VNT turbo in an A3/B4?

I was wondering if anyone with a 1Z or AHU engine has converted their car to a GT-VNT15 or GT-VNT17 turbo?

Any thoughts on doing this? I know that the wastegate actuator does not work well to try to modulate the boost on a VNT turbo but is there a way to get this to work without doing anything major to the engine (new ECU, etc)?

TIA.

Jeff at Rocketchips suggests that from an ECU programming point of view, it can be done. What is less clear is the actual hardwiring of the N75 and other control stuff to deal with the vacuum-actuated VNT mechanism versus the pressure-actuated wastegate.

I'm interested in finding more about this as well.

Peter, diesel des has done this with very good success give him an e-mail (desauld@hotmail.com) /images/graemlins/rolleyes.gif

Hi Peter,

Glad you asked, this has been a side project of mine for the past year. This is the 68 pin euro AFN110 (immo1). I have this conversion for either wastegated or vnt versions. It also comes in a version that runs the A4 maf - very snappy response for an A3.

I have several folks testing this now, and will release it soon. btw, this is big injector firmware with 18.5 psi boost, using a boostvalve with the N75 for smooth wot power.

I can also say the bad news is every car I've tested this in, the clutch slipped I just installed a new engine and vr6 clutch in my friends 96 passat last night and will test some more tonight.

The 68 pin AFN110 using the vnt15 and A4 maf with .205 injectors will be a very powerful upgrade. Other good news is there are automatic maps too, if you want to be the 1st automatic 96 passat. You can also load 4 separate tunings as well (ie, oem, stage 1, 2, and 3) However, you can't mix 1Z/AHU and AFN tunings - different firmware.

I'll probably add a webpage to my site in the next few weeks, I'll keep you posted.

I'll convert a wastegated A3 to vnt15 soon and have the necessary parts list and exhaust plate/adaptor for this too. FMIC will follow . . .

Regards,
Jeff

Jeff, that sounds intriguing. At a recent Dyno Day here in the SFBA, it was proven, again, that the earlier non-VNT cars don't make as much HP because of the standard turbo. That's why I made this thread.

Something you posted that sounds interesting: one chip with multiple programs, can these programs be changed "on the fly"? I'd love to have stock and Stage III at the minimum.

Hi,

All 68 pin A3/B4 ecu's can be made with dual maps and hard switch that you can switch on the fly. I can do this, just pm me for more details.

Jeff

I've done similar conversion in my by-passed AGR engine.

It required exchanging whole charge pressure regulation system and ECU re-programming. In case of 1Z engine exchanging ECU may be needed (perhaps AFN ECU).

Here is the link to my post describing whole procedure:
GT15 -> VNT15 conversion

After converting to VNT15, conversion to VNT17 is very simple - you just have to put an adapter on outlet pipe.

[ QUOTE ]
I can also say the bad news is every car I've tested this in, the clutch slipped /images/graemlins/smile.gif I just installed a new engine and vr6 clutch in my friends 96 passat last night and will test some more tonight.

[/ QUOTE ] I have a Sachs Power Clutch waiting to be installed so I think I have that covered.

How did the testing on the B4 go?

While I'm not the addressed, I have had a Sachs Power Clutch in my B4 since last summer, and I can say that for my setup, I have never had any slip whatsoever. Pedal feel, effort and modulation have not changed perceptibly.

I am glad to see this is getting revisited. The 110 HP A3 TDIs were supposed to have the VNT turbos, which helped with the HP and torque. I am curious about the program to run the A4 MAF. Is the design different which allows more power to be made? The A4 MAF is much more unreliable than the A3 MAF, so unless some startlingly results were shown for this combo, I don't think I would even consider this. I would also like to see some dyno runs of the A3/B4 cars that have had the VNT turbo installed. This would be cool if it substantially raised power and gave better driveability.

