The Z31 Project - Race Car

[260DET]

There will be some secret squirrel custom work done on the rear suspension, using the OE stuff as a base. Details of that will emerge in due course. At the moment I'm just happy to get some good bolt on stuff as a start.

[dat2kman]

What sring rates front vs rear are they supplying you?

What is the current corner weights of the car now, in a track ready condition?

The poundage rates front to rear from factory, will give you an idea on fore/aft pitch.

Z31 motor is set back behind front wheel axle centreline, ( mostly) so no need for heavier front spring rate from factory.

 

Most f the "race spec coil over" type kits, tend to come with ridiculously high rate springs, due to the drift brigade being sold what the manfacturers want them to buy.

[260DET]

Will be using King springs Jason, supplier suggests 8/6 in kg to 10/8 F/R with their valving, I'll start with 8/6 which is similar to what the 280ZX has. The rear suspension itself will have it's measurements run through Susprog or else I'll get some graph paper and do it the old fashioned way. I like working out all this shit, it's part of the reason for doing this project.

Edited September 2, 2016 by 260DET

[dat2kman]

Kilgrams s so wde ranging.

Dont the suppliers talk in pounds ratings anymore?

Something thats 6-8 kg is akin to 225-300 pounds, huge range.

Especally when changes f less than 25 pounds can make big differences.range

Paper calculations are one thing, actual track testing is what shows what has worked.

[260DET]

US supplier talks in metric, Kings talk in Imperial, work that out lol. As you know Jason it's important that any dynamic suspension changes are favourable eg more camber on bump, more toe on rebound. That's what I will be working on using Susprog or whatever, the suspension design that will be used facilitates such adjustments. With the S30's strut suspension dynamic camber is no problem but dynamic toe is, it is not available. Which is maybe why some of the S30 racers use a lot of static toe.

[dat2kman]

Programs, and paper are no substitute!

Your true test will be the high speed slight right on the full 3.0 km crcuit at MP, (after the RH turn to older/shorter layout)

Its that fast sweeper, with the multiple pre, mid, and exit undulations, with road camber change, that you need to run over multiple times, to then get a feel, via your bum and hands, as to fine tuning spring rates, and shock bump/rebound settings.

 

The other sequence, for lateral adjustment tuning, is the uphill right/left flip flop, coming onto main straight, also on 3.0 km circuit, it has a short bit of straight between each turn, that settles the car.

 

The Proddie cars cant fine tune/adjust, like you will be able to, they get a bit ragged, on these two sections of track.

The full adjust cars, ie Sports Sedans, open wheelers, 2A Sports, can dial in to suit, as will you be able to!

[260DET]

Seeing that the body is at rest it's a good time to cut things so some of the top radiator support panel has been removed, mainly to lower it for easier engine removal purposes, the replacement is some 25x25x1.6 square tube which will be welded into place. New radiator is a V8 Commodore all aluminium replacement which will be mounted vertically and not at an angle like the original. It's a little bit smaller in size, not much though, but the core is about twice as thick so with proper venting it should do the job.

 

 

[260DET]

Radiator and fan mounts all done so that can be put aside until assembly time, next job is mounting the DBW accelerator pedal and modifying the pedal box so the electric steering mechanism clears. Pic shows the fan which came with the radiator properly mounted not using those plastic retainers which thread through the core. Pads on the bottom sit inside cups welded to the body while the arms near the top bolt on. Yay, the first fabrication job is done, progress 

 

[260DET]

Electric steering is now mounted internally using some fabricated parts including a new 30x30 dash bar and retaining the stock pedal box, drive by wire accelerator pedal is also mounted. The supplied steering assistance variation adjuster will be dash located eventually, the supplier wired that. In all one of those awkward, time consuming jobs that at the start is a bit of a 'will it all fit' adventure. Now to remove it all, finish welding and paint the OE unpainted pedal box. Obligatory pic shows the steering motor in the middle right behind the dash bar..

Edited September 17, 2016 by 260DET

[d3c0y]

You've probably already explained this, but why electric power steering? Packaging and ease right?

[260DET]

You've probably already explained this, but why electric power steering? Packaging and ease right?

 

Gets the weight back, a PS pump and mount has to be added to a crate engine. less complication and space needed with no reservoir, custom lines or a cooler required, potential oil leaks avoided, dash control of steering effort, less power loss.. Overall weight I'm not sure but probably a bit less but the weight is a bit higher and it needs a fair bit of power to operate. And of course here the steering shafts have to be matched up and a support bearing installed although being custom the steering wheel has been able to be repositioned.

 

Besides I like to try new things although often that gets me into trouble

[260DET]

More of the trivial that eventually ends up as a race car, I love the practical detail, working out what will do the job reliably, simply and which involves minimum weight by paying attention to design. Underneath all the crap the Z31 is quite decent, the body carries very little extra weight and should be quite stiff when everything is done. Today we are getting really trivial, the steering wheel adapter was a real lump of pot metal so we got stuck into it and carved off about half of the original weight by the simple expedient of chopping a chunk off it, the other pic shows the replacement steering wheel after drilling and tapping what was left of the adapter and screwing the wheel to it. Total weight 140 g compared with 223 for the original wheel.

 

[260DET]

Rust 'repair' race car style. If the part is non structural, like a front guard, then just fix it up the easiest but permanent way possible. If it is structural then my procedure is to clean the area removing all loose rust, hit it with rust neutraliser then work out if the part should be made stronger/stiffer during the 'repair' process, always keeping weight to a minimum. On the Z31 the top of the rear panel that meets the bottom of the hatch was significantly rusted in several places, it's certainly a structural piece so the decision was to plate the entire panel using stiff zinc plated 1.2mm sheet. I avoid using plain mild steel for any structural part. Pics show what was done and the procedure, note that the back edges of the plates will be welded when on the rotisserie and the whole job will have a final dose of fish oil.

