....i would add a ground wire from AFM to engine, use one of the four bolts on the AFM.
....you might eventually want to try a AFM blow-through set up if you can fit it...it idled and reved much better.

well, i know its not ground because it works beatifully with the maxima AFM. i may try blow through down the line. i was of the understanding that they run worse that way tho. worth j try i suppose. anyhoo, heres another video clip for yall. i cant get over the sounds this thing makes lol

My blow through has/had perfect idle, perfect startups, no off-throttle stumbling or any issues at all

well, im going on a weekend trip with the family this weekend. maybe next week ill have time to try it blow thru and see how it behaves. thanks Mike and James both for the advice.

Attachment 13813

got a larger fan installed. wired this as primary and the one up front is wired to temp switch #2 so its more like a back up fan. so my coolant temps are stable again.

if your having stumbling issues look for loose/missing grounds and vacuum leaks. those old wiring harness are notorious for having one to many grounds.

you'll be ok with blow through. the older MAFs were built a little tougher.

well...I changed my set up to blow through today...it runs like crap in basically every way except under boost. ive been running 10psi with an atmoshperic blow off valve and the apexi beo preventing stall. had zero issues except the stumble that i believe to be the MAF. i had stable idle, good cruise AFRs and 9.8 AFR under boost. now that its blow through, im idling at 10:1and it runs like crap from 750-2000 rpms and doesnt want to rev, it wants to die. 2000-3000 cruise gives me 18:1 AFR and under boost at 10psi im seeing high 11s AFR. not nice safe 10s. so......in short, screw blow through. way worse on my car. im putting it back the way i had it tomorrow and ill get a new MAF when i can afford one.

you know you still have to move all the vacuum lines in front of the maf....

yeah, i did. unfortunately not all setups are the same. maybe it has to do with my intercooler flow and plumbing, who knows. all i do know it it did not work well for me. i put it back the way i had it this morning except with a 3"cold side charge pipe instead of the 2.5" one i was running before. AFRs are normal again. also, i used damn near a whole can of MAF cleaner on my sensor. 3rd time ive cleaned it. stutter is just about gone. it was just a bunch of build up aparently. it was a junkyard part after all. also, i found my boost limit this morning. i cant go over 10 psi without some additional fuel or ignition changes. i tried both 12 and 13 psi. 13 psi lost traction at 70mph, which was pretty wicked. but i heard a little spark knock so i let and and turned it down to 12. still got a hint of spark knock at 12 so im back at 10 now. im wondering if i need to bring my base timing down to 12 or 13 degrees. its currently at 15, but thats base timing for the factory turbo motor with 7.8 compression so....

Do you have any pictures of how you had it setup when you tried blow-through?

You need the MAF on a straight section of pipe without any curves immediately prior to the MAF. If you had positioned the MAF immediately after a bend or something that would almost certainly give you issues because it makes the air very turbulent entering the MAF.

....that sucks..i,d also liked to have seen some pixs of the blow thru set-up before it shat the bed...frustrating when gremlins show up, but it was probably something simple.

sorry guys, i didnt get any pics of the blow thru setup, but it had 12 inches of straight pipe in front of the maf and almost 6 behind it. had it between the intercooler and the throttle. no matter, like i said before not all setups run the same. not a big deal, mine just runs better draw thru.

so on another note, since ive been running 10psi, i started to get spark blow out at high rpms and i blew out the exhaust manifold gasket on the rear manifold. today i replaced the rear manifold gasket and used copper coat on it this time. i also replaced the plugs one heat range colder. running NGK bcpr7es-11, gapped them at .030. no more spark blow out and the car almost runs normal out of boost now, very little hesitation at the bottom. also, i had previously set base timing at 15btdc, i guess i did something wrong 6 months ago when i did it with the maxima computer installed. i checked it again since i heard that spark knock the other day and base timing was at 22btdc! no wonder it pinged! so i pulled it back to 15btdc. im also gonna run some decarb thru the motor to try and get any carbon buildup off the pistons. im doing all i can right now to prevent detonation. i think i lost a tiny bit of power with the timing change, i may try running it at 17btdc tomorrow and feel it out. ive got the boost at 11psi now and it feels crisp, AFRs are good and no ping. i do however think im running out of injector so to speak. i think 11 is where ill be at for a while, my math tells me i dont have enough cc to attain the 15psi id like to see. ill need something in the 300cc area. anyway, its scary fast in such an outdated chassis, so its fun for now. ill keep making little improvents until i can get some bigger injectors. and of course ill keep the thread updated with changes and photos/videos.

i ran mine for a while blow through. and the only thing that gave me issues was the bov. outside of that...intercooler, fuel psi at 45, 91 gas. ran for a coupple years before i went different direction....

how much boost pressure were you running?

