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R33 Gts25t Standard Turbo Activator Point

h2k

By h2k,
in Engines & Forced Induction

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h2k Enthusiast

h2k

Posted
Posted

Im running a R33 gts25t with 3" exaust, filter and a large FMIC.

And Im getting a bit to much boost. Im getting boost up to 0.9Bar after 4500rpm.

Im getting fuel cut 0.8Bar so I want to run 0.75 in boost untill I can afford a fuel controller and/or fuel pressure regulator.

I removed the standard original 2-step boostcontroller and tried to run boost from the compressor side directly to the solenoid regulating the wastegate arm.

Wich should give me the lowest possible boost, but still Im boosting 0.9-1.0Bar.

I took off the heat shields on the turbo and connected a compressor directly to the solenoid and measured with a gauge when the actuator starts to move the arm and when it is fully opened.

It starts to open about 0.5 bar and reaches it's max open wastegate at 0.9Bar.

Is this correct?

This seems wrong to me since the car ran fine(max 0.6bar) with the original 2-step controller before I installed the intercooler. Before I had only exaust and airfilter. But this problem occured after I installed the FMIC.

Now I have tried a manual bleed valve and a Apexi AVC-R to controll boost but they can only INCREASE the boost.

Now what I need is to change the actuator so that it starts to open the wastegate at about 0.2Bar and is fully open at about 0.6Bar and if I want to increase the boost I can use a boostcontroller/bleed valve to increase it to whatever I want from there.

Is it possible to adjust the standard actuator by opening it and modifing the springs or something like that?

h2k Enthusiast

h2k

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Posted
sounds like the wastegate has been changed from the factory one, or it is sticking. do you have an aftermarket dump pipe? that may be the cause of it sticking if it is a really crappy one. stock wastegate is 5psi.

The wastegate and diecast downpipe with the lambda probe is original and I dont think it is sticking, I've tried disconnecting it from the rod comming from the actuator and the wastegate arm moves very lightly from closed to open and it feel right.

However if we say that the waste gate arm is a 0 degree angle when it is closes, and fully open at 90 degree angle. The rod comming from the actuator only pushes it open about 45 degrees.

I've tried adjusting the lengt of the rod but that only resulted in the wastegate beeing about 15 degrees open with no boost, wich makes the car really sluggish. And 60 degrees open with full boost(0.9 bar).

Tomorrow I'll try hooking the wastegate arm of the actuator rod and running the car with the wastegate completely open. If it still boosts then the wastegate is clogged or my engine is producing to much exaust and my wastegate is to small to deal with it.

h2k Enthusiast

h2k

Posted
  • Author
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Today I tried to unhook the actuator rod from the wastegate and I held the wastegate completly open with a steel wire like this:

img124.jpg

Wich should send as much exaust possible away from the turbo.

Low revving the car was very sluggish but when I passed 4500rpm the boost just launched like a rocket all the way up to 0.9 Bar in 3rd gear.

img123.jpg

Wich means one of 2 things:

1. The wastegate is clogged up by something, burnt oil remaints etc. But the arm moves very lightly and it makes a "dry" sound when I close it.

2. The wastegate on the T25 turbo is to small to dump all the exaust on a RB25DET engine when you have a podfilter, 3" exaust and a large FMIC.

Does anybody else have the same mods as me and are still able to run at original boost?

I've ordered a fuel pressure regulator so I don't run with to little fuel and to much air since that will kill my engine soon :\

otto Collaborator

otto

Posted
Posted

Hey mate

my car started doin exactly what your describing when i got cai exaust and cooler i put it down to the wastegate not being able to waste enough.

i disconnected the actuator and held the wastegate wide open like you and couldnt get the car to run below 12psi, I ported the wastegate as much as i could and now the lowest the car will run is 9psi which im happy with seeing as i run the car at 11psi, although if i give it a sudden hit in second or first gear it will spike horribaly to 14-15psi(im guessin the wategate is still abit inadiquet) the spiking seems to taper off the higher the gear im in.

Ide love to know how othe peoples cars run when there wastegates are held fully open???? comeon guys give it a go

h2k Enthusiast

h2k

Posted
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Another theory is that I understand that the ECU monitors the air beeing sucked trough the filter and when it gets to much air the ECU respons with a fuel cut function by richening the air/fuel ratio to decrease boost.

But since I have increased the air supply with filter and larger intercooler, and the exaust with free flow, it just keeps produsing exaust making the wastegate to small.

I've ordered a HKS fuel cut defencer as I've talked to a guy having the exact same setup as me and is having no problems adjusting the boost down under 0.8 bar if he wants with a bleed valve. Only things he has that I do not is a HKS fuel cut defencer and a adjustabel fuel pressure regulator.

mad082 Grand Master

mad082

Posted
Posted

i have a cooler, full exhaust and pod and the lowest i think i can run is 8psi (0.55bar). where is the gauge, and wastegate taking its reading from? and what sort of cooler is it? if it is reading the boost from before the cooler, but wastegate is reading from after the cooler, and it was a cheap cooler then it could be more restrictive than the stock cooler, therefor the air flow is less. and the wastegate is reading from a lower pressure area than the gauge.

BHDave Grand Master

BHDave

Posted
Posted

The wastegate simply can't flow enough to maintain a lower boost, which you have proven by wiring it open.

