1UZ TT Turbo Pulsating

[mshawari1]

May be that exhaust throttle or hole (To bypass the turbo) in the turbine side is open !! or stuck ! so this happen ….​

 

[mshawari1]

If you have that kind ​

 

[1ndecent]

Just took a couple of pics of the waste gate actuators, as you can see i had to modify one of them by moving the mounting bracket from the front of the compressor housing to the rear of it thus also had to shorten the actuator lever. Would this have any effect?

If the preload of the wastegate spring has been changed, it will increase the likelihood of one turbo blowing back through the other. Was the wastegate pushrod shortened by EXACTLY the distance you moved the actuator by?

 

[Pro]

if one isn;t opening before or after the other one, then no, it shouldn;t have any effect at all.

the only way i could see this having an effect is if one is partially open all the time, in which case, that would be the turbo you would feel pressure coming out of the inlet.

 

[4000GT]

Hmm kinda suggesting you do some reading yourself as the reasons are laid out in any decent turbo text. Yes this is a great place to learn but you are asking questions on someone else's thread...maybe i'm just old skool but i learnt most of what i know by teaching myself or maybe i'm just a cranky old bastard

However, free revving will easily see both surge and reversion of the throttle plate....both of which will pulse air out of the comp housing. I can do this easily any any turbo can i have owned or worked on. Third way this could happen is if the turbo wastegate control gets out of sync ie. one turbo is boosting and the other is not...the air takes the easiest path one of which will be out of the non boosting turbo

technical enough???

Well no, its not technical enough... it doesnt seem like anyone is addressing his issue. Which is what I have in mind when helping troubleshoot his problem.

I start by removing the air intake filters, i then get someone to hold thier hands close to the turbo intakes while increasing the engine rpm to around 3000, you can feel the turbo's suck you hands in then they blow back then suck in then so on.

He is free revving it slowly to 3,000rpm, the BOV should not be open, any pressure is forced into the motor (least resistence path is into the combustion chamber with no chance of resonance of the TB plate). Yes there is some off the valves, but its nominal on FI cars as its overcome by pressure from the turbo.

 

[JBrady]

Certainly sounds like mild compressor surge to me.

At part throttle the compressors can and will make pressure between the compressor outlet and the throttle plate. If the BOV is not bleeding this pressure then the turbo(s) can surge. Compressor surge occurs when there is insuficient air flow for a given pressure. At very low air flows (such as throttle restricted slow reving and cruising) the wastegates are closed (so they are not involved in this condition) and the compressors are moving air and creating pressure at the throttle plate. Look at a compressor map and at very low air flows it takes very little boost to cross the surge line.

Remember at cruise at say 45mph you are only needing say 10rwhp. This is a small amount of air mass. With 2 turbos this mass is cut in half. But these turbos are still moving air. As the pressure goes above the stable range for these compressors at THIS low airflow surge is encountered. Under surge the air will momentarily reverse. NOT the compressor direction just the air flow direction. As soon as this happens there is enough room for the compressor to move air again. With 2 turbos this easily becomes an occillating condition as describe in the original post here.

A true compressor bypass valve will correct this. A weaker spring in the BOV may also fix the problem. You simply need to bleed the pressure under these conditions.

 

[Hillbilly]

Certainly sounds like mild compressor surge to me.

At part throttle the compressors can and will make pressure between the compressor outlet and the throttle plate. If the BOV is not bleeding this pressure then the turbo(s) can surge. Compressor surge occurs when there is insuficient air flow for a given pressure. At very low air flows (such as throttle restricted slow reving and cruising) the wastegates are closed (so they are not involved in this condition) and the compressors are moving air and creating pressure at the throttle plate. Look at a compressor map and at very low air flows it takes very little boost to cross the surge line.

Remember at cruise at say 45mph you are only needing say 10rwhp. This is a small amount of air mass. With 2 turbos this mass is cut in half. But these turbos are still moving air. As the pressure goes above the stable range for these compressors at THIS low airflow surge is encountered. Under surge the air will momentarily reverse. NOT the compressor direction just the air flow direction. As soon as this happens there is enough room for the compressor to move air again. With 2 turbos this easily becomes an occillating condition as describe in the original post here.

A true compressor bypass valve will correct this. A weaker spring in the BOV may also fix the problem. You simply need to bleed the pressure under these conditions.

This is exactly what is happening

What is a true compressor bypass valve ?

 

[1ndecent]

Compressor bypass valves open when vacuum is present in the intake manifold. BOVs require an amount of pressure to be present in the intake piping AS WELL as vacuum in the intake manifold, to open.

When I googled 'compressor bypass valve' the first result was:

http://wwwrsphysse.anu.edu.au/~amh110/Technical_pages/blow_off_valve.htm

Which has a slightly longer explanation. OE style compressor bypass valves are cheap, the last one I bought from Petroject in Osborne Park was $30-$40.

Come to think of it, I still have it sitting up in the pallet racking in a crate of 7M engines. If you want to borrow it to see if it helps you are welcome to pick it up from my workshop in Balcatta.

