3B Rebuild and Performance Notes

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So the ARPs I left them finger tight in the block as ARP said with lube on them. I did go in small increments but on the last one I went to desired torque then backed it off about 1/8th turn and then retorqued to make it a constant accurate reading. I hear what your saying about lots of small torques as it could get weird. Thats why I did the backoff tighten for the final torque. I guess Ill leave the head on as I dont particually want to buy a new gasket and go through all the time either.

The studs did have the allen fitting on the tops for tightening.
 
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Yea it kinda sucks when you wanna change something it costs like 200 bucks to reassemble it...

On a different note,
You mentioned about sealing up the throttle body. I had to mod my shaft spacers and seals a bit after the linkage broke apart and i had to weld some washers to the sides of the linkage peice. Made it a bit thicker, so i had to shave the spacers a bit. I didnt take it right apart, but it was way tighter than stock when it was reassembled. I used to notice a bit of oily residue seeping out around the shaft, but not anymore and not for awhile...
Also heard, back when i swapped to the 3B, you can mod a 2H venturi/throttle body to fit and it gives better response and flow due to the larger bore.... wonder if they seal up any better...
Maybe machining an o-ring groove into the shaft would help some. Id like to get a second unit to play with and pressure test..
 
Yeah ive heard about the 2h throttle, but only a hear say. Ive got a spare 3b throttle assembly, but be darned it I can get the thing apart. Machining an o ring on the shaft was my thought too. These throttle plate assemblies are not meant to see positive pressure.
 
gerg said:
Yeah ive heard about the 2h throttle, but only a hear say. Ive got a spare 3b throttle assembly, but be darned it I can get the thing apart. Machining an o ring on the shaft was my thought too. These throttle plate assemblies are not meant to see positive pressure.
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Gerg I think I have a 2H throttle body kicking around if you want to take look at one next time you come by.
 
Traveller told me about it when i did the diaphragm spring swap. I know frm looking at a pic that the hole pattern isnt the same, but a adapter plate/TB spacer easily made up.

And no they definitley were not designed to see boost.

I was looking at the back of the 2H pump(governor housing) with the mechanical throttle, and its almost identical if not identical to the 3B. Just mirrored because its on the other side of the engine. Makes you think..... werent some 3B pumps on that side? Mechanical throttle would eliminate a lot of issues....
 
yotahed said:
Traveller told me about it when i did the diaphragm spring swap. I know frm looking at a pic that the hole pattern isnt the same, but a adapter plate/TB spacer easily made up. And no they definitley were not designed to see boost. I was looking at the back of the 2H pump(governor housing) with the mechanical throttle, and its almost identical if not identical to the 3B. Just mirrored because its on the other side of the engine. Makes you think..... werent some 3B pumps on that side? Mechanical throttle would eliminate a lot of issues....
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Yeah the automatic 2H had the mechanical throttle setup. They also have a vacuum actuated flap to kill the engine instead of a EDIC. That flapper setup is in the same place as the throttle on the manuals. It leaked like crazy when we turboed my brother Auto 2H. It would spray oil out and across the engine bay. With the 5spd motor and setup in it now there has been no issues. It also picked up about 2-3psi with no other changes.
 
Were there ever any such a linkage for the 3b pump? I would think that model of pump would used on more than just the 3b... Would be interesting to run the numbers and see what I come up with...

Posted via IH8MUD app
 
Had a brain storm while posting in my boost comp thread.

Ive been looking at and researching injection pumps with the butterfly/pneumatic governors (denso, mercedes, some marine applications) and many of them only use a vacuum supply from the intake venturi. The sense line is simply a vent at the pump itself for atmopheric press. reference.
I think (in theory) eliminating that line on the 3B system would affect the rate at which the diaphram progressed to the full load stop under boost. Most likely improving response and acceleration. Alternately, a restrictor in the same reference line would accomplish a similar result. Since under SUSTAINED boost, both sides of the diaphragm are under the same pressure, and the diaphragm spring pressure is all that's pushing towards full load. But since the the vacuum port hole size is much smaller at the venturi, positive pressure would be slower WHILE BUILDING boost against the reference side, which has a much larger hole. This would probably be felt as similar(and contribute) to turbo lag, or a flat spot, as it would be "fighting" against the slightly higher pressure of the reference side. And I myself do experience this. Even though I am building boost, the motor doesn't seem to really "take off" until around 10 psi. Almost as though the fuel just kicked in.
Where it "should" be almost a linear rise in power.
Am I making any sense ?


