paul r

Hi,

Many people have used Reliboost on a Tial or Lyndsey WG, but how does it perform on a standard WG? (It has been shimmed to open at 9psi on the bench).

I have chips programmed for 14psi running with the cycling valve. I want to know if fitting the reliaboost and bypassing the cyclng valve will:

a) build the boost sooner

b) hold the boost longer

Paul R

Waterguy

My understanding and results with shimmed stock wastegate, reliaboost and bypassed CV:

a) The shimmed wastegate builds boost sooner, not the Reliaboost. My wastegate is shimmed to open at 6 psi and I got a very noticable improvement from stock.

b) Yes. The CV reduces boost at higher rpm, so bypassing it holds high boost longer. With my K26-8, the boost drops from 17 psi below 5,000 rpm to about 15 psi at redline.

hosrom_951

The reliaboost replaces the cycling valve. That CV is controlled by the KLR which allows it to recirculate the boost while shifting and for boosting level sensing. By having a direct link between the banjo bolt on the intercooler, the reliaboost and striaght to the wastegate, you are eliminating any time needed for the CV to react and holt boost longer.

awilson40

It will probably not hold boost longer, thats more of a function of the WG and turbo.
It will build boost sooner and faster and let you adjust the max boost.
Bypass the stock CV and go with the reliaboost, you'll like it.

Jaak Lepson

Copied this from the 951 e-mail digest. Markus explains what happens with our turbo configurations.

Sage advice!

Jaak Lepson



If you want to prove to yourself that the wastegate will hold all the boost your car can produce, just pinch off the line going to it with a pair of vise grips etc. Be careful! In this configuration you can build in EXCESS of 25 PSI. You WILL blow your engine doing this if you drive it like this.

If your gate can't hold the pressure then it has a cracked valve seat. Common. Needs to rebuilt with a better quality material (which we do here)

Don't blame the wastegate for doing a peak-and-roll off if in the same sentence you say it is the controller that is opening the gate. You are right, the gate is a gate. It is your chip mapping and the cycling valve that is opening the gate. An aftermarket gate will hold more because it will work differently with the factory "rest of the components" because it is NOT matched to the factory system. An aftermarket gate installed in stock configuration does NOT do a better job than that of a properly functioning factory gate. Hate to disagree but a working gate is a working gate. If one isn't working properly, you can't compare it to another that IS working properly. That isn't a fair comparison.

Why is a factory gate, installed backwards not a factory gate? Ever install your tires in reverse rotation to get that last bit of rubber off of them? They are still tires right? You just installed them different but they still fit.

I NEVER said I install a stronger spring! As a matter of fact, when I rebuild gates I DO NOT want to even see the diaphragm units! I have no interest in machining that apart and installing stiffer springs. That would technically NOT be allowed in stock class. The original question WAS about a stock gate. Read the feedback from others on the list that are posting... some running 20 PSI on a STOCK FACTORY gate in RACING application.

Anyhow, always up to personal preference and as always, YMMV.

Second Post.

I never said I JUST replace the valve seat, I said that if the valve seat is
cracked it has to be replaced and I do that here. You can read into that
what you want. I don't divulge how I rebuild the gates... Like I say about
everything, if it were easy, everyone would do it... Yes, other people do
replace the spring (I hesitate to call some 'tuners') and twice as many
again do it without understanding completely how the whole system even
works. Make it harder for the gate to open and you have more boost is the
common logic, so they put in aftermarket gates, change the spring etc.
Actually the proper way to tune anything is to look at WHY things happen and
solve the problem! The gate opens on the 951/2 because of a signal to do so
(assumes all parts are in working order of course). So, if you want more
boost (and all other conditions that are required are met) then you should
be looking at signal conditioning or control instead of feeding the gate the
same signal values and then preventing it from working by overloading it
with a spring etc.


