Couple of boost/vacuum question - GTB BH5 Rev D

[Guest]

Hi all,

Well, finally got my boost gauge plumbed in correctly, and wanting to know if the readings sound pretty good...

On the first turbo, she reaches 14psi, then there is a drop down to 10psi and then the second turbo will boost up to about 14.7psi.

Do these sound about right for a Rev D? Looks good to me, but wanting your opinions...

Now, i'm not sure if i'm just used to the car now or if it's just that the car is still very tight and smooth, but it feels gutless - any ideas?

[Guest]

That sounds about right.

Compared to a single turbo setup... they definitely feel slower cos you wait for so much longer for that shove in the back lol!

[funkytown]

 DarkCrystal GTB said:

On the first turbo, she reaches 14psi, then there is a drop down to 10psi...

that doesnt sound quite right.. boost spiking a little high i would have thought.

[Guest]

I figure the drop to 10psi is just moving onto the 2nd turbo - the so-called VOD... but it only drops for a split second, you can hardly feel it happen... i believe the VOD was significantly reduced on the rev D..

[Ammon666]

I know on my GTB primary stage is 11psi and then secondary stage is 16psi. Don't know to much about the later twin turbos but I would have thought there would have been a bigger difference between first and secondary stages. 14psi on the primary turbo seems a lot when both turbos it's only 14.7psi.

[Guest]

Yeah, i'm a bit puzzled myself... figured with the smaller turbo's the rev d's supposedly have, i thought they'd boost a bit higher...

FORGOT to mention something here... i broke a vacuum tube (snapped in the middle)... was about 80mm long... it's a solid tube and looks like it may be some kind of restricter... normal vacuum size at either end, but about 2.5mm in the middle... i didn't have a spare, so used normal vacuum tube to repair.. good or not?

[funkytown]

 DarkCrystal GTB said:

Yeah, i'm a bit puzzled myself... figured with the smaller turbo's the rev d's supposedly have, i thought they'd boost a bit higher...

FORGOT to mention something here... i broke a vacuum tube (snapped in the middle)... was about 80mm long... it's a solid tube and looks like it may be some kind of restricter... normal vacuum size at either end, but about 2.5mm in the middle... i didn't have a spare, so used normal vacuum tube to repair.. good or not?

ah that might do it.. that might be the "pill" . you want/need that.

14psi on primary is to much. it should do about 10-11 on primary and 14-15 when both are humming.

[ODB]

 SpotMe said:

That sounds about right.

Compared to a single turbo setup... they definitely feel slower cos you wait for so much longer for that shove in the back lol!

do you think so?

Personally the BH GTB i am currently driving I find it actually quicker than the Turbo Forester I own and on a par with the WRX i did own in a straight line for daily driving.

It came ex Japan with a few STi bits and bobs so Im unsure as to the exact mods on it but for all intents and purposes it appears stock.

Personally I prefer the GTB to single turbo models for its refined driving and smoothness(and loving the full leather interior). I rate it highly on the proviso that it will be driven in standard trim. It can carry 5 and fit 2 sets of golf clubs in the back with ease and still goes well.

Obviously if you are planning to hit the engine with mods your priority will change but i feel that there is too much dissing the twin turbo models on here.

Particularly the BH, they are decent!

[funkytown]

which revision BH are we talking tho.. they get better and better as time goes on.

agree with your other sentiments tho. I had a BG and i loved it. they are quite quick - deceptively so.

I would imagine it wud stay on par with a WRX in a straight line easily. plain WRX's arent "that" fast imo.

mod stick = get a single to start with thats for sure.

but your point stands and i concur.. horses for courses.

[Guest]

Well i have pretty much no lag at all... i'm boosting from about 1500rpm all the way through till redline... iv'e only had one single turbo car which was a GTSt skyline... definitly quicker than my GTB, but the TT GTB has a bit more down low torque...

[ODB]

actually i want to buy this GTB of my parents!

Its the only one i have found manual, wagon and full leather interior!

Nevertheless a GTB wagon will be my next subaru!

Im getting to be an old prick. I cant see myself modding future cars engine wise and creature comforts and boot size for snowboard etc are major concerns now, rather than outright quickness!

[Guest]

Although this pic is from an earlier model TT, it has the same vacuum line i broke... it's the one coming off the blue T connector - the short one... basically looks to be about 100mm long... and the hole inside is about 2mm and takes up most of the length of the pipe... so definitly need to replace that one? Anyone know what it's called?

Okay, so the pic aint working... here's the link... works if you 'Zoom' on the pic... otherwise it don't appear to be there!

http://media.photobucket.com/image/subaru%20legacy%20vacuum%20restrictor/mark240973/Legacy%20B4/Legacyvacuumlinesinspection008.jpg

*pic should work now -smurff

[Guest]

Unfortunately I've had my Rev D tuned so I don't remember exactly but I do remember it boosting up to 1 bar on primary and 1.1 spiking to 1.2 bar on secondary.

You'd see 1 bar on primary normally when on the motorway in 4th or 5th and planting it. It wouldn't normally hit that high in a straight line through the gears from memory.

