Why am i overboosting

[zeppelin101]

So it holds 1 bar + ok but struggles at low boost? Wastegaste can't be taking enough air away from the turbine wheel for some reason if there are no leaks. It's not much more complex than that. It definitely has full stroke on all the occasions you've stripped it?

I'd check all your boost lines carefully. With that low a boost requirement, it won't need much help to not open enough and up increase boost pressure. By my calcs, the turbine is still sub 1.7 PR so it won't take much in terms of a pressure increase pre turbine to increase wheel speed.

[fikemoo]

Well as said in my previous post annoyingly I don't have any data on when it was holding exactly 1bar. Ie if I lowered the boost if it would still over shoot. The reason for the lower spring was just testing purposes really to see if it would hold lower boost pressure such as 0.6 bar and to see if the lower spring gave it a bit more control as the problem as stated is not enough gas is getting dumped for whatever reason. At present no matter if I run it through the avcr or just on spring value the boost will just creep and creep and creep until red line. I did some testing today and found some nice results. I plumbed a manual gauge into my boost reference line and disconnected the avcr so I was running purely on spring pressure.

So I have two gauges the one mentioned above and the avcr unit itself. Right so went for a drive. Nailed it... manual gauge sees bang on 0.4 bar and does not move but this is before the avcr sees anything. No boost nada. Once the avcr sees boost so say 0.2 bar 0.3 bar the manual gauge is still sitting strong on 0.4 bar. Once boost then decides it's going to keep going and going so avcr is reading 0.64 bar the manual gauge is now seeing 0.5 bar. This seems strange to me. Care for a second opinion?

[zeppelin101]

That depends on whether the manual gauge is accurate or not to compare to. You could test it with some compressed air from a reliable source and see what it reads versus what the compressor says and then do the same with the AVCR. If one says the same and the other moves or does something unexpected then that may be part of the answer.

The problem with lots of measurements on different equipment is that you're into the realm of equipment error against what is actually happening unless you validate both against a constant (if that makes sense?).

[ANDY black s13]

The two gauges plumbed into the same boost source? if they are then something is off just from the readings being different
got to admit it has had me thinking for ages why its doing what it is
is the take off for the WG central to the manifold collector or is it slightly off-set?
just thinking if not central on a 6 primaries into one collector set up you could have 1 or 2 primary runners bleeding past the gate?
so they are still driving the turbo even thought the gate is open? and causing the spiky over boost b@ll bags senario you have
I'm sure its a vent exhaust problem (sort of) but nothing seems wrong with the set up really (you certainly haven't skimped on cheap parts)
aside from my recent collector/WG position idea
took me ages to make this post btw as keep going back to the pics

[fikemoo]

If both gauges are plumbed to the same source/area they read exactly the same as this is what I had done previously. These result were with the avcr where it always has been on the intake manifold. And the manual gauge was teed in to the pressure line from the compressor housing. The wastegates position is slap bang in the middle of the collector. And hahahhaha Andy thanks again for the kind words. As you said I haven't skimped on the car. And I'm a bit ocd lol

[zeppelin101]

Hmmm.

If you are measuring pressure in the compressor housing, the pressure should not be rock solid, it will increase with increasing airflow (to overcome the pressure drop that the intercooler has) in order for the manifold pressure to be consistent.

So something not right there. It should be the other way round. You definitely had them plugged in where you thought you did right?

[fikemoo]

Yeah they were deffo plugged in where stated hahahaha I did double check to make sure I wasn't being a noob. And the compressor housing pressure did climb but below what the avcr stated.

[ANDY black s13]

OCD and car builds means great awesome things in my book , nothing wrong with getting things just right how you want them
like I have redone some simple brackets over 4/5 times as I rethink its use and redesign it lighter and/or stiffer
my weight reduction OCD alone is bad enough, nearly done the dashboard bulkhead area,still lots to do though

back on topic of the crazy boost senario, I have run out of ideas for now
and yep did think the collector and WG take off was central,it was hard to check from the pics that was all

we are missing some thing but not sure were,,,

[fikemoo]

The words air leak have popped up quite a few times and as far as the lines go that run from the wastegate to the pressure source and to the avcr. Have all been checked. say for example intercooler pipework has not as I was told that my pressure source coming from the compressor housing only the line that feeds the wastegate could effect it. But I'm doubting this statement. All the fittings on the wastegate are tight also but apart from being tight they could be leaking I suppose. Who knows. All the vac line nipple on the greddy intake I removed cleaned and ptfe taped them up

[fikemoo]

Right so doing some testing this morning. I've rigged up a tyre pressure pump to replace the pressure in which the turbo would produce. Left the lines as is. So its pressure (in this case it's pump) to a tee. One goes to bottom of wastegate l. Other goes to gauge. Top ports on wastegate are open. I turn pump on and you can hear and see through the top port that the valve is fully open. It's hitting the top of the wastegate. There's no hisses or anything coming from the lines as i expected there is no leaks in them as they are all new. The gauge read 1.2bar so if they were going to leak they would have

[shredjester]

I don't know if anyone else has experience this problem but when my car was over boosting from 10psi to like 17/18psi i found that it was my clutch was slipping every now and again it wasn't happening all the time but if I put my foot down when the clutch slipped slightly it over boosted.. I ended up changing the exedy organic to a act hd organic which is rated to like 364 ft lb of torque if I remember or somewhere around that figure.. When it was all installed I haven't had any cases of over boosting since touch wood... I ones fikemoo to tell him my situation I had but just wondered of anyone else has hear of it or had it happen to them


Sent from my iPhone using Tapatalk

[fikemoo]

Right a bit of an update nothing done as of yet but my mapper is certain that the way in which my car is tuned is the reason for it not being able to hold lower boost. Even with wastegate fully open. The timing and fuel. The turbo just powers on. So the map is going to be made a little bit more tame and ill let you know how it goes