SCC and CA18 Fuel Injection

[Xero]

I keep reading their article about the 4 engine options into the S chassis cars, and I get stuck in the CA18 part with this:

"...Nissan had to save computin gpower by switching from a sequential fuel injection to a batch fire system at high load."

What the hell does this mean and why is it bad, and how can it be fixed if it IS bad?

[Doogz]

I could be mistaken as i haven't really read anything on this in quite sometime, but if my memory serves me well then they are talking about how the injectors fire at high rpms. Evidently, when the car really starts screaming they do not spray the injectors in accordance with the firing order of the cylinders but let all the injectors spray at the same time or in a "batch". Sequential injection is by far the more effecient way and should allow for smaller injectors for a certain power level but i don't think batch systems are all that bad. I believe that is correct but as i stated earlier it has been a while for studying fuel injection systems.

[McAdam]

I am pretty sure that all factory systems hit a point where they switch to batch. Its a function of RPM. unless you have a super powerful engine computer (most are like, 16 bit) the computer can't keep up with every individual injector at like 5000 RPM. once you start screaming along at high RPM, it doesn't matter if its batch or sequential. but, when your driving around town and your just lightly applying the throttle, thats where sequentyial makes a difference.

hope this helps

McAdam

[Xero]

so...for, say, auto-x where I'm screaming along at high ROM 'cause there's constant cornering and shifting will not set me up for teh next corner, will that be bad?

[float_6969]

Ok, so here is the deal. Just as McAdam stated, most cars switch firing types at higher RPM's due to proccessor speed restrictions. Sequencial fuel injection is a form of injectin fuel into the head/intake manifold/combustion chamber in which the only time the injectors fire is when there is air flowing through the manifold. Batch firing does just as it implies, it fires the injectors in "batches" (usually 2 @ a time in 4 cylnders) which means you are injecting fuel into a manifold that isn't flowing air. The difference is that sequencial is supposed to be more effecient, and it is at low rpms/light load. The problem is that at higher rpms, the time that the injector has to fire is very small and it takes alot of info to get it fired at the right time. The computer even has to know the cam specs, and if you change them, you have to reprogram the ecu. The idea of going to sequencial firing of the injectors was because in batch firing at low rpms the fuel had a tendency to "pool" in the manifold/head. But at higher rpms, there is so little time between pulses, that the difference was negligible. For further clarification go HERE.

[Xero]

thanks much, that's what I figured after the initial post, and you clarified it even more, thanks doode,

[float_6969]

no problem. Glad to help.

[dareo]

So what about an SDS management system, is it going to have the balls to fire each injector to 9krpms?

[McAdam]

I beleive the SDS is batch fire from the get go. only super expensive stand alones are sequential. there is one out there that is tested on a 4 cylinder up to 10,000rpms for sequential firing. cant remember which one it is. i think its Australian. Microtech or something?

McAdam

[float_6969]

stock the SDS is capable of 9G's but thats it. They can make them to go to 15G's for an extra charge. All the info you'd need is here http://www.sdsefi.com

[iliketocrash]

so wait... SDS is batch fire at all times? even at low rpms? isn't this bad?

[float_6969]

NO!!! not unless you are really concerned about emmissions. If you are, a piggy back system may be better for you. Generally if you are going standalone, emissions takes a back seat to performance. Kind of a balance, and you've gotta decide where you want to be. Ofcourse it depends on how the test is done. I mean, you could always alter the fuel for the test and just make it run real lean and put a cat on. That should fix any emissions problems. Course that would be a real pain in the arse...

[iliketocrash]

so on top of poor emissions wouldn't it cause poor fuel mileage too?

[drumma022]

Yea, SDS can handle 9750 RPM, BUT your CA will more than likely NOT need that much. On low boost, my motor started to level off HP at 7000, and drop Torque at 6500. I see no need to be taking it up to 9000 at all. Unless you hold some secret that I am unaware of. Yes the motors can goto 9000 and SDS can handle it, BUT you wont gain any benefits from it.

[dareo]

It would just be good times to take it from boost to 9k. I would think with some porting/airflow mods more high rpm power could be arranged. And/or performance cam. Just being able to is cool to me.

[float_6969]

Once again, yes both of these won't be like stock. But once again, if you're concerned about them then standalone may not be for you.

[boost_boy]

Quote »Yea, SDS can handle 9750 RPM, BUT your CA will more than likely NOT need that much. On low boost, my motor started to level off HP at 7000, and drop Torque at 6500. I see no need to be taking it up to 9000 at all. Unless you hold some secret that I am unaware of. Yes the motors can goto 9000 and SDS can handle it, BUT you wont gain any benefits from it.[/quote] You're right! The SDS is batch fired at all times and can cause your little CA18 to drink fuel like a V12 with carburetors. If you're experiencing fuel economy is issues, just set the system's open/closed loop setting and this will allow the ecu to try and maintain stoichmetric by using your oxygen sensor as a reference. You can also set this to make feature cut off at whatever RPM you want, especially when you kick into real boost and it does work. I can't speak for all, but I think the SDS system is the best investment a CA18 owner can ever make. You have full access to all your engine's functions and you kinda become a semi-tuner as well.

