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If there's a serious space issue I can understand it, but otherwise I can't see the point. Happy to be proven wrong though. I guess the only real advantage is reduced under bonnet temperatures? Obviously turbos get really hot and so do engines, it kinda makes sense to keep them apart. Heat soak and all If it dos'nt increase lag IMO it seems like a good idea, however the more pipes you have the more boost drop your going to get which is curse word!
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Sierra - here we go again! He has an illness, it's not his fault.
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qwerty
Club Retro Rides Member
Posts: 2,410
Club RR Member Number: 52
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If it dos'nt increase lag IMO it seems like a good idea, however the more pipes you have the more boost drop your going to get which is curse word! Get a shorter car ;D Mount it where the middle box should be? Right another thought has just come to me...... The exhaust gases when they reach the turbo are going to be a lot cooler than in a conventional setup. The main problem with using an easy to get turbo off a turbo diesel is the heat that it would have to deal with if the turbo was mounted up front? So in theory you should be able to use a TD turbo no problem in this rear mount setup?? Which makes it even cheaper. Seriously loving this idea more and more haha ;D
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Last Edit: May 29, 2008 8:33:49 GMT by qwerty
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Mount it where the middle box should be? I've seen some Ford Probes on an American site with turbo conversion on the V6 lump, iirc nearly all of them had the turbo sat literally between the drive and passenger. Probably cause there's no bloody room in the engine bay of a V6 Probe!
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Sierra - here we go again! He has an illness, it's not his fault.
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May 29, 2008 11:29:55 GMT
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manifold to back box on a 205 isn't 'that' long though is it compared to most yank motors...
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May 29, 2008 13:09:06 GMT
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The main problem i can see with them is that you are relying on the exhaust flow only to spool the turbo. As far as i know, heat play a big role in turbo's. Most turbo manifolds have small runners that converge into the turbo, so when the hot gas gets to the turbo it expands through it. This expansion really helps them spool better. Though some of these setups seem to be around, so would be interesting to see the lag of one compared to the same turbo on a proper turbo manifold.
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May 29, 2008 13:23:04 GMT
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I still don't see the point. Everyone accepts that a draw-thru turbo set-up is very laggy because of the long intake tract. Yet peolple say there is no noticeable lag when you're running the intake tract virtually the entire length of the car. Doesn't make sense.
And I still don't see what problem it solves. Heat soak can be solved by better engine bay ventilation. If there's no room for the turbo in the engine bay, there's always stuff you can move (battery for instance), and if there really isn't any room under the bonnet, surely somewhere under the floor which is closer to the engine is better than way out back. Plus, I'd sooner have heat soak in the engine bay to deal with than a red-hot turbocharger next to my fuel tank.
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qwerty
Club Retro Rides Member
Posts: 2,410
Club RR Member Number: 52
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May 29, 2008 13:33:46 GMT
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I'd sooner have heat soak in the engine bay to deal with than a red-hot turbocharger next to my fuel tank. .......But it won't be red hot......becuase the heat source (the exhaust gasses) have cooled somewhat by the time they reach the turbo.....well thats how I understand it anyway.
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MWF
Posted a lot
Posts: 2,945
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May 29, 2008 15:19:11 GMT
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As far as I know lag isn't an issue because they tend to run a smaller turbo than you would normally. I'd rather try one really rather than just right the idea off and talk pedantic forum theory.
As for the benefits it's all about installation time I believe, it's fair easier to get a car up on the ramp and hang one of these kits off the back than to start pulling the engine bay to bits.
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May 29, 2008 15:30:13 GMT
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I can't see it's much quicker to install one of these than a regular turbo system. Both need to be car-specific kits. What's the difference between installing a new downpipe / manifold with a regular turbo, and installing a new rear section with one of those turbos? You still need to plumb in oil feed / return lines, you still need to plumb intake piping in...
Plus, how does the oil return to the sump? I assume it has some kind of pump as you can't rely on gravity returning the oil any more.
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May 29, 2008 15:41:00 GMT
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They either run a pressurised feed from front to rear, or have an additional electric pump (as mentioned), or an altogether separate oiling system with a reservoir, pump etc For example, on one of the STS kits:
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MWF
Posted a lot
Posts: 2,945
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May 29, 2008 15:44:25 GMT
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I'm surprised you can't see how much easier it is tbh.
Oil feed has already been discussed.
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May 29, 2008 15:46:38 GMT
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May 29, 2008 16:15:36 GMT
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[.......But it won't be red hot......becuase the heat source (the exhaust gasses) have cooled somewhat by the time they reach the turbo.....well thats how I understand it anyway. So defeating the process entirely..... Good turbo system design/spec is to keep as much heat (Energy) in the pipe as possible In order of preference pre turbo 1: Twin skin Hydroformed manifold with reasonably equal length (Short) primaries 2: Twin skin Log manifold 3: Cast Iron equal 4: Cast iron Log 5: Tubular equal length 6: Tubular unequal 7: entire system, front box, mid box etc The heat loss alone will be horrendous, oh and those silencers..... what do you think they are designed to do..... Take energy out Add it all up and why Bother ? I just see losses all through the system yes you can wrap or ceramic coat, but if you go to that expense, why wouldnt you do it to the underbonnet components of a conventional turbo set up and remove the heat issue in the first place Its just wrong....... Basic thermodynamics / Turbocharger theory Understand how they are supposed to work/ how to spec them and you would never give this a second look....
