[Mk2] [Turbo] Borg Warner EFR - boost drop at higher revs - end of ideas

[bambam79]

Hi everyone,

perhaps someone can lead me to the vital point.

My engine cannot hold boost higher than 0.8 bar at higher pm.
0.8 it holds till 7200rpm no Problem
1.0 bar starts to go down to finally 0.8 bar at about 6000rpm
1.2bar -> 1.0 bar from 5500 rpm
1.5bar -> 1.2 bar from 5000 rpm






first graph shows oil pressure, oil temp, intake temp etc
second graph blue is rpm, pink is intake pressure (absolute)
third graph egt (maximum is 750°C)
forth graph throttle position sensor, the green line is fuel pressure

I built my engine with the following specs:
(loose clamp on the silicone hose coming from the turbo is fixed by now of course)


3sgte rev3
264 JUN camshafts set to standard position like originals (nothing dialled in specificly, just Toyota recommended setup)












URL=http://s283.photobucket.com/user/timtay ... 6.jpg.html][/URL]

JUN valve springs
Mahle pistons C/R 9.0:1
Eagle con rods
ACL race bearings
arp head studs
BMC Carbon airbox / no switched to a HKS intake including the mushroom filter
Delphi 870 injectors
COP conversion
Denso IK24 spark plugs
head skimmed 0.2mm
HKS stopper head gasket 1.6mm
Mongoose exhaust (2.5" restriction removed, now full 3" with v-band)
BorgWarner EFR 6758 turbo
3" downpipe
custom full race style tubular manifold

charge cooler
Syvecs S6 ECU (brilliant piece)
sensors for egt, oil pressure, fuel pressure, oil temp (everything reads fine and doesn't tell a problem)

My first guess was the wastegate actuator might be too weak so I switched for a high boost one. Connected it directly to the turbo so it opens not until 1.1 bar is reached -> now I can drive 1.1 bar until about 5500-5700 and then the boost starts dropping to about 0.8bar at 7300rpm

next try was the BMC airbox which I reülaced with the HKS intake with the "mushroom" filter ... problem stays the same

3rd guess exhaust too restrictive, so quick pull in 3rd gear with only the downpipe on....deafening loud but still boost drops

4th checked every vacuum line, sprayed brake cleaner while idling... no sign of a leak

manifold and turbo taken off to check for gasket failure, but both gaskets were fine and not blowing. New gaskets installed.

double tightened every boost tube silicone coupler ... nothing

charge cooler is a BMW custom build and rated for well over 500hp so I guess, not too restrictive intake temps stay under 30°C when doing a quick pull in 3rd


Is there anything I might have missed? At the moment I am making 388fwhp and with 1.5bar till redline I should easily see 4xxfwhp and won't have that nasty torque drop at 5000rpm

[Marf]

Something is restricting flow up top...

Either it cannot get enough air in or it cannot get enough air out.

Hotside too small?
Cams adjusted properly?

[bobhatton]

What fuel do you run on?
What is your piston to head clearance with that thick head gasket; it should only be 1mm?
What is your measured compression ratio?

Have you plotted your total air flow on the turbo compressor map to check it is the correct size?

Control for the waste gate should come from the inlet manifold not turbo or pipe work.

[ashley]

Control for the waste gate should come from the inlet manifold not turbo or pipe work.

That doesn't sound right, reference pressure should come from a point pre-TB shoudn't it?

[Marf]

Control for the waste gate should come from the inlet manifold not turbo or pipe work.

That doesn't sound right, reference pressure should come from a point pre-TB shoudn't it?

Should come from a point closest to where the charge air enters the engine.

[ashley]

The way Dave Rowe (and others) have explained it to me- you can take the boost reference from the manifold, but when you slam the throttle closed you expose the wategate reference port to a vacuum- which it is not set up to deal with. The "better" way to do it is to take boost reference from pre-TB, this can be pre or post intercooler...but most common is from the compressor housing itself.

Like this:

http://www.turbosmartusa.com/technical- ... tallation/

Just to confirm- we are talking reference pressure for the wastegate here, not where you would take a MAP reading- which obviously needs to be in the inlet manifold itself

Apologies- off topic for this thread though...

[bobhatton]

The way Dave Rowe (and others) have explained it to me- you can take the boost reference from the manifold, but when you slam the throttle closed you expose the wategate reference port to a vacuum- which it is not set up to deal with. The "better" way to do it is to take boost reference from pre-TB, this can be pre or post intercooler...but most common is from the compressor housing itself.