[alfred183]

How much could a beginner CA owner in, say AZ, get SDS for?

[s13sr20chris]

batch fire will limit the injector pulse width you can hit. obviously, this just means getting bigger ones. motec(the best and most expensive) is sequential all the time.

[float_6969]

It's actually the exact opposite of that. With sequencial you have LESS injector pulse width to deal with. Batch firing has MORE pulse width to deal with. Because of this, with sequencial you have to use bigger injectors because you have to flow the same about of fuel in less time. Please read this link for more explanation.

[iliketocrash]

batch fire will limit the injector pulse width you can hit. obviously, this just means getting bigger ones. motec(the best and most expensive) is sequential all the time.

so where can i find info and pricing on the motec standalone?

[s13sr20chris]

i think you are giving too much to a website that has a little bit of conflict of interest. mainly yours and theirs. a true oem batch fire system fires two injectors at a time(on a 4 cyl engine) every other stroke. being that its a four stroke engine, thats twice per complete cycle. the idea is to use less computing power and be almost as good. it basicly makes an educated guess and is exactly right 50% of the time. some oem's dont use the true batch fire and use a random batch fire like the sds system. the usdm z31 is of this type. all the injectors fire at the same time. this is really a sloppy arangement and you wont find it in a modern car(stock) or any high end racecar. it will be found however in lower end modified cars. it makes sense as it is so much cheaper. i just wanted to make the point that sequential is actually better. the sequential system has just as much time to fire as the random batch system because it does not have to stop flowing at any particular time. the most important part is that all the cyls are getting their fuel at the same time (in crank degrees) of the cycle. if you fire all the injectors at the same time(irrelevant to crank) they are all getting their fuel at a different part of the cycle. this is prob not a big deal, but its big enough that f1 and other serious race cars stay away from it. just for the record, i am poor as all get out and would not have a problem using random batch fire on my own car.

google motec. you will find it.

[float_6969]

i think you are giving too much to a website that has a little bit of conflict of interest. mainly yours and theirs. a true oem batch fire system fires two injectors at a time(on a 4 cyl engine) every other stroke. being that its a four stroke engine, thats twice per complete cycle. the idea is to use less computing power and be almost as good. it basicly makes an educated guess and is exactly right 50% of the time. some oem's dont use the true batch fire and use a random batch fire like the sds system. the usdm z31 is of this type. all the injectors fire at the same time. this is really a sloppy arangement and you wont find it in a modern car(stock) or any high end racecar. it will be found however in lower end modified cars. it makes sense as it is so much cheaper. i just wanted to make the point that sequential is actually better. the sequential system has just as much time to fire as the random batch system because it does not have to stop flowing at any particular time. the most important part is that all the cyls are getting their fuel at the same time (in crank degrees) of the cycle. if you fire all the injectors at the same time(irrelevant to crank) they are all getting their fuel at a different part of the cycle. this is prob not a big deal, but its big enough that f1 and other serious race cars stay away from it. just for the record, i am poor as all get out and would not have a problem using random batch fire on my own car.

google motec. you will find it.

Actually, I think I'm giving credit where credit is due. That site contains a plethora of information not related to strictly their systems. I have no money invested with them and so there is no conflict in intrests. Yes it fires 2 injectors (and sparkplugs) at the same time, yes it is twice per 4 stroke cycle, yes it uses less computing power, but to state that it is sloppy is to stongly state it in my humble opinion. The SDS unit DOESN'T fire all the injectors at once. As you stated earlier, it fires 2 at one time. One cylnder is in it's intake stroke and the other in it's power stroke. The reason that it isn't found in modern cars is due to emission regulations. At low load/low rpms, it isn't very effecient at all. But in high load/high rpm situations, the difference is negligible. A sequencial injection system only injects fuel when there is air flow in the intake runner. Because of this, it doesn't start injecting untill after the valve opens and has to quit injecting before the valve closes. Because of this, it has much less time to inject the fuel and therefore requires relatively larger injectors so that it can inject the same amount of fuel in less time. It is true that the batch firing system injects fuel into an intake runner that isn't flowing air. But at high rpms (which the motor spends most of it's time at in a racing situation) the time that the fuel 'sits' in the intake manifold is inconsequential due to the space of time between the valves opening and the heat of the intake runners/head. I will be the first to admit that it's not the most effecient way to inject fuel into an engine, but it's by no means "sloppy". I'm sure that in modern race car applications they have the monetary backing available to create ECU's with the computing power to accuratly control fuel at high rpm's and fuel effeciency is enough of a concern to warrent it. As I stated earlier, if emmissions and fuel economy are of great concern to you, then the SDS isn't something I would recommend. If you have a limitless budget, then there are probabally more effecient systems out there. They ARE probabally sequencially injected. But there are alot more factors to take into consideration when tuning an engine with sequencial injection and if you don't have it tuned right then then whole point for using sequencial injection is now moot.

