FREE MPI help!

[GMalatrasi]

Ok guys... I'm trying to understand this this fully before I dive into anything.
So why exactly is it better to have extra injectors?
It seems logical to assume that getting bigger injectors is easier.

 

[terbow]

cause bigger primary injectors require tuning to get idleing properly. for example, your ecu puts out so much voltage to say, hey inject for .32ms, but that same amt of voltage on a larger injector will put out alot more fuel. thus causing an idle issue. plus our car dumps fuel so who knows what will happen with larger injectors when it hits boost. (pre tm hitting)

so while yes u can tune them, at a certain size they become hard to control unless you have a standalone, the mpi's resolution isnt high enough to get it jsut right, it will work but its just easier to get extra injectors so when u hit boost u can just add fuel and not even worry about idle. its just alot easier.


this is just for a basic idea. im not getting technical cause theres no point really.

 

[GMalatrasi]

Ok I see what you mean. Do you know of any drawbacksto the extra injector set-up?

If someone that knows or wants to get into the technical aspects of this IM me:
GpegasusM

 

[GMalatrasi]

Bump for more info

 

[GMalatrasi]

One more bump

 

[Moeed]

The only arguement that I have heard is that the fuel doesnt mix properly. I have no problems with that as none of my plugs looks dirtier than the other.
MPNick made a huge post about this. Its in the mpituner anyone thread.

 

[Crazee D]

Got install issues guys

 

[Crazee D]

OK MPI NA install
Step 13 refers to Red NA Module to RED /WHITE fuel pump wire.
Only problem is there isnt one.
The PCM #71 is the 12 volt key on and run.

It is White with a black stripe.

My other potential canditate for key on source include:
PCM # 97 WHite thru the firewall loom
PCM# 80 is PURPLE
PCM # 63 GREY

 

[Crazee D]

NA Module does not have short and long white wires
it has one white only and a brown unused

 

[BlkZoomZoom]

Did you check out the link big tim has in his signature? Step 18 is the wire you are looking for. It has nice detailed pictures where it is located.

 

[terbow]

indeed. its under the shifter plate (red white wire) and to the left

 

[Crazee D]

indeed. its under the shifter plate (red white wire) and to the left

Gracias Tonio

 

[Bigg Tim]

Like they said, only put the red TM wire to the wire under the console. As for the white wires, yours is NA, so it's a bit different. Go by the instructions that came with it.

 

[GMalatrasi]

Bigg Tim could you explain why it's recomended to run the extra injector set-up instead of the bigger injectors? I dont mind if you need to get technical.
Thanks

 

[altspace]

indeed. its under the shifter plate (red white wire) and to the left

Now go figure.

 

[bazooka joe]

Gracias Tonio

did you find it? it's critical that you have right wire? let me know...i actually have a pic too, if you need it?

 

[Crazee D]

OK gonna head out to Wellfleet ASAP
still leaves one problem

NA Module does not have short and long white wires
it has one white only and a brown unused

 

[TurfBurn]

you pmed asking for help, but I'm not seeing what question you need answered... can you clarify??

 

[TurfBurn]

Bigg Tim could you explain why it's recomended to run the extra injector set-up instead of the bigger injectors? I dont mind if you need to get technical.
Thanks

Everyone has opinions on this and there is no "right" answer contrary to what some will try to maintain. It also depends a lot on execution of the setup. Keep in mind that a stock evo or SRT-4 Stage 3 or the like run larger than 440 injectors and have no problems with startup, idle, or emissions (which are the "usual" items that people argue are problems with larger injectors). The big problem or issue that you usually run into with big injectors is that at low idle speeds and low mixture densities it is often hard to get a small enough injection of fuel from the injectors to get a good burn for emissions and idle. this can be compensated for with EGR, cams, etc... so it's not a major issue. On our cars you can run into a little difficulty but there are plenty of us running 550's and larger that have great idle, startup, etc... so again it's all about setup.

That said... then the discussion for extra injectors REALLY depends on execution. The best possible situation is upstream individual runner extra injectors. If you put a large injector up stream on each runner you'll get a cooling effect from the fuel as well as better atomization and vaporization which will lead to the ability to produce more power and in some cases reduce knock as well. That is the ideal setup and infact many F1 cars run a single set of injectors very far up in the runners because of the intake tract speeds as well as the improved cooling etc you get. Now, the reason I comment about it being on individual runners is that you can maintain sequential injection and you ensure that each runner receives a metered amount of fuel. Pre-TB or plenum injection is NOT as good for that reason. While it works pretty well, and it does provide some of the cooling benefit, and it is definitely more simple, it does NOT lead to even mixtures being delivered to each cylinder in many cases due the flow patterns of the air and the levels of atomization and so forth. This can lead to enough differential that a particular cylinder can run more lean and be more prone to knock.

So that all said, it is typically best to go larger injectors unless you have the money to do a good secondary rail in further up on the intake runners. I'm not 100% sure how well the MPI can handle each of those scenarios, so I leave that to Tim and the like that are more experienced with the MPI.

Hope that helps!

Later,

Steve

 

[GMalatrasi]

Hope that helps!

Later,

Steve

Yes it did... Thanks

PS: Would you know what size injectors I need to run 6psi on a GT28RS and not max them out? 440s or is there something between stock injectors and the 440s?