Issue with engine not liking boost

[dysan]

FYI, I run the GT500 pumps, a single 40A BAP wired pre-FPDM, upgraded my fuel lines and filter from the fuel hat to the rails(stock rails still), deleted the check valve on the fuel hat and I run E85. All this with the Bosch 1000cc injectors and I am only seeing 71% duty cycle making somewhere just above 600rwhp so you can make plenty of power without having to do a return style system.

I don't know my power from a dyno but from my track times and weight of the car.

 

[Dubstep Shep]

FYI, I run the GT500 pumps, a single 40A BAP wired pre-FPDM, upgraded my fuel lines and filter from the fuel hat to the rails(stock rails still), deleted the check valve on the fuel hat and I run E85. All this with the Bosch 1000cc injectors and I am only seeing 71% duty cycle making somewhere just above 600rwhp so you can make plenty of power without having to do a return style system.

I don't know my power from a dyno but from my track times and weight of the car.

That's likely what I'll end up with here soon so I can run e85. I've already got the GT500 pumps. I need new injectors anyways, and lines aren't bad. Really the two big ticket items I would need are the injectors and BAP. I may end up just getting bigger drop in pumps for the GT500 hat, but I need to do more research.

Honestly I like return systems better. Because there's really no tuning involved there are a lot fewer variables, which usually works out to a more consistent product. At some point I may be putting a MUCH larger blower on my car, which is probably when I would look at the Aeromotive system.

 

[JoshK]

FYI, I run the GT500 pumps, a single 40A BAP wired pre-FPDM, upgraded my fuel lines and filter from the fuel hat to the rails(stock rails still), deleted the check valve on the fuel hat and I run E85. All this with the Bosch 1000cc injectors and I am only seeing 71% duty cycle making somewhere just above 600rwhp so you can make plenty of power without having to do a return style system.

I don't know my power from a dyno but from my track times and weight of the car.

So it sounds like we have very similar fuel systems since I run ID1000 injectors. Have the BAP full on all the time is not an issue with it wired pre-FPDMs.

 

[TexasBlownV8]

I too have a GT500 dual pump kit and a competition dual bap kit. I have my BAP on all the time though. If have the BAP wired in before the FPDMs you are not going to be sending the full 20volts to the pumps all the time. The FPDMs will still regulate the voltage, the BAP just allows them to go up to 20volts instead of only up to say 13volts. You are not running full volts all the time and overworking the pumps. I have run this setup as high as 21lbs of boost on E85 and it works well. I do have a -8 fuel line from the tank to the fuel rails also though. I am at 86% pump duty cycle with this fuel system at 21lbs and E85

Thanks

I have mine wired pre-fpdms as well. So looks like I may go this route if I need the voltage boost, and leave it on al the time, especially if it supports e85 (assuming the pump parts hold up in the e85).

 

[BruceH]

A stock fuel system is ethanol compatible. GT500 pumps, one 40amp bap, and 1000cc injectors with stock fuel lines and an 8 gauge power feeder resulted in 699rwhp uncorrected on e85 with a 86% duty cycle. Returnless of course.

Bigger injectors and a larger power wire will take you a long ways. Some aftermarket pumps aren't e85 friendly so be careful if your upgrade includes pumps.

The race BAP spits out 20 volts vs. 17 on the street version (according to product details).

Well, using the Hobbs switch and turning the BAP boosted-voltage on only when under boost is not working out very well and appears to be the cause of my problem.

When I blocked off the switch and just ran the GT500 pumps naturally, I could get into boost at levels and hold it where I could not before (2-6 psi under part throttle), with no issues other than running very lean, which is where the BAP would normally bump up the pumps. Fuel pressure was holding steady around 40 psi during this, too.

Looks like I will need to change my fuel setup here a little, and some re-tuning to match it. Might just go ahead and upgrade to an ethanol-capable system, since I've been thinking about it, remove the dual bap and pump.
Oh well, that's how it goes. Learn and move on... make it better, stronger, faster...

Odd that it was working OK for quite some time (about a year) with no apparent issues.
I tend to agree with everyone, though, do away with the Hobbs switch and just run things at a steady voltage, whether stock or increased voltage.

 

[TexasBlownV8]

Thanks, Bruce.
Sheesh..I had a 40A bap that I passed on to another member, too. Ugh.

 

[702GT]

I was always told if you're going to run a BAP, lock it to max and leave it there. The boost reference can make tuning for it hell.

 

[TexasBlownV8]

Just an FYI, after doing some datalogging, there is definitely a fuel delivery issue.
I took the BAP out of the equation for now (left the hobbs switch wired in, but the bap is not boosting voltage, just passing normal voltage through to the fpdm's).

