Light Weight Sports Car Build

Hey there.

I'm new here and I have been looking for a platform to carry on this conversation. I hope this is the right place. :)

I intend to build a light weight sports car and this is to be a diary as well as a conversation about the project where I look for advice and guidance for the project. Full disclosure that I have never done something that big before. I'm comfortable around a car and have done my own repairs. But nothing major. Head replacements, oil changes, break pads as well as painted my own car and done small body work. Again nothing close to this adventure I'm about to start. But I love to learn and am not afraid of challenges. ;)

I would like to do as much as possible myself. But I'm also able to get help for things I can't do alone. I know a few people with skills that will be useful to the project. From welders to mechanics.

My goal is to build a light weight sports car.  The intention is a Coupe fastback, 2 seats, front mid engine, RWD, manual transmission and to keep the weight as close to 2200lbs as possible. So it needs to be small. Not as small as a Miata. But not as large as a Corvette. Something with an original design for the body.

I want it to handle really well. Top speed is less important than 0-60 and handling. Handling is really the most important factor.

I want a somewhat pure sports car, to a point. I would still like to have a few basic safety features, being a father and all. So no Viper levels of raw. I would like to have ABS, airbag, traction control and air conditioning. That's basically it. Not luxury items such as electric everything or any other amenities. Just the very basic.

Drivetrain wise, to keep the weight and size down a V8 might be a bit much. Since a straight 6 will make it too long to have a front mid engine set up, and I want more than a 4 cylinders, a V6 might be the sweet spot. But not decided yet. A small light weight V8 might also do. I  would love for the engine to be something a little more exotic though, rather than the natural choices normally used. So I'm thinking something less common than a LS. :) Gearbox wise a 6 speed manual is more than fine. ;)

My goal is to select an existing platform and use that. So instead of building a custom one of tubular chassis from scratch, I will choose a suitable donor and rebody it, transplant engine and gearbox, rework suspension, brakes etc. I feel this will be easier, safer and afford me some level of "factory build" standard. I don't want it to look, feel or drive like a cheap kitcar. So by using a donor platform, something with already decent handling for example, I will also have the electrics, isolation, rigidity etc already figured out.

I have a few ideas for platforms, engines etc. But before I would like to make sure this is an ok type of project to carry on here. I don't mean to step on anybody's toes or anything. Since this is not your normal build thread where people are already building it. It will start as a place to ask for opinions and guidance and will morph into the build thread as I get the donor platform, start stripping it and building the project.

I thought about looking for a Kitcar forum first. But I then came accross this forum and thought that as it is not a kitcar but more of a custom car or coachbuild type of deal, this place might be better suited than a kitcar forum. :)

Please let me know if I'm right. ;)

Thanks for reading.

Welcome home!

I want to be sure you are aware of these two inspirations...

Midlana

ExoTruck

More inspiration. The Volvo p1800 & Miata mashup

John Welsh said:

Welcome home!

Well, thanks! :)

In reply to Stz2020 : 

You're in the right place for this madness. Welcome.

If you could start with a body on frame car, there might be some advantages to implementing your plan.

Sounds like a FRS/BRZ or rx8 would make a decent jumping off point

A rx8 is just a long Miata afterall

See also: Corvette rebody

John Welsh said:

Welcome home!

I want to be sure you are aware of these two inspirations...

Midlana

ExoTruck

 

More inspiration. The Volvo p1800 & Miata mashup

Thanks for the inspiration. :)

Indy-Guy said:

In reply to Stz2020 : 

You're in the right place for this madness. Welcome.

If you could start with a body on frame car, there might be some advantages to implementing your plan.

Thanks!

Yes that would make things easier. But that would also mean a much older car. I wanted a more contemporary ride. Or am I wrong? What was the last body on frame sports car?

gumby said:

Sounds like a FRS/BRZ or rx8 would make a decent jumping off point

A rx8 is just a long Miata afterall

See also: Corvette rebody

Thanks.

I have thought of the BRZ. It has the correct proportions for sure. Although still a bit larger than I wanted.And since I was thinking of a lower front end, it will mean totally reworking the front frame.

The less frame cutting I have to do the better for many reasons. So it would probably be easier to find a donor which doesn't have that much structure at the front. Like a BMW Z car for example. It being a convertible, I could also add any shape of roof I wanted. As it's already legal to drive as a convertible, adding a roof would only make it more rigid right. With a fixed roof car it would mean I would either have be happy with the roof  or hack it, which again is not the best. It would be messing too much with the chassis integrity.

But at least the BRZ has the correct proportions I'm looking for. The RX8 doesn't. Since I'm looking for a fastback design, the RX8 would again mean hacking the roof. :)

The Corvette as a donor is again a bit larger than what I wanted.

