Boost issues...

[Jonathan]

Not 100% sure whats amiss with my car atm, seems slow and not very tight on acceleration....funny how the human body can detect so little difference in things so I chucked out a freescan log.

Basically my guess was right, I was saying to carl C today when we went out that his car felt as if the thing was being pulled along by a tight rope where as mine feels as if the rope is going slack here and there.

See graphs attached:

red=throttle %

blue=Boost sensor voltage

yellow=wastegate duty

From when I used to do temperature control it looks like a classic over compensate line...it sees the massive rise in pressure and goes 'oh crap, back off'...instead of having a nice clean steady approach to full boost I get this flutter or my slack rope feel, there's no real bite to the accelerator.

Any clues.

I'm thinking pressure test for leaks in the induction system to start. The 2nd graph has a steady wastegate DC but the boost pressure is dropping...if anything with increasing RPM it should get higher ! As can be seen the boost rarely gets close to 2.0v - in some cases as low as 1.7v - what is the factory 0.84bar voltage ?

Good news is there are zero knocks and the car is in closed loop all the time.

Bad news is the injector pulse width seems to jump from 9-10 and the 2ndry injectors seem to be inconsistantly operating on each run.

Could also be leaking past the BOV ?

Sticky wastegate not coming back immediatly ?

What about pipework ballooning ? I've re-done a lot of the silicon hose, I can't believe they would balloon to a point of significal pressure drop but

[Vulcan Grey]

Not 100% sure whats amiss with my car atm, seems slow and not very tight on acceleration....funny how the human body can detect so little difference in things so I chucked out a freescan log.

Basically my guess was right, I was saying to carl C today when we went out that his car felt as if the thing was being pulled along by a tight rope where as mine feels as if the rope is going slack here and there.

See graphs attached:

red=throttle %

blue=Boost sensor voltage

yellow=wastegate duty

From when I used to do temperature control it looks like a classic over compensate line...it sees the massive rise in pressure and goes 'oh crap, back off'...instead of having a nice clean steady approach to full boost I get this flutter or my slack rope feel, there's no real bite to the accelerator.

Any clues.

I'm thinking pressure test for leaks in the induction system to start.  The 2nd graph has a steady wastegate DC but the boost pressure is dropping...if anything with increasing RPM it should get higher !  As can be seen the boost rarely gets close to 2.0v - in some cases as low as 1.7v - what is the factory 0.84bar voltage ?

Good news is there are zero knocks and the car is in closed loop all the time.

Bad news is the injector pulse width seems to jump from 9-10 and the 2ndry injectors seem to be inconsistantly operating on each run.

Could also be leaking past the BOV ?

Sticky wastegate not coming back immediatly ?

What about pipework ballooning ?  I've re-done a lot of the silicon hose, I can't believe they would balloon to a point of significal pressure drop but

You graphs don't begin to tell the whole story though. It is possible that your ECU is opening the wastegate on purpose... Maybe your IAT is too high (bad cc waterpump impeller) for example.

Maybe you can share your freescan csv file.

[Jonathan]

As far as I can tell the car runs on the money as far as the other values are concerned, the charge cooler never gets much above ambient even at high sustained boost.

The prob is the ECU is not opening the wastegate at all infact it's trying to close it according to the wastegate solenoid duty cycle (yellow trace).

Gonna try some things tonight, mainly bypassing the solenoid and see what values I am getting for mechanical boost - under these conditions the wastegate shouldn't flutter at all, prob is with the Esprit is the rpm/speed picks up so quick you run out of road/get very high speeds before you can get an decent set of results.

EDIT:

Been out to finish some other work, air bleed nut on the chargecooler was weeping a bit so I tried to tighten it and 'CLONK' from the plenum cover...it does this when you rest / lean on it after a run which is a bit odd was at the bottom of my list to worry about...I wonder if there's a crack somewhere, everything is tight, can't see any damage.

Added freescan file, Dermot if you have time, any clues ?

freescan log

Edited June 19, 2006 by Jonathan

[CarlC]

Jon,

Any chance you can post the origonal as the feilds are in the wrong order or are mising from this file.

P.s. I've emailed over the latest version, if you can import and compare an early log with this one once you've sorted out the fields.

[Jonathan]

OK that link should be the original file now (just uploaded it) - lots of idle, sat at 3 traffic lights for a decade.

Edited June 19, 2006 by Jonathan

[CarlC]

Jon,

Very interesting suggestion from Travis. I no bugger all about the IAC but its the one chart were your car is significantly different. your log showing between 80-100, all other logs i have show typically 40-60.

Ill need some help to understand the significance of this.

suggestions anyone ?

Edited June 19, 2006 by CarlC

[Vulcan Grey]

Jon,

Very interesting suggestion from Travis. I no bugger all about the IAC but its the one chart were your car is significantly different. your log showing between 80-100, all other logs i have show typically 40-60.

Ill need some help to understand the significance of this.

suggestions anyone ?

Your IAC is too high, should be between 20-40 at idle, it really does make a big difference at idle.

