Overboost?? Delta Dash findings
10 July 2002, 11:17 PM
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Did a couple of runs with Delta Dash software attached to the car and below was the findings of change ups in 3rd to 4th to 5th to provoke what I think is an overboost issue.
I think it happened..... Any comments???????????
J
I think it happened..... Any comments???????????
J
10 July 2002, 11:27 PM
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Agree. Increase the restrictor orifice by 0.1mm or use a needle valve or remap the ECU to suit your car.
To avoid overboost beyond my 20 PSI target when it is cold and wet I put up with 18 PSI in the lower gears in warm conditions. Nature of the beast I am afraid.
To avoid overboost beyond my 20 PSI target when it is cold and wet I put up with 18 PSI in the lower gears in warm conditions. Nature of the beast I am afraid.
11 July 2002, 02:57 AM
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Urm, exactly what am I looking for?
I did note that the car was running 15deg BTDC on the timing at mid-rev's high boost. That seems like quite a bit of retard, yet the Knock Correction was showing very little.
Is this a UK Turbo?
I did note that the car was running 15deg BTDC on the timing at mid-rev's high boost. That seems like quite a bit of retard, yet the Knock Correction was showing very little.
Is this a UK Turbo?
11 July 2002, 10:28 AM
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RT - Yep its a UK Turbo with Tek2 , fully decatted exhaust and an STI intercooler fitted afterwards. I didn't feel the retard was that bad but will dig a bit deeper.
As Evil says, the figures show how in change up from 3rd to 4th the boost cuts as I lift off but then comes in too high as I get back on the throttle and has to again be cut. It should be holding 16.5PSI all the way.
J
As Evil says, the figures show how in change up from 3rd to 4th the boost cuts as I lift off but then comes in too high as I get back on the throttle and has to again be cut. It should be holding 16.5PSI all the way.
J
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11 July 2002, 11:02 AM
#8
Relating to my dawes/ecu combined control.
If you put a dawes, actually, let me stop there. A dawes is a pressure relief valve PLV from now on.
Put a PLV set at 16psi in the plumbing somewhere, so the overboost would trigger a direct opening of the wastegate.
No more overboost.
Paul
If you put a dawes, actually, let me stop there. A dawes is a pressure relief valve PLV from now on.
Put a PLV set at 16psi in the plumbing somewhere, so the overboost would trigger a direct opening of the wastegate.
No more overboost.
Paul
11 July 2002, 01:12 PM
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Scoobysnack do us a favour and post a graph of your boost as you go through the gears - then you will see the rise in boost the drop and then it settling - ie it fluctuates.
11 July 2002, 01:12 PM
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How many bars is 18 psi?
Looking at those measurements, and assuming all "overboost" problems look like that, I'd say you guys are overreacting.
I can't see the control system overreacting, or cutting fuel...all seems fine, it is just a controlled high-boost situation.
There's no oscillation, or anything else indicating that the control system is not coping. If something was really wrong, I'd expect all of the input variables (fueling, timing, boost-control) to move to their extremes, or oscilate.
All looks normal to me.
Looking at those measurements, and assuming all "overboost" problems look like that, I'd say you guys are overreacting.
I can't see the control system overreacting, or cutting fuel...all seems fine, it is just a controlled high-boost situation.
There's no oscillation, or anything else indicating that the control system is not coping. If something was really wrong, I'd expect all of the input variables (fueling, timing, boost-control) to move to their extremes, or oscilate.
All looks normal to me.
11 July 2002, 01:16 PM
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The Tek 2 has a target of 16.0 PSI. When it sees +0.3, 0.8, 1.7 or 3.0 PSI over (possibly over a certain time threshold) it does an adjustment to the duty cycle. So really in the highest boosting conditions (top gear on a cold wintery wet day) then you don't want to see more than 17 PSI on a Tek 2. Otherwise it will undershoot before stabilising and is not nice to drive. The overshoot/undershoot/stabilise is unnecessary if you set the car right.
11 July 2002, 01:20 PM
#14
I was under the impression that the wastegate actuator is damped, so that pulses of pressure are averaged out to hold the wastegate at a stable position. So it should not be a problem to vent a little more air to the actuator in the event of overboost, and have the actuator respond in a stable mannner.
