EBC - Can you alter boost levels at different RPM's?

[Cubes]

Turbo-Tits,

I see it like this...

If a wastegate is too small it cannot bypass enough exhaust gas which causes the turbo to spin harder and produce MORE boost and airflow. This is known as Boost creep and is common on backyard t3/4 jobs.

IF on the other hand the motor is consuming more air than the turbo can efficiently provide it will cause a boost drop as at that particular boost level the turbo will run deep in to the choke zone of the compressor map, the air will also become heated some what, if severe enough it can cause a power drop. This is due to the requirement to pull out ignition timing to stop detonation occuring.

Superheated air = very bad for power.

BUT.. similiar to the RB20t turbo which also runs in to choke even on the rb20t you can push it just that little more and get a little more out of it. I picked up a measly 12rwkw going from 12.5psi (where boost would drop to) to 15psi. 2psi for 12rwkw is obviously not very efficient.

Robo, You really need to get it on the dyno and see what power it is making.

If it is up around the 220-230rwkw the you know you cannot run any more boost as the turbo is running out of airflow.

You can try to push it that little bit more and scrape another few kw's.

[Robo's]

Yeah we are making around 220-230rwkw at the moment. I just wanted to try and push it further and get less boost drop.

[Turbo Tits]

hi cubes,

hmmm, i understand where you are coming from, and the way you explained it makes perfect sense on paper, but in practice with THIS setup, it doesnt seem to work that way.

we are talking about a real-life example, and the results are on the table for all to see, not just with robo's car, mine as well, identical results. no matter how much sense your explanation makes, its not happening. if the turbo was capable of sustaining 17psi, it would have.

ive already given the explanation told to me by 2 different tuners how know what they are talking about.

the pieces fit, who am i to argue?

maybe someone with more knowledge could fill in some blanks for us?

surely, every turbine and compressor are designed to operate within certain parameters, which affects things like blade pitch, angle etc. what happens when those parameters the turbo was designed to best operate in are exceeded?

my brain hurts, good night

[Cubes]

You can still squeeze a little more out.

As I said in a previous post. There is a limit as to how much you can push the turbo before it begins superheating the air in turn loosing power.

I have no doubt you could get the turbo running 17psi, the question is, will it make more power at 17psi or 12psi?

The air may be superheated which requires you to remove a lot of ignition timing.

This looses power. Chances are you will be better off running less boost with more ignition timing and make more power.

There is a happy medium, push the turbo and find out where it is.

Thats if you want to push the turbo to its extreme limits which may reduce reliability.

My main point was the EBC has a lot to do with boost control.

There are a lot of cheaper crappy EBC's available that don't give you full control over your boost.

If you do a little search regarding Grepins 2835ProS you will see he has ran in to this issue. Jam the wastegate shut (which is what a decent ebc will basically do) and it made more power.

Turbo Tits.. .Who are these Tuners?

Going back 2.5years Tim Possingham was the one who told me to get a decent ebc that will learn boost curves and adjust duty cycle to suit in order for my boost to hold in the higher RPM's.

[Turbo Tits]

hey cubes,

first off, simon from morpowa, and bill from ATS.

secondly, we've tried a turbosmart E-boost and Blitz dual-SBC specR, no cheap parts.

mate, a 2835proS, which we currently have on the car is huge in comparison to a 2530! they simply cannot be compared. the 2530 is barely much bigger than the standard turbo.

your theory is viable if the turbo if big enough, in comparison with the engine's capacity, to provide enough volume at high revs, but the 2530 is not big enough.

try dialing 17psi into a standard turbo and see if it holds at the top end, that is if the turbine doesnt fly off before then.

dude, im not a bullshit artist, i keep to myself on this forum unless i truely believe, and have experience from first hand knowledge, that i can help someone out. this is one of those cases. Im trying to save this dude all the trouble and money my brother and i spent on this car.