Your explanation on how a gate works is partly true only. The turbo does
NOT run on exhaust pressure primarily. It runs from the latent energy that
is in the exhaust gas, which is in the form of heat! That is why pipes are
double walled, insulated etc and people put blankets on them and ceramic
coating. Keep the heat in, keep the power UP. The amount of pressure only
that would be required to spool a turbo to 40,000 + RPM would require quite
the compressor, and unfortunately your engine just isn't that efficient an
air pump (if it was you would not have a turbo attached to it). Yes,
exhaust pressure does push on the factory valve, but it is primarily the
electronic controls with a line of PRE-INTERCOOLER PRESSURE that opens the
gate by pushing down on the diaphragm. Note that line coming from your
intercooler piping to the Cycling Valve, and then to the gate. Reduce or
control the pressure in this line (LBE, banjo bolt, MBC, broken off match
stick etc) and you have just increased your boost.

Gate rebuilding costs vary depending on what is done and required. Average
is $200.00.


Markus Blaszak
Blaszak Precision Motorsports
www.BlaszakPrecision.com
4835 Holmes Rd.
Inverary, ON, Canada
K0H 1X0
613-353-7012

Danno

"Be careful! In this configuration you can build in EXCESS of 25 PSI. You WILL blow your engine doing this if you drive it like this."

Jaak, you can try this test with a modification. Pinch off the hose to the wastegate, or remove it altogether. Feather the throtttle to get a 15psi max-boost level in the mid-range. Then gradually increase throttle with RPM to keep boost-constant. Even with zero pressure going to the wastegate to open it, you will not get more than 10psi by redline; in many cases less, like 7-8psi.

What this means is that exhaust-pressure on the surface of the valve, will generate more force than what the spring is exerting to clamp the spring closed (calculate using valve-surface area if you want). I can assure you that with the 50psi+ I've measured in the crossover, the stock wastegate, regardless of shimming, will not be able to hold more than 10-11psi at redline.

That's why I went with a replacement spring that's twice as stiff as stock in the GURU rebuilt wastegates. This equates to roughly a 0.7-bar spring if boost is fed directly from the banjo-bolt into the wastegate diaphragm. In this instance, you can get a 12psi flat boost-curve.

BTW- forget about programming boost with chips, way too many people have tried and failed.

GaryK

I'm using a Reliaboost with a standard wastegate (rebuilt by Blaszak), no cycling valve, and a T04E turbo. Ramp-up is fine and there is no problem holding full boost to redline, but I won't run more than 16psi.

Danno

GaryK, even though you're holding your max-boost level just fine, it's because you've got a larger aftermarket turbo. How's the boost build-up BTW? I remember you had complained about slow boost with your previous configuration, but thought it was the altitude.

Anyway, with the stock spring in your wastegate, you're still losing boost due to the creeping wastegate. Just that your big turbo can more than compensate. So you're over-driving the turbo. You're getting 16psi into the manifold, but an additional 5psi is going out the tailpipe. When you ramp up that turbo to 20-22psi, its sweet-spot, you'll find that you'll have a 2-3psi high-RPM boost-drop just like the stock turbo.

GaryK

Hi Danno. Since you asked.... I've changed some things on my car since last year. Back then, with the original wastegate and a K27/6 installed by the p.o., boost would drop from 15psi to 11psi up top. The rebuilt wastegate fixed that problem. Then I pulled the banjo bolt restrictor and cycling valve in favor of the Reliaboost and spool-up improved. Then I replaced the K27/6 with a T04E and the car pulled much stronger and spool-up was actually marginally better as well.

As to what Blaszak actually did to the wastegate, I'm not sure as he won't reveal it, but I can see it is shimmed. I'm sure with a Tial wastegate, an AVC controller, and a 3" downpipe, spool-up would improve, but we're talking what, $1200?

