Turbo 5.3 E85 fuel problems

Reply Subscribe

Thread Tools

Search this Thread

Aug 20, 2013 | 02:21 PM

DavidPHumes

Thread Starter

On The Tree

iTrader: (1)

Joined: Jul 2010

Posts: 197

Likes: 0

From: Duluth, MN

Turbo 5.3 E85 fuel problems

I am having a confusing fueling issue when getting into boost.

Engine/drivetrain/etc.:

Stock bottom end L33, LS6 cam, Patriot Gold dual springs, LS9 gaskets, Pro Comp head studs
TC76
PowerGlide w/ PTC converter
2 bar HPTuners OS
BR7EF plugs gapped to .020"
Conservative timing (15-20*)

Fuel system:

E85
80lb Siemens injectors
-6AN feed and return lines
Fuelab boost referenced FPR (regulator is above the rear axle with semi truck vacuum line running to the front to a distribution block)
Fuelab filter w/ stainless element (screwed in directly before the FPR)
Dual in tank Walbro 255s in parallel
48PSI base pressure
AEM fuel pressure gauge with sensor mounted to regulator

Whenever I get to the point of breaking vacuum and getting into boost, my AEM wideband reads extremely rich (10:1 which is the bottom of what it reads) and fuel pressure drops from 48 to 35PSI for a split second and then it goes back to 48PSI and adds fuel pressure as needed all the way to redline. During this time the car hesitates and generally runs like ****, but then runs fine once fuel pressure increases. Voltage to the fuel pumps is good as are the grounds.

I did set base pressure based off of what the AEM gauge on the regulator was reporting. I'm thinking I should put a mechanical gauge on the Shrader valve on the rails and redo the base pressure setting. Still, I can't see that causing this massive drop but I'm definitely no expert.

I can post up an HPT log of one of these pulls if it would help.

Last edited by DavidPHumes; Aug 20, 2013 at 02:39 PM.

Aug 20, 2013 | 02:33 PM

Grr

TECH Fanatic

iTrader: (2)

Joined: Mar 2005

Posts: 1,363

Likes: 1

From: Fargo ND

Pull the vacuum line off and get rid of it, re tune it with static pressure. Raise it up if you run out of injector. No reason to boost reference with the amount of power you are making and the regulator in the back it only adds complexity and is inconsitant.

Aug 20, 2013 | 03:05 PM

parish8

single digit dreamer

iTrader: (6)

Joined: Mar 2002

Posts: 9,757

Likes: 4

From: omaha ne

Or put the regulator up front.

Aug 20, 2013 | 04:04 PM

DavidPHumes

Thread Starter

On The Tree

iTrader: (1)

Joined: Jul 2010

Posts: 197

Likes: 0

From: Duluth, MN

I know of a certain 370" 88mm car that ran high 8's with the regulator in the back... so I question whether that's the real culprit or not. I'm not saying it isn't I just don't see why it would be inaccurate.

Aug 20, 2013 | 04:18 PM

parish8

single digit dreamer

iTrader: (6)

Joined: Mar 2002

Posts: 9,757

Likes: 4

From: omaha ne

Quote:

Originally Posted by DavidPHumes

it just isn't ideal.

for one the long vacuum line is going to give a delayed signal to the regulator. then once it does react there will be a delay before the extra pressure gets to the rails.

another thing is the pressure at the rail is going to vary depending on how fast the car is accelerating. there is a .43psi loss in pressure for every foot of line going to the front of the car when under 1 G of acceleration. a fast car will pull more than one G off the line.

between the delayed signal and the loss of pressure as much as 10psi from the forward g forces it will make things inconsistent.

are you tuning ve only? your tune might just need some work right in that area, if your dumping a **** ton of fuel it will bog out and might show a loss of fuel pressure just from dumping soo much fuel in the car.