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Bibs

Turbo options

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If the turbos are all used on the same car you would be able to negate a lot of the differences you mention. Also, I doubt if one turbo will come out as the 'best', I would imagine that as you say they will all have their strong/weak points; one may offer stacks of boost, one may have very little lag but at least we'd know what does what and be able to make an informed decision from there.


88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

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Upgrade today to remove Google ads and support TLF.

If the dyno run were to be completed... I would like to see the dyno graphs for 2nd and 4th gear. 2nd gear is a good demonstration of the spool speed of the turbo and 4th gear will show the peak power and torque better.


Modifying esprit's.. now that's fun..

PS... I AM NOT A CERTIFIED MECHANIC.. I Have chosen to help those in need, in the past and must not be construed as being a certified technician.

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Guest Troy Halliday

I could possibly do this with Rogers car (if his willing of course) I could arrange it with Steve Greenal who I know has very accurate rollers and is not into ego boosting numbers but how the car runs and performs. He also has a Lotus background so will be familier with the cars.

But the biggest issue I see here is that idealy it needs to be done to a stock car or at least a level of tune that all suppliers recomend their product for.

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I'm not sure that comparing different turbos on the same car is really a valid test....

The compressor maps for different turbos will suit a different state of tune for a given motor...

Basically you'd tune the motor (fuel delivery, intake temp, boost pressure, etc) to suit the map of the turbo.

Putting a turbo that is tuned for 78% efficiency at a mass air flow rate of 48lb/min with a pressure ratio of 2.6 for a car making 440hp and using 26lb of boost, on a car that is using 14.7psi of boost, and an inefficient intercooler, won't yield very good results.

Now if you are looking at two turbos with identical maps, marketed to work with a stock engine, on a stock car... then that might be valid, if only to compare bearing schemes...

I would rather a vendor post the maps and the information to make use of the information, and possibly recommended upgrades to get certain results... And then each person would take responsibility for their intended result, realizing that the vendors can't be responsible for testing every different combination of upgrade and running condition of every Esprit... IMO


Travis

Vulcan Grey 89SE

My Lotus Photo and Projects Album

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Sorry Mike, that should have been 4Cyl Esprit "GT1", because that was what the owner was claiming... :)

The engine was from a Sport 300, and had a"LeMans" plaque on it (I did read it). I can't remember exactly what it said, but I do recall "GT1", and he claimed it was from one of the "GT1" racecars.

Nope - the 1993 and 1994 Lotus S300 Le Mans entries were in the GT and GT2 categories respectively; They never ran a 4-cylinder car in GT1.

:)


1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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I'm with Travis. Post the maps and the upgrades required to make the best use of the particular blower. :animier:


Driving Automotive Aristocracy Since 2004

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How many out there are REALLY able to read AND understand AND properly apply what you see on a compressor map??

Show of hands please!

My hand is firmly down by my side.

Power and torque plots showing the before and after turbo upgrade, YES, turbo responses to exhaust gas flow etc NO.

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I have been asked by a fellow forum member to give my take on this thread, and since I hold him in particularly high regard, and although much of it has been said by others, I will do my best not to disappoint him. So, in my hallmark condescending tone of voice, I plunge myself into the flame wars.

First, I'd like to comment on a couple of minor issues early in the thread. I too do not think that it is advisable to restrict the oil flow on a journal bearing turbo.

DanR raised the very valid question of internal vs. external wastegates. An external wastegate is preferable, because internal wastegates tend to make a mess of the flow around the turbine wheel, which may significantly reduce its efficiency (some turbines are worse than others). When we are using the wastegate, we are trying to make a lot of power, so that would be an opportune moment for good efficiency. The argument that the wastegate is there to reduce turbine power anyway is not valid, because with greater turbine efficiency we would be able to open the wastegate more, to get lower exhaust manifold pressure, which is good for engine pump work and cylinder emptying alike (meaning less crankshaft power is expended during the exhaust stroke and more fresh air is sucked in during the intake stroke). Furthermore, an external wastegate lends itself to interesting things. Depending on your preferences and requirements for emissions and sound, you can choose to reintroduce the wastegate flow into the main exhaust flow in a number of ways. Put it in upstream of the cat and you are always emissions and sound compliant. Put it in upstream of the muffler and you are always sound compliant, but the pressure drop over the cat is much reduced. Or just dump the darn gas! You can run fairly high power with a stock cat (and be clean for the vast majority of the time), the pressure drop over the muffler is also reduced, and you get a clear audio feedback on the boost. On my S4, if I ever decide to change the turbo, I want to get a V8 thing-under-the-bumper, and make a wastegate tailpipe to the left. In the unlikely event that I decide it is too loud, a small muffler can be added. Incidentally, this is how aging P911T's work.

