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

TT running VF33/VF32 combos with the supporting mods/ tune can put out 185Kw ATW. The VF31 (BB) in your car has greater potential than the VF33 (sleeve)just by swapping the turbine housing from its retrictive P11 (10.5) to a P14 from VF25 or P16 from earlier primary turbos (generate PE1016F) This would get you close or past 200Kw ATW in sequential mode. Regarding the TD04s they can be set up to run seq or para. With just a TD04 as primary turbo would genarate 130+ Kw ATW pretransion and 200+Kw ATW. I would suggest to do only the primary first to get the feel and response of these turbos, as they are not BB. The TD04 to use would one with 15G or 16T comp wheel. The primary turbine housing to use is a P11 (10.5) or P12 with these you can always exhaust titrate up to a TD04L turbine wheel.

Is the car exhaust system modified? What is the reason to change from seq--->para?

I am presently running TD04-16Ts What is your power output at present? Manual or Auto? What other additional modification does your car have to support going to 200Kw+?

The TT turbine housings are able to accept TD04,TD04L and inducer clipped TD04H turbine wheels and the RHF4 and TD04s share the same size 73mm C clamp They can be set as straight bolt ups for sequential or parallel. To run parallel you replace the ECV with adapter pipe with a primary turbo flange.(as the smallest secondary turbine A/R is P16 which is a bit too large to run parallel)

You certainly can run parallel twin TD04 hybrids in a 2.0L. These can be max out to a exhaust clipped inducer TD04H-19T using existing TT primary P10.5 --> P14 exhaust housings.

This may help http://www.overl0ad.com/LegacyFiles/Gen%20III%20-%201998%20-%202003.zip Engine Section 3 ---> Engine diagnostics --> Part 5 ECM

Yes "straight swap"

I can see your point. The primary turbo is worked the hardest of the two turbos. Yes it is possible to swap out matched CHRAs --> " even out the wear" However more cost effective and practical to just repair/replace the turbo when it fails.

Depends on the turbo set you have in your car? The Secondary turbo will always have the greater flow of the two turbos.Therefore you can always call it the "biggest". Examples 1. The VF13 and VF14 have the same P16 turbine housing, but the wheel set comp/turbine are a different size. The ones in the VF14 are much larger than the VF13.Thus the flow is adjusted by the wheel set. 2. The VF25 and VF27 have the same size wheel sets but the turbine housings are different P12 for the VF25 and P18 for the VF27. Thus the flow is adjusted by the turbine A/R or P This adjustment by turbine A/R also applies to VF26/VF27,VF31/VF32,(VF16/VF17?),VF18/19,VF20/VF21 combos. 3.The true size difference and flow belongs to the VF33/VF32 combo The VF33 has a smaller comp wheel and turbine A/R or P than the VF32 In right-hand drive cars the 2nd turbos is on the drivers side.

This is a direct swap. Just plug the line to the 2nd turbo actuator as you will not need it. The VF18 has got a larger exhaust wastegate port and higher pressure set actuator

If your secondary turbo is not a VF27 and I suspect it is either a VF19 (MT) or VF21 (AT). Then changing to a VF32 would be a significant power upgrade. If somehow it is a VF27 leave it alone as they have similar power ratings.

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What was your original primary turbo?

All secondary turbos are BB The turbo you have is a VF14 with its own actuator. I have a spare VF14 CHRA if you need it (no cost). Which you can lock and load if you have to replace it.

To high flow and minor WG porting plus set actuator approx $150 . Major WG port and new flapper extra $25-$50

From the VF33 you just need the turbine housing and the wastegate actuator. The turbine housing will need to be scrolled out or high flowed to take the larger TD04L wheel. Once that is done put the TD04L CHRA onto it and orientate the the original position as the VF33 was in . Install the actuator. Have the wastegate ported within tolerance of the existing flapper or ideally a larger porting with new bigger flapper

No will not work as the VF33 is a thrust/2sleeve bearing turbo therefore has no virtual A/R like a BB does and it also has a smaller compressor wheel therefore less flow. Upgrade with TD04 CHRA on the VF33 turbine housing this will match with the bigger VF33 60mm compressor Inducer.

