VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: subsonic on May 28, 2007, 03:40:47 pm
-
After reading a few links about these from here on the forum, I decided to take a cruise around the internet to find some more info. It seams that Garrett made a bunch of these for Dodge but Dodge's car did not do well so there was an overabundance of these turbo's avail. It appeared that Garrett was selling them cheaply. Specificly the VNT 25. Does anyone here know anything about this? Have any good leads on them? If so what do you think about them on the vw diesel? I have seen that Andrew has a nice new functional setup with a VNT 15.
-
i doubt the dodge vnt's would be useful on aa diesel though... the a/r would be made for top end power...
named tintin was the pioneer of the accelerator actuated vnt turbo... and yes andrew made a nice system using the same concept and was very pleased with it!
if you read jake's thread about putting a VNT on a rabbit, he was getting boost from just blipping the throttle... those turbo's spool up really damn quick!!
-
i have a internet-friend he have a gt1749v on a 1400TD IDI (not a vw as well) he was controlling it with electronics, it could make 1bar(+-14psi) on idle.
early years the turbo's were called vnt, now its by example gt1749v, the v stands for vnt. i also think the gt versions are better than the old T versions, thats one of the reasons why i like vnt turbos, GT-gasser turbos are expensive, but if you search good you can find a GT-VNT pretty cheap.
Greetz, Benjamin
-
Must be a high idle. My GT1749V on a 1.9 doesn't make any noticeable boost at idle, but it does climb rapidly with a little throttle. In fact, I can get it to surge sitting in the garage just playing with it.
-
The VNT25 that was on the shelby was sized differnt then todays vnt's as it was still based on the old garret sizing of t3, t4 ect... It is not even close to the same size as the now known VNT25. VNTxx as we call it now is a slang that was adopted first by tdiclub, and then spread everywhere as easy of use in discribing the turbo. In fact though a VNT17 as we call it can mean a big verity of turbo's Ie GT1749v, GT1752v, GT1744v ect... The v at the end infact tells us that it is varrible vane, the rest of the numbers tell us the size of the turbo as according to garrett sizing standerds for GT seires turbo's.
So what does this mean to you? The VNT25 off the dodge cars is a lousy fit to our motor's and you should look elsewhere. :wink:
-
Where would you find a description of: GT1749v, GT1752v, GT1744v and the differences between each digit?
-
Well, the 49 , 44 or 52 are the A/R of the compressor. I did have a link to a good foreign page with maps, but I can't find it now.
-
i have a internet-friend he have a gt1749v on a 1400TD IDI (not a vw as well) he was controlling it with electronics, it could make 1bar(+-14psi) on idle.
I know you know your stuff, but 14psi at idle sounds like a load of you-know-what to me. That high of a pressure ratio at such a low airflow would surge like a mother. There isn't enough energy in the exhaust at idle to make that much boost anyways.
Even at 1000rpm idle and ideal conditions, I can barely get the boost gauge a hair off it's 0 stop. Even loaded I can't make more than 10psi below 1500rpm without major surging.
-
Well, the 49 , 44 or 52 are the A/R of the compressor. I did have a link to a good foreign page with maps, but I can't find it now.
please, if you find any vnt turbo maps, post them here :D
@OM617: i cant say this was under load or not, all i know is he said to me it was able to make that pressure on idle, but he dont do that becouse problebly surge.
Greetz, Benjamin
-
i have a internet-friend he have a gt1749v on a 1400TD IDI (not a vw as well) he was controlling it with electronics, it could make 1bar(+-14psi) on idle.
I know you know your stuff, but 14psi at idle sounds like a load of you-know-what to me. That high of a pressure ratio at such a low airflow would surge like a mother. There isn't enough energy in the exhaust at idle to make that much boost anyways.
Even at 1000rpm idle and ideal conditions, I can barely get the boost gauge a hair off it's 0 stop. Even loaded I can't make more than 10psi below 1500rpm without major surging.
and that is with the vanes in the fully closed position???
-
please, if you find any vnt turbo maps, post them here :D
Greetz, Benjamin
I thought I remembered maps, but it just had this.
(http://www.turbomaster.info/img/turbos/gt15_25_chart.gif)
-
I could be understanding it wrong, but after looking at some stuff, it seems the GT and GT V have the same maps for the same size/trim. So a GT2252V would have the same map as a GT2252R, which makes sense. The variable vane shouldn't change the map, only how quickly it can get to a certain point on the map. So.....
(http://www.rbracing-rsr.com/turbo/TurboMaps/GT15compress.jpg)
(http://www.rbracing-rsr.com/turbo/TurboMaps/GT20compress.jpg)
(http://www.rbracing-rsr.com/turbo/TurboMaps/GT22compress.jpg)
(http://www.rbracing-rsr.com/turbo/TurboMaps/gt2540rcompress.gif)
(http://www.rbracing-rsr.com/turbo/TurboMaps/gt25rcompress.gif)
The 17 map seems hard to find, but I found a paper that has about anything you would ever want to know about the vnt 17 in 55 and 70 trim http://deposit.ddb.de/cgi-bin/dokserv?idn=974988219&dok_var=d1&dok_ext=pdf&filename=974988219.pdf
It's a long technical read, but has some interesting stuff.
-
and that is with the vanes in the fully closed position???
Yes. My setup has the vanes closed all the time except for maximum boost.
-
(http://www.rbracing-rsr.com/turbo/TurboMaps/GT15compress.jpg)
One day I'll have to learn how to read these damn turbo maps :?
-
One day I'll have to learn how to read these damn turbo maps :?
http://www.automotivearticles.com/Turbo_Selection.shtml
-
understanding turbomaps can also be found here
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html
i was also thinking those maps should +- the same, but only nobody could say this is a fact.
Greetz, Benjamin
-
So with the vnt style of turbo, how do you size one for your application? If the internals are variable and change to meet load conditions, this changes everything, does'nt it?
-
No, the variable part is on the exhaust, so it just changes how the turbo spools. The map is for the compressor which will pump x amount of air at y psi pressure when turning z rpm. You would size it like any other turbo. But that is also where vane control comes in, to make sure you stay within the safe area as I believe a VNT is easier to put in the surge zone since it spools faster.