drmotorhead

I am planning my next project car and would like to get input from anyone with constructive comments. There should be pictures at the end of this post. If you don’t see them, I will add them shortly.

Not counting a boring year after turning 16 and having a VW Beetle and then a Toyota Tercel, my first real car was a Datsun 260z that the previous owner had converted to a 350 chevy with a 700R4 trans using the JTR(Jaguars that Run) designs. It ran well, but it was a little fragile. Working on it was great fun and over several years I disassembled and reassembled the car more than once for various repairs and modifications. Since then I have owned and modified many cars, including a Buick Turbo-T, C6 Z51, C6 Z06, Corvette C5 Z51, a Supra, an NSX, and a 98 Camry CE V6 manual with the trd SC, headers and extra boost. I just sold my 2000 M5 that I enjoyed turning into a 450hp 3650lb ride.

I am ready to build a 240sx version of my first real sports car, the V8 260Z. This is the basic outline.

S13, early year, no sunroof, manual windows
Stock exterior other than steel flared fenders that follow the body line, similar to Chargespeed 30mm front w/o holes at the trailing edge and Chargespeed styled 50mm rears.
255 fronts tires, rears 285 – 315’s depending on what fits, normal camber, no wheel protruding beyond the tire.
Only in the front: BBK, coilovers, and 5 lug conversion(why only front? Keep reading.)
LS7 engine installed with Sikky kit, or, since DFI excites me way more than my ex-wife, possibly a C7 LT1 with AFM and VVT deleted and a cam.
Slightly wider front fender to accommodate a wider tire, approx. 255mm(normal camber, no wheel lip protrusion)
2” wider rear fenders to cover 285-305mm tires
Various weight saving measures: CF seats, a one speaker stereo, real CF hood/trunk or hatch, Braille li-ion battery, use aluminum or Cf where possible.
Complete rear suspension and manual transaxle from a C6 corvette

The last one is the clincher. Why do this? Weight distribution, technologically advanced and high performing rear suspension geometry, a nearly indestructible trans and LSD, great brakes. 2008 and up Z51 tr6060(or from a Z06) has upgrades from the T56 architecture. No need to add a BBK, new LSD, better half shafts and various suspension pieces to make the stock rear work well with 600hp.

The s14 has a weight distribution of approximate 55-45 front to rear. Great for drifting, not so great for putting down 600hp.

The s13 starts at 52-48 front to rear. Better than s14, but still nose heavy.
Moving the 100lb+ trans about 4ft to the rear is a big transfer, and the beefier TR6060 is a little heavier than the T56.

Changing from a 45lb lead acid mounted in the front to an 11lb Li-Ion battery in the rear will help. Real CF hood drops some weight on the front. There is the potential to get the front end weight to around 1250lbs, which means a conversion to a manual steering rack becomes possible. I have read a manual steering rack and losing the pump and hoses drops 30+ lbs.
The projected curb weight is 2750lbs with AC, a one speaker stereo, and a pair of CF shell seats, and no back seat(maybe a couple of lap belts and pillows in case I want to scare three passengers at the same time).

With all of this, the weight distribution changes to somewhere between 47-53 and 45-55, partly depending on body style and a few unknown factors.

The Nissan rear is fairly compact and made of steel. The C6 suspension is aluminum and similar in size. There are 3 issues with mounting a c5/c6 rear in any other car:
Different mounting locations for the cradle
The C6(and C5) upper control arms do not mount to the cradle, they bolt to the chassis,
Upper shock mount is not in same location

These problems are made much easier to solve with a somewhat new product: Corvette Interface Suspension Adapter by Dobbertin Performance. This is Rick Dobbertin’s company, who some of you may recognize from his pro-street creations or from his amazing Surface Orbiter.

This upper cradle adapter allows the whole rear assembly to be bolted to a back-half frame that has rails at the appropriate height. Get the rails in the right place, everything else flows around it.

I would like to get the traction control to work. This car will be street driven, and my Z06 was difficult to drive in the rain. I would not drive in the rain on purpose, but I am in west central Florida. If the engine control computer has the brains and the rear is set up for wheel speed sensors, and we can add sensors to the front hubs and wire it in, it should doable.

Since the rear is getting back-halfed, the spare tire well can go and the gas tank would have to be reconfigured. The back seats are already getting mostly eliminated. These changes can free up a lot of room for exhaust routing and mufflers.

Comments?