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May 29, 2008 16:22:22 GMT
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i don't really understand all the negativity,tbh.
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qwerty
Club Retro Rides Member
Posts: 2,410
Club RR Member Number: 52
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May 29, 2008 16:25:59 GMT
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Nope me neither.....It obviously works even if its not as efficient as a conventional installation.
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May 29, 2008 16:45:57 GMT
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There's negativity because it's not a good set-up. I'll admit that I'm not turbocharging expert, I'm still learning and having fun messing with them. But Dom knows his stuff, and as he's very thoroughly explained why they are complete waste of time and money. Here's another example of a similar thing: Woo! Look at all those science-y words they're using! But we all know that electric "superchargers" are a load of curse word. What I'm trying to say is, the sites which sell these systems are very good at using convincing words to make them sound as if they know what they are talking about and look as if they're product is good.
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May 29, 2008 16:51:45 GMT
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i wouldn't compare those electric 'superchargers' to those turbo installs.
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May 29, 2008 17:01:19 GMT
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The way I see it is this; Using a stock exhaust from the manifold to the turbo means it will act as a type of accumulator for exhaust pressure, keeping the turbo spinning between gear changes; then, the length of delivery pipe cools the charge before it enters the engine without having to go round the houses to get there (I bet some intercooler installs have damn near the same length of pipe involved as a straight run from back to front); I always was led to believe that the cooler and more dense the charge the better? It all depends on what you are using the car for I suppose.
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Rover Metro - The TARDIS - brake problems.....Stored Rover 75 - Barge MGZTT Cdti 160+ - Winter Hack and Audi botherer... MGF - The Golden Shot...Stored Project Minion........ Can you see the theme?
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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May 29, 2008 17:13:19 GMT
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At least its shows who not to ask advice about installing turbos!
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May 29, 2008 18:10:44 GMT
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right, seems to me we need a breakdown here of what does what and how to get the most from the argument a turbo works by pressure differential. IE. the energy that flows across the turbine makes it spin, the more pressure at the header compared to less pressure at the tailpipe applies more effort to the turbine wheel. this is why a turbo is semi altitude compensating, thin air at the tailpipe gets more boost which makes the thin intake air dense picking up the ponies you lost to being 10000ft above sea level. the expanding exhaust gas in the manifold helps to give better available pressure to the turbo. because of this the turbo needs the most energy before it not after. the exhaust system, which is what-5/6ft long on a pug? will have considerable cooling effect on that lovely expanding gas. even more so at speed meaning a drop in energy available to the turbo. all that lovely expanding gas has shrunk to a mere fart at the tailpipe. which is why loud exhausts are often short exhausts as even a 6ft open pipe will do a lot of dampening to the sound energy compared to 12" zoomie so pressure equals more available power to the turbo. short header runs eqaul more power available to drive the turbo, as its closer to the pressure source with less parts to rob the energy. big v8s can get away with longer exhuasts by the shear volume of gas they pass with their big pistons and lengthy strokes. now thats that bit, now lets try some intake theory. you run that pipe which is what? 2" diameter for 5-6ft back down the car. thats a big volume of space! even a huge intercooler like a gtp car would probably not be that big in volume. yes that length of pipe will cool the charge, but that small turbo you fitted will not have the flow capabilities to fill that pipe fast enough. if we said that pipe was the size of a pale of water, and a race air-air IC setup was about 1/2 that volume; with the same tap which one fills faster? thats what gives you lag you stomp on the loud pedal and demand that turbo rush all its available boost into the engine, but it takes time for it to fill the pipe, hence you go nowhere for a second or two. now heat- you want less heat then trade off for a bigger turbo. thats what porsche did with the 911. being air cooled engine bay temps are far more crucial.; by fitting a larger exhaust housing it flows more gas (less back pressure) so gets the hot exhaust gas out the way rather than soaking into the lube side of things and coking the bearings. the trade off is a longer spool time, meaning the power has moved up the rev range and comes in more suddenly- many perceive this as lag. the whole reason manufacturers have pioneered this idea (IMO) is ease of fitment and cost of development. not designing a decent turbo manifold and producing it has just saved them a packet! the pipe comes in here, lopp it off, stick a flange on it, cost 3p to design. a proper manifold that's correctly designed to give the best flow but shortest route, most compact, strong for turbo support will cost one hell of a lot more. and install costs are cheaper making the package more profitable for the dealer and more convinient and attractive for the buyer. the only time a turbo should be in the middle or at the end of a turbo exhaust system is on a two stroke as the expansion chamber has be first to control the flow of gas through the engine. I don't profess to be a profesional at all this so please, feel free to re-invent the wheel. just don't make it a square one, eh?
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