Just adding my own experience with my efr8374ewg. Im getting that flutter thing a fair bit too. Part throttle, boost/vacuum threshold with some engine rpm on board.
Have a 50mm turbosmart raceport? Bov near the throttle body refferenced to the uim, the efr recirc valve dissabled by way of being looped back to compressor housing.

Im not worried about it. Iv been meaning to hook the efr bov up and dusable the turbosmart, and maybe hook both up together to see which way works better but like i say im not even worried as it doesnt seem to affect drivability.

I see.. No my actual ebc unit is not sourced off the turbo but rather post-tb. I dont have any sources pre-tb, ill have to mod something up or T in the solenoid line.

Cool
Just T into the solenoid line to try it out and do something more permanent (closer to the throttle) if you are happy with the result .

I am confused. Not on how to hook everything up as described, but as to how this will solve the issue?


The turbo provides boost, the solenoid gets its pressure source from the turbo. The boost controller, the signal to open and close the wastegate to control boost pressure, is tapped into where the engine would see pressure to most accurately get the pressure you want.


Now if you tap into pre-throttle body you still get pressure but there will be slightly more pressure drop (not much) as boost travels down the UIM and LIM post throttle body and after your source.


But the issue we are experiencing is at part boost pressure while modulating the throttle which will have the throttle body opening and closing, possibly completely, how would controlling boost pre-throttle help this situation? The wastegate is closed the entire time.


Yes, the turbo still does this with the boost controller open (off) and running just off the spring pressure.

if you could jack the wastegate open all the way to test out and see if that solves the problem it would tell you if the EBC can be plumbed differently so also solve the problem... or it would tell you there is something else going on with the flow of the turbo vs the engine....

stock ports we made 340 on 11 psi pump gas and 365 on e85 after 16 psi was going over 400s

Ok not bad, what about the exhaust system and type of ECU, ignition? Overall the first dyno before it made 330 on 10 psi. I am trying to compare apples to apples if it matters.

Tuning4life

I am confused. Not on how to hook everything up as described, but as to how this will solve the issue?


The turbo provides boost, the solenoid gets its pressure source from the turbo. The boost controller, the signal to open and close the wastegate to control boost pressure, is tapped into where the engine would see pressure to most accurately get the pressure you want.


Now if you tap into pre-throttle body you still get pressure but there will be slightly more pressure drop (not much) as boost travels down the UIM and LIM post throttle body and after your source.

Well, I guess that would come down to how good the filtering is on the EBC and which post TB nipple you used.

I had my MAP sensor tapped off the nipples on the FD UIM primary runners at first and I will tell you I saw some interesting readings on the data logs and wonky 2ndary injector staging (stuttering).

The Dynamic Effect Intake pressure pulses from the ports opening/closing were 2-3psi spikes in the map signal.

I switched the MAP line to the proper location just behind the throttle body and had a cleaner signal and no more problems with stuttering when staging the 2ndary injectors.

Boost reference before the TB is definitely going to be the cleanest signal (ofc lacks vacuum signal so not an option for MAP signal).

That's the thing .... the WG isn't closed the entire time in that scenario . Plumb a boost gauge between the turbo and throttle and see what boost pressure you have at partial throttle as compared to post throttle . You may see up to 20psi pre throttle when post throttle is at zero or even in vacuum.

To put my previous explanations another way : with an EBC you are trying to control the turbo . Plumbing it into the manifold only controls the turbo accurately when the throttle is open ! When the throttle is closed the information it gets from the manifold is not relevant to what the turbo is actually doing. IE building up quite a bit of boost pre throttle.

If that is the case ..... doing what i suggested probably wont achieve anything.
I would still give it a go though , you may see an improvement.

Let's say this is actually what is happening....wouldn't the BOV be open in this scenario to relieve the pressure? the BOV is connected to the post throttle body position experiencing vacuum.

Depends on how much vacuum and how much tension is on the spring . I like to set the bov up such that it opens at idle which does help avoid too much boost build up .
But in the situation you are describing manifold pressure is likely to be hovering around zero and BOV will definitely be closed.