 

[JustenGT8]

2 things spring to mind...you are hitting the surge line ie the turbo is trying to make too much boost too low in the flow range which suggests to me you need the bigger a/r turbines...OR...your boost control is mismatched so your turbos are alternating making and dropping boost.

LOL Thanx JBrady, just what i said in the very 1st response

External gates are great to solve this prob as most have a vac port on top to open the wastegate under cruise (vac). Personally, i have never used this as my turbos have always had a reasonably large turbine which makes this condition rarer.

 

[JustenGT8]

Well no, its not technical enough... it doesnt seem like anyone is addressing his issue. Which is what I have in mind when helping troubleshoot his problem.

Jeez mate, read my very 1st reply ie SURGE!!!!!!!!. The other potential reason explanations are educating you seeing you asked.

 

[dass]

Mine TT 1uzfe does the same, as did the 2 x gt30 on the 2jzgte.Has nothing to do with waste-gates as the wastegate is closed at the pressure it occurs.It is called compressor surge . The compressor side is flowing more the the engine can consume and flows/spits back out the inlet side.Very common most people just live with it.A larger exhaust housing and or turbine size will go towards fixing the problem.

 

[Pro]

thanks dass - my thoughts as well.

 

[4000GT]

LOL Thanx JBrady, just what i said in the very 1st response

External gates are great to solve this prob as most have a vac port on top to open the wastegate under cruise (vac). Personally, i have never used this as my turbos have always had a reasonably large turbine which makes this condition rarer.

To see compressor surge free revving to 3,000rpm without load (assuming its not on a dyno?), is fairly extreme. Its got nothing to do with the WG at all...

 

[JBrady]

To see compressor surge free revving to 3,000rpm without load (assuming its not on a dyno?), is fairly extreme. Its got nothing to do with the WG at all...

Not free reving. Steady state cruising. Read my post again as I describe how this happens.

 

[JBrady]

LOL Thanx JBrady, just what i said in the very 1st response

External gates are great to solve this prob as most have a vac port on top to open the wastegate under cruise (vac). Personally, i have never used this as my turbos have always had a reasonably large turbine which makes this condition rarer.

This is correct and for the people wondering about this is why wastegate action CAN effect this condition. As Justen just stated using a vacuum port on the actuator can open the wastegate reducing the compressor power at cruise and light throttle where this surging occurs.

 

[4000GT]

Not free reving. Steady state cruising. Read my post again as I describe how this happens.

Right so someone was holding their hand over your turbo while you were cruising at 3,000rpm? Were they sitting in the engine bay or something?

I start by removing the air intake filters, i then get someone to hold thier hands close to the turbo intakes while increasing the engine rpm to around 3000, you can feel the turbo's suck you hands in then they blow back then suck in then so on.

 

[JustenGT8]

To see compressor surge free revving to 3,000rpm without load (assuming its not on a dyno?), is fairly extreme. Its got nothing to do with the WG at all...

External gates with vac port are specifically setup to open under cruise...primarily to improve gas flow, which in turn can influences a number of factors, as it doesn't have to pass thru the turbine.

If you have a small turbine then you can get positive pressure under cruise conditions and this may cause surge because, as Jbrady says, your airflow requirements are very small. The vac port equipped external WG will prevent this.

As you say this is unusual with a free rev but you certainly can produce boost with free rev so if the turbos are that mismatched then i have no probs believing they are going into surge. Without the car harder to say any more

 

[JBrady]

Right so someone was holding their hand over your turbo while you were cruising at 3,000rpm? Were they sitting in the engine bay or something?

No, he also has the problem while cruising.

OK should of said this before, thought i had....
But it also has this problem when i drive the car.
I can drive along at about 3000 rpm in any gear and its fine but if i decrease rpm slightly i get the surge. Under accelaration its ok and when changing gears the bov vents and i may get a little amount of surge.
It seems to be mainly at the point where the bov is not able to vent that it does it.

In fact I think that the cruising surge is what inspired him to do the free rev test. Make sense yet?

Again, look at a compressor map. Consider the small amount of mass air flow needed with very little throttle cruising at 2500-3000rpm (10hp requires apx 1 pound air flow/min). Divide this 1 pound by 2 turbos and each is only moving 1/2 pound per min. Look at the 1/2 pound line and see how LITTLE boost is needed to chart UNDER the surge line. Since these efficient turbos are spinning at cruise they will create some pressure between their outlets and the throttle plate. This is the condition producing the surge. Either a compressor bypass or external vacuum opened wastegate will address this. Since these turbos are integral WG I recommended the bypass.

 

[JBrady]

Here is the map for Hillbilly's GT28R turbo (part number 466541-1)

http://www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT25/GT2560R_466541_1.htm


Tell me how much pressure at 1/2 pound per min would be needed for surge? Almost ANY would do the trick agreed?

 

[4000GT]

Ummmm wont the motor be seeing vacuum on cruise... all the turbo charged cars I have owned do. Is he running anti-lag?