Tacos 4KTQ I0vt Swap: The Red Baron - buying parts again

[AngryTaco]

I think ive bent over 20 valves now lol! Then again I think ive tried doing things a little different in some areas

[AngryTaco]

Im wiring in a push button for the csv. Tired of this hotstart bullshit

[Wilford Brimley]

Im wiring in a push button for the csv. Tired of this hotstart bullshit

What are your control and system pressures? Are the injectors new?

I've had CIS cars start in 0 degree temps without a CSV

[AngryTaco]

All pressures are within specs. Only problem I cant solve is control drops to 10psi immediately upon shutdown

It starts fine when cold. Its only after sitting for 20 mins when hot

[Wilford Brimley]

Fuel pump check valve or accumulator.

What is the residual system fuel pressure? It should stay at ~3bar for multiple hours.

[AngryTaco]

Sorry thats what I was meaning. The residual pressure that you check at the wur immediately drops off upon shut down

[Wilford Brimley]

Valve closed (reading system pressure) or valve open (reading control pressure)?

You could close off the valve on your pressure tester (system), then shut off the car before it dies to see if the pressure is bleeding off between the metering head and the tank.

[AngryTaco]

ohhh gotcha. I will check that tomorrow. If the system pressure bleeds off upon shut down, does that indicate accumulator, or does control pressure signify that?

[Wilford Brimley]

System pressure would indicate issues with the fuel pump check valve/accumulator. Also look into this:

http://www.sjmautotechnik.com/trouble_s ... html#vapor

[AngryTaco]

I actually just stumbled onto this thread over at quattro world

http://forums.audiworld.com/showthread.php?t=2194572


The 2nd post accurately describe every symptom I am experiencing. I believe it to be the accumulator. There is a junker 4000 in the local yard, so I think I'll pull it and replace it. I'm wondering if the relayed fuel pump put too much pressure through it?

[Wilford Brimley]

I'm wondering if the relayed fuel pump put too much pressure through it?

Negative. Your system pressure is regulated by the metering head (MC1 cars used shims, MC2 used an external reg like the NG engine). There was no increase in pressure, but there was a flow increase.

Assuming it is the accumulator, a big contributing factor to its demise would be the pump going from ~11.2v (what I have usually measured at the terminals) to ~13.5v. Extra flow will have detrimental effects on older parts in a fuel system (especially parts with diaphragms).

Case in point: a friend had a neon that kept eating FPRs. We eventually discovered that the PO had installed a relayed walbro 255 on an otherwise stock engine in anticipation of boosting the car. All of that extra fuel going back to the tank was raising hell with the reg.

[AngryTaco]

Interesting. Is there any kind of alternative to installing another accumulator? Or should I just grab one out of the junkyard and hope it works?

yay CIS lol

[scubadave]

YES!!! VEMS

[AngryTaco]

yeah yeah yeah! I'm working on it! Broke azz shit from school tuition

[Wilford Brimley]

Interesting. Is there any kind of alternative to installing another accumulator? Or should I just grab one out of the junkyard and hope it works?

yay CIS lol

Grab it, and soak those fittings in PB blaster.

If it doesn't work, you're out a few dollars. Only bad thing I imagine happening is the lines going to the accumulator break on the baron when you try to remove it.

[themagellan]

Interesting. Is there any kind of alternative to installing another accumulator? Or should I just grab one out of the junkyard and hope it works?

yay CIS lol

Grab it, and soak those fittings in PB blaster.

If it doesn't work, you're out a few dollars. Only bad thing I imagine happening is the lines going to the accumulator break on the baron when you try to remove it.

Wow - Nice CIS info dude.

Pro tip to not break those lines - Get yourself a set of vice grips and use cardboard or packing foam to clamp onto the metal line near but a few inches away from the fitting. If you put all of your force at the top of the line where the fitting is, that will be your path of least resistance. Allow it to give a little bit and it will come over time.

After super PB saturation, attempt to tighten, then untighten - Repeat this while holding equal parts pressure. I don't think anyone can take off crusty hydraulic lines better than me in a dirty garage haha!

[AngryTaco]

Well, guess I'm grabbing an extra accumulator today after I mail out a bunch of stuff.


Now here's a strange boost issue.....

1st gear through 4th, it will hold 14-15psi with out issue at any rpm

5th gear and the boost will skyrocket towards infinity......why!?

[Wilford Brimley]

Well, guess I'm grabbing an extra accumulator today after I mail out a bunch of stuff.


Now here's a strange boost issue.....

1st gear through 4th, it will hold 14-15psi with out issue at any rpm

5th gear and the boost will skyrocket towards infinity......why!?

Engine load increase.

[themagellan]

Well, guess I'm grabbing an extra accumulator today after I mail out a bunch of stuff.


Now here's a strange boost issue.....

1st gear through 4th, it will hold 14-15psi with out issue at any rpm

5th gear and the boost will skyrocket towards infinity......why!?

I'm willing to bet under full load your wastegate could simply just not be able to keep up - What are you running currently (hardware/spring)

[Wilford Brimley]

Another likely scenario is the stock 20vt WG being unable to bleed off boost with the tiny 30mm plunger when loaded up in a high gear. Check to see if there isn't a tear in the WG diaphragm too.

A good upgrade is the 34mm WG off of an AAN engine. It is a direct fit to the 20vt engine.


Are you using an MBC or the stock N75 to regulate boost?

[AngryTaco]

Using the stock N75 for right now. Diaphragm isn't torn and is relatively new. Already done numerous vacuum tests to make sure. I was starting to wonder if the wastegate had become a little too small

[dana]

Another likely scenario is the stock 20vt WG being unable to bleed off boost with the tiny 30mm plunger when loaded up in a high gear. Check to see if there isn't a tear in the WG diaphragm too.

do you have experience to back this up, or is this just a theory? I used a 20vt WG on my car, and never had an issue with boost creep. My car was around 350whp, maybe more at 30psi.

[Wilford Brimley]

Using the stock N75 for right now. Diaphragm isn't torn and is relatively new. Already done numerous vacuum tests to make sure. I was starting to wonder if the wastegate had become a little too small

Disconnect the N75 and see what the boost holds at through the gears. It should be pretty low, something like 7psi with a 2.2bar spring in, since the N75 is no longer applying pressure to the upper WG chamber.

[Wilford Brimley]

Another likely scenario is the stock 20vt WG being unable to bleed off boost with the tiny 30mm plunger when loaded up in a high gear. Check to see if there isn't a tear in the WG diaphragm too.

do you have experience to back this up, or is this just a theory? I used a 20vt WG on my car, and never had an issue with boost creep. My car was around 350whp, maybe more at 30psi.

I had my boost set at 17, and it would creep to 20 if I was in 4th or 5th.

You also have to remember that this is on a 20v, which has an awful exhaust manifold design when compared to the 3b/AAN. Not all of the cylinders even feed the WG...

[dana]

You also have to remember that this is on a 20v, which has an awful exhaust manifold design when compared to the 3b/AAN. Not all of the cylinders even feed the WG...

good point, mine was on a tube header.