C4 Fuel Injection Types

[Rob]

Can anyone tell me what later C4 years had "Multiport Fuel Injection" and "Sequential Port Fuel Injection" or are they one in the same?

 

[Geof180]

fuel injection

lemme see here.... from my young mind - multi port fuel injection refers to the fact that each intake port or runner has its own dedicated fuel injector....

sequential port fuel injection refers to the setup where a dedicated injector fires right before the intake valve opens - at each cylinder when appropriate....

you might be saying - geof - don't all fuel injectors fire right before the intake valve opens... actually no, there are several "old school" types of fuel injection... for example, simultaneous double fire.. this is where all injectors fire once per engine revolution... or grouped single fire - where there are two injector groups, with one group firing once per revolution...

to my knowledge rob, all C4s have the sequential multi-port setup... since they were designed for good fuel economy and performance, this is the best setup given the technology at the time....

i think this is right, unless someone else can lemme know otherwise... so when is the Corvette gonna become direct injected?? maybe i should start working on this now... hmm...

but first, i should prolly get this finite elements homework done...

Geof

 

[vettl83]

Except the Cross Fire cars, there throttle body injection. 84 CF 91 ZR-1

 

[LarryBible]

Multi Port indicates an engine that triggers injectors in "batch" mode. This means that all injectors fire at the same time for the same duration. Sequential fires each injector at the precise time for that individual cylinder.

I don't know about the later engines, but the L98 operates in "batch" mode. It works better than you might imagine, but the sequential system is slightly more efficient and leaves a cleaner plenum.

The '84 model with throttle body injection, is for practical purposes an electronic carburetor.

Any of these systems are far superior to a carburetor as far as efficiency goes.

Have a great day,

 

[-=Jeff=-]

85-93 had Batch fire/ Multiport..

94-96 are sequential.

 

[Geof180]

doh! :duh

forgot about the 84 with its TBI unit.... thanks for the info everyone.....

i have never heard of "batch" before.... i would like to learn more about this - where might i look??

Geof

 

[LarryBible]

Geof,

There's really not much to learn. The only basic difference in the operation principles between multi-port and sequential is the fact that the multiport fires all eight injectors at the same instant, for the same commanded time duration.

The sequential system is just that, it fires each of the eight injectors sequentially at the time at which the intake valve is beginning to open for that cylinder. The batch mode doesn't sound very efficient but it has proven out pretty well.

If you notice in an L98 engine, over time there will be quite a lot of crud in the plenum. With this fuel hanging around over the course of two engine revolutions, I think that's why you see this. I have never opened one up, but I expect that the plenum area in a sequential injection system is much cleaner. At least, in theory, it seems that it should be.

I have a very good manual on Bosch fuel injection for my other brand cars that describes these principles. I'm sure that it can be found in most any fuel injection publication that covers the Vette.

Have a great day,

 

[Geof180]

cool.. thanks for the info... is this book called bosch fuel injection and engine management ?? if it is, then i have it - just have not really read through it yet...

Geof

 

[WhalePirot]

My port injected, '90m ECM fires the left and the right injectors separately.

 

[geekinavette]

[

My port injected, '90m ECM fires the left and the right injectors separately.

:confused Did you toss the CFI for a TPI setup, or using a '90 ECM with the CFI?

Bill