Tuning with turbo (SD22 / '85 kc 4x4)

#16

#17

Now I have an issue that I have to shift pretty fast on hard accel to keep the motor from over reving, the boost shoots to about 15 when the gas is let off for a shift, would a BOV help that?I would prefer to kill that over rev.

That's because

I did not pressurize the IP on mine, that hose is open right now.

You need this-

to counteract the boost pressure that's holding the rack open.

RE: BOV (Blow off valve)
Ever heard of water hammer? It's a loud bang that happens in plumbing when you shut the faucet off quickly. All that volume of water moving in the pipes (let's say 1 gallon) has mass (let's say 8 lbs), which stops instantly. It's the equivalent of hitting the pipe with an 8 lb hammer. Plumbers put a vertical pipe in the system capped off and full of air to absorb the shock. A BOV does the same thing in a blow thru system where there is not enough air volume between the turbo and the TB to cushion the pumping energy stored in the rotating turbo wheels, ie you slam the TB shut but the turbo takes just a little longer to quit pumping so it makes a racket when it pumps into a dead end (surge). If you have an intercooler with a lot of piping that holds a lot of air volume that will compress some, you may never need a BOV. If you need one, you will hear it. I don't need one yet, but mine is still turned way down. Dump the TB and you'll never need one.

It can build boost sitting in my driveway with the clutch in, about 3psi.

At an idle in neutral? That 3 lbs should be enough to shove the rack open w/o a pressurized vent. I'm guessing it doesn't idle very well. Mine doesn't either, even with the pressurized vent.

#18

I understand how the hammer works, that why I made my area between the turbo and TB as much as practialy could. I will try pressurizing that line and seeing what happens.

It idles great, only builds boost with throttle but I thought the motor had to be under load to build boost? It did not do it before I adjusted the waste gate all the way shut.

#19

waist gate is adjusted closed at a given pressure.
or adjusted fully open at maximum pressre.

this is done without the engine running.

if it has too much boost after that then the exhauste housing is the wrong size,exhauste pipe is too big,or too much unburnt fuel in the exhauste manifold creating a jet engine...

a blow off return to intake is a good idea,also a throttle plate in the cold air intake that shuts of with clutch aplication,the late model RD28 has a vacum operated throttle plate for EGR purposes in the air cleaner box.shutting of the intake air keeps the turbo up to speed without over boosting.turbo must suit this aplication or you fill the engine up with oil.

#20

Well, there's a lot of info that is not yet clear about the setup, but the key point is that there is a spring that pushes the rack open. Idle happens when the relatively lower manifold pressure applied to the back side of the diaphragm pulls the rack closed. Open the TB, the pressures equalize and the spring pushes the rack open. Three lbs. in addition to the spring does not spell a nice idle. Something is wrong here.

Waste gates are for gas engines. No standard diesel should have one. If so it will be on a multiturbo setup or for emissions purposes.

I would be sure that you want to keep the TB setup before you invest in a Blow Off Valve.

You might want to put an exhaust pressure gauge on so you can see both sides of the turbo.

#21

Hey this is great stuff....I also have a turbo in the works and plan on ditching the TB, since the IHI RHB5 I will use can't take vacuum on the compressor discharge, so let me throw my control scheme out there for y'all to critique. I plan on using a vacuum reservoir and a pulse width modulated (PWM) idle control solenoid from a Ford gas application to regulate pressure on the accell side of the rack diaphragm. The PWM valve is essentially a three way solenoid valve which can either evacuate or vent to atmosphere the accell side of the control diaphragm. The other side would just get filtered air, no boost reference. Plan on using a throttle pedal from a GM 6.5 turbo app, which is just a spring loaded pedal with a potentiometer built in and a PWM controller to run the Ford idle solenoid. The downside is that vacuum pump failure, or PWM valve failing open, or catastrophic vacuum leak = engine run up to mechanical governed speed. I suppose some kind of mechanical shutdown is called for, but I haven't worked that out yet. The rest is off the shelf parts.

#22

Phil, I don't think that's going to work. But I can't articulate why right now.

#23

Here is my set-up, I pressurized the IP and is idled a little higher but did not pull as strong. I will have to go buy a T fitting to run my boost gauge and the IP at the same time to see what the boost looks like there.

#24

asavage wrote:Phil, I don't think that's going to work. But I can't articulate why right now.

Did you looked at this arrangement?

#25

What Phil is planning amounts to manual control of the diaphragm-controlled portion of the rack. Granted, there's the pot->PWM->Idle controller->diaphragm tree, but it is still pretty much manual control, excepting the internal overrides built in to the inline IP.

I can't envision the reaction time of that setup being nearly fast enough.

#26

so let me throw my control scheme out there for y'all to critique.

I think you'd be better off just removing the diaphragm and affixing the rack to the control arm.

#27

Anyone got a pic of the valve to turn the fuel up a little?

#28

It's the one with the wire seal and lock nut on it.

#29

Knucklehead wrote:It's the one with the wire seal and lock nut on it.

You know, to prevent people from "accidentally" turning it. Which, come to think of it, is not usually a good idea. Clever, those Japanese.

#30

Right beside the TB? Clockwise for more fuel, counter clockwise for less right?

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Tuning with turbo (SD22 / '85 kc 4x4)

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