boost pressure issue, more then 1,3bar are not achievable

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Zenki
 

Posts: 54
Joined: Mon Feb 02, 2009 3:13 am

boost pressure issue, more then 1,3bar are not achievable

Post by Zenki »

I am not able to achieve more boost then 1,25-1,3 bar and I don’t know why

-> I have done a pressure test to check the piping and all hoses are leak proof with 2,0 bar.
-> I have tested a OEM actuator same result
-> I have testes a new HKS actuator same result
-> I have tried the boost controller AVCR same result
-> I have tried a new greddy profec boost controller same result max. 1,3 bar.
=> The setting at the boost controller where at the max. full set and gain

Spec List:
SR20DET Blacktop
Stock cams
Stock manifold
Garrett GT2871r 0,86
HKS actuator
3 inch free flow exhaust
FMIC
Bosch 044 Fuel Pump
740cc Nismo injectors
Bigger oil sump
Oil cooler
52mm water cooler

full load
timing:
3650-4800 12°
5200-6500 13°
7000 14°
AFR
11,5-11,8 (fuel 98 octane)
unex
 

Posts: 86
Joined: Sat Aug 06, 2011 6:59 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by unex »

1. try disconnecting actuator vacuum and run in 4th or 5th gear (the things going slower) and see if boost goes over 1,3
2. are you sure that exhaust gaskets are not blown? especially manifold-turbo
Zenki
 

Posts: 54
Joined: Mon Feb 02, 2009 3:13 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by Zenki »

unex wrote:1. try disconnecting actuator vacuum and run in 4th or 5th gear (the things going slower) and see if boost goes over 1,3
2. are you sure that exhaust gaskets are not blown? especially manifold-turbo
2. gaskets are fine. manifold-turbo checked about 500km ago (exhaust housing was changenged to 0,86ar)
louiswun
 

Posts: 256
Joined: Tue Apr 07, 2009 1:11 am
Location: Hong Kong

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by louiswun »

2 case I had see

Case 1, CA18DET with a copy GT2871R 0.64 rear housing, not able to achieve more boost then 1 bar, and boost come lazy.
-> I have done a pressure test to check the piping and all hoses are leak proof with 2,0 bar.
-> I have testes a new 1 bar adjustable actuator, same result.
-> I have tried the boost controller AVCR, same result.
-> I have tried the boost controller Greddy Profec, same result.
-> I have tried disconnecting actuator vacuum hose on that new 1 bar adjustable actuator, same result.

Conclusion, exhause housing inside pressure push open the accuator flip door.
The accuator control arm angle vs accuator flip door angle plays a part.
Thats accuator rod travel vs accuator flip door angle.

Solution, weld shut the internal wastegate door, weld an external wastegate pipe and flenge, fit a 38mm external wastegate, boost not just controllable, it also come earlier.



Case 2, SR20DET with a genuine Garrett GT3071R 0.64 GT28 rear housing, not able to control boost, always overboost.
-> Tested everything you can think of, same result
-> Tested few actuator, same result
-> Tested few boost controller, same result
-> Tested direct actuator vacuum hose from intake plenum without any boost controller. same result
-> Tested totally remove accuator and let the internal wastegate flip door move freely, same result

Conclusion, exhause housing too small + turbine exducer too small + internal wastegate hole too small
Even the flip door totally open, the internal wastegate hole still not enought flow area for the exhause air flow quantity

Solution, weld shut the internal wastegate door, weld an external wastegate pipe and flenge, fit a 38mm external wastegate, no longer any overboost, boost steady and it is controllable.


Exhause housing size and turbine size are the biggest limiting factor on making reasonable power from the compressor,
especially on Garrett compressor to turbine matching, always use 1 step smaller turbine to achive quicker spool, always maxed the turbine flow but compressor still have room to flow more. Always need to tune richer to control the EGT.
If it is aim at performance, I prefer to use a turbo with a bigger turbine, give up some spool, to trade with higher top end, lower exhause pressure, lower EGT even with leaner AFR, also less prone to knock.
Attachments
Temp73.jpg
Accuator control arm angle
Blue line = Garrett GT25/GT28
Red line = accuator flip door angle
(86.76 KiB) Downloaded 4767 times
Temp72.jpg
Accuator control arm angle
Green line = copy GT2871R
Blue line = Garrett GT25/GT28
Red line = accuator flip door angle
(84.38 KiB) Downloaded 4767 times
Zenki
 

Posts: 54
Joined: Mon Feb 02, 2009 3:13 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by Zenki »

unex wrote:1. try disconnecting actuator vacuum and run in 4th or 5th gear (the things going slower) and see if boost goes over 1,3
tried it today, max. 1.3 bar


=> I checked my pcv valve it, it does not close well in direction valve cover. I ordered a new one.