Tim is right, but not with every turbo application, hes assuming youve got a well matched turbo. take it to the extremes: take the standard turbo from a CA18DET and slap it on a RB30DET, do you really think its going to stay in its efficiency and be able to sustain any decent boost level at the top end, no matter how magical the EBC is, it cant fight the physical limitations of the turbo?

we have all heard of turbos "running out of puff", this is exactly that.

peace and many flowers for you

[Cubes]

Turbo-Tits,

Peace to you too.. A discussion is a good thing.

BUT.. haha

Boost drop in the higher rpm's is a very common problem when pushing a turbo to the limit.

There are a few well known fix's that help reduce the boost drop and make a little more power.

1. Use a wastegate actuator to suit the boost level you are after.

2. A better EBC that uses a learn mode, not the usual valve duty cycle % of max boost number (hence the Turbosmart E-Boost & Blitz SBC SpecR).

Sure they are not cheap but they simply do not have the feature of 'intelligent duty cycle adjustment', the AVCR & Blitz SBC-iD do.

I have no doubt if you hook up a Blitz SBC-iD or AVCR run it in boost learning auto mode Robo wil be able to hold more boost.

Sure it may push the turbo way out of effiency and superheat the air causing a loss in power but this really depends on how far it is pushed, I have no doubt you will be able to squeeze another 15rwkw out of the turbo.

Have a look around which ebc's really do have an auto learn feature.. Not many.

The fact is it works Turbo-Tits... A self learn ebc does allow you to pull a few more psi out of the turbo.

I've seen an older (unsure of the model) HKS boost controller that drops boost in the higher rpms, as did the bleeder and as did the Blitz SBC-iD when running in manual mode (which is exactly the way the Turbosmart & Blitz SpecR works).

I threw the Blitz SBC-iD in to automode, had it learn the boost curve and there we have it.. 15.1psi on the stock rb20det turbo at 7200rpm.

I later threw a VG30DET turbo on the RB20DET which had exactly the same problems when running a bleeder or the Blitz in manual mode. Boost drop to roughly 1.5psi over the wasteagates stock pressure.

Without any boost control my rb20det actuator held 10.9psi, manual mode ebc & bleeders could only hold an extra 1.5psi whicb raised boost to ~12.5psi.

EDIT: I've done a little research on the ebc's.

HKS, Turbosmart all the Blitz apart from the SBC-iD use the conventional valve duty cycle percent settings.

Which is no good if you have boost dropping in the higher rpm's and want just that little more dyno queen rwkw's out of your turbo.

This leaves only the AVCR, Blitz SBC-iD and Greedy Profec E-O1 that have the auto intelligent duty cycle feature.

Maybe this is why Tim travels the world tuning.

He was the one who told me to only get an EBC that has an auto feature which is able to play with the actuators pressure.

[Clint32]

so whats the go for a external gate then joel?

[Cubes]

From what I can gather you select the wastegate size for the hp and boost you want to run.

I.e a lower boost will require a larger wastegate where as higher boost will require a smaller wastegate.

I remember Steve ran a smallish wastegate and had no issues holding 22psi or there abouts with the PowerFC's boost controller.

Select a ext. wastegate that is too small and you will get boost creep where as the rev's rise boost also keeps rising.

You know this Clint?!

[Cubes]

http://www.gnttype.org/techarea/turbo/turboflow.html

There are two different sets of curves in the graph; efficiency curves and rpm curves. The area where there are lines drawn is the operating envelope. It is best to operate the compressor within its envelope. It will still run if you go to the right of the envelope, just not well.

[Turbo Tits]

hi again cubes,

it all sounds very impressive.

the results are there for robo to make up his own mind whether to pursue this problem or not.

i guess we will have to wait until somone actually solves the problem in the real world, not in a forum.

[Clint32]

Joel i meant what boost controller do i buy, may be a little small on the gate as not running the boost i was expecting too, so need a controller to get it set right

[Cubes]

hi again cubes,

it all sounds very impressive.

the results are there for robo to make up his own mind whether to pursue this problem or not.

i guess we will have to wait until somone actually solves the problem in the real world, not in a forum.

Thats the thing.. It has been solved in the real world, just not yours.

