Righto I have a few things i would like some answers to. Sorry if i ask things that have been brought up in the past but i would like to brush on a number of things before i go spending money doing the wrong thing. First is regarding maintenance. One of the first things I am going to do to my new Z is a Major Service (timing, pulleys, bearings, seals etc.) & replace the coilpack and injector connectors. I hear the power steering bushings are also problematic on the Z32, should I also invest the time and money to do these anyways for peace of mind whilst its on stands? Is there anything else that i really should turn my attention to considering the unknown history of the car beyond knowing its got 155xxx km on it and has had an auto behind it for its entire life? Secondly I wanted to ask about the cruise control. The cruise in the car is very much so in a working state now, When i change the car over to a manual transmission will i lose the use of the cruise control or not? I tend to go between Blue Mountains NSW and Sunshine coast a fair bit so having it for the long trips would be a massive bonus. Third, lets talk about Diffs. Currently I have the choice of fitting a Twin turbo diff or leaving the n/a diff in the car. considering im building a daily thats going to be used very occasionally on the track (might see a track day once or twice every 3 months and the odd mountain run here and there). Which would be better in terms of gear ratios? Is there any difference in terms of limited slip between the n/a and the tt diff (i.e. na being a single spinner whilst the TT being a 1.5/2way). The na is a 92 ADM 2+2 auto & the TT is an imported 89 2+0 manual. Next is exhausts. Whilst i've dealt with both an n/a and TT Z in the past I would like to know what size Exhaust people feel is best for the n/a. I was thinking about going with a 2.5in system but im worried about the lack of backpressure and a loss of power, i'm not really that concerned about if it sounds good or not as most of the time i will be cruising around with the windows up, a/c on and the music going. Would a 2 & 1/4 better suit the car or is a 2.5in fine? I'd also like to ask about the "rubber wing". This car has one, im planning to shave it and use my Bomex wing on it. I've heard horror stories about the wing soaking up moisture and rusting out the boot below it and it not being worth trying to remove these so called "rubber wings". Any input on this before i attempt it would be great. Judging by what i see in alot of the build threads ive been reading over the past week i've seen alot of people are straying away from what are considered the "main brands" of coilovers (when compared to the cars i normally deal with). If anyone could offer up a reason why they are ditching TEIN's and the like for Powertrix that would be great. The next subject i would like to talk about is brakes. I'm planning to swap my Twin Turbo brakes onto the n/a when i get around to doing the major service and manual conversion. I will be replacing the rotors for some form of slotted rotor (not gonna bother with the 12" upgrade from Z1) but is there a preferred pad of choice? When i was still building 323's the pads of choice were either a QFM HPX or EBC Green Stuff. Whats the pad of choice for the 300zx? I would like something that is fairly soft (i don't mind doing pads twice a year) with a hard bite but something that also works well in the wet. Lastly i would like to talk about Tires, More specifically performance tires. During my time building the 323's the tire of choice (limited choices for a car that size, but the Z has alot more options) was a Kuhmo KU36. Now i have the option of stuff like the 595 EVO, Toyo Proxy, Advans and all sorts of other stuff. Is there any tire that seems to be pretty uniform amongst Z owners? I'm not prepared to pay more than $1000 per 15xxx km. If it helps i plan on using 18in wheels with a 9.5" width all the way around.
A lot of questions, so here goes. 1. Maintenance, you have covered most of the engine problem areas. A plenum pull and water hose bypass (under plenum) is a good idea if it has not been done. To nip any injector problems in the bud it could be a good idea to get the injectors reconditioned. Next, PTU. if it has a series 1 PTU its worth upgrading to a series 2. A series 1 PTU may work for many years and let you down with no warning, Also make sure your contacts in the CAS are also thoroughly cleaned. 2. Cruise control, someone else can shed light on this one, but I think you need to install a cancel switch on the clutch pedal. 3. Diffs - I'm out 4. Exhaust - 2.5 is the preferred choice for good breathing. 5. Rubber wing - Yes they do cause problems with rust in the hatch. My advice would be get to it sooner rather than later. Use a metal filler to do the holes, not a bog filler. The bog filler will shrink over time and show cracks in the paint. 6. coilovers - I'm out 7. brakes - A few people here have gone for the Brembo upgrade. I find the TT brakes to be fine. Tyre grip plays the biggest part in good braking, unless you tracking your car, then heat is the biggest problem 8. Tyre choice - I prefer a good wet weather tyre, not worried about brand. I want the damn thing to hang on when I need it. Doesn't matter what tyres you have if the suspension tune is not right. 18's are a good size rim with not too much wall flex.