The main issue here, however, was turbocharger selection. This is part science, part black magic, and part luck; with skill and experience, informed choices may be made, but the only way to be certain is to experiment, preferably using well designed and executed procedures, so as to ascertain the relevant data and to eliminate the sources of error as much as practically possible. I, too, feel that it will most likely be impossible to declare a clear winner even in a well controlled experiment, as the choice will be highly dependent on personal preference. When speccing a turbo, we always need to make a compromise. We should balance at least the following:

* Reliability (refers unpredictable failure)

* Durability (refers predictable failure or life expectancy, not to be confused with the above)

* Physical size restrictions

* Response at various engine speeds (I prefer that term over lag or spool-up)

* Power or torque at various engine speeds

* Fuel consumption

* Product cost

* Plus whatever I happened to forget

Each person will have different priorities, and different goals leading to a different setup of any number of things around the car, so one person simply declaring one turbo the winner on one car would certainly be interesting to hear about, if nothing more. Some people might favour the cost and reliability of journal bearings, while others favour the response and efficiency of ball bearings; and so on. For the time being, all that seems to be available to us are a few compressor maps on the suppliers websites. We may attempt to compare them (we notice that WC has swapped the axis labels around), and it seems to me that, perhaps, the WC compressor sizes are slightly larger than PUKs at the same stage numbers. But not only are the maps quite different in graphical style, even if they were not, they wouldn't be truly comparable unless they were produced on the same flow bench by the same technician (for example, I would argue that the surge limit is a matter of opinion). There are no turbine maps to compare, but then, turbine maps never did say much to anyone anywhere anyway. There is no telling the response. The data at hand is grossly incomplete. We must experiment, and I too would hope for the suppliers support, since I feel that they are currently asking us to buy expensive hardware of which nothing much is known. Appallingly, the higher spec products don't even come with compressor maps.

Ideally, I feel that the proposed experimental comparison should also include something out of the GT28R range as seen on http://www.turbobygarrett.com/turbobygarre...ts/catalog.html. This would be a bit more involved to do, however, as it is not a direct bolt on fit, but on the other hand, part of the range lends itself well to the external wastegates that I like so much. Probably overkill for this thread, but it would have been interesting all the same.

Personally, I am biased towards preferring good turbocharger response and broad maps. I would tend to be sceptical of clipped turbine wheels and compressors with no maps; and, while flow capacity is nice, I would want a reasonable surge margin. I don't subscribe to the viewpoint that the highest power number at a single rpm number on a dyno run wins, rather, I want the fastest real world car, and that does require good response and a torque curve somewhat wider than the space between gears. For that reason, I think that lap times on suitably fast track should be a prominent feature of the experiment. I think the testing should be done during a period of particularly stable weather to get fairly similar running conditions for each turbo. Meteorological data should be recorded; and tyre pressures and fuel load and all that stuff should be kept the same. When on the dyno, you should, as a bare minimum, record power and boost as a function of engine speed in a tall gear (4th seems like a sensible choice), and also try to record the boost as a function of time when idling at an intermediate engine speed (say 4000 rpm) and slamming on full throttle, to get some sort of comparable turbo response times. If you get all ambitious, you also measure the air mass flow as a function of engine speed (if you can), as this will tell us where we are in the compressor map, which in turn allows us to read theoretical compressor efficiency and surge margin, which tells us a lot about how well matched the turbo is to the engine. If you can find a dyno that can do this, then it is well worth travelling a bit to get there. Also, please try to record the compressor discharge temperature as a function of engine speed at full load (the silicone hose should seal well enough even with two thin wires between the charge cooler and the hose). The higher the temp, the poorer the compressor efficiency. If you get even more ambitious, you also measure pressure and temp before and after the turbine, so we can determine the turbine efficiency (and ultimately the turbo efficiency), but that requires drilling into the exhaust manifold near the turbine, which may not be to everyone's taste, although it affords a perfectly useful pyrometer instrument in the car afterwards (just don't use el cheapo temp probes that break and mess up the turbine wheel). In a professional setting, well over a hundred engine parameters would be recorded, but we also need to stay practical here.

