Peak torque may or may not be peak efficiency (I don't think it correlates normally), but only if you have some use for all that torque. You may produce 193 lb-ft of torque very efficiently, but if you only need 40, you're wasting a huge amount.

But, as I said, without the go-pedal floored you're not getting 193 lb-ft at that RPM anyway.

I think it's just running at that RPM not running at WOT at that RPM.

Looks like the SD is not going to work so well however I have an option.
Nissan also makes an L-series diesel that produces more power and has a higher torque peak. 124 lb/ft @ 2400 RPM compared to the SD's 104 @ 1800 RPM.

I think the section I underlined in the second excerpt I quoted is the most telling. This would be a huge undertaking, except in the "if my aunt had a beard, she's be my uncle" sort of way. Amusing to think about but inevitably unrealistic.

Stock A4 chassis VW TDI (New Beetle from 98, Jetta from '99, Golf from '00) do better than that 40+ mpg AND will handle far better. Side air bags, ABS, traction control, A/C.... It's amazing how much technology has moved on since the early 80's.

The hoped for 2200 rpm at 60 is 27.3 mph per 1k rpm. Those generation VW diesels have 28.9 mph / 1k rpm. Is 2100 rpm at 60 mph close enough to your desired 2200?

The 4th gen VW Golf (Jetta, New Beetle) is stock chip limited to 4500 rpm, and with the exception of the N-B aerodynamics, has enough software limited power to pull to darned close to 4k in top gear. That's 116 mph with stock tune.
Chip tunes? What level do you want? I know of several daily street driven 200+ hp, 300+ lb*ft, A4 TDI.
You want rpm? Stage 6 (appropriate injectors, exhaust, turbo, and that level of chip) allow 6k+ rpm. The owner gives these instructions: "Floor it, hold it there until the tach pegs, then count to three, and THEN shift."
Gotta love keyboard tuning.

As a side note: My bigger, heavier, mid-90's Passats returned 50+ mpg over the 200+k miles I had them, ran 9.2 0-60, 18.2 1/4 mile, 125 mph sea level (and a disappointing 109 at Bonneville altitude), did track days at Mosport, autocrossed to the best of my ability and had 900+ mile range (1300+ in the wagons), with stock tune.


If the choice of the Datsun is for aesthetic reasons, well, there's no disputing tastes. If the goals are more quantifiable (40+ mpg, 2200 rpm, 120 mph) there are better ways to achieve them.

its mostly aesthetics I love the Datsun 510 shape and I know how to make them handle. As far as power is concerned I'm not really looking to set any records with this but 100 hp will beat the gas engine by 10. I just want to open a few eyes to the fact that a diesel can be fun and still be cool. I am well aware that VW makes a better car than this but they start life as much as 150X the cost of this car. I paid $150 for this I figure if I hit $5k building this I will have paid too much for something in the swap.

I will have help doing this... My Father is a retired Diesel mechanic so I won't be allowed to cut corners or make mistakes.

A little background on LD swaps. This swap is more common among the Z crowd and those guys have seen 56mpg as a best and 40 as worst. I figured my car will weigh less than a Z and has less U-joints so it's a touch more efficient in the drivetrain. I will have a little less ultimate power but oh well.

this should be fun.


BTW the lazy comment was to say I don't see any reason to swap differentials since the 3.36 will suit my needs perfectly.

here is a chart showing RPM and speed in 5th gear using the following parameters:

tire: 205/50/15

Differential ratio: 3.36:1

transmission 5th gear ratio: 0.73:1

engine HP peak rpm: 4400

RPM 5th Gear
500 14
600 17
700 20
800 22
900 25
1000 28
1100 31
1200 34
1300 36
1400 39
1500 42
1600 45
1700 48
1800 50
1900 53
2000 56
2100 59
2200 62
2300 64
2400 67
2500 70
2600 73
2700 76
2800 78
2900 81
3000 84
3100 87
3200 90
3300 92
3400 95
3500 98
3600 101
3700 104
3800 106
3900 109
4000 112
4100 115
4200 118
4300 120
4400 123

just to be clear the LD20T has a torque peak @ 2400 RPM

What about the REAL 510s, with IRS?

I would have used a pl510 if I had one. I have had a few of the 68-73 510s. Something in me likes the refinment that this one has over the better handling IRS cars. The price was right and it looks pretty good if you ask me.

If that $150 was the entry cost, and you've a self-imposed $5k limit, you'll be OK.
Me personally? For a "3 squares" design I'd have located a VW Fox, more than likely a wagon (ok, the wagon was "2 box") I could then use bolt-in, no modification, VW and Audi parts. Say what you will about the cars, but the "Mr. PotatoHead" parts interchangeability of VWAG cars is a blessing for those of us that refuse to leave well enough alone.

For fun that doesn't have to be inefficient, I have an oily rag.
Well, it's mine, but I can use it only when Mrs. doesn't want it that day....

nice cabby. The interchangeability is what I like about Datsuns too. The LD20 is the same as an L 20 or L28 so I can use a 280ZX transmission and get the OD I want.