...pretty much same results for me with blow thru...i use 93 octane....22 degrees initial timing...15psi.....meth injection with M2 nozzle....never ever pings..nasty little car at 2800 lbs....only issue blow thru is the 300zx AFM will lift up the plastic "lid" under higher boost, but solved with some proper adhesive and clamp.

just throwing out some missing pics from missing updates. car is finally street legat again lol. got almost 300 miles on the build now and am boosting just under 13psi.

BOV mounted up between intercoller and throttle.

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idle control valve and cold start valves installed, uses a ford ecoboost check valve to keep boost from leaking back to the turbo inlet. used on a factory 16psi system so im sure itll hold.
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heres the colder NGKs im running if anyone wants the part number
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and a couple of photo shoot style shots, cuz ya know, race car haha!
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im hoping to get it on a dyno once i get to 15psi, that way i can safely see how much timing the car can handle and make some tweaks to the fuel curve with the apexi neo to maximize power and see what kind of numbers i can put down. eventually id like to make a run at little river(local 1/4 mile trip) and see what i can trap with it. its an hour from home so i wanna arrange a trailer as backup in case i blow the trans. i understand that to be the weakest point of my build. we'll see how it all holds up.

....very nice job.....i,d love to pick up a wagon version of the Maxima and do the same.

I ran blow thru a long time never had any issues. Not even the blowing cap/lid off and I was at 27-30psi

what size injectors were you running???

im on 1000cc now previously ran 370cc stock intake and 450cc when did top feed conversionm

ok, good to know. does anyone know what my limit is gonna be with the 259cc injectors im using? i didnt think theyd get me over 8-9psi, but im pushing 12psi now with low 10 AFRs, im wondering what ill need to get to 15psi.

I have z31 so pretty familiar with your setup. 14psi seems to be about the limit on stock fuelling. Biggest thing with z31 turbos is the ceramic wheel they don't like over 14psi before the tend to grenade. Just watch your afr 12-15 should be doable with 260cc. Also keep in mind the stock fpr is 1:1 rising rate so your flowing closer to 300cc injectors at 12 psi. Should put down 250ish stock fuel setup.

running 13psi solid now. AFRs still good. starting to get clutch slippage on the freeway now. clutch only has around 5,000 miles on it, but its an OE replacement from aftermarket. i believe theyre only rated to 220 torque, which i believe im well over at this point. time to start shopping clutches now....

...stock 1986 300zx turbo 260cc Injectors...top feed style...performance fuel pump...meth injection

alright more changes, fixes and updates. first up, i relocated my apexi neo where i can see and adjust it better. feels like a cockpit in here.
Attachment 13700

im looking at digital thermometers with external temp probes so i can install it in my charge pipe. i want tk be able to monitor charge temps since ive upped the boost. im now set at 13.5 psi and fueling still looks good. pulling the base timing back to 17 along with the colder plugs seems to be keepin detonation at bay, so im working on heat management now to keep it that way. working on all the little details to reduce temps. first off i finally moved that damn coolant hard line from the radiator that was touching my inlet tube and my turbo hot side pipe, because that was definately not good for heat containment lol.
Attachment 13701
Attachment 13702
the solution was right in front of me the whole time. i just took out the hard pipe and splice the factory upper/lower hoses for that side with a coupler at a different angle and now the hose perfectly misses the charge tube, goes under the inlet tube, around the belts and straight up into the water outlet. almost like it was meant to be haha!

i also re-purposed a cold air intake box from a compact pickup the isolate the air filter so the turbo can only draw air from inside the fender. which is fed from a large opening directly under the car. it took a lot of love with my tin snips and still isnt perfect, but its functional and looks decent. ill be tidying that up over the next few days.
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still shopping clutches in the meantime, not sure what i wanna get yet. 421 miles on the build now, nothing blown up yet. fingers crossed.

heres a quick example of the clutch slippage in high gear. was in over drive and gave 20% throttle exactly, i watched it on the fuel controller. if you watch the tach and listen for the spool, youll see around 3100 rpms it shoots up to 4100 rpms and then drops back down to about 3800rpms once it grabs again. its only an issue in a high gear/load situation, but a problem that needs sorting nonetheless.


as you all can imagine, its much worse if i punch it on 5th gear lol. i understand this clutch is rated around 230lbft of torque, i guess im making decent power if its slipping with such small throttle input.

swapped ecus today. im quite surprised at how many of my problems have been coming from that damn old computer i had. turns out it was an 84 computer, not an 86 as i had thought. im now running a 1988 300zx turbo 5speed, federal computer. car starts much more easily, still doesnt idle perfect but thats because its expecting a pwm idle valve. idle afr is almost always 14.5 and sometimes goes up to 16. used used to bounce back and forth a ton between 14 and 19 and idle like poop. also, that stupid stumble is had is GONE! it has a better timing curve. so now 9 psi feels as good as it did at 13psi on the old computer.