Main issue with a convertible is when adding a custom roof, the side window sealing and isolation etc. When even commercially produced hard tops leak sometimes, it's clear it's not that easy. Doing a roof transplant, like in the Corvette C5 thread makes it easier since a custom roof isn't needed. But then the side windows will not fit. I guess it's a matter of choosing your compromises. :)

Welcome to the game. It can be fun and I guarantee that if you start the project, you will be a wiser, more skilled, person at the end no matter how it turns out.

The P1800 wagon linked above was my first effort and while I did not arrive here with much more of a plan than "Hold my beer and watch this" it seems to have evolved down a road that has many of the same requirements that you state.

My first and only responsible-adult advice is to not do this. You are trying to out-doo factory engineering and it aint gonna happen. Especially on a first effort. And if you want a car that is actually compelling to drive it is going to take a lot of time and $$$. The difference between a one-use challenge car and a real car that you and your significant other will want to drive on long trips is huge. Your instinct to try and use as much factory engineering as possible is a good one. 

I don't really see your vision as described above: Are you planning on doing a chassis swap into a different body like I did? Are you wanting a custom chassis under a classic body? Bit if column A and bit of column B?

I drive an FRS and it is an awesome chassis. V8 swap into this car would be fun but CAN buss complicates stuff

I have an MGB GT and originally planned the project around that. Some nice repowered MGBs roam the streets and they are dirt cheap to buy.

The 240Z is a classic form that fits your stated requirements.

I am assuming that you dont want to bash out and entirely new and original body for this car?

Pete

NOHOME said:

Welcome to the game. It can be fun and I guarantee that if you start the project, you will be a wiser, more skilled, person at the end no matter how it turns out.

The P1800 wagon linked above was my first effort and while I did not arrive here with much more of a plan than "Hold my beer and watch this" it seems to have evolved down a road that has many of the same requirements that you state.

My first and only responsible-adult advice is to not do this. You are trying to out-doo factory engineering and it aint gonna happen. Especially on a first effort. And if you want a car that is actually compelling to drive it is going to take a lot of time and $$$. The difference between a one-use challenge car and a real car that you and your significant other will want to drive on long trips is huge. Your instinct to try and use as much factory engineering as possible is a good one. 

I don't really see your vision as described above: Are you planning on doing a chassis swap into a different body like I did? Are you wanting a custom chassis under a classic body? Bit if column A and bit of column B?

 

I drive an FRS and it is an awesome chassis. V8 swap into this car would be fun but CAN buss complicates stuff

I have an MGB GT and originally planned the project around that. Some nice repowered MGBs roam the streets and they are dirt cheap to buy.

The 240Z is a classic form that fits your stated requirements.

I am assuming that you dont want to bash out and entirely new and original body for this car?

 

Pete

 

 

 

 

Hi! Thanks for the reply.

Yes, the idea is exactly that. As you put it, to bash out and entirely new and original body for this car. :)

Well, if starting from a fixed top, I would not mind keeping the original roof for simplicity and safety.

So in answer to your question here: "Are you planning on doing a chassis swap into a different body like I did? Are you wanting a custom chassis under a classic body? "

Neither. The idea is to rebody an existing frame with an original design. ;) As well and installing a different engine and gearbox.

I totally agree with you about being insane to try to out-doo factory engineering. So I won't. ;). This is why I want to keep basically the full internal structure and engineering. So apart from the new body, it would be basically the same as a "regular" engine swap, or upgrading brakes etc on any car to add performance. ;)

I hope I have managed to make my goals a little more clear now. But if not, please ask away. :)

By the way, your P1800 project looks great! I did cheat and skipped to the end. But I plan on reading the full thread as soon as I have a chance. I'm sure I can learn a lot from it. :)

In reply to Stz2020 :

Then I highly recommend the FRS chassis as a starting point.The engine will take pretty much anything you can think of from 2jz to Coyote modular engines.

The one place you can get away with your own plan is in the re-wiring. As long as you dont need factory levels of electrical sophistication and nannies, doing a complete analog re-wire with an aftermarket harness is not a huge deal or penalty as far as driving is concerned. Body-module computers are the bane of engine swaps.  Standalone engine management and aftermarket gauges are the way forward. 

Pete

NOHOME said:

In reply to Stz2020 :

Then I highly recommend the FRS chassis as a starting point.The engine will take pretty much anything you can think of from 2jz to Coyote modular engines.

The one place you can get away with your own plan is in the re-wiring. As long as you dont need factory levels of electrical sophistication and nannies, doing a complete analog re-wire with an aftermarket harness is not a huge deal or penalty as far as driving is concerned. Body-module computers are the bane of engine swaps.  Standalone engine management and aftermarket gauges are the way forward. 

