32 replies to this topic

[matty...]

I would go for the mirage setup to be honest. By mounting the turbo at the rear, it would make a good intercooler setup a pain in the ass to do! By the time you've bought the kit, paid for the pipe work to connect it all up you'd may aswell go for the mirage setup. You also lose power with heat loss between the head and turbo, which along the length of the car would be quite significant! Then you've got issues with the air filter either being underneath the car (amongst all the dirt on the road) or in the boot (if you want to cut the boot floor).

Price it up and see how much it would cost to mount at the back and compare it to the £350 for mirage setup.

[whitebuffalo]

I would think that the rear mounting would allow the charge to cool down during the travel from the turbo to the carburetor negating the need for an intercooler. If an intercooler was desired , then it could be mounted above the transfer case and plumbed from the charge pipe into the cooler then into the carb. The rear mounted turbo does not need heat for it to work, just the exhaust gasses passing through it. Also, found that using the 1.75 tubing will help keep the velocity of the exhaust gasses up and would keep lag down to a minimum.

Still sounds like a black art to me. I am just concerned about keeping the motor alive and don't want to do any damage to it regardless of how the turbo is mounted.

Edited by whitebuffalo, 22 October 2008 - 04:47 PM.

[matty...]

Its true you don't NEED heat for a turbo to work, but with heat loss you also get energy loss, if you lose heat you lose energy! Thats why you want to keep, exhaust manifold lengths to a minimum. You will never be able to cool the air as well with long charge pipe lengths as you can with an IC as you won't have the 'ram air' effect.

Using a smaller bore exhaust will only cause higher exhaust back pressures, which can limit the amount of boost you can use efficiently aswell. Its much simpler to keep to a nice compact setup with a decent IC and you'll be sorted!

[Sam Walters]

Another implication with this is running a feed back towards the engine, unless you’re running it through the car it’s got to be running next to a very hot exhaust.


I have a lack of gaiter over the gear stick on one of my cars. Go over a puddle when it’s wet, you could do your ironing with the amount of steam generated!

[Ethel]

You need as good a pressure differential across the turbo as possible and good gas velocity, to me that means keeping the plumbing close to the diameter of cylinder head ports until after the turbo. I guess you could lag your, very long, manifold to keep the heat in and away from the induction plumbing. Even so, an under bonnet setup sounds easier and more efficient.

[smith1380gt]

The big advantage of this setup is packaging, no need to cut the bulkhead, and the stealth factor. Its true you don't need an intercooler with a rear mounted turbo, as heat is not much of a problem due to the 6 feet of aluminum tubing that the pressurized air is going thru (well exposed to moving airflow). I've heard there is not the lag issue you might expect as well. You don't need a muffler as the turbo is a very efficient noise reducer, and you can keep your standard LCB. You just need an electric oil scavenge pump, and a bunch of tubing.

[matty...]

Forgot to mention about having to run a stupidly long oil pressure feed pipe to the turbo, and the return line would probably need some kind of collection/swirl pot (mounted below turbo as they are gravity drain) with an additional pump to pump the oil back to the front, and back into the engine. Far too many complications and additional cost when you weigh up the "benefits". A mirage manifold or even over the clutch setup would be far better.

When you bear in mind how many times you clip your exhaust on speed bumps, then think you are also going to have a turbo, boost pipe, oil pressure feed, oil return hose, swirl pot + pump, return fuel line, air filter underneath aswell, its asking for trouble. Lol

You will still require some kind of silencer also, as they are still loud even with the turbo fitted.

[1987_ParkLane]

Sounds like a good idea, and looks strangely good.

[AlbertaAMX]

Did you ever make any progress with this?

[whitebuffalo]

Did you ever make any progress with this?

No, I have not made any progress with it. The money I had set aside was used to build up my Riley Elf so I am saving up to have a try at it next year.

[Radleigh]

Just go fo the Mirage Manifolds as said, proven to work and work well.

[SukiDawg]

I've just had a good laugh looking at this thread....

I'm a professional engine development engineer, I worked at Cosworth for the best part of a decade, and since leaving have done consultancy work all over the industry. Most of the engines I've worked on are turbocharged.


You will have very poor throttle response with the engine and turbo so far apart. The influence of the long pipe on charge cooling will be negligable - so for any real benefit you would defintely need an intercooler. Plumbing the wastegate is also an issue. If you take the pipe for this from the outlet of the compressor scroll, you will suffer from massive spikes in boost across a gearshift (as the throttle closes) - hence the feed needs to come from the plenum downstream of the throttle. That means a massively long pipe and therefore the wastegate control will be poor, which means your boost will be difficult to regulate = bad for the engine.

Aside from the effect on the engine of having the turbo mounted where it is, the problems associated with its position are probably the most significant. You have the oil suppy to wory about. I see there is a small electrical pump on the photos - thats just asking to get smashed off by a speedbump, with pretty terminal results. Also - you would not be able to take that car out in the wet - turbine scrolls will operate at anything up to 900degC when the engine is running hard - try dumping a casting at 900deg into a puddle of water and see what happens. Answer: It'll crack.


All in all a great bit of lateral thinking, but ultimately a poor idea.

[whitebuffalo]

I already thought of sticking with the tried and true front mount set up since the idea of an electric pump dealing with the oil feed to the rear mounted turbo sounds suspect at best and I would always worry about that pressure and the second aspect that worries me is the idea of being a pioneer (guinea pig if you will) for the rear mounted installation. I like the idea of being able to ask people on forums like this how to fix a problem and get an answer since it has been experienced before.

Edited by whitebuffalo, 26 May 2009 - 02:16 AM.

[Wil_h]

When I first saw the rear mount idea I initally thought of all the problems that you say, however, in the states this is a common mod and all the issues have been resolved.

In fact when you start thinking about it in detail , most aren't actually problems. the puddle one potentially is, but the turbo will be running much cooler at the back.

As I think I may have said, ther rear turbo idea is used in the states to get around a law that restricts you modding the exhaust manifold (or something like that). If you don't have this restriction , then sticking the turbo close to the engine is the best idea. The rer mount is doable, but it's a compromised design with no benefit.

I've just had a good laugh looking at this thread....

I'm a professional engine development engineer, I worked at Cosworth for the best part of a decade, and since leaving have done consultancy work all over the industry. Most of the engines I've worked on are turbocharged.


You will have very poor throttle response with the engine and turbo so far apart. The influence of the long pipe on charge cooling will be negligable - so for any real benefit you would defintely need an intercooler. Plumbing the wastegate is also an issue. If you take the pipe for this from the outlet of the compressor scroll, you will suffer from massive spikes in boost across a gearshift (as the throttle closes) - hence the feed needs to come from the plenum downstream of the throttle. That means a massively long pipe and therefore the wastegate control will be poor, which means your boost will be difficult to regulate = bad for the engine.

Aside from the effect on the engine of having the turbo mounted where it is, the problems associated with its position are probably the most significant. You have the oil suppy to wory about. I see there is a small electrical pump on the photos - thats just asking to get smashed off by a speedbump, with pretty terminal results. Also - you would not be able to take that car out in the wet - turbine scrolls will operate at anything up to 900degC when the engine is running hard - try dumping a casting at 900deg into a puddle of water and see what happens. Answer: It'll crack.


All in all a great bit of lateral thinking, but ultimately a poor idea.

[megabob]

i've only seen a Saxo VTS with a rear mounted turbo... lots of alloy piping