DIY mid engined car
Discussion
Max_Torque said:
The key, is to get the engine / transmission as LOW as possible across the back. The FWD suspension kinematics won't be ideal, because they will be set for power on dynamic toe (ie oversteer!) when you use them at the back, but make sure you have a low powertrain CofG, stiff mountings (enigne mounts and subframes etc) and spend a bit of time playing with the tracking etc (castor/camber/toe/offset) and you can do a reasonable job in your shed. The two hurdles tend to be:
1) What to do with the steering rack. If you replace it, make very very sure you are not introducing ANY bumpsteer
2) The gear shift. Getting a link to the back of the trans, now facing out the back of the car, and away from the gearstick way up front can introduce a pretty un-inspiring gear change.....
i built a rear mid transverse engine Volvo 480 way back in 1996 (eek, that's 21 years ago!!) but i didn't use fwd suspension in order to avoid some of those issues.
With my 6C Sprint I kept the steering rack, but locked it, so bumpsteer was minimised. The gear change from the gearbox was altered to run forwards and a rod with U/J went to the gear lever with another fixed rod to the engine - so the change was very similar to the original 164. The handling was good with minimal roll and it felt like a big go-kart!
1) What to do with the steering rack. If you replace it, make very very sure you are not introducing ANY bumpsteer
2) The gear shift. Getting a link to the back of the trans, now facing out the back of the car, and away from the gearstick way up front can introduce a pretty un-inspiring gear change.....
i built a rear mid transverse engine Volvo 480 way back in 1996 (eek, that's 21 years ago!!) but i didn't use fwd suspension in order to avoid some of those issues.
With my 6C Sprint I kept the steering rack, but locked it, so bumpsteer was minimised. The gear change from the gearbox was altered to run forwards and a rod with U/J went to the gear lever with another fixed rod to the engine - so the change was very similar to the original 164. The handling was good with minimal roll and it felt like a big go-kart!
Some Gump said:
Ha Ha, that's great. The thing with 4 wheel steering is how to control it. In the 90's? there was at least one Japanese car which had 4 wheel steering. At low speed the rear wheels turn the same way as the front, and at high speed the other way (thus 'following' the radius of the bend).An arguably useful feature, whether your view is the added complexity/cost is worth the benefit. A simpler way is to have the usual rear-wheel set up, which is designed to add a small amount of tow-in to the inner rear wheel and a small amount of toe out to the outer rear wheel as the body rolls during cornering.No benefit at low speed with this simple set up though. The active 4 wheel steer on the Japanese car gave easier parking ability.
If you're thinking of scratchbuilding, or adapting an existing car, rather than using an existing kit car base, then best read up on the IVA test that your new vehicle will need to pass, and consider the criteria in your design process.
https://www.gov.uk/government/uploads/system/uploa...
https://www.gov.uk/government/uploads/system/uploa...
I've just been looking into using the subframe from a mid-rear car instead of trying to adapt a front end steering/suspension setup.
That solves a few problems, no need to mess around fixing the steering arms and the geometry is already set up for the rear end rather than front, and you no longer have to adapt some rear calipers for the handbrake.
This brings up the question of why would you use just the subframe and not the whole car and just do an engine swap instead. There are a couple of advantages the biggest one being space, you have loads more room in the back of a car where a boot and seats would normally be as opposed to a rear engine bay, but the main reason is I just want a project, and the car I've got in mind would be cheap enough to just scrap the entire project and not lose any sleep over the money lost if it didn't go to plan.
That solves a few problems, no need to mess around fixing the steering arms and the geometry is already set up for the rear end rather than front, and you no longer have to adapt some rear calipers for the handbrake.
This brings up the question of why would you use just the subframe and not the whole car and just do an engine swap instead. There are a couple of advantages the biggest one being space, you have loads more room in the back of a car where a boot and seats would normally be as opposed to a rear engine bay, but the main reason is I just want a project, and the car I've got in mind would be cheap enough to just scrap the entire project and not lose any sleep over the money lost if it didn't go to plan.
Here is a photo of an MR2 shell, there is a lot of space behind the seats that you could use if changing the engine.
There are more photos of the shell on this link - http://mr2roc.org/phpBB3/viewtopic.php?f=88&t=...
An MR2 can be had for a few hundred quid. If it was me i'd be using something like that as a base. At least you know it'd handle well.
There are more photos of the shell on this link - http://mr2roc.org/phpBB3/viewtopic.php?f=88&t=...
An MR2 can be had for a few hundred quid. If it was me i'd be using something like that as a base. At least you know it'd handle well.
Fastpedeller said:
Ha Ha, that's great. The thing with 4 wheel steering is how to control it. In the 90's? there was at least one Japanese car which had 4 wheel steering. At low speed the rear wheels turn the same way as the front, and at high speed the other way (thus 'following' the radius of the bend).
Honda did it with the Prelude. It was the other way around to how you describe, the rears turned the opposite way to the front at low speed, making the turning circle much tighter, improving low speed maneuverability. At high speed they turned the same way as the front (albeit to a much lesser degee), making the car very stable, particularly when doing lane-changes. There were other manufacturers who offered it too.
