Adjusting wastegate spring for less boost

[swinks]

but the point is you will be drive in a fuel saving mind set when you activate the low boost option, so you will not be putting your foot down hard in bumble about town driving.

I'm already driving like that with stock wastegate . No difference to Galant v6 or even GLS when keep my foot off. So... question again... what's the point?

[Kenneth]

one option is to loosen the throttle cable so you can't actually get WOT

[Adam.Findlay]

Im pretty sure you need a somewhat decent spring to push high boost pressures. as like with cars with external wastegates a soft spring can handle low to meduim boost settings fine but as soon as you try get high levels of boost the spring cannot hold the gate shut enough or something like that. so although you will be able to drop the boost pressure to almost nothing (depending on how much the internal gate can bypass the turbine) your high boost settings will be unstable.
TLDR soft springs could harm your "performace" boost settings negativly

[lathiat]

Yeah I was thinking that myself.. the spring needs to be approximately within range of your desired boost I think. I doubt a 1.5PSI spring pressure could be bled up to 15PSI.

[SEAN-NZ]

what about a separate pipe that bypasses the turbo? with a manual valve or butterfly valve, so you can keep as much exhaust gasses from turbo and wast egate as possible, could be expensive i would imagine

[lathiat]

I really think if you engage 0 boost (so ~6PSI).. enable a say, 120KM/h speed limiter (depending on your countries highest speed limit).. you'd be right enough.

[foxdie]

"0 boost" is still 0.5 bar of boost up to 120 KM/h.

It's not about limiting speed, it's about limiting acceleration and boost. Adjusting the throttle cable is a bad idea... but thinking out aloud... how about a drive-by-wire conversion?

Something akin to an Arduino with a servo / stepper motor attached to the throttle body (or driven remotely via the existing throttle cable), accelerator pedal detached from the throttle cable and connected to either a variable resistor or even better, an optical encoder for accuracy.

Arduino sits there, monitors accelerator position and remotely actuates the throttle body, in eco mode the arduino limits maximum throttle to about 50% with a slow response (ie. you floor it, throttle position gradually changes over about 1-2 seconds to 50%). In "sport" response time is instant with maximum throttle being 100%.

There'd have to be safeguards in, I started to design a cruise control system with an automatic safety cutout in the very rare case of a hardware malfunction. Thinking about it, there's nothing to say the project couldn't be applied to total throttle control. This is how it's done in most recent sportscars anyway.

The idea is wayyyy out there, but it's crazy, crazy like a fox, so it might actually work

[pezza]

Hi all,

......es I'm aware it'll make the car flat as a fart, that's exactly what I'm going for as I'm looking at this for a valet mode / anti-joyride feature.

As an aside to the boost limitation discussion and focussed more on performance lockdown as mentioned in the first post; the ecu in my camaro can restrict the engine/car to a user defined speed/revs via a switch. Many of the guys in the US use this for implementing a valet mode. I am not sure if our ecu's are capable of doing the same or even allow a switch to activate a stored setting in this way. (plus there are other factors as to whether a flashable ecu is required)

This method obviously wouldn't be any use for fuel saving via means of boost restriction but can be effective in other ways.

[foxdie]

All ROMs let you adjust the vehicle top speed limiter and engine RPM limiter, however Kens KS Mods 2.0 ROM lets you do it per map so you can implement a switchable limiter... but alas it doesn't limit the stock wastegate boost.

[lathiat]

"0 boost" is still 0.5 bar of boost up to 120 KM/h.

It's not about limiting speed, it's about limiting acceleration and boost. Adjusting the throttle cable is a bad idea... but thinking out aloud... how about a drive-by-wire conversion?

Something akin to an Arduino with a servo / stepper motor attached to the throttle body (or driven remotely via the existing throttle cable), accelerator pedal detached from the throttle cable and connected to either a variable resistor or even better, an optical encoder for accuracy.

Arduino sits there, monitors accelerator position and remotely actuates the throttle body, in eco mode the arduino limits maximum throttle to about 50% with a slow response (ie. you floor it, throttle position gradually changes over about 1-2 seconds to 50%). In "sport" response time is instant with maximum throttle being 100%.

There'd have to be safeguards in, I started to design a cruise control system with an automatic safety cutout in the very rare case of a hardware malfunction. Thinking about it, there's nothing to say the project couldn't be applied to total throttle control. This is how it's done in most recent sportscars anyway.

The idea is wayyyy out there, but it's crazy, crazy like a fox, so it might actually work

The main issue with drive by wire is you absolutely do not want your system to go mad.. veryy.. very.. dangerous possibilities. I would personally be quite hesitant to implement a home made system here.. cruise control systems are a little easier because they can limit the max acceleration applied, etc, where as drive by wire requires the ability to do snap full throttle etc.

Factory drive-by-wire systems generally have dual TPS sensors that have a different output curve and are compared to ensure that the sensors are not faulty, etc...


Here's another thought for you.. my understand of the TCL throttle body is it has a vacuum driven ability to pull throttle input.. I am not sure how adjustable it is.. but you could probably drive your throttle pull using some external device (or even some custom ECU programming).. to limit throttle without having to replace the system entirely.. and still using a factory throttle body part.

I have a TCL throttle body here I might have a closer look how it works and how adjustable or not the input is.

[The Vee]

the other thing to remember is that a weaker spring will result in less seating pressure for the wastegate,

A mate single turbo'd his rx7 and for wet weather use he fitted a 0.3 bar wastegate so it would be usable but it resulted in not being able to make constant boost once the tub got spooling properly.

This

[Kenneth]

if you want a valet mode which drops power, use a switch and map one of the ECU configurations to run very retarded ignition and very lean AFR so that you essentially cut power above a certain load point

[wintertidenz]

How about very low wastegate duty cycles tied to one of the maps, and a rev limiter of let's say 3500 rpm?

[Kenneth]

straight fuel cut is quite harsh (harsh is bad for mechanical components), especially under load. You would need to use a few hundred RPM to drop power using the mapping first.