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Sat Feb 07, 2015 1:52 pm

So you have a TDI... And you have an unlimited budget, unlimited skill, unlimited tools. What in the eyes of the TDI gurus opinion would be the best turbo? Let's keep this realistic in the sense of original transaxle, proper gearing and other upgrades. From all of my reading it is very obvious that there is a definitive limit to the amount of power the transaxle can take, even with all the proper upgrades.

So you have XXX torque that you are shooting for to keep that transmission alive, you want to keep EGT's down for hill climbing, and obviously want good driving characteristics... What turbo? Custom Manifold? Does 15/50 degree change your choice?

To stir the pot a little more, what is your ideal torque number under the reliability/drivability compromise?

Sat Feb 07, 2015 3:20 pm

VNT or Not?

Sat Feb 07, 2015 5:22 pm

Whatever is best!

I have seen builds that have VNT on an AHU and I have seen non VNT on an ALH. I guess that is part of the point of my question... What is best, in various people's opinions.

Sat Feb 07, 2015 6:42 pm

I suggest that you contact Andrew Libby - lots of posts on Samba - he is very knowledgeable WRT to turbos and good choices.

Sat Feb 07, 2015 9:32 pm

Interesting question. I've considered bumping up a turbo size from vnt-15 to vnt-17, but then to take full advantage of a larger turbo I'd need to do some other things as well, injectors/nozzles, different tune, larger pump, etc. I'm pretty sure Andy Bees is running stock setup with an ecu tune. Hopefully he'll chime in.

The question might be better received over at the TDI club forums where the experts hang out. I'm under the impression most people who put tdi engines into vans don't mod them too much besides a low level ecu tune or some pump pin mods.

I'm interested to hear what others have to say. Also if its of any consequence to you, I'm the third owner of my alh tdi swap and its got over 100k on it. The trans was rebuilt at the time of the swap and could use a rebuild at this point. I'm not to fussed considering it got a good 100k on it spun by the 110hp/200ftlbs engine.

Sat Feb 07, 2015 9:50 pm

Assuming you are using an AHU conversion the preferred upgrade
from the tdi-forums when using the ahu in passenger vehicle

vnt 17/22 hybird (spool fasts & more air at higher rpm & lower egt)
-lots parts, turbo, & ecu tune
~ upgrade cost if using stock afn parts & new NA turbo $3K

wastegate -> gt2052 & family
-few parts spools a little slower & moves alot of air egts spould come down
using the aaz manifold & clock the turbo its a almost a drop in
~ upgrade cost if new NA turbo $800-900

-

Sat Feb 07, 2015 10:15 pm

The VNT's really are kick ass. I mocked up a GT1749VA turbo (came in the 2005.5 passat(VNT17) on an AAZ manifold and it would work but I ended up scratching the project after some deep thought. The main reason I did the TDI install was reliability and I was possibly going to loose that with some of the custom stuff (custom ECU tune, different N75, turbo adapter, sticky vanes, etc) I now have a wastegated GT2052 waiting to go on. Sure it won't spool like a VNT but it is much larger than the KO3 and should really improve highway driving. Plus they are only $800 and a few silicone hoses and you are done. I would have been near $2,000 for the VNT swap. Luckily I sold the turbo and made my money back. Yes, It's rather easy to get 180+HP with a VNT17/22, chip tune and nozzles but I think it may be a tad much for the syncro trans.

FWIW I have 85k miles on my TDI swap (trans was done by German Transaxle and I've had 0 issues with it) and have run the Ko3 the whole time. It has large nozzles and a fairly aggressive tune for a K03. I don't actually mind the little turbo but it does run out of juice on the highway. I usually have the cruise on at 72 MPH at 3050 RPMS with a .70 4th and 28" tires. It's seen 15hrs straight on a few occasions. Not saying its the best or anything but I have run Amsoil 75-90 in it since 1000 miles.

****If anyone is interested I have a set of Titan 520 nozzles and a set of chips from Malone Tuning to convert a AHU (FA ECU) to run a VNT17 turbo. They are set up for the nozzles. I would sell for all for less than the price of the chips****

Sat Feb 07, 2015 10:20 pm

An AHU or ALH TDI in stock form will put out enough torque that you're tranny will not be particularly happy.

A modded TDI will ruin a Vanagon tranny sooner than later.

While driving a Vanagon you really shouldn't be trying to win any races.

This all adds up to; the stock turbo is just fine.

You will never really notice any difference with just a turbo swap. If you want more power just get a chip tune and be done with it, with that you will get more power without changing the turbo.

A turbo swap will not result in any measurable gain in MPG, and will not result in any gain in HP unless you add more fuel via larger injectors or a chip tune.

Sun Feb 08, 2015 12:03 am

jackbombay wrote: An AHU or ALH TDI in stock form will put out enough torque that you're tranny will not be particularly happy.
A modded TDI will ruin a Vanagon tranny sooner than later....

What's the weak point on the stock transmission - Like what's the first thing to go if someone drops in a 90 HP TDI?

Sun Feb 08, 2015 9:25 am

tjet wrote: jackbombay wrote: An AHU or ALH TDI in stock form will put out enough torque that you're tranny will not be particularly happy.
A modded TDI will ruin a Vanagon tranny sooner than later....

