Thanks, I have a pressure transducer at the pump so I'll see if this is accurate.
BUILD THREAD 86 GP 2+2~Blown 6.0
- Thread starter 81cutlass
- Start date
I'd love to validate the math. I'd comfortably say it could be off ±25% based on the range of friction in the equation.
I am going to put my mechanical gauge at the tank and turn the pump on manually and see how it compares to -6 and -8 with my 450. I'd love to see the results on yours.
Absolutely, I understand the effective flow rate thing when you put boost on the discharge side of the injector.
I put e85 in the car for the first time in '18 and I've just added duty cycle previous to this when I want more fuel. It's typically worked fine. Last fall I tried adding fuel (via duty cycle) when I was dialing in my tune at the track and I was putting extra duty cycle in and wasn't getting any more fuel. At the time the fueling was mostly OK so I didn't stress over it and I am glad I looked into it now.
Exactly why I'm putting a sensor in. Get some hard data and get rid of the misinformation.
So I spent all Saturday fixing my wife's fusion trans leak and doing house stuff so I didn't get my data collection done until today.
I got my -8 line in the mail late Saturday afternoon and got started on checking my pressure with the -6 line. Want to check how much pressure drop reduction I get with -6 before I swap.
At 48psi rail I had 5psi of back pressure at the regulator. That's stock 3/8 feed line feeding back to the tank. I was a little concerned that might have been a restriction but it looks minimal. At 68 psi rail I had like 3psi back pressure.
I checked loss from the pump to the trail with my -6 feed and it only has 3psi loss at 68 rail and 4psi loss at 48 rail. My math said it should be north of 50psi. WAY off. There is some flexibility with variables in the equation but not a factor of 10 off.
I checked my voltage at the pump and it was like 10.9. 11.9 at the battery. I hooked up the charger and yeah still 12.5 when it's 13.5 at the battery. For sure not getting the voltage at the pump I want.
Dad has a stack of 8 or 10 gage wiring that he harvested out of some air seeder wiring harnesses that were getting scraped at work so I'm going to replace the 12 gage and see if my voltage drop is lower. 12 gage wire is only rated for 12ish amps and this pump pulls 22 when its really working so I think that's part of my issue.
I am going to try jumping 13.5v to the pump and see if I can get more pressure drop once that variable is a little less of a factor.
I'd like to fully understand why my math and actual drop is so far off. I think I have some flow meters at my lab I might borrow and see if my pump is really flowing what it should. Something seems off.
How I'm checking the pressure. Right after the pump and before the filter or feed line.
Oh and I made it to cruise night last week and the photo dude is back. If nothing else I really am happy with the ride height im at now. It's comfortable and confidence inspiring and looks good.
I got my -8 line in the mail late Saturday afternoon and got started on checking my pressure with the -6 line. Want to check how much pressure drop reduction I get with -6 before I swap.
At 48psi rail I had 5psi of back pressure at the regulator. That's stock 3/8 feed line feeding back to the tank. I was a little concerned that might have been a restriction but it looks minimal. At 68 psi rail I had like 3psi back pressure.
I checked loss from the pump to the trail with my -6 feed and it only has 3psi loss at 68 rail and 4psi loss at 48 rail. My math said it should be north of 50psi. WAY off. There is some flexibility with variables in the equation but not a factor of 10 off.
I checked my voltage at the pump and it was like 10.9. 11.9 at the battery. I hooked up the charger and yeah still 12.5 when it's 13.5 at the battery. For sure not getting the voltage at the pump I want.
Dad has a stack of 8 or 10 gage wiring that he harvested out of some air seeder wiring harnesses that were getting scraped at work so I'm going to replace the 12 gage and see if my voltage drop is lower. 12 gage wire is only rated for 12ish amps and this pump pulls 22 when its really working so I think that's part of my issue.
I am going to try jumping 13.5v to the pump and see if I can get more pressure drop once that variable is a little less of a factor.
I'd like to fully understand why my math and actual drop is so far off. I think I have some flow meters at my lab I might borrow and see if my pump is really flowing what it should. Something seems off.
How I'm checking the pressure. Right after the pump and before the filter or feed line.
Oh and I made it to cruise night last week and the photo dude is back. If nothing else I really am happy with the ride height im at now. It's comfortable and confidence inspiring and looks good.
Ok so more mind numbing data.
My notes probably dont make a ton of sense but I retested the pump with a charged battery and got a little more pressure drop. Still only about 5-6psi so I gotta redo the math and see if I can get it to agree. It's way less than I thought! However the flow is less than I thought so I can imagine the numbers will converge.
With 12.3V at the battery for all tests
12gage wire
I have 11.9V at the relay fuse block under the hood
And 11.5v at the pump under load
I pulled a set of jumper cables from the battery to the trunk and then 1ft jumpers of 10 gage wire to the pump harness
I had 11.9V at the pump under load
So 12 gage wire is around a half a volt of drop. I'm going to simplify the wiring some, pull power right off the alternator instead of what I'm doing now, which is essentially using the starter as a junction and sending all power to the starter lug and then back to the fuse block. And replace it with 10 gage.
