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I have yet to fit the new fuel pump (still waiting for the new strainer to arrive) so all the ancillaries are as before, I haven't changed anything yet. Those who read my earlier posts may recall I found the turbo wastgate dump port well and truly blocked off, and I 'm wondering if someone else has 'been there before' on the car, and if this issue might be related.

 

Accelerate at full throttle through the gears, then back the throttle off slightly for a steady cruise in 4th or 5th but the boost gauge continues to indicate full boost, even though I'm not trying to accelerate, and the engine starts surging, and hesitating. If I take my foot off the throttle completely, and depress it back to where it was before (again for the steady cruise), and the boost drops away to where it should be for part-throttle, and normality is restored. Performance through the gears is as brisk as expected, however.

It's almost like the ECU is not shutting off the turbo wastegate solenoid with whatever information it's being fed, despite full boost not being required, and I'm also not sure if the engine is still being fed fuel in order to produce that level of boost, albeit on very little engine load.

Any thoughts or pointers would be appreciated, I probably should try another Freescan log too.

 

 

Margate Exotics.

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Update:- I fixed the turbo wastegate pipe using a reducing connector and two different pipe sizes so the problem doesn't happen again. I also fitted a new pair of Moroso coil packs at the same ti

At the same time as I discovered the split pipe, I also found the aftermost air filter housing U-bracket missing. I initially blamed myself for not tightening it up properly, however closer inspection

Right, here's the 217-427 IAC, which has just arrived. I'm not hopeful, because it looks to me like there's a three-angle pintle on it. If you look at the original IAC, it doesn't have that as far as

Are you saying that your symptoms were identical to the ones I'm describing, Nick?

Reason I ask is that the turbo is a recon one from Turbo Technics (yeah, not my favourite people, but there you go), and the wastegate assembly was new. the car's only done a thousand miles since then.

Margate Exotics.

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Hi Ian ,well my issue first started to manifest as an over boost issue which for me was down to a stuck wastegate pivot,but as you say yours has only covered a 1000 miles maybe yours is unconnected to my issue.When you say the car is in 4th 5th etc and the boost gauge climbs does the car actually feel like its gaining boost? or could it be a dodgy boost gauge transducer ,or as mine was in a poor state due to the wiring to the transducer being damaged.To answer your question my symptoms weren't exactly the same but i was just trying to think outside the box as it were, you can easily check the pivot by putting an open ended spanner on the crank it should move back and forward freely (i wish i had done this when my problem started and saved myself a few quid) Interested to hear how you get on. Just for info when mine first started to play up the car went like a rocket!

Simplest things first.

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It does sound like a waste gate issue one way or another,be it mechanical or vacum or a signalling problem,do you always get a positive throttle response or do you some times feel the car is a little 'flat' but the next time you stab the throttle all seems good ?

Simplest things first.

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If your wastegate solenoid (boost control frequency valve) vent is blocked, then you should be restricted to the mechanical boost limit set by the wastegate preload (factory spec is .65bar).  Since it is the ability of the solenoid to vent to atmosphere that allows the ECU to control boost to a point higher than .65bar.

Does sound like you have another issue.

Travis

Vulcan Grey 89SE

My Lotus Photo and Projects Album

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Only if the hose, between the turbo outlet and the wastegate were open to outside air, would you see more than the mechanical boost limit of .65bar.   Unless the wastegate were adjusted for more than .65bar...

If you remove the boost control frequency valve and just connect a hose from the turbo outlet to the wastegate capsule, then the limit is the mechanical limit of .65bar.

If you poke a large hole in that hose, then you'll see max boost, above the overboost limit.

Since Ian said it appeared his vent to atmosphere port in the boost control frequency valve was plugged with something like epoxy, then it is less likely it is vented to atmosphere...  Unless his hoses have a crack elsewhere.

 

I actually blew a hole in my wastegate line on the dyno once!  The engine went into overboost cutout after the boost surged well past the cutoff for the ECU.

 

Travis

Vulcan Grey 89SE

My Lotus Photo and Projects Album

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Shortly after I bought the car, as I was removing the engine and box for various replacement bits, that was when I found the turbo wastegate solenoid dump port had been deliberately blocked, with a steel nail shoved up a short piece of rubber hose non the dump port. It wasn't an accidental thing, and I never understood why it had been done, unless perhaps to mask another problem. The PO could then have jacked up the mechanical boost to 1 bar, and no-one would be the wiser. That may be a cynical viewpoint, but then I'm a cynical bastard.

Anyway, I tested the solenoid some time ago, and it appeared to function correctly on the bench, passing air through one lower port until I applied power to it, which then closed the top port, and connected up the two lower ports.

All the turbo control hoses are new, as is the turbo. I was pondering on the TPS, but ultimately a log is the most sensible course first off. Except it's going to piss down today, so I won't get one until the weather improves.:angry:

Margate Exotics.

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23 hours ago, Vulcan Grey said:

Only if the hose, between the turbo outlet and the wastegate were open to outside air, would you see more than the mechanical boost limit of .65bar.   Unless the wastegate were adjusted for more than .65bar...

If you remove the boost control frequency valve and just connect a hose from the turbo outlet to the wastegate capsule, then the limit is the mechanical limit of .65bar.

If you poke a large hole in that hose, then you'll see max boost, above the overboost limit.

Since Ian said it appeared his vent to atmosphere port in the boost control frequency valve was plugged with something like epoxy, then it is less likely it is vented to atmosphere...  Unless his hoses have a crack elsewhere.

 

I actually blew a hole in my wastegate line on the dyno once!  The engine went into overboost cutout after the boost surged well past the cutoff for the ECU.

