3B Rebuild and Performance Notes

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Found this while surfing,

http://archive.commercialmotor.com/...umatic-governor-system-for-turbocharged-engin

Some of it is hard to understand/not really explained well, but another point of view nonetheless....

Testing will have to wait for a few days. Need some boost line as id like to measure the actual pressure/vacuum in the rear cavity while driving and under boost.

another thing that confused me....
Amaurer did a test without a turbo, saying that even at revs(no load) the vacuum is actually higher than at idle... and only when you are accelerating does the vac drop.

Quote from his thread:
"Steady-state
650rpm - 4"Hg
2500rpm - 5"Hg
Accelerating hard (any RPM)
0.5 - 1"Hg
Deccelerating hard (any RPM)
10"Hg
 
So,
Initial test.

Unhooked reference line and plugged off.

No changes to anything else.

Amazing difference in power upon reaching spool up @1600-1800. Truck takes off like a rocket. And no changes to fuel screw. Very linear power with boost level.(up until a certain point when the rack is at max travel) As soon as boost starts coming up, I'm assuming the diaphragm is forced to full load, since there is now zero resistance on the reference side.

As a side effect of this, the engine keeps revving until boost drops back down. Makes for interesting road driving. Very similar to a sticky IAC valve on a ford.(ranger owners will know exactly what I'm talking about)

A one way check valve on the vacuum side may solve this ^^, keeping positive pressure totally out of the system. As soon as vacuum drops off it would hold at 0" hg-0 psi (relative to atmospheric of course) and spring pressure would take over at WOT. This would need to be tested once again, but it is obvious that the vacuum side does see boost.

Alternately a needle bleed valve on the reference side, with a needle bleed valve coupled with a check valve on the vacuum side would probably be smarter given the off throttle issue and giving control and tun-ability of both sides.

After this short test, it was immediately apparent what power was available and the change to the power curve was unmistakable. To note my fuel is turned way down at the moment and the truck is almost scary fast, compared to yesterday...

Sent with greasy fingers.
 
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No smoke, not a signifigant change in EGT. maybe a tad higher(50-80F or so) and came up a little faster, nothing too crazy though. I would think that would be relative to the fuel being dumped in faster and sooner, yes, but the also the same amount which it would see later on in the rpm range before the test. So really I've only moved the curve down lower in rpm and made it more linear relative to boost level, (instead of "nothing, nothing, GO! as it was before"). It would still be the same max setting/delivery as before. Pretty crude test, as Im aware, but it did prove three things.

1. the reference side assists the off throttle behavior, as well as restricting the diaphragm movement while building boost before equalization of the two chambers.
2. Vacuum side does see boost.( I thought it might but wasnt entirely sure.)
3. restricting (in this case a total block off) the reference side would provide more linear fuel delivery with boost level.
 
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Another of my crude drawings of what I think might work.

1.)One way would be to eliminate the reference line( may or may not cause off throttle issues?) and tee into the vacuum side with a bleed valve(to limit the boost pressure on the diaphragm) and a one way vacuum check valve(to eliminate bleeding of vacuum.)

2.) the second way would be to retain the reference line and tee it with a bleed valve to slow the pressure build to the front cavity. vacuum side the same as #1.

3.) the last option (but I will probably try this first) is eliminate all positive pressure from the system. Disconnect the reference side of the venturi and block it off, and put a breather on the pump on the front cavity nipple. A one way check valve oriented to block boost and allow vacuum would be inline on the vacuum side line. This would allow vacuum and spring pressure to control the throttling alone. once positive pressure is reached, check valve shuts and spring takes over. Not sure how this would work out in reality, but would be the easiest of all 3.

the next test would be to see what the vac side is doing as various part throttle positions at various RPMs.

thoughts?

VenturiMod.webp
 
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after reading about removing the reference line i gave it a try and wow has scary amounts of power

but i didnt drive to long until i switched back to normal because the engine keeps running away

not at idle but while your driving

i only took the hose of and didnt block any thing

is this why the engine starts to speed up uncontrollably?

Thanks
 
Is it turbo'd?
Yes it makes for unpredictable throttle control to say the least, but does reveal the capabilities waiting to be harnessed.
Im in the process of putting a few parts and peices together to do some more refined testing, and some numbers/data to back it up.
Sent with greasy fingers.
 
