Anybody want to explain detuning for me. I have 24lb accels along with the other mods in my sig and have been advised to detune. Without expending to much of my own brain juice trying to figure this one out, I imagine there are some FI gurus out there that can help me out!


Thanks in advance!

Marty

Don't worry, your brain's not a limited resource...you can use it all you want and never run out.

i dont know about detuning, that defeats the whole purpose of mods. you probably should get the injector constant in the computer chip changed from stock to 24.

yep yep, what he said, the PROM needs the injector constant set up.

works fine for me.......

Makes sense to me. Some folks on this board had recommended setting the FI to 21lbs. Just wondering why..in a semi-technical explanation.

What do you need a semi-technical explanation of. If you're changing the size of your injectors, the ECM *NEEDS* to know, so it will have an accurate idea of how much fuel is moving when it opens the injectors. You tell the ECM the size of the injectors in your chip. Buying the stuff to burn your own chips and making the change yourself is the cheapest and easiest way. Refer to the sticky post at the top of the board for some newbie tips on getting into chips.

If you don't understand why the ECM needs to know what size the injectors are, maybe you should stick to reading and learning before you start turning any wrenches or replacing anything. Not that FI is that hard to work with, but if you don't have a basic understanding of what is going on, you will probably end up causing more harm than good.

At 21psi, I doubt it will run at all. The lowest I've heard anyone running is 35psi & thats rare. If you are going from 22lbers (stock) to 24lbers, it will run richer than it did before. That may be good or bad depending on where it's at. The setup you are running should be tuned, if it has not been already. If it's good now the injector constant should be changed in the prom, otherwise tuning & prom burning is in order.

Hi Rick, I am talking about the fuel injector constant...not the fuel pressure; also Ed, I am asking this question because I burned a chip with the ARAP bin and want to dial it in.

I received the following response to a message I sent to craig moates.

.

If setting the Fuel injector constant to 24lbs (which is initially what I planned) then why are some of the other board members using lower FIC's?


If there is a somewhat ideal place to start with the fuel injector constant and fuel pressure given the experience of other board members with setups similar to mine, I would like to know. It is understood that some fine tuning will be involved as it is unlikely somebody has EXACTLY the same setup as mine.

The fuel injector constant is currently set to whatever is in the ARAP bin to begin with and the fuel pressure is set to 49lbs.

OK..I'm ready to start reading all of those replies.

Thanks in advance

If you don't have a scan tool to actually check what you are doing, i would think setting the injector constant smaller than stock would be a poor idea when you're running injectors much bigger than stock (24# SVOs are effectively 26# when you compare to GM)
I'll admit i don;t have any experience tuning MAF, or runnning the SVO injectors, but that seems very counter intuiitive. That doesn't mean it's wrong, but i wouldn't go blindly trying something like that either unless i was sure it was the right move.

Definately need to get a scan tool I think. Any recommendations ed?

For now I will probably just set the constant to 24 and see if anything seems to change for the worse.

Thanks for the replies.

I think the reason that Craig said to start at 21# is the engine mods you have showing in your sig.
I have 24# injectors in my car with a "similarly" moded engine also using ARAP, I had to set my constant to 22# to get enough fuel to run "properly" (I'm still tweaking it in) having the constant set to 24# made it run lean.

Morley...do you recall exactly what the standard FI constant is in the ARAP bin? Is changing it .2 or .3 going to make much of a difference?

ARAP Starts at 22.1#

isnt that FP a little high on 24#ers for your setup? I run SVO 24#ers on a blown G92 LB9 at around 42psi ( i cant remember its been so long since ive driven the car). My spray pattern probably looks like boner **** though.

The scantool I use to use was Auto-Xray. It displays inj. pulse width (if i remember correctly), knock retard, tps, etc etc.