With some experimental data, we might better be able to make informed choices. Now, do I think that would help Bibs in his quest? Well, there is no telling, really. I mean no disrespect to the honourable Bibs whatsoever (or to anyone else for that matter), and I admire his initiative and dedication to our common cause that shows up yet again here, but having read this thread, it seems to me that he may be suffering from PLE syndrome (planless engineering). This is an all too common ailment amongst amateur car modders. "I'll pick up a few goodies and bolt them on, that should make me faster", seems to be the way the majority of these people think. While that theory may well hold true, it is not the recipe for achieving anything resembling an optimum, in which all parts come together in well-matched harmony where no single part is particularly overpriced and overspecced (or underspecced for that matter). What he needs to do is to come up with some concrete realistic goals and a budget to match. This can then be broken down into a coherent plan, and that plan can then be executed. This doesn't have to be something fancy enough to be presented to a board of directors, just scribble something down, but do include the whole car in the process, and make your choices with the greatest of care. Like, for the engine, you might say, I need so-and-so much power, with fair response and torque and whatever characteristics you prioritise. To achieve that we somehow determine that we need, say, a bigger charge cooler, a chip, some injectors, some cams, and a turbo to match. Tally up the cost and compare to the budget. This may be an iterative process, and for something as complex as an engine, professional advice by someone experienced in our particular engine and without further financial stake in the project may be well worth it if you are serious about what you are doing (i.e. don't just ask the guy selling you the parts)(btw I'm experienced enough in the art of engines to realise that I'm not qualified for this). Then, and only then, go out and buy all the stuff you need and bolt it on.

Don't do what the proverbial Bibs is doing. Suppose he chooses his favourite turbo and puts it on his car. Then, a few months down the line, he decides he wants a bigger charge cooler. And so on and so forth. And before he knows it, that expensive turbo of his, that was determined at great pains to be the best available, has become a complete mismatch. Don't embark on your 400 bhp project by first perfectly matching the turbo to 300 bhp. I know this goes against the popular view that tuning comes on in a number of stages, but that is the way I see it. This methodology is called project management, and it is there to get you the most bang for your hard earned bucks (or quid or whatever you use) through minimizing the number of hasty choices and regrettable purchases. While it cannot guarantee that you get the very best available turbo for your finished package, it can certainly increase the likelihood.

Good luck and best regards all around!

  • Like 1

Jens

15407iq.jpgProud member of The Fearless Red Squadron

Better living through turbocharging!

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Well put!! And I agree wholeheartedly... however.. the idea does tend toward the slightly complicated side. It should be done though.. and it should be done by dyno tuning too!! A big part of the problem is not being tuned properly in the first place. Each engine/turbo combination is going to need it's own tune.... for that matter... every engine should be individually tuned. This is why i have no intentions of using the original factory ecu on my build.... it will be tuned for the setup that is there... not just an original factory map that is still designed to perform safely with a factory turbo and factory intercooler. There is soo much more to getting it right than just turbo selection... I suspect we will end up with a proper stage by stage piece of advise. For example --

stage 1: PUK turbo with stock intercooler and re-mapped chip designed for PUK turbo. Total cost: $5000

stage 2: WC turbo with over-sized intercooler, twin fluid pumps, custom mapped chip for this setup: total cost: $7000

stage 3: WC stage 2 turbo with exhaust header, over sized intercooler, new plenum box, oversized secondary injectors, custom intake piping, freeflow exhaust, external wastegate with an external dump, 272 intake cam and green dot pulley... etc... total cost $10,000

that's what I think would be of great assistance to the members of the forum...

and then, once the research is done, the best way to do it from the forums perspective is to have the forum sell the kit for retail and have the suppliers give a slightly discounted price to LEF so that Bibs can actually make a little bit of money back for his efforts.


Modifying esprit's.. now that's fun..

PS... I AM NOT A CERTIFIED MECHANIC.. I Have chosen to help those in need, in the past and must not be construed as being a certified technician.

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Hey Mark & All,

Warning :thumbup: Apparently turbos are a HOT topic! :blink:

Good to see ya! All this just got too complex for me! :P Anyway wouldn't it make sense to ask Bibs what his intentions were w/ his car? Maybe he is looking @ staying w/ one state of tune for a reasonably long period of time :P . What a concept!

If that's the case then he could try recommended turbos that would suit his engine mods. That is, unless the suppliers

don't offer a turbo for the level that he expects.

Do you Bibs, desire a long term level of power? Or desire to reach for the Holy Grail of squeezing out the last bit through constant modding? Inquiring minds want to know! :P

Edited by Esprit Aviation

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Hi Jens,

This was a great write up ! :blink:

Your method to explain things is way better than mine ... and your English also is lightyears better. :thumbup:

Cheers

Marcus


Marcus

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If I was Bibs i'd pick up the phone and ask Brian Angus for advice. He probably remembers all the turbo options Lotus tried and their + points and - points.

