What happens if the wastegate is open all the time?

[Davezj]

as the title says.

force the Wastegate open fully, does the turbo make any boost at all?

What do you say will happen.

 

[Peter_D]

Good question. I believe that the waste gate acts as a relief valve, therefore if it stays open the boost pressure will be vented directly into the exhaust on our turbos. On larger setups with separate waste gates it would go directly to the atmosphere with a rather large roar.

 

[Guest]

depends what you mean by open, (valve physically open to bypass exhaust pressure?) then i guess it would make little to no boost depending how big the wastegate is to its corresponding turbo ie small wastegate to a big turbo would probably create a fair amount of boost at full scream.

 

[bradc]

I doubt it would make much boost until higher up in the range when the wastegate couldn't handle the entire exhaust flow. By 7000rpm I'd expect it to be making quite a bit of boost

 

[Guest]

Yo would find that you have crappy power and the fuel to air ratio would be running uber rich and may even kill oxygen sensors and catalytic converters so it may end up being costly if you are going for more boost later in the rev range go to a good dyno expert they would be able to help and it would be better for the engine

 

[Guest]

why are you asking this?

 

[Davezj]

My theory is that if you are not creating boost you are sucking in less air to the engine. The MAF will realise this and put less fuel into the engine for a given postion on the throttle position sensor. thus acting like a none turbo car. giving better fuel economy.

This will be able to be switched in and out as and when you want it.

I have some pics of our turbos showing wastegate size, placement, and generaral orientation, but they are at work so i can post the up on monday if you like.

 

[Adrian]

I don't think it works like that

 

[jungle]

Nice try but no.

 

[Davezj]

Nice try but no.

please explain

if you know what this would do please share you knowledge.

 

[Guest]

When the ECU senses that you are not getting the boost it will try to compensate but its skills of how to compensate are limited and it will try to adjust the fuel, timing and anything else it can control. Most turbo cars ----well in theory--- will then be giving too much fuel to the engine then it will splutter and most likley die out basicly you would experience something similar to what Dan did in this thread.............http://ozvr4.com/forums/showthread.php?t=3238&highlight=splutter . But I may be wrong as all this is based on TAFE trade school lessons and a little experience with a few astra turbo's so if someone has real life experience with VR4's feel free to correct me.

 

[Guest]

there is this pedal inside the car, usually its located around the right foot area.
what you do is press it as lightly as possible to achieve the particular speed you are after, and your fuel consumption will miraculously improve!

 

[Davezj]

there is this pedal inside the car, usually its located around the right foot area.
what you do is press it as lightly as possible to achieve the particular speed you are after, and your fuel consumption will miraculously improve!

!!!

 

[Guest]

My theory is that if you are not creating boost you are sucking in less air to the engine. The MAF will realise this and put less fuel into the engine for a given postion on the throttle position sensor. thus acting like a none turbo car. giving better fuel economy.

This will be able to be switched in and out as and when you want it.

I have some pics of our turbos showing wastegate size, placement, and generaral orientation, but they are at work so i can post the up on monday if you like.

Either.. Buy a N/A V6 or don't create any boost..

 

[Zild]

Yeah get a boost gauge, stay off boost for better economy.
Knowledge is power!

 

[Guest]

When the ECU senses that you are not getting the boost it will try to compensate but its skills of how to compensate are limited.....

I think this is about right. I think the ECU would be able to see the lower airflow at a given RPM and loadpoint and trim the fuel accordingly. However, like when you get too much airflow and you get fuel cut (because the standard ECU's map can't go any further), I bet the same principle applies at the low airflow end of the map. I bet Mitsubishi Mapped it expecting a minimum amount of airflow (wastegate pressure) @ a particular rpm/throttle/load. Any less than this (like if you did keep the wastegate jammed open) then I would imagine it has to inject the 'minimum' amount of fuel it is mapped to do - which could still be too much.

It would however be interesting to see what would happen especially if you could keep the ECU in closed-loop operation; the O2 signal might help the ECU trim back - But then, from the other end of the scale, when my 02 signal went and the ECU was reading a constant super-lean state it could only trim up to 120% (100 being normal operation), so I bet on the flip side it can only 'pull back' the fuel map to 80% of normal.

If that makes sense?!

 

[bradc]

Kieran is more than likely right, and explained it the best

You could swap the boost solenoid to one that is designed for a lower boost car, say only 4psi or something, or even one that would let boost ramp up slower. Easier still as Andy said, get a boost gauge and stay off boost!

 

[Davezj]

Thanks to kieran for coming up with a resonable answer, that is entirly possible. Cheers Mate.

It is just a shame more people can't be helpful when a reasonable question is ask, instead of........ well you know who you are and i hope you are feeling my Padington Bear Hard stare.

i know we are guests on this site but i expected a more intelligent answer to a question.

for those of you who are interested I do have a boost gauge and do use it if i want a economical drive, if i want i can get 32+MPG out of my VR4 which gives a 420Miles per tank and for those antipodean who are interested it is 676ish Km per tank.

anyway i might give it a go and use EvoScan to monitor the results.

just to see what happens!!!

 

[bradc]

420 miles out of a tank is even better than me!

 

[Davezj]

that is topped up to dry.

32mpg and a 60L tank gives you 420 mile per tank. 60-70mph all the way. not an easy thing to do especially in little old England. we do not have that many long flat roads with out traffic jams on them.
But i was hopping to get that a bit better.

Not sure how, hence the reason for the original question.