[Go Further]

Even with my custom tune, if I control my foot, I average around 31 mpg. I have achieved 33 mpg highway also. Driving style has a bunch to do with fuel economy.

As they say... The best fuel economy mod, is the driver.

 

[ZStang]

As they say... The best fuel economy mod, is the driver.

Of course, occasionally, the loose nut behind the wheel gets 26 mpg combined when playing!

 

[dgc333]

If the wastegate was completely deactivated in slot 5, would that not mean no boost would be produced by the turbo... Thus saving fuel?

I think the wording is misleading in the Cobb write up. The wastegate is controlled by the ECU using a solenoid to route manifold pressure to the wategate actuator to open the waste gate and limit boost. If it was deactivated that would mean that no manifold pressure would be present at the actuator resulting in an over boost condition.

I would suspect that the solenoid is held open so only the actuator spring is controlling boost. This would mean your max boost would be around 7 psi.


Dave

 

[zhent]

Of course, occasionally, the loose nut behind the wheel gets 26 mpg combined when playing!

Your loose nut is still better than mine. I can get as low as 18 combined when I decide to have fun with the car (which is almost all the time).

 

[Go Further]

Of course, occasionally, the loose nut behind the wheel gets 26 mpg combined when playing!

I was always told, the best way to get good fuel economy, is to imagine there is a ripe peach right underneath the go pedal.
And if you press too hard you will squash it.

 

[ZStang]

Your loose nut is still better than mine. I can get as low as 18 combined when I decide to have fun with the car (which is almost all the time).

But you are racing! I tend to do spirited runs on open roads and not on and of the throttle like you do!

 

[zhent]

But you are racing! I tend to do spirited runs on open roads and not on and of the throttle like you do!

Eh, not so much. Yeah, the Auto-X and track days do impact the overall average since new, but I also daily drive this to work. I've seen as low as 18 just doing that. The day I spent on track at CotA got me a combined average of 9mpg driving it to the track, all day on the track, then back home again before filling up...

 

[gatornek]

I will have to defer to those good folks to reply back on that subject as it's not entirely clear to me either.

I'm sure you noticed this, because you did this install yourself, but I found this video of the turbosmart wastegate actuator install. At the 20:15 mark he cranks on the wastegate with the actuator removed and you can see how 'flimsy' it is to open/close with no tension applied.

So in my mind, the two forces in the spring are:

1) The resistance of spring extension - so that the exhaust doesn't suck open the wastegate
2) The resistance of spring compression - so that the rod doesn't prematurely actuate the wastegate open

 

[dgc333]

The strength of a spring or it's rate is expressed in lbs/inch. If you take a 10 lb/in spring and put 10lbs on it it will compress 1 inch, put 5 lbs it will compress 1/2 inch, 1 lb it will compress .1 inch. However, if you preload the spring 1 inch it will not start to compress until 10 lbs are applied then it will start to move at it's 10lb/in rate.

In the case of a wastegate you do not want it opening at all until the ECU commands it to by allowing boost pressure to act on the diaphragm. That is accomplished by preloading the spring. To little preload and pressure in the turbo housing will start to open the wastegate preventing the desired boost from being obtained. To much preload and you get over boost spikes or erratic operation do to the wastegate not operating as the ECU expects.

Dave

 

[EcoVert17]

The strength of a spring or it's rate is expressed in lbs/inch. If you take a 10 lb/in spring and put 10lbs on it it will compress 1 inch, put 5 lbs it will compress 1/2 inch, 1 lb it will compress .1 inch. However, if you preload the spring 1 inch it will not start to compress until 10 lbs are applied then it will start to move at it's 10lb/in rate.

In the case of a wastegate you do not want it opening at all until the ECU commands it to by allowing boost pressure to act on the diaphragm. That is accomplished by preloading the spring. To little preload and pressure in the turbo housing will start to open the wastegate preventing the desired boost from being obtained. To much preload and you get over boost spikes or erratic operation do to the wastegate not operating as the ECU expects.

Dave

Spoken like a true expert. As always, I for one appreciate your expertise and insight.

 

[dgc333]

Spoken like a true expert. As always, I for one appreciate your expertise and insight.

Thank you, it's nice to be appreciated! [emoji16]

Dave

 

[gatornek]

To little preload and pressure in the turbo housing will start to open the wastegate preventing the desired boost from being obtained. To much preload and you get over boost spikes or erratic operation do to the wastegate not operating as the ECU expects.

Dave, in the video, the guy preloads it (I think) by finding its most taut default position, and then twisting it three more times or 3mm. Is that all that's needed? I imagine its just to give the spring some initial tension, so it is sure to keep the wastegate shut TIGHT. That spring in the turbosmart looked tense as hell by the way. Not sure if maybe it was a 12 psi or what, but he had a tough time giving it the heaveho, to get it over the wastegate lever, after he put the preload in.

So essentially the ECU via the boost controller is going to make a decision point to start routing pressure to the actuator.....the higher the psi rating of the actuator spring, the longer it will take for that rod to actuate the wastegate open, yes? Why would anyone want a tighter spring other than to help keep the wastegate door more tightly closed? I ask that, bcuz it seems to me that you could use the timing of the ECU command to actuate the wastegate (sooner, later) rather than relying on some extra resistance from the rod to delay the effect of opening the wastegate?

Thanks Dave. I echo @EcoVert17 Ive gotten a lot of induction knowledge off of you these past few months! This is madly appreciated.

 

[dgc333]

The spring in the wastegate actuator needs to be strong enough to conteract the pressure in the turbine housing of the turbo that is trying to open the wastegate.

A soft spring rate will require more preload than a stiffer spring to do the job. The ecoboost motor is tuned by Ford using torque targets. If the spring is to stiff and/or has to much preload there may not be enough boost pressure to open the wastegate at a particular target. That is why stiffer spring wastegate actuators need a tune to work right.

Dave