust emissions at idle? (there must be some reson to use it?).

[efahl]

Only good thing about sequential injection may be better exhaust emissions at idle? (there must be some reson to use it?).

Yup, OEMs like that part of it. Race car tuners like "sequential" because it typically lets them trim each cylinder individually to account for less than perfect manifolds and ports...

[Hans]

Most EFI Land Rovers up until I think 2001 were all bank fire as well. The Lucas 'Flapper' and 'Hot-Wire' systems definitely, I believe the GEMS as well. The Thor-Motronic.... I don't know for sure.

-Hans

[streetpirate]

every car that is tbi and not multiport, is not running sequential injection.

[MegaScott]

Being a Ford freak, Ford started out EFI in 1983 with "CFI" Centralised Fuel Injection, of course used a throttle body with injectors in batch fire mode. In 1984 Ford first used a port style intake on the 2.3 turbo that used the same basic ECU in batch mode, in V8's a two piece runner manifold provided very even distribution due to equal length runners and injectors of equal distance from the valve. Later in 1988 they introduced Sequential injection using a signature PIP TFI distributer which gave a shorter pulse on #1 cylinder which supposedly gave an idle improvement and slight emissions improvement, though not many people could tell the difference.

I would say the biggest improvement in the Ford injection system was not sequential injection, but rather the introduction of a reliable Mass air system which allowed for changes in engine VE without having to change the tune, which gives the ECU the capability to keep the engine in tune throughout the life of the powerplant, because the intake air mass is being measured continuosly, therefore automatically compensates for minor changes in the engine VE and still run good.

[enyawix]

Is Batch firing injectors easier to setup? Crank pulse etc.......