Engine performance

[Adam 83]

Every pay check I put a little more into my 1983 280zx. It has the same engine in it that it rolled out of the factory with. What I am looking for is advise on little things here and there that I can do to increase engine performance. I looked in the archives, but I could not find specifics for my question. Does anyone have a story or instruction on something they did to their engine that worked for them? I know this is a broad question, but its a start. I mean anything, from aftermarket O2 sensors to custom enhancements you came up with yourself. Any advise is appreciated.

[zbane]

Adam, this isn't a blow off answer, especially since people here have found ways to improve performance on the L28, but you will have better luck finding answers to this particular answer at hybridz.org

If it's been done, it's been done over there...

[Carl Beck]

Hi Adam83:

You would have to give us more to go on. Did you just rebuild this engine or does it have 120K + miles on it already?

For the sake of discussion - I'm going to talk about a stock engine, in an 83 280ZX with 95K miles, that has had good care..

The truth is that there is very little that one can add to that engine, that will increase its performance. If I were spending my money I'd do it in this order:

1. have a good engine shop do a fresh valve job, check the cam/followers to assure they are fine, relieve the valves, port match the intake/exhaust ports to the intake/exhaust manifolds.. do a mild milling on the head to raise the compression slightly...and reinstall. A good Z shop will know how much they can mill the head without going to far. Check the cam timing and made sure it is to spec.(might have to replace the timing chain and gears to get it near perfect).

2 open the stock exhaust pipe at the "Y" - into a 2.25" exhaust system with a turbo muffler at the rear.

3 Super Tune that engine - make sure the ignition system is fully up to spec., that the injectors are clean and delivering the proper amount of fuel, etc etc. Check the distributor function and timing curve.

Do the above and that car will run circles around the cars with lots of add no goodies - that do nothing more than waste your time.

FWIW,

Carl B.

[sblake01]

Great advice from Carl. Aftermarket O2 sensors? Do you understand the function of an O2 sensor? Don't get caught up in product claims. If you added up the HP from each of the items found in the local autoparts stores you'd probably end up with about 300-400 extra HP just from bolting them on! Of course, common sense should tell you that's not true. If every pay check you put a little more into your car, what do you spend it on? Other than gas/maintainence, the last time I spent money on my Z was to register it.

[ktm]

Other than gas/maintainence, the last time I spent money on my Z was to register it.

I wish this was my case.

[Adam 83]

The engine is stock with 178,000 miles on it. My biggest problems are fuel efficiency and back fire and sluggish performance. I replaced the mass airflow sensor, and that seemed to greatly improve the performance. The car doesn’t run as ruff at lower RPM's and when you step on the gas the car doesn’t stutter as much when climbing from low to high RPM's. It was recommended to me to replace the fuel pressure regulator because it is old and is most likely leaking. The spark plugs are getting fouled because of to much fuel. My mechanic hooked the car up to a machine (scope maybe?) that looked like a heart monitor. The signals from all the cylinders were in synch and lined up when the car was idling, but when the engine revved up they all fell out of synch. He believes the distributor is wobbling, so will have to replace that to. The spark plugs must be taken out and cleaned. The EGR valve is also suspect and old, so I will replace that to. I researched a bit, and some people say they just blocked it off with a plate. Is that the better route to take? I don’t know the advantages/disadvantages of doing that. If backfire is detonation of unburnt hydrocarbons in the exhaust, then most likely fixing my fuel problems will help with my back fire problems I think. (It likes to back fire on deceleration when in gear and after the car gets warm). The cat is gone, and replaced by all new pipe to the muffler (same diameter as the stock pipe). These are my problems that I will be fixing over the next few paychecks. Advice?

Even after these new parts are put on, the only way I think I will significantly improve performance is to have the engine rebuilt. So, my next question is what is the cheapest/ performance-effective route to take on this matter? Getting a rebuild, buying a crate engine (do they even make a crate L28?) or following Mr. Carls advise:

"1. have a good engine shop do a fresh valve job, check the cam/followers to assure they are fine, relieve the valves, port match the intake/exhaust ports to the intake/exhaust manifolds.. do a mild milling on the head to raise the compression slightly...and reinstall. A good Z shop will know how much they can mill the head without going to far. Check the cam timing and made sure it is to spec.(might have to replace the timing chain and gears to get it near perfect)." -Carl Beck (forgive me, I havnt quite figured out the qoute option).

Thank you guys for all your help

[m4xwellmurd3r]

I wouldn't do a head rebuild unless you do a bottom end rebuild as well.

Have you cleaned up all the connections? if it's fouling plugs from running rich, I would suspect corrosion on the water temp sensor at the plug or at the connectors for the plug (about a foot from the plug itself)

I would also check the fuel pressure before you go and replace the regulator.

if you do a rebuild, I would do it myself. Saves on money and it's a great learning experience (if you do it yourself)

As far as making power, to make bigger power out of the stock engine, you really needa open up that head and make it breath. Stock they're not to hot, but you can get some decent flow numbers by doing a good port/polish job. and a new intake manifold is a MUST

[Adam 83]

Alright, I forgot to mention, when the O2 sensor is unplugged the emissions tester (the one you stick into the tail pipe) read around 400 hydrocarbons ( I forget the exact units of measurment). When the O2 sensor is put back into the exhaust manifold, the hydrocarbons jump back up to around 2000. So as of now, I am running the car with the O2 unplugged.

I understand I will not get a race engine out of my L28. I just want to know how to make it perform as close or better than when it rolled out of the factory. I want to do this but I am pretty low income right now, so I thought Id ask those who have experiance, and accomplish what I want in the most cost effective manor. The problems I have listed here are my main challenges, and being only a beginer at auto mechanics I am not always what approach or perspective to take, so I really appreciate the help.

So, when I check the water temperature sensor connections, or any connections for that matter, is corrosion always visible?

[zbane]

So, when I check the water temperature sensor connections, or any connections for that matter, is corrosion always visible?

Not always. If there is corrosion, it is usually a white or green residue. It would be best to go from connection to connection and clean them all, then apply some dielectric grease (available at most all parts stores). The function of the grease is to improve conductivity and slow/prevent future corrosion. You may find that some of your connectors have become rather fragile, and they will break. Stephen did a great write up on replacing the FI connectors; I just searched for it but couldn't find it (perhaps he will post the link).

[sblake01]

IIRC, that thread wasn't my thread nor about changing the connectors. It just showed the difference between the original Nissan connectors and the BMW connectors. I have since switched to Volvo connectors because I like them a little more. I could find that thread if you want but it contained a bunch of questions and side bar remarks from our beloved Tomo and a little ranting from another member because he sells replacement connectors that are the same as the OEM Nissans and my responses kind of stepped on his toes.

[Bruce Palmer]

Everything else aside, a compression test would tell you just how tired that engine is. If for example compression is down say 40% from new, then a rebuild should yield some major bang for your buck. Hanging go fast parts on a tired old motor is, how would one say it, counter productive. Start with the basics and build from there.

[Adam 83]

Im on my way out the door to borrow my friends compression tester. I wonder what I shall find. Will generice vaccum tubing be fine if I replace the vaccuum tubes on the engine? Oh, what did you guys think about my O2 sensor problem? Is it bad or dangerous to just leave it out like that?