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Sorry in advance because this is kind of a double post. I posted something else over in fueling and injection but when it comes to tech questions they just seem to get more attention and the right people for turbo stuff replying here.
But a while ago, as in maybe a month ago, I finally got a pressure gauge on the fuel system I could log and I found that I was losing fuel pressure much sooner than I was hoping for. I had a single 400lph walbro feeding a 6-an line with a 5/16" return to the stock fuel rails through an high flow aeromotive FPR. So I stuck another 400lph in the tank and that kind of helped. It did provide a few more psi of FP further into the boost but still trailed off after 14psi of boost.
So with two walbro 400lph pumps Y'd together in the tank and feeding a single 6-AN feed line to the regulator, what's causing me to never see over ~63psi of FP? When I first logged the FP and saw the drop I had a base FP of 44psi and it was capping out at about 52psi by the end of the RPM range with it spiking around 4k RPM at 63psi. So, I changed the base FP to 58psi to see what difference it would make. I re-tuned the VE table but same thing still. Now it just starts off at 58psi, climbs to 63psi then trails off back to 52 by 6400rpm.
The regulator is referenced...But it gets no where close to 1:1 referencing changes. The reference line isn't leaking, the vac/boost source is also hooked to an in dash gauge to I know its getting proper pressures. I have enough pump to power more than I have.
Did I mess something up in the setup? Have a maxed the factory LM7 rails out or something?
The FPR is about 4" away from the inlet of the factory rails and mounted on the engine 6" forward of the firewall. Truck engine bay. So the feed and return come up from the tank and it deadheads from there. The pressure sensor is on the FPR itself.
If the regulator is before the rails, and you're measuring pressure at the regulator, then the rails being any amount of restriction would have zero effect on your fuel pressure.
You are no where near the point where factory rails become a restriction. Going by weight and trap Ive been around 900whp on e85 using a dead head factory rails as you have them plumbed. Though I use half inch line.
Could be a few things. Most likely voltage drop. Can you datalog? Fuel pumps are very sensitive to voltage and wiring. Tap the power wire going to the pumps with a volt meter and make a pull, watch voltage. Many, including myself have issues with alternators continuing to charge past even 5800 rpm. Some less that that. Some have no issues at all. But I'd check voltage first. Ensure you have the pumps wired with a large enough diameter wire for the length of wire run and the AMP draw of those pumps.
Your pump setup should be good for all the power you can make on those injectors, even at higher base pressures. But to make a pump go farther, you drop base pressure. You don't raise it. Set it back 42psi adn figure out your issue. A lot of the "Y" setups are junk IMO. you don't take 2 3/8 lines and Y then into another 3/8 line. It's just a bad idea. You need to step up the diameter of the "y" exit. Ideally you'd run a -6 from each pump to the regulator, then a 1/2" or larger from the regulator to the rail.
You are no where near the point where factory rails become a restriction. Going by weight and trap Ive been around 900whp on e85 using a dead head factory rails as you have them plumbed. Though I use half inch line.
Could be a few things. Most likely voltage drop. Can you datalog? Fuel pumps are very sensitive to voltage and wiring. Tap the power wire going to the pumps with a volt meter and make a pull, watch voltage. Many, including myself have issues with alternators continuing to charge past even 5800 rpm. Some less that that. Some have no issues at all. But I'd check voltage first. Ensure you have the pumps wired with a large enough diameter wire for the length of wire run and the AMP draw of those pumps.
Your pump setup should be good for all the power you can make on those injectors, even at higher base pressures. But to make a pump go farther, you drop base pressure. You don't raise it. Set it back 42psi adn figure out your issue. A lot of the "Y" setups are junk IMO. you don't take 2 3/8 lines and Y then into another 3/8 line. It's just a bad idea. You need to step up the diameter of the "y" exit. Ideally you'd run a -6 from each pump to the regulator, then a 1/2" or larger from the regulator to the rail.
Ya, that is this winters project. It wasn't feasible to run 8-an lines because I was stuck with the factory sending unit until I move the fuel tank and replace it with a better tank or I cut this one and stick a larger sending unit in it.
I went up in pressure to see if it had an effect on the final pressure and it didnt. But there is a plus side to the increase in base pressure, the VE table smoothed out a TON. It had spikes in it that I couldn't get rid of without pissing off the wideband. With the higher base pressure now though the VE table is much smoother and it seems to run better down low at neighborhood speeds.
My largest concern is figuring out why I'm not getting proper reference near 1:1. I figured with this much pump I'm not in danger of running out of fuel even at 78psi of fuel pressure. The way it sits now I'm hitting about 98% injector duty cycle at 52 psi at 6000-6400rpm.
