The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

  • Join the Community!

    DSMtuners is a massive archive of DSM information - but more importantly, it's a COMMUNITY! Join in and participate with other DSMers, and invite all of your DSM friends to make this place their home. Chat with others, create a build thread, post questions and answers. Get involved! Logging in will also remove many of the advertisements, along with this notice. ;) It will also allow you to view images in threads.

Please Support STM Tuned
Please Support STM Tuned

Big Pump, Small Fuel Line Tune issue resolution "Bandaid" TEST

This is a diagram for a workaround for cars with Big Pumps and Small Lines (stock) issues. It IS an issue and I didn't realize it until my tuner brought it up in my tune. We have worked around it but I am going to try this and just see what happens.
If you have any experience with this issue, I would like to hear your input and, of course, if something looks like "That's not gonna work", please give me your opinion.
This isn't really meant to take the place of proper line size but, in "theory", this is a "Bandaid" fix that I think will make a difference. I will be re-plumbing the car today and will report on any issues that arise.
To me, the injectors won't care that there is a much larger VOLUME of pressurized fuel for use under heavy load situations. I am just pressurizing fuel at the rail and its "reserve supply" and going to see if the pump can keep the pressure up at the injectors without any side effects.
I am running the Hellcat 525 pump/2150 injectors and have stock fuel and return lines for reference.
I'd like to thank @VelocitàPaola for the easy to use/modify diagrams!
Thanks!
Marty

You must be logged in to view this image or video.
 

1990TSIAWDTALON

Moderator
7,952
3,883
Nov 14, 2013
Independence, Kansas
I did my Bandaid tonight when I swapped in a spare set of injectors while I am chasing a full lean issue not related to the Big Pump Small Lines problem.
I can report that so far, the car sees no difference but I can't boost right now due to other problems, but "Stay Tuned" and thanks!
Here are pictures of the "6' Fuel Volume Mod".
Like I said, the car, under normal driving, seems like I did nothing, but we will see soon how she reacts under load. :thumb:
In the pictures, I am feeding both sides of the rail, with an extra 6' of line going to the other side in case you are wondering what I am doing and what you are looking at.
Time will tell. It may not make a dam bit of difference but I am testing it!
It is not a replacement for just running bigger line to the pump and forgetting about it, its just a test.
Marty
Pics

You must be logged in to view this image or video.


You must be logged in to view this image or video.
 

bastarddsm

Proven Member
5,346
1,153
Aug 26, 2003
Mendota, Illinois
from my testing a stock hose from filter to rail is the only real restriction. My car literally makes 800hp on a factory stock fwd n/t fuel line from tank to filter, wix stock replacement filters, a double banjo bolt and 2 stock hoses from filter to rail. I do drill the filter inlet so it is same as OD of the line, but you don't have that issue.


I've flow tested the stock stuff, and there is a post on here with the data. I doubt you are seeing a restriction in the lines. You just made a poor pump choice. Them big ass pump have terrible high pressure delivery. 40psi boost, 43psi fuel pressure, and then add 10psi dp for the lines/filter. 1psi less dp from bigger lines ain't gonna do shit, even go hog wild and get huge lines so there is like 0 drop (never happen) and it's still a marginal improvement in delivery. Ditch that 525 and get 044 or something and a BAP. Or a screw pump.
 

jed344

Supporting VIP
1,074
207
Jan 10, 2008
Waterville, Iowa
I haven't noticed a issue with my 525 pump. I do also have a bulkhead fitting -6 feed. Granted with a 10:1 motor and 62mm turbo it does not take a ton of boost to make some jam, for a more serious set up the car we are finishing up went with sump on stock tank, -8 lines and magnafuel 750. I have no idea what the limit of this combination will be so will be interesting to see.
 

1990TSIAWDTALON

Moderator
7,952
3,883
Nov 14, 2013
Independence, Kansas
My pump is working fine but when Kevin and I started messing with the tune, he had already been through this and I thought, what the hell, I have extra line and fittings, lets just see if it makes any difference at all. I will still update if I notice any good, bad or different results. It is easy to take back apart. I bet a lot of people are saying "why didn't you just use that line to go to the tank", and I will at some point. I just wanted to play around and see what happened, and really, nothing to talk about so far.
 

Mech Addict

Supporting Member
620
225
Jun 9, 2019
Jackson, Wyoming
Since you haven’t really reported on how this has worked out, I’ll go out on a limb from my background in engineering and make a prediction/ evaluation.
The most obvious part that should have no effect is the 6’ coil of tubing. Fuel is incompressible, so that volume can’t change in response to pressure drop, and therefore is really only acting as more pipe friction.
You are feeding the rail from two directions instead of one, so that could have a benefit, but likely a negligible one.
It is possible that a stock fuel rail or the short connection from filter to rail are limiting flow (reducing delivery pressure) to the farthest injector under high demand, so some benefit could be gained by the additional path and shorter rail length, though I presume you have upgraded the rail with the injectors.
Overall, I’m predicting this is not going to do anything near upsizing the line from the tank.
 

1990TSIAWDTALON

Moderator
7,952
3,883
Nov 14, 2013
Independence, Kansas
So far, you are SPOT ON. I was just playin around anyway. I found plenty of line in a carboard box that would fix the issue, so now it is just getting to the bulkhead fitting and running line. The lift makes that stuff easy, but I have some other issues/gremlins to iron out before I get to that. Thanks for all the input from you all.
 

Mech Addict

Supporting Member
620
225
Jun 9, 2019
Jackson, Wyoming
I don't want to have given the impression of dumping on your experiment: that is primary science. Often discoveries and great ideas come from having one thing fail, but noticing something else along the way. Sometimes long-held beliefs are upended when someone bothers to TRY something. Plus this is a hobby, after all, and I like wrenching on lines and fittings and all manner of stuff too, so Kudos for trying.
 