Like this:

http://www.turbosmartusa.com/technical- ... tallation/

Just to confirm- we are talking reference pressure for the wastegate here, not where you would take a MAP reading- which obviously needs to be in the inlet manifold itself

Apologies- off topic for this thread though...

The "better" way is the manifold as the waste gate will slam shut as soon as the throttle is closed instead of hanging open till the pressure has dropped pre throttle body.
The vacuum pressure is much lower than most boost pressures so will do no harm to a waste gate, and can give better control as it is seeing the same pressure the engine is. Taking the pressure from the turbo, this will change with the back pressure from the intercooler as the air flow goes up and down. This means the engine will get a lower pressure at higher air flows because the signal at the turbo will be higher than the manifold.

Every turbo car I have worked on since 1972 I have had the WG signal from the manifold.

[bambam79]

wow, quite some input Thank you very much.

First of all, thanks Ashley for clarification.
Boost reference for the wastegate is taken from the compressor housing as shown in the link.

The MAP-sensor gets it's pressure from the intake manifold after the TB.

Now for the rest:

What fuel do you run on?

RON 98+

What is your piston to head clearance with that thick head gasket; it should only be 1mm?

Unfortunately I don't know. I think this is hard to measure when the head is on, isn't it? The head was skimmed 0.2mm; genuine Gen3 headgasket has 1.0mm and I was advised to take the 1.6mm headgasket from HKS (I still have the genuine Toyota Gen3 headgasket at home and if everything fails, I can put this back on, but first I want to make sure it is nothing else possible causing this problem.

What is your measured compression ratio?

another thing I didn't measure. I put in the 9.0:1 compression pistons, -skimmed block + thicker headgasket = should be something between 8.5 and 9.0:1
So the slightly lower compression should make way for the higher boost at cost of fuel economy on lower revs. But I doubt this should effect the boost at higher revs?

Have you plotted your total air flow on the turbo compressor map to check it is the correct size?

this is the compressor map for my turbo:

unfortunately I don't know how to plot my total airflow to this map. A friend of me has the same turbo on it's rev2 turbo (same pistons) and he has no problems with boost drop at higher revs.

Either it cannot get enough air in or it cannot get enough air out.

That's why I took off the exhaust and tried the HKS intake. Again, friend of me with the same exhaust has no problems

Hotside too small?

On the fullrace you have some dynocharts.
http://www.full-race.com/store/turbos/b ... turbo.html
Here you can see, that this turbo should easily hold 1.7bar

Cams adjusted properly

They are not specifically dialled in. They are just set to the Toyota specifications as you can see in my post further on. I have not retarded any cam so my idle is nice, nut lumpy.

[bambam79]

[quote="bobhatton
The "better" way is the manifold as the waste gate will slam shut as soon as the throttle is closed instead of hanging open till the pressure has dropped pre throttle body.
The vacuum pressure is much lower than most boost pressures so will do no harm to a waste gate, and can give better control as it is seeing the same pressure the engine is. Taking the pressure from the turbo, this will change with the back pressure from the intercooler as the air flow goes up and down. This means the engine will get a lower pressure at higher air flows because the signal at the turbo will be higher than the manifold.

Every turbo car I have worked on since 1972 I have had the WG signal from the manifold.[/quote]

Here is the way it is set up by Borg Warner themselves:

the boost is sent from the compressor housing to the solenoid that is attached to the compressor housing as well. From that you are supposed to connect the correct side (which I did, nearly triple checked and I can see on the datalogs when looking at the duty cycle of the wastegate actuator, that this is working fine) of the solenoid to the wastegate

[ashley]

This means the engine will get a lower pressure at higher air flows because the signal at the turbo will be higher than the manifold.

But if it was set up this way when you mapped the car, and you mapped boost control as a function of MAP, then it will make no difference to the absolute pressure levels achieved for the engine will it? We're just talking about a "reference" pressure for the waste gate here, not about the actual boost pressure the ECU lets the engine see, and as far as I can see- the more stable the "reference" pressure the better?

I originally had my wastegate taking a line from the inlet manifold and was strongly advised to change it by those who have far more experience than me....and to be honest I have not noticed any change in boost control as a result, so perhaps it's another one to go in the "academic arguments" pile for our cars

[bobhatton]

This means the engine will get a lower pressure at higher air flows because the signal at the turbo will be higher than the manifold.

