Procharger Rolloff Hesitation and Fuel PSI
 

Howdy:

A while ago I posted about installing a Procharger on a 502, got 'er done, boy does it run cool. Pert snappy too.

Yet I am having some setup difficulties involving the pressure while running. And, I have seen a symptom I might call a rolloff hesitation.

Description: running at mild boost and perhaps 2/3-3/4 throttle, when the throttle is pulled back a little the motor seems to drop off power a lot, for a moment or two, and then it gathers itself up.

It's enough for anyone to wonder what just happened, did the spark cut out or injectors pause or what.

Build specs: stock 502 lower, ovalport aluminum heads, mild hydraulic roller cam, roller rockers, IMCO exhaust and diverters.

Fuel system has been modded with a high flow pump, staged regulators (one Essex and one BEGI), and reconfigured to returnless at the fuel rail.

Pressures without vacuum are 42/42.5 for the regulators, average idle pressure is around 36, and under max boost I have seen 55 or so.

The ECM has been reprogrammed slightly, and the coolant temp sensor wiring has been adapted to read 40F degrees hotter than actual, since it seems to run so cold with the bypass installed.

Timing has been verified at revs to match what the ECM says it is, and the plugs are a nice toasty brown. Running NGK BR6FS (I think) gapped short, @ .025 .

Yet although the fuel pressure peaks at 55 it does so only momentarily, therefore I fear for the motor...I want to avoid detonation. Typical pressure at full boost is only 45 or so, and maybe 40 under half boost. (5PSI and 2.5PSI, respectively)

And the rolloff hesitation, when it happens, seems unrelated to fuel pressure as it changes little, the motor seems well supplied with fuel when it happens according to a mechanical gauge. Say, 40PSI, steady.

The BEGI regulator came with a vacuum check valve for venting, which is installed, and a restrictor for the vacuum/pressure feed, which is not installed.

I have concerns for the longevity of the motor at these pressures, aside from the 'hesitation' when throttle is brought down slightly. That's just annoying but pressures must be correct.

So I'm asking if anyone here has been there done that and has some fuel pressure setup tips that are useful.

And thanking y'all ahead of time..... :D

Re: Procharger Rolloff Hesitation and Fuel PSI
 

WOW, THAT A MOUTHFULL :drink:

Re: Procharger Rolloff Hesitation and Fuel PSI
 

You need more fuel pressure under boost or its going to melt down. Check your reference line for the regulator,if you can't figure it out call me this weekend and I will reveiew everything with you as I use a almost identical setup,Smitty 989-823-7319

Re: Procharger Rolloff Hesitation and Fuel PSI
 

I am not familiar with boat setups but I know automotive versions come with a bypass valve that vents the boost off when you let off the throttle to prevent excessive pressure being built up in the blower and piping before the throttle blades since its still spinning high rpm yet the throttle has been shut either partially or fully. It also keep the inlet charge much cooler if you happen to throttle up and down a lot.

Re: Procharger Rolloff Hesitation and Fuel PSI
 

I agree with Smitty, more fuel pressure. My system is similar to yours, 502 mag with a Vortech. I know my motor has a sweet spot with fuel pressure. Too much and I can't hardly get it to idle, too little and the knock sensor will shut it down. I'm running an Aeromotive regulator with a gauge on it and a gauge on the dash. I typically need 45 psi of fuel pressure at idle and closer to 52 at wot. I take it you have a vacuum line from your manifold to the regulator and that it's increasing fuel pressure with vacuum? Do you have a regulator that increases under vacuum? Is it a bypass style regulator and do you have the bypass plumbed in either before the pump or back to the tank? Are you sure that it's working properly? What kind of fuel pump do you have? You need an aftermarket pump, Aeromotive or something similar. The stock Merc pump wont keep up. What size line are you running? You should be running 1/2 or 10 an also. Here's how my system is plumbed in order with 10 an line.
Tanks
Valve
Fuel separator
Aeromotive 100 micron filter
Aeromotive pump
Aeromotive regulator
Fuel cooler
Fuel rail

The bypass on the regulator goes back to the fuel separator.

Re: Procharger Rolloff Hesitation and Fuel PSI
 

I would call smitty if it was me.

Re: Procharger Rolloff Hesitation and Fuel PSI
 

Smitty said: "You need more fuel pressure under boost or its going to melt down. Check your reference line for the regulator" and I agree, the reference line is from the front of the plenum and has no restrictor orfice as the rear port does.

HRDLNCN said: "I know automotive versions come with a bypass valve that vents the boost off when you let off the throttle to prevent excessive pressure being built up in the blower and piping before the throttle blades since its still spinning high rpm yet the throttle has been shut either partially or fully."

I am familiar with such setups particularly with turbo'd motors, yet this setup does not incorporate an overboost blowoff or bypass valve. It is a thought but the symptom does not occur with closed throttle blades. However I may have to check the throttle valve blade adjustments as they may be off (which would misinform the ECM as to true throttle angle). BTW I have about 50 IAC counts at idle, maybe too high?

BADKACHINA wrote: "I know my motor has a sweet spot with fuel pressure. Too much and I can't hardly get it to idle, too little and the knock sensor will shut it down."

Hmmm..maybe I am seeing knock sensor action dialling back timing. Hadn't thought of that.

"I typically need 45 psi of fuel pressure at idle and closer to 52 at wot. I take it you have a vacuum line from your manifold to the regulator and that it's increasing fuel pressure with vacuum?"

I like those numbers. I'm nearly 10 PSI short across the board, however a prior setup was in that range but way rich.