Attached Images

	240sx corvette interactive suspension adapter.jpg (86.2 KB, 198 views)
	240sx see thru layout from above.jpg (101.2 KB, 156 views)
	240sx corvette reat susp transaxle layout.jpg (44.3 KB, 147 views)
	240sx c6 rear suspension sitting on floor.jpg (59.2 KB, 149 views)
	c6 torque tube.jpg (176.8 KB, 155 views)
	c6 diff and trans.jpg (149.1 KB, 148 views)
	corvette-zr1-chassis-02 good under pic.jpg (106.2 KB, 139 views)

Def

If you keep the interior you might get close to 50/50. Dropping the interior takes out a lot of weight on the front, and LS engines are not as light full-up as most would have you believe. They're a decent bit more than a KA with all accessories on them I believe. KA is about 40-50 lbs more than an SR give or take, so you can extrapolate out weights yourself.

You can fit anything with enough fab work. The biggest issue I see is probably frame rail height and width if you're going to put the UCA off of them.

If you keep most the interior, an LS7 S13 w/ AC will probably be about 2800-2900 lbs with a few lightweight bits on it like a CF hood and lighter battery. Quite a bit depends on your wheel and brake choices, as you can easily swing the weight 30 lbs on each of those choices. I have an SR20DET, no AC, very little interior, 2 FG seats, 4 pt rollbar, very lightweight brakes, lightweight RPF1 wheels, lots of other weight savings, and I imagine I'm somewhere around 2460-2480 lbs now at 1/2-3/4 tank gas (corner weighted it a while ago at 2550 lbs).

Powersteering pump and bracket weighs 10-12 lbs, reservoir a couple of pounds. The rack weighs about 10 lbs, and a manual rack will be about as much (there is no commonly available one that drops in). So maybe 10-15 lb savings with no PS. It's doable to drive it at speed, but always a bear if you have decent caster. I personally didn't like it, and am faster with PS on track.

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S13 Hatch - Goes around tracks quickly
DEFSPORT

Croustibat

Personnal opinion, i think this is a hell of a lot of work for very little result.

The "easy" and most efficient way would be to buy something like this (this is a C7 with the rear mounted gearbox but a C6 will do fine)
http://www.ebay.com/itm/2014-Chevrol...-/112102176694

And bolt an S13 chassis on top of it.

Now, i say this is a bit pointless because S13/14 rear suspension "problems" can easily be solved with bolt on items. Same goes for the front.
The weight distribution is not an issue either, unless you are one hell of a pilot that can actually feel a 1% change. I'd be more worried about the left / right difference, since these cars were designed for a driver in the right seat; heavy exhaust & manifold are on the left. The rear right side has like 100lbs less than the rear left.

If you actually are capable of extracting the performance of a car up to the point such weight distribution becomes a limiting factor, you should be building a race car, not something based off a production car with all its tradeoffs.

What i am saying is if you want to do it because you just want to, then fine, do it. But there are no performance reason to do all that, the result will not be whatever you want it to be IF it is the reason you want to do it.

So either use a 'vette chassis with an s13 look on it, or get an S13 with a bolt on pbm/tdp/gktech/wisefab suspension kit front / rear and a bolt on LS swap kit and call it a day.

derass

You bring up many great reasons as to why the retrofit is worth it and seem to have a good idea of how to get it done. If you have the means then I think you should definitely go through with it. Many people, myself included, would love to follow the process and you'd be left with an incredibly unique 240SX at the end of it.

But if it were me, I'd either buy a Corvette (which you've already owned) or modify the 240SX more "traditionally".

Either way, sounds like a cool build. I hope you post it up!

pacotaco345

Didnt someone else in here literally try this exact same thing and give up a week or so ago? Lol his build should still be on the front page and his partout is in the classifieds


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derass

Here's the link: http://zilvia.net/f/showthread.php?t=622223

drmotorhead

pacotaco345, I have read through that thread, and it was crazy to me, and I dont mean crazy in a good way. He way trying to build a whole new car and trying to custom fab every item. Cutting the front subframe??? I would never do that, or much of anything that guy tried to do. Other than wheels/tires and a slightly lower ride height, the car will look fairly stock from the outside.

For the vette donor parts, I am buying the whole car and selling what I don't use.

I did decide to simplify a bit and narrow the vette irs about 4", so no need for wider fenders. The half shafts are all that get shortened, and the CV joints can handle it.

Got to get back to work, will post again later.

Thanks for the comments!

drmotorhead

Also, he was trying to integrate the transaxle into the existing architecture. That sounds more difficult than a back half job. Back half jobs are very common.

drmotorhead

Hello DEF, you mentioned one concern that is a big one. "The biggest issue I see is probably frame rail height and width if you're going to put the UCA off of them."
I have not done a back half job on any of my cars. I have not seen enough of a cut of s13 to know where the strong parts of the unibody are. I assume we would start with cutting out the floor panels from the rear seats back, decide where the frame rails need to be, then weld back in gussets, bracing and sheet metal as needed to correctly position the rails. Need to leave as much room as possible for new gas tank, battery and exhaust. it would all be hidden from above by a raised floor.
A cage meeting the requirements of standing mile races will be needed as well. Speeds of 180 to 205 make that mandatory(and a really good idea anyway).