Cruising at normal speeds and light load, the fuel pressure is maintained around 38-40. But when I floor it, fuel pressure drops into the 20's, where she sputters, briefly spikes up to 40, then gradually drops back down to the 20's. Of course she runs very lean by this point.

So at this point, I'm thinking:
- one of the pumps is out or not able to deliver enough fuel
- one or both of the pre-filters in the tank are clogged or dirty
- some kind of fuel flow valve issue in the pump hat

 

[05moneypit]

Just an FYI, after doing some datalogging, there is definitely a fuel delivery issue.
I took the BAP out of the equation for now (left the hobbs switch wired in, but the bap is not boosting voltage, just passing normal voltage through to the fpdm's).

Cruising at normal speeds and light load, the fuel pressure is maintained around 38-40. But when I floor it, fuel pressure drops into the 20's, where she sputters, briefly spikes up to 40, then gradually drops back down to the 20's. Of course she runs very lean by this point.

So at this point, I'm thinking:
- one of the pumps is out or not able to deliver enough fuel
- one or both of the pre-filters in the tank are clogged or dirty
- some kind of fuel flow valve issue in the pump hat

Mike,
Pull the pumps and check the siphon line and the supply line. I know I have seen other threads here on the same issue with the lines splitting or coming off at the pumps. Good luck.

Lee

 

[Fullboogie]

Just in case you think the tube pointing downwards with the orange "beak" on it is a siphon tube, it's not. It's the dump from the line that draws down fuel from the passenger side. The pump(s) draws fuel directly from under the pump. Also, even if the crossover tube (rigid black plastic) comes off, it won't affect pressure. However, I have heard of the "Y" plastic fitting breaking or splitting, which would cause this.

Definitely time to pull the hat and check the lines and filters.

 

[TexasBlownV8]

Thanks guys; I was hoping for some good advice like this before pulling the pump

 

[05moneypit]

Just in case you think the tube pointing downwards with the orange "beak" on it is a siphon tube, it's not. It's the dump from the line that draws down fuel from the passenger side. The pump(s) draws fuel directly from under the pump. Also, even if the crossover tube (rigid black plastic) comes off, it won't affect pressure. However, I have heard of the "Y" plastic fitting breaking or splitting, which would cause this.

Definitely time to pull the hat and check the lines and filters.

Sorry for my ignorance at not correctly putting into words what I was thinking.

Simply stated .........pull the pumps and check the plumbing.

 

[CPRsm]

Awesome. At least you have a place to look

 

[Fullboogie]

And OP - I've got a few spare hat parts laying around that may be of some use. If you find something small that you need, PM me and I'll send it out to you.

 

[TexasBlownV8]

OK so I pulled the pump assembly today. Before doing so, I tested key-on fuel pressure from each pump, unplugging one fpdm, then the other:
- unplugging the passenger side fpdm, fuel pressure only got to 8 psi
- unplugging the drive side fpdm, fuel pressure got to 19 (seems normal, if both pumps are to produce half the pressure each).
This tells me the driver-side pump is not working or not holding pressure.

After pulling the pump, ll connections are intact. I do not see any split lines nor hose separations. Not sure which pump it is in the hat yet, but seems like one of them is not doing well!

(are the pumps themselves the same as stock GT pumps? I have a '07 fuel hat with a good pump, that I can replace the 'bad' one with.)

 

[BruceH]

According to this FRPP info sheet they are. Single and GT500 system are listed as using Gen 6 pump or pumps.

OK so I pulled the pump assembly today. Before doing so, I tested key-on fuel pressure from each pump, unplugging one fpdm, then the other:
- unplugging the passenger side fpdm, fuel pressure only got to 8 psi
- unplugging the drive side fpdm, fuel pressure got to 19 (seems normal, if both pumps are to produce half the pressure each).
This tells me the driver-side pump is not working or not holding pressure.

After pulling the pump, ll connections are intact. I do not see any split lines nor hose separations. Not sure which pump it is in the hat yet, but seems like one of them is not doing well!

(are the pumps themselves the same as stock GT pumps? I have a '07 fuel hat with a good pump, that I can replace the 'bad' one with.)

 

[TexasBlownV8]

gt500 pump: 6C34-9350-AA
gt pump: 6C24-9350-AA

The outlet tubes are NOT the same: the GT one has a hoes-end flare, and is smaller diameter, while the gt500 outlet is larger and smooth.

So now that I have a gt pump with the hose-end removed, and can't use that pump, looks like I need another compatible-fitting gt500 pump; I want to be able to replace the pump and secure the tubing end over the outlets, and let'r rip, with no hose changes, if possible.

This would be a good time to upgrade the internal pump units, one or both.