read every reply in this thread and you will find it:cool:

Anybody know the uncompressed height of the stock spring? Also where did you tap into for vacuum source?
I still can't understand how the stock spring is able to pull off 10psi at full vacuum when my holley unit (with a 22#/in) was only able to get 5psi before reaching it's min height. The difference is that the holley unit has a slightly larger diaphram and the spring is only an 1" tall uncompressed.

That's it right there. You just nailed it. Your bigger diaphram allows more surface area, which makes the effect of vacuum greater; there is more atmospheric force applied to the diaphram, because it has a larger surface area.

Further, the VRFPR spring I have is 1-7/8" tall, uncompressed. I can't measure my stock spring at the moment, because it is in my car. We're not lying to ya, I have 15 PSI WOT, and 10 at idle. I would suggest trading that Holley injector pod for a GM unit. The Holley stuff is junk (IMO).

Bump. This is a very good topic.

BTW, the new holley stuff isn't junk. It's delco electronic injectors, not the cheap chrysler crap. They changed ~3 years ago because of the problems people were reporting. It was costing them money so they switched. For this reason I actually think the new holley pod is better! The pod itself is smaller and the fpr is easy to adjust with a 4mm allen key. You can also change springs with a phillops without removing the pod.
BTW, all info I posted with the fuel pressure is bogus. It turns out my fuel pump was so weak it wasn't able to do anything right, let alone flow any fuel into the return line :) . I'll retest the results but with the last spring I was using and the new walbro pump I had a 28psi reading at idle!!!
Very good article, keep on top, maybe a sticky

I'm probably gonna get one of the TDS Fuel Regs in a week or so and I"m wondering how are you guys reading the Fuel Pressure. Obviously a gauge but how did you install yours?

my aeromotive reg is going on this month. the reg has 4 identical ports all from which i can run the FP gauge. the remaining 3 of 4 will get the exit/from TB. reg is downstream from TB and backs up pressure so to speak. i dont have a dual TB attached right now(have 2 single TB's; crossfire) but i believe the gauge needs to go b4 the regulator. seems the only option for stock dual TB is the feed line to TB. se z28boy.com as he has nice photos?

Howdy, Been reading some OLD post's about the vFPR mod. I have bought one but would like to change the spring in it. Do you still have a source for them? I am running a new HT 383 crate motor in my 3/4 ton 93 Suburban. I have the Turbo City TB and matched 68 injectors and also their chip. Runs pretty good but I know there is more. Thanxs Kevin in Kissimmee

Top down solutions. a sponsor on this forum.

adjusting
 

I just ordered the sprign and valve from tds. I have 1 easy..easy question. To adjust the fuel pressure up do i turn the hex nut in or out?. With the stock heavy spring it didnt matter which way i adjusted it... it was 18lbs with no vacuum and 10 with vacuum. Now i believe it has to be turned in to move pressure up but i wanted to be sure so i didnt waste time.

Thanks guys this article was a big help!!!

You're right. In = more presure.

I have the VAFPR, and the spring from TDS. I'm waiting on an autometer fuel gauge I ordered from Jegs. I held the VAFPR up to my injector pod and it looks to me like the vacum hose will go directly under the injector! Hope I can bend it without breaking it to get the vacum hose on it without it getting in the way, even if I bend it so I can run the hose off to the side, it will still block Air flow to my self ported throttle body(all ultimate tbi mods)

Re: adjusting
 

sorry, please delete this post it wouldn't let me.

i cut mine off with a dremel and used a small ty wrap to secure it on nipple . can you run the vac line straight up vs. down and then out the base and then back thru the base once again to vac source? that is what i did but i had a crossfire. other option is to run i believe where the injecor wires run? i think there are photos posted here somewhere. you are right. impedes airflow somewhat.

I heated the nipple w/a propane torch and bent it to the desired angle for my application. Worked like a charm. I had a CFI also.

-Tom

You can also just reverse the bowl on the pod itself. All that you have to do is grind off a small part of the outside edge so it will fit back on the pod. After you do this the tube will be on the passenger side and will be facing backwards. Or u could just cut it off at the begining of the bend in the tube and just put your rubber tubing over the nipple thats left.

Ok I got the VAFPR, the new spring, and the vacum delay valve all from TDS a few weeks ago, I waited to put them all on until I got my autometer fuel pressure gauge. I got it and installed everything here is the problem I'm having.

With the VAFPR, the new spring, and the vacum delay valve, and the VAFPR at 7ish turns or so from flush:
I'm getting 9psi at idle with everything on, but when I give it throttle I get no inscrease in fuel pressure at all it just sits dead on 9psi. I unpluged the vacum line just to see if it made any difference and it jumps to 14psi imediatly. I tried reversing the vacum delay valve and it sits at 14psi and doesn't move at idle or with a little or alot of throttle.

