JoBy

The thread discussing the 360 hp injector limit for TBI is now locked.

https://www.thirdgen.org/techbb2/sho...hreadid=106117


At the end there were some discussions about using vacuum referenced fuel pressure regulators to extend the usable range of the injector.

If many fuel pressure regulators are installed in series the one that wants to have the highest fuel pressure 'wins'.

I made a simple Excel sheet that shows the fuel pressure at different engine vacuum.

http://w1.601.telia.com/~u60113744/m...L_PRESSURE.xls

And a screen dump:



The blue numbers at the top are the WOT fuel pressure that the regulator is set at. You can change those and see how it affects the fuel pressure curve. That is the value you can adjust with the spring force on the regulator.

I used a combination of the stock regulator and a progressive 2:1 regulator in my supercharger installation.

JPrevost

If you read my 2nd post (15th down on the first page) you'd see that from the get go I was all about the fuel pressure but NObody seemed to hear me.
Anyways, I'm going to try and make my holley FPR into a vacuum referenced by tapping into the side of it. There isn't a sight hole so there won't be any problem getting it to be air tight. The only questions is how much will it effect the pressure! My guess is that it won't be much at all, maybe 2 psi at the most but we'll just have to see.

JoBy

If you have 17 InHg differance between idle and WOT then you will raise the fuel pressure by 8.3 psi. ( 17 * 0.49 )
That is if your fuel pump can deliver that pressure.

It will keep the fuel pressure constant over manifold vacuum instead of constant over atmospheric.

Somewhere your regulator should have a vent hole to the spring. make sure that you plug that hole if you tap into it somewhere else.

steve8586iroc

Jon, are you still running the stock Holley injectors, it sound that you are? Do you have access to any 350 or 454 GM injectors? Just thought it would be easier to use a GM vafpr and good set of injectors.

The new CHP mag said that GM made 314hp and 424ft tq with the HT383 using tbi. It just doesn't say weather it was a 350tb or 454tb. I also searched the web for more info but couldn't find any.

Steve

JPrevost

I bought this Holley about a year ago and it's got the delphi injectors, or so it seems from my sources.
I don't like the GM fuel pressure regulator because the spring doesn't have as much room for adjustment. It seems like there are a lot of people having to change the springs and I don't have the cash to change to different injectors right now.

steve8586iroc

I hope you can get it to work good, I would like to see you get your 1/4mi times down this summer and not go lean at wot.

Steve