But if it was set up this way when you mapped the car, and you mapped boost control as a function of MAP, then it will make no difference to the absolute pressure levels achieved for the engine will it? We're just talking about a "reference" pressure for the waste gate here, not about the actual boost pressure the ECU lets the engine see, and as far as I can see- the more stable the "reference" pressure the better?

I originally had my wastegate taking a line from the inlet manifold and was strongly advised to change it by those who have far more experience than me....and to be honest I have not noticed any change in boost control as a result, so perhaps it's another one to go in the "academic arguments" pile for our cars

With an ECU type boost controller your sensor for the boost is from the manifold via the MAP sensor and then just using the before TB line as the pressure to open the WG, that works ok
Stock and manual controllers are better from the manifold

[ashley]

With an ECU type boost controller your sensor for the boost is from the manifold via the MAP sensor and then just using the before TB line as the pressure to open the WG, that works ok
Stock and manual controllers are better from the manifold

[bambam79]

With an ECU type boost controller your sensor for the boost is from the manifold via the MAP sensor and then just using the before TB line as the pressure to open the WG, that works ok
Stock and manual controllers are better from the manifold

Well. My Syvecs ECU controls the boost and it it gets it's values from the MAP sensor in the manifold. And I am using the before TB line to control the pressure to open the WG. So this part should be fine.
I have no manual boost controller installed.

So the problem must be caused by something else

I will try to do a compression test later today or by tomorrow as it is quite rainy today and I will have to drive the engine warm prior to testing.

But the engine was brand new machined to accept my 86.5 mm pistons by a machine shop. And I thought, they know what they were doing. As the problem occurred from the first mile since I got the engine back together (ok the first time I was aware of this problem was on the tuning session on the dyno after about 1000running in miles), I thought there must be another thing playing tricks on my boost.

[bobhatton]

[quote="bobhatton
The "better" way is the manifold as the waste gate will slam shut as soon as the throttle is closed instead of hanging open till the pressure has dropped pre throttle body.
The vacuum pressure is much lower than most boost pressures so will do no harm to a waste gate, and can give better control as it is seeing the same pressure the engine is. Taking the pressure from the turbo, this will change with the back pressure from the intercooler as the air flow goes up and down. This means the engine will get a lower pressure at higher air flows because the signal at the turbo will be higher than the manifold.

Every turbo car I have worked on since 1972 I have had the WG signal from the manifold.

Here is the way it is set up by Borg Warner themselves:
Image Replaced With URL For Quote http://www.full-race.com/store/images/f ... tent-4.jpg
the boost is sent from the compressor housing to the solenoid that is attached to the compressor housing as well. From that you are supposed to connect the correct side (which I did, nearly triple checked and I can see on the datalogs when looking at the duty cycle of the wastegate actuator, that this is working fine) of the solenoid to the wastegate[/quote]

An easy thing to try is take the signal from the manifold and put a plug into the turbo, that way you will not see any of the back pressure building up in the charge cooler and pipe work. The turbo may well be giving 1.5 bar boost at its sensor but with the back pressure you may only get 1 bar in the manifold.
If your boost controller is taking its signal from the manifold then forget the above

The cams should have a spec sheet, they need to be set up to the spec sheet and not the stock cam markings.

Do you know what sort of ignition advance you have at higher boost and revs?

What is the AR of the exhaust housing?

[bambam79]

An easy thing to try is take the signal from the manifold and put a plug into the turbo, that way you will not see any of the back pressure building up in the charge cooler and pipe work. The turbo may well be giving 1.5 bar boost at its sensor but with the back pressure you may only get 1 bar in the manifold.
If your boost controller is taking its signal from the manifold then forget the above

I can do this, but as my boost controller is the ECU, I think this is as you said, pointless, I'm afraid.
But I am thinking of wiring in an additional sensor to my ECU and to test several positions such as before the intercooler, to show how much backpressure this builds up.
I will also try to install it in the exhaust to see if there are some problems to be expected there.

The cams should have a spec sheet, they need to be set up to the spec sheet and not the stock cam markings.

I have bought the cams second hand here on imoc. Unfortunately whithout a spec sheet. So I set them to stock cam markings. Is this likely to cause such a problem? Idle is perfect and the boost up to 0.8bar is held fine up till redline?
Maybe I should contact JUN to get a spec sheet of the cams? When I dial them in different, I guess I have to visit a dyno afterwards, right?

