Fiat Coupe, Lexus V8 and a Mazda MX5
Discussion
Evoluzione said:
Interesting project, I suspect it will be heavier overall when it's done and whether the front to rear ratio changes much remains to be seen I suppose.
If the weight is an issue i'd be putting the contents of both the original 20vt then the lexus/MX5 onto a trailer and visiting the local weighbridge a couple of times, but I suspect it's not about that
Personally i'd get the rear subframe/suspension, driveshafts and diff from a Dedra integrale or Q4 as it bolts straight on, they have either a torsen or a lockable open diff so you could go drifting (yeehah!) but that's just me.
Looking forward to seeing the progress.
I did think of the Dedra set up to begin with. But finding the bits is not easy compared to bits I can find for pennies over here. If the weight is an issue i'd be putting the contents of both the original 20vt then the lexus/MX5 onto a trailer and visiting the local weighbridge a couple of times, but I suspect it's not about that
Personally i'd get the rear subframe/suspension, driveshafts and diff from a Dedra integrale or Q4 as it bolts straight on, they have either a torsen or a lockable open diff so you could go drifting (yeehah!) but that's just me.
Looking forward to seeing the progress.
Plus I know the Toyota parts can take serious power and abuse.
The weight will be an issue and I'm having to be mindful of this through the build.
The standard coupe weighs in at 1360kg (weighed on the weigh bridge at work)
The lexus engine and auto box comes in at 300kg fully dressed with air con compared to the 270 odd kg of the coupe drive train.
Ideally I'm aiming for a total weight of 1260kg. Whether or not I make that is a different thing
I have some crane scales so I'll be weighing various bits as they go on.
As yet nothing has been cut. I've just been taking measurements and assessing the fitment issues.
I know how I want it to go together. I'm heading off on holiday for a fortnight so hopefully I'll be able to get through the IVA manual and see if I can come close to getting the car road legal.
Then when I'm back I'll spend some time stripping the practice vessel.
Rather than hacking up a nice coupe I'll be mocking the thing up using a Fiat Marea, the floorpan is the same as the coupe with identical engine bays so it's ideal to practice with.
I know how I want it to go together. I'm heading off on holiday for a fortnight so hopefully I'll be able to get through the IVA manual and see if I can come close to getting the car road legal.
Then when I'm back I'll spend some time stripping the practice vessel.
Rather than hacking up a nice coupe I'll be mocking the thing up using a Fiat Marea, the floorpan is the same as the coupe with identical engine bays so it's ideal to practice with.
The main reason is the mx5 suspension is so well packaged, it doesn't come with scene tax prices and is more suited to the project.
I've had lots of experience with s body cars and although there are loads of aftermarket options for drifters, the design is very bulky in comparison.
I'll not discount it though as it was one of my earlier choices.
I've had lots of experience with s body cars and although there are loads of aftermarket options for drifters, the design is very bulky in comparison.
I'll not discount it though as it was one of my earlier choices.
Escy said:
I still don't understand the benefit of using MX5 parts to base this project around? To do what you said, you need to fit the Lexus diff case into the MX5 subframe and get custom driveshafts. I'd personally be going for a 200SX rear end, lots of options for aftermarket differentials and they can't be much wider than the MX5 stuff, i've seen them fitted under AE86's.
Whilst on holiday with nothing to do but cogitate abs ponder. Since I'm wanting to use the Toyota diff shafts and brakes it really does make sense to use suspension and uprights that isn't going to cost a fortune to make work.
I got to looking at the lexus complete rear end as is.
It's still double wishbone, all adjustable ish, it's a similar design to the supra set up and, it's free so no machining making the brakes and hubs fit the mazda parts.
The only thing left to work out by not using the mx5 rear floor / chassis is the nice fuel tank set up.
But the lexus also has its stock tank above the rear subframe.
It will make things much cheaper and save time.
All quiet on the Frankenstein front at the moment. Since the Lexus has just been through another test I've been doing some bits and bobs on it.
Despite the vastness of the LS400 there really isn't any room under the bonnet for throwing a turbo In there. And as the engine is going to be turbocharged in the Fiat I made a start on that while I'm waiting for my workshop to free up a little.
