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ANOTHER Datsun Z/LS3/T56 Swap Thread


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7 hours ago, 280Z-LS3 said:

I found post #13 in this thread informative.

 

https://f87.bimmerpost.com/forums/showthread.php?t=1270915

 

Thanks for the link.

 

Coincidentally, I called Essex yesterday and talked to their "brake pad guy"....might have been this same dude...not sure.

 

Anyway, he told me that currently their closest thing to a perfect pad is the DS3.12....which is what I have installed.  He asked me if I had heat cycled them yet, which I have not.  He said he was very confident that once I had heat cycled them, their cold bite will greatly improve.

 

My "Z" as set up is a bit of a challenge for brakes.  I am definitely going to need high heat capacity on track as the car can build momentum very quickly.  But as I still plan to street drive it, cold bite is an issue, exacerbated by the fact that it has no power boost.  He assured me that once properly heat cycled, I will be happy with the DS3.12 pads....so my plan is to soldier on with them.

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Finished the stitch welding....nice to have that chore done....and moving forward at my normal glacial pace.   Started building the supports for the main hoop of the roll cage.  I included c

Thanks for the kind words Vanilla.   I spent most of the day today getting the passenger side door hoop bent.  It really fought me.  To make it fit decently, bends in multiple planes are nec

Calling the cage done, at least from the dash back.  Also hit the tubes and welds with Scotchbrite so they are ready for primer.          

Posted Images

I've been driving the car around a lot to get a feel for it, break in the moving parts, and iron out all the bugs.

 

Among the bugs, the 1/4" ABS is not really stiff enough to use as a splitter.  In the picture below you can see that it is already deforming in the areas not supported by the turnbuckles....and I have not yet driven the car over 80 MPH.  It's kind of a quandary:  The part is going to take a lot of damage and need to be replaced often, so CF would be too expensive.  Maybe a flat piece of fiberglass will be my next move, not sure.  I know some use plywood too.  In the short term I might just remove the splitter.   Driving on the street it makes the car significantly more unwieldy than it already is.

 

Issues with the diff:  The OSG LSD clunks and bangs horribly during tight, low speed turns.  I mean it sounds like things are tearing themselves apart.  I talked to an OSG tech, and apparently my decision to use Motul gear oil during break-in rather than the $50/quart OSG oil is the main cause.  He said the Motul will work fine and protect all the parts, but that it will make the diff extremely loud, particularly during break-in (500-1000 miles).  So I guess I will ride out the noise and change to the OSG oil once things are broken in.  I am also questioning my decision to install a diff pump/cooler.  Just driving around for an hour or so, the diff temp rises to around 200 degrees and stays there.  I'm sure track use will heat it up more, but track day sessions are typically only 20 minutes, and the OSG tech said their oil is fine to around 270 degrees.  I doubt mine would get that high during track days, and if it doesn't I am going to yank the pump/cooler in the interests of lighter weight and simplicity.

 

Still not happy with the brakes.  Once up to temp after some hard braking, they work pretty well.  But, when cold they are a bit scary.  All this would be fine on a pure track car, but it isn't a pure track car.  This is with the Ferodo DS3.12 compound front and rear.   My next move is to try Carbotech XP20 pads.  The DS3.12 pads have a friction coefficient between .50 and .55 once up to temperature, but Ferodo doesn't state their "bite" when cold.  I will say it's "not much".  The XP20 pads supposedly have a .70 friction coefficient at all temperatures, which is about the highest bite of any brake pad material.  So I'm hoping they will give adequate cold bite and lower pedal pressure a bit at all temperatures.  Have to try them though, I'm sure there will be a downside of some sort.

 

Otherwise, car is running well.  No overheating or other problems.  I've never driven a completely "stripped" car before, and sometimes I feel like I am driving in a garbage can, but I knew full well that was coming.

 

Thanks for looking.

 

hqwfKZV.jpg

 

rAJgENv.jpg

 

h7K663P.jpg

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54 minutes ago, Ironhead said:

Maybe a flat piece of fiberglass will be my next move, not sure.  I know some use plywood too.

 

Honeycomb aluminum plate is your salvation!  I have no idea where to get it (unobtainium?) and sure it's ungodly expensive.  Read an article about a hill climb/time attack car that used it.  Their real job was in aerospace and had a piece "sitting around".  So stiff that a 200 lbs guy could stand on the splitter. 

