I put up this thread about a year ago and since I have gotten a new bdc hbp and tune up to about 10psi. I still have the same basic problem as before. The boost starts to creep up around 6-6.5krpms. It doesn't go up as fast or as much as before but it still does.

The wastegate is plumbed off of the big vacum/boost nipple on the primary runners on the uim. Will plumbing it off the turbo fix it or help at all?

I put some air pressure off my compressor to the side port on the wastegate and it opened a good bit. It is kinda hard to tell how much pressure it takes to open it but its around 10-15 psi. I could almost get my finger under the valve, it seemed to open all the way.

A little background, same turbo with 3" exhaust and hks standard wastegate held boost fine. Once I went to 4" exhaust I got horrrible boost creep. New motor/tune with 50mm wastegate and it helped out some but didnt fix it.

Any opinions and thoughts are greatly appreciated.

 

run dual wastegates 4" exhaust is massive... no resistance on the turbo so pretty much you need more than 50mm

 

how much hp should you me running with that set up man

 

Yea so new manifold then huh,lol.

Do you think that a turbo with a q-trim or other higher flowing exhaust wheel would also help/take care or it?

 

Your current configuration will cause an initial spike in the boost.
Move the vacuum line to the turbo compressor or closer to it - it should change the boost ramp.


-Ted

 

It doesnt really spike though, it goes up to 10 when I get on it and stays there till about 6-6.5krpms. I am planning on putting right after the turbo. Im just not sure how much it will help.

 

I personally feel it will near solve your issues. The responce will be more initial and accurate. Are you just on spring pressure or using a boost controller? If using a boost controller, which model? And what spring do you have in your wastegate?

Ty

 

your problem is either your boost controller or the wastegate placement on the manifold.

 

All this is with the boost controller off. I am using the apexi avcr. I even took the solenoid out off the loop and ran a line straight to the side nipple. I am pretty sure its the 10.15 psi spring.

 

So do you think the HKS cast manifold is to blame?

 

well if you run the vacuum straight to the side of the wastegate and elimate the boost controller and it still creeps, you pretty much figured out where the problem lies.

A well designed manifold will direct flow into wastegate.

 

I think the HKS manifolds are probably designed fine. I haven't heard of anyone having problems with boost control using them. I actually had the same issue with my car using a 50mm wastegate. I tried all sorts of different combos, as it sounds like you have. If the boost is creeping up late in the rpms, its obvious that as your car is putting more and more exhaust out, the gate just can't keep up. So its either the manifold is designed badly or the gate isn't big enough. I'm not 100% on this but you may be able to just change the flange on the manifold to mate with a 60mm instead of just ditching the whole thing.

 

I have had a similiar experience. HKS manifold and hks 50mm. Although I need to dial in my Profec B a bit more. I had horrible creep with the 40mm version. I think it's the manifold, but at the same time others haven't had any problems.

 

what are you guys' setups?

 

Alright I got one of those quicktap things and tapped the silicone hose right above the turbo. I got the wastegate running off of it now and it pretty much does the same thing but at 1-2 psi lower overall.

So looks more like manifold design then huh?

 

you could just set the thing to run like 12psi....

 

Thats what I wanted to do but the tuner wants it to hold steady boost before he countinues.

 

It could be the manifold design...you think it was designed for flow to the wastegate at 12psi?

Keep in mind that the LOWER your target for boost the LARGER your wastegate has to be.

The HIGHER your boost target, the size of the wastegate becomes LESS of an issue.

I'll would think that you have LESS of a creep issue at 14psi, than 10psi.

 

Not necessarily...

You're making a very generalized statement trying to describe the dynamics of what goes on with the turbo operation.

While it does make sense intuitively, you're ignoring a whole bunch of stuff that affects boost and wastegate orifice size...


-Ted

 

Ted,

Is anything in there untrue? Granted it is generalized, but can you refute it?

Regards,
Tony

 

Riley,

In response to your PM...

Enzo mentioned it, your wastegate placement and manifold design greatly affect how your wastegate performs.

While Ted questioned it (but did not refute), I still support as true that the lower the pressure you try to hold to the more important the effectiveness of the design of the wastegate system (read: placement, orifice, boost reference source, line size, etc.). It is also true that lower target boost requires more flow through the wastegate for optimial control and hence wastegate orifice size becomes important.

Since you cannot control (cast HKS manifold?) the size or the placement of the wastegate in that manifold, I would conclude that for the boost target (12psi?) you cannot control boost effectively with that system (without a spike).

Before junking the manifold design, I would suggest trying the same test at 14 or 15psi IF YOU ARE SAFE FOR THAT BOOST LEVEL. (Safe means good solid ignition map that isn't too advanced, good trailing spark strategy, solid ignition, good fuel supply and safe and actively monitored AFR. Try at your own risk.)

The premise here is that if your target boost is higher than 12psi, and your system is better suited to control boost without spiking closer to your target boost (assumption that the target is higher boost), then you may be okay for solid boost control at your target boost. Based on the idea that the higher your boost target the smaller (or in this case I will say the design limitations of your system) will contribute to spiking.

You shouldn't have to boost much higher to see a change in test results or behavior.

 

I have the HKS cast, and an E-Bay 50mm WG, I have no problem holding 14 psi to 8500rpm. I have a 3.5" DP, and a 3" exhaust. Bosst controller is an AVCR. What EBC are you running? The wrong settings on any decent EVC will cause overshoot, and a good EBC like the Blitz, HKS, or Apexi will use feedback speed in combination with a boost threshold to avoid overshoot without giving up spool. I may have started my tune as low as 12psi, I cannot remember, perhaps BDC can chime in with my Datalogs. Turbo is a PT67 .81 P trim, I also agree with ASLEEP, and have proven it in practice. Has anyone measured their HKS wastegate? a "40mm" HKS gate only measure 32mm at the outlet, the Ebay is like 53mm. For those wondering, I ran the EBay WG for a full season of roadracing with no problems, boosting 20 psi for nearly 20 minutes at a time. Carl

 

I've experience this problem on a customer's car. He had an hks style log manifold w/ a 40mm gate, car would spike in the midrange ever so often. He changed to a manifold that I make, using same gate/turbo etc fixed the problem. Now that may not be your problem, but its food for thought.

 

I have pretty much the same setup as you but with 4" exhaust. Same manifold, wastegate, boost controller, and the turbos are close.

I was told that about 13 psi is the max boost (pump gas) i can run by my tuner (BDC). Reason being the turbo (t04r .96 p trim) and half bridge port combination puts alot of stress on the motor.

 

my assumption is that the manifold causes too much back pressure and the wg can't evacuate all the exhaust. the half bridge is generating too much exhaust flow and the manifold can't feed all of it efficiently through the turbo turbine. i think your wg is already fully opened but it still can't get rid of all the exhaust that's backing up in the manifold.