1990TSIAWDTALON

Moderator
7,952
3,883
Nov 14, 2013
Independence, Kansas
Heck, I wasn't worried, I wanted feedback. Good bad or ugly. I am going to put AN line on the car at some point anyway. Just "Playing" to see what happens. :thumb:
 

jed344

Supporting VIP
1,074
207
Jan 10, 2008
Waterville, Iowa
I have tried to find flow data on the magnafuel 750. I haven't found any concrete data yet but it appears at 80+psi of fuel pressure the flow is decent amount more then 525 pump. I tuned a 1g that ran into same issue as you with same stuff on a 35R but he was still on all stock fuel lines and stock filter. I assumed stock filter was biggest issue.
 

Mech Addict

Supporting Member
620
225
Jun 9, 2019
Jackson, Wyoming
Bigger pump will draw more amps to make more pressure at the pump to overcome high pipe friction for a given flow rate. Higher pressure delivered at the injector will add more fuel to the engine, though my vague understanding is that injectors are designed for a certain fuel pressure to work right. Larger diameter line from tank to filter will pass more fuel at whatever pressure it already makes. Centrifugal pumps have a curve relationship of pressure vs. flow. So a bigger pump is one answer, though the power consumption could require bigger fuse and wire.
 

NOSLO2PT0

Proven Member
2,473
120
Aug 31, 2002
Joliet, Illinois
I have tried to find flow data on the magnafuel 750. I haven't found any concrete data yet but it appears at 80+psi of fuel pressure the flow is decent amount more then 525 pump. I tuned a 1g that ran into same issue as you with same stuff on a 35R but he was still on all stock fuel lines and stock filter. I assumed stock filter was biggest issue.
I believe the banjo bolt from the stock feed line coming off the OEM style fuel filter is the biggest restriction
 

1990TSIAWDTALON

Moderator
7,952
3,883
Nov 14, 2013
Independence, Kansas
Lots of good info in these conversations that have come up! Thank you all for the interesting views. In the end (probably after this weekend), I will put a bulkhead fitting on and just run 6an all the way. I was going to run 8, but all of my "stuff" is 6.
I plan to leave the loop, although just a feed to both ends, after I run all AN line.
It will just act like a larger volume rail.
 

Vegas Smith

Proven Member
4,528
2,328
Dec 2, 2002
Houston, Texas
I think everyone is misunderstanding what lean condition is occurring. Correct me if I'm wrong Marty, but this lean condition occurs around 3-4k and is not the same as the common restriction or small pump issues up-top where the engine can't get enough fuel. This is a lean "VE wave" where the car wants nonsensical extra fuel down low. I also had this issue on the 525 + 1650/2150 injectors with 6an feed. I upgraded to the 10an feed and that seemed to fix the problem. Kevin Jewer hypothesizes that it's some type of fuel volume/resonance issue with our pumps/injectors. It's beyond my understanding, but upgrading the fuel feed beyond 6an seems to work for those who have this issue.
 

1990TSIAWDTALON

Moderator
7,952
3,883
Nov 14, 2013
Independence, Kansas
Yes Nick, that was the particular issue that Kevin and I were having when he was setting me up. It was his idea about the dead end length of hose to try but not tying it into both sides. I decided to do that.
For those interested, I do have boost back in an entirely different issue that was going on. So I'M BACK and smiling again :thumb:
 

jed344

Supporting VIP
1,074
207
Jan 10, 2008
Waterville, Iowa
Yes Nick, that was the particular issue that Kevin and I were having when he was setting me up. It was his idea about the dead end length of hose to try but not tying it into both sides. I decided to do that.
For those interested, I do have boost back in an entirely different issue that was going on. So I'M BACK and smiling again :thumb:
I think i read a article from radium last year on this very issue. I haven’t seen it recently but all the cars I have tuned lately have been 62mm+ cars that are not even coming awake till after 4k so it seems to negate part of the issue. But I have seen this before. I thought it had to do with pulse waves and a fuel dampener or something inline on feed helped to remedy it.
 

1990TSIAWDTALON

Moderator
7,952
3,883
Nov 14, 2013
Independence, Kansas
Well that is some new and interesting news, thanks @jed344 !!!
Good to add to the thread.
My car doesn't wake up til 4k also but boy when she does......Big Smiles.
 

Vegas Smith

Proven Member
4,528
2,328
Dec 2, 2002
Houston, Texas
I think i read a article from radium last year on this very issue. I haven’t seen it recently but all the cars I have tuned lately have been 62mm+ cars that are not even coming awake till after 4k so it seems to negate part of the issue. But I have seen this before. I thought it had to do with pulse waves and a fuel dampener or something inline on feed helped to remedy it.
I tried the Radium fuel pulse dampener and it helped a little but didn't fully alleviate the problem.
 
Last edited:

1990TSIAWDTALON

Moderator
7,952
3,883
Nov 14, 2013
Independence, Kansas
Thanks for that comment Nick. I will end up going with AN line all the way. My bulkhead fitting came in today, but I don't have the $ for the line until I get paid.
 

Kryndon

Proven Member
674
357
Jan 10, 2014
Bulgaria, Europe
a double banjo bolt and 2 stock hoses from filter to rail. I do drill the filter inlet so it is same as OD of the line, but you don't have that issue.

Can you elaborate on this further, please? What do you mean by double banjo bolt and 2 stock hoses from filter to rail? The rail has only one inlet. Also which part do you drill out exactly.

From personal experience, I noticed that a DSM wont even get good cold starts if the banjo bolt on top of the filter isn't lined up properly with the hose direction.
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com Raven Fabrication RixRacing RockAuto RTM Racing STM Tuned VR Speed Factory

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Top