Seems like it working except I'm not getting any increase in fuel pressure with throttle. I have the vacum line plugged into the far right vacum at the front base of the throttle body.

Any idea what would cause this? faulty vacum delay valve?
This was me throttling it by hand in park, how much of a delay is there?

I'll try it without the vacum delay valve and see if the pressure adust to throttle accordingly.

Connect the vacuum line without the delay valve. Install the spring right??

Its working. 9si at idle, then goes up with more throttle, then slowly goes back down when off the throttle. Although something strange I notice. At startup I get 9psi but if I let it just sit and idle the pressure slowly drops to about 5psi, not sure why that is. Maybe a small leak in my fuel system somewhere?

p.s will this spring from TDS handle a walbro 255? I know it over powers the stock spring, and the 454 spring tends to be to stiff if I remember correct not allowing a lower setting for lo3's.

I used the stock spring w/the Walbro 255 w/no problem what so ever. 10 PSI at idle, 15 at "no vacuum" (WOT)...w/my combo.

Taking the vacuum delay out was the right move. That shouldn't be used there at all.

TOM: i assume this was the 400 cid. what size injectors?

Yep, a SBC 400 Let me know if you want the details.

The injectors were MSD brand and they were listed as 75 pph injectors. I *think* that they may have been the same as the GM 90 pph units, just rated at a lower pressure possibly, but I'm not sure about that.

This was also used w/the stock ECM and chip.

GM are rated at 12 lbs from what i heard. dont think mallory would rate less. GM may be same as mallory. i have 90's now and am comfortable with 12.7/1 A/F. 5000 rpms . @ 12 lbs FP. but the cam is in today 224/230 .05 and now 5800 rpms. so concerned about fuel adequacy. will find out soon as i have WB.

Well, the cam may change things a bunch for you but it'll be fun to play with.

-Tom

This is an absolutley great thread to read........

Anyone got an update???????

Some of you have been running this for a LONG time......

update? cam caused some problems. not enought fuel above 4500 rpms:D 13.7/1. too much fuel at idle:mad: asynch on inj. so upped rpms from 800 to1000 and that helped. but still some asynch. FP is 17.5 lbs. am running OL past 30 days. idle is 13.5/1 and able to add AE in VE tables (i think?) with enrichment in those cells. had little time to tune this season. car on body shop :cool: and then pesty mechanical issues with WB and other things. will up FP 2 lbs at a time and see if i can get results i want (12.7/1 WOT) then DYNO TIME.

Have you tried no async at all (except AE obviously)? I had best results going with just sync fueling when I was using the $61 and high fuel pressure.

run no asynch. please explain. i thought asynch was a default and synch was the norm? asynch was the manner in which the fueling in reduced when the pulses need to be very small in time on? as i stated i am in OL now. i use Tunercat and have not mastered hex? i honestly dont think i am going aysnch any longer as my A/F is 13.5/1 (idle) and i upped idle from 750 commanded to 1000 rpms(manual-stop screw) and 0 steps IAC.

Compensating for a tuning issue by raising the min idle?
Do a search for disabling async, it's been talked about frequently. Only trouble is you'll need to get a hex editor or deal with TunerPro and the $61 xdf file.

Q:Compensating for a tuning issue by raising the min idle?

actually in CL at 750 rpms the idle pulsated. with IAC activity. yet IAC was set to 0 at that rpm. asynch flag came and went on idle. turned the set screw on TB and idle smoothened out. this is CL. trying to disconnect IAC activity at idle. went to OL and seemed to get better 13.5/1 A/F. in CL seems car does not idle and tip in not as good. AE issues as well. it likes enrichment? crutches AE. BLM values are 122 accross the board in this tune CL but as i said running OL past weeks.. i would like to run car with carb and WB just to see the A/F on WB. my buddy(carb guy big time) thinks all the time i spend tuning is nuts. maybe a slightly rich 13.5 vs 14.7 is better for driving arround town. on x way 65-80 mph leaner seems to be OK. the AE seems to blend better. cam wants to run 2500 >. car does not like the slow running in town?

Asynch at idle isn't so bad, it's the transition from synch to asynch back to snych that causes all kinds of problems. As you noticed you were cycling in and out which was causing your idle fluctuations, not your IAC. Diasable asynch at idle and I bet you can lower your idle with no problems. Does tuner cat have Min/Max Asynch values?

a nice thing about TC is they will add if you ask. i will do so.

Quote: Does tuner cat have Min/Max Asynch values?

is that a function of RPM or pulse width?

RPM with a 747, I set mine to zero and my asynch flag quite working and my idle smoothed out.