I'd like more HP ... without Turbo

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

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Knucklehead
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#31

Post by Knucklehead » 13 years ago

ecomike wrote:The eRam guys are wrong about what exactly?
If your pyro is running 1200°, they are wrong that your IP isn't supplying enough fuel.
When I first got this beast I could not go over about 30% of WOT because the IP lever was stuck, locked in the start position with a failing diaphram on top of it.
Possible confusion here. Understanding the Pneumatic Governor is fundamental to making the SD22 run its best so please be patient with me while I ramble.

The position of the IP lever (which controls the Full Speed Stop) determines the maximum rack travel. In Start position, the lever is forward, allowing the Governor Spring to push the rack all the way forward, even a little more than in Run position. Only the diaphragm connects to the rack, not the Stop Lever. The little spring loaded button in the end of the diaphragm (Ungleich Mechnism) bumps into the Stop lever when there is no (or little) vacuum. Start position doesn't forcibly put the rack anywhere, but it allows the Governor Spring to push it really wide open. Adjusting the smoke screw back moves the Full Speed Stop forward = forward rack, more fuel. The governor is by default WOT. Only engine vacuum on the diaphragm (or max rpm flyweights) pulls the rack back against the spring (that's why opening the TB when cranking makes starting easier). If you have holes in the diaphragm, idle vacuum won't be able to overcome the spring, and the rack will be more forward in relation to the TB position than it should, in effect fueling it and choking it at the same time. If you have a bad diaphragm, idle is the worst situation, but if it's WOT (at the TB) the condition of the diaphragm doesn't make any difference. IOW, both conditions you described would lead to lots of fuel. So if you mean that you could only get 30% before the embarrassment made you back out of it, maybe yes, but not because the IP was stuck in an underfueling condition.

Image

Perhaps it would be more accurate to say that we have two throttles on the SD22: The IP which is primary, and the TB which is secondary and artificial, because remember, air does not need to be metered to a diesel. These two things have been made to operate in a parallel fashion. If you open up the TB (WOT) or take it off, and take the diaphragm off the IP so that you can see the back of the rack, you can control the engine with your hand directly on the rack, but it's very sensitive.

Image

Thank you Phil for the many diagrams and the page about the Ungleich Mechanism from years ago. I spent quite a while getting my head around that.
'82 standard cab 3 axle SD22 turbo
'89 int'l 9700 Cummins 444 (855 ci)
'29 HD FD export model

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philip
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#32

Post by philip » 13 years ago

Knucklehead wrote:Thank you Phil for the many diagrams and the page about the Ungleich Mechanism from years ago. I spent quite a while getting my head around that.
Thank you for speaking concisely and accurately about the Pneumatic Governor. The Ungleich Mechanism is not mentioned to the SD supplementary book. :wink:

When's your next theory/teacher available? :)
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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ecomike
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#33

Post by ecomike » 13 years ago

Knucklead,

You have it backwards, the eRAM guys agree with your position. I was the one having a hard time believing it would increase torque or HP on my system as my system is currently operating, performing and calibrated (smoke screw, etc., at least under the conditions they recommend it be used for (WOT only).
And the conditions I was thinking of using it for was high speed (50 to 70 mph) cruising in 5th gear, normally at 1/4 to 1/3 throttle and at WOT for a few seconds when I encountered a grade while in 5th gear.

I should note that their system is design only for WOT use for a few seconds at a time in passing or racing at WOT. It is activated by a micro switch attached to the throttle and triggered only at WOT. It is not designed for continuous use. Therefore it would only be of use at WOT.

But here is, was my thinking. I did not see or feel any difference between WOT and 1/2 throttle while in 5th at my top speed(yes I know you all have explained the torque drop off issue quite well) which now makes me think I have another problem that should be located and fixed first, unless it is just a torque drop off issue. But I think I should be feeling something when I give it that extra 1/2 throttle from 1/2 to WOT in 5th gear.

