Well, Ive had the 2k for about a month now... I am very happy with it. Always been a "old truck" kinda person until now... All that emission stuff and the fact that I couldn't do as much myself without some special this or that.. At any rate while looking into the facts of the engine I have in this Blazer, I came across this>>

Central Port Injection (CPI)
General Motors developed a new "in-between" technique called "central port injection" (CPI) or "central port fuel injection" (CPFI). It uses tubes from a central injector to spray fuel at each intake port rather than the central throttle-body. However, fuel is continuously injected to all ports simultaneously, which is less than optimal.

GM refined the CPI system into a sequential central port injection (SCPI) system in the mid-1990s. It used valves to meter the fuel to just the cylinders that were in the intake phase.


I would like to know if anyone can tell me if the CPI can be converted into the SCPI without to much pain. Seems to me that it is much more effiecient with the gas bill at the end of the month as well as performance. I am not any top wrench or close to it. So if I am speking out of turn, or anyone can tell me in much more detail the diffferences and facts around the different engines I would like to know more.
I was reading about doing a mod on a TB and from what I have read, the CPI that I have is different and can't be modified in this way.. Is this true? Is there another way or ways to modify this engine in the intake area? If there is a link or URL that you can turn me in the direction of please do.

Thanks again in advance for any help....

 

You already have the SCPI which has 6 injectors in a centrally located injector pack with tubes running to poppet valves down into the intake runners right before the head. GM has made a change to this however. They have released an MPI version that is a direct replacement for the SCFI injection system. THe MPI spider has injectors right down at the intake runner instead of a central injector and poppet valve for each cylinder. Much less to go wrong as the poppet valves on the SCFI injection systems tend to get gummed up and sticky. If I ever have to replace mine, I'll be throwing in the MPI system.

Now onto the throttle body mod. The actual mod is to cut off the deflector plate on the throttle blade. I have done this and to be honest, I think I'm going to revert back to stock. The implications on the part throttle flow of EGR gasses in the intake are enough to make me think twice about it. Not to mention that the deflector really did nothing at WOT (wide open throttle). It only improved throttle response at low throttle angles. I'll have a better idea of what it did when I revert back to stock.

 

"THe MPI spider has injectors right down at the intake runner instead of a central injector and poppet valve for each cylinder. Much less to go wrong as the poppet valves on the SCFI injection systems tend to get gummed up and sticky. If I ever have to replace mine, I'll be throwing in the MPI system."

When did the MPI come in and is it possible to convert one of the SCFI's like I have now into one? Can just a different top end, i.e. manifold, and whatever other parts are needed be installed to accomplish this?

Thanks...

 

Actually, I stated that wrong, it's MFI, not MPI.

Anyway, yeah, it is designed as a direct replacement for the CSFI spyder. PNs as follows:


[IMG]local://upfiles/667/BBF4237A74E64CBF99A1F206F856BDDF.gif[/IMG]

 

Might also want to add:

 

Forgot to ask what model year did they introduce the MFI into regualar production to the public on the MFI
I mistakenly sent this too early just now sorry...

 

Fixed it for you.

It is possible that this was utilized mid model year 2002, but I can not find any information to verify this. The TSB on the CSFI to MFI convertion only applies to 1995-2002 s-series trucks/suvs (plus other models with the 4.3L, 5.0L, & 5.7L engines). I would think that this is when it was switched over. The TSB is dated Feb, 2003...

Anyway, on the price, GMPartsDirect.com has it at somewhere around $150 +S&H but they'll kill you on the S&H. I would give a call to your local dealership to see what they would charge for it. I will be calling my local AC Delco store to see their price. As far as installation goes, I had my plenum off and o-rings replaced in my CSFI unit in alittle over 3 hours start to finish, and that included going to the dealership to pickup the o-rings. If just replacing the spyder, it shouldn't take more than 2 hours.

Next time I have a problem with mine, I'm ditching it in favor of the MFI. Its cheaper to replace the entire unit with an MFI than it is to replace a single (or multiple) injectors on the CSFI unit.

 

Thanks for all this info... One last thing to ask is what will this changeover do for my mileage? Better or not?
TA

 

Nope, the only reason you should consider this change over is if you are currently having problems with sticky poppet valves and a fuel injection cleaning did not solve the problem.

If just looking for added benefit to MPG or power, this conversion will do neither. The CSFI is a good system, but the poppet valves do sometimes stick causing misfires etc. Now, if your current CSFI is malfunctioning with either a sticking poppet or otherwise, then the MFI spyder may regain some of your lost power, but will not deliver more than a properly working CSFI. The appeal of the conversion to me is that I won't have to deal with the sticking poppet valves again.

 

Is the TSB you refer to Document ID# 1234172?