VNT25 (VNT actuator theory)

[garrettp]

well, i'll be darned... looks like i can post offer all Hi again all. for those that don't know me, that is prolly a good thing.

regardless, I am in the process of putting a VNT25 on my car and need input on the VNT actuation PSI. I will be using PSI instead of the stock vacuum system as i can control boost on my own this way. I was wondering if anyone would have input as to when the boost should open the vanes? i was thinking of 9PSI is where the vanes should start to open.

I do have a dawes device on my car now that operates my K04 turbo which seems to work quite well and throws no codes as the stock N75 valve is still hooked up electronically. I will also be throwing in a 12mm pump and i have .203's now but will go to .216's after i pay some medical bills off (pnuemonia )

the other question i have is if anyone knows if the VNT actuates at idle or when you slow down. as i understand the vanes should be open when you slow down or at idle so as to releive the turbine and also help keep the vanes free from carbon. i was thinking of installing a vacuum gauge on my stock N75 to check to see exactly what it does and when it does it (if at all of mentioned above). has anyone checked this? any input would be great.

for those that dont know me or those that do and thought i died, here is a quick run down of my JEDI...

2000 JEDI TDI (debaged save a "1.9 TDI" from Euro Audi)
281,000 miles with original clutch (thanks K04)
UPsolute Chip (custom made for me )
Up FMIC (Christmas present from Rene)
.203's (Greg Landyut install)
K04 Turbo (installed and piped by me, i am a weldor/piper now)
Wide open Exhaust
PiperX Cone filter w/ custom CAI box
customized Euro cluster w/ V1 remote display
short(est) shift kit

The K04 is great save the lag. boost does not come on until 2300rpm but then it hits 24 PSI and LOOK OUT. I put the K04 on around 175,000 and this may help to the fact that i still have my original clutch . once i get the VNT25 in i am sure i will need a new clutch but i drive pretty moderate and save the punching it for the hi-way. will also take the head off and check the piston protrusion and maybe go with the 1-hole if need be (mileage is more inportant to me so no lowering compression for more boost for me).

I also work with a guy now that makes Bio in his garage so we are going to starting making it together /off topic info.

well, that is it. good to be back(<---?)
theres other stuff but i need to go to bed.

 

[mojogoes]

I would think the vanes would be fully closed at idle and anywhere short of max boost pressures....i would also suggest that in using a 12mm pump setup that the .216 nozzles may not be big enough....you may want to try the pp764's or R520's then just map back on fueling for the best results.

 

[Smithers]

Good to not hear from the person that's not you. I haven't been around here much either. I was at Bay Beach last weekend and didn't call you. The #'s I have for the person that's not you didn't work the last time I tried. You still have my # ?

 

[mojogoes]

I used to not know to be his friend also some time ago but now i'm not shaw it not being him anymore.

If its not the guy who i thought it wasn't i think i now know who it isn't yesterday.........he was never a friend to me in any case so no love lost here/there then.

 

[diesel des]

If its the VNT25 from the old dodge dont bother putting it on a tdi.

 

[garrettp]

If its the VNT25 from the old dodge dont bother putting it on a tdi.

dieseldes my old friend. please explain as this is the exact turbo it is. i got it new form a guy i know in LA. I am running my K04 right now and the VNT25 is somewhat similar. please keep in mind what other mods i plan on and explain if you would. thank you. I have reorineted the turbo so as it will work with the output where i want it and the oil return down. i will also be fabricating a new down pipe instead of using the 90* thing that it came with.

Smithers my love. i will ask myself next time i see me if he still has yer number. otherwise i will try to PM you with the new number for me's (man i miss the 4am thread )

I was early of late, because i was behind before, but now i am first at last.

 

[Mike_M]

Good to not hear from the person that's not you. I haven't been around here much either. I was at Bay Beach last weekend and didn't call you. The #'s I have for the person that's not you didn't work the last time I tried. You still have my # ?

If its not the guy who i thought it wasn't i think i now know who it isn't yesterday.........he was never a friend to me in any case so no love lost here/there then.

Jeez...you guys are giving me a headache. Good thing I'm just passing by this thread. Otherwise I might get really confused.

 

[oldpoopie]

ME thinks unless your planning on running 35psi plus, anything more than 20/22 hybrid is overkill for these motors IMHO. I think with the 25 you'll just have similar lag as you have with the k04. Just too big.

 

[diesel des]

The problem with the "dodge 25" is that it has a compressor suited to low boost high flow setup eg a bigger gasser. The tdi needs high PSI for high flow. The map is just "wrong" It wont be happy sitting at 25 psi. A VNT 20 is actually much better at making more boost than the "dodge 25". Dont waist a lot of time and money on this one......

 

[hatemi]

Des pretty much said the whats our problem. We need preasure and not that much flow. Curent VNTs start to crap out at 1.5-1.7bar... After that the EPM rises but not the real boost. We need a compressor that is capable of working eficently at ~1.9bar but that is yet to be found. Going bigger dosnt make that much difference if the compressor isnt designed to make higher boost than 1.5bar.

 

[garrettp]

Would either of you guys have the compressor map for the VNT25 that i could look at? I have a copy saved on a hard drive some where, but i have gone through so many computer upgrades it would be hard to find (plus i am running RAID0 and my computer no like when i hook up a single drive as slave as it tries to boot from that insteada RAID )

I know before i purchased this turbo i checked it out and did some calcualtions based off of what Rene had done for his GT20 upgrade program. the VNT25 actually looked better then K04 and even that didnt look bad.

with that however, it was`a`PITA to find the map in the first place so if someeone has it please send it or post it. thanks much

 

[hatemi]

I would very much like to find maps for VNT turbos too.

 

[fastvicar]

Not,

How are you planning on actuating the vanes? If it normally uses vacuum are you swapping out the actuator diaphragm for one from a bigger GT-series (boost/+ pressure)?

 

[diesel des]

I did see the map at one point but didnt bother saving it to my "maybe usefull" colection. its that bad. Google should find it though...

 

[garrettp]

Not,

How are you planning on actuating the vanes? If it normally uses vacuum are you swapping out the actuator diaphragm for one from a bigger GT-series (boost/+ pressure)?

Yes, the vanes will actuate by boost. The VNT25 comes with two ports on the actuator, one for boost one for pressure. As with the waste gated K04 i have now i will use the boost to open the vanes as the rpm (and boost) build.

The thing i want to know if the vanes open on a stock TDI when you let off the throttle or at idle. As i understand it this should happen to 1, keep the turbine free and 2, help keep the vanes from getting stuck.

What i may do is hook up to the vacuum side and have a valve in the cabin where as i can control when the vanes would start to open (and of course open the at will at idle or when coasting).

I supose i could just leave the vanes closed all the time

 

[8mrbump8]

You really should make some device to open the vanes at idle and more importantly when lifting off at full boost (ie changing gear) to avoid operating the turbo in surge/overspeeding. There are various ways to do this from connecting the actuator arm to the throttle arm, through using a ball valve to open vacuum onto the -ve port on your actuator, or as I use, a throttle arm mounted switch that activates a solenoid valve to add vacuum to the -ve port at about 1/5 throttle or below.

I am sure there are better ways, but these methods are currently used and work!