I just installed an LBE and APE Stage II chips- car runs MUCH better then before - my 2-3k light sputter is now gone and the boost no longer rolls off like before. Car is transformed. However, I dunno what the correct setting on the LBE was.

I have read many past threads on the archive and on the LR site - I tried to eyeball what I assume was 10psi on the LR web page - 5 threads exposed or so. Just paranoid I will grenade the motor with excess boost. Boost pegs just a c-hair past the 2bar mark on the stock gauge (no aftermarket one yet).

Thanks

Eugene

 

Well, the stock wastegate spring's condition varies widely across different cars, so you can't make one setting on the LBE as universal (it will produce different boosts on different cars at the same setting). I in your case, your spring is on the strong side, so I would turn DOWN the boost to be on the safe side.

 

Danno,

I thought the Wastegate was dictated to by the LBE? Air has to go via the LBE before getting to the wastegate, no? Therefore, if you raise the boost via the LBE, the wastegate will not be able to react since the pressure will be kept back by the LBE until desired boost reached(?) Or, am I completely wrong, as has often been the case ...

I agree with your suggestion about turning it down a bit though (mine pegs at 2bar in 3rd and 4th)

[quote]Originally posted by Danno:
<strong>Well, the stock wastegate spring's condition varies widely across different cars, so you can't make one setting on the LBE as universal (it will produce different boosts on different cars at the same setting). I in your case, your spring is on the strong side, so I would turn DOWN the boost to be on the safe side.</strong><hr></blockquote>

 

Thanks guys. Will try to lessen some of the boost. Sure feels good though! I need to T in a good aftermarket gauge soon.

Gary, my car is the same color combo as yours - Graphit and maroon interior. What kind of rims are on your car in the Avatar?

Eugene

 

[quote]Originally posted by eclou:
<strong>Gary, my car is the same color combo as yours - Graphit and maroon interior. What kind of rims are on your car in the Avatar?

Eugene</strong><hr></blockquote>

Eugene, in the avatar, it's a general picture, not my car! However, I have 16" phone dials with S02 - Pole Postitions (225/50 & 245/45's).

I'm not sure maroon would describe my interior but yes, it's darker than rosso red

You can see a couple of pictures at members.rennlist.com/gary ("Porsche" is on the rotating wheel at the top)although the interior isn't really obvious.

Are you running phone dials also?

 

Eugene, I recognize you from the bimmer boards. Good to see that you are running the same setup as me (APE Stage II and LBE).

I am only hitting 12-13psi according to my aftermarket gauge, should I increase the boost on the LBE?

 

if you screw it so that the distance between the two peices is equal to 3 pennies, that is 10psi

 

V Shah,
from what I have soaked in from here, up to 14-15 psi is pretty safe. I don't want to run anymore. I have a 16yr old 140k mile head gasket.

Luke,
I read your 3 pennie thing before but if that was the distance between the lock nut and the base then that would be way more spring pressure than what I have got now. The LR photo ad shows 5 threads exposed which is way more than 3 pennies (mine is not threaded all the way to the base). I will take a dig pic of mine and post it soon.

Eugene

 

its 4 pennies then


Ilost my spring and poppet. Mike @ LR sent me new ones with a pen Drawing explaining the 4 pennies is 10lbs (for a reference point)

 

"I thought the Wastegate was dictated to by the LBE? Air has to go via the LBE before getting to the wastegate, no? Therefore, if you raise the boost via the LBE, the wastegate will not be able to react since the pressure will be kept back by the LBE until desired boost reached(?)"

Yes, that's WHAT it does qualitatively and in principle. But we have quantify that with actual operating pressures (numbers) to see HOW and WHEN things are occuring.

The LBE and wastegate are not digital devices, in that they're not all ON or all OFF, but rather are analog devices operating with variations. The amont of pressure applied to wastegate diapram determines how much it opens. And this pressure actually varies between different stock wastegates depending upon the condition of the spring. I've seen variations from 3-8psi as being the minimum pressure to start opening the wastegate.

Ok, onward to the LBE, which is a check-valve type of controller (similar to the earlier Hallman and Anderson boost-controller). It basically consists of a spring-loaded ball or plate that covers the incoming port with an adjustment screw behind the spring.

In order to push open the check-valve, you have to have a minimum amount of pressure coming down the inlet port. Now we know that the LBE claims to be shipped set to '10psi', but as we've seen most people have been getting around 15psi on their boost gauges. Why? That's because this '10psi' is the pressure that starts to open the check-valve. Since it barely opens the valve, little pressure makes it to the wastegate and no boost is lost. The LBE is not a digital device and the amount of air & pressure that gets past it, is based upon the amount of pressure present at the inlet port. It just may be the case that it doesn't START to open until 10psi, but only less actually makes it to the wastegate.