 

Back to reality...  I like the idea of home made sheet of fiberglass.  Too increase stiffness one could mold in some 1/4 or slightly larger plastic tubing.  Watched a Aussie old racer guy on YouTube who makes race car body panels (I spend way too much time on the internet...) and his trick is to add various sized hose depending on panel being made to resist bending and torsional loads.  If I understand correctly the hose creates a rib in the fiberglass increasing cross section.

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30 minutes ago, 280Z-LS3 said:

 

Honeycomb aluminum plate is your salvation! 

 

This is the smallest size that they have that would work....https://www.flatironpanelproducts.com/store.html?model_number=AHP-04038--B-250, unless I made it out of multiple pieces....which I guess I could.  That's still less than a CF sheet that size.

 

This stuff would work well....but DAMN....$$$$$$: https://www.mcmaster.com/sheets/composite-fiber-aramid-honeycomb-panels/ (they also are not "rated" to use outside)

 

Even regular fiberglass sheets are expensive in the needed size...not to mention I'm sure shipping would further the pain:  https://www.mcmaster.com/sheets/fiberglass/

 

I could make my own fiberglass panels....but...you know....mess and PITA.

 

In a lot of ways plywood makes the most sense...it just seems so...redneck....especially if I didn't bother to paint it black....LOL.

 

Or maybe some plastic that is much stiffer than ABS?

Edited by Ironhead
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A lot of the budget endurance racing teams(Champ/WRL/Lemons) use alumalite. It's essentially the same as the aluminum honeycomb sheets, but with a plastic core instead. It's much more cost effective than the pure aluminum. 

https://overnightgrafix.com/alumalite-material.html

 

Plywood is definitely the easiest and most cost effective. Sanding the edges and giving it a decent paint job would make it hard to tell that it's wood unless you really look closely. 

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Tegris is not light. I have a COT splitter made of tegris, turned out too narrow for my front end, so it's just sitting in my shop. Pretty cool, but probably weighs as much if not more than plywood. If you just use it for the front lip and then do something else from the lip to the front xmember, that's a good one.

If you use plywood, it does matter what kind. Birch is supposed to be the stiffest, so that's what I used. It is heavy. I've seen lots of alumilite at autocrosses. Looks great until it touches the ground, then not so much.

 

I decided on plywood to see where it rubbed and how bad, thinking that I could adjust things and then do a more expensive/less durable one after I worked out the bugs.

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Great input guys, many thanks.

 

I think what I will do is take the damn splitter completely off while breaking in the car and ironing out bugs.  Driving on the road, damage is inevitable.  Or just leave on the ABS one until it destructs.  Looking at the photos, I think even with six turnbuckles, the ABS still would not hold up.

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1 hour ago, JMortensen said:

Tegris is not light. I have a COT splitter made of tegris, turned out too narrow for my front end, so it's just sitting in my shop. Pretty cool, but probably weighs as much if not more than plywood. If you just use it for the front lip and then do something else from the lip to the front xmember, that's a good one.

If you use plywood, it does matter what kind. Birch is supposed to be the stiffest, so that's what I used. It is heavy. I've seen lots of alumilite at autocrosses. Looks great until it touches the ground, then not so much.

 

I decided on plywood to see where it rubbed and how bad, thinking that I could adjust things and then do a more expensive/less durable one after I worked out the bugs.


Yeah man... plywood sounds cheesy but it is super durable. The wood is laid in alternating grain so it is uniformly strong in both axis. Great stuff for an application that will see a lot of vibration, rocks, flexing 

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Posted (edited)

I've been having trouble getting the brakes adequately set up.

 

Based upon tech advice a few years ago from one of my suppliers of parts, my starting master cylinder sizes were .612" front and .812" rear.   The problem with this combination, is that the front cylinder moves so little fluid into the relatively large front caliper pistons, I get a ton of movement of that side of the bias bar.  Conversely, the larger rear master cylinder, moving much more fluid into the relatively small rear caliper pistons, barely moves at all.  The consequence is that the balance bar gets massively angled and effectively "bottoms out" before I can apply sufficient pedal pressure to get full braking front or rear.  Clearly something was amiss...

