Lots of talk of trans ratios in TDI

[theman53]

I have a theory, more of a known fact to me, but to some theory. Here it is, on the TDI people are running a lot of them 8v included say that the trans are geared too low. Lot of people say they wish the trans were taller etc., but I think all people that say this have a VNT 15 or K03 on the TDI. I personally hate the vnt 15 as over 3,000rpm there isn't much to be had even with my stage2 tune. Almost all the power is made under 3,000rpm. With that the case it seems as if the car doesn't pull well and it is "out of gear" I have found that it is not the gear but the turbo is just done. I think that the solution is to put on a bigger turbo not try to get gears that still go fast but keep you under 3,000 rpm. If the power was made from 1,500 rpm to 4,300rpm I think that the trans issue would suddenly dissappear.

[R.O.R-2.0]

my 1.6 LOVED the vnt15 i had on it.. it breathed fine clear till ~6000 revs..

[libbydiesel]

I have a lot of experience with VNT15s (and 17s) and almost all of the stock 1.6 and 1.9 turbos on several 1.6 and 1.9 engines.  The variable geometry makes the VNT with vanes closed spool faster than the K03 and with vanes open flow considerably better at the high-end than the K24 or T3.  I'm not sure what your issue is with your ALH, Lucas.  It may be the considerably higher weight of the A4s or there could be an actual engine management issue.  A friend's AHU runs like a total turd (worse performance than a 1.6 non-turbo Rabbit) and doesn't toss a code...    

[R.O.R-2.0]

I have a lot of experience with VNT15s (and 17s) and almost all of the stock 1.6 and 1.9 turbos on several 1.6 and 1.9 engines.  The variable geometry makes the VNT with vanes closed spool faster than the K03 and with vanes open flow considerably better at the high-end than the K24 or T3.  I'm not sure what your issue is with your ALH, Lucas.  It may be the considerably higher weight of the A4s or there could be an actual engine management issue.  A friend's AHU runs like a total turd (worse performance than a 1.6 non-turbo Rabbit) and doesn't toss a code...    

Yup, that sounds about right..

mine never felt choked up, even pulling clear till the power went flat from the cam plate skipping the rollers..

i had my engine significantly over-fueled, so it still spooled relatively fast, and would make ~20psi until it started to die..

[theman53]

Mine runs ok, if you are under 3,000 rpm. It just fizzles after that. My thinking is all the guys that want a trans with higher gearing is that they run out of Turbo. 8v and some others like the small turbo instant spool but I think that is why they also want the gears. It pulls great off the bottom but it just seems like the turbo needs a govnor mod lol. I am betting if they made power over 3,000 then the 'need' for a trans would be gone.

My alh isn't the best runner, no codes, but without the tune it was basically just about the same as CRSMP5's mk1 jetta when following him. It is an N/A mk1 jetta at that. I think it was the best running one I have ever seen but still.  Now with the stage 2 tune it doesn't do bad, but it makes that distinct line at 3,000 rpm more noticeable.

[fatmobile]

 So you're saying the VNT-15 won't push 18 PSI any higher than 3000 RPM.
 Because that's about the max of it's efficiency range.

I think it will push 18 with the vanes half way open at 3000RPM.
I know it will with a 1.6.

[theman53]

I am saying I don't like small turbos. On the TDI I have it gets less and less power over 3,000 rpm. It really pulls well until that point. When it is pulling well it feels like the gearing is good. When it stops pulling well I think that is why 8v and others say they need higher gears. Never did I make a claim of psi.

[R.O.R-2.0]

So you're saying the VNT-15 won't push 18 PSI any higher than 3000 RPM.
 Because that's about the max of it's efficiency range.

I think it will push 18 with the vanes half way open at 3000RPM.
I know it will with a 1.6.

mine would pull ~20psi @ WOT when it was still in good shape..

maybe the small VNT is better suited to the smaller engine?