So no room up front for a turbo means a little out of the box thinking. All reasoning states that a turbo should be mounted as close to the engine as possible for the obvious reasons, and that's the general accepted route. A group of open minded individuals in the good old USA decided that their corvettes needed turbocharging and as there was no space next to the engine they put two turbos where the rear silencers used to live. Job done.
Yes it sounds ridiculous and the laws of physics say it shouldn't work. But it does, kinda. Well enough to make a decent increase of power. So this is the route m taking with the Lexus. According to many folks on various Facebook groups devoted to the Lexus V8, they can take a small amount of boost without having to spend millions on management.
The secret of getting a turbo to work "at the rear" is all about flow and pipe sizing. I watched a build thread of an E55 AMG with a similar set up and basically I'm ripping that off.
To get the hot gasses to a turbo so far away from the engine means keeping the exhaust small, simple and hot.
Small, means keeping the general pipe sizing pretty much stock size. Sol I'll be using 63mm piping from the manifolds directly to the turbo.
Simple, means no restrictions. So directly from the manifolds the exhaust will join via a Y pipe and head directly to the turbo with no cats or silencers in the way.
Hot, this is the tricky bit. The exhaust will be wrapped and then extra heat shielding added in a vain attempt to decrease air flow on it.
Now this is a budget experiment as I've the main project plus my other Fiat Coupe to be getting on with, so this is all being done on the cheap. This includes the turbo which is from a nice man in China. I know people who've had bad experiences with Chinese turbos and others who say they've lasted well.
If it lasts six months it's still cheap enough to be a consumable item.
The turbo itself bases itself on a GT35. Using a T3 turbine with a relatively small ar63 size housing (to help with spool up) and ar70 sized compressor side.
The exhaust makes its way into the turbo via a 2.5" V band to T3 adapter. The exhaust side uses a 3" V band which I'll mount another Y pipe, one pipe goes on to two silencers and tailpipe, the other will have a 3" butterfly which when closed diverts the exhaust through the silencers, but when open it flows the exhaust straight to a tailpipe.
This way I can have a go mode and a shhhh mode.
The turbo itself will be mounted in the boot. Or more specifically a section of boot floor cut out in front of the spare wheel well so it sits just behind the rear axle.
It will be fed it's life blood of oil not from the engine, but via a separate SCOS, Self Contained Oiling System. I made that up isn't it great!
So this is really the sump from a Fiat coupe complete with its oil pump (you gotta use what you have lying around) which will be driven by a wiper motor via two sprockets and a chain.
The beauty of this sump and pump set up is its all set up for the turbo. I can control the oil pressure, have the perfect oil return path (which has in built cooling) and also incorporate a filter.
The sump will be plated over on top, the turbo will sit in a cradle on top of that and the whole hint will be mounted on its own cradle via exhaust hangers (four srrong ones)
Something like this, but the turbo will be higher up and maybe further over depending on pipe routing. I know it's upside down but it needs stripping and sorting out anyway yet.
Now I know everyone is thinking about lag. It's generally the first thing that gets thrown around when anyone mentions rear mounted turbos. The ones I've seen and researched have worked really well, some have been total failures but if it's done right it does work without huge lag issues.
The piping from the turbo to inlet manifold will also be 63mm that sounds quite big but you've got to think about how much air this V8 will consume.
To start with I'll just be going directly to the inlet manifold, they say running the charge pipe along the bottom of the car provides an intercooling effect, I'm not 100% sold on that idea and I may make up some kind of charge cooler like the V8 merc rear mount turbo used.
I only want to run low boost with this and the whole thing is to see what kind of results I get before thinking about building a similar (but twin) set up in the Fiat Coupe V8 albeit mounted in front of the rear axle.
The current Lexus V8 has done 135k miles and is in fine shape with FSH. I plan on replacing the distributor caps, rotor arms and plug leads as well as fitting some cooler spec plugs, new leads and a rising rate fuel pressure regulator fed by a Walbro in tank pump, I'll also be adding a wideband and egt gauge to monitor fuelling.
