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rogerch

Another boost question

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This is the first Esprit I've ever had, and never driven another, so I have nothing to compare it against, and I suspect the nearest one to me would be about 500klm away.

When I first got it last November I thought it was fast, but the turbo was noticable when it came in.

Now having rebuilt the carbys, the induction system, gone over the electrics, and adjusted the turbo, a bit of guess, it's gone wild.

It seems the turbo is there from below 2000 rpm, and it just keeps going, I should be happy and I am, but, are they supposed to come in that early, once I have achived the speed limit, which doesn't take long, and I'm just resting my right foot the gauge does go back almost all the way to the left. And yes the wastgate is working.

Roger


Life is like a sewer, what you get out of it, depends on what you put into it. (Tom Leahrer)

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Turbos are really load/gear dependant not RPM, and also depends how hard you stamp the floot down.

Turbo boost is a product of gasses turning the turbine, so you're looking at a product of volume of gas (throttle in effect) x RPM (engine speed).

If your RPM is low but you have your foot down hard you wont really see much boost, conversly if you have high RPM and low throttle you wont see much either.

In 1st you'll struggle to get maximum boost, 2nd will come in somewhere on the rev range depending on whether you boosted in 1st and so on.

3rd and 4th are the better choice but again it depends on whether the turbo is already spinning from a previous gear or whether it has stalled from closed throttle. If you do compare it I like 3rd becuase it's not so fast (over 100mph in 4th) and you can feather the turbo accuratly to the throttle.

If you start at say 20mph in 3rd and floor the accelerator you should hit max boost at about 3000 or perhaps just below as Mark says but a whole lot of other factors can influence this (intake resistance, exhaust back pressure, exhaust temperature and so on).

What have you done to adjust the turbo I wonder ?

BTW I have seen air intake pipes (on my car) that have totally been ripped open and by passed the air filter - this would make the spool up time shorter.


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Be careful with the actuator arm - the wastegate is in flow with the exhaust - a correct description would be a Wastegate inhibitor arm.

If you take the wastegate capsule off all you'll get is zero boost as the wastegate flaps around in the exhaust breeze.

In the past I have likened it to a kite on a string - there the kite is the wastegate and the string is the arm/actuator.

You would notice a gain in boost if the wategate arm was incorrectly set as the arm would not allow the wastegate to open enough. Plus being a turbo you haven't got a chargecooler and no overboost. As long as the car is boosting to the correct pressure I can't see a problem.


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Let's see if I have this right, the bost is set to 0.9, so anything under that, isn't going to do anything, it won't open until 0.9, which is about what i see on the gauge. So to my way of thinking if my bost pressure sarts to noticably up from around 2000 rpm on, this is not conected to a wastgate setting?

In fact I should be happy because this is giving better low end performance than I had before. and even better, I seem to be using less fuel! I just need to know I'm not going to blow it up, I have a trip to Sydney coming up, and there are some good bits on the old highway and no plod, so I can enjoy myself!

Roger


Life is like a sewer, what you get out of it, depends on what you put into it. (Tom Leahrer)

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Wategates are progressive, well at least the ones I have seen are, they dont just fly open of you would get a large drop in speed - they are feedback regulators if you like.

I just went out in the GT3, it does seem a fair bit early to be at 2000 rpm max boost, I know mines only a 2.0L so it take a little longer.

Best thing to do is to put a compressor on the wastegate capsule and look at the movement in a controlled manner - what you might have is the rod wound in too much which means the waste gate will in effect suddenly open or be opening later than expected which gives the turbo a faster spool - either way you wanna fix it, might go like a rocket now but it's now right imo.


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I'm not seeing full boost at 2000rpm, but it is substancial, more like what I was used to seeing come in at 3000 plus, I'm pleased because it makes me think I did a half reasonable job, but I would also say I am getting less lag than I used to and it's certainly coming back up faster after gear changes. Though I would like a recycling BOV.

Roger


Life is like a sewer, what you get out of it, depends on what you put into it. (Tom Leahrer)

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... I have a trip to Sydney coming up, and there are some good bits on the old highway and no plod, so I can enjoy myself!

Roger

When are you coming down? (I'll be at Port Macquarie for the last two weeks of May though.)

This could be a god opportunity for a number of us to get together.

The old highway is heavily patrolled now. Bikers tend to have one fatality per month on it plus other serious "offs".


DanR

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I won't be coming down until the 29th or 30th, and only for a couple of days, I was thinking of the Bulahdelah stretch is that the one you mean or the Gosford stretch, I know that one is policed, I have it on good authority some idiot a few years back shot a video from an S4 elan at high speed on that bit, and Mr Plod was Pi**ed off, cause they couldn't catch it, but I don't know who it was.

Roger :lol:


Life is like a sewer, what you get out of it, depends on what you put into it. (Tom Leahrer)

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here the article on setting the wastegate - > http://www.lotusespritworld.com/EGuides/ET.../Wastegate.html

BTW - I believe you cannot achieve fullboost while rolling in first gear - as a means of primative traction control. You can get 15secs of overboost by launching from a dead stop with the RPMs over 5000.


Lou Senko

Austin, TX

more, more, more....

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If you adjust the waste gate actuator arm it does affect bring boost in early or late. As Jon says the cars isnt an SE so there is no overboost its just mechanical based of the actuator capsule. I cant remember which way round to make the adjustment, IIRC if you shorten the arm it will give you more boost earlier. If your capsule is working correctly it should be a problem for your car other than your turbo is working harder, has less time to cool and will generate higher intake tempratures an lower overall performance.

Personally, I'g get the car back to stand performance then adjust to suit your personal likeing. strong boost at 2000rpm does sound excessive.

As was suggested I'd also strongly suggest checking that your capsule is working correctly and not bleeding boost pressure from a split pipe for example. This could also have similar results to what you are experiencing but lead to dangers in overboosting your turbo.

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Thanks for the link to the LEWs article, now I have to admit to being really dumb! When I had the carburators off to rebuild, I didn't like the look of the small hose to the wastegate actuator, so I replaced it. When I got this vast improvement in performance, I was concerned that the previous owner had adjusted the actuator with a possible leak in the old hose, and now I was getting too much bost.

Forgive me, it's my first turbo, link anything to the induction, it's vacum, unless it's a turbo!! der. I thought it sucked to open the wastegate, of course it blows! Go on have a laugh!

On the upside I obviously haven't forgoten how to set up multiple carbys, and must be close with the elecs, I'll measure the exact movement to presure tomorrow.

Thanks Dum Rog :lol:


Life is like a sewer, what you get out of it, depends on what you put into it. (Tom Leahrer)

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