400Z28Racer

iTrader: (4)

I am going to build 400 sbc next month. I'm confused about the fuel system. I am going with fuel injection but the question is Should I go with TPI SD (Batch fire) or CSFI out of 98 Vortech(Sequential fire)?
Thank you in advance

formula_novice

iTrader: (1)

Z28 DUDE,

I am an amateur when it comes to fuel injected vehicles (just wanted to make that clear - LOL).

However it is my understanding that, because TPI is a batch system, the injectors spray fuel simultaneously. Whereas with the CSFI (Sequential fire), the fuel injectors spray fuel individually (when it is needed per cylinder). Thus creating a sequence.

I would think that CSFI would be the better way to go but, due to my limited knowledge, I will leave that advice up to the experienced forum members.

Hope this info helps.

Nixon1

I don't know the difference between batch and sequential fire either, but I can't imagine batch means it fires all injectors at once. That means, for example, it would fire when one cylinder needs it, but another cylinder might be on its exhaust stroke. That wouldn't be good, having a cylinder get fuel when it's not even sparking, just pushing the exhaust gas out. It's be pushing that gas past the valve and trashing your oxygen sensors, etc. And possibly compression detonating the gas left in the cylinder and creating a nasty detonation.

crazycrocket

Okay there is not going to be detonation.... the batch fire is as far as I know all injectors are spraying (like a carb always gives gas) if the intake valve is closed then no air/fuel mixture goes in.... remember how short the intake valve would be closed..... sequential fire is when the injectors squirt in tune and the computer is able to control each injector individually and tells them to squirt in an order so that the injector is only squirting when it needs to be....

at least this is my understanding

formula_novice

iTrader: (1)

I did manage to find a small bit of information about this topic on
http://auto.howstuffworks.com/fuel-injection4.htm that states,

"There are two main types of control for multi-port systems: The fuel injectors can all open at the same time, or each one can open just before the intake valve for its cylinder opens (this is called sequential multi-port fuel injection).

The advantage of sequential fuel injection is that if the driver makes a sudden change, the system can respond more quickly because from the time the change is made, it only has to wait only until the next intake valve opens, instead of for the next complete revolution of the engine. "

I know this article doesn't mention TPI, but it is my understanding that TPI is a form of multi-port fuel injection (someone please correct me if I am wrong).

You might want to surf around the web, Z28 DUDE, if you need more technical data. Thanks.

mrr23

batch fire = one bank at a time. left then right

sequential fire = individual injector firing one at a time.

8Mike9

Batchfire (as in our TPI's) fire all 8 injectors at the same time. The ECM only has one QD to operate all 8 injectors. The confusion about left-right..etc, could be due to two fuses, one for each bank.

One thing to note about sequential is that at WOT, it becomes "batchfire". So the only advantage (and slight at that) is cruise RPM's.

Nixon1

PS....Z28DUDE......so much for the secret project huh? Don't worry, I won't tell anyone.

mrr23

then if it fires all 8 at one time, then why two leads out of the ECM? as seen here from my ECM? i'm not the brightest, but?

8Mike9

If you look at the schematic of the ECM, you'll see those two leads connect to only one QD.

400Z28Racer

iTrader: (4)

Thank you guys for the input. I am going with TPI set up, and I was told that it's not smog legal for CA, and it doesnt fit anything except Vortec heads. It's also not any better than TPI for performance.

400Z28Racer

iTrader: (4)

No No I was talking about my other car (non secret project)

91GTABird

So everytime my ECM sends a signal to open a/the injector(s), it sends a signal to ALL 8 injectors at the same exact time?

If yes, does that have any relation to when you go to start your TPI and it takes a moment to start, but when it does it revs up and then right back down? Dont know if i worded that right.

I am talking about speed density if that matters.

Also if yes, then what does the cam dur. and lsa have to do with the cam being ECM friendly?

And one more thing. When you get fire for the injectors and #1 plug fires then #1 cylinder gets 8 times the fuel on its next compression stroke?

1-8-4-3-6-5-7-2

dans82bird

batch fire - fires 4 injectors then the other 4....

sequential - fires each individually according to which cylinder needs it.

sequential would be a badass swap

formularpm

Id say you dont have any choice but to go with the batch fire system, the sequential Vortec system is OBD II and probably wouldnt work with a lot of fabrication. It isnt worth the work involved just for better fuel mileage.

Ed Maher

No, as already explained my 8mike9, batch fire means ALL 8 injectors go at once.

We are quite aware there are 2 wires, and even 2 fuses for the injectors on these cars. We also know that the 2 wires connect to one spot in the ECM.

Nixon1

Wow...what a crappy system. But hey, I guess it works. I'm surprised GM didn't go sequential on the F-bodies. Ford did on the fox bodies....

mrr23

they did in 94

Nixon1

Few years too late. (Ford started sometime in the 80's, in the 5.0 HO...) But I can't bash GM...they were my first love. Still wear my Chevy Racing hat. Although I have to admit, I love Ford motors now. Cant blow em up.

formularpm

Well, its still better than a carburator or TBI. There isnt really anything wrong with the system when it comes to making power, and thats what most of us care about.

Nixon1

Very true.... Although a carb is unbeatable for simplicity and they're so cheap to build.

