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Engine Specific Info and Questions => IDI Engine => Topic started by: regcheeseman on October 17, 2011, 05:48:13 am
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Finally, I've got my VNT controller running properly and took the car for a decent 100 mile test run, it's just had the gearbox replaced as well.
I've also got a boost gauge fitted for the first time, it's a 30 LED bargraph and calibrated to 30 psi.
Driving out on the A roads, taking it steady and the boost seems to be fairly tame, around 12psi peak and I'm beginning to wonder if the turbo is capable of actually delivering much boost. However 6 miles into the journey the single lane switches to dual lane and there’s a queue of traffic up ahead. I give it some pedal and the boost is up into the 20's, but I back off as someone pulls out ahead of me, they realise the mistake and pull back in and I'm back on the loud pedal - boost is now off the gauge and charging hard - Suddenly BANG!, huge cloud of black smoke and the gauge drops to 0.
I pull over and refit the boost hose. ::) (something I would be doing a fair bit during the day)
It was on the journey home I notice the problem, the boost is building very quickly, and during a spirited charge in second gear the gauge is straight past the red limit and the motor stumbles/misfires, chucks out a cloud of white smoke and then after a second or two, clears and runs fine.
Any idea what is happening?
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mine did that once,revving the engine in neutral.my vanes are opening at 1 bar so the same thing happen but at only 1 bar.
missed a bit,white smoke but then it returned to normal.
so i will be looking this thread with attention lol
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Isn't this the recipe for destroying your turbo?!?
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What's a recipe for destroying my turbo?
If I knew what was happening then I'd do something about it.
Maybe fit a wastegate?
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Is the VNT controller reacting too slow to the changes?
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What turbo do you have again? Boost spikes of 35 are very bad for the small vnts. 25 psi spikes should be the absolute max for a vnt15 or similar.
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What vnt controllers you have?
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With my late experience if it's a vnt 15 I don't think it can sustain 35 psi without having issues like what you've described only mine was catastrophic failure of the turbo. My opinion after cleaning all the oil and replacing my head gasket is that the turbo is pushing oil into your intake, maybe for only a second or two, your engine is burning it (white smoke) and is then fine for a while. My turbo pushed about 1 1/2 litres into the intake and engine as it was failing. My $.02
I'd like to try that vnt 22 I've seen with modified bearings and seals - 25 to 35 psi would be easy for it.
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yes my engine smoked alot of white when it was running away, this makes a bit of sense. it also could simply be getting into the exhaust.
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What turbo do you have again? Boost spikes of 35 are very bad for the small vnts. 25 psi spikes should be the absolute max for a vnt15 or similar.
No I have a proper turbo not a toy one ;) It's a BV39A-0072 IIRC and it's pushing 30 psi easily
Is the VNT controller reacting too slow to the changes?
possibly or the map isn't right at the moment - it gains revs and boost at an incredible rate - mash the pedal in second and it'll bury the guage almost instantly.
Now that I've learnt to go a bit steady on the pedal - but I was curious what was happening?
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BV39 from a PD100 or PD105 pushing 30psi... Has overspeeding and ultra low efficiency written all over it... :o
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Just cuz it pushes 30 psi easily doesn't mean it should. BV39 is what is on the BRM. It's actually a pretty stout turbo. But tuners generally map for 18 psi sustained with it. Any more and you should go to a larger turbo.
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are you monitoring emps?
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emps? ???
Just cuz it pushes 30 psi easily doesn't mean it should. BV39 is what is on the BRM. It's actually a pretty stout turbo. But tuners generally map for 18 psi sustained with it.
How do I stop it making 30 psi then?
Has overspeeding and ultra low efficiency written all over it...
No signs of ultra low efficiency - my god it shifts ;D
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try this controller
http://dmn.kuulalaakeri.org/vnt-lda/
does VNT & LDA control (boost enrichment)
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like was mentioned.. 35psi is out of its efficiency..
the BV39 is about identical to the VNT17 i believe..
im lucky that my VNT still boosts, its seen over 40 psi before :o
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Sounds like your vanes are stuck closed.
I could easily hit 35 when my vanes were tied closed all the time.
I think a BV39 is closer to a VNT 16, ha, somewhere between the VNT 15 and the VNT 17.
