VNT1749 laggy!? advise!?

Adamski · Mar 24, 2011

VNT1749 laggy!? advise!? vain setup???

Hi guys, my mechanic has just been and fitted my second hand 1749, he said the car was nice and quick before the turbo change. due to the old turbo oil seals going i wanted to upgrade.
Any way he fitted it up tonight but says it goes very well but its VERY laggy says it doesnt pull hard till 3000RPM then pulls like a train...
surely that isnt right? Could the turbo be bit screwed!?

any help appriciated
Ad

EDIT:- done some searching and it could be the vain setup?? how do you set them up or whatever it is my mechanic has never done this before!?

K.I.T.T. · Mar 24, 2011

Is the actuator / stop screw adjusted properly?

Ash

Adamski · Mar 24, 2011

what do you mean!? does it need adjusting?

NewTdi · Mar 24, 2011

My vnt15 used to boost a little before my 1749 does; like yours, once i reach 3000rpm the car really takes off. A liitle adjustment to our tune could help boostba little sooner!

Piranha · Mar 25, 2011

IS the turbo new or second hand???

I had that issue when I installed my vnt17 (ebay.de).

Turbo felt real laggy.

Blew it's seals 5 miles down the road and nearly hydrolocked my engine.

If it's second hand get it rebuilt!!!!!

Adamski · Mar 25, 2011

it is second hand yes, however i have done some research and i think perhaps the vains are sticking, my mate says its got better today slightly as he took it for MOT, it passed and he said he hasnt got time right now to remove the turbo and clean it all up so he's gonna gimme a oil change anyway and try and squirt some wd40 on the rod and se if it may help then he'll bring it back to me to use for 2 weeks then if still playing up we will remove it and clean it up

, he's also going to give the actuator a few turns to try and make it pick up a bit better

Nash_TDI · Mar 25, 2011

You need to check the actuator adjustment not just give it a few turns. You need to see at what pressure it starts moving and at what pressure it hits the stop.

JFettig · Mar 25, 2011

Don't just start adjusting the actuator and stop screw, especially don't even touch the stop screw!

Measure the vacuum that it takes to lift the actuator off, it should be 3-5in-Hg, it should also stop at the stop screw between 18 and 20in-Hg. Verify its function and its numbers before making any adjustments!

Jon

Adamski · Mar 25, 2011

whats hg!? do i need to buy a proper vacuum pump?

ok well i have the car back tonight and it basically doesnt hardly boost till 3k then as my mate said it builds up then and comes on very strong, you can hardly hear the turbo whistle, plus he said it was going into limp mode once or twice...

Which after driving it leads me to believe the vains are not workng properly its probably my own fault the turbo has been sat in a box for near a year and came off a written off PD150 so the carbon build up and fact its not been used would indicate that its sticking which unfortunatly means removing it again to clean it up

NewTdi · Mar 25, 2011

try using the oven cleaner method to clean the turbo, there is a thread somewhere

http://forums.tdiclub.com/showthread.php?t=246287

JFettig · Mar 25, 2011

inches of mercury, I'm sure you're use to using different units, its one of the many 29in-hg is 1 atmosphere.

A $30(usd) hand held vacuum pump will do the trick, odds are that you know someone who has one - like the mechanic working on it.

Jon

85_305 · Mar 26, 2011

Find somebody with a mityvac... your vnt rod should begin cracking at 4-5hg and starting to close NO SOONER than 18hg. I'd be willing to be your VNT rod didn't come tuned correctly and it just needs to be set.

JFettig · Mar 27, 2011

85_305 said:
Find somebody with a mityvac... your vnt rod should begin cracking at 4-5hg and starting to close NO SOONER than 18hg. I'd be willing to be your VNT rod didn't come tuned correctly and it just needs to be set.

I just got my jetta with 184k on it running, before putting the turbo back in I checked the VNT rod, it cracked at about 2inHg but I figured, 184k miles, I'll leave it, test it then adjust it. Boost spike is obnoxious on this and will bring it up to ~4inHg.