Do to the fact that the turbo will run much cooler than intended this may help longevity and another by product of the reduced heat is massively reduced compressor heat which has got to be good and should negate the need for turbo water cooling. Also being a separate oil supply there's no engine heat adding to the oil heating.
Without a turbo sat next to it the engine and bay will be much cooler and a much more pleasant place to be, a new breather system will be made (again from bits of Fiat Coupe catch tank and breather system) and the cluctch fan will make way for and electric unit that can be pre set.
I think that's covered most bases and I'm just waiting for postman Pat to start delivering parts of the exhaust and other associated parts.
The turbo landed yesterday but working away means I won't get to covet it till Tuesday. Like I said this isn't a mega serious attempt at making power, just an experiment done as cheaply as possible.
It is possible to just flip the Lexus exhaust manifolds around to face forward, ibut that means losing things like air con and moving alternator and PAS mounts and having the car off the road.
This way I can keep running it (albeit loud) while I build the system in the car.
I'd like to do a power run before and after for giggles.
In the mean time I'm getting the welding done on my yellow Fiat Coupe and then putting an engine in it. (I rescued the shell from being scrapped to put all the running gear from the red one in) I've also got some other cars to to other work on to clear space in the workshop, but more updates will be forth coming.
Despite the vastness of the LS400 there really isn't any room under the bonnet for throwing a turbo In there. And as the engine is going to be turbocharged in the Fiat I made a start on that while I'm waiting for my workshop to free up a little.
So no room up front for a turbo means a little out of the box thinking. All reasoning states that a turbo should be mounted as close to the engine as possible for the obvious reasons, and that's the general accepted route. A group of open minded individuals in the good old USA decided that their corvettes needed turbocharging and as there was no space next to the engine they put two turbos where the rear silencers used to live. Job done.
Yes it sounds ridiculous and the laws of physics say it shouldn't work. But it does, kinda. Well enough to make a decent increase of power. So this is the route m taking with the Lexus. According to many folks on various Facebook groups devoted to the Lexus V8, they can take a small amount of boost without having to spend millions on management.
The secret of getting a turbo to work "at the rear" is all about flow and pipe sizing. I watched a build thread of an E55 AMG with a similar set up and basically I'm ripping that off.
To get the hot gasses to a turbo so far away from the engine means keeping the exhaust small, simple and hot.
Small, means keeping the general pipe sizing pretty much stock size. Sol I'll be using 63mm piping from the manifolds directly to the turbo.
Simple, means no restrictions. So directly from the manifolds the exhaust will join via a Y pipe and head directly to the turbo with no cats or silencers in the way.
Hot, this is the tricky bit. The exhaust will be wrapped and then extra heat shielding added in a vain attempt to decrease air flow on it.
Now this is a budget experiment as I've the main project plus my other Fiat Coupe to be getting on with, so this is all being done on the cheap. This includes the turbo which is from a nice man in China. I know people who've had bad experiences with Chinese turbos and others who say they've lasted well.
If it lasts six months it's still cheap enough to be a consumable item.
The turbo itself bases itself on a GT35. Using a T3 turbine with a relatively small ar63 size housing (to help with spool up) and ar70 sized compressor side.
The exhaust makes its way into the turbo via a 2.5" V band to T3 adapter. The exhaust side uses a 3" V band which I'll mount another Y pipe, one pipe goes on to two silencers and tailpipe, the other will have a 3" butterfly which when closed diverts the exhaust through the silencers, but when open it flows the exhaust straight to a tailpipe.
This way I can have a go mode and a shhhh mode.
The turbo itself will be mounted in the boot. Or more specifically a section of boot floor cut out in front of the spare wheel well so it sits just behind the rear axle.
It will be fed it's life blood of oil not from the engine, but via a separate SCOS, Self Contained Oiling System. I made that up isn't it great!
So this is really the sump from a Fiat coupe complete with its oil pump (you gotta use what you have lying around) which will be driven by a wiper motor via two sprockets and a chain.
The beauty of this sump and pump set up is its all set up for the turbo. I can control the oil pressure, have the perfect oil return path (which has in built cooling) and also incorporate a filter.
