Pulsation damper question

[azerty]

Hi. For some time now I have noticed some hesitation/stumbling above 3000rpm in gears 3, 4 and 5.
I have Lexus AFM, 550 RC injectors, Aeromotive FPR. I am running 0,8-1barr boost, and the screw of the AFM is set for maximum unmettered air.
My fuel pressure is set at iddle at 43 psi.
Checking for problems in the fueling system, I have foud that the screw on top of the pulsation damper was all out, just resting beneath the plastic cap.
I have screwd it all the way in and it seems to feel better now, the stumbling is almost gone.
Also, after I drive the car for a few minutes, if I pop up the hood, I find the FPR oscilanting between 38 and 40 psi.
So my question is this: is the oscilation of the FPR normal? Is it a bad pulsation dumper? Can it be fixed, or I should just replace it?
Thank you.

 

[IwantMKIII]

Not sure about the dampener but i can tell you that idle FP is high. I believe spec is around 30 psi.

 

[azerty]

The TSRM states that the pressure should be between 33 and 40 psi for stack aplication. I think I should up it to 45 or 50 because I have larger injectors, bigger turbo pressure, and more unmettered air.
Let's say the 550cc injectors make up for the increase in air flow due to the Lexus AFM, but more air and pressure are there. So the ECU is trying to inject more fuel to keep the stoich condition. So there is a high demand of fuel. I also have a 255 Walbro fuel pump to suply this fuel. I willl try to up the fuel pressure and keep you informed if it solved the problem.
Anyone here knows how this pulsation damper is made/works? Has anyone dissasebled one yet?

 

[IwantMKIII]

Your theory on increased pressure is wrong among many other assumptions. You ECU will adjust just fine. What it WON'T adjust for is too much FP that is way out of spec. Not that you are, but still you should know.

 

[gaboonviper85]

The TSRM states that the pressure should be between 33 and 40 psi for stack aplication. I think I should up it to 45 or 50 because I have larger injectors, bigger turbo pressure, and more unmettered air.
Let's say the 550cc injectors make up for the increase in air flow due to the Lexus AFM, but more air and pressure are there. So the ECU is trying to inject more fuel to keep the stoich condition. So there is a high demand of fuel. I also have a 255 Walbro fuel pump to suply this fuel. I willl try to up the fuel pressure and keep you informed if it solved the problem.
Anyone here knows how this pulsation damper is made/works? Has anyone dissasebled one yet?

Your injectors are bigger there for they flow much more...at idle your fuel psi should be at 30ish as your ecu will tune the injector duration with the o2 sensor....increasing fuel pressure will just make it harder for the ecu to do this as the o2 has a very narrow window of compensation tollerance....

This is why we have piggyback fuel controlers for open loop operation and an o2 sensor for closed loop

 

[TurboStreetCar]

A bigger turbo and larger AFM increase the CAPACITY of allowable airflow into the engine. Capacity is not always 100 percent utilized.

The larger AFM is letting un-metered air in while at the same time the injectors are letting additional fuel in to compensate, raising fuel pressure is furthering the addition of fuel, creating a rich condition causing the TCCS to work that much harder to compensate for and maintain stoich ratio.

A larger higher flowing turbo will only add additional air into the motor at or above stock boost levels, not across the board. The lexus AFM that is allowing extra unmetered air into the intake track will effectively raise fuel cut by tricking the TCCS into "seeing" less airflow.

This allows for possibility of allowing more airflow into the engine to generate more power. The larger injectors coupled with the larger AFM results in the air fuel ratio remaining close to the same.

Now, is it 43 psi with the vac line connected or disconnected? Do you have a good external boost gauge that reads vacuum? Do you have a wideband?

Firstly, If its 43 with the vac line connected the fuel pressure needs to be lowered. as per TSRM (http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=A&P=8) the fuel pressure with the vac line disconnected, or with the engine not running should be between 33-40psi.

If you have a boost/vacuum gauge, when the fuel pressure is fluctuating, check if the vacuum is fluctuating as that would cause the regulator to change fuel pressure in reference to fluctuating vacuum.

If you have a wideband, report Air/fuel ratios during all times of concern. If you dont have a wideband, get one.

 

[isnms]

And the screw on the fpd is not an adjustment, it's an indicator.
I don't think you want it screwed all the way down.

 

[azerty]

Ok' I realize now that I am anything but helping the TCCS by raising fuel pressure.
I have set the pressure by shorting B+ and FP as the TSRM says, with the ign to ON without the engine running, with the vacuum line connected.
I do have an aftermaket gauge for boost and wideband.
But the oscilating fuel pressure is at idle. The wideband shows between 14 and 15, the boost gauge shows -0,7 barr.
At wot I have tens and elevens on the wideband at 0,8-1 barr boost.
What is puzzeling me is that in firsth and second gear all is ok, but starting with the third, I get some stumbling, over 4000 rpm.
That is why I thought it was not getting enough fuel, or that the fuel presure dumper was not working as it should.
Any one knows more about this part?
Is that screw supposed to be all in, does it holds/connects to something in the interior? If I have found the screw all out, what should I do?

 

[isnms]

http://www.cygnusx1.net/Supra/Library/ToyotaTech/

•EFI#3 Fuel Delivery & Injection Controls

also a forum search of pulsation, damper

 

[azerty]

Thank you very much for the links. I admit I haven't searched the forum, but it looks like it doesn't returns any results.
So, if I get it right, the little screw has just diagnosting purposes?
Can you think of anything else that can cause what I am experencing?

 

[TurboStreetCar]

If your air fuels are correct at the time of the problem i would look elsewhere from the fuel system.

Check plugs and wires. When did the problem start?

 

[CRE]

It was explained to me by a Toyota tech, a VERY long time ago, that the screw in the FPD is used to set the damper's opening pressure at the factory. Unless you know what that pressure is and have to tools to adjust it while tuning it it's a bad idea to (pardon the pun) screw with it.

 

[azerty]

Damn. Anyone has one just laying around and would send it to me?
I had narrowed the spark plug gap to 0.008 if I can remember well. But I was told by a friend who is a mechanic that if it would have been the spark, it would have done this at any rpm,even low rpm.
Just in case I will try the plugs on the coils and on the spakplugs.

 

[Poodles]

Spark blowout usually occurs at torque peak, so probably not the issue.

 

[isnms]

Thank you very much for the links. I admit I haven't searched the forum, but it looks like it doesn't returns any results...

It does return over two pages of results.
When you click on the link I posted, you then have to click [Search Now] to get the results.

I had narrowed the spark plug gap to 0.008 ...

0.008 What?
Stock is 0.8mm (0.031in)