[burn_your_money]

How's your intake? Is the timing in spec? My friends AHU drove similar to how you describe and his timing was off.

[theman53]

I will check all that when I do the timing belt here soon. From what I can see nothing is bad.

Still, if you make all your power down low and it even stays there, it feels like you lose pull. I don't think 8v and others need the 2:1 ring gear and .5 overdrive that they think they do. I think they need more turbo.

[R.O.R-2.0]

I will check all that when I do the timing belt here soon. From what I can see nothing is bad.

Still, if you make all your power down low and it even stays there, it feels like you lose pull. I don't think 8v and others need the 2:1 ring gear and .5 overdrive that they think they do. I think they need more turbo.

TDI engines are just as capable of revving out, as our little 1.6L engines..

IIRC, andy2 shifts @ 7500-8000 revs...

[fatmobile]

I will check all that when I do the timing belt here soon. From what I can see nothing is bad.

Still, if you make all your power down low and it even stays there, it feels like you lose pull. I don't think 8v and others need the 2:1 ring gear and .5 overdrive that they think they do. I think they need more turbo.

 How much boost are you getting at 3000RPM?
 What EGTs?

[hillfolk'r]

My02c.
Tdis need the taller gearing partly cause of a low redline(stock)
And because the torque curve is so wide the ratios in 020s with the hi numerical diffs dont help
Something like a 3.5 would be nice.
Because of the different nature of a tdi the only way i can explain it is  if u take a wide ratio 020 and put it in a tdi, its like swappin in a gti close ratio. A wide ratio had good spreads its the final drive. It needs a 3.67 or lower to keep it in the grunt.
Do the math i wanna say my old 79 tdi m with a 7a and stock 175-70-13 tires is redlined at like 112 or 115 maybe. Thats 4700 area btw i said stock redline. No sense revvin to the moon the tq is so fat and wide
And the merc turbo liked the revs i didnt mind it too much i hit 5 k by mistake not paying attention a few times. I def was not running out of turbo but hitting 4 th by like 60-65 sucks trust me. Hard to maintain that 5.55 0-60 with that many shifts. Im in 5th at half track in the 1/4

[MachZ]

My alh isn't the best runner, no codes, but without the tune it was basically just about the same as CRSMP5's mk1 jetta when following him. It is an N/A mk1 jetta at that. I think it was the best running one I have ever seen but still.  Now with the stage 2 tune it doesn't do bad, but it makes that distinct line at 3,000 rpm more noticeable.

Sorry to kind of necro a thread for my first post but just wanted to run an idea by you for you to try out. The ALH in my Beetle ran almost exactly as you described, good power under 3k RPM then falls on its face. Turns out the MAF was bad. Never once has it ever thrown a code or CEL for the MAF but it was most definitely bad. After replacing the MAF it revved above 3k with ease and actually was fastest revving above 3k. Power starts to taper off sharply at around 4300 - 4500 RPM.

Quick and easy test is to unplug the MAF and if you gain power back then it is bad and needs replaced. The power gain is very noticeable as it should freely rev above 3k with a bad MAF unplugged. Once you get the new one in the power gained is even more so than the power you get from the unplugged MAF. If yours is bad and has the Bosch MAF use the new part: 0 281 002 757. Got mine for $90 shipped on eBay.

Did a video today to show how mine revs through the gears to 60 to maybe help you compare, see if maybe the MAF is your issue. The Beetle is basically stock though I do have the muffler removed, snow screen removed, and timing in adaptation is advanced around 4.5 degrees. Static timing on the pump is nearly dead on at the recommended timing in the middle of the graph, though planning on advancing to the top of the graph sometime. I think I still have a few more bugs to work out, thinking maybe the injectors need cleaned but will likely just get new nozzles if I screw with those. Anyway, here's the video: newbielink:http://www.youtube.com/watch?v=q6v80QJ4Xbg [nonactive]