 

So I contacted support at Essex Parts (A+/massive kudos to them, BTW).  He took all my data and subjective experience and said he thought my best starting point was to go with .75/.75 master cylinders.

 

In an effort to understand what was going on, I plugged all my data into this calculator, that 280Z-LS3 brought to my attention a while back:

 

https://www.tceperformanceproducts.com/dual-bias-calc/

 

There are some figures on this table that required an educated guess, but most was hard data.  As I played around with it, gradually it emerged that the .612/.812 master cylinders made no sense at all for my car/setup.  It provided much more line pressure/brake torque to the front wheels than I needed, and far too little to the rear wheels.  At least, that's how it looked to me.  After punching in a bunch of numbers, it indeed appeared my best starting point was either .700/.700, .750/.750. or .750/.700.  If I wanted minimal possible pedal pressure, I could go .612/.612, but I had already found that would give very long pedal travel, possibly more than I had available before the pedal hit the firewall.

 

This all definitely makes more sense.  Most front and rear calipers, even aftermarket ones, are designed to be usable with OEM style master cylinders that are the same size front and rear.  Many people using them will not have aftermarket style balance bar/dual master cylinder setups.

 

I don't want to name which place recommended the initial screwy sizing, because I might well have messed something up in the data that I gave them.   I honestly think that is more likely than believing that they got the math wrong.

 

I already have a .75 M/C lying around, because I bought that for my clutch before learning it was a couple of sizes too small.  So I am going to order a .70 for the rear and try that combination.  If I did the math right, I should get maximum braking with something like 65# of pedal pressure, which "sounds" doable.

 

Time will tell.

 

 

 

 

 

 

Edited by Ironhead
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Posted (edited)

On a related note....

 

Since with the small front master cylinder I was getting too much pedal travel, I started to analyze possible ways to improve the situation.  When I plumbed the brakes on the car, I used entirely AN-3 steel braided lines....no hard lines whatsoever.  Many were of the opinion that this would lead to a soft pedal.

 

I started to wonder if this had something to do with my excessive pedal travel....if the AN3 lines were expanding under pressure, they would certainly contribute to the problem.

 

I had a lot of hardware left over from plumbing the car, so I concocted a little experiment.  I bought two six foot lengths of steel brake "hard" line.  With adaptors, I connected one end of each to each of my two master cylinders.  The other ends were dead ended into a bleed valve.  So, basically, I had two six foot lengths of hard line with two valves to bleed the air out, which I did.  Twelve feet is probably roughly the total length of brake plumbing on most cars.

 

Once charged with fluid and bled, I stepped on the brake pedal with all the strength I could muster.  The pedal was rock hard, not surprisingly.  It felt completely immovable, like it was bolted in place.

 

Then I repeated the experiment using AN3 steel braided Teflon line, exact same setup, two six foot lengths of hose, bleed valves on each end, bled, and attached to each master cylinder.

 

This too resulted in an immovable pedal, rock hard, completely indistinguishable from the hard lines.

 

Could there have been a miniscule difference in the pedals, so small that my foot could not detect it?  Yes....but if your foot cannot detect it, who cares?

 

Now there might be other good and sound reasons to use hard lines rather than steel braided Teflon, like cost or weight.  However, I feel the methodology in this experiment was reasonably sound, and can state quite confidently that pedal feel is not a sound reason.

 

I've read a lot of opinions on the internet that hard line should be used wherever possible, but it has always been the standard internet "cuz I say so"....or "so and so says so" reasoning.  I have never seen anyone try a simple test like this that took perhaps an hour to do.

 

So to anyone who thinks AN3 Teflon brake hose expands and causes a soft pedal, I call BS.

 

 

Edited by Ironhead
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I think one thing you have to temper the don't use braided line for all the brakes is probably based on hose that was available 30 to 40 years ago.  Someone respected said it and then it was passed down as lore.  I think you have proved modern lines are fine and it's really up to the owner in what they want to run.

 

The one area where a single master cylinder can help is when they use fast fill.  That's where they use a stepped piston to move a lot of fluid initially and then it steps down so you have even force between the axles.  I don't know if fast fill is the right term but that's what I'd heard from the McLaren/Ferrari spygate scandal where they had redacted court docs but only drew over the top with black rectangles so it was easy to remove and secrets were spilled.

