Fuel Pressure Drops at 7k (VF650)

[lonatic]

Good Evening,

In the process of getting my e90 tuned by RK, he (Jordan) asked me to perform some data logs.

All was good until he asked me to do a redline pull, and datalog.

Well what we found was that:
@72xx RPM fuel pressure starts declining hard.. attaching datalog.

I understand that the fuel filter is built in to the pump. With that being the case is it best to replace the pump? If so are there any upgrades out? (I haven't found any).

My plan was to run e85, I have fuel it hellcat secondary pump ready to go but want to make sure lpfp is running properly before I move on to e85.

Thanks

[amrazM]

What’s the injector duty cycle hitting?

[lonatic]

Originally Posted by amrazM

What’s the injector duty cycle hitting?

TBH this is one area im not really too familiar with, how can I check?

[nycplumber]

This seems like something your tuner would or should know. Jordan didn't offer any help?

[Davisca455]

Originally Posted by amrazM

What’s the injector duty cycle hitting?

^
This seems like really good info to check into.

When I read the original post, my assumption was the data logger was reading the fuel pressure sensor output?
Given my recent "loss" of fuel pressure experience I'd be curious to know if the sensor feedback is good.

I was at Thunderhill East last year and got a code for low fuel pressure when I was redlining 4th and 5th gear going down the front straight, and the first thing I thought of was "fuel pump, maybe clogged fuel filter?".
Turned out zis sensor es kaput.

[lonatic]

Originally Posted by nycplumber

This seems like something your tuner would or should know. Jordan didn't offer any help?

He hasn't responded yet, I don't think he wouldn't help. I was just trying to get ahead.

[Green-Eggs]

This is an age old problem since Bert @ BEBearings discovered it back in 2011. Simply said, your fuel pump can't provide enough supply. You need to upgrade your fuel system.

[lonatic]

Originally Posted by Green-Eggs

This is an age old problem since Bert @ BEBearings discovered it back in 2011. Simply said, your fuel pump can't provide enough supply. You need to upgrade your fuel system.

I do have a hellcat secondary pump with 4psi hobbs switch (not installed). My understanding was that the factory fuel pump was enough for 93 octane? I was primarily planning on running the secondary pump for e85 and was going to have it off unless I was running E85.

[nycplumber]

What pulley/boost you running?

[lonatic]

Originally Posted by nycplumber

What pulley/boost you running?

VF650 - 3.48"

From the guage i've seen 8.1

[lonatic]

update: Jordans recommendation was to install the secondary pump with 4psi switch.. so i'll be doing that as soon as I get a chance.

[Green-Eggs]

Originally Posted by lonatic

I do have a hellcat secondary pump with 4psi hobbs switch (not installed). My understanding was that the factory fuel pump was enough for 93 octane? I was primarily planning on running the secondary pump for e85 and was going to have it off unless I was running E85.

The factory fuel pump will fail to provide enough fuel for anything around 600 rwhp or greater.

[lonatic]

Originally Posted by Green-Eggs

The factory fuel pump will fail to provide enough fuel for anything around 600 rwhp or greater.

Yeah I guess I was wrong.

[Adriano917]

Did you buy the kit new or used ? 3.48” equals to 88mm, 94mm is the 650 kit. Have you flow tested the Injectors ? I run the 94mm Pulley with 3 gallons of E85 and 7 of 91oct and have no issues, I also sometimes run a full tank of Gas and Boostane to equal to around 97oct/98oct and no issues whatsoever. I’m guessing the pulley you are running is maybe a 10 psi Pulley.

[lonatic]

Originally Posted by Adriano917

Did you buy the kit new or used ? 3.48" equals to 88mm, 94mm is the 650 kit. Have you flow tested the Injectors ? I run the 94mm Pulley with 3 gallons of E85 and 7 of 91oct and have no issues, I also sometimes run a full tank of Gas and Boostane to equal to around 97oct/98oct and no issues whatsoever. I'm guessing the pulley you are running is maybe a 10 psi Pulley.

Form Vf:
VF650 - 3.48"
VF620 - 3.6"
VF595 - 3.8"

What you have is 3.7 I'm not sure where that falls.
Have you performed data logging to see what your fuel looks like? Also injectors we're brand new. I believe 10 psi is 3.3 pulley.

[amrazM]

with big injectors when your injector duty cycle gets high the fuel pressure drops off dramatically its normal to see. you need to run the secondary pump which helps you maintain the 70-75psi in boost.

I would not be driving the car over 5000rpm without the secondary pump installed, im not sure why jordan even has you logging the car without a second pump. multiple people have had their engine let go from doing this .

[lonatic]

Originally Posted by amrazM

with big injectors when your injector duty cycle gets high the fuel pressure drops off dramatically its normal to see. you need to run the secondary pump which helps you maintain the 70-75psi in boost.

I would not be driving the car over 5000rpm without the secondary pump installed, im not sure why jordan even has you logging the car without a second pump. multiple people have had their engine let go from doing this .

In his defense I'm not sure he knew, I had advised him I had it but hadn't installed it yet. Maybe he just missed it. Thank god all good here. I'll get around to installing it soon maybe a diy too who knows.

We did datalog till 5k and all checked out. It was at 7200 where the fuel pressure dropped

[BPMSport]

The real question is, what is the air fuel ratio? What injectors are being used? Take another log with lambda values and voltage. These are very imperative parts of understanding what may be happening, and if your tuner isn't looking at this - there is a larger issue here.

There is no question that with full E85 use that the factory pump will not be sufficient. It is sufficient however, for a fair amount before exceeding pump limits.

[lonatic]

Originally Posted by amrazM

with big injectors when your injector duty cycle gets high the fuel pressure drops off dramatically its normal to see. you need to run the secondary pump which helps you maintain the 70-75psi in boost.

I would not be driving the car over 5000rpm without the secondary pump installed, im not sure why jordan even has you logging the car without a second pump. multiple people have had their engine let go from doing this .

That makes sense, put secondary pump in running 70-80psi in boost now, AFR 11-12. Working out final kinks and then switching over to e85.