Learning about the Z31 Turbo

I own a 1985 Z31 Turbo (5 speed manual / around 180,000 miles on it) which I am very pleased with. I've had it less than a year, and now that I'm out of school, I'd like to learn as much as I can about the car and get to work on improving it. I know that's very broad...

I also know this is a lot to read...but I hope someone with more knowledge than I will take the time.

A little about the car first:
As far as I know, it's mostly stock. The air conditioner was replaced with a newer kind, and a few other things were retrofitted by Nissan. It has an aftermarket air intake, a GReddy Blowoff valve (type s), and as far as I can tell, the stock turbo running 3-5 psi (I need to replace that stock gauge some time).

I really don't know too much about these cars, so I ordered all the z31 books that were on Amazon. I was wondering if anyone has any good book reccommendations for cars in general? (note, I know how engines work, how my turbo works, all the basics)

Now to the 'problems':
1. The handbrake sticks. Back right rotor is warped from the sticking. You can drive around for a good 20 minutes with the handbrake being released and it still will hold you on a low grade hill. So I park in gear and leave the brake off (and use a brick as a block at my house).

2. The car runs about a centimeter below the top notch on the temp. gauge. Oil temp. seems fine. The other day when I parked I noticed the coolant reservoir was boiling. Didn't see any leaks, and there is the right amount of coolant, but the radiator light comes on for about the first 5 minutes of driving. Radiator cap was replaced, and radiator was flushed according to records.

3. Turbo seems inconsistent. I've got a manual boost controller, not the cheap bleeder kind. Some times, I'll be driving around and ease onto the gas down to the floor and the car will go from 2.5krpms to 5krpms in a very few seconds. No tire spin, nothing unusual with the boost by my gauges. Other times, it feels like the turbo never even kicks in.

4. The car has a lot of trouble starting when it is hot. Let's say I've been driving around for 30 minutes. The temp. gauge is now pretty high, but it won't go any higher. So I turn off the car, and come back to start it. If it hasn't been long enough for the car to cool off to about the middle range of the temp. gauge, it doesn't want to start. It sounds really bad when you get it to finally run. Hard to describe, but it seems like it's misfiring and it makes a bad popping noise every now and then ( like the side of a tin can being bent in and out ). When I get the rpm's above 2k, it still feels rough, but I can get the car to move. The rpms drop considerably when I put it in gear, and I have to carefully get it driving at around 2krpms to keep it from stalling out. Once I do start driving, the problem immediately dissappears. No issues when the car is cold, though it's been getting a little harder to start recently; plugs probably fouled out from all that bad starting when it's hot.

Aside from other minor issues, these are the problems I really want to resolve right away, if that's possible, with the overheating being the problem of primary conconcern.

On a final note, I don't know what kind of plugs to get. I've been reccommended to buy NGK iridium plugs that are a little colder than the stock plugs (no idea what the stock plugs are). And what kind of plug wires?

One more thing: since I'm working on upgrading the car, exhaust seems to be the first thing to start with. It currently has the stock exhaust except for a flowmaster 40 muffler which sounds very nice, but I don't think it helps performance any. What should I look at getting, and what should I avoid?

Thank-you very, very much for reading : P

whew alright... well after reading through that ESSAY i think we can help :p

now for your handbrake sticking problem, i had the same thing when i first got the car... i found spraying down the spring/clasp assembly and hitting it with a heavy blunt object free'd it up to the point where i could spin the rotor freely with the ebrake disenguaged.

as for the temperature problem, i would completely flush the coolant immediately. sounds like you've got a bubble in the system or something, but running that hot is definitely not good for the engine.

for the turbo issue, maybe your wastegate is starting to stick open.. time for a new and bigger turbo:D not sure how to fix the wastegate if that is what's causing it.. you say you have a bov, have you blocked the stock popoff valve? if so that might be causing some boost issues if it is sticking as well.

as for the hot starts, it should go away after you stop it from running so hot:p

what is your manual boost controller set at?

Time for my essay...:p

you say you have a bov, have you blocked the stock popoff valve?

If by "popoff valve", you mean "blow off valve", Z31s don't have blow off valves stock. The Z31 is damn near the simplest turbo system you could ever imagine. No intercooler...no twin turbo or sequential set up...no blow off or recirculation valves...just a turbo...that's it. Just a little FYI. :biggrin:

About the overheating/coolant problem, check your radiator. Doesn't sound like it's cooling the coolant...like it's blocked up or something...like the coolant isn't even going through it at all. You might just have to go through the entire system piece by piece. COMPLETELY flush the system...change all your hoses...check your thermostat...all of it. Something's definately not working suffeciently and no where NEAR up to factory spec.

As for mods...you said you already had an intake, so go straight to the next step...

