What RPM does the turbo kick in?

What RPM does the turbo kick in?

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dr.ian

Original Poster:

115 posts

236 months

Tuesday 18th February 2003
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Yesterday, I showed my car to my uncle, who bought 4 esprits new back in 88. Well, I guess it made him feel young again, because he was really slamming on the pedal. He got the RPMs very high...like 6500 a couple of times. After that, it seems the turbo only starts kicking on at about 4000 and seems weak. Before this, it would turn on as it approached the 3000 RPM mark, and really boosted the acceleration. What should it be at? Could the turbo have been damaged? Anyway to check its function? Maybe I am just getting used to the boost.

superdave

935 posts

237 months

Tuesday 18th February 2003
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Your uncle had his fun back in 88 now it's your turn. I would think again about letting your pride and joy into other hands. Hope it hasn't damaged anything. There could be many factors why the car is behaving differently. I thought that the turbo kicked in at around 3500RPM with the biggest torque at 4000RPM but Iam still new at this and the likes of Calvin Hamada or Jim McFadden will be able to put you straight. Other factors could be the weather, engine temperature, constant hard running? When was it last serviced? When did you notice the drop in performance, was it straight after your uncle drove it or have you tried it since?

cnh1990

3,035 posts

244 months

Tuesday 18th February 2003
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The turbo usually kicks on mine at 3K or just after. It depends on what gear and speed. But it goes to 1 bar and sticks pretty good. The SE has quite a bit of a kick compared to a non intercooled Esprit. Could be a few things. Sometimes the throttle cable slips a bit if someone has been mashing the pedal, then the throttle plates do not open fully. On my friends Mike's car the lining from the flex tube from the air box peeled off inside the tube and the blockage made the turbo performance lackluster. How does the clutch feel? It's not splipping is it? Did the car smell funny after he finished driving it? Also check the plugs and see if they are fouled or burnt. I change mine every 10K miles or so to keep it up to specs. It says you can go longer but performace suffers, so what's fun in that.
Calvin 90 SE

lotusguy

1,798 posts

238 months

Wednesday 19th February 2003
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Dr. I.,

Sounds like Calvin covered all the obvious culprits. Personally, the throttle cable sounds suspect. The car should be well capable of operating in the 6,500 rpm range with no problems.

Some of the weirder causes could be that the timing belt jumped a tooth, have you checked belt tension? You should be able to twist it 45° in either direction, no more, if you can twist it further, your belt needs to be tensioned. To check if it jumped a tooth, put the car at TDC and see that the dimples on the timing pulley rims are still aligned. The best way to do this is put the car in 5th gear and push it forward 'til the dimples align (if you run out of room, put the car in neutral, push it backward, re-engage 5th gear and push forward again 'til you get the dimples aligned). Once the dimples line up, check the timing pointer on the flywheel to insure it's at TDC, if not, you jumped a tooth. Each tooth = 8°. The jump of a single tooth will still allow the car to run, but all the 'oomph' will be gone, somewhat similar to what you describe.

Another possible cause is the turbo itself. To check this, remove the intake hose going from the airbox to the turbo, run your finger inside both the hose and the turbo housing, if your finger comes out with any oily liquid at all, your turbo bearing seal is blown requiring a rebuild. Hope this helps...Happy Motoring! Jim'85TE

GUY JOHNSON

179 posts

245 months

Wednesday 19th February 2003
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I own an "88,and my turbo kicked in at 3,500 rpm and it was pretty consistant all the time.



Guy

superdave

935 posts

237 months

Wednesday 19th February 2003
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Very silly suggestion but is anything blocking your pedal? When I first bought mine, the carpets were fixed with velcro and kept slipping underneath the pedals which restricted them. Not to clever hey...

dr.ian

Original Poster:

115 posts

236 months

Wednesday 19th February 2003
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Ok, My car seems tuned fine, and has recently been serviced. I did change the air filter and spark plugs yesterday. The car seems to run just fine, but the turbo seems absent (The timing belt is fine). It does turn on, but it is not as powerful feeling. Mabey like there is a leak somewhere. When I push on the gas there is a significant amount of slack in the throttle cable. At the engine, there is enough slack to almost pull the cable right off. Could this cause these symptoms? Does the turbo kick on if you achieve a specifed RPM, or does it kick in if you achieve a specified RPM in a specified time? The latter circumstance would make that seem possible. Also, I found a vacuum line that was leaking. It was the one at the front on the the intake manifold that raps around to the drivers side and meets next to another vacuum line. That seemed to help, but I still think something else (throttle cable) is contributing to the problem. My uncles high RPM ordeal may not have pushed the car to it limit, it was only for about 1 second, but the oil light came on. We immediatly stopped the engine and restarted it, and all indicators were normal. He claimed that the throttle linkage was "stuck" (I did not mention that before) and reved the engine up while only going about 10 mph, which may be what is throwing the performance off now.