The inherent problems with the ECU boost control is the system response changes with so many vairables. It becomes difficult to create a boost control using a single method, to give good control in all gears, or at all loads. Especially as the tools available to physically change it respond relatively slowly, slow enough make a 2ms cycle time pretty pointless.
Paul
The inherent problems with the ECU boost control is the system response changes with so many vairables. It becomes difficult to create a boost control using a single method, to give good control in all gears, or at all loads. Especially as the tools available to physically change it respond relatively slowly, slow enough make a 2ms cycle time pretty pointless.
Paul
11 July 2002, 01:26 PM
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Bruce, yes you are absolutely correct... I wasn't watching TPS 
So overboost.. hmm, just a very little bit (17.9 psi) but as John says this could get a bit higher in winter.
Restrictor drilling time.
So overboost.. hmm, just a very little bit (17.9 psi) but as John says this could get a bit higher in winter.
Restrictor drilling time.
11 July 2002, 01:34 PM
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Well not as I showed it for the first gear of the three because the wastegate duty cycle did not drop, but look how it drops to 74.9 % in the last gear and the horrible undershoot - this wastes performance.
11 July 2002, 01:45 PM
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We need a boost control solenoid that can bleed more air...Then the overshoot wouldn't happen in the first place...enlarging the restrictor orifice in effect does this, but it is uncontrolled.
11 July 2002, 01:47 PM
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I am now coming round to the idea of setting the boost target a good 1-2 PSI higher than I like to run. This would mean that in cold weather when it boosts higher (and is safer to do so) it would not overcompensate. At present I run 20 PSI boost target, but end up running 18-19 in lower gears in hot weather 
It then pours down and the boost goes up by 1 PSI!
It then pours down and the boost goes up by 1 PSI!
11 July 2002, 02:04 PM
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John,
When you say raise boost target I understand the reason and logic behind that, but is it a simple change to the ECU map that can achieve it along with the duty cycle.
And based on the Tek 2 (16.psi) on my car what do you think the extra 1 Psi target would achieve in power/torque terms
J
When you say raise boost target I understand the reason and logic behind that, but is it a simple change to the ECU map that can achieve it along with the duty cycle.
And based on the Tek 2 (16.psi) on my car what do you think the extra 1 Psi target would achieve in power/torque terms
J
11 July 2002, 02:38 PM
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J - boost target on mine has been set to 17, but now need to get it on the rollers - its *MUCH* quicker than the last dyno run from the EcuTek open day and even more now I have a 57i Induction fitted. I was shocked with just how quickly I can build up speed now and even Emma was a bit terrified, which she's never been before in the car 
She's used to it now though
With my target set at 17, the map was compensated for on duty cycle to and was getting no knock at all on the final run, I don't suffer any overshoot probs either, peak is about 0.75 kg/cm above the held reading.
BTW - It would indicate from the Manifold pressure you have got on the figures that your boost gauge is over reading by 1psi or so from what you were telling me. I think my Defi is fairly accurate going by checking it while delta dash was running.......
She's used to it now though With my target set at 17, the map was compensated for on duty cycle to and was getting no knock at all on the final run, I don't suffer any overshoot probs either, peak is about 0.75 kg/cm above the held reading.
BTW - It would indicate from the Manifold pressure you have got on the figures that your boost gauge is over reading by 1psi or so from what you were telling me. I think my Defi is fairly accurate going by checking it while delta dash was running.......
11 July 2002, 04:28 PM
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Seems pretty good
Held of 17.4PSI is tops but if it hits 1.3Bar (18.85Psi) surely thats going to be minor overboost based on when the ECU sees +0.3, 0.8, 1.7 or 3.0 PSI over target it does an adjustment to the duty cycle. Thus overboost ?
Is it happening
J
Held of 17.4PSI is tops but if it hits 1.3Bar (18.85Psi) surely thats going to be minor overboost based on when the ECU sees +0.3, 0.8, 1.7 or 3.0 PSI over target it does an adjustment to the duty cycle. Thus overboost ?
Is it happening
J