 

Isn't there just one pipe to the wastegate capsule, via the solenoid to the induction? So, with the solenoid open the wastegate sees the manifold pressure and with the solenoid closed (or open circuit) the wastegate sees ambient pressure. That way, if the solenoid isn't opening, or is sticking when it attempts to to do so, then the boost would be effectively unrestricted.

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I read that same page a few times yesterday and tried to make sense of it.

Ian has bench tested the frequency valve, but it's hard to say if it will react in an appropriate manner with a pulsed voltage from the ECU. It may not be a good idea to take it out of the equation just yet. The valve may be sticking in the vent position (?).

It sounds like the ECU is figuring out (eventually) that the boost is high (from the MAP sensor or, if the MAP sensor is faulty, from the other sensors) and shutting down the engine. I read in the manual that the knock sensor is a failsafe. If the car fails to control boost, the knock sensor detects a problem (detonation) and tells the ECU, whereupon, the ECU retards ignition and if that fails to stop detonation, the ECU cuts boost via the frequency valve. If the frequency valve fails to control overboost for 3 seconds, the ECU will shut off ignition and fuel.

Might an under-reading MAP sensor also be a possible cause? Sorry, I can't recall in the other message thread what you've already changed.

If the TPS got stuck at high rpms, and then disagreed with the actual throttle position when you backed off the accelerator, would the car slow down (because of less air going into the cylinders), but the ECU continue to provide boost and fuel (according to the TPS).... or is it not possible for the TPS to stick like that? Is the TPS rigidly connected to the throttle?

 

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I wouldn't rule anything out at this stage, the wastegate solenoid may not be working as it should, but short of putting it on someone else's car to test, I'm not sure there's anything else to be done with it.

I did check back at earlier Freescan logs I created, and noticed that the TPS voltage at rest was less than it should read, about 0.39, and that it doesn't reach full voltage as stated in the service notes.

I also has a good poke around on top of the engine, and found the rubber pipe that runs from the inlet manifold T-piece to the crankcase breather valve had become detached, which could lose pressure to the fuel pressure regulating valve. I did feel that whilst the car performs OK, it doesn't quite feel as strong as it should, so could be something to do with that. I won't know until I can get to drive it, though.

Trouble is, the weather was against me, and I haven't had the opportunity to create the log. :(

Margate Exotics.

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2 hours ago, andydclements said:

So, if the solenoid sticks open, the wastegate sees nothing but atmospheric pressure and so keeps the turbo at full output. 

correct.  Not sure if it can fail that way, but worth looking into.

If there was a crack in the hose to the fuel pressure regulator, then that could cause a lean condition with boost, and the ECU should cut fuel and spark, and lower the boost limit back to .65bar.

Travis

Vulcan Grey 89SE

My Lotus Photo and Projects Album

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Despite the good old British weather, and in taking the afternoon off work, I had awful problems getting a decent Freescan log. The damn thing just kept on disconnecting after only a short time, we tried probably 10 times to get a consistent log, and ended up with probably only one good one, and even then I'm not sure it's reading all the parameters correctly. It seems like some readings remain static, even if others change.

Anyway, here it is, but bear with me, eh? To summarise, accelerate hard in, say, 4th. When you reach the desired speed, ease off the throttle to bring it to a steady speed - but the boost gauge stills shows it at 1.1bar, and the car starts missing, and hesitating. Ease off the throttle more quickly, and re-apply the pedal to where you had it before - problem solved, boost falls away, normal service at a steady speed is resumed.

On returning home, I measured the TPS voltage, it goes from 0.39V to 4.14V at 100% throttle. I couldn't see any drop outs through the range, though. I have a new one, ready to fit.

 

I reckon the issue starts at line 511 in the attached log.

 

 

s4strial.csv

Margate Exotics.

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Somehow I just knew you were going to say that, Derek! Still, I've awarded myself 10/10 for effort, and a bottle of Cabernet Sauvignon for good measure.

I'll have another go if it's dry at the weekend, and the wife hasn't got me doing domestic stuff.

Margate Exotics.

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Hello Ian, 

Worn out wastegate or sticky wastegate valve might also be the issue. If the turbo is a reman unit they normally don't replace the bushing and the wastegate valve in the turbine housing. When inner bush or valve shaft is worn the wastgate can get sticky in some conditions. 

VAN DER LEE Turbo Systems     -      www.vdlee.com

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Which ALDL connector are you getting your logs from, the boot or the passenger side? My passenger side one is hideously glitchy - I think the cables are a bit worn, so it can be difficult gathering data so it doesn't "drop out" all the time. 

Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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Jaap - I shall endeavour to elicit a lucid response from the 'Brain of Britain' contenders at Turbo Technics. Wish me luck, I'm going need it.

Vanya - I've been using the cabin connector, and I hear what you say. At rest it's no problem. But after the car has been moving for a minute or so, the laptop says it's lost the connection. I am assuming it would do that with Espritmon, too.

I have had a modicum of success this afternoon: I removed the TPS to see if there was anything amiss, nothing as afar as I could see, so I refitted it. Of course I dropped one of the M3 screws down beside the engine somewhere, gave up looking for it, after half an hour, and used a new one. I set it up to read 0.49V at rest, and it now runs up to 4.22V at 100% throttle. I do have a new one coming, so I will probably change it anyway, assuming the issue is still occurring.

I also fitted a new IAC. The one I removed was not entirely identical in as much as the new one had a point on its cone, the old one didn't, it was flattened off. The cone angles were identical as far as I could see, though. Unable to open the garage door against the wind, I turned the key to make sure it ran, and the engine fired up immediately, which was a good sign. Maybe I will get to run it tomorrow. 

Retired indoors, and back to the Cab Sauvignon now.:wine:

Margate Exotics.

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