lotusguy

1,798 posts

238 months

Wednesday 19th February 2003
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dr.ian said: Ok, My car seems tuned fine, and has recently been serviced. I did change the air filter and spark plugs yesterday. The car seems to run just fine, but the turbo seems absent (The timing belt is fine). It does turn on, but it is not as powerful feeling. Mabey like there is a leak somewhere. When I push on the gas there is a significant amount of slack in the throttle cable. At the engine, there is enough slack to almost pull the cable right off. Could this cause these symptoms? Does the turbo kick on if you achieve a specifed RPM, or does it kick in if you achieve a specified RPM in a specified time? The latter circumstance would make that seem possible. Also, I found a vacuum line that was leaking. It was the one at the front on the the intake manifold that raps around to the drivers side and meets next to another vacuum line. That seemed to help, but I still think something else (throttle cable) is contributing to the problem. My uncles high RPM ordeal may not have pushed the car to it limit, it was only for about 1 second, but the oil light came on. We immediatly stopped the engine and restarted it, and all indicators were normal. He claimed that the throttle linkage was "stuck" (I did not mention that before) and reved the engine up while only going about 10 mph, which may be what is throwing the performance off now.


Dr. I.,

You state the "timing belt is fine..." what does that mean? Have you checked to see that the valve timing is correct? The high centrifical force on the belt at high rpm can cause it to stretch and jumping a tooth is very possible. It's an easy check, so make sure you do it.

As far as the throttle cable, there should be no slack in it at all. You need to remove the plenum cover and observe that the throttle plates actually open fully when the pedal is pressed to the floor, merely tightening the cable won't necessarilty facilitate this as the cables do require replacing from time to time because they will stretch beyond their given adjustability. This is a somewhat common problem with Esprits. If you merely tighten the cable without a visual check of what's happening to the throttle plates, you may create a condition where the throttle plates won't fully close on pedal release, creating more and different problems. Happy Motoring! Jim'85TE

dr.ian

Original Poster:

115 posts

236 months

Wednesday 19th February 2003
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I checked the timing. Everything lines up and the belt is at a good tension. All is great there. I know this sounds stupid, but what/where is the plenium? Is it tough to open, and will I need to buy a gasket to put it back together? I will check that today...once I know what it is. The throttle seems very loose.

superdave

935 posts

237 months

Wednesday 19th February 2003
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When you say that the turbo comes in but doesn't feel like much kick, what sort of boost gauge readings are you getting and for how long? Does the boost gauge move at all?
When did you do your engine tune, oil and plug change, was it before or after the problem arised?
Does your car run normal before the turbo kicks in. What sort or oil pressure readings do you get when the car is very hot?
As Jim suggested, you'll need somone in the car as you check the throttle in the engine bay. But to rule this out if the throttle cable is knackered, I suppose you could tighten the slack just for a test run only to see if this changes the symptoms or resolves it.
Jim, what happens if the wastegate valve is loose i.e. open all the time, what would happen? Can any of the breather pipes when blocked cause a problem. I wonder why the oil light came on??
Is yours a Carbed turbo? If so ask Jim if a faulty choke could have anything to do with the problem.
By the way Ian, Iam like you a complete novice but when you get any problems try to list as many sysmptoms as psosible i.e hot/cold, before/after any work carried out on car etc, readings/gauges also help but not entirely accurate.

cnh1990

3,035 posts

244 months

Wednesday 19th February 2003
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I would just about suspect the throttle cable at this point in the symtoms you describe. The plenum is either black or orange and is ahead of the throttle body or carbs. Undoing the bolts you can remove half of this plenum and have a good look at the throttle plates to adjust it. If you have the knack you can adjust it without opening up the plenum. The idle stops on the linkage is where the cable should be with the pedal fully up. If the linkage has lifted off the idle stop you have tightened the cable too much and you will have a high idle. You could try and take up the cable slack in this way before cracking open the plenum.

How hard the turbo kicks in depends on engine vac, speed, and few other parameters. I'm not quite sure on the deatils of how it works on Bosch if you have that FI or carbs. I could tell you a lot about the Delco. I don't recall which one you have at the moment.
Calvin 90 SE

>> Edited by cnh1990 on Wednesday 19th February 15:52

lotusguy

1,798 posts

238 months

Wednesday 19th February 2003
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Calvin,

As this is a 'new' car to Ian, I would discourage having him judge the throttle plates by looking at the idle stops. This is because there is the possibility that the throttle plate shaft is twisted which would allow it to rest on the idle stops while the plates themselves remain open. A visual check is really the thing to do.

