I've got a number of points on the VE map of my '808 that are over 90% in the current state of tune and will go over 100% when I put the new head, cam, exhaust and intake on.

On my BIN, 100% VE is $FF, and that leaves me stuck with a 100% VE limit I think.

I was going to handle this by increasing the injector constant and then re-entering all the VE's with the same proportional decrease. Is this the way to go and if so, what other traps are there?

John

 

This is just my opinion but. . . set the injector constant where it's supposed to be and get larger injectors.

Since you dealing with WOT, or pretty close, at those ranges there are other ways to increase the fueling, but that wouldn't really be the correct way to compensate for injectors that are too small.

Besides, you would have to DECREASE the IC for your plan to work. It's one of the problems with the GM method.

I don't know 808 but I did experiment with offsetting the CC per cylinder (cubic inches) instead of trying to cheat with the IC for a bit. I thought maybe the changes would be more global that way instead of changing the IC.

It seemed to work somewhat. I didn't persue that direction very long, I just got injectors that could handle the HP I was making.

 

I'm assuming you mean with having changed injectors.
Then yes.
BUT, often, OK always, when you change injectors the linearity at short PWs will vary. So everything takes a rework. You will have the basic shape for the fuel curve, but it will change some.

There is just about no such thing as too much injector, other then not having control of the idle PWs. Marginal injector sizing just generates grief. Finding a cheap set of used larger ones, is always a good investment in my book. Even if not exactly what you want, you can afford to play with them to see where you are, and what might be your best answer. While mine's a lil over the top, running 60s in my 231, just leaves all sorts of room for AE, PE, etc etc. And having done it right, all my commanded numbers line up with the WB. Makes tuning so much easier, when you know where you're at.
You might need to look at the base BPC/BPW for the crank mode thou, if applicable.

 

First, have you checked your Duty Cycles to ensure that you are not getting close to the higher limits? Are you using an AFPR too? Sometimes that is just enough if you are in the low 90% DC range...but do double check your Duty Cycles to ensure that you are not running out of injector.

Also, cranking up the fuel pressure tends to have it's greatest effect at the high MAP/Load values and least effect at low MAP/low load values. This will avoid some of the pitfalls Bruce is describing as it will not have to rescale the "idle rpm" area as much, while hitting the high VE area (like you want).

If you injectors are okay and you are not running out of PW and already adjusted you fuel pressure, then yes, you can consider re-scaling the entire VE Table. I've done this on my car and it is not exactly proportional either; but it is do-able - involves work but nothing outrageous IMO.

Lastly, you would need to DECREASE the Injector Constants - not incorease it (if you are using a BIN Editor that uses Injector Constant like TunerCat). If you use actual BPW, it works in reverse and you would increase it. Just wanted to clarify.

It it makes you feel good, I did rescale my tables after I swapped to my Miniram (with larger injectors too). Initially, I had to "play" with the injector constant to get it where the car ran very close to 128/128. But didn't like the fact that my "injector constant" was quite different than what it should be rated at.

I wanted the constant back to be closer to it's true rating so it forced me to rescale the VE tables. The longest part of the process was taking the "nice long drives" to capture the data to adjust the tables. No biggie.

 

Good assumption. Sorry it wasn't clearer. Thanks for the advice.

I've put in 24# injectors (had about 18#) and adjusted for that by reducing the injector constant. It runs fine, but as you and Glen predicted, it is a little lopsided in the BLM's (down in the idle range- about 120 odd, and under open loop DE conditions- about 110). It feels great though- maybe better AE. I'll fix the bias problem later.

I don't need to do this to increase fuelling. I need to do this to keep tunability. When the new mods go on, the BLM's will go really high at high rpm values, because I won't be able to correct my fuelling with VE's over 100%.

The '808 injector constant KINJFLOW = litres/gm per sec. This may work the opposite way to your mask's IC.

Thanks Glen. I don't want to go through all the hassle of rescaling VE's if there's a better way. But are you saying you went back to where you started from and just fiddled the IC to put more fuel in for a given MAP?

It was late last night when I posted. Maybe the thing to do is just increase KINJFLOW, and edit the VE's individually as needed.

What do you think?

John