Hi,

I'm considering a K04-001 turbo using an adapter plate to mate it to the exhaust manifold. It has been suggested that the K04, mated to a ceramicoated exhaust manifold, will flow more air at 19-psi than my GT15 and reduce IATs... netting a gain of about 15-20 hp. I'm always skeptical. But my stock turbo can't last forever. /images/graemlins/wink.gif I'd rather replace it BEFORE pieces of it wind up inside the engine. /images/graemlins/laugh.gif

What do you think of the power potential of these upgrades?

Comments?

Scott

As has been posted many times, in and of itself, a turbo swap with a bigger unit and running more boost will result in a negligable increase in HP in a Diesel if it's not accompanied by an increase in fuelling. So, I'm left questioning the claims from your source of a 15-20 HP gain from a turbo change alone, but I would say, "no."

Neglecting the effects of the intercooler, a reduction of IAT at a constant boost pressure can only occur if there is an increase in the compressor efficiency at that particular operating point. While this is not clear-cut, I do recall seeing a map of a K03 and it seems to be near it's airflow limits at 19 PSI boost and redline on a TDI, with efficiency only in the 60-65% range. A larger, higher flow turbo will certainly be more efficient in this area (near redline), but the location of the efficiency island is not affected significantly and the peak efficiency also doesn't change much (between 72-74%). I assume most of your time is not spent at max load and redline, so the real-world benefits of a bigger turbo will not be frequently noticeable.

Also bear in mind that the K04 would be from a gasser application, and that means a number of things: trims and A/R ratios that are optimized for higher flow / lower boost, and higher energy exhaust (higher EGT in a gasser). Therefore the A/R will tend to be a higher number, which is good to make more top-end power, but more laggy on the bottom-end.

Also, unless you're getting a hybrid turbo, the centre section of the K04, like most gasser turbos, would be water-cooled, which means necessitating plumbing a coolant supply- and return line.

One other thing: a coated exhaust will do NOTHING directly for IAT, nor for airflow on the compressor side. That's logical.

Where it will help is in reducing the heat rejection from the manifold, and that has a number of benefits, including lower underhood temps. A higher turbine inlet temp will help spool-up (although the magnitude of the gain nobody really knows). A higher initial temperature at the turbine inlet and greater temperature delta across the turbine means increased efficiency (thermodynamics 101), and that directly affects manifold backpressure (increased total efficiency = reduced backpressure) but have no effect on the compressor side.

Conclusion: Good thing to do, but don't be convinced that it will be responsible for a significant power gain.

As a side note, upsolute has stated that if they made a FMIC for the A3/B4 they would also make a stage III kit. Without a FMIC they refuse to make the kit. There's a Group by for FMICs for the A3/B4 btw

/images/graemlins/wink.gif

[ QUOTE ]
As has been posted many times, in and of itself, a turbo swap with a bigger unit and running more boost will result in a negligable increase in HP in a Diesel if it's not accompanied by an increase in fuelling. So, I'm left questioning the claims from your source of a 15-20 HP gain from a turbo change alone, but I would say, "no."


[/ QUOTE ]
I don't pretend to make claims of making 15-20 HP from just a turbo change but the fact remains that as the revs rise the boost drops off past 3800 RPMs. I see it on my boost guage. At the Dyno Day I mentioned before, stock A4 TDI's were making almost as much HP as my chipped or bogstomper's PP520 injectored A3 Jettas. I believe that it is because the VNT turbo is not dropping off boost at high revs like our wastegated turbos and no amount of additional fuel will help this situation.

I'm actually considering a hybrid K03/K04 turbo instead of the VNT option because of the added complexity of the installation (that assumes that the compressor section of the K04 is similar to the compressor section of the K03 that is in my car).

Hi,

Thanks for the reply. Like I said, I'm always a skeptic. A larger turbo is something I won't consider unless I also install injectors that are larger than my current .205s. Even then, it's tough to justify spending $800 (turbo) for a less than breath-taking improvement. /images/graemlins/wink.gif

Regarding the exhaust manifold, your explanation is about how it was explained to me. I used the term IAT although I was aware the temp at the IAT sensor would be unchanged. I was told the new manifold would keep some heat off the intake manifold, thereby reducing the actual IAT.

Sorry to highjack the thread, Peter. But this seemed like a good place to drop my question instead of starting a separate A3/turbo upgrade thread. I hope I didn't take it too far off topic.

