Prolly a retarded question, but where can I tap into to find a boost only line(positive press) and no vacuum? Should tap into one of the intake IC pipes right or inbetween the s/c and FMIC?
Right now i'm tapped into the line going from the back of the LS6 manifold to the brake booster....am I in the right place? My boost gauge only reads boost no vacuum so I can't tell

J

 

Your fine where you are.Just because it doesn't READ vacuum doesn't mean you can't hook it into a vacuum source.

 

Cool, just wanting to make sure I had a good boost referenced line going to my adj FPR(boost referenced)

I read that if you had a line that was seeing boost/vac going to the adj FPR that it wouldn't work well.

Thanks Don
J

 

Jer, when i was laying arounf with my FP on my BR Reg. i was seeing vaccum because i was seeing the vacumm drop my base FP then it would rise with boost when i went into it..... i didnt really like that...... BTW the kit is almost all the way of the car now....
Kyle

 

I wouldn't hook any vaccum to your regulator. It will drop you fuel pressure at idle and cruise. I wouldn't think you would want that unless your tuned for it. Get you boost reference from anywhere between the the front of the throttle blade and the outlet of the charger/turbo. That will give you boost only.

Frank

 

if you have a boost referenced regulator i think it would be easiest to let it pull fuel presure under vacume. basicaly keep the actual fuel presure diference between the rails and intake the same at all times.

my truck has the stock fpr set up. base presure is 60psi, at idle i see 49-50 and at 15psi i see 75psi of fuel presure.

 

Great info and advice fellas. I am seeing a dip in FP right at WOT the it starts to compensate and rise....but the ol LM1 wideband shows the lean spike and I reeeaalllllyyyy don't like the feeling that gives me or my pistons. I have it set at 58 psi base pressure, at idle or cruise it drops to 51-53 psi....and WOT it drops then goes up...

I was reading that if you have a line that see's vac/boost the the vacuum will pull on the diaphram of the boost referenced regulator and cause the dip and skew readings all the time.

I will tap into intercooler pipe and go from there. Bet that does the trick.

Boosted one: I LOVE YOUR CAR. There is a local here with the same ride with a D1-SC on what he says is a mild build small block chev...damn thing runs easy 9's every pass I can't get past the looks of the car, it just looks like a street strip killer. I agree with you and what I read, got a project to do for tomorrow while continuing the N2O install.

J

 

Even if you don't dip slightly in fuel pressure when you go WOT, the afr will probably go real lean for ~.2 sec. I had to drop the PE mode enable tps in 45-50% range instead of the stock 62%.

Gary

 

I think the problem is when your cruising the vaccum is dropping the pressure and when you nail it, the charger makes boost pretty fast and the regulator has a hard time going from pulling pressure to adding pressure. I think if you do a boost only line it will fix your problem.

Thanks for the compliments on the car. Hopefully I'll be squeezing out some 9s by the middle of next year. I wanna try and do it on a stock bottom end

Frank

 

I thought it was common to use a one way check valve in that line so that base pressure was not hit by the vacuum...

 

if your going with a return style fuel system why wouldn't you want your fuel presure boost/vacume regulated? it will make tuning much easier having consistant fuel presure across the injector. the regulator is pleanty fast, if you are geting a lean spot then that is in your tune.

 

Not common enough for aeromotive to warn you or provide you with a one way check valve with the Boost referenced ADJ FPR(guess the 1.50 cost is too much for aeromotive?). Going by the responses above, i'd say it wasn't common knowledge here until now. I read up on this tip in the latest hot rod. They were having the same problem, and aeromotive was put on it and told em how to fix it....run the line to a boost only side.

I'll go get a check valve from NAPA tomorrow to see if that will be an easy fix....they sell those lil blue and white ones on that goofy spinny tree thing.
Thanks xssive

Frank, i'll do an update to let you guys know what happens...going to try the check valve xssive rec'd above.

