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VF Turbos what you need to know in laymans terms


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I have no idea about the later VF stuff above 37- on wrx so feel free to comment if you have real world exp.

Ive run VF22/23/28/36 in P18 and 20 housings so drawing most of this from personal real world exp. BIt of a mess but easiest way to blurt it out read and weep.

The common early single scroll turbos are like so from biggest to smallest roughly. BB VF22, BB 23, BB 34/ Journal 30, Journal VF35, BB 24/28/29.

The 24/28/29 are all pretty much identical not worth changing from one to the other.

A VF34 is the same as the VF36 the only difference is the housing P18 on the 34 vs P25 on the 36.

The spool difference between VF30 and 34 is night and day.

The single scroll housings go Ball bearing P20, BB P18/Journal P18 and Journal P15. No idea on late housings other than P25 is the VF36 BB twin scroll.

The Ball bearing chra will accept any other BB housing so you can put a VF22 into a P18 for example. Same applies to the P25 twin scroll housing so you can make a VF22P25. The journal and ball bearing housings do not swap over.

Running a VF36P18 and P20 back to back theres almost no difference when logged. Stick with the P18 if youre all about spool but the P20 wont hurt peak power and doubt you would ever notice the difference if a computer hardly sees it.

The VF30 P18 journal housings crack easily watch out if you are buying one secondhand that its not leaking severely.

You can clock any comp housing on a VF you just need to redrill holes thro the actuator bracket to mount it to the back of the comp housing.

The VF30/34/36 all have exactly the same compressor wheel which design lends itself well to restrictors and spool noticeably better than the early VF stuff found on the GC/GF STI chassis. They are more efficent at higher boost often -24psi where VF22 have a small hub on the compressor which tends to shed blades at 20psi-.

All VF run the same turbine which is the limiting factor the only way to get more is to clip the turbine. Steve Murch does a comp upgrade for these unsure on the turbine but guessing it gets steve treatment. Regardless its not going to make 300wkw but will get you a few extras kws for what it would cost to go a VF22 or the like. Overseas they throw Garrett compressors on them but its hardly worth it when the turbine cant keep up.

If you want to buy the best VF turbo with no budget get a VF34 or 36 in a P18 or 20 housing. On a 2.0L it will spool like crazy and going to the t/s housing will just cost more money for not much more up top. If youre all about the t/s or spending money then go for gold.

Stop getting hung up on dyno figures. Some cars will run a VF28 and net higher power than another running a VF22 at higher p/r its life its not fair. Reality is setups and even stock engines vary greatly and even tuned back to back by the same tuner Id put money on a noticeable difference. If you have a VF dont bother upgrading to another VF its likely not worth your while and may only see 5-10wkw where youre better of saving a few bob to upgrade other bits as you will likely be limited by your stock injectors before the VF hits its limit.

If you have a wrx non sti and you want a bit more power slap on a VF of some description it will only do good things providing you setup the boost on the dyno and make sure afr is within spec and you have no det.

Being a small turbo they turn into heaters really quick so a FMIC is a good idea.

Common dyno figures show 140-160wkw around 4k but dyno results are just that draw your own conclusions.

End of the day theyre all tiny turbos all -500cfm where a early TD05 off a V1/2 will give slightly more than a VF22 with similar spool. If you want to make somewhere between 200-240wkw and arent hung up on dyno figures stick with a VF they will do what you want. If you want a decent power hit you'll need something extra which means $ in injectors etc to keep up with your addiction.

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Good write up! Many thanks for the information. Could also be worth mentioning which are rebuild-able and upgrade-able? And is there any chance you could go over identification on exhaust housing and maybe even 2nd hand buying advice (e.g checking for cracks ect)

I can supply photos of td05 stuff I have 3 of them now haha

Edited by slystiguy
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  • 3 months later...
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I can't see anything in there I disagree with. People froth over the VF22 but at the end of the day it's not a magic turbo, the maths/compressor maps/physics don't lie, the turbine is only good for about 235wkw on a dyno that isn't set up to tell ego-inflating lies.

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I'd love to see back to back comparisons of twin vs single scroll; with and without avcs, with and without a tune. Say, 34 vs 36, or even something like that VF22/P25 or whatever it was that ADIKT had. A twin scroll conversion is an (inexplicably) appealing thing for a GC/GF if you are wanting to stay with factory kit, but may well be utterly pointless in terms of looking for better response.

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I struggle to see the appeal in t/s for VF other than nice noise and slightly more low/top. 1k- to do the conversion I think cost/benefit doesnt add up there. By going to VF36 in a p20 it spooled like a demon if I can find the logs of which Ive got a ****load and all by date so feck knows which is which now it would build 14psi or so by 3k in 3/4/5 on flat. Doesnt get a lot better than that without making it rather surgey. Pretty much no difference between 0% d/c vs 100% or p18 vs p20. EWG but still 20psi/3.5k is pretty average for any VF.

Adikts one wouldnt count it was murched no longer an ihi comp and turbine wouldve had a massage.

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 evowrx said:
I struggle to see the appeal in t/s for VF other than nice noise and slightly more low/top. 1k- to do the conversion I think cost/benefit doesnt add up there. By going to VF36 in a p20 it spooled like a demon if I can find the logs of which Ive got a ****load and all by date so feck knows which is which now it would build 14psi or so by 3k in 3/4/5 on flat. Doesnt get a lot better than that without making it rather surgey. Pretty much no difference between 0% d/c vs 100% or p18 vs p20. EWG but still 20psi/3.5k is pretty average for any VF.

Adikts one wouldnt count it was murched no longer an ihi comp and turbine wouldve had a massage.

Tbh people have thrown more money at worse ideas than a twin scroll conversion.

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 evowrx said:
I think I did manage to get a VF22 comp map out of somewhere but tis f all bigger its not like 16g vs 18g size. Your thoughts on VF30 vs 34 was night and day with response for similar power iirc?

Un-tuned, noticeable but not world-changing. On a relatively stock vehicle it's only in the order of a few hundred rpms in boost threshold.

Tuned it was a complete spool-demon. Pointlessly so, you could push it into surge very easily and in 6th with the slightest load it would be into boost.

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I can say from real experience there was bugger all (no?) difference between VF22 and VF23 on the same setup, there was about a 1kw difference so probably within margin of error tbh.

The 22 stays on boost better however and feels less responsive around town. The car feels slower in the real world but lap times disagree.

I have enjoyed my VF22, but I am quite excited to go bigger now. I am just wondering where it ends :/

Edited by Johnnynz
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See; I like my little VF28; comes on strong and oddly held quite well down the 1/4 mile, though I didn't really watch the boost gauge; I was watching the rev counter and listening for just in case something broke. Should have watched the boost gauge....

-It felt like it held well though.

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