Could this small issue make such a big problem?
pcv.jpg
(66.93 KiB) Downloaded 4761 times
Zenki
 

Posts: 54
Joined: Mon Feb 02, 2009 3:13 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by Zenki »

@ louiswun

Garrett 3071r with 0,64 AR @ SR20DET

you have to port the exhaust housing, then it will work, done at a mates car+ forge actuator

Garrett 2871r with 0,64 AR @ CA18DET
the 56trim version works well, good boost controll, also with stock manifold
louiswun
 

Posts: 256
Joined: Tue Apr 07, 2009 1:11 am
Location: Hong Kong

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by louiswun »

Zenki wrote:
unex wrote:1. try disconnecting actuator vacuum and run in 4th or 5th gear (the things going slower) and see if boost goes over 1,3
tried it today, max. 1.3 bar


=> I checked my pcv valve it, it does not close well in direction valve cover. I ordered a new one.

Could this small issue make such a big problem?
Why not temporary block up the hose to the pcv valve and test again ?
unex
 

Posts: 86
Joined: Sat Aug 06, 2011 6:59 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by unex »

louiswun wrote:
Case 2, SR20DET with a genuine Garrett GT3071R 0.64 GT28 rear housing, not able to control boost, always overboost.

Conclusion, exhause housing too small + turbine exducer too small + internal wastegate hole too small
Even the flip door totally open, the internal wastegate hole still not enought flow area for the exhause air flow quantity
conclusion is very not true. Because of quite big exhaust housing, and free flow exhaust, exhaust gases are easier to go through turbine wheel, not through wg. Yes, your solution also works, because to go through external wg is much easier neither turbine wheel, but there are also two more solutions:
1. ported wg, as somebody already said that.
2. little bit restriction in exhaust (also overboost problem comes when people do tuning without exhaust at all, so this is the reason why it should be fitted). You can try putting silencer and you will see how boost becomes controllable.

edit:
forgot to mention third overboost reason. Sometimes over rich mixtures causes overboost, because fuel is more heavy than air, and it spools up turbine more. So, sometimes going leaner helps to reduce overboost. Its not theory, I have seen this.
Zenki
 

Posts: 54
Joined: Mon Feb 02, 2009 3:13 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by Zenki »

louiswun wrote:
Zenki wrote:
unex wrote:1. try disconnecting actuator vacuum and run in 4th or 5th gear (the things going slower) and see if boost goes over 1,3
tried it today, max. 1.3 bar


=> I checked my pcv valve it, it does not close well in direction valve cover. I ordered a new one.

Could this small issue make such a big problem?
Why not temporary block up the hose to the pcv valve and test again ?
So i have tested, same result :(

anybody else a new idea?
unex
 

Posts: 86
Joined: Sat Aug 06, 2011 6:59 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by unex »

Zenki wrote: anybody else a new idea?
how your intake looks like?
air filter can do something like this: https://www.youtube.com/watch?v=fwLySsn ... ture=share
stock intake hose also can do the same
Zenki
 

Posts: 54
Joined: Mon Feb 02, 2009 3:13 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by Zenki »

unex wrote:
Zenki wrote: anybody else a new idea?
how your intake looks like?
air filter can do something like this: https://www.youtube.com/watch?v=fwLySsn ... ture=share
stock intake hose also can do the same
I am using a modifided stock airbox, with a K&N replacement filter

Image

From the turbo I am using a 90° Samco bow, which enters then into a 90° 76mm aluminum bow and after it goes to the MAF
unex
 

Posts: 86
Joined: Sat Aug 06, 2011 6:59 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by unex »

Zenki wrote:I am not able to achieve more boost then 1,25-1,3 bar and I don’t know why
-> I have done a pressure test to check the piping and all hoses are leak proof with 2,0 bar.
how you did pressure test? a lot of people doing it wrong. Best way to do that is: remove MAF and put z32 fuel filter into maf place (fits perfectly). Dont do any more changes and via fuel filter blow 1bar.
Zenki
 

Posts: 54
Joined: Mon Feb 02, 2009 3:13 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by Zenki »

unex wrote:
Zenki wrote:I am not able to achieve more boost then 1,25-1,3 bar and I don’t know why
-> I have done a pressure test to check the piping and all hoses are leak proof with 2,0 bar.
how you did pressure test? a lot of people doing it wrong. Best way to do that is: remove MAF and put z32 fuel filter into maf place (fits perfectly). Dont do any more changes and via fuel filter blow 1bar.
I use a self made plug to block the intake side at the maf.

At the hotpipe I go inside with air
louiswun
 

Posts: 256
Joined: Tue Apr 07, 2009 1:11 am
Location: Hong Kong

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by louiswun »

Did you try adjust to more spring load on the HKS actuator ?

=> The setting at the boost controller where at the max. full set and gain
The way you adjust the set and the gain to the max, it is almost leak away all the pressure to the actuator,
if you tried disconnecting actuator vacuum hose still cannot get more boost than 1.3 bar, it is either actuator spring not strong enough or you have too much exhause pressure inside the exhause housing.
unex
 

Posts: 86
Joined: Sat Aug 06, 2011 6:59 am

Re: boost pressure issue, more then 1,3bar are not achievabl

Post by unex »

louiswun wrote: or you have too much exhause pressure inside the exhause housing.
because this is impossible with such turbo and 1.3bar, so its definitely problem with actuator.
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