84-86 ecus are low imedance the 88 ecu is a high impedance. What impedance injectors you have?

i have high impedance 260cc out of (95?) maxima, side feed. i had read and was told high impedance is fine with low impedance computer, but thats clearly not the case lol. i think its a big reason i had so much trouble before. im strongly considering installing this 88 turbo PROM into my 88 maxima computer. that way ill have properly funtioning idle controls and ill be able to run closed loop since the maxima board can read a zirconia 02 sensor. i can use the output from the wideband and have very accurated closed loop feedback that way. this is kind of a stop gap measure since nistune is financially so far out of reach right now. i really want some 370 injectors and 14 psi, but again, cant do that without nistune :/

Yes you can run high impedance injectors on a low impedance ecu people do it I personally would never do it. When you get ready do 370cc Ill sell you my set dirt cheap in 3rd gen rail. There type 1 z32 TT injectors. If your running just a z31 t3 the 260cc should support all that the z31 t3 will handle with that ceramic compressor.

so.....made it to 1000 miles on the build and finally had a serious failure. time to make some changes. my fuel injectors maxed out and got stuck open. my own fault really. 13psi freeway pull with VERY hot oitside temperatures. long story short, flooded the intake runners and smoked the catalytic converter. and i meam SMOKED the converter. so im dithcing the converter, gonna get a new set of 260 injectors(ebay, $60) and an electronic boost controller so i can set this puppy at 10psi and lock it down there. the car makes very good power at 10psi, it also doesnt produce as much heat from the charge air, the injectors will be around 90% duty and the trans wont be that far over its capacity. i had to take a long hard look at my goals gor this project and the funds and u can spend to do it. im getting a small welder and redoing my exhaust entirely. my 2.5 down pipe is currently choking into 1.75 flange and cat and maintains 1.75 until the 2.5 muffler at the back. im gonna run my 2.5 down pipe straight 2.5 to a magnaglow style mid muffler, then bump to 3 and run 3 inch all the way back. i dont believe ill run any additional mufflers. im also ditching the front mount intercooler and setting up a top mount with a scoop so i can get some damn airflow into the intercooler amd reduce charge piping. will also plumb back my blow off valve. lastly, will be redoing the turbo inlet so that i can reinstall air conditioning.

not much to report just yet. have been rounding up compnentents for the revamp. finally got a new speedo cable and installed it. pulled the green domes out of the instument cluster and installed red LEDs so the cluster matches my other gauges. also, alcohol rubbed the green off the back of the AC control panel display and painted the back red, also painted the bulb behind it red. so everything now matches inside the car. i bought a small scoop to install in the hood for the top mount, top mount unit is already sitting in the garage. i believe i have all the pipe i need for the exhaust system upgrade and i purchased a small 110 flux wire machine, pipe cutter and pipe expander set. so ill be working on the exhaust soon.

Attachment 13437

heres the little welder i bought. im used to using a mig at my old job so this is taking a little getting used to, but it welds quite well.

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red gauges.

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AC panel, didnt come out quite like i hoped it would, but it matches the rest so im happy with it.

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the cluster had little green domes in it the had to come out.

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got a little chain cutter to help out the exhaust work.

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and of course this expander set is a neccesity.


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a bunch of pipe to work with for the exhaust mods.

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and lastly, a little test fitting to see how the scoop will look :)

got all the interior yrim back in today and found that the voltage and rpm on my cluster are out of whack, so i gotta pull the back apart. grrrr.....oh well. part of the territory i guess. also spend a few hours working on the exhaust. mid pipe is done and muffler is mounted working on connecting them now. decided to only got with one muffler also.

Attachment 13064

this is the temp gauge i installed to monitor charge temps.

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midpipe is finished. i also had to extend the downpipe and put in a larger flex section. got a new O2 bung and installed the wideband.

Attachment 13066

this is the beginning of the "s" at the rear where it transitions from 2.5 to 3 inch.

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heres the old muffler on the left and the new one on the right. dual 3 inch tips and very little fiber glass packing ;)

Attachment 13068

and lastly, a little teaser of how the tips look. more to come soon!!!

just a quick sound check on the exhaust.

exhaust system is finally done. took it for a drive to let it all kinda settle in. heres what the idle sounds like

well, i drove it for the first time in a while. my charge temp gauge works. kinda hard to read at a glance but functional and was super cheap so i cant complain. ALL of my gauges are inaccurate so ive gotta open the cluster again and adjust the needles. but i do have a working speedo again so thats nice. in regards to the new exhaust, i decided against the mid muffler and am running straight pipe up until the 3" ebay muffler at the back. its not too too loud which is good. it does pop quite a bit on decel, but i enjoy it. it really helps the turbo breathe tho. the accelleration at 10psi is ridiculous and 1st and 2nd gear no longer have traction at all. its delightful.

fixed the speedo and did some road testing today. had to be easy on 1st and 2nd gear to avoid wheel spin, but for what it is i feel its running pretty quick.

finally runnimg again. little weak pull at 7psi