It is hard to describe, but I can feel the response from 1/2 to WOT in 5th gear when I first shift into 5th gear, or a flat road. But I reach a peak speed where I can back off from WOT to 1/3 throttle in 5th gear with no change in engine or jeep speed. And then I can go back to WOT in 5th and still feel no change in engine speed, sound, load or jeep speed.

The other part I was talking about was back before I fixed several things (like replacing a diaphragm with a 1/2 inch hole it and fixing the manual choke style cable I use for start/run/stop lever postion control!), and yes I was afraid to give it more than 1/3 throttle then because it was embarasing if you will and more importantly I was afraid the fire department would show up to put out the fire! It also seemed to rev to high too fast if I tried to floor it back then. Now I can floor it all time with no smoke at all.

So where should I install, or test the temperature with the pyrometer. Is an external infrared good enough, or does this test need to run while driving, in 5th gear at peak load for instance? I have plenty of thermal testing hardware, but you did not say exactly where to take the readings, nor when?

ecomike wrote:
The eRam guys are wrong about what exactly?

Knucklead said:
If your pyro is running 1200°, they are wrong that your IP isn't supplying enough fuel.

Quote:
When I first got this beast I could not go over about 30% of WOT because the IP lever was stuck, locked in
the start position with a failing diaphram on top of it.
Regards,

Mike

1985 Jeep Cherokee Pioneer, 2WD, retrofitted with SD-22 & 5 spd manual trans, a 4X4 Gas Wagoneer ltd. (XJ) Jeep, 4.0 L w/ AW4 auto, and now 2 spare 2wd Jeeps, 87 & 89.

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#34

Post by asavage » 13 years ago

ecomike wrote:It is hard to describe, but I can feel the response from 1/2 to WOT in 5th gear when I first shift into 5th gear, or a flat road. But I reach a peak speed where I can back off from WOT to 1/3 throttle in 5th gear with no change in engine or jeep speed. And then I can go back to WOT in 5th and still feel no change in engine speed, sound, load or jeep speed.
That's the way the SD22 is. Actually, a lot of diesels are that way. Once the IP goes to full-fuel for a specific RPM, moving the manual lever (on a non-pneumatic system) makes no difference. Unlike a gasser, when you ask for more fuel on a diesel that is already fully fueled by the IP's settings, you aren't going to feel any more "pull".

Put another way: even though there is a throttle butterfly on your SD, it is not a restriction when it's open more than a low percentage unless the revs are way up there. At off-idle, open the throttle 1/3 and the IP goes to full-fuel (for that RPM: some IPs will do more fuel per stroke as the RPM increases, others do timing changes). Though you have only "demanded" 1/3 of the pedal travel, the SD is fuelled to maximum.

The SD is even more pronounced than other diesels this way. To me, it acts like a lawnmower governor. Pull a load, push the pedal to a given position, and the engine pulls very hard -- up to the exact RPM where the butterfly vacuum signal to the IP diaphragm is enough to pull back the diaphragm. Then the power cuts off pretty abruptly. But the IP is at full fuel until that point. On mine, it's pretty abrupt dialback of the fuel when the RPM setpoint of the butterfly is acheived by the engine RPM.

Does that make sense? It's very common in small diesels to not feel any more pull from 1/2 to full pedal, unless you are rev'd way up there.
So where should I install, or test the temperature with the pyrometer.
Exhaust manifold, preferably near where all four cyls come together. See this post for some pics on an LD28.
Is an external infrared good enough, or does this test need to run while driving, in 5th gear at peak load for instance?
No, and yes. The EGT varies a lot on load, and EGT is what you are measuring.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

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philip
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#35

Post by philip » 13 years ago

ecomike wrote:-SNIP- But here is, was my thinking. I did not see or feel any difference between WOT and 1/2 throttle while in 5th at my top speed(yes I know you all have explained the torque drop off issue quite well) which now makes me think I have another problem that should be located and fixed first, unless it is just a torque drop off issue. But I think I should be feeling something when I give it that extra 1/2 throttle from 1/2 to WOT in 5th gear.