The sump will be plated over on top, the turbo will sit in a cradle on top of that and the whole hint will be mounted on its own cradle via exhaust hangers (four srrong ones)
Something like this, but the turbo will be higher up and maybe further over depending on pipe routing. I know it's upside down but it needs stripping and sorting out anyway yet.
Now I know everyone is thinking about lag. It's generally the first thing that gets thrown around when anyone mentions rear mounted turbos. The ones I've seen and researched have worked really well, some have been total failures but if it's done right it does work without huge lag issues.
The piping from the turbo to inlet manifold will also be 63mm that sounds quite big but you've got to think about how much air this V8 will consume.
To start with I'll just be going directly to the inlet manifold, they say running the charge pipe along the bottom of the car provides an intercooling effect, I'm not 100% sold on that idea and I may make up some kind of charge cooler like the V8 merc rear mount turbo used.
I only want to run low boost with this and the whole thing is to see what kind of results I get before thinking about building a similar (but twin) set up in the Fiat Coupe V8 albeit mounted in front of the rear axle.
The current Lexus V8 has done 135k miles and is in fine shape with FSH. I plan on replacing the distributor caps, rotor arms and plug leads as well as fitting some cooler spec plugs, new leads and a rising rate fuel pressure regulator fed by a Walbro in tank pump, I'll also be adding a wideband and egt gauge to monitor fuelling.
Do to the fact that the turbo will run much cooler than intended this may help longevity and another by product of the reduced heat is massively reduced compressor heat which has got to be good and should negate the need for turbo water cooling. Also being a separate oil supply there's no engine heat adding to the oil heating.
Without a turbo sat next to it the engine and bay will be much cooler and a much more pleasant place to be, a new breather system will be made (again from bits of Fiat Coupe catch tank and breather system) and the cluctch fan will make way for and electric unit that can be pre set.
I think that's covered most bases and I'm just waiting for postman Pat to start delivering parts of the exhaust and other associated parts.
The turbo landed yesterday but working away means I won't get to covet it till Tuesday. Like I said this isn't a mega serious attempt at making power, just an experiment done as cheaply as possible.
It is possible to just flip the Lexus exhaust manifolds around to face forward, ibut that means losing things like air con and moving alternator and PAS mounts and having the car off the road.
This way I can keep running it (albeit loud) while I build the system in the car.
I'd like to do a power run before and after for giggles.
In the mean time I'm getting the welding done on my yellow Fiat Coupe and then putting an engine in it. (I rescued the shell from being scrapped to put all the running gear from the red one in) I've also got some other cars to to other work on to clear space in the workshop, but more updates will be forth coming.
Edited by Steve20vt on Saturday 13th August 09:36
Edited by Steve20vt on Monday 15th August 08:21
Edited by Steve20vt on Monday 15th August 08:25
It may seem that way, but this isn't a quick project. The LS400 had a fresh mot 4 weeks ago and as I have another V8 in the garage to use for mocking up purposes I'll still be using the LS400 for some time to come.
The next jobs on the V8 coupe are
Cutting up and disposing of the unwanted parts of the MX5
Breaking my Fiat Marea estate, and using that as a practice mule for grafting the MX5 front cross member into and mocking up the V8 position.
As the Marea shares its platform with the coupe it's an ideal practice tool, it saves me making mistakes when it comes to taking a grinder to the coupe.
As I'm only mocking up the engine bay / bulkhead I only need the front half of the Marea.
As for doing the rear mount turbo on the Lexus, it's also a trial run as I'd like to run a similar set up on the V8 coupe. As it will be a two seater it would be interesting and cool to have shiny engine stuff on show in the rear and also further improve weight distribution.
The battery and electric PAS will also be mid / rear mounted.
So there's lots to be getting on with before I actually pull the engine out of the Lexus.
As she stands at present.
The next jobs on the V8 coupe are
Cutting up and disposing of the unwanted parts of the MX5
Breaking my Fiat Marea estate, and using that as a practice mule for grafting the MX5 front cross member into and mocking up the V8 position.
As the Marea shares its platform with the coupe it's an ideal practice tool, it saves me making mistakes when it comes to taking a grinder to the coupe.
As I'm only mocking up the engine bay / bulkhead I only need the front half of the Marea.