 

Pete

Yes. It is indeed a good platform. But it has the disadvantages I listed above. :)

In terms of engine swap, I guess the older the donor platform the easier it will be. But I'm trying to stay within about 15 years old give or take.  To keep the electronics headaches lower in the swap as well as to avoid some of the thing I dislike and which have become the normal in new cars. But don't want to go older because chassis design came a long way too.

As a way to try to get around the electronic headaches in the swap, I was thinking of possibly transplanting more than just the engine.  For example, let's say that I would take the BRZ as a donor platform and would like to transplant a Mercedes engine in it.  I would have all sorts of electronics compatibility problems. But what if I stripped the BRZ to the basics, leaving mainly just the rolling frame/chassis with suspension, brakes, wheels etc from the mechanics, plus the interior installations? And then transplanted the whole heart of the Mercedes. Meaning the ECU and electronics etc. Does it care which metal frame it is riding in? Would it know? What would still be a problem? What would have to come in along with the engine? What modules etc apart from the obvious ECU? I hope it's clear where I'm coming from here. I'm just trying to get around the compatibility problems.

A stand alone engine management is of course an option. But not every engine has one available for it. So it will limit the engine to the widely swapped ones.

Of course, doing it this way I would have to have 2 donor cars. One for the platform/frame/chassis and another for the engine. If I'm transplanting the whole thing from the engine car, having a full car as a donor, possibly crashed, would be simpler.

Does that line of thought make sense at all to those with more knowledge in the subject? Is it worth pursuing? I'm sure with a new car that would be most likely impossible as they have sensors for everything. But in a mid to late 2000s car it might be possible.

The good old days where the biggest problem in an engine swap was to figure if the bay was large enough and fabricate mounting points were the days. :)

In reply to Stz2020 :

Yeah, your brain is traveling down all the right roads here and you do have some coin-flip decisions to make. I agree with your full electrical system adoption and integration into the project; the more intact the better. Sounds easy if you say it real fast, but doubt it will be that simple as sensor cross-over might not be the same for al parties. Solving this stuff has to be half the fun.

You are going to be doing a E36 M3load of stuff for the first time. A such, it is not realistic to get everything right on the first try. I highly advise spending the time and money to make stuff better than "Good enough" if you want a good result.

Don't underestimate how much room three dis-assembled cars require. Plus you are going to be needing the space to build the body.

Metal or composite body?

By the way, what I said about beating factory engineers at their game? I kinda feel that way with the designers also, hence why I always build my projects around a classic body-shell that I fall in love with and try to keep it as close to stock as possible. Looking forward to a sketch of what is in your head.

Here is another thread that might be of interest, Person is re-bodying a Volvo P1800 into a Ferrari style body and swapping in a V12 engine. Has not updated his thread here for a while, but I know it is ongoing even if not posted on other forums.

https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/volvo-p1800-to-approximation-of-a-ferrari-275gtb-s/129937/page1/

Pete

I'm absolutely with you about striving to go beyond just "Good enough" . :)

But why space for 3 cars? 2 cars really. Frame donor car and engine donor car. ;)

About the body I will build it directly over the frame donor.

I feel you about trying to beat pro designers. But at least on this side it's highly subjective. I only need to please myself. ;)

But with the engineering I have to please the laws of physics. So I'm not even trying and will stick as closely as I can to the factory engineering for the important parts.

I have a very good idea about the design I want.  But I need to iron out the technical kinks first as that might dedicate parts of the design.

My first job is to figure what modules and parts I need to carry on with the engine, in order to use the same electronics from the engine donor in the new car. It seems if I carry the ABS module I could have ABS in the new car. The computer doesn't seem to care what discs, calipers or even brake lines it's on. Well, at least not with ABS of this era (2000-2010) anyway. This is the info I'm finding so far. But I would love for more people to jump in and help on that. :)

Also it seems carrying over the ABS module might bring some other things like traction control and even stability control etc.

It seems I might also have to carry on the gauges of the engine donor, if I want it all to work properly. But then I need to recalibrate speedometer, tacho and possibly fuel gauge if I end up using a different gas tank? It used to be easy. But nowadays with more modern cars, I'm not sure. Any ideas?

The airbag seems to be a separate thing and I might be able to just keep the one in the frame donor car.

Since the car will have a manual, I guess no transmission module is needed. So is that it? The ECU and ABS module which I need to carry on from engine donor to new car? Plus potentially the gauges.

Thanks for the link to the thread. Very interesting. So many interesting projects to keep track of. :)

Here is some more inspiration. This is the builders third ground up build.