Adjusting wastegate spring for less boost

[foxdie]

Hi all,

I'm not sure if this has been done, has anyone adjusted / replaced the wastegate spring on the 6A13TT?

I'd like to try and lower the stock wastegate pressure to somewhere around 0.1 bar (1.5 PSI), yes 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.

Naturally I will still be controlling boost via ECU control (or hopefully soon an EBC) for those 1.25 bar (18 PSI) TLGP (http://www.clubvr4.com/forum/showthread.php?25019-Traffic-light-races)'s :satan: but the plan is to lock the car down via a hidden keyswitch that sets the WGDC (http://www.clubvr4.com/forum/showthread.php?53046-Boost-Control-via-Factory-ECU&highlight=wgdc) to 0% /Hmmm

[Wodjno]

Wtf ?????

[foxdie]

Wtf ?????

Yeah I know I know, I'm an oddball ;)

[Wodjno]

No.. Not Oddball. If u are, i am also :D Just something i was discussing as an idea earlier with a club member. But for a totally different reason !! Freeeeeaky /yes

[foxdie]

I've been thinking about this for a long time, I tried detuning my cars boost as low as it'd go for some decent around-town economy, but ultimately it bottoms out at the 0.5 bar wastegate pressure.

Ps. I'm psychic... :inquisiti

[Wodjno]

My idea was for Fuel saving while pottering around. Stopping the little tubs from spooling so quickly low down and then the ECU dumping in loadsa fuel. Decreasing the spring pressure to around 1-2 psi and along with wastegate creep would keep manifold pressure negative. (Hopefully)

[Kenneth]

Before you try this, I would disconnect the wastegate and wedge it open.

Fluids flow the path of least resistance, as soon as the resistance in the wastegate opening (and lets face it, it isn't THAT big) results in flow across the turbine, you will get turbo spooling.

The question is at what point/RPM this happens and if having 'very low' spring pressure will make much difference in the boost level at higher RPMs.

[psbarham]

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.

[foxdie]

Interesting, very valid points, might be worth investigating alternative methods of bleeding boost then.

[Kenneth]

I would be very interested in seeing fuel economy results with the wastegate open or at very low wastegate spring pressure.

I am not convinced that it will improve fuel economy over a well trained right foot as even below positive pressure the turbo is spinning giving possible VE gains and causing potential fuel use if you are a bit too heavy footed. By the time you get to boost, chances are that you have done the damage in fuel use already.

[Wodjno]

Is there anyway that the system could be cheated? By making the wastegate see poisitive pressure below a certain throttle position.

[Wodjno]

Is there anyway that the system could be cheated? By making the wastegate see poisitive pressure below a certain throttle position. Suppose it would need some kind of lekky pump compressor ? That could be turned of by a switch above a specific throttle position?

[foxdie]

Stop reading my mind Glenn!

:kiss:

[scott.mohekey]

Replace the mechanical solenoids with electrical ones?

[Kenneth]

a vacuum canister which is essentially a reversed wastegate actuator. A correctly sized one would, when activated have enough pull to open the wastegate against the standard actuator.

Would be and interesting job to hook up and control though.

[Wodjno]

Suppose it would need some kind of lekky pump compressor ? That could be turned of by a switch above a specific throttle position?

What about back pressure in the exhaust, say just before the cat converter(for those who have them fitted) A pressure line to fool the wastegate into thinking there is positive pressure in the manifold.Thus opening the wastegate. Above a certain TP it can be cut off via a valve triggered by TP?

[foxdie]

I started looking at 12V compressors like this; http://shop.wiltec.info/product_info.php/info/p5137_Airbrush-Battery-Compressor-Set-08ADC-KB.html

Stupidly expensive for a theory.

[Kenneth]

Isn't likely to be sufficient exhaust back pressure to do that, at least not there. If you are flowing enough for that sort of pressure, chances are you are creating sufficient boost.

[Wodjno]

I started looking at 12V compressors like this; http://shop.wiltec.info/product_info.php/info/p5137_Airbrush-Battery-Compressor-Set-08ADC-KB.html

Stupidly expensive for a theory.

Yeah we need free pressure /yes

[Wodjno]

Isn't likely to be sufficient exhaust back pressure to do that, at least not there. If you are flowing enough for that sort of pressure, chances are you are creating sufficient boost.