Croustibat

The S13 rear section can be described with many words, but "strong" and "stiff" are not one of them; this is caused by the hatch design. The upper rear is full of emptiness.

A pic is worth a thousand words:



Note there is a "missing" part of the frame rail. Some chassis have them, some do not.

If rules allow you to cut a lot of things and use tubes as subframe mounts, you may want to go that way.

drmotorhead

I have looked through the Mojave Mile, Texas Mile/US Mile and the Colorado Mile rules. 1.75X.095 for alloy material tubing in a 6 point cage is required to go over 200mph. The 2 connecting points behind the front seats and the rear points should go to the existing frame and could be extended to the new 2x4 rails.

I will be eliminating the spare tire well and raising the floor in the rear, so there will be opportunity there for increasing the strength and distributing loads.

Other than having a safe car with good brakes and in a good state of repair, and having the expected safety equipment like five point seatbelts, they don't have much to say about what you can run.

Anyone know what kind of lift the stock s13 fastback experiences at high speed? I am assuming I will need a front splitter, rear spoiler and rear splitter.

drmotorhead

One of the reasons I am doing this is because I HATE NEW CARS. They are heavy and so complex that serious improvements are a pain in the A--. Example: I just got so frustrated with a 2000 BMW M5 that I lost faith and sold it. Putting in a racing seat should be easy, but not with this car. When the seat wiring harness(which has enough pins to run a whole car) is removed the steering wheel thinks you are working on the seat and decides to go in the fully up and retracted position. Only solution is to buy stock seat, cut it up for the harness, then plug it in under the seat. But the airgbag light will never go off.
Another example is the key. If you lose your M5 key and need a new one, the dealer offers FIVE different keys. if you want the good key, it is a couple hundred dollars, must be programmed correctly, and an entire chain of electronic and computerized events have to take place to get the door to open and the engine to start.

An Aerial Atom was on my short list, but I am in Florida and it rains way to much for a car with no top.

Another NSX was also on the short list, but I could not bring myself to cut into a car like that.

I want a key to open the door and start the engine. And if I want the window down, I want to hand crank it.

usrocket

Welcome to the forum drmotorhead!

jr_ss

There are obstacles and challenges with making an S-chassis go to or over 200mph. Here's a link to start sifting through. You may not find all you want/need, but it's a start.

Welcome to the forum from another 941 local.

http://www.motoiq.com/Projects/Nissa...peedRacer.aspx

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drmotorhead

Thanks for the link. I found that earlier today and have been reading it. Two things that jumped out at me were:

fairly stock aerodynamics: wheels/tires and some air management on the roof.
and
The speed of 191.9. Is that over a full mile? In both directions? That would be very hard on a car.

With 600hp and a total drag of about 12% less than a c6, and about 15% less weight, I would have expected a higher speed. Then again, I am not familiar yet with the problems LSR racers run into. As far as stress on the vehicle goes, I would think 1/4 drag is at one end of the scale, LSR is the other, and standing mile is somewhere in the middle. WOT at a high RPM for that long of a time would make a small weakness into a big one.

jr_ss

That record was at the salt flats, so I highly doubt it was 1mile to get up to that speed. That was a combined average of two runs. One down and one back, at least that's how I understand the text.

They have had issues with the car washing out at higher speeds and spinning.

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My SR20VET

drmotorhead

I did not correctly word the comment about the speed at Bonneville being done over a mile. I also looked into the bonnville race. There are two courses set up for LSR runs: 4-5 miles and over 7 miles. I think the measurement of speed is average speed over the last mile. My point was that the car spends a long time at WOT or near it.
During the runs, the salt surface was described as "wet and loose". I could continually hear the driver modulating the throttle. Two other cars spun as well. Then event organizers closed the race.
from the article:
"The H in H/PS represents the engine class with displacements permitted being between 1.0 - 1.5L. The PS portion is a specific class for a production body car void of aerodynamic modifications, using the same engine family available from the factory, (For example, KA24 or SR20 ) and the same induction method (single turbo must use single turbo or supercharger must use supercharger, etc)." [[not sure how they got away with the roof rails]]
"While attempting to push the record over 200 MPH, Chuck would go for Mr. Toad’s Wild Ride spinning the car not once, but twice at over 196 MPH. The car suffered minor damage as a result of the high speed spins but Chuck was fortunate enough to walk away unscathed."
They did an amazing thing: took a stock bodied 1.5 liter car to an amazing speed.
But...they worked with a rule book designed to make it difficult, even dangerous.
The rules for standing mile have rules for safety, but the car is up to the builder.