Take Care,

Scott

Scott, no problem as that answered another question I had about our cars. Saved me the trouble of posting a new thread /images/graemlins/smile.gif

Along those lines I was thinking of getting some of that DIY ceramic coating stuff and coating my own exhaust manifold (when the turbo is out getting replaced or upgraded).

Peter tell me why your boost is droping 0ff at 3800rpm when i can get 5000 in 4th and 4600rpm in 5th.I take it you have a chip and dawes + injectors ex,if your set up is right this should not happen this is why i use the dawes cut out eliminator not as to trick the map more because the restrictor keeps the wastegate closed . after putting on the dawes boost valve some punch is lost because the wastgate is opening ,Nowing that your car is capable cr you could weld it closed or a better heaver actuator

It is the exhaust (turbine) side that is the first restrictive piece of the gt15 turbo in the A3s and B4s.

The turbine inlet A/R is only 0.35 where as the VNT-15 has A/R 0.65 when the vanes are most open.

Exhaust manifold pressure (EMP) is up to 3 bar or 44 psi with the gt15 in contrast to 1.5 bar with the VNT-15 with the same power level. This EMP is working against the movement of the pistons and also makes it harder for the exhaust gases to exit the cylinder.

There is no easy way of changing the A/R number since there is no exchange piece available that has the same flanges for the downpipe and manifold. Some reduction (3 -> 2 bar)in EMP can be gained by changing the center piece of the turbo to a larger (gt20) piece and machining the turbine outlet (in the housing) from 33mm to 40 mm. With adequate fueling (12mm head and pp502) boost is still at least 1 bar at 2000 rpm, even with 52mm compressor wheel.

Other turbine housings with different flange configurations and larger A/R numbers are available, but it means that the position of the whole turbo is shifted and all plumbing is more or less 'in the wrong place'.

Apsalutely bang on,its the same with head flow and cam. sorry I sometimes forget i've changed the turbo and think everyone has the same.

[ QUOTE ]
It is the exhaust (turbine) side that is the first restrictive piece of the gt15 turbo in the A3s and B4s.

The turbine inlet A/R is only 0.35 where as the VNT-15 has A/R 0.65 when the vanes are most open.

[/ QUOTE ]

Correct, and excellent point! However, it must be noted that increasing the turbine A/R on a fixed geometry turbo like a K03/K04 is, will result in laggy low-end performance and low boost in that operating range. One of the beauties of the VNT is that is allows for the response of a low effective A/R turbine at the low-end and also the free-flowing nature of a high effective A/R at the top-end, esssentially giving you the best of both worlds.

With a hybrid K03/K04, you still have to put up with, as TDIFreak noted, with restrictiveness of a puny housing (even smaller than the GT15) and a low A/R ratio for good spool-up at the low-end.

To close the HP differential between the newer VNT-equipped TDIs to that of the older wastegated TDIs, you really need to open up the restriction on the turbine side, and you can only achieve that with minimal compromise in spool-up response with a VNT...

[ QUOTE ]
...it must be noted that increasing the turbine A/R on a fixed geometry turbo like a K03/K04 is, will result in laggy low-end performance and low boost in that operating range. One of the beauties of the VNT is that is allows for the response of a low effective A/R turbine at the low-end and also the free-flowing nature of a high effective A/R at the top-end, esssentially giving you the best of both worlds.

[/ QUOTE ]

And that's the reason for this thread!!! I WANT THE BOOST RESPONSE THAT ONLY THE VNT TURBOS CAN GIVE US! I've said it before, I would sacrifice some low-end boost for a bit more top-end boost but I'd prefer having my cake and eating it, too.

Thanks for the responses so far.

I am most interested to hear how the new clutch holds up.

I have said this before my other half has an A6 2.5 V6 tdi quatro sport with 155hp and a vnt20 standard no mods, this car feels like my a3 golf before i chiped it lagy and untill you chip or put some injectors in, to put the boost up compared to my golf now with a t25 wastegated turbo /images/graemlins/grin.gif