This is The Bomb ... with Turbo!

[asavage]

I would have expected smoke at part throttle with boost up.

Are you pressurizing the IP housing too, via the IP vent line? That would be the same connection as stock. The hose that goes on this nipple here (A/C air plenum shown):


and you can see the same hose connected to the non-A/C plenum in this pic:


Is this connected to the replacement plenum still? If so, then the IP housing gets pressurized too, which would (somewhat, see below) compensate the pressures across the diaphragm . . . but I wonder what the consequences of pressurizing the IP housing are.

I imagine that significant boost air would be bled into the crankcase, and thence through the road draft tube and out. Or if a PCV-like rebreather system is fitted, back into the intake, upstream of the turbo intake.

Hmmmm.

[Knucklehead]

Hmmm. How is that going to work? Any boost at all = fuel delivery to full?

Yea, it would (and it did) without this-

I m very unhappy with this setup. The old setup with the TB ahead of the turbo worked much better. I haven't turned up the pump any yet but my exhaust pressure is significantly higher than intake. Can't get the pyro over 600°, which means no fuel. I could just turn the pump up, but I don't like the exhaust pressure even as it is. I'll fiddle with it a little more just to learn, and I might even try try it the old way just to compare, but I'm sure I'm going to change the pneumatic governor and dump the TB. Anybody want a polished TB?

[asavage]

Anybody want a polished TB?

I've been meaning to ask you: can you summarize your aluminum polishing techniques and tools? I'm quite envious.

[Knucklehead]

Think progressively finer.

Japanese castings like the valve cover or thermostat upper tend to be high quality finish cast so usually you can get away without any grinding or sanding and go straight to using a buffing wheel starting with brown compound, green, white, blue. Rarely do I go beyond green.

But something like the main thermostat housing is a coarser casting. I started with a 180 disc on an air die grinder and then a 320-

Keep it all wet with WD40 and don't think you can skip steps. I don't like to use cartridge rolls or any other rounded grinder/sander except in corners because the surface will look dimply when done. Using a disc larger than the backing allows you to conform the edge into the curves. That's my own technique, not what I learned in the polishing shop. I think it's a lot better. And thank you!

[asavage]

Japanese castings like the valve cover or thermostat upper tend to be high quality finish cast so usually you can get away without any grinding or sanding and go straight to using a buffing wheel . . .

Is this one of those laminated-cloth affairs I see at the swap meets, which seem to be mounted to a bench motor (I'm thinking like a bench grinder)?

Or are they mounted to a portable device, such as a air die grinder?

I suppose I should Google for the answer to those, and go educate myself, but there does seem to be a lot of disinformation, or at least misleading information, in the area of polishing the kinds of things I want to polish, which are also the things you are polishing, so I thought I'd ask you first.

. . . starting with brown compound, green, white, blue. Rarely do I go beyond green.

I work next door to a welding supply shop, and they have the sticks/bricks of colored compound, so I guess I have a source. I do need a much better compressor though, and probably to upgrade my die grinder again

[Knucklehead]

Is this one of those laminated-cloth affairs I see at the swap meets, which seem to be mounted to a bench motor (I'm thinking like a bench grinder)?

That sounds right. Long arbor is good. Heavy pedestal needed. Use a wheel for brown and another for green, ie don't mix compounds (duh). Thinner and smaller for tight places. They do make 1" cloth wheels for use on a die grinder but don't work that well. Still, some places ya gotta have em. Or at least I do.

Oh, and, obviously, hard metals are hard to do but look better and last longer. Can't polish chrome at all. Steel will look like chrome but rust if not coated. Copper and brass polish up easily and look knockout but tarnish in no time if not coated. Fun to play with. Aluminum calls my name. Kind of in between. Stainless is my favorite.

[asavage]

Really great info, I appreciate it.

[zen]

Refering back to Why only 600ºF?

Whats wrong with it?? (assuming your pic shows turbo before tb)

I have no trouble at all that way...and at least that way it does not cause a problem with suction on the input to turbo and hense possible turbo oil seal failure...

[zen]

Regarding.... can't get over 600...(is that F or C?). Where are your lines going to the IP connected?? One to the TB but the other??

[Knucklehead]

Here are both sides so you can see the hoses.




