Lost 25 Horses From 77/78 ZX
 

I just got this 81 ZX last week, no previous Z Car experience. I read that the 77/78 has 170 horsepower while the 81 has only 145 horsepower. How can I get them back? I suspect that its largely in the computer, but I don't really know.

Thanks,
John

That is largly in the drivetrain.

Both engines are the same. Basically the same head/block from 75-80 with just a small difference the first two years (75-76) in the exhaust port design. All have 170 flywheel horsepower but later on (1979) Nissan had to stamp on the wheel horsepower of 135.

In 1981 the engine gained a new combustion chamber design and flat top pistons with just a tiny bit more compression. This bumped the torque and horsepower up by 10 at the wheels.

There were additional emissions equipment put on some engines starting in 77 and then again in '79 or 80, but the claimed horsepower is the same. But did the actual horsepower decline? ...I'm not sure.

While some say the 280zx is much slower due to weight, the early 79 280zx's dry weight (according to Nissan's FSM) is about 40 lbs less than the dry weight of a 78 280Z. :eek:
Once all the power steering, power windows, t-tops ect came into play... well, the 280ZX was up to about 3000+ lbs. The 2+2 models added only 180lbs.

Thanks, it does seem that the engines are basically the same and the slight boost in compression ratio should increase rather than decrease the HP. As I recall, the 1981 has a tad more than the 79/80.

I know the ZX creature comforts added a lot of unnecessary weight with features that to me seem like "foo-foo."

The 81 ZX was not my first choice, but its what I've got and I plan to increase the performance the best I can afford. I've had to re-bush the gear shift and fix some electrical problems, but hey, its 22 years old and I only paid a grand. I'm happy, but do want to up the power a bit.

Again, thanks,
John

Larger throttle body :)

They say the throttle body is the most restrictive part of the engine.

The major difference in the power numbers is the change from gross horsepower to net horsepower. Gross horsepower was used on the earlier Zs and with the ZX, Nissan made the change to quoting Net horsepower. The 79 & 80 suffer power loss from a restrictive catalytic converter which was also remedied in 1981 or 1982. Bigger power gains will come from upgraded exhaust with high flow CAT then you will get from just adding a throttle body. Add both with higher flow filter and its a good start to more power.

From the looks of it, the air flow meter's square hole is about the same size if not smaller than the factory throttle body. also, the metal on the intake manifold is not larger than the factory throttle body.

Adding on a larger throttle body (like I did) and doing nothing else (like I did) seems like it will only increase throttle sensativety but ultimatly not increase your peak horsepower by much at all. (if any at all) It feels faster untill you're at wide open throttle. That's my driving impression... waste of $200 too for the MSA unit which is sticky even after all these years. I'd recomend the '89-90 240SX throttle by far. I hear its nice and smooth and never sticks.

A larger air flow meter, large throttle body, K&N air filter and new intake tubing to connect it all to a ported intake manifold would be the way to go.

Thanks to all for your help, looks like I have a lot to learn but that's part of the fun with a project car.

John