219 replies to this topic

[zanzarah]

The ZS Seq Controller will allow you to move transition point as high as 5000rpm and the return point as low as approx 3000-3200 rpm.
These are the recommended set ups
Street - Sequential = 4200~4400, Return point 3300~3400
Winding - Sequential = 4600~4800, Return point 3300~3400
Highway - Sequential = 4000, Return point 3400~3600.
Regarding pre-spool (earlier than initiated by the ECU) there are two methods
1.Adjusting the pretension on the ECV Actuator rod so that as the exhaust back pressure rises the valve will be forced open and leak exhaust to the secondary turbo.
2.Titrate some primary boost to hose No 5 the positive boost port of the ECV actuator this will cause the valve to open earlier and leak exhaust. (wastegate effect)
Since you will be running mostly primary turbo I would recommend the Fujitsubo headers, as the cross pipe is set up to reduce exhaust pulse clash.

[twinturbosubaru]

The prespool is tricky.
When the boost starts rising the ECV is opened using this pressure, this starts spooling the secondary, when the pressure coming from thje secondary matches the pressure coming from the primary side (use the differential pressure sensor - aka code 66) the ECV is opened fully by the vacuum side of the actuator, this then causes a drop in pressure on the primary side as the secondary goes into full swing, this is why you feel the VOD, it's the pressure drop from the primary before the secondary can really kick in.

Issues I see from 8 years of owning a TT are mostly related to boost pressure.
The problem is that it's all controlled via the primary, even on early TT's with the wastegate on the secondary, put simply, the more boost you run the bigger the VOD unless you can match the turbos very well.
Late AUDM B4's were about the best match, however I am really keen to see what happens here.
I think you have approached this in a very interesting way, with a bigger exhaust wheel on the primary but smaller housing you may just achieve something, I personally reckon the exhaust housing on the secondary needs to be smaller, that way it might not come on boost quite as quickly when the secondary kicks in, but the drop in pressure on the primary side will be better and should see a marked improvement on the VOD.

I for one think the VOD is over-rated, if you are driving the car hard who gives a crap, once it's revving it's nuts off under full load you never see the VOD again anyway, it's only when you slow down again you hit it again

Regards
Paul

[BigWillieStyles]

I for one think the VOD is over-rated, if you are driving the car hard who gives a crap, once it's revving it's nuts off under full load you never see the VOD again anyway, it's only when you slow down again you hit it again

I dont really notice VOD that much, its only when you change into that it annoys me.

I have honestly never looked to see how these other systems work. Do have any info or links on how they differ that you would be keen to share? I am interested in having a squiz.
Ta

Im not really a tech-head but I had an FD rx7 as my last car. The rx7 is completely different, and the two turbos share the same downpipe. Some owners comment on a small hiccup between the turbos, but its no VOD, and can easily be tuned out. I never felt it personally.

The ZS Seq Controller will allow you to move transition point as high as 5000rpm and the return point as low as approx 3000-3200 rpm.
These are the recommended set ups
Street - Sequential = 4200~4400, Return point 3300~3400
Winding - Sequential = 4600~4800, Return point 3300~3400
Highway - Sequential = 4000, Return point 3400~3600.
Regarding pre-spool (earlier than initiated by the ECU) there are two methods
1.Adjusting the pretension on the ECV Actuator rod so that as the exhaust back pressure rises the valve will be forced open and leak exhaust to the secondary turbo.
2.Titrate some primary boost to hose No 5 the positive boost port of the ECV actuator this will cause the valve to open earlier and leak exhaust. (wastegate effect)
Since you will be running mostly primary turbo I would recommend the Fujitsubo headers, as the cross pipe is set up to reduce exhaust pulse clash.

Nice post, do you have a sequential controller? Im curious about how good they are.

[natho]

i believe the 2JZ has the wastegate of the primary turbo spooling the secondary, but the 'ECV' is in the secondary's dump pipe, rather than before it. (see http://www.jzs147.co...3f85c071579c5ba). i've had lengthly discussions with billsy about this and ideas of improving subaru's system. i couldn't be bothered and put on a VF29 instead (it'll be tuned next week).

at the end of the day though, the best way to get the most out of the sequential system is to have more exhaust gas to play with, i.e. a larger engine. i bet those TD04 hybrids would work a lot better on a 2.2 or 2.5. billsy maxxed out the flow of ported vf25/vf26's with his 2.2 (with extensive head work and cams), it made no more peak power than the 2.0 due to lack of flow from the turbos, but the transition was not noticeable at all.

i considered the td04 hybrid idea also, as i wanted more of a midrange 'punch' rather than waiting till about 5000rpm for full boost with both turbos. im sure the larger TD04 will provide more flow and better power pre-transition. however i was worried that going larger would just make the transition worse. when my TT was tuned, the VOD was removed by reducing boost a little on the primary - the car actually made about 9kw less pre-transition after the tune, but it was completely linear. i can't see the TD04 being so much more efficient that it will maintain power in the changeover as well as the stock turbo. no doubt it will be far better pre and post transition, but how long will the transition take? i'd be very interested to see, i just wasn't willing to try it and risk being unhappy after all that effort.

[zanzarah]

Billsy VF26/VF27 combo result 107Kw->dropped to 90Kw trans->229Kw ATW in 3rd gear @ 19psi. (ported ECV)

[BigWillieStyles]

i considered the td04 hybrid idea also, as i wanted more of a midrange 'punch' rather than waiting till about 5000rpm for full boost with both turbos. im sure the larger TD04 will provide more flow and better power pre-transition. however i was worried that going larger would just make the transition worse. when my TT was tuned, the VOD was removed by reducing boost a little on the primary - the car actually made about 9kw less pre-transition after the tune, but it was completely linear. i can't see the TD04 being so much more efficient that it will maintain power in the changeover as well as the stock turbo. no doubt it will be far better pre and post transition, but how long will the transition take? i'd be very interested to see, i just wasn't willing to try it and risk being unhappy after all that effort.