Yes, I was really impressed with the spool-up of your car I drove in Santa Barbara, but it had the a K26/6 on it, right? And, believe me, altitude makes a huge difference in spool-up. I've never had my 951 below 4500ft (and usually drive at 5000-7000ft), but I've taken some modded Audi's from here down to sea level, and the difference was remarkable.

I have no intention of running more than 16psi boost, which at this altitude corresponds to about 19psi at sea level, and is within the efficiency range of the compressor.

But, since you brought the point up, do you really think I'm getting boost creep from the wastegate even though it's been rebuilt/shimmed and the cycling valve has been removed?

Also , I just (hopefully) dealt with another problem, which was probably affecting throttle response, particularly on the track. I finally installed a .01" restrictor in the oil feed to the T04E, since there was a ton of oil blowing through it during track use. So much so, that it was not only making the intercooler less efficient and displacing the air/fuel mix in the cylinders, but it was also backing up the intake towards the MAF! TEC had recommended against installing a restrictor, so I didn't when I installed the T04E last year, but the oil consumption was ridiculous. Haven't had the car back on the track since I put the restrictor in, so we'll see. I really expect the car to perform better exiting corners without the intercooler and cylinders full of oil, and for the oil pressure to stay a bit higher as well.

And yes, a fair amount of oil blew through the old K27/6 as well, so I guess we could discuss blowby, crankcase pressures, etc too!

Anyway, sorry for the long-winded response, but as always with these cars, there are a lot of factors affecting any problem.

Tomas L

The stock spring is really to weak for a modified engine.
This was intentional from the engine designers. In case of problems the KLR is supposed to take down boost to a harmless level, somwhere around 0.4 bar. To do this the wastegate is equipped with what can be considered a 0.4 bar spring from factory.
A wastegates main features should be that it's opening is not influenced by the exhaust pressure and that it should not open before the desired boostlevel is reached, and when it's reached it should open very fast.
The first thing is accomplished be a great boost membrane/exhaust valve area ratio.
The second thing is accomplished by a low rate (soft) spring that is highly compressed to give the correct preload. A big exhaust valve does also help but then a bigger area membrane is needed.

The stock 0.4 bar spring makes the wg sensitive to exhaust pressure. I have not measured but my guess it that the stock wg has an area ratio of around 2-2.5:1. This means that it is, given a spring rated for the used boost pressure, more than twice as sensitve to boost control pressure as it is to exhaust backpressure. But since the spring preload is only half of what it should be to run a stock 0.8 bar boost then the relationship gets much worse. Instead of a 2:1 we now have a 1:1 sensitivity boost/exhaust pressure. This is very noticable when running the stock turbo outside it's efficiency range where the boost drops fast.
There is also the risk that the weak spring start to open before max boost is reached, giving slow boost buildup.

Tomas

Tomas L

My previous post got long and maybe hard to follow.
The simple conlusions is.
- Always run a spring that gets you close to your target boost pressure, only do minor adjustments with your boostcontroller.
- When buying a wastegate, choose one that has large ratio of the boost membrane area to exhaust valve area (the wg exhaust valve, not the engines).

Tomas

Danno

"But, since you brought the point up, do you really think I'm getting boost creep from the wastegate even though it's been rebuilt/shimmed and the cycling valve has been removed?

No problems with your configuration. Since you're only running 16psi, the extra boost that's lost in the upper-RPMs won't make a difference.

"- Always run a spring that gets you close to your target boost pressure, only do minor adjustments with your boostcontroller."

Exactly! Even at double the stock spring-rate, at about 0.7-bar the GURU wastegate could use one that's about 3x stiffer than stock. This will be roughly 16psi when controlled directly from the banjo-bolt. Then a boost-controller can be used to nudge it up a tiny bit to 18psi. I suspect this configuration will allow a K26/6 to hold flat 18psi boost to redline with a mechanical controller like the K26/8 TurboS can do now. Although with an electronic controller, you can get flat 18psi out of a K26/6 as well, but it'll be over-revving compared doing it with a stiffer wastegate spring.