Regards,

Peter.

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Already spoken to Brian, my first port of call - Lotus were limited in the number of aftermarket options they looked at, as they didn't need to.

Jens - Thanks for the post, I've read it 5 times now! I've no plan in place as I didn't expect my current turbo to fail. I'm in a position now where I need a new one. If there are better options than the stock turbo (and if price is indicative of quality, then there is) then I'd like to ask others what their opinions are of these units and as we have the suppliers on here, I'd like them to tell me (sell to me) so I know what their turbos offer.

If I had no interest in increased response or more boost, I'd had just replaced the current one. If your 18 year old TV blew up, wouldn't you look for a new one with more features, surely both turbo as other technology has moved on?


88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

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WC Stage 2 and VERY fast SE reporting for action!!!

Bring it on!

Oh and i'd be wanting a very special one of them show plaque things for this 'trial'...


2009 World Singstar Champion

No I don't like the Europa, Evora or Exos.

"Like a cockmonkey with 3 cocks."

SLEG_Rog.jpg

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Thanks, Marcus, you're too kind!

Bibs, maybe I was a bit too harsh on your planning skills, but my advice still stands. I wanted to stress the importance of matching the turbo to the engine you want to end up with rather than the one you start out from. Talking to someone in the know is always a good thing, but even I can tell you that the oem solution was to a large extent governed by product cost, a statement informally backed by Garrett people.

One thing that I think perhaps we should elaborate on is surge margin, as I have noticed that there are quite a few hybrid turbos available out there for our cars. The basic idea of a hybrid turbo is to combine the high flow capacity of a large compressor with the response of a not-so-large turbine. That sounds wonderful, but there are at least two distinct drawbacks.

1: Assuming that you have a fairly large air mass flow (a fair assumption considering that this deals with large compressors), that large flow must also pass the turbine section. Since the turbine is relatively small, a large portion of the flow will be going through the wastegate, it just won't all fit in the turbine. In order for the small turbine (operating on limited mass flow) to generate enough power for the compressor (which will be consuming plenty of power to compress all that air), we must have a very large exhaust manifold pressure. In other words, the turbine/wastegate combination can be seen as a turbine with extremely poor efficiency, even if the turbine itself can be demonstrated to have good efficiency (something we can only benefit from lower down in the engines speed range where the air consumption is smaller). It may seem counterintuitive at first that a large wastegate flow leads to a large exhaust manifold pressure. Ultimately, your engine will make more top end power with a larger turbine.

2: With a relatively small turbine, we will still get good response (say, similar to oem spec), i.e. we get to combine good boost and a small air flow. Now, a centrifugal compressor can only have so much map width, and as we go up in size to get increased flow capacity, we also loose its capability for boost at small flows. Of course, we can have small flows going through a large compressor, but not while making boost. The larger the boost pressure, the larger the flow must also be. Too much boost and too little flow at the same time leads to a highly undesirable condition known as surge, where the boost pressure fluctuates uncontrollably as the compressor blades alternate between stalling and regaining composure. This can be detected as a series of loud bangs or whooshes in rapid succession or it can be detected by the vibration of the boost gauge (a good business case for an *undampened* boost gauge (which can be annoyingly noisy even under normal operation due to pulsation from the intake valves opening and closing)), and prolonged operation in this regime can damage the turbo. Also, I'm not sure the ecu can keep up and maintain lambda. Change down a gear if it ever happens! - and remedy the situation at your earliest convenience.

If you look at a compressor map, you will find a sharp border, known as the surge limit, above and to the left of which he who enters should abandon all hope. The problem of surge can be combated to an extent by electronically limiting the boost at lower to intermediate rpms, for instance by means of a custom ecu calibration. Given the compressor map and the engines capacity for swallowing air or given a hand drawn boost curve below which you can't detect surge, and given enough money, I imagine it would be fairly easy for someone like Marcus to make such a thing. However, boost pressure cannot be electronically limited to a value below the turbochargers basic boost level, which is largely governed by the choice of wastegate actuator, and is usually around half a bar. Choosing a softer actuator will make it difficult to accurately control the higher boost pressures and is not really advisable in this context. If electronics don't solve the surge problem, you need to better balance your turbine size and compressor size (i.e. select a larger turbine). The closer you can go to the surge limit, the better response you can give the turbo and the wider the speed range you can give the engine. Cutting it close requires tight control over the engine, and you will want at least a small surge margin.