I can copy and paste phrases from your thread and drop them into the search on this forum or even Google and get results. Sure if you're lazy it is easier to just drop in "sorry if this has been covered before" and ask away. Strange thing is that you have typed so much, so you don't seem too lazy.???? If you are building up your NA for daily, then build an NA as it was intended. Rubber spoiler, if it is in good condition leave it alone and concentrate on other areas. The leading edge should be cleaned up and use some auto silicone to seal where it meets the hatch. If it looks like there is a problem then piano wire the sucker off. If your auto is in good condition and your cruise is working, keep it until it becomes a problem. Concentrate on other areas. You can look into that six(6) speed manual upgrade that mounts inside the auto bell housing, for later. The TT diff is taller ratio, not suitable. Ask a TT owner if they will swap with you If you are upgrading rotors then you should read that thread about the exact topic. There is a guy who says it is cheaper to buy TT rotors. PS: who cares about FWDs, completely different animal mechanically.
If you're really wanting to get into it do the complete front of motor service including crank seal, tensioner and idler bearings. Pull the plenum off and change the heater hoses, and do the under plenum hose bypass. While the plenum is off you can reseal your cam covers, and get your injectors serviced and replace injector o rings and buffers. Understand though this is a significant amount of work and thousands of $$ in part for what may be considered preventative maintenance. NA motor/NA diff. The NA and TT rear end have different ratios. Nismo make 1.5 and 2 way centres for the NA diff. Headers and 2.5" Who is a lot of people? The majority of owners these days vote with their wallet. There is nothing wrong with Tein, especially if you plan on doing any performance driving ie circuit etc. Both of those pads that you mentioned are pretty good. Contact http://www.gslrallysport.com/ from up your way -they used to be fairly active on the forum and have a good history of offering good advice and pricing. Both of the tyres you mentioned are pretty soft and have low wear ratings. Sumitomo HTRZIII might be worth a look.
I love the NA dif in a TT. Best mod bar none. Long highway drives you will obviously sit at higher rpm with the NA rear. If you go spastic power with the NA, you will break stuff.
Not sure if you realise that he is considering going against the grain on this mod. He was thinking of putting his TT diff on his NA car. He likes being different.???
Also re brakes NA rotors are 280mmx26mm, TT are 280mmx30mm. The only reason I would consider fitting a TT caliper in your situation would be to then use a 324mmx30mm rotor and a suitable adapter.
Actually - I'm asking which is the better option as i am parting a twin turbo and IF the diff out of that was better, then i would have been keeping it. Hence the reason for asking. On the RX7s the turbo II & savanna Diffs are the best. Sorry for any confusion, but im trying to be as informed as i can before making decisions so i can have a quality built car at the end of it.
First is regarding maintenance. One of the first things I am going to do to my new Z is a Major Service. Just check over everything. the power bushes you mean 'steering rack bushes' ? . if so they can be changed while the motor is in the car, but do have to be done while on block. mine are still stock are are fine. Secondly I wanted to ask about the cruise control. Cruise control will work fine after you change to manual (i did a manual conversion too) it actually works better in manual than it does in the auto . You know when you speed up using cruise control and it drops back in gear and essentially floors it. you wont have this problem with a manual as you control the gears. Third, lets talk about Diffs. The diff is not a bolt in , you need to change the entire subframe. Both are stock Viscous LSD's and a TT diff would be an overkill. i personally believe the stock ratio is perfect for a NA (1st=50km/h, 2nd=100km/h , 3rd=140km/h) and the ratio is whats going to keep you close to the turbo guys hehe. at 110km/h my car sits at just about 3000rpm. ohh and NA is not a single spinner Next is exhausts. I run twin 2.25 exhaust and with a single hi flow muffler, and i think its perfect. << But i saying that i havnt driven one with a twin 2.5 inch. Its not that loud until it gets over 4000rpm. on idle its very quiet. I'd also like to ask about the "rubber wing". Pull the wing off , you will save 10kg haha . any scratches or marks while removing will be covered by the bomex wing. if you have rust under their, just treat it prior to fitting the new wing. I took mine of and replaced with the bottom half of a bomex two piece wing. Judging by what i see in alot of the build threads ive been reading over the past week i've seen alot of people are straying away from what are considered the "main brands" of coilovers Honestly most cheap coilovers feel 'just as good' as name brand. If you buy damper adjustable , just soften them on long trips. I run r32 GTST coilvors (swapped in a silvia rear knuckle to fit eyelet type coilovers, as i had these coilovers sitting around). Im running BC base height and damper adjustable coilovers 8/7kg <still feel too soft... these coilovers felt better than my previous set (Endless Zeal coilovers). The next subject i would like to talk about is brakes. Doing the TT brake swap is not worth it IMO. But if you have them lying around, you may aswell. Im running Bendix pads in mine, i havn't overheated them (on my spirited runs ) , but then again i havnt been on track with them yet. Lastly i would like to talk about Tires I running Federal tyres on my car. They arnt as good as I expected in the dry. I wouldn't consider them better than my old Champiro GT radials, or My old Dunlop SP sports (ive run both of these) .however they are AMAZING tyre in the wet.