[boost_boy]

Daaayuuummm guys, this conversation is good, yet very intense! I can say this for one about the SDS system compared to say a haltech or dta, much less drama with installation and programming. My car and others that I've done not only idles without a miss, but aren't that bad on gas and is excellent on performance. I have yet to see any of my customers engines bow because of something I done wrong with their ecu's programming or some strange hiccups or whatever; i've seen this on many ocassions with other programmable systems. I would say it was the best $1300+ I ever spent. Screw the big $750 turbocharger or the $400 wastegate or the fancy $500 boost controller, the heart is in the computer that controls the engine and it's functions; and most guys wonder why their stock nissan computers with piggy backs or whatever are playing-up on them. I went this route route and spent big dollars with JWT stuff and all I can say is "what a waste of time". But I've evolved now and have no use for chip burning and plugging and unplugging of the ecu as well as reading codes to see why the car's performance is crappy. What I got for the money I've invested is a car with performance that's superb. And even though it's batch fired, hey if it works, then it works. I've been down the road that most of the guys here are going and sometimes I don't even comment because some of these guys are either financially stumped and have to work with what they got or just could care less about the good info and continue to post about how their cars are giving them hell (More power to you all that this pertains to). But I say if you can afford to step up into the world of performance and turbochargers, why short change yourself with a limited system like the factory ecu and crappy AFM stuff. And BTW, my car has fast idle, idle up and doesn't dump huge amounts of black smoke or hit some stupid fuel cut or speed cut; goodbye AFM and hello to map sensing. A motto that I admire is "Do it right or pay someone to do it" .

[s13sr20chris]

well see here we have another difference in opinion. thats exactly what forums are all about and i think its fun. i really like mass airflow meters. i can see a large amount of value for a map sensor in a strict race only type of car, but for anything that sees street driving i prefer maf. i also am partial to jwt ecu's. i like standalone and all, but jwt just rocks in my opinion.

[s13sr20chris]

here are some links just to check outhttp://www.tobefast.com/speedpro.htmhttp://www ... com/theese guys both say sequential is better(for more money of course)who's to say who is righthttp://www.fuelairspark.com/co.../001/this was done by some guy named lance ward at the Advanced Engine Technology Conferencehttp://www.bgsoflex.com/megasquirtfaq.htmlheres another one professing batch fireby the way i checked some other stuff on the sds website and found that they swear by pintle type injectors. russ collins of rc engineering says they suck and that lucas disk injectors are the best. all just opinions.so you see its all just water under the bridge. no hard feelings eh?

[boost_boy]

Quote »so you see its all just water under the bridge. no hard feelings eh?[/quote] Not at all. Whatever works for whomever!

[quest]

jwt works for some cars, but there are ongoing problems reported from many users. Talk about "sloppy" tuning ? ....for my $600, they must be fckn nuts. I'm not. Poor turn aroud too. Coming from the buick GN world of the $100 chip that had blistering performance / crisp drivability / good economy (sequential btw), I can only see that option as a joke.I can understand them tuning a "one size fits all" chip, conservatively, so they don't have a bunch of people screaming at them, but its by far not the best solution. Run rich, lazy timing, poor fuel economy ? no thanks

550s + safc + z32 afm + oe ecu works fine for ~350whp. You maintain the quality nissan controls. DSMs, same thing. No need to pay extra for knock sensor, idle up, etc.. Should you wanna push the envelope, say on race gas, and take control of your timing, you have other piggyback options - I have one I'll be trying, after the safc.

Around my way, we're all into swaps. I go the donor car oe wiring route, while my neighbour always go standalone. So I get a first hand view of many types.... their pro and cons, and on someone else's dime.sds, wolf, link, haltec, tec, ems, microtech, etc

For my starion, I'm going with a $7xx (shipped) import. laptop, ez display, and been roasting tires for a long time now. Not a single prob (thanks to the guinee pigs)

I'm budget concious, so I think many systems are way overpriced.Thats proof above..... and below.I thought this low dollar d.i.y. standalone is tooo cool... if u wit ithttp://forums.club4ag.com/topic.asp?TOPIC_ID=44697

theres alot of difference in opions. Educate yourself, then make your move. You'll be happy

[float_6969]

Not at all. Whatever works for whomever!

Ditto. I in no way meant any hard feelings by my responses. I'm ALWAYS up for an educated argument, and as always, when it comes to cars, alot of things are merely opinion and there is rarely a right and wrong.

[iliketocrash]

megasquirt is batch fired as well, or were you just pointing out that its cheaper?