As for doing the rear mount turbo on the Lexus, it's also a trial run as I'd like to run a similar set up on the V8 coupe. As it will be a two seater it would be interesting and cool to have shiny engine stuff on show in the rear and also further improve weight distribution.
The battery and electric PAS will also be mid / rear mounted.
So there's lots to be getting on with before I actually pull the engine out of the Lexus.
As she stands at present.
Edited by Steve20vt on Monday 15th August 08:18
Some photos of the Fiats I have.
This Broom yellow Coupe was going to be scrapped, it had the later desirable "plus" interior and a blown engine so the owner had partially stripped it.
I got it with no interior, engine / box, brakes, suspension, wheels or a sunroof and some of the engine bay and dash looms had been cut.
As I had all of the above parts removed from my red Coupe it seemed a sensible idea to fit them into the yellow one.
Before anyone says, it's easier for me to do it this way as the red one is stripped totally, as in there's no wiring or sound proofing, dash (which is a right pain to get in & out) or pedals.
Plus it's got more rust.
The emptiness of the red coupe engine room.
It's not that pretty in real life, just wet from washing.
And here the old Marea Weekend 2.4 HLX, now quite rare. I think there's only around 15 left on the road in the uk.
This one is rotten as a pear underneath and stood me at about £200
It was a great banger for the money and provided me with a years cheap motoring, plus it went pretty well with one of those cheap diesel tuning boxes on it, and had a coupe front roll bar and intercooler as well as the wheels.
The Fiat Coupe was based originally on the Tipo chassis. Enabling Fiat to mass produce several different cars on the same platform and wheelbase.
For Fiat it was the Tipo, Marea, Bravo/Brava, Coupe and albeit a different chassis but using the same components the wonderful Fiat Multipla. And for Alfa Romeo it was the 155,146 while Lancia used it for the Dedra.
Incidentally the Coupe was designed by an American chap named Chris Bangle. Who later went on to work for BMW.
The Couoe was the last car he actually designed personally.
The interior was designed by Pininfarina and the cars were all built not at Fiat but at Pininfarinas factory which goes some way into why the Coupe was put together in a higher quality fashion compared to say a Fiat Bravo.
It could have looked quite different!
Here's my inspiration, the Fiat 8V
They wanted to call it the Fiat V8 but at the time Ford had a copyright on the name.
Here is the principal of the rear mounted turbo.
In 1941 US fighter planes struggled with power at altitude, and by Installing this whopping great turbine they could get the stock power back at 20,000 feet.
At the time it was called the turbosupercharger.
In the 60s Oldsmobile introduced the first turbocharged all alloy V8, the Rocket Jetfire. It's turbo was mounted directly on the inlet manifold and had to use water / meth injection to stop it blowing up.
They called it "Jetfuel" although as you can imagine once it ran out people didn't fill it up so a butterfly restricted the boost pressure to prevent damage.
The Chevrolet corvair spider was the first production turbocharged car released only a few weeks before the Oldsmobile.
Pointless info but I find it cool.
This Broom yellow Coupe was going to be scrapped, it had the later desirable "plus" interior and a blown engine so the owner had partially stripped it.
I got it with no interior, engine / box, brakes, suspension, wheels or a sunroof and some of the engine bay and dash looms had been cut.
As I had all of the above parts removed from my red Coupe it seemed a sensible idea to fit them into the yellow one.
Before anyone says, it's easier for me to do it this way as the red one is stripped totally, as in there's no wiring or sound proofing, dash (which is a right pain to get in & out) or pedals.
Plus it's got more rust.
The emptiness of the red coupe engine room.
It's not that pretty in real life, just wet from washing.
And here the old Marea Weekend 2.4 HLX, now quite rare. I think there's only around 15 left on the road in the uk.
This one is rotten as a pear underneath and stood me at about £200
It was a great banger for the money and provided me with a years cheap motoring, plus it went pretty well with one of those cheap diesel tuning boxes on it, and had a coupe front roll bar and intercooler as well as the wheels.
The Fiat Coupe was based originally on the Tipo chassis. Enabling Fiat to mass produce several different cars on the same platform and wheelbase.