I did wonder what sort of pressure would be there on light throttle.. I suppose it all comes down to the restrictiveness of the exhaust also. So where else can we get some free postive pressure ?

Spare tyre in the wheel well /Hmmm

[foxdie]

http://is.gd/6Y4gIp

PMSL!

[Kenneth]

You could either store boost pressure somewhere (canister) but that requires having boost at some stage first.
The best bet for "free" actuation is a vacuum canister (like the brake booster, you COULD actually use the brake booster...) which stores vacuum and when activated will connect to another pneumatic cylinder or some such which will open the wastegate.

[Wodjno]

Sure we could use the spare wheel for constant a constant pressure source. A pressure regulator inline to keep say a constant 8-9 psi at the wastegate. And then a switch valve that switches at 50% throttle and above so the wastegate see's no pressure and the Boost Solenoid takes over ?

[Kenneth]

You would be better off with a dive cylinder or some such if you want to go to those lengths.

[foxdie]

How would you then replace the air in the tyre?

[Wodjno]

How would you then replace the air in the tyre?

Via a electric tyre pump that gets triggered only when the tyre pressure falls to say 10psi ? They can be set to shut off at a set pressure also.

[Wodjno]

Anyway.. Before any of the above is tried, the 1 thing to test is as Ken says! Wedge open the wastegates to see if it has any adverse affects and if any fuel economy gains whatsoever? So whose gonna volunteer to drive like miss daisy for a week :D

[Kenneth]

If you got to this effort, you are better off with a small accumulator (you could get one off an old AYC pump unit) and a regulator setup. This would allow sufficient pressure so that the pump only has short duty cycles (and it is useful that those pumps can generate quite a bit of pressure)

Via a electric tyre pump that gets triggered only when the tyre pressure falls to say 10psi ? They can be set to shut off at a set pressure also.

[Wodjno]

If you got to this effort, you are better off with a small accumulator (you could get one off an old AYC pump unit) and a regulator setup. This would allow sufficient pressure so that the pump only has short duty cycles (and it is useful that those pumps can generate quite a bit of pressure)

Agreed /yes Good thinking :D

[Davezj]

i suggested this a wile back to see what would happen for a fuel saving option.

one of the issues raised was the compression ratio of the engine is very low to cope with the turbos. there was some issue with running an engine with a low comression ratio with out working turbos.
i will see if i can dig the thread out.

here you go,
http://www.clubvr4.com/forum/showthread.php?34189-what-would-happen-if-you-forced-the-wastgate-to-stay-open&highlight=wastegate

[Wodjno]

i suggested this a wile back to see what would happen for a fuel saving option.

one of the issues raised was the compression ratio of the engine is very low to cope with the turbos. there was some issue with running an engine with a low comression ratio with out working turbos.
i will see if i can dig the thread out.



http://www.clubvr4.com/forum/showthread.php?34189-what-would-happen-if-you-forced-the-wastgate-to-stay-open

[Davezj]

edit my post but glenn beat me to it.
and already posted like, you have got to be quick round here!

[Wodjno]

Well thats good info and good constructive arguments /yes But!

The prrof is in the pudding, and the pudding still hasn't been served :D

[jjayokocha]

is there no way to have a seperate map for "no boost map"? it would save a lot of hassle.

[foxdie]

And it's that very reason I suggested 0.1 bar of boost, just enough to kind of break even with a bit of wastegate creep :)

[Wodjno]

is there no way to have a seperate map for "no boost map"? it would save a lot of hassle.

even without no boost. The wastegate spring will stiil hold shut until it reaches it's spring pressure. Thus you will get boost..

[swinks]

Well, talking about potential fuel savings - rubbish. No boost, longer applying load on engine to achieve the same thing, bigger fuel consumption in the end. IMO recent wastegate pressure is an optimum. Rather recommend you to drive for some time Galant v6, it's not as great once you apply load on engine.

[Davezj]

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.

as soon as you want to boot it you can turn the boost up.

[jjayokocha]

well then just get a really crap spring for the wastegate and switch off the ebc and ur sorted.

[Davezj]

no you can't do that.
because as stated above it will reduce the minimum pressure achievable but when you turn it up the waste gate will not be able to stay shut as the boost climbs the EBC or other control system will not be able to bleed off/stop all pressure over 0.1 bar.

[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 :P

[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? :D

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? :D

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.