This does not mean to say that hybrid turbos are inherently a bad thing, they're not, they have their place. It just means to say that when buying such a product, you need to know what you are doing (or at least the supplier needs to know it intimately). I hope this illustrates the importance of compressor maps and knowing where we are in them. Furthermore, I think it can be seen as a business case for someone like Marcus to provide kits with a turbocharger and a choice of custom chips to match, and a higher spec kit that also includes, say, a green dot cam pulley and a large charge cooler and whatever else he decides on. But to make the most of it he would have to depend on the discipline of the owners to stick closely to his spec. Can we be trusted to do that?

BR


Jens

15407iq.jpgProud member of The Fearless Red Squadron

Better living through turbocharging!

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Again... Brilliant! It's a shame there's not the market here in medicine hat. There are two VERY good dyno tuner's near by that would be able to re-map the stock GM chip to match each turbo/modification requirement. But... I'm in no position to fund this operation, nor am I Bibs.


Modifying esprit's.. now that's fun..

PS... I AM NOT A CERTIFIED MECHANIC.. I Have chosen to help those in need, in the past and must not be construed as being a certified technician.

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Thanks Jens, after getting really frustrated with the quality of information in this thread, in two quality posts you've started to shed some real light on the subject.

Any chance of talking us through how to interpret a compressor map in terms of expected performance? I'm sure I'm not the only one here who'd appreciate another freebie lesson :lol:


More speed, less haste

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i have to agree jens post make for very good reading, one thing on the list next year is to have my turbo stripped down and all the seals and bearings replaced and upgraded.

the turbos in my old fairlady were modified by kakimoto racing japan and they were much better than the stocks.

besides if i could lose another 3 stone i would have the fastest esprit on the forum :lol:

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Ye...thats the way to go.

Its way to much that do more to confuse in this tread than I have read in a long time.

For the people that not intend or are unable to understand the fully how a turbo works.

Go for a turbo that have been used before on a Lotus and are available from companys like in this tread.

And there is other companys that sells turbos that will work perfect,witch is on this forum........but not in this tread...


89 Lotus Esprit Turbo S

Very fast road and trackday car.

GT3076R+ a lot of other modifications.

http://lotusespritwo...inZzdningz.html

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Already spoken to Brian, my first port of call - Lotus were limited in the number of aftermarket options they looked at, as they didn't need to.

Jens - Thanks for the post, I've read it 5 times now! I've no plan in place as I didn't expect my current turbo to fail. I'm in a position now where I need a new one. If there are better options than the stock turbo (and if price is indicative of quality, then there is) then I'd like to ask others what their opinions are of these units and as we have the suppliers on here, I'd like them to tell me (sell to me) so I know what their turbos offer.

If I had no interest in increased response or more boost, I'd had just replaced the current one. If your 18 year old TV blew up, wouldn't you look for a new one with more features, surely both turbo as other technology has moved on?

Hi bibs.

Have you find the turbo you want?

As I understand you will like to have a newer more modern turbo on your car for impoved response and more boost?If you only put on a free flowing exhaust you will gain incredible response and able to use more boost even with the stock turbo.And a stock SE turbo has capasity for max 300bhp.

The GT28RS is rated to 350bhp with incredible good spoolup.

After what i read and have learned about this turbo is that you will get earlier boost and more bhp available,than on the old SE turbo.

It depends how you gona use your car.If you go on the track and run max for 10-20minutes then I wouldnt use more than 280bhp out of the GT28RS.The backpressure will be very high and can overload engine and/or the turbo.

But in a car to outrun some in the trafficlights you will be able to use may be 320-340bhp.

For short dyno runs with racefuel they are able to get 373bhp.

So 350bhp is a raiting for dragrace as I understand it.

If I wanted the best drivability on the road (not the German Autobahn with free speed limit or other severe use.) with 320-330bhp I would have gone for the GT28RS with free flow exhaust.I gess you would gett 1,0 bar of boost already at 2000rpm with this set up and you dont need to do any other work on the engine than having a healty stock engine with chip.

This is the turbo I would have used with T3 exhaust turbine to bolt direct on the manifoil.

http://www.atpturbo.com/Merchant2/merchant...tegory_Code=GRT

You have to use the 5 bolt Ford flens with waste gate and adapt the exhaust.

Edited by rydning

89 Lotus Esprit Turbo S

Very fast road and trackday car.

GT3076R+ a lot of other modifications.

http://lotusespritwo...inZzdningz.html

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