Do you know what sort of ignition advance you have at higher boost and revs?

12.44°BTDC 6800rpm 0.91bar
10.22°BTDC 6800rpm 1.18bar
7.94° BTDC 6800rpm 1.45bar

11.44°BTDC 5600rpm 0.91bar
9.19°BTDC 5600rpm 1.18bar
6.97° BTDC 5600rpm 1.45bar

if you want a specific one, just let me know

What is the AR of the exhaust housing?

according to the fullrace homepage:
BorgWarner EFR 6758 Turbo
The EFR 6758 is a remarkably versatile turbocharger, packaged in the compact B1 EFR frame. The compressor offers broad map width for outstanding power potential in a variety of applications from rally, drift, road racing, autocross, drag and street driven applications. This FMW compressor wheel measures 53.9mm inducer with 67mm OD compressor to support a 53lb/min max flow rate. The EFR 58mm turbine wheel is made of Gamma-Ti for low inertia and an optimal match for the FMW compressor wheel. Ideal for use in single turbo applications for the 300-450hp range, or as twin turbo applications 550-900+hp. Ceramic Ball Bearing only, watercooling recommended.

Compressor Specifications
◾Compressor Wheel OD (exducer): 67mm
◾Compressor Wheel Inducer: 53.9mm
◾Max Flow Rate: 53 lb/min
◾Built-in BOV: All EFR compressor housings incorporate an integrated BOV.
◾Compressor Housing: 2.5" inlet, 2.0" hose coupler outlet

Turbine Specifications
◾Turbine type: Low Inertia Gamma-Ti Turbine Wheel
◾Turbine Wheel OD: 58mm
◾Stainless Steel Investment cast Housing
◾0.64 A/R T25 Undivided (Internal WG) - Part # 179388
◾Turbine outlet: GT-Vband (aka small 3" vband) ~92mm OD for all EFR turbos

Features
◾Dual Row Ceramic Ball Bearings - lowest friction and fastest spool/response, most extreme durability, built-in oil control orifice - (aka oil restrictor) **no restrictor can be used with EFR turbos
◾Watercooled Center Section - watercooling is recommended, 14mm banjo bolts
◾Double seals on both turbine and compressor end for extreme durability and resistance to any oil seepage
◾Boost Control Solenoid Valve Integrated to Compressor Housing
◾Integrated Speed Sensor mounting provision

[Marf]

I think your hotside is too small personally..

[bambam79]

I think your hotside is too small personally..

It is the most obvious thought, I have to admit, but how comes, that other people drive this turbo with 1.7 bar all the way to the redline?
Or my friend, 3sgte rev2 1.3 bar all the way till the end, without any problems.

And well, if the hotside is kind of small for let's say "higher" pressure... then 1.0bar is NOT high. This thing should develop 1.0 bar all the way to the end when set to 1.0 bar, don't you agree?

It can do 1.2 bar at 7000rpm when set to 1.5 bar.

And over here there are many guys driving this particular turbo on the 2.0 TFSI VAG engine with up to 2 bar without any issues. So I think this hotside must be able to handle this boost. and being not capable of more than 0.8 bar of boost.... it's not a CT26 I have put on my car


Is it likely that wrongly dialled in cams cause such problems? And this at higher boost only? These cams are, as far as I can consider, the only hardware difference between me and my friends car. Except that he has a rev2 and I have a rev3 and he uses the standard exhaust manifold and I use the stock one. He also has the rev2 intake manifold where my rev3 intake manifold should be better as well. And my TB is also slightly bigger. So why can he produce 1.3 bar and I can't?
Is this caused by the fact, that the rev2 intake is more restrictive and the TB is smaller so that his 1.3 bar are a smaller "air mass" than my rev3 1.1 bar?

Another thing... the exhaust manifold runners are not equal length.... possible problem? Guess not.

[Marf]

You have different cams which all the engine to breathe better, that could account for it.

Bob may be able to comment better than I

[ashley]

I think your hotside is too small personally..

Then he'd see EGT's climbing rapidly as boost was increased wouldn't he?

EDIT: my money's on cam timing as well

[Marf]

I think your hotside is too small personally..

Then he'd see EGT's climbing rapidly as boost was increased wouldn't he?

Not sure, if boost cannot rise as the turbine can't spin any faster due to the hotside being too small then would EGT rise?