I have a low goal for curb weight. I may not get there. But along the way, I always for the lightest part that meets the performance goal. Aluminum over steel, carbon fiber over aluminum or steel where appropriate or possible, and titanium where possible.

drmotorhead

i planned on getting some parts together first, but a good car became available. Driving it home now. 1990, 85k miles, 2 owners, garaged, never any paint work. No rust on the car, but it appears the spoiler is plastic covered foam, and the foam wicked up moisture and the internal frame rusted from the inside out. Stereo, cigarette lighter and cruise control not working. Otherwise, it looks like I got a pretty good deal at $6500.
It has an automatic and more options than I wanted. Mostly easy to convert or remove as I go through the build.

Attached Images

1990240sx my car.jpg (318.1 KB, 43 views)

Def

6500.... pesos I hope? I think the S chassis is underrated, but a stock zenki S13 with hatch rust for $6500 seems like utter insanity.

I feel like you paid a ton for a low mileage number on the cluster. Who gives a crap about how many miles the cluster has - it's basically exempt due to age at this point. Plus the stock cluster sucks balls.

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S13 Hatch - Goes around tracks quickly
DEFSPORT

drmotorhead

The rust on the hatch was superficial on the surface where the spoiler was touching it. Otherwise, the car is rust free from top to bottom. It was garaged since the early 90's, and I bought it from the second owner. It was not just the miles. The rubber on the doors, window, everwhere was near perfect. A couple of barely visible dings on the sheet metal. Never an accident, perfect frame. Interior is nearly perfect. The only item on the interior that does not look like a two year old car is some minor defects on the area around the shifter. I drove it over 1000 miles home without an issue.
It was not that easy to find one that I don't have to spend time and money fix previous owners mistakes and lots of wear and tear issues. The cars I saw for significantly less money would have cost me more in the end.

fliprayzin240sx

Jeez, this just seems insane to me. I got out of S-chassis a few years ago and now own a C6Z. Between the height difference and width of the rear cradle to attempt to fit it into an S13 rear end, have you done measurements on how long the torque tube will be? Just seems too long to fit on a shorter S13. To get the rear end to sit where its supposed to be, how far would the engine sit in the engine bay?

But either way, this is interesting. I live in Riverview and if you need a hand or just want to bounce some ideas, PM me.

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drmotorhead

Fliprayzin240sx, regarding the rear suspension: the cradle can be narrowed 4 inches in this case. This puts the tires out 2" further than stock, just about right for 50mm fender flares. The half shafts get shortened as well. The CV joints can take the additional angle. With a stiff suspension it will spend nearly all of its time in a narrow range of travel.

The torque tube can be shortened. The driveshafts are available in CF for about $1300. I have not asked, but I would be extremely surprised if they could not cut that tube to a requested length before assembly.

Regarding height: I have overlayed side view internal layouts of both cars. Engine location is not a problem. It may be slightly higher or lower, but not much. The rear assembly in a lowered s13 is not significantly different that a lowered c6. What may require extra work is the driveshaft tunnel, which may have to be raised. The torque tube comes from the center of the crankshaft, instead of the lower back end of a front mounted transmission. The center floor pan between the "frame rails" from the back seat cushions to the end of the trunk is coming out anyway, so if needed we can increase the size/height of the tunnel. It might be a good way to make room for a dual exhaust. No cutting happens until we verifying a square chassis, install the roll cage install, and do some seam welding and gusseting)

Project is stalled for a bit. I did pick up a pair of CF doors last month, but then the IRS hit me with a surprise $13k bill.

I will try to post the side views of the two cars.

rawgarage

sheesh who sold you that auto hatch for 6500?

do u not enjoy it as is....

Frank_Jaeger

You need to get 180 degree headers don't think about it just do it.

PoorMans180SX

I smell a partout happening. Just like that other guy that tried to do this.

Buying a $6500 mint S13 to chop up is about as logical as buying a sword and melting it back down to use for gun parts.

Changing the static weight distribution 5% isn't going to do jack to help you "put down 600hp". That's the suspensions job.

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Frank_Jaeger

No please. I couldn't go through that again.

OBEEWON

I sold my S14's way too soon. In like 7 years they are going to be as rare as everyone thinks they are.

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Bushido

car is clean, leave it stock.

find another one to hack up.

this project seems like a ton of unnecessary work, but i hope you post pics if you actually go through with it.

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onehundredoctane

Or just buy a Corvette and be done. You can get C5s for under $10,000 now, and they even come with the drivetrain you want LOL

Bushido

SR or KA swapping a corvette would probably be less work...

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