Removing WGFV for good? Mechanical vs N75 boosting

[Jamo]

@Jamo, thanks for all the reading. I've had a good couple of hours today.

Something newsh said has got me thinking that my preference might be to have the majority of boost controlled mechanically, with a bit extra controlled by the ECU at WOT, e.g. with Paul's example of 0.4bar mechanical and 1.0bar ECU totalling 1.4bar, I'd want to switch it around for 1.0bar mechanical and 0.4bar ECU - I'll get a more torquey, high boost part throttle response and quicker spool up from the spring, but if the ECU finds something wrong I should be able to notice not getting the extra 0.4bar. It would also give my 3B a similar overboost feature to ABYs, but without the time- and gear-limits.

for your example you'd have to have 1 bar wastegate spring meaning the ecu cannot reduce boost below 1 bar is that really a safety function??? thats more boost than the stock 3b produces

[S2central.net]

Exactly right Jamo... Each to their own with this stuff. If other people wish to ignore this kind of approach then fine, as long as they aren't surprised when things go wrong down the line if the ECU has been prevented from executing a safety routine.

Paul

[gnutz2]

The most redeeming feature of the n75 valve (i think) is the fact that if correctly mapped on any management it will not show the WG any pressure untill near maximum boost, this uses all the exhaust gas energy to spool the turbine up and ensures no WG creep.

On the other hand if you use a mechanical boost control you cant stop the WG creeping open at 50% of your desired boost level. So when your spooling up the turbo it`s not getting all the exhaust energy that it could do with an n75 valve on.

[newsh]

This is what MRC does with the RS2 turbo, 1 Bar on the spring and 0.8 extra on the WGFV at WOT. I'd like 0.4 extra at, say 3/4 throttle on the WGFV. Ideally it would be graded so a little extra throttle gives a little extra boost, just as it does up to 1 Bar on the spring. The difference being the ECU could reduce the extra boost if something goes wrong, I'm certainly not against that. Basically a map that makes the car feel like the boost is being controlled by a spring when it actually isn't

[S2_Dave]

The most redeeming feature of the n75 valve (i think) is the fact that if correctly mapped on any management it will not show the WG any pressure untill near maximum boost, this uses all the exhaust gas energy to spool the turbine up and ensures no WG creep.

On the other hand if you use a mechanical boost control you cant stop the WG creeping open at 50% of your desired boost level. So when your spooling up the turbo it`s not getting all the exhaust energy that it could do with an n75 valve on.

Read Jamo's link. It's a great article, inlcuding how wastegate creep can be eliminated mechanically.

[gnutz2]

I particularly lice the 3d WG controll of dave walker`s Emerald ECU`s instead of mapping the duty cycle % (33Hz on the n75) against the RPM it uses rhrottle position as the third variable.

Mapping duty cycle against RPM gives the car the on off feel, or full boost at half throttle feel because if your travelling along at say 4000 revs at half throttle and the duty cycle is set to give you 16psi thats what your gonna get if there is enough exhaust flow to give it.

Obviosly the motronic ECU has excellent WG control but im using aftermarket.

This is why im annoyed i cant use Emerald management

Hurry up Dave.

[gnutz2]

Read Jamo's link. It's a great article, inlcuding how wastegate creep can be eliminated mechanically.

My friend uses a mechanical valve thet does`nt show the WG any pressure till near full boost and thereafter regulates the pressure.

It`s not a bleed valve either because it only has one pipe in and one out.

[Faheemo]

Is ther any performance replacement for an N75 solenoid ?
After boosting the car to 2bar the N75 has seemed to have given up and is causing a boost leak to the turbo inlet side.
I pressure tested my system the other day and the N75 was the problem.
Want to keep a solenoid style boost regulator so ecu can control boost.

[gnutz2]

Not too sure what you`re getting at there you could check the resistance of the n75this should tell you if it`s broke or not.

A leak through the n75 valve?? surely if it`s making 2 bar boost it`s working fine.