That being said you can only lean on it so much before failure, be it the turbo or motor due to superheated air causing detonation.

Pull the boost feed off the actuator and my bet is the turbo will make much more boost at 7000rpm than 12psi.

This is really what a turbo running out of puff means.

The turbo is pushing air that is heated so much (to the right of the ideal envelope) that there are no performance gains.

[Cubes]

Joel i meant what boost controller do i buy, may be a little small on the gate as not running the boost i was expecting too, so need a controller to get it set right

So you have selected a small gate and running too much boost? or one that is too large and bypassing too much air?

I would look at the AVCR. or Blitz SBC-iD.

They are well priced.

I haven't got any direct experience with the AVCR but it is supposed to be good when you work out how to use it.

The Blitz SBC-iD was good but the version I had (2) had a couple of little bugs in the auto mode (slight over boost when sitting at a constant speed/load on boost up a hill then planting it)

When in manual mode I didn't have this problem, but as I said I would then have the problem of boost dropping in higher rpm's.

What I did to get it working a little better was to set up a scramble channel that ran the manual mode for say 1-2 seconds after it initially saw any positive manifold pressure, after the 2 seconds it flicked to the auto mode channel. This removed the slight spike caused by the auto mode's learn feature and gave a slight increase in boost response. The auto mode does tend to not feel as responsive when coming on to boost.

A friend had a Greedy E-01 which also had this issue. BUT I haven't heard of this problem from the AVCR.

Maybe grab a copy of the AVCR EBC manual and check it out Clint.

EDIT: http://www.apexi-usa.com/productdocumentat...s_savcr_ins.pdf

[Nacho Vidal]

With a Electronic Boost control can you alter boost pressure at different rpms.  Im getting 17psi at 4500rpm and then it drops off too 12psi and peak revs.  This is using a HKS actuator and no bleed valve so its not the actuator spring.  So i thought with a EBC could i dial in more boost pressure at say 6000rpm.  

Can i do this?

Hi robos.

speaking from direct experience with the 2530 on an RB25, good luck if you go looking for that top end boost!

Ive read all the discussion here and its good, it does make sense, but i believe you will be wasting your time and money!

Cubes is certain you can do it, so maybe get him to reimburse your costs if it doesnt work

Bottom line is for whatever technical reason, the 2530/RB25 will NOT hold 17psi at the top of the rev range. Ive tried numerous EBCs including the E-boost, which while i think cubes pointed out is not a learning one or whatever, it does have the function of supplying NO signal to the gate actuator until a certain pressure which you set is reached. So i played with that for ages, couldnt get boost to hold. Then i put on a propper 1.2bar wastgate actuator- just watch the boost guage as it revs out, the boost will fall off just the same. Even attached extra springs to put more pressure on the gate to try and hold it closed, boost still drops off. I even tried different dump pipes, split, open, etc, to no avail.

Im thinking a few things. that the turbo doesnt flow enough air to hold the boost up top. also as mentioned the rb25 spins the little 2530 out of its range.

Guys just remember while the 2530 is a great turbo, it is definitly much overestimated. Get hold of one, the things are tiny. Also this misconception that just coz its HKS that "its only getting started at x-Bar boost"... your still governed to physics and you still need a propperly matched turbo for your engine!

Robos: Lots of good discussion here! while im aware of tim's status and his worldly travels, and do believe he knows his stuff, i would be listening to the people who have gone the hard yards in this SPECIFIC setup. As turbo Tits said, those who have tried it have done so at considerable time and cost, and you can benefit directly from our experiences! I am not saying that you wont be able to pull together every little trick in the book and maybe get an extra psi of boost or something, but im telling you now, you wont see more than ~230rwkw from an RB25 on pump fuel with your turbo. The 2535 will give you that extra top end your chasing.

[brett33]

and you know this because why?

do you know where a 2530's Efficiency range is?

its certainly not at low boost - 10-15psi. HKS turbos are designed to perform better at higher boost... not just "make hot air"

Nothing to do with boost. More to do with flow rate.