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I have about 400 miles on the car now, just gradually ironing out bugs...

 

Last time I drove it, I noticed a (new) clunking noise coming from the rear on acceleration or deceleration.  So, I figured it was time to jack it up and check things out, tighten bolts, etc.

 

Well, when I did final assembly on the car I could not find my HUGE washers that went on top of the front diff mounts.  So I used large thick washers, but not HUGE.

 

You can see what happened below.  The upward loads on the diff "circumcized" both of the mounts.  Easy fix, and probably something I should have anticipated.

 

BDJXpm5.jpg

 

The exhaust is a much bigger problem.  I knew it was very close to the ground, and driving the car is really pressing the point home.  It just hits the ground too much, too easily, and under too wide a range of circumstances.  It's doesn't require road debris or a speed bump, just loading the suspension, like when you level out at the bottom of a hill, is enough.  It's taking too much damage too fast to continue ignoring the problem.

 

1hPk5e0.jpg

 

So I have abandoned denial and accepted that I have to do something with the exhaust.  It's going to require new headers and modifications to the center section.  Fortunately the back section/mufflers are fine and I can keep them.

 

The only way I can think of to raise the header collectors is to make them a "Tri-Y" design.  Then the final collector will be a two-into-one instead of a four-into-one.  If arranged vertically, it would be much narrower than the four-into-one and I should be able to tuck it up quite a bit higher between the transmission and car body.  As the car is now, the collectors are the lowest point.

 

Most of the center section I plan to convert from twin 3" round to singe 4.5" oval tubing.  It will have roughly the same area as the twin 3", so flow should not be restricted.  There is even an oval 4.5" resonator on the market that is still narrow enough to fit within the trans tunnel.

 

The hassle will be the transitions...from twin round 3" to oval 4.5".....then from oval 4.5" to twin oval 3".  No such transitions are on the market, so I will have to just get metal in hand and figure it out. 

 

This is a huge PITA, and the exhaust is among the last things I wanted to have to re-do....but driving the car constantly cringing as to when it is going to hit the ground is no good either.

 

So for those of you doing exhaust on a Z, when you think it is high enough, move it up some more!  My goal is to have nothing lower than the frame rails....which may not even be possible.  Time will tell.  If I could just gain a solid inch, that would make all the difference in the world.

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  • 4 weeks later...

Exhaust V: 2.0......

 

I am trying to tackle my problem with the exhaust hitting the ground.  First step was to make a new crossmember.  It is basically the same design as the Hoke one I was using previously, just with wider and deeper exhaust recesses:

 

ol4LTnx.jpg

 

This is what I came up with for the exhaust.  There is a huge advantage, clearance wise, to building tri-"Y" headers, because the final 2 into 1 collector is much narrower than the 4 into 1 units, and thus can tuck MUCH higher up between the transmission/bellhousing and car body.  This was the lowest point with my previous exhaust, and I would estimate with this setup that I gained 1.5-2" of ground clearance in this area...which is a ton.

 

The problem I had with the mid section on my old system was that the two 3" resonators were too wide to tuck very far up into the driveshaft tunnel.  With my new design, the center section is 4.5" oval tubing...slightly larger in area than two 3" tubes....so it should add no restriction.  And, even with the 4.5" oval resonator it will fit up in the narrow part of the driveshaft tunnel as far as I wanted to put it.  The only limiting factor is I didn't want it too close to the CF driveshaft.

 

clIV5O1.jpg

 

dy2dG8X.jpg

 

Xy9u5cl.jpg

 

VRP2edv.jpg

 

IXxdYqu.jpg

 

Building another exhaust is an expensive PITA for sure....but I didn't feel I had much choice.  The tight ground clearance was seriously limiting the driveability of the car.

 

Now I just have to build a couple of tri-Y headers.....

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5 hours ago, 280Z-LS3 said:

Does the 4.5" resonator have a built-in x-pipe or just an open chamber type?  Honestly, I don't know if it makes any difference with your design.

 

Beautiful work!

 

 

Well, there is a Y-pipe at the beginning and end of the large oval tubing, so as I read exhaust theory, it is like the entire center section is a giant X-pipe.

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