What's the weak point on the stock transmission - Like what's the first thing to go if someone drops in a 90 HP TDI?

I know some tranny shops wont warranty their work if the trans is bolted to a 2.5 subaru, and that engine puts out about the same torque as a stock TDI, but the TDI does it so early in the RPM range that its easy to hit the tranny with the full torque output of the engine more frequently. It is torque that is hard on trannies, 90 HP at 2000 RPM (TDI) takes double the torque that 90 HP at 4000 RPM (WBX) does. It is that torque that the tranny doesn't like.

My tranny had 60,000 miles on the rebuild and it had a laundry list of things wrong with it when it went in for a second rebuild...

I had a stock AHU, but the stock turbo did blow up and was replaced with a boraparts "hybrid" that just has a slightly larger compressor wheel IIRC. I never "added more fuel" to that engine, as the van wasn't really happy over 67 MPH anyway.

Sun Feb 08, 2015 8:08 pm

Very interesting stuff... I have no plans on going wild with the power. I will be fitting new nozzels and getting the injectors balanced, mostly just because my donor engine was up there in miles. It does seem that the transaxle is the real limiting factor in a lot of ways, thank god the 2wd's are so much cheaper to rebuild hahaha.

I would love to hear more opinions.

Tue Feb 10, 2015 12:36 am

kustomizingkid wrote: Very interesting stuff... I have no plans on going wild with the power. I will be fitting new nozzels and getting the injectors balanced, mostly just because my donor engine was up there in miles. It does seem that the transaxle is the real limiting factor in a lot of ways, thank god the 2wd's are so much cheaper to rebuild hahaha.

I would love to hear more opinions.
My AHU with a K03 turbo easily hits 1000F EGT in 4th, just cruising at 60. Will changing out to a VNT actually lower those? Isn't the egt measured pre-turbo?

Tue Feb 10, 2015 7:51 am

From what I have experienced your tune will have the greatest impact on performance and temperatures. In the process of tuning my VNT17 on my PD I had to go back to the stock tune to log data for a few days. Stock was max boost of 14-15psi. My EGT's went up, performance went way down, and fuel consumption went up. Now with a peak boost of 26psi my EGT's max at 1250F under load in the mountains. Performance is crazy, and fuel consumption is better than stock tune (28-31mpg). More boost was the way to bring EGT's down.
Regarding turbos. I never did any tuning with the stock KP39 so I can't make any comparisons. I had decided I wanted more power and my tuner (Malone) directed me to the VNT17. I will say that the VNT17 with no tune did seem to perform very similarly to the KP39

Tue Feb 10, 2015 8:11 am

Tue Feb 10, 2015 8:14 am

luVWagn wrote:
My AHU with a K03 turbo easily hits 1000F EGT in 4th, just cruising at 60. Will changing out to a VNT actually lower those? Isn't the egt measured pre-turbo?

EGT should be measured pre turbine.

I'm pretty sure the Ko3 is rated for 1,400*sustained. What is the highest you have seen with the stock tune, 1,250 or so?

IIRC the PDs inject a small amount of fuel very late in the combustion cycle, this is for emissions reasons, this fuel does nothing to propel the van down the road though, so it hurts MPGs and increases EGT, a tune will generally eliminate this late cycle fuel injection so tuning results between AHU/ALH and PD shouldn't really be compared too closely.

Raising boost does/should generally lower EGT slightly, but if your intercooling is minimal/lacking then higher boost results in higher IAT so your EGT doesn't really come down with higher boost.

Tue Feb 10, 2015 10:39 am

I noticed a significant drop in EGT when I added a diesel catalytic converter. 1250 is the max I will run mine up to, and now with the cat, it barely reaches 1050.

Stock tune, stock turbo, and Sprint 520 nozzles is enough to propel my 5300 pound syncro up anything. I still have to downshift up the big hills, but I'm not in any hurry.

Tue Feb 10, 2015 12:49 pm

hans j wrote: I noticed a significant drop in EGT when I added a diesel catalytic converter.

That is really interesting. I built my whole exhaust without the cat thinking it would increase temps. In fact I didn't run a muffler for the first 30,000 miles for the same reason.

Tue Feb 10, 2015 1:39 pm

Mine was straight piped all of the 4 foot length my exhaust is. I'm still running no muffler, just the cat. It also quieted the exhaust noise inside the van quite a bit too!

Tue Feb 10, 2015 3:18 pm

hans j wrote: Mine was straight piped all of the 4 foot length my exhaust is. I'm still running no muffler, just the cat. It also quieted the exhaust noise inside the van quite a bit too!

My turbo manifold was "backwards" so my entire exhaust system was 16" long, then I added a cat and had to exit out the side and ended up at 22" f or the entire exhaust system. The cat REALLY cut the noise down a lot, and made the exhaust quite a bit more pleasant smell wise.

The EGT reduction is a bit puzzling though, is your probe pre turbine?

Tue Feb 10, 2015 4:09 pm

Wastegated turbo will handle EGT's that the VNT cannot. I would not suggest running egt's that high but it has a greater safety factor. Wastegated turbo is more reliable. If the vanes get coked up on the VNT and you pull out of a gas station with a little spirit at say 3000 ft altitude you just may blow the turbo and hydro lock #3 cylinder with the oil. Bent rods, new head job etc....