On another note, there is no such thing as "keeping backpressure to help performance" ......backpressure is exactly what it sounds like, it is a restriction and should be eliminated. Its exhaust velocity that counts when it comes to sizing, i ran twin 2.5" on my NA for 4 years....everything from a custom system, my current UAS exhaust and even ran straight pipes for a week..
Your worry is sort of on the right track but as stated above it is not actually back pressure you want - you never want that - that is a myth - you want back pressure low as possible. It is not hard to see how the myth would arise though from someone who only has experience and doesn't have physics theory to go on. What's actually happening is that to a point as you decrease exhaust diameter you increase exhaust velocity which increases exhaust momentum and it's that extra momentum which leads to the gases getting out of the way of the gases behind it faster leading to less resistance for the gas behind it. However reducing exhaust diameter also increases resistance to flow which will decrease velocity and increase back pressure. So there are 2 effects there that work in opposite direction with change in exhaust diameter. This means there will be a sweet spot. Your job is to find the sweet spot where exhaust diameter gives max velocity and minimum back pressure.
Ah righto - I was under the impression that if you had too large a diameter with your exhaust that you would have gasses change direction about half way down the system like you do with a rotary. I understand restrictions are bad but I'm also pretty sure i was doing some reading some time ago that states you want SOME backpressure, not alot but lack of back pressure = lack of throttle response. Not sure how true that is, but thats where that thought pattern comes from.
Too large a pipe will give you less horsepower and hence less throttle response than an optimally sized smaller one. But it is because too large a pipe causes a drop in velocity and hence momentum of the exhaust gasses. Back pressure is always bad. People see that the smaller pipe gives better performance and think smaller pipe is restrictive but I get better performance therefor some back pressure must be good. But it's not the back pressure that is doing it but the higher velocity the smaller pipe creates.
Correct me if Im wrong.. The reason you need some sort of exhaust velocity on an NA, is to create a 'vacuum' Between the exhaust flow out and the closed exhaust valve. as the exhaust valve opens, this vacuum pulls out the exhaust gas (as well as the exhaust stroke pushing out), this creates a 'clean' exhaust gas free chamber. Not only does the exhaust velocity do that, it is also helps with 'Scavenging' , which is when you have Valve overlap, the intake air is 'pulled' from straight from the intake side out the exhaust. This increases flow rate of air into the engine, and will help the torque curve considerably (this is important on our car especially due to VCT). If you have no velocity in the exhaust, a smaller vacuum (or none at all) is created, and it makes it harder to expel the exhaust gas when the valve opens. Not only this, when 'scavenging' , some of the exhaust gas will get pulled back in due to the intake stroke, which means a chamber half full of exhaust gas . This is called 'back pressure' ( I think you may have mixed up your terms ) ^^^ I hope this clear it up, its how I understand it anyway.
I'd agree with that. Its the momentum (mass times velocity) of the exhaust that means it can leave behind a lower air pressure (doubt if its a full on vacuum but certainly less air pressure) that offers less resistance to the next pulse of air. A physics lecturer I knew would baulk at describing a vacuum as sucking* but colloquially that an OK way to put it. You might then ask why not make the pipe diameter as small as possible and the answer is that the closer air is to the pipe walls the more resistance to flow it experiences. The air right next to the pipe wall is stationary and the velocity of the air increases as you go further away from the pipe walls. In fact as you increase the pipe diameter resistance (or something - its long time since I was at Uni) to flow decreases in proportion to the 4th power of the pipe diameter (or maybe radius) - pretty sure its the forth power - but like I said its a long time since I was at Uni - bottom line is you don't need to increase pipe diameter very much to get huge increase is flow possible. But as you increase diameter while you decrease resistance to flow you decrease the velocity and hence the momentum induced vacuum effect. So you have to find a diameter that is a happy middle ground of wide enough where lack of pipe resistance to flow is good but drop in velocity is not bad. (*In the sense that a vacuum doesn't providing a pulling force only an absence of force that allows a pushing force to work better).