Your idea sounds great. Loads of incredibly skillfulI and creative people have executed such ideas brilliantly.
In the 1970s and 1980s "Cars and Car Conversions," the sublime magazine from Croydon, used to run stories about such things on a regular basis.
One of my favourite items featured a Fiat 500 with a Lancia twin-cam in the back. A man called Andy Burton built an Alfa with a Ferrari engine in the back.[ http://www.alfabb.com/bb/forums/297188-post21.html ] Later he made a 4wd Peugeot 306 with a mid-mounted Cosworth V6. It got banned, I think.
CCC, as it was known, had the most exciting articles by people like Art Marcus, Andy Dawson (Dawson Auto Developments) and Dave Walker (Emerald Engineering.)
A really enjoyable and inspirational madly-missed-monthly.
In the 1970s and 1980s "Cars and Car Conversions," the sublime magazine from Croydon, used to run stories about such things on a regular basis.
One of my favourite items featured a Fiat 500 with a Lancia twin-cam in the back. A man called Andy Burton built an Alfa with a Ferrari engine in the back.[ http://www.alfabb.com/bb/forums/297188-post21.html ] Later he made a 4wd Peugeot 306 with a mid-mounted Cosworth V6. It got banned, I think.
CCC, as it was known, had the most exciting articles by people like Art Marcus, Andy Dawson (Dawson Auto Developments) and Dave Walker (Emerald Engineering.)
A really enjoyable and inspirational madly-missed-monthly.
huckster6 said:
Your idea sounds great. Loads of incredibly skillfulI and creative people have executed such ideas brilliantly.
In the 1970s and 1980s "Cars and Car Conversions," the sublime magazine from Croydon, used to run stories about such things on a regular basis.
One of my favourite items featured a Fiat 500 with a Lancia twin-cam in the back. A man called Andy Burton built an Alfa with a Ferrari engine in the back.[ http://www.alfabb.com/bb/forums/297188-post21.html ] Later he made a 4wd Peugeot 306 with a mid-mounted Cosworth V6. It got banned, I think.
CCC, as it was known, had the most exciting articles by people like Art Marcus, Andy Dawson (Dawson Auto Developments) and Dave Walker (Emerald Engineering.)
A really enjoyable and inspirational madly-missed-monthly.
Best. Magazine. EVER!!!In the 1970s and 1980s "Cars and Car Conversions," the sublime magazine from Croydon, used to run stories about such things on a regular basis.
One of my favourite items featured a Fiat 500 with a Lancia twin-cam in the back. A man called Andy Burton built an Alfa with a Ferrari engine in the back.[ http://www.alfabb.com/bb/forums/297188-post21.html ] Later he made a 4wd Peugeot 306 with a mid-mounted Cosworth V6. It got banned, I think.
CCC, as it was known, had the most exciting articles by people like Art Marcus, Andy Dawson (Dawson Auto Developments) and Dave Walker (Emerald Engineering.)
A really enjoyable and inspirational madly-missed-monthly.
The car I had in mind was an MG ZR using the front subframe/engine/drivetrain from a ZS 180. It may seem an odd choice to some people especially when you can buy something like an MR2 or MX5 for very little money but I want something to do as a project.
You can get a headgasket failure ZR and an MOT fail or rear end damaged ZS for very little money, same applies to a TF rear subframe if going down that route. The MG/R parts bin is quite big and everything is very cheap, so my idea was to build the car to the stage where it "works" with no upgrades, and then if it's succesful start thinking about upgrading the suspension/brakes, more power etc..
It might seem a bit of a strange choice and it's all pie in the sky at the moment but it would be fun to atleast try it, if it fails then it doesn't really matter as the initial cost is only a few hundred quid.
You can get a headgasket failure ZR and an MOT fail or rear end damaged ZS for very little money, same applies to a TF rear subframe if going down that route. The MG/R parts bin is quite big and everything is very cheap, so my idea was to build the car to the stage where it "works" with no upgrades, and then if it's succesful start thinking about upgrading the suspension/brakes, more power etc..
It might seem a bit of a strange choice and it's all pie in the sky at the moment but it would be fun to atleast try it, if it fails then it doesn't really matter as the initial cost is only a few hundred quid.
Good luck with your plan. I found that posting up a build thread gave a lot of support from many different people with good ideas - there will always be some "naysayers/pratts" though! In fact what took the most time was not the basic mechanicals but all the other stuff - especially the electrics......
Been thinking about this a bit more, as I say it'll be a while before anything gets started yet if at all.
Just going over a few things to make sure I haven't missed anything out, I've tried to think of all of the parts that would need to be changed.
First off I'd need a ZR shell, TF rear subframe, and the V6 engine from the ZS.
Strip the ZR down so all the mechanical bits other than the front suspension are off, remove the fuel tank etc.
Take measurements of the rear subframe and work out the area of the ZR floor to be cut out.