 

   

[260DET]

As well as rust repairs these bodies have some large openings for various purposes, my idea is to weld all but the few essentials up. Pictured are before and after shots of a vent opening in the lower B pillar which had weakened it so much that both sides were cracked at the top outside corner of the opening. Also shown is a large hole rusted through both inner and outer panels just forward of the A pillar door hinges on both sides, caused I suspect by the car being parked facing up hill so water could not get out the drain holes. There are a few bits like this that need repair and which could not be seen when inspected, the bodies on these cars have lots of double panels and are way more complex than a S30's.

 

 

 

[260DET]

OK, a break from my dodgy looking but effective welding, the coilovers have arrived and are presented to you in all their not Tein green glory. Imported without springs, Kings will be used and when changes are likely it's best to stick with the one brand.

 

 

 

[260DET]

This project is very much alive, am hoping that it will be ready to take to Bathurst in 2017. As for doing a race car Z31 project there are pros and cons to work through but basically for race use it is not a particularly a heavy car and has good aero. It really is a development of the original S30, unlike the Z32 which is a completely new car. A new auto transmission package is planned using the same LS3 engine that has performed so well in the 280ZX, the new auto will be about 30kg lighter and have engine braking which is something that you don't miss until you don't have it.

 

The two engine stands rotisserie is made so next week she should be flippable, very careful attention will be paid to firstly repairing the usual underbody dings and then looking at what can be beefed up with minimum extra weight to improve handling. Had a close look at a MX5 the other day, boy do they have some nice body stiffening features. There is a reason why those sorts of modern cars handle so well, I'm trying to transfer that knowledge to this project.

 

Sorry, no pics 

[d3c0y]

That's my project deadline too, group transport buy?

[260DET]

The L34 project? It will love Bathurst.

[PZG302]

Easiest way to stiffen the shell up for handling is a well designed cage tying into the suspension mount points.

 

The cage in my S14 is a really well thought out cage and a credit to the builder. The cage ties into the cradle mounts in the cabin and the rear top mounts in the parcel shelf. The cage doesn't punch through the firewall, but I have a knee breaker bar to replace the standard cross bar in the dash that the steering column adjuster had been welded to. I also had the engine bay seam welded as well as the two cross seams in the floor.

 

When I got the car off the rotisserie and onto jack stands, I didn't realise I had set up one stand a notch lower than the others, and it wasn't until I was climbing around inside and had all my weight over the shorter set stand that the shell rocked over onto it. It was pretty easy to balance the shell on two stands diagonally opposite each other.

[260DET]

S chassis is one of those modern chassis cars like the MX5 I was referring to, the Z31's chassis is not in that class so it needs some targeted reinforcement as well as a cage which it will get.

[PZG302]

Unless you're talking about an ND,  NC  MX5 I wouldn't say that the MX5 chassis is that good. The NA and NB8A chassis have a lot of flex from the factory, the later NB's got extra bracing from the factory and even then the aftermarket bracing available can make a big difference.

 

My NA6 was a well kept and good condition car that had plenty of scuttle shake and a bit of flex, the torque box design roll bar it had certainly helped tone down the scuttle shake, but they do need some reinforcement to make a stiff,

 

I would imagine that not too much reinforcement would be needed, just the usual seam welding in the engine bay, and a bit of welding around the suspension mounting points to help. 

 

Depening on what rules you are building it too, the cage will be easiest way to stiffen up the body, making use of mounting points around suspension mounting points where you can.

[1600dave]

I was amazed by how stiff the new roll cage is in my 1600. It pulled a little from welding so one front leg was 4 or 5mm off the floorpan. I thought I'd just pull it down with the mounting bolts, but it barely moved. Ended up putting another thickness of 3mm plate as "packing" under one foot to get it right.

 

And yep, earlier MX5's are pretty "floppy" without all their additional bracing. Had to take all the underfloor bracing, engine bay bracing and transmission to diff alloy "ladder" off mine to replace the engine and it sagged quite noticeably as the axle stands / shed floor weren't all level. Had to carefully adjust the axle stands till the doors opened freely again before I replaced all the bracing. All good now, though it does get quite a bit of scuttle shake. Its a late NB, so has more racing than earlier MX5's.

Edited December 11, 2016 by 1600dave

[260DET]

The Z31, like the S30 and the S130, looks to be weak both vertically and horizontally where the front chassis rails butt up against the firewall. Both points will be reinforced with braces welded across diagonally. The sills will have some RHS running front to back and tied into other structural points. Those and some cross transmission tunnel bracing are the major bits. RHS from the top of the A to the B pillar has already been done to close off the targa top cut outs, these will be tagged to the above door cage bars in due course.

 

At present I'm looking at some pretty serious mods to the rear semi trailing arm suspension, the whole assembly weighs a ton for a start.

[260DET]

Stock rear suspension component weights - each arm bare but including the hub is 14kg, the X member is 14kg too so a total of 42kg. Not including the coilovers. The arms are of course unsprung weight which is the main problem, they are multi function which is a bar to getting a lot of weight off them. It would not be hard to design completely new ones at about half 14kg but that would require complicated stuff for getting the various alignments correct and then jigs to use for the fabricating.

[dat2kman]

Plenty out there for s30

A few have fabricated semi-trailing arms for other models, once a jig is made, shouldnt be too hard to make in Cro-Mol.