Should be available at most Auto supply stores:NULON Worn Engine Treatment

It may be simpler to prime the turbo with some Nulon worn engine treatment via the bango bolt you have removed. Then put the rest in the engine oil and give it a good run..Will coat the turbo gallery if that is the problem.

Essentially you are making the turbo more efficient (greater flow at the same boost level) An example of this is with the VF25/26/27 these all run the same size compressor wheel/turbine wheel. At the same PR VF25 flows 370 CFM, VF26 flows 390 CFM and the VF27 flows 400 CFM and the only difference between them is the A/R. 12.14 and 18 respectively. The increasing A/R pushes the hook on the compressor wheel map to the right --> into a more efficient area ie 77%-->85%. The VF31 and VF32 share the same size wheels with A/Rs of 11 and 18. The VF32 has similar flow to the VF27. Therefore one could speculate that changing the A/R of the VF31 from 11 -->16, the flow change could be 365 --> 395 CFM approx 8% improvement in efficiency.

The VF31 is on a very restrictive P11 (A/R 11) turbine housing.This would be OK if it was a thrust/sleeve bearing turbo like the VF33 with P11. This is a BB turbo so it has smaller virtual A/R.That is to say if you put it on a P16 housing, it will spool as fast as thrust/sleeve bearing turbo on P14 housing.Thus the P16 extends the VF31 capability. P16 housings are on all primary turbos pre VF25/26 ie VF13/16/18/20 It should be a direct swap that you can do yourself. No balancing required. Some of the older turbos ie VF13 have slightly deeper collar seat in the turbine housing.Therefore you may require a heat shield spacer 2mm (heat shield with the centre cut out) to seat a later turbo CHRA. (the turbine wheel will sit too deep in the housing otherwise) Remember you do have an auto so you will note a degree of initial lag / throttle response with the P16 housing.

This would be an excellent upgrade. Alternatively you could go for VF32 as secondary and if you can get a VF31 swap the turbine housing from your VF18 onto it. This will give the VF31 extended performance --> PE1016F. PS have the primary turbo wastegate ported within tolerance of the existing flapper. (extra 2-3mm)

Subaru reached a twin turbo zenith with the VF25,VF26 and VF27 turbos. These turbos all have the same size compressor/turbine wheels. Primary turbos VF25 and VF26 both thrust/2sleeve bearing turbos with A/Rs of 12 and 14 respectively. The VF25 was on the auto GTB and the VF26 on the manual. Prior to this all primary turbos were BB on A/R 16 housings, however to get the spool rate the A/Rs had to be dropped. Secondary VF27 is a BB turbo on A/R of 18 housing. Another distinction these turbos had was the 8 blade performance turbine wheels instead of the standard 9 blade for reduced weight (improve spool) and better exhaust flow. Following on from these turbos were the VF31 and VF32 (both have the same size compressor /9 blade turbine wheel)with a larger compressor wheel exducer than VF25/26/27. The VF31 primary turbo went back to a BB on A/R 11 turbine. The small A/R housing really reduced its potential, but gave it fantastic spool. Power Enterprise (PE) noted this and put the VF31 on an original primary turbine housing A/R 16 to generate the PE1016F turbo. The secondary VF32 turbo is BB on A/R 18 housing.PE rebadged the VF32 as the PE1018F to market as a set with PE1016F for earlier twin turbos. Comparing turbos: Primary PE1016F>VF26>VF25>VF31>VF33 Secondary PE1018F=VF32=VF27 approx equal, the VF27 may have a slight edge at higher boost.

High flow your existing turbo with 19T compressor wheel matched to a TD04HL turbine wheel (if possible get the 11 blade performance turbine wheel instead of the standard 12 blade) to generate a TD04HL-19T. A nice responsive turbo with flow just short of a small wheeled TD05H-16G