For Fiat it was the Tipo, Marea, Bravo/Brava, Coupe and albeit a different chassis but using the same components the wonderful Fiat Multipla. And for Alfa Romeo it was the 155,146 while Lancia used it for the Dedra.
Incidentally the Coupe was designed by an American chap named Chris Bangle. Who later went on to work for BMW.
The Couoe was the last car he actually designed personally.
The interior was designed by Pininfarina and the cars were all built not at Fiat but at Pininfarinas factory which goes some way into why the Coupe was put together in a higher quality fashion compared to say a Fiat Bravo.
It could have looked quite different!
Here's my inspiration, the Fiat 8V
They wanted to call it the Fiat V8 but at the time Ford had a copyright on the name.
Here is the principal of the rear mounted turbo.
In 1941 US fighter planes struggled with power at altitude, and by Installing this whopping great turbine they could get the stock power back at 20,000 feet.
At the time it was called the turbosupercharger.
In the 60s Oldsmobile introduced the first turbocharged all alloy V8, the Rocket Jetfire. It's turbo was mounted directly on the inlet manifold and had to use water / meth injection to stop it blowing up.
They called it "Jetfuel" although as you can imagine once it ran out people didn't fill it up so a butterfly restricted the boost pressure to prevent damage.
The Chevrolet corvair spider was the first production turbocharged car released only a few weeks before the Oldsmobile.
Pointless info but I find it cool.
Yes I could put a turbo or two up front, but it means making manifolds, losing air con, moving the battery, making new alternator brackets etc etc.
It does look nice in that pic but it's really not that good.
The drivers side has been very badly repainted and the lacquer is all but gone.
It's had a knock on the drivers side front at some point too.
Apart from that is been well looked after. Every service fully documented.
The engine is the later skinny rods type and only good for about 400bhp unopened.
Whereas I have a rebuilt big rod pre 91 engine ready to swap all the bits onto when I'm ready.
I've almost got everything together to get on with the turbo so hopefully in a couple of weeks I'll have something to report on.
In the mean time I'm starting to strip the practice fiat so I can begin mocking up the v8 in ther .
It does look nice in that pic but it's really not that good.
The drivers side has been very badly repainted and the lacquer is all but gone.
It's had a knock on the drivers side front at some point too.
Apart from that is been well looked after. Every service fully documented.
The engine is the later skinny rods type and only good for about 400bhp unopened.
Whereas I have a rebuilt big rod pre 91 engine ready to swap all the bits onto when I'm ready.
I've almost got everything together to get on with the turbo so hopefully in a couple of weeks I'll have something to report on.
In the mean time I'm starting to strip the practice fiat so I can begin mocking up the v8 in ther .
The espace isn't mine. Just part of what inspired me with this project.
The Peugeot you speak of is in practical performance car. July 2014 in fact. It belongs to Julian of Balance motorsport.
https://balancemotorsport.co.uk/project-cars
It worked really well in the little 1.9 engine. The majority of rear mount turbos are on big capacity V8 engines where the sheer amount of gas flow means it can compete with conventional systems.
Imagine what they thought back in the day when GM started bolting these tiny turbos directly to the engine?
"What putting a turbosupercharger so close to that source of heat"
It probably sounded as crazy back then as rear mounting does now.
Don't fight it, let's just see how it goes. If it works as well as I've heard it'll have been a cheap way to a few extra ponies.
It's basically fitting a different exhaust with a turbo bolted to it and a pipe back the inlet. Job done *
The Peugeot you speak of is in practical performance car. July 2014 in fact. It belongs to Julian of Balance motorsport.
https://balancemotorsport.co.uk/project-cars
It worked really well in the little 1.9 engine. The majority of rear mount turbos are on big capacity V8 engines where the sheer amount of gas flow means it can compete with conventional systems.
Imagine what they thought back in the day when GM started bolting these tiny turbos directly to the engine?
"What putting a turbosupercharger so close to that source of heat"
It probably sounded as crazy back then as rear mounting does now.
Don't fight it, let's just see how it goes. If it works as well as I've heard it'll have been a cheap way to a few extra ponies.
It's basically fitting a different exhaust with a turbo bolted to it and a pipe back the inlet. Job done *
- plus a few little odds and sods
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