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Sounds like your vanes are stuck closed.
I could easily hit 35 when my vanes were tied closed all the time.
I think a BV39 is closer to a VNT 16, ha, somewhere between the VNT 15 and the VNT 17.
when my vanes were seized closed, i would hit 35 psi before the neighbors driveway, and its not even 100 yards.. and that 35 psi would come on by about 2500 revs..
and any way you look at it, no small VNT is happy at 35psi.. i dont think i would run anything under atleast a VNT 20 with 30+ psi..
i know about VNTs and overboosting.. im surprised mine is not grenaded.. idk how many times ive heard it scream like a oversped G60..
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The vanes cycle open and shut when you turn the ignition on - it's part of the system diagnostics. It will light a red led if there are any problems - and I get green led every time.
However you said that they should be open to limit boost? Is that correct as they would be operating in reverse by my setup.
Mine are set closed at idle and open when you bury the throttle pedal then close progressively as the boost rises, is this the wrong way round?
It would seem so as it shows 15psi at 2000 rpm
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Yes that is the wrong way around. In order to avoid overboosting, the vanes must open at higher rpm.
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Yes it should open as boost rises.
I use the term open because the wastegated turbos use that term when the waste gate opens and relieves some of the boost pressure.
This just shows how sturdy these turbos are,
running that high of boost and a hose pops off,.. yet it survives.
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Ok, I was getting confused, I've looked again and the vanes release pressure from the turbine rather than force pressure into the turbine.
I must have had it straight in my head at some point because I've just gone over the code that drives the VNT controller and it is as follows
0 pedal 0 boost - vanes open
Any pedal input tends to close the vanes proportionally
Any boost increase will tend to open the vanes
I need to go and hook the laptop up to it - run debug and check that the sensors are orientated correctly in relation to the mechanical position of the actuators.
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emps? ???
Exhaust Manifold Pressure. The first thing to monitor with home made vnt controls IMHO. It shows what is happening with vanes.
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The first thing to monitor with home made vnt controls IMHO. It shows what is happening with vanes.
Go on... is this how the TDIs control their vanes? Does it work by measuring two different pressures? I tried to google the term and just got electro magnetic pulse information!
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its not how the vanes are controlled on a tdi. but by measuring the pressure in the exhaust manifold you can get an idea of how efficiently your turbo is working, a 1:1 ratio is ideal, but u can still make more power with more pressure in the exhaust than in the intake. at some point u have too much more pressure in the exhaust than in the intake, and you are losing more power than u are gaining, and also putting extra strain on the turbo and engine. when a turbo is being over spun outside of its efficiency range on the compressor map, the emps get higher and higher in comparison to the boost pressure because it is taking more and more energy to maintain the boost and flow as the compressor becomes less and less efficient. and on top of that when the compressor is working inefficiently it is also pumping air which its much hotter and less dense.
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Just install pressure gauge to exhaust manifold. You clearly see when vanes are moving from emp. EMP usually spikes when spooling, goes down when vanes open and usually goes above boost when rpm rises. Depending of size of turbo.
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The vanes cycle open and shut when you turn the ignition on - it's part of the system diagnostics. It will light a red led if there are any problems - and I get green led every time.
However you said that they should be open to limit boost? Is that correct as they would be operating in reverse by my setup.
Mine are set closed at idle and open when you bury the throttle pedal then close progressively as the boost rises, is this the wrong way round?
It would seem so as it shows 15psi at 2000 rpm
you want them open at idle, then close when you floor it, then open progressively till you get to your desired boost pressure..
i can make about 15 psi @ 2k rpms with no vane control at all..
when the vanes are closed, your EMPs sky rocket.. when the vanes close, the exhaust side becomes small, and a bit restrictive, but spools great.. then the vanes open, and the exhaust side becomes BIGGER, and flows quite a bit better, especially in the upper RPM range..
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Something weird going on with the servo so I unplugged it and pegged the vanes open.
Diagnostics gave me a red light because of the servo - which is reassuring.
And the best I could manage on the run home was 18psi :)
I'll hook up the laptop to the VNT controller and run it in debug mode to find out what is going on.....
