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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philip
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Re: I'd like more HP

#16

Post by philip » 13 years ago

ecomike wrote:
philip wrote:Max 61 HP is 3800-4000 rpm. Max torque is 102(or less) torque @ 1900-2400 rpm. It's a DIESEL ... Mike! Good grief. Diesels like this thing LOSE torque well before HP top.
Torque Chart
I seem to be noticing that! But in fifth gear I am trying to maintain a steady speed. That becomes a problem when I encounter a hill, climb, so are you saying more HP alone wont cut it, that it needs more torque as well to maintain a constant speed when I go up and overpass?
Torque the transmission input shaft

For a small power against heavy vehicle, you need more gears.

As is in these little trucks ... the gear spacing is about 700-800 rpm (1-2 is more space and 4-5 is less space) at 3000 engine rpm. Because these wide space gears are coupled to a diesel, you pass RPM over max torque peak only enough to ensure the next higher gear reduces the diesel engine to torque peak (1900-2400 rpm).
-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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#17

Post by ecomike » 13 years ago

Not to get sidetracked but what ratio is the rear end on the 720s?
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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ecomike
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#18

Post by ecomike » 13 years ago

Well I sent and enquiry to the eRAM guys and seems that the the problem with the SD22 would probably be that the IP would not respond with additional fuel to match the added air supply at WOT, at least in the applications I had in mind. THe eRAM is only designed for operation at WOT (at any rpm). It might work OK at lower rpms, and in lower gears that 5th, but that was not what I originally had in mind.

I have plenty of power around Houston in fourth gear (and lower) but I don't like running the engine and transmission at the higher RPMs to maintain highway speeds of say 60 to 65 mph. It's only a problem in 5th gear when I go over a long tall bridge like the ship channel bridges for example. I typically have to drop into fourth gear for them, depending on traffic, and whether or not I can get a running start before I hit the grade. But I can feel the speed dropping off when in 5th gear when I go up any overpass, and the throttle from 1/4 throttle to WOT in 5th gear on the incline does almost nothing. So the increased air flow from 1/4 throttle to WOT, or increased air flow capacity in 5th gear when I hit the incline is doing nothing already, so in that situation a boost of air is not going to do anything useful either. If anything it acts like it needs more fuel at that point. I am getting no smoke, nada, nothing at WOT in 5th gear when it bogs down going up an incline.

Does this sound like a fuel problem at that point instead of an air supply problem? Or is it just normal for this beast?

After reading and rereading multiple threads here, I am starting to think I should at least recheck the smoke screw setting which I set over a year ago, and I don't recall if it was hot or cold weather or a hot or cold engine when I set it. Might even be time to change the fuel filter.
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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philip
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#19

Post by philip » 13 years ago

Mike: What is your single, simple question? No more than 20 words.
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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ecomike
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#20

Post by ecomike » 13 years ago

philip wrote:Mike: What is your single, simple question? No more than 20 words. Thanks.
20 words, OMG, just shoot me please! OK, I will give it a try:

How can we get 5-10% more power in 5th gear without going to extreemes of cost or complexity.

:D
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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ecomike
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#21

Post by ecomike » 13 years ago

ecomike wrote:Not to get sidetracked but what ratio is the rear end on the 720s?
Philip, I asked this specific question because I am pretty sure the rear end ratio I have is different than the stock 720, so I wanted a baseline for comparison. I am trying to determine which of 3 possible rear end ratios I have currently. That relates to power, torque to the wheels as I understand it. Changing my rear end gear ratio with JY swap might be a place for me start, or might not? Right now I don't know what I actually have or what the stock 720s had. It is pertinent to my restated question at least for my vehicle.
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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Knucklehead
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#22

Post by Knucklehead » 13 years ago

ecomike wrote:It's only a problem in 5th gear when I go over a long tall bridge like the ship channel bridges for example.
You mean the one by Clinton Drive over the P of H Industrial Complex. That's gotta be like 8 percent. Damn, everything slows down over that!
ecomike wrote:the problem with the SD22 would probably be that the IP would not respond with additional fuel to match the added air supply at WOT
I would immediately disagree..., except that you have messed with the smoke screw, so that makes it a possibility.

Ok Mike, what you must do before anything else is put in a pyrometer. That will tell you whether you need more fuel or not, and it will keep you from getting things too hot if you turn it up too much. If you go up that bridge running 1000° you need to turn it up, 1200° and the eRAM guys are definitely wrong in your case.
'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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#23

Post by philip » 13 years ago

ecomike wrote:
philip wrote:Mike: What is your single, simple question? No more than 20 words. Thanks.
20 words, OMG, just shoot me please! OK, I will give it a try:

How can we get 5-10% more power in 5th gear without going to extreemes of cost or complexity.

:D
I want to be Carnac. You get to become the envelope ANSWER.

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Last edited by philip 13 years ago, edited 4 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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philip
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#24

Post by philip » 13 years ago

ecomike wrote:-snip -...the stock 720, so I wanted a baseline for comparison. .... -snip-
The 720 in 2WD with a SD / 5spd final drive is: 3.88:1

The 185/75x14 tire is: 24".