Get a 3" MANDREL bent (must be mandrel bent...smooth bends...) exhaust system. That'd open up your exhaust nicely. Get a custom 3" mandrel system...keep it as straight as possible...take the cat out if you don't legally need it where you are (or gut it if you do...a broom stick will hollow it out easily... :wink: ) and get rid of the muffler all together. Don't need it with a turbo. The turbo quiets the exhaust plenty. That should only run you 200-300 bucks.

That, the intake and boost controller will put you in the running with the 350Z and the such...somewhere in the mid 5 second range 0-60 with 15psi. Do NOT go over that though and do NOT run that for an extended period of time, without having the highest octane gas you can get your mits on (preferrably 101 octane race gas), and never on very hot days. Your turbo is fine at this boost level for short times, but only on cool days and with VERY high octane gas. After 15 psi, the turbo produces more heat than anything else...heat is bad. Before a race, turn the boost up and turn it back down after the race. You can safely run 12 psi consistantly, but I'd keep it to 10 psi around town...no need to go overkill around town.

Oh...and get a quality aftermarket boost gauge that's measured in PSI. The stock gauge isn't very accurate cuz it's REALLY hard to read. It's measured in mmHg (millimeters of mercury) and there aren't really any tick marks or anything on it...very vague. A good boost gauge SHOULD have been purchased with (or even BEFORE) the boost controller...they aren't expensive and I'll help you put it in if you need help. This is now priority #2 behind the coolant issue. I'd turn my boost controller down to stock levels until this is completed if I were you.

You should ALWAYS be running premium fuel anyway since you're running forced induction...I shouldn't even need to say that, should I.......

The e-brake just sounds out of adjustment. Smack the shit out of it...don't waste your time messing with it.

If you need any more help with your car or need to find some parts, send me an e-mail. I can find pretty much anything you could want.

fyi:The blow off valve was welded on very carefully by the previous owner. It bypasses the original setup. And I do buy premium fuel.

I was talking to a local guy about the car, and he said the stock turbo isn't very good; he reccommended getting a ct 22 or 28 or something like that...should have written it down, but it was late at night.

I've been looking at exhaust packages, and I'm pretty clueless what to avoid and what to regard as worthwhile. Certified Muffler sells a stainless steel downpipe for 215 and a catless turboback exhaust for 735 (also stainless steel). A friend told me that's way overpriced. A few other friends said it's expensive but worth it. I have no clue. I do know I want a 3 inch exhaust without a cat or muffler that sounds comparable to the current setup which I adore: stock except for the flowmaster 40 muffler. It has a very nice, mid to low rumble, with a slight growl under accel. I def. don't want one of those hornet fart cans or any kind of buzzing noise. I'm looking for performance and sound. Any reccommendations? Note...it has to fit the car, I only know how to bolt on currently ( unless you want to teach me something more complicated; I'll buy you pizza : P)

I really don't know much about brands at all. I just look at what the people with the really nice wrx's and such have in their cars and assume they are good parts.

One last thing - I bought a new thermostat, but haven't installed it yet; waiting on the arrival of my instruction manuals (haynes and such). Any tips or info on how to change the thermostat?

Thankya very much! My Z appreciates your help :)

Oh yea, manual boost controller is set so that my gague reads between 3-5 psi; no markings on the manual boost controller, so I just read it off the gauge under full boost...yes, I plan on replacing that wretched stock gauge when I get the car running cooler : )

ack you're right, sorry i must have been daydreaming or something... i think it was the l28et or something, not too sure, it was late when i read it.

anyway, for $735 you should be getting a full stainless exhaust from the turbo back and a blowjob, that is ridiculously expensive. stock turbo is good for most people until you start wanting more than 300ish whp.

as for making an exhaust, you can get a shop to do it for you most of the time. i'm not sure where you're located, but if it's a bigger city, you probably won't have a hard time finding a shop that does mandrel bending for you. just ask them to make it the straightest design possible, 3 inch mandrel bent stainless steel (prefferably 304.) with the turbo, it will be hard to find a muffler that will give it that buzzy sound, as the 3 litre v6 seems to give off a nice sound no matter what you throw at it.

not sure about the thermostat, never had to do it yet (lucky me)

for the exhaust, even a small town exhaust shop can order you the parts you need mandrel bent from a bigger supplier and they will ship it to the exhaust shop.

what sucks about the stock exaust of the Z31 is that it curls up over the rear end and sub frame...which puts a hefty bend that restricts the exhaust flow. it also doesnt help that it is about a 1 1/2" wide...

so basically a straight through designed 3" mandrel bent is gonna up gobs of power, expeically when you start boosting a little more and get more modifications.

and yes that exhaust for $735 is way over priced...you could call up Greddy and pay them to design you a custom exhaust for that price. JEEZ... :lol:

so what is that object screwed into the side of my intake on the front if its not a blow off or pop off???? just a spring thing that doesnt allow pressure to build to high thingy????
not a pop off or blow off was his terminology not proper???
what is it called then i heard it referd to as both sio then you take a shot at it then

so what is that object screwed into the side of my intake on the front if its not a blow off or pop off???? just a spring thing that doesnt allow pressure to build to high thingy????
not a pop off or blow off was his terminology not proper???
what is it called then i heard it referd to as both sio then you take a shot at it then

um...maybe a wastegate actuator solenoid???

i went to this performance shop this weekend called A-Spec tuning and seen this 3rd gen rx-7 running about 350hp with a 4 inch exhaust it was pretty sick looking ..

so what is that object screwed into the side of my intake on the front if its not a blow off or pop off???? just a spring thing that doesnt allow pressure to build to high thingy????
not a pop off or blow off was his terminology not proper???
what is it called then i heard it referd to as both sio then you take a shot at it then

It's just a relief valve...not a blow off/pop off/recirculation valve.