The alternator is my next move I think, probably a new battery too since this one is getting weak, has swelled somehow even though it's never been frozen but since it still went to 12v NAPA wouldn't warranty it. I need to just find a way to ruin it and take it back. They didn't remove the date stickers on it for the warranty....so free lifetime warranty lol.
It's voltage drop, not sure on the reference yet but the voltage went from 12.7 at low rpm to 12.4 at about 4500 and at 5300rpm on the nose it drops to 11.4v
So, what is the best way to go about fixing this. Replace the Alt and battery? Get a voltage regulator/booster for the fuel pump? A new non-re manufactured alt is about $200-$400, new battery is about $200-300 for a good AGM cell. The new alt may or may not fix the issue, I might have to under drive it and that involves more than I'd like to do. Voltage regulator is $400 for a good one. Would a booster/regulator be able to provide the voltage needed off the 12v of only battery when the alt stops working at 5300-5600rpm? If so I would think that would be the safest route of stabilizing it since it would work with no alt charge and with?
So, what is the best way to go about fixing this. Replace the Alt and battery? Get a voltage regulator/booster for the fuel pump? A new non-re manufactured alt is about $200-$400, new battery is about $200-300 for a good AGM cell. The new alt may or may not fix the issue, I might have to under drive it and that involves more than I'd like to do. Voltage regulator is $400 for a good one. Would a booster/regulator be able to provide the voltage needed off the 12v of only battery when the alt stops working at 5300-5600rpm? If so I would think that would be the safest route of stabilizing it since it would work with no alt charge and with?
There is a pulley available for the alternator that will let you under drive the alt and might fix most of your issues.
Is voltage measurements above at battery, alternator output or fuel pump? What alternator do you currently have? If alternator output is not at least 13.5V at 1500rpm it's no good and needs replaced. What alternator are you looking at as replacement?
If battery starts car, it should be sufficient. Surely not causing your problem. I wouldn't worry about battery yet.
I checked it again today with someone reving it up for me to different RPMs. 13.8v at idle and up to about 14.5v at 3k RPM so it would appear to be working still. Looks like an under drive pulley is probably in order then.
Do you basically always have to change out the crank pulley to under drive any accessory? Because as it stands now my belt is so tight that I can barely get it on and the tension pulley doesn't spring back at all its 100% at the end of it's travel by the time the belt fits.
I'm battling the same thing. The voltage booster with and 11v source is really a bandaide. it's also not good for it to only get an 11v input. You need to address the alternator IMO. Really seems hit/miss. Stay away from parts store remans, they are all crap. Many people have luck with some of the Ebay 160a+ alternators. I've run 3 now and all ofg them dropped voltage around 6k. I have now went with a power master unit (about $200 on sale at summit now) and it STILL drops voltage. I then installed a 3.10" alt pulley and it STILL Drops voltage. I have ordered a manual belt tensioner as the power master guys feel like belt slip is the issue. I have great belt wrap and large pulleys so I kinda doubt it. But I hope they are right!
With all the trouble and headache associated with the 4+ alternators, pulleys etc... (same issue on 2 cars) I'd have been time ahead just dropping the big bucks on a mechman alternator. They claim to be fine up past 8k rpm with factory pulleys. So really it just depends how lucky you feel and what your budget/time are like. AS long as your wring is up to snuff, I'd just buy the big bad mechman and be done personally. I'm tired of messing with it!
Look up 6 groove 17mm pulley on ebay. They have a 3.10" which is really a 2.95" if you go by the portion the belt rides on. It's the best deal I've found by far at around $20. Also I brough tmy old belt in and asked for a 1" larger belt. It fit perfectly with the larger pulley VS stock. I run the factory crank pulley (7.5")
It $400 for the mechman LS truck engine conversion alt but I think that's what I'm going to do. Because you're right, it's almost $300 just to guess at any other fix.
It $400 for the mechman LS truck engine conversion alt but I think that's what I'm going to do. Because you're right, it's almost $300 just to guess at any other fix.
A larger alt pulley is like $30 and would seem worth a shot to see if it helps before spending $400. To be fair if your belt is already that tight you'll need a new one. So add $20.
exactly. I hate when people jump to the most expensive fixes first, but I can appreciate that some people just want the issue gone regardless the price.
East Coast is a common go to for alt on high rpm track cars. Appears they don't do LS style alts though https://ecae.com/product-category/alternators/ . They typically setup with a 2 to 1 ratio on drive to alt pulley size. Max alt rpm to be on the safer side, 16000. Interesting that the f body CS130D is typically more stable than the truck AD230 or AD244.
07-13-2020, 11:12 PM
When are factory fuel rails maxxed out? 