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Test #2

I bought an adjustable needle valve and a couple hose barbs. princess auto-$11.99 with 1/4 NPT ports. The 1/8NPT was cheaper but its hard to find a 3/8" hose barb without buying a few adapters so I went with the bigger one.

TEST #1
I simply hooked up the needle valve in-line with the reference hose.

I ran new 3/8" hose and transferred the internal spring to the new hose as well to prevent kinking.

With the valve fully closed, the revs climb slowly to about 1400rpm while idling. not sure why.
Opening the valve gives strange results depending on how much air is allowed past. power is good and take off is good, but shifting is really strange, as the engine keeps revving a bit after taking your foot out of it, or drops off completely, again depending on where you set it. Kind of unpredictable and I wasnt impressed after fiddling and driving it around the block a few times...

TEST #2
I grabbed a 3/8" brass T, Put it in place of the needle valve, and ran a line to the needle valve, leaving the 2nd port on the valve open to atmosphere.

This way worked MUCH better. Fully closed, you have a stock system. Open it a tad, you bleed a bit of boost while accelerating. I played with a few positions on the valve and found 3-4 half turns from fully closed worked really well. Too much and you experience more run on while shifting, and twitchy "on-off" throttle behavior.
This method had none of the "weirdness" or unpredictability, response was very good, power on take off was better, and boost started to build 100-150rpm lower. I can bark the tires going into second gear, which I've never done before. EGT change was minimal once again. Im thinking that since boost built a little quicker, any extra fuel is burnt efficiently.
I read in the Nissan thread above that a pressure difference in +2-3psi was seen on the reference side of the diaphragm compared to the rear cavity, which would explain why this gives the results it does.

Now as a side effect, it also stopped my idle from diving while downshifting coming to a stop. When I would put in the clutch it would dive down below the set idle, and come back up a second later. I especially liked this because my truck vibrates bad at 600 rpm. Shakes everything and makes a helluva racket inside. So when it dove like that, It rattled everything loudly for a second. annoying. Well, no more of that. And it seems to idle smoother as well overall.

I will be testing this same setup later on with the reference port relocated to the intake manifold side of the throttle plate(instead of directly above it). I've heard several accounts that this is a better place for it, but I will test it and see.

I'd like to offer up some pressure/vac numbers, but I need a couple more pressure guages and a decent mount so theyre not hanging out the hood while Im testing. I'd like to have a video so people can see in real time whats happening.

couple pics of the setup
cheers

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That is very interesting. Would you say power at wot at 2000rpm has increased? Sounds like the lower rpms has. Is there a way you could do a pocket dyno or something? Not to get an accurate number, but to try and quantify the change. I look forward to trying it out on my truck when I get the engine back into it. It would be cool to some how link the valve to the throttle so that during normal driving it could be closed, but at wot the line would bleed.
 
Whats a pocket dyno? like one of those handheld accelerometer deelys that you put in your gear ratios and weight and whatnot? maybe theres a phone app for that? lol

I think the change comes from the front side of the diaphragm not seeing a higher boost than the back side. Really a fine line there as opening the valve too little and you dont see much change (although response is noticeable). Open it too much and you get more boost acting on the back side, giving the "on-off" twitchy throttle.
Just right and it's....well... just right.

I only really notice it when I push the the pedal more than halfway to the floor, and it really kicks in. Otherwise it drives very similar to before, although like i said, it seems a lot smoother overall especially when upshifting and downshifting.

Ill see what i can do for a quantification for ya.

cheers
 
Im not the most techy guy out there either, but I just got my wife an ipad for christmas and there are some very cool apps for that thing. I got it specifically cus she is a teacher and there are lots of teacher apps.... and some very cool dyno programs too. I know there are apps for phones for sure, but I dont own a phone, other than my house phone. I dont know how accurate they are, but using it to detect positive tunes would be better than the seat of the pants technique. I like that off boost it behaves normally. What turbo are you using?
 
The turbo is a off brand (godspeed) "T3" off ebay. turbine housing is .42 and compressor is .48. Ive no idea on the actual wheel diameters. same mounting as a garrett.