Sent with greasy fingers.
 
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yotahed said:
Had a brain storm while posting in my boost comp thread.
As a side note, Ive been looking at and researching injection pumps with the butterfly/pneumatic governors (denso, mercedes, some marine applications) and many of them only use a vacuum supply from the intake venturi. The sense line is simply a vent at the pump itself for atmopheric press. reference.
I think (in theory) eliminating that line on the 3B system would affect the rate at which the diaphram progressed to the full load stop under boost. Most likely improving response and acceleration. Alternately, a restrictor in the same reference line would accomplish a similar result. Since under boost, both sides of the diaphragm are under the same pressure, and the diaphragm spring pressure is all that's pushing towards full load. But since the the vacuum port hole size is much smaller at the venturi, positive pressure is slower to build against the reference side, which has a much larger hole. This would be felt as similar to turbo lag, or a flat spot. And I myself do experience this. Even though I am building boost, the motor doesn't seem to really "take off" until around 10 psi. Almost as though the fuel just kicked in.
Where it "should" be almost a linear rise in power.
Am I making any sense ?


Sent with greasy fingers.
Click to expand...

Makes sense, your just allowing the boost pressure to push the pump to fuel harder and faster. Would be easy to test with some sort of pressure bleed valve.

Edit: the other option would be to adjust the spring load to allow it to supply more fuel faster.
 
Yea thats exactly what I figured. You can get those pneumatic "speed controllers" at princess auto for like 5 bucks. Adjustable from fully shut to fully open and lots of sizes of them..
I used one as a "fooler" for the map sensor on the 2LTE to run higher boost and lower fuel.

Sent with greasy fingers.
 
Wheelingnoob said:
Edit: the other option would be to adjust the spring load to allow it to supply more fuel faster.
Click to expand...


The only trouble with that is youd be messing with the idle fuel delivery and idle speed. I put the longer mercedes spring in mine awhile back and I had to tweak the idle down a bit.
Made a large difference in pick up and response, but still get the lag like I mentioned above.
Just seems a lot simpler to eliminate that line or restrict it like you say, than to go fiddling with spring preload. I seem to be fine full out and fine starting from a stop, just the in between tuning seems to be "off"
My compensator is ready to install in a few days as well, so ill try it both with the line connected, and not connected and report back with some results....

Edit: Only thing id be worried about is the stress on the diaphragm from 18psi on one side....

Sent with greasy fingers.
 
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So further to what you are say is: A weak spring will not give you full rack travel, or very slow rack travel?

Im really interested in hearing your results. Im getting that "Doh! Why didnt I think of that?" feeling.


To limit max boost on the leather, you could "T" into the line and put a granger valve to vent say 4 or what ever psi you wanted. That way it would build pressure quickly, yet only allow a set presure. This would also bleed presure from your intake so the sending oriface would have to be small to limit the waste, yet large enough to transfer the signal quickly. A needle valve as the sending oriface would allow easy adjustments without dissasembly id think.
 
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Well to be honest, Ive always kind of thought that line was unnecessary, once I learned how the system actually worked.... Just forgot about it, and never got around to trying it.
What got me really thinking is when I looked at the injection pumps that used the same system, and that line was omitted and was simply a vent on the forward cavity.
So " DOH!, why didn't I think of that?" was my thought exactly. Lol

As far as springs, if you look at my old boost compensator thread from a year or two back, youll see the diff. between the length and wire thickness of the two springs (stock vs mercedes 240D)
From what I understood at the time, it would extend further at full load at the same max fuel setting than the stock spring, while giving a more progressive rise in delivery, and giving similar idle fueling as the stock spring. Meaning you get more fuel without actually turning up the fuel screw any.
Now Im a little skeptical on the more at max thing, since I dont know if the stock spring actually reaches the max rack travel stop or not, but I will say that it made a large seat of the pants difference in part throttle response and top end power and response on the highway. Turbo spooled quicker and it just seemed better overall. Ill tell you what I tell everyone else: spend the 10 bucks and ten minutes and just try it, see how you like it.