Note that I said *feels* slower, not that it is slower than a single turbo setup. I drove Drunken's BG with a VF23? on it for a number of weeks and that hit of boost at 3000-3500 was very very addictive. For the same hit in the BH twin you have to wait for 4500-5000. Before that though, the BH is quicker and more pliable due to the early boost of the primary.

[Guest]

 

Unfortunately I've had my Rev D tuned so I don't remember exactly but I do remember it boosting up to 1 bar on primary and 1.1 spiking to 1.2 bar on secondary.

Thats pretty much what mine is doing...

Spoke to Winger (grrrrr) and of course they don't have the hose in stock... but they reckon it shouldn't make SFA difference as it's after the turbo... and i don't trust them - what do you guys think?

[funkytown]

ask boostin - he'll tell you for sure..

hes a subbie tech.. but actually is hella helpful.

[GravelBen]

 DarkCrystal GTB said:

 

Unfortunately I've had my Rev D tuned so I don't remember exactly but I do remember it boosting up to 1 bar on primary and 1.1 spiking to 1.2 bar on secondary.

Thats pretty much what mine is doing...

1 bar = 14.7psi from memory so yours is a bit on the low side. But IIRC yours is an auto? Which may run lower boost than a manual as part of the EJ206 detuning-to-protect-slushbox.

I have a boost gauge on the way for mine so it will be interesting to see what its doing.

[Cloud]

My 99 BE5 runs 10psi on primary, 14-15psi secondary

[Guest]

Mine is tiptronic / auto....

Having a better look at it this morning, i boosted on first turbo to 14psi, then 2nd turbo looks like its getting to maybe 13psi and falls off when she reaches about 6200rpm - is that normal??

[funkytown]

 DarkCrystal GTB said:

Mine is tiptronic / auto....

Having a better look at it this morning, i boosted on first turbo to 14psi, then 2nd turbo looks like its getting to maybe 13psi and falls off when she reaches about 6200rpm - is that normal??

i would say no.. it should be two stage.. 8-10psi on primary, then when the second comes online you will get to around 12-15 depending on auto/manual.

[pharnos]

Here are a couple of datalogging screenshots from a 1999 Subaru Legacy BE5 auto. It was quite a cold night. We're looking at logging the same for a 2002 Subaru Legacy BH5 manual (rev D) - will put up the results as soon as we get it done.

Tiptronic was just in auto mode.

You can see it boosts to about 11-11.5psi on the primary, drops to 7.5 on the switch, then spikes to 15psi on the secondary before flattening out to about 12-13psi

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links to pics here too:

http://pharnos.orconhosting.net.nz/subarulogs/99-be5-auto1-nightcold.JPG

http://pharnos.orconhosting.net.nz/subarulogs/99-be5-auto2-nightcold.JPG

[Guest]

Dam!! thats good info.... be great to see the Rev D 2002 model too....

After a bit of research on the net, it sounds like around 14psi on primary turbo is about normal on the Rev D.. but should be boosting to around 15.5/16.0psi once on secondary... my primary is boosting to approx 14psi, so that's all good... when secondary kicks in she's only boosting at 13psi. Now, i know this is not a vacuum leak or i'd get low boost on both turbo's. But i did come across a bloody good sequntial turbo thread that addresses low boost on the secondary - not subaru related but hey.... http://www.nopistons.com/forums/topic/8134-sequential-turbo-troubleshooting/

Basically talks about boost solinoids, clogged cats...

Main problem i have is there are no codes registering... so it a matter of trying parts out... I don't think the cats are clogged as she don't smell like a rotten egg... i have no idea where the boost solanoid is to try that out either - help?

[pharnos]

Ok, got a little bit of logging from an 02 BH5 Rev D (manual, completely standard) - the auto above has an exhaust, just muffler.

got about 10psi on the primary, dropping to 7psi on the switch to secondary then 13.5psi before changing to 2nd gear where the secondary boosted 13.5-14.5psi up until 6500rpm then it steadily dropped to 10psi around 7000rpm, then in 3rd it's at around 14.5psi until around 6300rpm then it drops to 13psi by 6800rpm.

hopefully that's some handy information

links to actual images:

http://pharnos.orconhosting.net.nz/subarulogs/02-bh5-manual1-nightcold.JPG

http://pharnos.orconhosting.net.nz/subarulogs/02-bh5-manual2-nightcold.JPG

[EJ20T]

mine makes about 14psi on the primary, this is completely normal, and a peak of around 14 is normal on the secondary, i think the aus market cars used to run about 16 on both, but that was to make up for the reduced timing for aus fuel and conditions

[EJ20T]

the above car is very slow to make boost on the primary, in 5th i make 14psi by 2100 rpm

[pharnos]

will try some 3rd gear runs (40kph up) and some 5th gear runs (80kph up) and post up the data logs

mind the above logs were not launching the car from standstill, they were squeezing through light accel in 1st

but yeah, interesting that the primary only shows 10psi ... maybe cos in 1st?