I never thought about lowering the boost on the primary and raising it on the secondary to get a linear power curve what a simple way to do it.

There are a number of things you could do to play around with the system. I reckon a 2.5 with forged internals, then running the a pair of TD04 turbos in parallel would be pretty fun. There is car on clubsub forums running a similar setup with a pair of VF22s and making about 240kwatw

[acres]

Guys just want to say thanks the positive attitude towards this has been fantastic so far.
Zanzarah - great info on the zs controller, I may have to invest in one of these. Regarding the pre-spool I wasn't keen on adjusting the rod to have the gate permanently open slightly however I have operated the positive side of the ecv actuator using boost pressure from the primary but it really needs an aftermarket boost controller or the duty cycle of the oem solenoids tweaked for this to work effectively.
Totally agree with comments made on the drop in primary boost causing the biggest effects on vod. This is why I am keen on running a dual core FMIC setup whereby the piping will only merge just before entering the TB. This way the I/C valve and differential pressure sensor can be placed downstream of the intercooler. I would think that this should allow the secondary a bit more time to build up boost before changeover.
The vf14 has the smallest available turbine housing for a secondary. Initially I want to be able to use the oem ecv however if I end up using an aftermarket ecv than I may replace the housing with another vf25.
Natho wouldn't lowering primary boost just reduce the sensation of vod as opposed to eliminating it? Since there is less pressure to be lost in the first place. I'm also assuming/hoping that the extra flow combined with extra rpm should produce enough extra exhaust gas to prevent the secondary from being slow to come online. This is also why I switched out the turbine wheels to standard td04 wheels with the smaller tip height. This was a recommendation given to me by another member on ozlib. This member has actually been experimenting with similar hybrids for a while now and he found a great improvement at changeover with using the smaller wheels. So props to Ashley(?) for saving me from having to discover that one for myself.
Big Willie, I believe that's the Prova B4 your referring to. Built in japan and I think someone tried to export it here at one stage.

[B4TT]

I will be keeping an eye on this, let us know how you go and then give a simplified version of it all to someone (me) who really doesn't know much about Turbos.

[Hypnotic]

This is a great read, very interested to see the progress

[natho]

Natho wouldn't lowering primary boost just reduce the sensation of vod as opposed to eliminating it? Since there is less pressure to be lost in the first place. I'm also assuming/hoping that the extra flow combined with extra rpm should produce enough extra exhaust gas to prevent the secondary from being slow to come online. This is also why I switched out the turbine wheels to standard td04 wheels with the smaller tip height. This was a recommendation given to me by another member on ozlib. This member has actually been experimenting with similar hybrids for a while now and he found a great improvement at changeover with using the smaller wheels. So props to Ashley(?) for saving me from having to discover that one for myself.

lowering boost on mine eliminated the VOD entirely, at l least the VOD in the perspective of revving it right out. it just seems to build more power at 5000rpm, there was no drop at 4000 like standard. the only VOD mine had with the ECUTEK2 was when you changed gear at the wrong time. this is what annoyed me most about the TT, and why I ultimately converted to single.

[acres]

Just had a look throught that link for the schematic's of the supra system and I think that the biggest problem with implementing a system like that would be packaging constraints. There is not a great deal of room in our engine bays so it would probably be a very tight squeeze with that exhaust setup. Perhaps that is why subaru didn't develop a system like this. The I/C valve interests me though so I might try and do a bit of research into how the supra one works. It looks like it has some sort of by-pass.

Reattched the intake manifold last night and have taken a few pics to show how tight a fit the intake pipe is. Hardly a mm to spare.

[Soop]

That intake pipe is great.

[natho]

great work with that intake pipe. looking forward to seeing the results of this!

[BigWillieStyles]

Looking good!

Thought this was interesting, have a look at allpaw4's dyno graph. He has now gone to single, but look at his TT below.

[acres]

Thanks guys. For the next bit of welding I attempt though I will definately be investing in a decent mig or tig with gas and some sort of metal cut off saw. I just used a hacksaw, angle grinder and a stick/arc welder. Was seriously gay. The flux coating on the electrodes kept getting into the welds causing alot of gaps and pinholes so I had to keep grinding it back and re-welding.

That is a very, very smooth TT curve. Nice

[natho]

thats very similar to how mine was after sean tuned it

bear in mind he's got more power/torque everywhere because his is now a twin scroll. i wish my VF29 was that good... i don't think it'll be any better than the TT until 3500 revs. will know once it's tuned.

[Alex]

I would take dynographs of other people's cars with a grain of salt.

The only graphs you should be looking at is your own, going back to the same, consistent dyno.

Only then, you can compare your own graphs with yourself, and then gauge true gains.

Comparing one person's graphs from SA, to another person's in QLD is like pissing in the wind. It's messy, and achieves nothing.



There are no constants to compare against.

[acres]

I don't think anybody was comparing more just appreciating the smooth line. Totally agree with what you said though you can only compare your own graphs to one another from the same dyno. And even then it is only so accurate

[Soop]

That is a very decent curve.

Although I notice there's no torque curve there?
It's fruitless looking at a power curve. Torque is where its at.

[Alex]

I'm sceptical of that curve