700-something for an exhaust is RE-GOD-DAMN-DICULOUS. Find a shop that'll make you a custom mandrel bent one and they shouldn't charge more than 300-350 bucks.700-whatever you said is just retarded, dude...don't do that...

The stock turbo is a plenty decent turbo. Spools reasonably quickly...no, it's not limitless, but no turbo is...it's plenty good unless you're gunna rebuild the engine...like me...:biggrin:

isnt a releif valve the same only its after the throttle bodit instead of before long live the z just jumped on his case and said they dont have one i was just sticking up for him

I didn't jump and anyone...I was just sayin... :screwy: The factory service manual (the bible) for the 88 Z31 calls it exactly that...a relief valve. I'm just here to educate...not jump on anyone's case.

Relief Valve == Pop-off valve
Pop-off valves are designed to stop damage to your engine (in case the stock wastegate stops working) and sits on the intake plenum.
Blow-off valves are designed to go off every time you close the throttle so that the turbo keeps spinning and you don't get boost spikes. They sit before your throttle-bodies. Same basic design but different purposes.

Provided everything is working like it should, your pop-off valve should never do anything, its just a failsafe in case your turbo's wastegate shits itself to prevent your engine from doing the same.

-Mike

ok anyway like was stated 3" manderal all the way back split it into 2 seperate 2 1\2" fart can tips and call it good (slight baffling ability as i stated 3" straights is loud as sin), put on a good intake(3"cone) and do an extensive tune up(ie plugs, wires, cap, rotor, check timing(recomend belt replacement), oil change to synthetic might help (youll want to change it till its clear), oil cooler prior to the turbo, a radiator flushing and replace the mechanicle fan with an electric and a new water pump could always help, try and remove all brakeing equipment in the rear and make it work freely and reassemble with antiseize in all friction points (higher melting rate than that of almost any high temp grease)..... and as for the inconsistance turbo perhaps try removeing the actuator rod and see if the gate opens freely .. also try and remove the intake piping and check the axes for free play, maybe its just had to many impeler stops allthough if theres a bov i dont think that would be a problem also the boost doent kick in on a totaly stock unit untill about 2700 (doubt thats the case ) and on a exhaust intake and exetra on a stock turbop i could get positive boost under 1800 rpms too quick to know if it was full boost though it was hella fast and i tried to drive it niucely all the time as iun if over 4000 rpms it was to the floor never tried to lug it (floor it at 55 in 5th) just drove it like i thought it should be driven sorta deals
well any way maybe try and take off the intake oil line and flush out the thrusrt bearing it may justy be so sluged from overheatiung that it is sluged or you may need a new bearing

ok if you stuck through it i hopoe you werent as confused as everyone else who tries to read it
i tend to confuse people as i stated before it seems as though i got add (not clinicly proven) and my mind thinks of things before the last thought is doen so sorry for making you a little stupider and your welcome if you learned anything

all i can say is good luck and hears anothe r esay for you to read

.......
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i counted that many punctuation marks. its definitely getting better, but we need some punctuation when you are NOT listing things also.

i counted that many punctuation marks. its definitely getting better, but we need some punctuation when you are NOT listing things also.

bored huh? :tongue:

-Mike

bored huh? :tongue:

-Mike

yeah, i was gonna go through and fix it all for him but i didnt have that much time. :lol:

sorry my comp only sorta does the write down deal if i try and go back and correct it it just overwrites what is there instead of pushing it alnong. also that has been my problem since i was a kid, you dont even know how many essays i faild for that problem. but anyway ill try harder and harder till i get it right .

sorry my comp only sorta does the write down deal if i try and go back and correct it it just overwrites what is there instead of pushing it alnong. also that has been my problem since i was a kid, you dont even know how many essays i faild for that problem. but anyway ill try harder and harder till i get it right .

thank you...

if you push the insert button on the keyboard it will allow you to insert whatever you want, wherever you want. hence, the name "Insert" on the keyboard. just delete what got screwed up and then start typing it over again.

oh, no doubt. i didn't know that. thats sweet deals. but back to the nature at hand, did you get any of that straightened out yet?? most importantly the over heating??
also the boost, could that be the boost controller is sticking or jamming??? is it a home made spring and ball bearing type?? try that also, that could be the whole boost problem. good luck