Replace primary with what?

[RSB]

 gtb36']

[quote name='RSB said:

VF26 is best factory primary.

VF25=Auto, VF26=Manual.

Go VF26. VF26>VF18

The VF13 is from a BD/G5A Legacy (that is, the first of the second generation legacys) The VF26 would be a substantial upgrade.

Also, next time I do any turbo work, without shadow of a doubt I'm going single.

/quote]

nar that not true

my 2000gtb is Manual and WAS running vf25

That dosent mean that it came from the factory with a VF25.

[RSB]

 ReubenH said:

VF31 (or is it 32, i can never remember) are smaller primary's, and are also a BE/BH turbo, i don't know anything obout these suckers other than i've seen one on a face lift BE.

Correct. Came on the e-tunes i think. Fin design gives more progressive boost than say a VF18. Basically these are a VF32 clocked differently and with a smaller turbine housing.

[gtb36]

 webup said:

REally so a VF25 is not the way to go for me from VF13??

vf 25 and 26 are slow as we play around with my gtb and find the the vf20 was that bit faster and better..but i wont go back to a vf13 no..

iam not saying vf25-26 are no good but it did seem to bog down a it

[gtb36]

 ReubenH said:

VF13 is an early early BG Primary, and they are notorious for blowing. If this was on a BH, someone cut corners to get that car fixed at some stage...

VF26's are the biggest primary you can get, as far as i know. They are usually said to be the best, and it's likely the factory turbo for your BH (and so the ECU tune is likely tuned for it as well), i recommend getting one of those. The point on them being slow to spool is silly as far as i'm concerned, they are still tiny little things compared to any single turbo, and should spool up plenty quick. And as i stated, it's probably the factory turbo for your car.

VF31 (or is it 32, i can never remember) are smaller primary's, and are also a BE/BH turbo, i don't know anything obout these suckers other than i've seen one on a face lift BE.

vf31 is a primary as well

have you tryed a vf 25-26 and vf20 man

as i have and the vf25 IS SLOWER AND GET BOG DOWN SOME TIMES

[gtb36]

 GravelBen said:

32 is BE/BH secondary, 31 and 33 were both used as primaries AFAIK (my rev-d BH E-tune has 33 primary 32 secondary). Just wondering what the differences actually are.

If your have vf33 as well the black pipe undor the manafold is bigger then the 1998-2001 gtb as the vf33 inlet it way bigger then on vf13 upto vf31

[telemekas]

The VF25 and VF26 are the first primary non-BB turbos to be used in the TT.

Prior to these all primary turbos were BB with P16 turbine housings.

To improve spool up due to the higher torque friction of the non-BB, the A/R or P was reduced the VF25-P12 and the VF26-P14.To aid spool up,both turbos are fitted with the 8 blade performance turbine wheel (standard is 9).This reduced weight, improved exhaust flow and total exhaust run out

These were then paired with the secondary BB-VF27-P18

All three turbos run the same wheel sets with the largest superback compressor wheel (37/48mm-6/6 blade) of all the TT turbos.

The VF25 and VF26 turbos are rebuildable. However it is more cost effective to directly replace them or swap the BB CHRA from a VF27.Thus generate a more responsive BB primary turbo.

The next primary turbo to appear was the VF31 this went back to BB with a P11 turbine housing (superspool) and coupled with the VF32 a BB on P18 housing. Both turbos run the same wheel sets. Flatback 36.5/52.5mm 10 blade compressor wheel, with standard 9 blade turbine wheel.

The last primary incarnation was the non-BB VF33 with 35.4/47mm (6/6 blade) superback comp wheel and standard turbine wheel.This uses a P11 turbine housing and has a compressor cover with a 60mm (standard 46mm) inducer collar and 50mm (standard 36mm) exducer.This turbo was also paired with the VF32

[webup]

Job is done and car is nice i.e no whistling turbo.

Initial thoughts: Definite increase in VOD, really noticeable after the VF13 that was on there which seemed to boost right through and I never felt it drop off before the secondary came on.

Now with VF26 as primary boost is good but with the VOD the car feels less responsive and I can finally see what all the fuss with VOD was about.

Previously with the VF13 on there I was like 'what VOD mine has zero VOD'

Interesting exercise for someone with the time and means would be to try making their TT have a VF13 as I did and see if they like it.

Overall im very happy to not listen to the whistle anymore but if youre looking for driveability and performance I think the old setup was possibly better.

Many thanks to Richard the Subaru man you want to see if you're in Christchurch for his great job!

[telemekas]

The main problem is the preset transition point RPM 3900-4100.

Essentially those two turbos VF13 and VF26 spool at approx the same rate.

The small wheeled lower flowing VF13 reaches peak efficiency much earlier and consequently has less percentage drop off in flow during transition.The larger wheeled higher flowing VF26 peaks later and suffer a larger percentage fall off during transition.

The VF25 or better still VF31 would produce less transition fall off.

The VF26 can be made to feel like a VF13 if the RPM point is moved up to ie 4500 RPM? by using Sequential controller or by changing the CHRA to BB.

[ReubenH]

+1 for sequential controllers. If vod bothers you, they are an excellent investment. I thoroughly enjoyed mine while i had it.

BUT ONLY IF VOD BOTHERS YOU.

[webup]

How much are they?

[Hailz]

 telemekas said:

The VF25 or better still VF31 would produce less transition fall off.

Agree, I noticed a difference in VOD with the VF31 on mine - much better!

[EJ20T]

its totally a trade off, ive got the smaller VF31/33(not sure on wich) , VF32 combo on my d rev RSK, its great in town and has low vod levels, on the other hand my bro has a A rev manual GTB with the big turbo set, little unresponsive under 3k medium vod but a killer top end that is useable out to 7.5k

[EJ20T]

just checked and mine has the VF33 as the primary thought it strange as mine is one of the early rev d's