Keep us posted on your progress, sounds like fun...and push that stock bottom end, it can handle it


Gary, hows that part of NM this year? I'd try to do some editing but I dont have access to my edit stuff or efilive stuff...its in a cold chicago PO BOX awaiting HP tuners to replace it with a new HP tuners cable and software

J

 

Hi Jim, well its worth a try....I'd try to tune it out, but the edit and efilive are in chicago getting replaced....so i'll try the check valve. But the dip in FP corresponds with the lean condition on my incar wideband. It goes hand in hand, step on it-FP dips-wideband goes to 16-17.1 then richens back up with the onset of boost. Won't be too tough to see if this works or not.
J

 

A little more reading:

Aftermarket Turbo/Supercharger Regulator
Two adjustment are necessary with this regulator. NA engines that are subsequently fitted with forced induction often exhibit extreme leanness in the range of 4 inches of vacuum to approximately 3 psi boost. The cause for this is that the turbo/sc can achieve atmospheric pressure in the manifold prior to the throttle being fully open. Without full opening, the throttle position sensor will not properly inform the ECU of what’s going on, hence, a lean condition occurs. This is not as prominent in later model ODB2 automobiles where the O2 sensor feedback covers a broader range.

Pressure calculation: the fuel pressure required increases with the square of the boost pressure ratio:
Example: 6 psi boost is a pressure ratio of 1.41. With stock fuel pressure of 36 at zero boost, than:

Needed fuel pressure = ( PR2 x 36) + boost = (1.412 x 36) + 6 = 77.5 psi

The first adjustment is of fuel pressure is at the atmospheric pressure point, and can best be done at idle. To simulate passing through the zero point, the vacuum line must be removed from the our FPR. The FPR then sees atmospheric pressure as a signal, same as zero on the boost gauge. Control of the fuel pressure at the zero point is by the Allen screw in the center of the FPR. Clockwise on the screw will raise the pressure. Once adjusted, plug the vacuum line back onto the FPR and observe the fuel pressure drop to the stock figure. A suggested pressure for starters is 48 to 50 psi.
Please understand, this will vary from engine to engine, and is not a magic number. The “magic” number is whatever pressure your vehicle requires to pass thru the boost onset without the lean flat spot. It is not unusual to see pressure anywhere from 40 psi to 55 psi. Use whatever works best.

 

We ran a regulator hooked up to the manifold for about a year on Pure Evils car and it worked great. Base pressure was 45psi,cruising was 40psi and it went to 55-60psi at full boost.No problems at all.
My Grand National runs like that.
All the supercharged Mustangs I do run like that..

Of course you have to tune it in right by locking the injector flow rate table and minor VE table work.Not very hard to get done.

 

Locking the IFR table as in setting one single IFR number all the way across?

 

yess!

 

I have a locked IFR table file that I was going to try, but the scaled IFR table was/is working awesome....not much I can do about that until the HP tuners arrives sometime next week hopefully.

I'll be doing the boost only mod here in a while lets just see what happens for ***** and giggles.

Don, i've been running the car like this all year, the car has been fine but that 1 sec(if that) of leaness always bugged the hell out of me. The car never missed a beat when this happened so its something that irks me.
I'll work on the tune when my hp tuners gets here...nnnnooo more edit for me.
J

 

Well did the check valve expirement today....got back from a short hop, and the fuel pressure didn't ever drop below 56psi...it would normally go down to 52psi cruising. The FP just stayed there
My a/f also didn't take a hit and go lean when I got into the throttle. It was adjusting like it should...meaning "hey boost is here...better start richening up"

Here is a pic:


It was 4.99 from the local NAPA PN 730-1347.Thanks to my big bro Eric for buying the check valve for me and suprising me with it
I just installed it backwards so it would keep vacuum away. I don't know how long these lil valves will last under my full 15-16psi but time will tell. It did prove that these boost reference fuel pressure regulators need to be hooked up to a boost only source...well atleast it did for me.

I'm happy now, the damn lean spike is now gone when going WOT, boost and FP rise together right away instead of boost hitting, FP drops then starts to pick back up.

FWIW
J

 

Nice, glad it worked out for ya!