If im lugging in 4th @ 1500 (around 50km/h) and I stomp it, it starts building and reaches 10psi at 1870-1900. Not as quick to spool as Id like, But I've also got the fuel turned way down for economy. The part of the fuel arm that contacts the stop is just barely off 90* towards the front of the pump. I usually run it much higher and the turbo spools a bit quicker.

On the highway in 5th @ 2400rpm(85-90km/h), if I let off and let it the boost drop, then stomp it, it goes to 15-18psi almost instantly. I run a blow off valve too and it seems to help keep the thing spooled up between gear changes.

Been a good hairdryer for ~40K kms so far. no oil leaks yet. i think i paid under $300 for it shipped.

I tried a couple apps out, one run gave me 185hp at the wheels with 400ft/lbs......
I dont think so....:hhmm:
 
Took the truck for a drive on the highway this morning.

Turns out the setup doesn't work so well at highway RPM's. Throttle surges to full out at anything above 3psi. Almost impossible to hold a steady speed and EGTs climb fast when surging, probably because the throttle is only partly open, but the fuel goes to full.
Funny thing was, it still did it with the valve completely shut as well. Im thinking because of the difference in the length of the lines. Unless the needle valve doesnt fully close(which im pretty sure it does) I cant see any other reason for this except for the length difference. I tried moving the valve right next to the T with a very short hose, and still the same result.
When I took it off halfway through my trip(was almost unbearable operating at highway speed) It went back to completley normal operation.
I had replaced both lines with 3/8" ID fuel injection hose. and retained the spring in both sides.

I messaged the guy who built the turbo SD22 motor pictured above yesterday, and he said he put the needle valve in line on his setup, so I may try that again, and see what happens on the highway. Seems the ill effects are not as pronounced when driving around town and going through gears a lot. I saw the issues right away as soon as I got up to speed on the highway.

Ive got a strong feeling after todays run that the mercedes spring may account for the difference in pressures across the diaphram, and may be the best bet rather than dicking with the airflow. The system is VERY sensitive to the smallest of changes as I've learned.... But Ill keep at it and see what I can figure out.
 
found this on Pirate. On a nissan again, but same overall throttle system.

Only issue with this, is the pump is almost impossible to get to idle correctly. A guy opened the front rack cover while running the stock setup, and said the rack moves constantly back and forth like a sewing machine, and is never really "set" or still at idle....


If this could be made to work well, I'd be all for it.

Mechanical1.webp


Mechanical2.webp


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There are a 3 or 4 guys on the nissan and Pirate forums that have tried this. I emailed them for any additional info.

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This is quite interesting. I wonder if anyone has pics of the mechanical linkage for a 3B? I remember seeing one, but cant see to find it again. There was an option, so it must be doable. I remember wheelingnoob saying he switched his brothers 2h over to mehcanical linkage. Any pics Jereme? How does the 2h idle?
 
If you could mirror image that (2h) pumps rear body it looks almost the exact same. I mentioned that earlier in the thread. Im sure it would idle just fine, its a very different setup than just a direct link to the rack, I believe. Springs and linkages and god knows what else in there lol. Ill have a look in the exploded diagrams in the manual for the 2H.
But I would also like to hear what wheelingnoob has to say nonetheless.

Im gonna have one last crack at putting the needle valve in as a restrictor instead of a bleeder. Maybe I didnt have it opened enough to begin with...


Sent with greasy fingers.
 
If you look at the 13-BT pump and the 2H (12HT looks like a completely different animal) pump diagrams, they have very similar mechanisms to control the throttle. Of course, the 2H has no boost comp, but the innards are much the same. the throttle looks to be connected to the rack through a series of bell-cranks, levers and springs and a "floating rod" assembly. no direct hard contact to the rack, which would explain why the mechanical systems shown above are very touchy and dont hold a consistent idle.

That said, if you could somehow get a hold of a 13-BT rear half, or a similar Denso inline injection pump with a mech. governor/throttle, you could probably bolt it right up providing it was for a pump on the left side of an engine.....
Finding that kind of unobtanium is probably easier said than done.

It's strange the 3B was never offered with an automatic trans but the 2H was.. :hhmm:
 
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