Yor MAT is very good at a max of 37C, no need to worry about rebuilding the ccpump for a while.

The secondary injectors don't do a whole lot. I would think they would be doing more at 1.9+MAP, 100%TPS, 100%LOAD, and 4800+RPM! Though in that situation your A/F is only around 11 so no need for more fuel... Though I thought that's when the secondaires would be needed under those conditions. Around line 4487 you have all those conditions and no secondary injector duty cycle at all!

I'm not exactly clear myself on what the wastegate duty cycle means exactly, but it seems to be allowing a high boost as long as your foot is in it (TPS high).

[Jonathan]

From what I understand IAC lets air past the throttle body iirc to alter the idle speed almost like a throttle jack, its always been between 40 and 80-90 (once it went into low orbit at 170!).

I'll look into re-setting it however it does idle at 1050rpm and I have done a recent ECU reset.

Yep - puzzled on the 2ndry injectors too...they do come in but only on really high revs.

It's the boost curve that bothers me, you can feel it in the car, the initial pickup is good but quickly becomes slack, gets better at higher engine speed but by then you're running out of rpm and road.

The wastegate DC is like a pulse generated bleed valve, the number represents the % the valve is operational, the valve simply blocks pressure from the turbo getting to the wastegate capsule, the higher that value the more the ECU is trying to overboost the turbo - given enough rpm and road I reakon you'd saturate my wastegate solenoid...atm I'm still looking at sticky open wastegate (wouldn't suprise me, looks like someone dug it up from the titanic) or air leak from the turbo itslef, the induction system or the dump valve - could also have a blockage in the wastegate solenoid preventing the capsule from moving back freely...all sorts of things.

I'll do another scan asap with the wastegate piped directly into the turbo outlet (ie mechanical boost) and see what the graph looks like then.

[Vulcan Grey]

From what I understand IAC lets air past the throttle body iirc to alter the idle speed almost like a throttle jack, its always been between 40 and 80-90 (once it went into low orbit at 170!).

I'll look into re-setting it however it does idle at 1050rpm and I have done a recent ECU reset.

Yep - puzzled on the 2ndry injectors too...they do come in but only on really high revs.

It's the boost curve that bothers me, you can feel it in the car, the initial pickup is good but quickly becomes slack, gets better at higher engine speed but by then you're running out of rpm and road.

The wastegate DC is like a pulse generated bleed valve, the number represents the % the valve is operational, the valve simply blocks pressure from the turbo getting to the wastegate capsule, the higher that value the more the ECU is trying to overboost the turbo - given enough rpm and road I reakon you'd saturate my wastegate solenoid...atm I'm still looking at sticky open wastegate (wouldn't suprise me, looks like someone dug it up from the titanic) or air leak from the turbo itslef, the induction system or the dump valve - could also have a blockage in the wastegate solenoid preventing the capsule from moving back freely...all sorts of things.

I'll do another scan asap with the wastegate piped directly into the turbo outlet (ie mechanical boost) and see what the graph looks like then.

Yeah, the IAC will always try to correct the idle, even with an air leak for example. And that is what your IAC is doing by running 40-80 at idle. That is why you can't adjust the minimum air rate bleed screw by ear... the IAC will fight to keep the 1050 idle while you adjust the screw. But iif you adjust it while watching the IAC counts in freescan, you can get it down to 20-40 and the IAC will be in the correct range. When the IAC is up around 70 it'll make the car difficult to idle, and may stall at first until warm. Then once it warms up it will probably feel like it's running fine.

I wonder if you have a weak wastegate spring (casualty of some of your rust?). As you build boost the spring can't hold the pressure after a certain point and then the ECU detects the slip and starts adding in force to hold the wastegate closed. Since its a control loop, there is some delay that you are feeling and seeing in the graph, as the ECU catches up.

Can you check the wastegate with a vacuum/pressure gauge, see when it pops open? Or whatever the prescribed Lotus check is (haven't read that part of the manual since I haven't hads this problem yet).

I once had a time where my chargecooler pink silicone hose to the intake kept slipping out from the clamps (too slippery). And that could be heard a a big pop, and then I could hear the turbo spool freely, and there was no power at all (like a wimpy honda). And that was a small leak where the hose was still attached by half the hose clamp.

[Jonathan]

Hmm I wonder if the IAC is the source of my low end stutter then, as I was demonstarting to carl at supoercar sunday the car goes 'du-dar' when you squeeze the acceleration (ta about 10%) on pickup from idle, yet when its hot it's as raspy as a race car and sounds great.

I was going to take the car into the local Lotus garage sometime and get a pressure gauge on the wastegate capsule - if it's leaking or as you say has a crappy spring it wont return to close the wastegate.

I think what they do is simply put a pump on it and see if it hold pressure and how far the arm moves...the arm seems sturdy and not floppy at all, but the mechanics are so badly rusted I wouldn't be at all suprised

I can get them to reset the IAC as well and see if there is any cause for it being the way it is.

All good - thanks muchly for the input, will post the results / freescan logs when I know them B)