My GT1749VA for my Passat was also cracking around 1.5inHg from the factory, that thing spooled like crazy but spiked pretty good too. Brought that up to 4inHg and adjusted the tune and it spools pretty awesome still.

Jon

85_305 · Mar 27, 2011

If your rod starts closing before 18hg, it's going to have disgusting spikes. It
s not so much when it opens, but moreseo when it starts closing.

Adamski · Mar 29, 2011

well there is no boost what so ever until you hit 3k then it all starts coming in but will only boost 1.2 bar held. on the std vnt15 it was boosting perfect and peaking 1.7bar holding 1.3-1.4. We have only changed the turbo nothing else.

the car will also go into limp mode after 5 mins of driving. Not sure if the rod is set right but i have a feeling the vains are sticking...

cfm56 · Mar 29, 2011

like everyone else has mentioned, check the actuator and the numbers that its starting and stopping at. Its not hard, quite simple actually. REgarding the vnt cleaning...there is a easy write up on here that you can use to take apart your turbo and clean it.....

first check your actuator for proper adjustment...if it is good and it still gives you similier symptoms, yes do the proper vnt cleaning method on it and then see how it performs.

JFettig · Mar 29, 2011

did you check the actuator? it will tell you if the vanes are sticking and if it is set right just by getting a hand operated vacuum pump(mitivac) on there.

if it is sticking, you will see the actuator lever sticking or not moving very far.

Jon

JFettig · Mar 29, 2011

85_305 said:
If your rod starts closing before 18hg, it's going to have disgusting spikes. It
s not so much when it opens, but moreseo when it starts closing.

I believe this is incorrect.

Adamski · Mar 29, 2011

yer guys i have ordered a pump thanks, i only got the car back friday BUT i should be going back to my mates this weekend to remove the turbo and clean it and get the pump on it to see what its doing... more a case of a learning curve just hope its a fairly easy fix. I heard a few places that the rod sticking(vains sticking) can cause the car to go into limp mode so hopefully this is all it is...

JFettig · Mar 29, 2011

Your first action should be to check the actuator, its a lot of work to pull the turbo, especially a lot of to work to get it apart. Checking the actuator is SUPER easy, just pull the vacuum line off the N75 that goes to the turbo and hook up the vacuum pump and visually watch the for the actuator to move. If it needs to be adjusted, it takes a 10mm wrench then just turn the thumb knob, once again, can be done on the car.

Jon

85_305 · Mar 29, 2011

Adamski said:
well there is no boost what so ever until you hit 3k then it all starts coming in but will only boost 1.2 bar held. on the std vnt15 it was boosting perfect and peaking 1.7bar holding 1.3-1.4. We have only changed the turbo nothing else.

the car will also go into limp mode after 5 mins of driving. Not sure if the rod is set right but i have a feeling the vains are sticking...

It could also be because the car hasn't been tuned properly on how to utilize fueling maps for the new bigger turbo, which will have different curves and requirements than the last one. Also, what really helped me out, was to make sure the MAS in the intake tract is very clean too..

JFettig said:
I believe this is incorrect.

I can assure you it's not incorrect. Jeff at RC has confirmed this as well.

Adamski · Mar 30, 2011

cheers guys i am not expecting the turbo to possibly produce the same boost as the last until remapped due to the difference in size, however the running issue was no there at all before so is either vain or rod issue i believe , but yes i will try the pump on the actuator first before removal

Adamski · Apr 2, 2011

OK finally seems to be resolved!
after checking the rod it seemed to be working yet a little stiff, my mate let me down so i did the work at my house, i removed the turbo dismantled it cleaned it all up and refitted it all in 3 hours.
BUT the problem was still there so after checking the boost hoses and various others i checked the N75 hoses to find 1 was not connected

... so by being a bit confused where it went as my mate assured me he had 'only removed the hose to the turbo and replaced it with the new one' i had a fiddle managed to blow the hose off, then after another go i got it in correct.

Now the turbo whistles lovely and pulls like a train now running 1.7bar held!

85_305 · Apr 2, 2011

Glad you got it fixed brother!!

VNT1749 laggy!? advise!?

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