I then did the obvious easy decision of just checking flow in the pump by draining the return into a jug and measuring the time to get a gallon. I got 66.5 GPH which at 12V and 64psi pump it should be 80 GPH according to the walbro chart. I did have 11.5V but that's a decent reduction past what I expected. That's probably 58 GPH at 75psi rail under boost.
Granted the alternator probably makes more base voltage than 12.3 like my little 6amp charger does so I might have a bit more voltage at the pump but not enough to get me where I need to go.
I need 110GPH realistically to max my injectors out. 2 pumps gets me right there.
I am surprised how small my 450 walbro is really acting. I didn't expect it. A 450 seems so big on paper but by the time you add voltage drop, run it at higher pressure under boost, and line restrictions it quickly turns into a pump that's only 210 LPH.
So I gotta throw another pump in there. It's actually not overkill, it's what the system requires!!
My notes probably dont make a ton of sense but I retested the pump with a charged battery and got a little more pressure drop. Still only about 5-6psi so I gotta redo the math and see if I can get it to agree. It's way less than I thought! However the flow is less than I thought so I can imagine the numbers will converge.
With 12.3V at the battery for all tests
12gage wire
I have 11.9V at the relay fuse block under the hood
And 11.5v at the pump under load
I pulled a set of jumper cables from the battery to the trunk and then 1ft jumpers of 10 gage wire to the pump harness
I had 11.9V at the pump under load
So 12 gage wire is around a half a volt of drop. I'm going to simplify the wiring some, pull power right off the alternator instead of what I'm doing now, which is essentially using the starter as a junction and sending all power to the starter lug and then back to the fuse block. And replace it with 10 gage.
I then did the obvious easy decision of just checking flow in the pump by draining the return into a jug and measuring the time to get a gallon. I got 66.5 GPH which at 12V and 64psi pump it should be 80 GPH according to the walbro chart. I did have 11.5V but that's a decent reduction past what I expected. That's probably 58 GPH at 75psi rail under boost.
Granted the alternator probably makes more base voltage than 12.3 like my little 6amp charger does so I might have a bit more voltage at the pump but not enough to get me where I need to go.
I need 110GPH realistically to max my injectors out. 2 pumps gets me right there.
I am surprised how small my 450 walbro is really acting. I didn't expect it. A 450 seems so big on paper but by the time you add voltage drop, run it at higher pressure under boost, and line restrictions it quickly turns into a pump that's only 210 LPH.
So I gotta throw another pump in there. It's actually not overkill, it's what the system requires!!
Front mount battery?
If I was spec'ing that out with 1 450 I would have 8ga to a block in the trunk, 2 450s I would have 4ga.
0ga alt to battery and 0ga to starter.
But I hate electrical gremlins.
I have a dedicated fat wire running off the alternator to a busbar at the back for just this reason.
My alternator directly feeds my supplemental fuse block, pump(s), injectors, coils, and the EPS.
Also, Mike was right.
Front mount battery yup.
I confirmed and the wire Dad has is 8 gauge so I am going to for sure (at least) use the 8 since it's free and a lot better than the 12 I have. I see 8 is rated to 35 amps which on 2 pumps is borderline considering each is rated to draw 15 amps at the flow I am running. I agree 6 would be ideal and 4 is ideally overkill
Oh and I redid your pressure drop equation with 1200lb/hr, #8 line, 12 ft and with the corrected friction I found on my setup and you are at 9.4 PSI.
I like the idea of the busbar, short of electric fans I have never dealt with this high of amp draw systems so it's a bit of a mental redo. I half melted my electric fan wiring last fall on drag weekend (due to woefully underdesigned circuitry) so I am trying to be a bit more prepared on this one
I'd say you were right but we can't let your ego get too big haha.
Also, I was able to get my math to match reality.
With my single 450 I saw 6psi pressure drop on #6 and when I adjust the unknowns to match my coefficient of friction is 0.006, which is between the 0.0025 and 0.025 limits on the chart. I was using the upper end previously. 0.0025 is drawn steel or glass tubing and 0.025 was cast iron pipe.
A single 450 on #8 line should have 1.35 PSI pressure drop
A dual 450 with the flow rate that matches what I am seeing should have 6.5 psi of drop on #8 line and 28 psi drop on #6 line, each with 14 ft of line.
So the plan!
#1 swap feed line out to #8
#2 replace 12 gauge pump wiring with 8 or better
#3 turn base pressure down to 43 just to see how it reacts
#4 burn the tank of e85 I have in
#5 drop tank and put a second 450 in
I was opposed to 2 pumps initially but I at least understand why I need them now.