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i think ideally u would want the vanes to be closed from idle, then open until peak boost, then open more according to rpm. honestly tho if i were doing it i'd just control it with a boost can and call it good enough ha
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i think ideally u would want the vanes to be closed from idle, then open until peak boost, then open more according to rpm. honestly tho if i were doing it i'd just control it with a boost can and call it good enough ha
If they're closed at idle you'll start building boost at idle, which you probably don't want. In terms of efficiency, you want the vanes open as wide as possible all the time, closing them only to give you the amount of boost you're looking for - otherwise you're just poking a potato in your tailpipe the rest of the time.
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i think ideally u would want the vanes to be closed from idle, then open until peak boost, then open more according to rpm. honestly tho if i were doing it i'd just control it with a boost can and call it good enough ha
If they're closed at idle you'll start building boost at idle, which you probably don't want. In terms of efficiency, you want the vanes open as wide as possible all the time, closing them only to give you the amount of boost you're looking for - otherwise you're just poking a potato in your tailpipe the rest of the time.
yea, you want them open as possible for ANY situation.. the more open they are, the more efficient the turbo is..
the VNT is a HUGE restriction when the vanes close..
you want the vanes closed down at idle, and until boost comes on. once some boost comes on, you want them to start opening up. then you want them to open to a certain point to limit boost at that point.. eventualy, the vanes ALMOST act like a wastegate.. the vanes are what controls the boost level..
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I've a tuning factor built in to the code, I can preload vane opening by up to 100%
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I've a tuning factor built in to the code, I can preload vane opening by up to 100%
Does this adjust the pitch of the vanes using vacuum like the VNT did stock, or are you using pressure?. I'm sure it's using vacuum, but I thought I'd ask. This ardunio based controller looks totally awesome and I think I'll have to build one now.
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hes using a servo or stepper motor, i am guessing the preload will help if the controller is reacting too slowly?
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The preload is an addition a variable in the code
The required servo position (sp) is given the value 0 - 255 (0 is open)
When Sp is calculated from boost value and throttle position I multiple boost value by a tuning factor (originally set to unity =1)
If I change this factor to 1.5, it means at low boost the vanes response remains pretty much as it was originally but as the boost climbs the vanes will have greater tendancy to return to full open position.
It wont change the speed of operation as such
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I think that you'll find that your orginal problem is excessive EMP's which cause the exhaust valves to float.The hydraulic lifter then takes up the slack and you lose compression for a moment.Once the exhaust pressure drops off the lifters back off.I've had this happen before on 3 different engine's.In 2 cases the engine actually quit running and would not start until the lifters had backed off.Tight valve guides and/or excessive EGT's can also contribute to the same problem.
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I think that you'll find that your orginal problem is excessive EMP's which cause the exhaust valves to float.The hydraulic lifter then takes up the slack and you lose compression for a moment.Once the exhaust pressure drops off the lifters back off.I've had this happen before on 3 different engine's.In 2 cases the engine actually quit running and would not start until the lifters had backed off.
Where is the 'I'm not worthy' emoticon?
Thank you very much for your answer, that would explain the fault symptoms exactly.
Cheers!
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thats about as interesting as it gets haha. neato
(http://media.tumblr.com/tumblr_lhwxxlw6b41qb9qjh.gif)
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I think that you'll find that your orginal problem is excessive EMP's which cause the exhaust valves to float.The hydraulic lifter then takes up the slack and you lose compression for a moment.Once the exhaust pressure drops off the lifters back off.I've had this happen before on 3 different engine's.In 2 cases the engine actually quit running and would not start until the lifters had backed off.Tight valve guides and/or excessive EGT's can also contribute to the same problem.
Hey Andy2, I like your thinking on this. I would like to add that high boost levels without enough spring rate for the intake valves will cause the intake valves to float, and of course with the ever popular loss of compression, and the ever possible piston to valve kiss.
Reg, since this is experimental, you might want to plumb in an inexpensive BOV from greddy or someone else, it is cheaper than a waste gate, but it may be good insurance. It is interesting that the Dodge Sprinter uses a stepper motor with a small electronics package built in. Also how about some Pics of the Regmobile cruising through Chedder Gorge ??????
Oh and it could have been worse
http://www.youtube.com/watch?v=AJTjwRni8ow&feature=related
The Blau Maultier