Diesel in a white suit

[Philip1]

I'm working on the details before I start but I'm planning an engine swap in an older Datsun.

Goal: 40+mpg and good performance

Planned engine: Nissan SD22 with a turbo added

Planned transmission: SD22 5-speed

Differential ratio: 3.36:1

Project chassis: 1981 Datsun 510 2 door sedan

Photos below:

[theholycow]

I like those wheels.

The car's pretty clean, do you have interior photos?

Do you have specifications on any of this stuff? Curb weight, power from that engine (NA and/or guessed with the turbo), gear ratios?

[Philip1]

the SD22 in N/A form is a bit weak
61hp @4000rpm 104 lb/ft torque @1800 rpm

turbo charged with intercooler Dyno tests show

109hp @4000 rpm and 133 LB/FT torque @1800 rpm

the transmission internally is the same ratios as all nissan 5-speeds except for 5th that is a taller .8125:1 overdrive

the car already has 3.36:1 gears in it so this is looking like a marriage made in Japan.

curb weight for this car is about 2200 Lbs the diesel will probably add 1-200 lbs to that with trans and all

the interior is as clean as the exterior but I don't have any photos

I want this car to be a statement that fun doesn't have to be inefficient

[theholycow]

That torque sounds great. I bet you could enjoy a singificantly taller gear. If the tires are the same outside diameter as stock, you're looking at 2750RPM at 70mph...that's above your peak torque and that diesel should probably be running far lower RPM.

Calculations by http://f-body.org/gears

[Philip1]

good thing I drive 60-65 everywhere I could swap the guts from a 280zx 5-speed they have a .73 5th. That would give a nice 2200 RPM 60 mph. The 3.36 gears are the tallest Nissan offered for this housing. Economically that's as good as I can get. I could swap the H190 out of the truck the SD22 comes in for a 3.16:1 ratio but that involves brackets and cutting tubes and all that fun. I am by nature a bit lazy and I think the 3.36 will do. I should also change up to the 205/50/15 tires to have the correct diameter that would bump my cruise at 2200rpm to 62 mph

[theholycow]

I don't know much about diesel FE, but I'd guess that you want to be much further from your peak torque for cruising.

[Philip1]

just found out the SD22 Transmission has the .73 5th gear so that's good news.
2200rpm 5th gear equals 60 mph with 195/50/15 or 62 mph with 205/50/15 with this overdrive.

[Philip1]

you know more than me but what I've seen these Nissan diesels like to cruise at peak torque. interesting side note is if the engine could pull to the governed 4400 rpm it would go 121 mph... Thats better than the stock engine could ever do.

[theholycow]

I double I know more about diesels than you do.

Remember that peak torque RPM is only producing peak torque with the go-pedal on the floor, so we're talking RPM but not power production. If you're producing 193 lb-ft while cruising, you're probably cruising at 160mph.

Anyway, you may be right, diesels might be most efficient at/near the same RPM as they produce peak torque.

[Philip1]

ah yes but peak torque is also peak efficiency or I think it is.... I guess I'll find out.