Someone mentioned the synchronic BOV earlier ..... that could well solve your problem as they operate in a different way to other BOVs and it should help prevent that boost buildup pre throttle.

Remember that I'm not just spouting out theory here . This is a problem i also had and was able to completely solve very easily .
All it took for me was swapping one hose over . As your power fc also controls the tune using the same boost source , maybe not so easy............

haltech stock coils , full 3 inch exhaust

A good BOV works indeed with differential pressure between upstream throttle and downstream throttle. lets say the threshold is 2 psi there cannot be more than 2psi more pressure upstream throttle than in the manifold. whether there is vacuum in the manifold or no does no make any difference.

As for solving this on the turbine side. therefore you need a really weak spring, of a dual port wastegate with 4 port solenoid with weak spring. With a normal actuator with lets say a 15-20 psi spring there will still be surge conditions possible because of lack of pressure to open the gate.

Just trying to make sense of all this.


I completely can understand that the spring pressure on the BOV is too strong. It therefore takes a few PSI or possibly 5PSI pressure to relieve pressure. As you boost partially the wastegate is closed and the throttle closes and anything under 5PSI has no where to go but to back up to the turbo.


solution: less spring in BOV


Wastegate controls boost pressure. if the threshold boost is 15PSI, perhaps the computer or EBC will open it slightly before but its trying to maintain a 15PSI boost pressure by modulating the exhaust pressure/flow with the watsegate. Obviously the spring pressure of the wastegate controller is less than 15PSI, perhaps it is 10PSI.


Anything less then 10PSI does not effect the wastegate at all. If the problem is backed up pressure in the intecooler track, then how the heck does the wastegate have anything to do with the intercooler track and preventing/relieving this pressure build up?


if the pressure is 3PSI and is less than 5PSI threshold for BOV...solved.


I would be willing to try a softer spring if someone knows where to find one. I am using the BW BOV on the face of the turbo, I haven't been able to find one. I do see they have stiffer ones.

As you may already know Turbosmart makes BOVS and wastegates for the EFRs, Singles and Twin Ports but it does bother me that they do not provide a spec sheet on their website, they just claim that it's capable of controlling boost over 30 psi

Pretty sure that most BOVs are way more than 2 psi, with the exception of the Synchronic . Which is why they are such great BOVs .


Agreed . Although it might come as a huge shock to a lot of people how much pressure is actually built up under certain conditions .
I run a 4 port solenoid with a 5psi spring in the WG and have no trouble boosting to 18psi plus ...FWIW.

It's all to do with how far you have to open the throttle to get more power mid corner. If the wastegate stays closed , you need less throttle and it's more controllable . If it's opening and closing ........... control is lost.
Just thought of something that might help clarify : At partial throttle , even with the wastegate OPEN , there can still be significant pressure pre throttle. There is very low flow though ( and no power ) so you open the throttle a little more .......... until ..............the wastegate suddenly closes and BAM........... say hello to the curb !

Put that boost gauge pre throttle , check pressure under the conditions you experience surge . From there you will know what you are dealing with .

Very constructive convo , will definitely have to try that .

we have someone local running an EFR 8374 with the turbosmart wastegate actuator, I believe its a 4port, so we can see if that makes any improvement.


if so I will report back and change my over, if not, oh well. He also has the metal cover from full race for the BOV, but I suspect that won't change anything.

The twin port actuator paired with a 4-port boost control solenoid allow you to run a very low base spring pressure (basically as low as itll go without creeping) and run boost as high as you like. On a dual-purpose car or a car that uses flex-fuel this can be a nice feature.

I have found that setup great for tuning as well . I can very easily tune at any boost pressure from spring pressure on up.
Good for when you drop the car off to get work done on it as well .... So when the hairy arsed apprentice takes it for a strop he can't get full boost.

Keep us updated

I see you've migrated over to 7club Brett. good to see you :)

i was thinking the same thing.. like,, welcome.. to out side the box.. we do things differently over here.. lol.

Any feedback on the surge issue ?