Let's say a particular wastegate opens at an average of 5.5psi, the pressure that actually makes it past the LBE may only reach 5.5psi when the turbo has created 10psi of boost (because the spring is always pushing back trying to close). At this point, the pressure opens the wastegate and boost drops. As boost drops (to say 9.5psi), it allows the spring tension to overcome the pressure at the inlet and the check-valve closes. Then the wastegate closes and the boost builds again (to 10psi). Which then creates enough pressure (5.5psi) past the LBE to open the wastegate and the cycle repeats itself.

In effect, it is a mechanical servo-feedback loop. The frequency of this cycle, I have no idea as it would require data-logging equipment to find out. But I surmise it happens several times per second quickly enough that the boost gauge appears to be hovering at a steady boost level.

Since the LBEs are new, we can assume that the pressure-differential between the inlet and outlet ports is a fixed ratio, thus we can ignore that to remove one variable. Which leaves the other variable of the wastegate's opening pressure. If we have two stock wastegates, one with a strong spring that opens at 8psi and one with weaker spring that opens at 3psi, then how the LBE affects them (and the resultant boost) will be different. Let's say the LBE starts to open at 10psi and allows 5.5psi to reach the wastegate. If we use the strong wastegate that opens at 8psi, it will remain closed. Only when turbo boost pressure reaches... say 16psi does 8psi make it past the LBE to open the wastegate. However if we use the weak 3psi wastegate, then as soon as turbo boost reaches 10psi and 5.5psi makes it to the wastegate, it'll open and dump boost.

So with two stock wastegates in different stages of wear, we'll see boost pressures of 10psi or 16psi from the same LBE setting.

EDIT 2002-10-03: This is almost right, I've got some of the numbers off. See this updated disccusion: <a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=010253" target="_blank">Topic: LBE intalled, getting weird readings</a>

 

I actually bought My LRBE with intentions to use it ONLY to see if my wastegate was functioning. Since my Diaphragm had been puctured, the LRBE does absolutely nothing. If the LRBE could dictate wastegate pressure, it could also replace it. But I know from personal expirience that the LRBE depends on the condition of the wastegate. That is why I reccommend A LR or another wastegate upgrade.

 

Even with chips and a banjo bolt jet that APE told me I should see 15psi with, I would see only 12psi. I replaced the banjo bolt with a stock one and installed a LBE. At its preset settting (advertised as 10psi), I saw only about 11psi boost. Adjusting the LBE to its maximum setting, I now see 14psi, but it holds to redline. Spool-up is improved.
So, I guess my wastegate spring is weak or the valve seat is cracked or some other failure. But I do live at 6000ft, so 14psi might turn out to be 17psi at sea level
Rebuilding the stock wastegate is starting to sound like a cost-effective alternative to an aftermarket wastegate and electronic controller (no, I don't really trust the schrapnelknobben, er manual boost controller.)
Gary
'89 951

 

Gary, have you tried shimming your wastegate? It's a simple 30-minute procedure and will increase the spring-preload a bit.

 

[quote]Originally posted by Danno:
<strong>Gary, have you tried shimming your wastegate? It's a simple 30-minute procedure and will increase the spring-preload a bit.</strong><hr></blockquote>

Danno,

Thanks (as always) for the detailed explanation earlier in the thread I understand what you say about the relationship between the LBE and the Wastegate. However, I still may have missed something (sorry for my lack of mechanical knowledge!) ... If you adjust the LBE to the desired boost (my boost gauge shows 1 bar or 15psi thereabouts and it will boost higher), then what difference does it make whether your wastegate opens at 3psi or 8 psi? In fact in theory, with an LBE, you don't need a a wastegate(?) since the LBE regulates what get's dumped. The wastegate just get's in the way in fact. In the same way, some people on this list run with a wastegate sprung to the required boost and do away with the cycling valve and any other limiting "valves" in favour of the wastegate.

Apologies for the questions but since I'm currently "shopping" for the next group of mods and a wastegate was a potential one (the turbo's currently at the top of the list with the MAF second), I really need to understand this to avoid "wasting" money (or, at least, putting it in the wrong mod).

 

So shimming the wastegate is really that simple? I assume you don't even have to remove it from the car? From what I've read, the most common failures on the stock wastegates are weak spring and cracked valve seat.
I also heard a rumor the stock wastegate will hold over 20psi in like-new condition.
Gary
'89 951