How much difference do you think going from 15 to 30 psi on a 5ltr would make.

Probably still in its effeciency though??

[Cubes]

My point is I believe you can get the turbo holding more boost than the 12psi in the top end with a good boost controller. Even if it is only another 2psi it may be enough to make just that little bit more top end and squeeze every little bit out of the turbo.

Sure you may not get to 17psi due to excessive scroll pressure forcing open the wastegate but you may get enough to pull another 10-15rwkw.

The most I've seen from a 2530 is 240rwkw.

Nacho, Its interesting as what you speak of is the same brick wall the 2835ProS hits at around 280rwkw. Hold the wastegate shut and it will hold boost and make 300rwkw. Connect the actuator up and it will drop boost?!?!?

[Nacho Vidal]

like i said cubes, i stated in my last post he may get an extra psi or 2, the point is that it wont hold significant boost up top.

it is interesting you are so sure about your boost controller theory, please go try it and show me the results! not having a go, but your saying "just go do this and im sure it will work" without having done it yourself. Now dont take that wrong, you may be the learning EBC king, but until youve tried it on an rb25 with a 2530, its all just theory, and would be more help to robos if it were proven!

i know of a stock turbo r33 doing 220rwkw at just over a bar. Like the 240rwkw example you mentioned, its a one off. the fact is that 2530's on rb25s average ~220rwkw.

[Cubes]

Nacho,

I was pointing out that it may be EBC related as the ebc robo is using tends not to hold boost higher in the rpm ranges even on a stock turbo.

I was speaking from experience with the VG30DET turbo, RB25DET turbo and RB20DET turbo. VG30DET & RB20DET turbo's have all dropped boost higher in the rpm' ranges on my car. The Rb25DET turbo I saw on another car.

For me the good boost controller fixed the problem. From there I went on to modifying the actuators bracket which is basically reducing the wastegate travel in order to hold boost higher in the rpm range.

This allows the stock turbo to hold higher 15-16psi boost levels higher in the rpm range without boost drop off.

As I said from the beginning.. The aim is to squeeze just a little more out of the turbo.

Sure you may get it holding 30psi if you hold the wastegate shut by hand but really this would be pointless as the air would be superheated, the turbo will most probably be overspeeding and either damage the motor and or the turbo. I am all too aware that more boost doesn't always = more power.

Do you now know what I have been saying all along?

In order to squeeze every little bit out of the wastegate.

Robo,

Really you only have two options.

If it is correct that even a 20psi actuator will be forced open then your only option is to get your self an adjustable actuator that can reduce its travel to force the exhaust's energy through the turbine. Get a big stick and hold the wastegate closed, i'm sure boost will be higher than 12psi above the 5500rpm or where ever abouts boost is dropping from.

[Nacho Vidal]

yes cubes i do understand what your saying, i was never confused.

Thats good that you have experience with all those engines, but i still dont see RB25DET running an GT2530 on your list. Hence the point i am trying to make- I never said your solution simply doesnt work, and i have said he may get a tiny bit extra (which is not going to be worth the cost of a learning EBC anyways) my point is to listen to my and others experiences WITH THIS TURBO ON AN RB25!!!! and save Robo's some time and money!!

Bottom line is, anybody can tell me i can do anything, but then if i ask them, "so you have done this for yourself with the same setup as mine?" and they say "well actually no i havent". well then thats great.

there is nothing wrong with people posting opinions and theory's in order to help each other out, but i always prefer first hand info thats all..!

Robos, youve been pretty quiet, please go and try these things out and get back to us, as if it can be done to achieve significant power increase i would really like to know what ive been missing!!!

[Cubes]

I gave Robo a few options to look in to, + I shed some light on EBC's which many do not realise.

Its much better than simply stating 'no you can't do it'.

Nacho... So can you tell me exactly what was causing the boost drop?

Was it the wastegate being forced open? I suspect this is the case.

Have you attempted to reduce the wastegates travel?

If the flap is being forced open then reducing its total travel will help direct more of the exhausts energy through the turbine.