I suspect maybe the factory dump is not allowing as much air out as an aftermarket one would when you consider it is angled pretty sharply back into the main pipe, but it's just a theory.

h2k Enthusiast

h2k

Posted
  • Author
Posted (edited)
i have a cooler, full exhaust and pod and the lowest i think i can run is 8psi (0.55bar). where is the gauge, and wastegate taking its reading from? and what sort of cooler is it? if it is reading the boost from before the cooler, but wastegate is reading from after the cooler, and it was a cheap cooler then it could be more restrictive than the stock cooler, therefor the air flow is less. and the wastegate is reading from a lower pressure area than the gauge.

I have 4 separate boostgauges to make sure Im not getting a wrong reading.

One is the original VDO gauge.

One gauge wich is connected to the same outlet as the VDO gauge with a T-piece.

The apexi avc-r digital gauge wich I have connected with a t-piece between the inlet and the boost dump valve.

One gauge wich is connected with a t-piece where the actuator gets its reference boost. One the cold side of the intercooler flow, just about in the middle between the IC and the throttle.

I'm getting consistant boost levels on all 4.

The cooler im using is a large Hybrid intercooler with hardpipe kit and silicon hoses.

Core size 600mmx300mmx77mm with 3" inlet and outlet.

I'm leaning more and more towards the theory that the fuel enrichment funtion on the ECU is forcing me to produce to much exaust, and with a to large exaust there is no restriction there so the turbo spins up to much.

I live in norway and we don't have a dyno within a 10 hour drive away from where I live and it costs blood to use.

and adding a boostcut defender won't change the problem as all they do is change the airflow meter signal once it gets past a certain voltage. has nothing to do with boost control.

It's not a boostcut defender, its a fuelcut defender. Though the fuelcut is activated to prevent overboosting. But in my case its producing overboost :\

Edited by h2k
mad082 Grand Master

mad082

Posted
Posted

fuel cut/boost cut, same thing, different name. the fuel cut kills the motor. it shuts everything down. it is like a violent rev limiter, so unless you are having that happen a fuel cut defender won't do anything. it doesn't control afr's. it would be your ecu making it rich. only fix if it is the ecu is an aftermarket ecu.

the first thing i would do is upgrage the dump pipe and see what that does. if the wastegate isn't flowing enough then the stock dump pipe won't be helping the situation.

paulr33 Grand Master

paulr33

Posted
Posted

its neither. its not boost cut and its not fuel cut. its actually excess airflow protection. when the ecu see's certain levels of "air" via the airflow meter signal it activates its protection mode which retards the timing a lot and richens up to protect itself (the engine). the engine doesn't shit off, it doesn't cut out, it doesn't cut spark.

it should feel flat and empty, and nothing more. maybe pop and fart a little bit cos its mega rich but nothing more. its oftenly referred as towing a boat all of a sudden or driving against an invisible brick wall

mad082 Grand Master

mad082

Posted
Posted (edited)

well i have it happen and its not a flat spot. its a violent cut in power, like hitting a brick wall, not driving against it. it is basicaly like turning the key off for half a second.

a guy i was speaking to that knows about it from other cars, as well as skylines, said that it isn't just rich and reatard mode. it basically shuts the ecu down.

Edited by mad082
h2k Enthusiast

h2k

Posted
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Posted

I installed a HKS fuel cut defencer this weekend and took it out on track day, adjusted the cut defender until the "rich and retard" point no longer occured and now I can adjust my boost like I want and the fuel popping in my exaust because it lowers the timing is gone.

I have also installed a air/fuel ratio gauge to make sure im not running lean air/fuel mixture and now its a hole world of a new car. Runs like a champion >_<

The conclusion is: when you upgrade airfilter, intercooler and 3"exaust the RB25DET ecu riches fuel and retards timing because airflow increases. Wich again makes so much and thick exaust that the standard T25 exaust wastegate cannot get rid of excess exaust and boost spikes above default 0.6 Bar.

Funtime :)

Bilde147.jpg

Sydneykid Grand Master

Sydneykid

Posted
Posted (edited)

Be carefull, if you have installed an A/F ratio meter off the standard slow and narrow lambda sensor then you CAN NOT rely on the readings. The standard lambda sensor only works around stoich (the narrow bit) and very slowly even then. It's for closed loop idle and cruise use only.

You need a fast and wide lambda sensor and a suitable A/F ratio meter. Since the dyno is so far away, I strongly suggest that you spend the $700 and buy one.

A boost cut defender is simply a voltage clamp, it stops the ECU seeing voltage from the AFM above the limit that you have set. As the airflow continues to rise above that point, the A/F ratios are getting leaner and leaner. There is more air going into the engine that the ECU doesn't know about, so it doesn't inject more fuel.

If you are going on with more mods I strongly suggest either a Power FC or at the very least an SAFC. So you can control the AFM voltages (that the ECU sees) and therefore adjust the A/F ratios.

That's when the A/F ratio meter becomes a very useful tool. I am currently using Tech Edge, details follow;

http://www.skylinesaustralia.com/forums/in...56&hl=tech+edge

>_< cheers :)

Edited by Sydneykid
mad082 Grand Master

mad082

Posted
Posted (edited)

turbosmart do a fuel cut defender where you can adjust the ramp of the air flow voltage so it adjusts the afr somewhat. it has 3 dials on it. the first is clamp, the second is ramp and the 3rd is release (where it lets it boost cut).

Edited by mad082

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