As for the pressure bleed for the rear diaphragm cavity, great idea! Why didnt I think of that? Lol. Seeing as how it sees a constant vacuum at idle (around 4-5" Hg) should be fine with limited pressure. Add a one way check valve so it doesnt bleed vacuum and we re golden I think...

Sent with greasy fingers.
 
gerg said:
So further to what you are say is: A weak spring will not give you full rack travel, or very slow rack travel?
Click to expand...

I think the spring isnt as much the issue as minimizing the pressure on the forward cavity. Any positive pressure there will fight the rack movement no matter what spring you run.

Until the pressures of the two cavities equalize, youll get that flat spot or resistance in fuel rack movement while building boost. Once they equalize, all is well and fueling will max out (assuming the spring does actually max it out)
The thing I cant quite figure out is what is happening at steady throttle and boost (say 10lbs @ 2300rpm) Is there still vacuum holding the diaphragm back from full load? Even though the entire system is pressured up and equal across both sides?
That woild be the hole in the theory right there.....
OR
Perhaps the rear cavity is constantly at a lesser pressure because of the smaller orifice of the venturi and it is not a closed system like an air tank. As the air charge is constantly moving, the pressure is never really constant.......
My head hurts now....
Where's that airflow dynamics book when you need it?

Sent with greasy fingers.
 
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Herez the springs side by side. Merc is like twice the length.

Sent with greasy fingers.

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So here's a bright idea I came up with while going to get a cigar for myself and a bottle of wine for the wifey,

What if,

We relocated the butterfly/venturi IN FRONT of the turbo? Like right in front, 3-4 inches from the inlet.

It would(should) operate like the NA setup it was designed for, No boost leaks, no overloading the diaphragm, No extra restrictors/controllers and valves etc., s*** to fu*k up.

hmm.
Modifications for this?:

1.Throttle cable relocated with new bracket-> not hard

2.New adapter and piping for both venturi to intake pipe and charge pipe to intake manifold.- some welding probably required.-> still not too bad

3.Longer lines from venturi to Injection pump. Possibly smaller I.D. for the vacuum side to account for increase in length. would need non-collapsing tubing of course or a very long spring inside, or better yet, copper or AL tubing.->not hard

Thoughts?
 
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So this would have two problems I can think of right off the bat.

1st is that the pre turbo air volume changes wildly depending on boost. It does not correlate like it would in its stock position. For simplicity sake take 14.7 lbs boost. Post turbo in the normal location the engine sees normal air volume WOT at 2000rpm. With the throttle plate pre turbo it would see double the volume (aproximated just a tad). So the pumping losses through the throttle would increase 4 fold. What are the consequences of that.... not good im guessing. Throttle pumping losses are a real pain and can decrease your VE signifigantly.

2nd is the pump would loose alot of the throttle sensitivity. I think it could get quite laggy, especially at low rpm low load... like wheeling

Now on a gas engine its not quite like this as the MAF is pre turbo to give accurate mass to the computer for fuel delivery, where as the throttle body is post turbo close to the manifold alowing for throttle response. Gasser also suffer throttle body boost leaks and many offer kits to o-ring shafts and such.

On some super duper weird diy carburator turbo jobs the carb can go pre tubo which can be a huge hassle to size properly as it has to flow enough fuel for WOT high rpms as well as idle properly with no boost. That is a major range to operate within. Plus they have icing issues as well as your whole intake piping is pretty much a bomb.
 
Yea that makes sense, I was thinking of the propane turbo 22r s thst have the carb/mixer in front...now that you mention it.
Okay so back to the drawing board. Lol
ill stick with the original plan with the hose disconnect. Maybe give it a go tommorow seeing as how its a simple test really.

Sent with greasy fingers.
 
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