Gear box:

1st 3.592
2nd 2.246
3rd 1.415
4th 1.00
OD 0.813

Weight: 2810 (2 fuels) (Add Full tank, me)
-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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asavage
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#25

Post by asavage » 13 years ago

I don't think that 10% more HP (6 HP more) in 5th is going to allow you to pull those grades. You are probably off the peak of the torque curve.

Honestly, I think you are already exceeding the recommended continuous output of the SD22. If you tried that with the Z24, you'd have worn it out already.

Car engines are not designed to run at or near full output for more than 10-20% duty cycle. Unlike truck and aviation and agricultural and generator engines. They aren't built the same.
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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ecomike
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#26

Post by ecomike » 13 years ago

philip wrote:
ecomike wrote:-snip -...the stock 720, so I wanted a baseline for comparison. .... -snip-
The 720 in 2WD with a SD / 5spd final drive is: 3.88:1

The 185/75x14 tire is: 24".

Gear box:

1st 3.592
2nd 2.246
3rd 1.415
4th 1.00
OD 0.813

Weight: 2810 (2 fuels) (Add Full tank, me)
Ah, HA! I forgot the tire size. I am running 235R15s! That makes a difference. Thanks!
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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ecomike
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#27

Post by ecomike » 13 years ago

Knucklehead wrote:
ecomike wrote:It's only a problem in 5th gear when I go over a long tall bridge like the ship channel bridges for example.
You mean the one by Clinton Drive over the P of H Industrial Complex. That's gotta be like 8 percent. Damn, everything slows down over that!

Yes, that is one of them, there are few others now that are even worse on the Beltway 8 loop, (Really steep!!!!), now called the Sam Houston Toll road. Those usually knock me down to 3rd gear and about 35 to 40 mph or if I get a running start (no traffic) I might manage 4 th gear at 40 to 45 mph at the peak.

The small ones that are like every 3 blocks on the 610 loop are the ones that really annoy me. If I stay in 5th the speed drops from say 60 to 45 or 50 mphs on many of them, then I have to drop back to 4th to hold 55 to 60 or to get back up to 60 quickly.

ecomike wrote:the problem with the SD22 would probably be that the IP would not respond with additional fuel to match the added air supply at WOT
I would immediately disagree..., except that you have messed with the smoke screw, so that makes it a possibility.

I currently have the smoke screw set to almost smoke, but not smoke (which I think Is wrong from what I have read). But like I said, I think my understanding of how to set the smoke screw is better now. I had set it originally when the engine was badly fouled with soot (bad diaphram at the time), and I was more concerned about getting rid of the smoke and getting the idle down. I have an FSM and the threads here now as a guide to reset it properly. So I will probably do that next. Also the engine has cleaned up and is running better now. Just recalled it was winter with three dead glow plugs when I set the smoke screw so it is probably way lean now!


Ok Mike, what you must do before anything else is put in a pyrometer. That will tell you whether you need more fuel or not, and it will keep you from getting things too hot if you turn it up too much. If you go up that bridge running 1000° you need to turn it up, 1200° and the eRAM guys are definitely wrong in your case.


The eRam guys are wrong about what exactly?
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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ecomike
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#28

Post by ecomike » 13 years ago

asavage wrote:I don't think that 10% more HP (6 HP more) in 5th is going to allow you to pull those grades. You are probably off the peak of the torque curve.

I agree, but I could still use more power.

Honestly, I think you are already exceeding the recommended continuous output of the SD22. If you tried that with the Z24, you'd have worn it out already.

I drive it pretty conservatively now. Especially since I noticed that I get very little out of the last 50% of the throttle in 5th gear. If I can not run at 30 to 40% of WOT in 5th gear I drop down to 4th gear at 35 to 40% of WOT for the cruising operation.

Car engines are not designed to run at or near full output for more than 10-20% duty cycle. Unlike truck and aviation and agricultural and generator engines. They aren't built the same.
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. At that time if I gave it anymore than 30% throttle it ran like sh#t and smoked up the entire freeway in seconds to the point of being scarry as hell.

Once I replaced the diaphram, reset the IP lever to the run position (note that I have a manual cable choke on mine to control the start, run, stop actuation), and reset the idle and smoke screws, I was able to run in most gears at WOT with no problem, perhaps because I have the smoke set screw set too lean. I don't think I am getting over 2500 rpm in 5th gear, maybe not even over 2000 rpm in fifth gear when cruising. By WOT I mean durring acceleration in 1st to 4th gear only, and cruising in 5th gear at WOT, which I no longer do as it runs just as fast at 40% of WOT in 5th gear as it does at WOT in 5th gear.

Hope that clarifies things????
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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asavage
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#29

Post by asavage » 13 years ago

ecomike wrote:. . .but I could still use more power.
Who couldn't? My point is that your rig is fine for some uses, but you sound as if you need about another 40 HP to perform as you want, and you are not going to get that from an SD on an ongoing basis without significant mods.
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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#30

Post by philip » 13 years ago

ecomike wrote: I agree, but I could still use more power.
It's the RED color that slows and reduces diesels. :roll: You'll only find yellow or red SD's in marines or generators. Need pictures? :wink:

I NEVER need more HP in my truck. WHY? Because truckers know the balance of engine torque rpm and gear box output torque used to minimize vehicle speed loss on up grades.
-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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