[newsh]

Not too sure what you`re getting at there you could check the resistance of the n75this should tell you if it`s broke or not.

A leak through the n75 valve?? surely if it`s making 2 bar boost it`s working fine.

It can leak where the solenoid is fixed on. Or the platic can crack..

[kwlw]

Is ther any performance replacement for an N75 solenoid ?
After boosting the car to 2bar the N75 has seemed to have given up and is causing a boost leak to the turbo inlet side.
I pressure tested my system the other day and the N75 was the problem.
Want to keep a solenoid style boost regulator so ecu can control boost.

034efi has one ask Corey here for details. Actualy I don't think new valve can leak@2bar. I have few, some older ones, one new one from RS4. Older ones show signs of wear in terms of airtightness and reaction time. New one doesn't have those problems. That's why it is installed in my coupe .

Sau

[A80Avant]

i was wondering reading all this about a few things..

If the OEM wastegate spring is indeed 0.4bar and the car is tuned to 1.8bar and something happens and it falls into limp mode,this means that it will only boost to 0.4bar,right?

Well if it boosts to 1bar rather than 0.4bar would it be noticable to the driver that something is wrong and it needs to be checked??? SO the driver can drive easily and not harsh until he reaches a place to notice what is wrong?

Im For the WGFV solution but also im puzzled with the ability or option to increase the tention of the wastegate spring rather than get a new stiffer one.A stiffer spring will ultimetly get you into higher boost figures even with the N75 pluged on which sometimed are unwanted.Limp mode does not exist with the stiffer spring anymore?Then this means that with the use of a stiffer spring,the WGFV is absolete and basically the car should be tuned with mechanical boost?NO failsafes?

SO the middle way to go is just stiffen the spring you already have to a desired place so that the N75 with it's duty cycle still sends the signals it is written to do by the remap,but since the spring is harder instead of 18bar over it now produces for example 2.0bar ??? and if the steady boost was previously programmed to go to 1.5bar it now goes to 1.7bar?

Can i make that assumption or is it wrong??

AND finally,if this is true,then how does a small pressure increase effect the air/fuel ratio ? Is the remap programmed just to achieve a certain level of ratio and whatever happens it does so?(so long as the injectors,pump can provide)??

[Faheemo]

034efi has one ask Corey here for details. Actualy I don't think new valve can leak@2bar. I have few, some older ones, one new one from RS4. Older ones show signs of wear in terms of airtightness and reaction time. New one doesn't have those problems. That's why it is installed in my coupe .

Sau

according to some sources the "N75 Race" from 034 is just a oem variant of the usual N75.
It was not made for after market performance setup as such.
When testing my N75 -
I pulled out the two hoses that connect to the waste gate and the other that goes to turbo inlet (between MAF and compressor).
Strapped the leak device on and pressurized the system.
the N75 leaked boost @ approx 1.5 bar from the long nipple that goes to the turbo inlet pipe.
2nd N75 that broke on me in 2 years.

Now i looking at industrial pressure solenoids to do the similar job of N75.
else its pressure regulators and relief valves the manual way.

[rs2315]

I know what you you mean Jamo, I don't like the thought of not running one. I wonder if Rosses went there?
Automark has a good rep...

Now that I've got GT500 old RS2 should I be concerned that the N75 valve has been removed and the car is running on mechanical boost and not by the ecu?
Am I right in thinking the wastegate is the bit of kit that has a hex nut in the center.
If so mines screwed well down, is that also a clue to the mechanical boost set up?
rs2315.

[4WheelDrifter]

Now that I've got GT500 old RS2 should I be concerned that the N75 valve has been removed and the car is running on mechanical boost and not by the ecu?
Am I right in thinking the wastegate is the bit of kit that has a hex nut in the center.
If so mines screwed well down, is that also a clue to the mechanical boost set up?
rs2315.

Big hex nut on the WG? That's a sure sign that the tuner doesn't what a boost map is.

When I first had my car it had the N75 disabled. I set mechanical boost to 0.4 bar and got MrC to sort out some proper chips asap.