I speak Fahrenheit. I'm not sure what the deal is just yet with low fuel delivery. Probably I turned the adjustment down during disassembly and polishing. Could be the vent tube is not angled quite right. No worries about that really, but I don't like the exhaust/intake pressure ratio. Sorry, I want perfection. Maybe I can get out there this weekend and find something out.

If yours works so well, why are you changing it?

[zen]

changing it in order to see if egt will drop some...so then can run more fuel!!

lpg and prehaps methanol/water injection next...

re your ip lines...looks like 1 connected to tb and one turbo side...(?)ie the same as if non turbo...(if not please ignore whats written below!!)

if this is so then the ip still sees the same pressure/vac as if it was n/a..it wont know its under any boost ...the line that is before the tb (not the one conected to the tb) needs to see atmosphere (ie no boost) for the ip to sense it needs to fuel it up...if this line just sees atmosphere only then it will be at max fuel virtually all the time its on boost however..makes for an interesting drive!!

to compensate and make controllerable/drivable one can bleed in boost/atmosphere(either way works,just depends upon how you want to plumb it) to this line..the more boost it sees the less fuel it gives...i use an aftermarket cab mounted turbo wastegate adjusting valve.(the type that would go in line with the wastegate senseing pipe that is used to bleed off boost so the wastegate stays shut at higher pressures)that way i can controll ip fueling from inside cab from n/a to max (read dangerously unusable)...

it works very well..only reason i wish to change it is i wish lower egt's..i have a rebuilt turbo ip, it seems it cant hurt to swap and see what happens..i will miss the variable in cab fueling though!!

[Knucklehead]

I have been driving the Datsun since our car was smashed by a hit and run driver on May 6th. It is running very well, much better than I initally thought, but I am still going to make the pump manual. I have measured a lag in boost between the plenum and the manifold. The diaphragm spring is fairly stout, and I was thinking that there must be at least a couple of pounds of pressure differential between the front and back side to pull the diaphragm back against that spring. I put matching gauges on and measured nearly two pounds of pressure lag when below 5 lbs, most pronounced at the bottom, diminishing with increase. I'm running up to ten lbs boost right now, but there is a lot of lag and I think the Throttle Body is the reason. It was a lot more responsive when I had the TB in front of the turbo.

Also, I was thinking that the TB causes a lot of vacuum in the cylinder at idle. So what? Well, forever and always, my SD has made a small bit of blue smoke when leaving a stop. I think when idling the vacuum sucks some oil into the cylinder and when you first open the throttle it blows off. So why don't gas engines do that, you might ask, they have TBs too. Yes, they do, but they don't have oil jets under the pistons, bathing the cylinder walls in oil either. And diesels that have oil jets don't have TBs. Except ours. We shall see.

I am currently working on switching the IP to a manual governor and will share the experience. Waiting for pics from Zen....

[philip]

-SNIP- So why don't gas engines do that, you might ask, they have TBs too. Yes, they do, but they don't have oil jets under the pistons, bathing the cylinder walls in oil either. And diesels that have oil jets don't have TBs. Except ours. We shall see.

Yes our SD22 have a Throttle Body with two big bypass airs (throttle blade and fix venturi inside) ... that only draws about 4" vacuum at idle ... and less when you accelerate. A typical gasoline (at sea level, idle, Neutral gear) runs about 18" vacuum. Notice a gasoline idling engine for a few minutes prolonged will puff when leaving a stop too (a good example are older Dodge Caravan who known for puffing valve stem seals). All it takes is loose seals and/or sloppy intake guides.

All gasoline engines having turbos that I know since early 1980s have included oil jets under the pistons like diesels. The SD (and some but not all gasoline/turbo engines) have a spring/valve on each jet. Did you miss the SD jet spring/valves?





I can only guess that 10 psi is the cut point.

[Knucklehead]

Well, hell. There went my theory. I didn't know that the jets cut off at low speeds. Duh. Kinda obvious. Cutoff must be over 10 because my oil pressure low is 20. Well then, let's just say I hope the lack of vacuum will make a change.

[philip]

-SNIP- Well then, let's just say I hope the lack of vacuum will make a change.

Only saying ... not that I say is -yours- but ... "knurling" the valve guides will work for a while to minimize sloppy valve stems. But the old sloppy valve/guide will return after some miles (5-10k?). Additional, the knurling now adds the spinal groove for oil to get into the intake. Isn't that just lovely?

My oil is still oem and does not "puff" as you mention.