Ian, using a 10mm socket, undo the 10 bolts holdong the plenum halves together (as Calvin said, it's the painted Black or Red box that the turbo feeds into). When you remove this, you'll see the 4 round, brass throttle plates. Moving the throttle linkage will open/close these plates. Adjust the cable so that the plates fully open when the gas pedal is fully depressed and make sure they fully close once the pedal is released. Adjust the cable slack to achieve this and if you can't adjust it sufficiently to do this, you must replace the cable as it has stretched too much. Happy Motoring! Jim'85TE

cnh1990

3,035 posts

244 months

Wednesday 19th February 2003
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I suppose if he is not used to the car, looking at the idle plates would be a sure way to go. You would think that if the linkages were messed up and that throttle plates were mis-alinged with the idle set screw the idle itself would be not set right at 1050.

Oh well I guess it's as well he does a visual. I hope he has a gasket handy and doesn't over torque the bolts. It seems he might not have a torque wrench handy, Oh course he may very well have one.

Hard to tell, he may be an old hand in auto repair and may just need a push start in the right direction.
Calvin

Skerd

384 posts

248 months

Thursday 20th February 2003
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Just trying to learn something new myself here. If the turbo does reach max boost, does that mean the throttle linkage has to be OK?

lotusguy

1,798 posts

238 months

Thursday 20th February 2003
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Skerd said: Just trying to learn something new myself here. If the turbo does reach max boost, does that mean the throttle linkage has to be OK?


Skerd,

Not necessarily. Your boost gauge actually reads the boost pressure in the plenum. It's possible that the turbo can spin fast enough to produce full boost, but misadjusted throttle plates (due to several things) don't allow all that boost to pass into the engine and it will feel sluggish or hesitate.

Much more likely however is the fact that since the engine cannot achieve max rpm due to intake restriction, the turbo won't achieve proper boost...Jim'85TE

dr.ian

Original Poster:

115 posts

236 months

Thursday 20th February 2003
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Ok.... I believe my oil light came on because the pump could not keep up with the RPM of the engine, and it was there as a warning. But, it did turn off immediatly. The car idles with oil pressure around 4, but when moving, it is up to 5. The car always runs at about 80C. The boost gauge will get up to .65 bar, but is is just slightly delayed and not quite as quick to boost up. I did take the plenium off, and am repainting all of that stuff orange again. My cable adjuster was at the maximun adjustment, and there was a good inch of slack in the cable still. I am positive that is as bad as it could get. The symptoms, I believe started when the car was reved up. Then again.....I could have disrupted an old vacuum line putting in the alternator last week. I am going to make sure the plenium is sealed tight, because it sounded like one of the hoses going to it was sucking in air around the edge, and did has a small tear in it. And maybe that was compounded by the terribly loose throttle cable. Where can I get a new cable/ or shorten this one and inch?

Skerd

384 posts

248 months

Thursday 20th February 2003
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Jim - thanks for the info.

lotusguy

1,798 posts

238 months

Friday 21st February 2003
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dr.ian said: Ok.... I believe my oil light came on because the pump could not keep up with the RPM of the engine, and it was there as a warning. But, it did turn off immediatly. The car idles with oil pressure around 4, but when moving, it is up to 5. The car always runs at about 80C. The boost gauge will get up to .65 bar, but is is just slightly delayed and not quite as quick to boost up. I did take the plenium off, and am repainting all of that stuff orange again. My cable adjuster was at the maximun adjustment, and there was a good inch of slack in the cable still. I am positive that is as bad as it could get. The symptoms, I believe started when the car was reved up. Then again.....I could have disrupted an old vacuum line putting in the alternator last week. I am going to make sure the plenium is sealed tight, because it sounded like one of the hoses going to it was sucking in air around the edge, and did has a small tear in it. And maybe that was compounded by the terribly loose throttle cable. Where can I get a new cable/ or shorten this one and inch?


Dr. I.,

As I suspected, your throttle cable has stretched. You can get these from any of the usual sources, JAE, SJSportscars, Fox Valley Motor, etc.

The best way to swap them out is to tape some nylon twine to the old one and pull it through to the throttle pedal, then attach the new one and pull it back through, fairly simple. I believe that you can also just get the inner cable and use the existing sheath. Steve or Jeff can tell you when you call them. Happy Motoring! Jim'85TE

cnh1990

3,035 posts

244 months

Friday 21st February 2003
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As a temp fix you can use a cable clamp and tighten up the pedal side. Don't use it long like that as the stretched cable can break and it that happensit may strand you. I snapped a cable in a Europa and I had to tie the throttle open to 3K and limp home to do repairs.
Calvin