waste-gate problem

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rde
MS/Extra Newbie
Posts: 4
Joined: Wed Mar 04, 2015 1:49 pm

waste-gate problem

Post by rde »

I'am using a megasquirt 2 on a Volvo 480 Turbo. I have replaced the MAF sensor with a pipe.
Under 100kpa the boost control from the megasquirt keeps the wastegate shut. Normally this wouldn't be a problem. But the turbo is a very small one and with the MAF removed, the turbo gives that much more air while just cruising that it builds up pressure before the throttle valve. after the throttle valve the pressure is lower. When I accelerate to about 80km/h and just keep the throttle in position to keep 80km/h my MPG is around 33. When I lift up the throttle pedal a bit the speed increases to around 90km/h and MPG increases to around 42. Is there anyway to change the firmware that boost control will be working while MAP reading is 100kpa?
I will use a fully electronic waste-gate actuator(doensn't require boost to open it) that is controlled by a PWM signal.

Roel
MegaHelp
Helpful MS/Extra'er
Posts: 50
Joined: Thu Oct 23, 2008 10:21 am

Re: waste-gate problem

Post by MegaHelp »

That is weird. I have done these engines. They are great power plants in the Renault 5 GT Turbo. Even in stock format.
I have not had any problems tuning them.

Also: the waste gate actuator /boost solonoid does not work that way. When the boost solonoid is not used, the waste gate will open at 0,7 bar, depending on the type of spring used.
The actuator / solonoid will not "open" if this pressure is not met. The assumed 0.7 bar will always be the minimum pressure. The actuator will not open before that.
The solonoid / boost control can only raise the pressure. Not lower it.
If you run a vacuum in your engine, the turbo will still try to make pressure, but most of the times there is not enough exhaust gas to spin the turbo hard enough to cause problems.

I guess your Blow Off Valve (BOV) is stuck or not fitted if you have pressure problems in your system.
Also you will get boost-creep if your timing is way to much retarded.
It will generate very hot gasses and the turbo could spool quicker.

These are not very thirsty engines. They are just really easy to work with.
Just make sure your ignition timing is correct and your fuel metering is correct.
rde
MS/Extra Newbie
Posts: 4
Joined: Wed Mar 04, 2015 1:49 pm

Re: waste-gate problem

Post by rde »

that's not right. The solonoid / boost control can only decrease boost. With stock ECU with the vacuum/boost hose not fitted to the solenoid it gives more than 100kpa of boost. (200+kpa in inlet manifold). With the hose fitted to the solenoid it gives 65kpa of boost. Also with the megaquirt I can lower boost under WOT to as low as 30kpa.
With the stock ECU I have no problems. And with the megaquirt I tested out that with the MAF fitted and with an AFR of 13.5 while cruising I have got no problems. But then the turbo is less responsive at low rpm.
MegaHelp
Helpful MS/Extra'er
Posts: 50
Joined: Thu Oct 23, 2008 10:21 am

Re: waste-gate problem

Post by MegaHelp »

The solonoid is a bleed valve. If not used the actuator wil open at the standard pressure of the actuator. If the solonoid is used some of the pressure will bleed away.
So if you have a pressure of 0.9 bar in the manifold and the solonoid is bleeding 0.2 bar, the actuator is just starting to act.
If it does not work that way, you have to review your pipework.
Still.. Even if the hose is not connected to the waste gate actuator, you would get insane boost at WOT (hence overboost protection), but with little throttle the car would drive fully normal.

So you have things routed like it is not supposed to be.
Someone may correct me if I am wrong.I only am aware of the raising pressure boost control method.
On my own car is a 0.2 bar (2-3psi) actuator. With a boost controller I can get it up to 1.2 bar. Works like a charm. This is a Mazda MX-5 1.6. But It works the same for the 1.7 8V Renault engine that is in your Volvo. I have converted these engines and know them quite well. I love them over the stock 1.4 turbo engine in the GTTurbo 5. That is a little beast. The 1.7 is more sophisticated and gives power in a wider range. There is nothing wrong with these engines. And they can be dialed in very easy.
rde
MS/Extra Newbie
Posts: 4
Joined: Wed Mar 04, 2015 1:49 pm

Re: waste-gate problem

Post by rde »

you're right. It is working like you described. But my problem was that the wastegate was shut under 100kpa. I have now installed an electronic waste-gate actuator. And fooled the megasquirt by recalibrating the map sensor. The map sensor now reads 100kpa to much al all times. I recalibrated my tables. And it is running fine now in closed loop boost control. No idiot throttle response anymore. I have got an average MPG of 41. (17.5km/L). With stock ECU it was 28MPG (12km/L). But It would be nicer and much easier to tune if I could just make the boost control work under 100kpa. So again what do I need to change in the firmware to make it work under 100kpa. I am now running on firmware 3.4.0.

roel
MegaHelp
Helpful MS/Extra'er
Posts: 50
Joined: Thu Oct 23, 2008 10:21 am

Re: waste-gate problem

Post by MegaHelp »

Waste gate only opens up after preset pressure is met as it is pressure fed and spring loaded.
That is how it works.
And it is not causing any problems off-boost. When there is no boost, there is little resistance in the hot side of the turbo.
It won't harm your MPG a lot.

Check the stuff you have made. It cannot be right.
It makes no sense to recalibrate your MAP sensor as it wil disturb your fuel calibration.
17,5km on one litre of fuel is insane for this engine. Even in NA version. Why do you have a turbo anyway if you are driving that slow.

Now I would really like to see that MSQ of yours.
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