8Mike9

I just know there's a joke in there...something about not being able to make enough power to spin high enough to come apart, but I'm not gonna say anything

Nixon1

Hehe...hey, believe me, I used to bash Ford. But trust me, if you had my motor, you wouldn't. That motor held together up to 6500 rpms, and ran a 14.5 at 95 with ruined piston rings and a bent connecting rod on Cylinder #8 that dropped compression on that cylinder to 125 psi. I didnt even know about the rod until we got the motor torn apart to do a head and cam swap and discovered how trashed the thing was. Looked like hell. That's when I ordered a new crate motor.

fisherbody86

HOLD ON, lets not beat up on batch fire here. Batch fire is great, and doesn't hurt performance at all. In fact, since you all were surprised to hear that TPI was batch fire, I bet you are all thinking now "hey, my car runs pretty damn smooth, i guess batch fire isn't that bad after all." TPI is batch fire, it fires all 8 injectors at the same, it makes great power, and fuel milage is pretty damn good. Sequential and batch fire make the SAME POWER, and get just about the same gas milage.

There are plenty of guys out there with huge HP numbers out of their TPI, and they are running batch fire, so whats the big deal.

Dave Y

yes, but 1 QD can control 4 different devices seperately, hence QUAD = 4

and the TPI batch fire controls the banks seperately

8Mike9

Grrrr....

fisherbody86

score one for Dave. And don't forget that there are 2 injector quad drivers for the speed density setup. TPI fires 4 at a time, left bank and right bank.

400Z28Racer

iTrader: (4)

SFI does not have an advantage over TPI when it comes to gas mileage, idle quality and emission. The SFI has better fuel atomization and reduction of fuel puddling. The SFI has ability to tailor injector timing and pules width to each individual cylinder can increase engine durability under prolonged WOT operation because it reduces the chances of lean cylinder even more than batch fire.

Apeiron

How does it fire a bank at a time if there's no camshaft position sensor to tell it which bank to fire?

Ed Maher

And as soon as Dave and company answer that one, they MIGHT have a leg to stand on.

They might then also explain the timing strategy used to get all the fuel out in half the time since they think that only 4 are actually going at once. Considering that eats half the available DC, i'm very interested in this one.

formularpm

How is this possible when the ECM only recieves data as an average from each bank? In order for this to be true you would need an O2 sensor for each individual cylinder, otherwise there is no true input as to whether a single cylinder is rich/stoich/lean. Correct me if Im wrong...

8Mike9

In the interest of fair play, when I put my heads back on in a few weeks, I'll be happy to hook up my scope (dual trace) and monitor the PW of each bank. This will be on my 165ECM. What I can do in the meantime this weekend, is verify continuity between Inj drive pins on the ECM.

I'm sure anyone with a SD car can do the same, if they have access to a scope.

Also, I've been told that SFI goes batch at WOT, belive it was Glenn (see him mostly at the PROM Board) who mentioned this.

One more note, if the injectors fire one bank at a time, this would be "Bank-to-Bank" or "Semi-Batch", not "Batch Fire".

Since I don't have a schematic of a 730 ECM, I can't comment on two QD's or not, but the schematic in my Helms for the '165 ECM, shows one QD...one switched output from it...to each Inj line.

Edited:

I might add one more thing...I just looked at my ECM schematic and noticed only a single switched device..."Hmmn, I thought" so I did a search at the EFI_DIY site, come to find out that the injector driver is not a Quad Driver, but a CMOS FET transistor (only one switched output available).

fisherbody86

To answer dave and aperion's question, the ECM knows when to fire the injectors off of the distributer pulse reference. Sure there's no crank sensor or cam sensor, but it still runs, doesn't it. You don't need a cam or crank sensor to run batch fire, and actually you don't need them to run sequential either. Case in point: Vortec injection.

Go unplug the cam sensor from your vortec truck and start the engine. It will run, and it will fire the injectors in the proper sequence. The only thing that will be different is that it will not know which cylinder to start the sequence on. So it will just guess and start firing the injectors. It knows crank position, but not which cylinder to fire first. So there's a 1/8 chance it starts it on the right cylinder and a 7/8 chance it doesn't.

Some of you guys sound like you don't believe that batch fire injection is even possible. It is. It works just fine, your tuned port motor runs, doesn't it? TPI is batch fire, period. There is no question about that.

Batch fire doen't need to know cam position, because it knows crank revolution speed. From that it knows how often to fire the two banks, and knows how far apart (in degrees of crank rotation) to fire them to make them fire every 360.

GASGZLR

Maybe you could go with TPI and sequential fire if you got an aftermarket ECM.

8Mike9

My friend,

Have you beeen following this thread completley, or bit's and pieces?

Thre was one minor reference to Batch fire and "crappy"...it's long sinced passed.

Have you even read what I said?

You say "batch fire", then say "how often to fire the two banks, and knows how far apart "

That's Bank to Bank, NOT Batch fire

The discussion has evolved into how
exactly it works...not how well, etc...

Please don't tell us what you think, tell us what you know, and how you know it.

Cool?

I could make assumptions all day based on numerous factors that the ECM could see, but won't.

Or maybe you'll answer Ed's question? Based on fact, not opinion.

91GTABird

Since its batch fire, then what does the cam dur. and lsa have to do with the cam being ECM friendly?

And one more thing. When you get fire for the injectors and #1 plug fires then #1 cylinder gets 8 times the fuel on its next compression stroke?