"I take it you have a vacuum line from your manifold to the regulator and that it's increasing fuel pressure with vacuum? "

Two regulators, actually, both plumbed, but lets talk about vacuum. Vacuum is an expression of air pressure. 14.7 lbs air pressure is what we consider to be 'no vacuum', or zero on a vacuum gauge. I want to be clear because I view zero vacuum as 14.7 lbs atmospheric pressure, or BARO. So we usually use zero on the gauge as a reference, and I will now. So, when vacuum INCREASES as at idle, the regulator REDUCES pressure or fuel. When vacuum DECREASES (or, as in under boost condition, goes past 'zero') the fuel pressure continues to increase. It can be confusing unless I look at it from a zero AIR pressure standpoint, then it's clear that more AIR pressure produces more FUEL pressure at the regulator.

"Is it a bypass style regulator and do you have the bypass plumbed in either before the pump or back to the tank? Are you sure that it's working properly? What kind of fuel pump do you have?"

I'm not clear as to what 'bypass' means, but the Essex (SX) has 1 in 1 out and 1 return line. That return line goes to the BEGI regulator, which has 1 in and 1 out (to the stock filter/separator return port). The Essex pump (SX) is the mate to the Essex regulator, rated for 1000 HP or more and surely up to the task.

"What size line are you running? You should be running 1/2 or 10 an also. "

This is a questionable matter. First let me list order of components fitted.

tank
stock fuel separator/filter
pump
SX regulator (bypass?)
BEGI regulator
fuel cooler
stock filter/separator (return port)

The SX regulator outlet goes to the stock rail/

Hose sizes are 3/8 throughout, although from pump through rail it's Aeromotive with AN 6 I think. Pressure gauge is at the rail port, fitted with the dash gauge sender (but right now the mechanical gauge is there).

The BEGI regulator supposedly is the one that will compensate for boost, and today I will perform setup and testing of pressures with a vacuum pump which will also do pressure to substitute for the reference line at the plenum. This should tell me if the regulator is severely misadjusted and allowing boost pressure to bleed off too fast, or if it really is a supply problem.

A key item I have considered is the inlet line at the rail. This would be the most restrictive point, aside from the separator outlet to the pump, where the stainless pipe is probably 3/8 inner diameter.

Look you guys, thanks plenty for your experiences. This helps a bunch.

Re: Procharger Rolloff Hesitation and Fuel PSI
 

I'm running same setup. I idle at 36-38 psi And it jumps up to 60+ psi under boost. Mine did like yours and it ended up being my pump. It couldn't raise the pressure over 54 psi. You need more than 52psi. I have pistons to prove it.

Smitty is the Man! Talk to him.

Re: Procharger Rolloff Hesitation and Fuel PSI
 

I Sell Sx Pumps And Have Read The Post And You Have Some Typical Problems That We See All The Time. Did You Increase The Fuel Line Size And Pre Filter Size. This Must Be Done Due To Larger Hp Requirements.
Also What Size Is The Tank Pick Up. If The Lines Are To Small The Suction Pressure Is To Great And The Pump Will Cavatate. This Will Give You Spiking Fuel Pressures And A Lean Condition.

Re: Procharger Rolloff Hesitation and Fuel PSI
 

Thanks, guys.

I found the setup is OK, and I adjusted to BEGI regulator to max and that did OK, plenty of pressure.

70+

Perhaps we will chat again, I enjoyed all your views.

THANKS.

wrench-NE Grasslands USA

Re: Procharger Rolloff Hesitation and Fuel PSI
 

Please let me know what you decide. My detonation detector went off twice, that I know of, and I am now in the process of a re-build as a result. If your ecu acts the same as mine (I started with a 7.4MPI not a 502 which has a different ECU) it shuts down TOO LATE and then keeps the retard in for at least a minute. I trust every respondent to your thread but I am going to install a an LM-1 O2 sensor to take the mystery out of what might be causing any lean conditions. I will be able to send Mark @ precision a data recording of F/A, RPM, and fuel pressure. The reason I have my problem is related to keeping the stock injectors (less than 30#s). The stock set-up (M-1 5PSI) did not lean out, but when I went to Gill exhaust, ported Merlin heads, with big valves, roller rockers and a mag cam, I needed more fuel. The injectors programed to 90% duty cycle @ WOT did not flow enough fuel. Mark warned me about this but initial plug readings seemed to be OK. My point here is to go to the basics A/F is what it is all about. You can make other changes such as line sizes etc but what you are trying to achieve is to keep the motor out of melt down. If your programmer can see the correct fuel pressure he can program the correct ratio to keep you out of trouble. If she runs good with the proper ratios then live with the hesitation. If you see damaging ratios under certain conditions then start chasing the various suggested fix's one at a time.

Re: Procharger Rolloff Hesitation and Fuel PSI
 

Hey Bob,
Sorry to hear that you have to rebuild again. I have been parting out my 7.4MPI and have a bunch of EFI parts I'd be happy to get out of my basement for a little beer money.
I do have a set of larger than stock injectors that came with a second MPI setup I bought for my 7.4MPI modifications.
Let me know if you are interested...

Re: Procharger Rolloff Hesitation and Fuel PSI
 

Hi Patrick
Thanks for keeping in touch. I am interested in your injectors What size and how much? What about fuel delivery parts? [email protected]
Bob

Re: Procharger Rolloff Hesitation and Fuel PSI
 

Hi Bob,
I replied to your e-mail from a couple of days ago.
I'm not sure what size the injectors are, but I'll get you any info off of them I can.
Talk to you soon,