Using a TF rear subframe, the drivetrain is straightforward as it's all standard stuff even if swapping the engine so the engine, gearbox, driveshafts, suspension and so on aren't a worry, the only trouble with the TF subframe is that the ZR has a wider track than the TF, and the TF uses an uncommon PCD so some hubcentric adaptors would have to be used to widen the track and give us the usual 4x100 PCD, this also means we could use the ZR brakes which are bigger than the TF's.
Once the subframe and drivetrain/running gear are put together, it would be located into the ZR shell and fixed in place.
Then you're left with all of the extra bits:
Use the original radiator for now just to get things running, run coolant pipes under the car
A new fuel tank would be needed under the bonnet and again new fuel lines
Brakes would be standard parts so a normal process for fitting/bleeding
Fabricate a new exhaust system
Gear linkages from a TF
Speedometer drive from a TF
PAS pipes under the car, or fit an electric PAS pump under the bonnet
Wiring loom
Anything else I have missed? Putting a list together like this makes it far less daunting as you can pick out all of the "easy" jobs, can anyone think of any major hurdles I might have missed?
Just going over a few things to make sure I haven't missed anything out, I've tried to think of all of the parts that would need to be changed.
First off I'd need a ZR shell, TF rear subframe, and the V6 engine from the ZS.
Strip the ZR down so all the mechanical bits other than the front suspension are off, remove the fuel tank etc.
Take measurements of the rear subframe and work out the area of the ZR floor to be cut out.
Using a TF rear subframe, the drivetrain is straightforward as it's all standard stuff even if swapping the engine so the engine, gearbox, driveshafts, suspension and so on aren't a worry, the only trouble with the TF subframe is that the ZR has a wider track than the TF, and the TF uses an uncommon PCD so some hubcentric adaptors would have to be used to widen the track and give us the usual 4x100 PCD, this also means we could use the ZR brakes which are bigger than the TF's.
Once the subframe and drivetrain/running gear are put together, it would be located into the ZR shell and fixed in place.
Then you're left with all of the extra bits:
Use the original radiator for now just to get things running, run coolant pipes under the car
A new fuel tank would be needed under the bonnet and again new fuel lines
Brakes would be standard parts so a normal process for fitting/bleeding
Fabricate a new exhaust system
Gear linkages from a TF
Speedometer drive from a TF
PAS pipes under the car, or fit an electric PAS pump under the bonnet
Wiring loom
Anything else I have missed? Putting a list together like this makes it far less daunting as you can pick out all of the "easy" jobs, can anyone think of any major hurdles I might have missed?
Funnily enough I was looking at MR2 pumps the other day whilst searching how other mid engined cars dealt with power steering, seems a better solution than extra pipes under the car, and one less pulley on the engine.
In my last post I mentioned the TF having a narrower track than the ZR, the difference is about 50mm, is it "safe" to use some 20-25mm hubcentric (spacer) adaptors? It would be ideal to use some adaptors anyway as the PCD is an unusual size, but other than the extra load on the wheel bearings would you be upsetting the handling characteristics at all by simply making up the extra width with spacers and/or wider wheels with different offset?
In my last post I mentioned the TF having a narrower track than the ZR, the difference is about 50mm, is it "safe" to use some 20-25mm hubcentric (spacer) adaptors? It would be ideal to use some adaptors anyway as the PCD is an unusual size, but other than the extra load on the wheel bearings would you be upsetting the handling characteristics at all by simply making up the extra width with spacers and/or wider wheels with different offset?
Good point, I might look into finding a non PAS rack that fits easily but I don't mind keeping the PAS for now.
Does anyone have any input on my last comment about the difference in the track width, and how to go about altering it?
Are 25mm hubcentric adaptors ok? Or would it be better (as an example) to go for some wheels with more offset, so 10-15mm adaptor and 10-15mm offset to give the same overall width.
Edited to add the standard track rear track width of the ZR is 1457, the TF is 1410. Adding 50mm overall width brings that up to 1460 so near enough the same as the standard ZR rear.
However the front track width of the ZR is 1472, so even with the rear track widened to 1460mm it's still 12mm narrower than the front.
I've always been under the impression that on a RWD car it's better for the rear track to be wider than the front, so should I consider widening the rear track a little bit more?
Does anyone have any input on my last comment about the difference in the track width, and how to go about altering it?
Are 25mm hubcentric adaptors ok? Or would it be better (as an example) to go for some wheels with more offset, so 10-15mm adaptor and 10-15mm offset to give the same overall width.
Edited to add the standard track rear track width of the ZR is 1457, the TF is 1410. Adding 50mm overall width brings that up to 1460 so near enough the same as the standard ZR rear.
However the front track width of the ZR is 1472, so even with the rear track widened to 1460mm it's still 12mm narrower than the front.
I've always been under the impression that on a RWD car it's better for the rear track to be wider than the front, so should I consider widening the rear track a little bit more?
Edited by s91 on Saturday 30th September 20:38
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