It is hard to describe, but I can feel the response from 1/2 to WOT in 5th gear when I first shift into 5th gear, or a flat road. But I reach a peak speed where I can back off from WOT to 1/3 throttle in 5th gear with no change in engine or jeep speed. And then I can go back to WOT in 5th and still feel no change in engine speed, sound, load or jeep speed. -SNIP-
Now why does the OEM spec end up with a 3/4" full throttle opening?
Clue: It has something to do with the Pneumatic Governor (... that position's the "control rack" ... that rotate the pinions). Hmmm.

Image
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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Knucklehead
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#36

Post by Knucklehead » 13 years ago

Those are great pics Al! Though I have never used an amplifier; what's the deal with that?

On an SD22 (or 25) I would put a pyro probe here:
Image
(notice with the SD25 they got rid of the TB!)

ecomike wrote:You have it backwards, the eRAM guys agree with your position.
I'm sorry, I thought the claim was that "the IP would not respond with additional fuel to match the added air supply at WOT". I'm just saying that it WILL respond one way or another. But the point is that I got more power by adding AIR only. All things being at factory settings, 7 lbs boost made a big difference. I think two or three lbs would do the trick.

Sometimes you learn the most by destroying something. I've done a lot of destruction. Once we put an old VW motor on a stand, tied the throttle WOT, started it up and ran. I was hoping I could get out of the way before I got hit with flying pieces. Surprise! I couldn't get it to blow up! The thing couldn't get enough air to overrev. So we put on some dual port heads and BAM!

Assuming a state of proper tuning, the SD22 needs air more than anything else, unless the IP has been turned down or something to diminish peak factory fuel flow, then you need the pyro to set it to peak fuel as in your case. Then you're back at trying to get more air in. Head work? Turbo is easier. Don't want a turbo? How about a cam? I've got one. It won't help you with the small ports and besides, putting on a turbo is easier than changing the cam. Hmm..., how to get more air in. Nitrous! Maybe, seems kind of impractical for what seems to me a nonsport application. I think you're back at the fan idea.

I can respect the feeling that one should appreciate the little SD22 for what it is and get used to it. But I just happen to think that it has a lot of potential, so why not go for it? I think we're getting too complicated here so let get simple. We want to pedal harder. That's all it is. More pressure on the piston. More burnable (gotta have air) fuel in the cylinder. Will we hurt something? I don't think it's unfair to ask the SD22 to pedal harder than a Z22, because the hardware is better. But it was put in road vehicles as a fuel saver so its power potential is untapped. Bottom line? Sure, why not?
'82 standard cab 3 axle SD22 turbo
'89 int'l 9700 Cummins 444 (855 ci)
'29 HD FD export model

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#37

Post by asavage » 13 years ago

The ISSPro unit comes with an external amplifier and signal conditioner. I'm not sure why; possibly to reduce the size of the gauge pkg?

The point I made was that Mike's current implementation of a basically stock SD22/61 HP is well beyond what Nissan had planned for it in the 720, and that it performs as well as it does is fortunate.

The Cherokee (Pioneer) body has much more frontal area than a 720, it's heavier, and the 720 was not really set up to try to run with today's big dogs (ie 65+ plus A/C + cargo + hot air).

Maybe adding a turbo, add'l cooling, and appropriate gearing or a gear splitter (GearVendor, USGear/Doug Nash, Ranger).

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#38

Post by philip » 13 years ago

Where would you put a probe ... here? That rear shield has a trick bolt, facing the wire wall.
Image

And while you may like the absent Throttle Body, I don't like the crude C.A.V. injection pump AND the huge fuel pump located on the END of the cam gear housing.
Image
Last edited by philip 13 years ago, edited 1 time in total.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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Knucklehead
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#39

Post by Knucklehead » 13 years ago

Philip wrote:Where would you put a probe ... here? That rear heat sheet has a trick bolt, facing the wire wall.
What a coincidence! I debated on whether to use that very picture of your engine but opted for clarity. Plus I'd be surprised if there are very many heat shields left.
I'd use a hole saw to cut a nice opening through the shield just above the clamp. I don't know exactly how the shield looks underneath, but if it's not possible, I'd dump it. A pyrometer is top priority for someone who's readjusting the IP.

I'm with you Phil on that ugly IP.
Point well taken Al.
'82 standard cab 3 axle SD22 turbo
'89 int'l 9700 Cummins 444 (855 ci)
'29 HD FD export model

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#40

Post by asavage » 13 years ago

Knucklehead wrote:I'd use a hole saw to cut a nice opening through the shield just above the clamp. I don't know exactly how the shield looks underneath . . .
Relative placement (click on image for larger):
Image

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#41

Post by philip » 13 years ago

asavage wrote: Relative placement (click on image for larger):
Here's an outside look of Al's manifold. (non EGR) Note the forward shield over cyls 2 and 3 are gone.
Image
Image

BUT here is the outside of my California shield. (CA EGR)
Image
Last edited by philip 13 years ago, edited 2 times in total.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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#42

Post by bacho » 13 years ago

For your gear ratio, My 720 has a 4.10 in the back. Its a 4x4 model and it will top out about 75 or so before the motor sounds like its revved too much.

As for pulling 5th on hills, dont think you are gonna get it in an NA motor. I can accelerate up a hill in that gear, but I have to have about 8psi boost at the bottom and keep 8-10 all the way to the top.
1992 nissan pathfinder 4x4
1985 KC 720 4x4
1982 KC 720

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ecomike
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#43

Post by ecomike » 13 years ago

Seems I have missed out on several replies here lately. I use to get email notices of replies, but did not get them for these last replies?

I hit the JY about 8 weeks ago and found a suitable replacement, non-Nissan, rubber hose for the air filter connection to the throttle body intake pipe assy, and moved my air filter intake about 10"s forward in the jeep bay, to get colder, ram air into the air filter housing's intake. My old OEM Nissan hose had a new hole in it (underneath from rubbing on the AC compressor) that I luckily discovered since it was letting in hot, unfiltered air the last 2 months.

My butt dyno, and the cars I can now pass on the freeway, LOL, instead of their passing me, tells me it made a small but noticable improvement. I did test the intake air temp at idle and it was about 120 F, before I moved the air filters intake forward.

Only other change I made was fixing the (replaced the valve and connected the missing vacuum lines) Max AC damper's vacuum valve which should have decreased the AC load on the engine by decreasing the HP side temperature, and thus pressure, and thus load, since it is actually in Max AC mode now and not normal mode (still running about 90 to 95 F at 85 to 100% humidity here). Also, I have been running ULSD the last 4 months, but I doubt that has had any significant effect, although it seems to be running smother with ULSD.

Still thinking of buying the Tiny Tach that Al suggested (probably will as soon as I recover from my last 2 jeep purchases, I have 4 jeeps now) and maybe an e-Ram to play with. I plan to replace the manifold gaskets in about 2 months, so I may tap a hole for the pyrometer probe then.
Regards,

Mike

1985 Jeep Cherokee Pioneer, 2WD, retrofitted with SD-22 & 5 spd manual trans, a 4X4 Gas Wagoneer ltd. (XJ) Jeep, 4.0 L w/ AW4 auto, and now 2 spare 2wd Jeeps, 87 & 89.

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#44

Post by Nissan_Ranger » 13 years ago

danged double post...

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The old 'six gun' was as popular as the cell phone in its time and just as annoying when it went off in the Theater.

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#45

Post by Nissan_Ranger » 13 years ago

I tried the E-ram a couple of years ago. Didn't work worth a poop and blew up on the 3ird test run; commutators let go.

N_R
The old 'six gun' was as popular as the cell phone in its time and just as annoying when it went off in the Theater.

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