Vnt-15 installation, slowly but surely.....almost

[Rabbit on Roids]

oh hell yea, the more i push the smoke pedal, the more it screams. eventually, right before full boost, it screams almost the same sound as a G charger, not quite as loud. but yea, as long as my turbo is spoolin, you can definitely tell its there. do you have boost yet finally? should have tons...

[rabbitman]

With only the 2.25" dp and the rest yanked I get about 5psi max with the vanes opened.

Well I don't know what's up, my turbo screams right up and quickly gets so high pitch I can no longer hear it.

[rabbitman]

I'm starting to wonder if I'm loosing flow/pressure from using a long 1.5" turbo/intake mani hose.

After looking at this: http://www.vwdiesel.net/forum/index.php?topic=11698.0 and seeing how big of turbo he can spool I must have real problems if I can't spool a little vnt.

[Rabbit on Roids]

i used to have a rabbit radiator rigged up as an intercooler, worked alright. still got 18psi out of it. but when i just had it non IC, the boost hose was about 4 feet long to go from my turbo to intake mani. then it would run alot more boost too. and the intake mani before the IC was on there, it would burn your hand if you touched it. now with the IC, its never warmm, always ice cold.

but i doubt you are losing boost because of your hose. the only reason you lose boost from a hose, is if the hose has a hole in it. i had a boost leak for a long time after i plumbed in my 740 IC. it was right after the turbo, but it would still boost to 15 psi. if you took all the boost pipes and hoses i have and mesure there length, i bet the air has to travel 8 or 9 feet to go from the turbo to get to the intake port on the head.

[rabbitman]

Thanks I'll rule out the hose then.

I really should stop complaining untill I install this, in case it's not clear in the pic, the cable housing retainer is attached to the boost can rod and the rod/triangle piece slide in the bracket. Here's the pic:


The only problem is if the vanes have to be partway closed to get the boost I'm after the turbo might be overspeeding the whole time and I wouldn't know it. grrrrr

I undid the compressor intake and outlet hoses and it acts the same, I didn't drive it for fear I'd suck a rock through it. I might've not been able to hear the turbo since the engine is so loud without the exhaust on, when I close the vanes in neutral and rev it I can get about 10psi and can hear the turbo real well.

[Rabbit on Roids]

you dont need to close the vanes at all to get boost. i have my vanes wide open and still get 25psi out of a half worn out turbo. you should be making enough boost to make a nice sized head shaped dent in your hood...

[rabbitman]

Ok I finally got a 2.5" straight exhaust pipe installed, so it goes 2.25" DP into a 2.5" pipe with no muffler.

I haven't done much tinkering lately but I did turn the fuel waaaay up to see what would happen, it topped out at 8psi boost, some smoke and 1350F egt that's when I back off.

I could definitely feel the boost kick in, but to get more I'll need to close the vanes a tiny bit.....or would a intercooler help? I seems like the little bit of boost I get is just enough to burn more fuel and cause high egt's so maybe a IC would help cool the egt's some.

I didn't test it very much like that since I didn't want to turn the underside black, now I can test it better.

I'll post pics of the exhaust as soon as I get my hands on a camera.......

[Rabbit on Roids]

8 psi is sad with a VNT. there has got to be something wrong with it. HAS TO! i just got my rabbit runnin again yesterday, and it still boosts to 25 psi, and i have a muffler. i lost about 5 psi boost when i muffed it, but atleast the turbo doesnt draw soo much unwanted attention. if you could make your turbo have 15 psi, you would be like "HOLY FU*K, this thing friggen rips." they dont even really dump more fuel till around 10 psi, then its like a big, fat hit...

[macka]

yea check your impeller shaft for play. I lost mega boost when I had a sloppy bearing then it went bang and I lunched the whole damn thing 

[rabbitman]

yea check your impeller shaft for play. I lost mega boost when I had a sloppy bearing then it went bang and I lunched the whole damn thing  

I'm running a 2-3 month old center section so it better be good still......

Today I turned the max fuel screw up as far as it would go before I ran out of idle adjustment. It's not as smoky as before the turbo was installed , even off boost.

Anyways I can get 10psi and the smoke almost starts to clear and then the egt's hit 1350F and I back out.
It's weird though, I have no LDA or stop pin so I control all the fueling with my foot, I can hold the egt's at 1100F and the boost will sit at 1-2psi then if I slowly push the pedal more the boost jumps up to 5-10psi and the egt's climb just as quick.

This is lame

[Rabbit on Roids]

On my friend's quantum with VNT-17, even with the vanes wide open boost will go above 20 psi without any visible smoke and EGTs will not ever go above 900° even on an extended hill.  There's still something not right with your setup.  I'm not sure what it is, but you shouldn't be getting the smoke and EGTs without the boost.

Im with you on this one. well, and just for the fact that i know what a VNT should do.

my center section is at least 20k miles old, cause thats what just i have put on it. i think the jetta it came off of had somewhere around 125k miles, so, my center section has about 150k on it, no vain control, and it still spools quick enough and makes lots of boost. are you POSITIVE? that you dont have a gigantic boost leak? or your timing really f***ed up?

[rabbitman]

On my friend's quantum with VNT-17, even with the vanes wide open boost will go above 20 psi without any visible smoke and EGTs will not ever go above 900° even on an extended hill.  There's still something not right with your setup.  I'm not sure what it is, but you shouldn't be getting the smoke and EGTs without the boost.

Im with you on this one. well, and just for the fact that i know what a VNT should do.

my center section is at least 20k miles old, cause thats what just i have put on it. i think the jetta it came off of had somewhere around 125k miles, so, my center section has about 150k on it, no vain control, and it still spools quick enough and makes lots of boost. are you POSITIVE? that you dont have a gigantic boost leak? or your timing really f***ed up?

Well.....as for leaks I plugged the compressor inlet and pumped the intake mani to 15psi for an hour or more. I sprayed soap on everything and with the hoist I could lift it up and walk under so it was a thorough inspection, the only leak was the slight leaking of the rings.
I'm very new to turbos so I'm not sure what a boost leak would sound like but I've noticed at full pedal there's the turbo whistle and a sound like a jet engine at takeoff power.

I'm sure the timing is good, it starts and runs perfect.

The only thing I can think of is where the airoduct hose goes into the compressor it isn't a good fit, the airoduct is 2" and the inlet is 1.75" and the hose has to make a sharp bend so it could be pinching itself off at boost. I need to get some silicone elbows but that stuff has to be ordered and cost quite a bit.

Thanks for the help guys

[Rabbit on Roids]

you know how an air compressor sounds when you have just an air nozzle on the end? sounds like rushing air. there should be the whistle from a turbo, but it shouldnt sound like a wind storm. only the whistle should get louder, there should be no "air blowing from somewhere at a high rate of speed" sound. but if you pressurized the intake for over an hour, you would have found a boost leak if there were one.

[rabbitman]

Well I feel really stupid

I decided to check for preturbine exhaust leaks, guess what I found......

I sealed the tailpipe and blew about 15psi into it and the stupid little pipe plug that I used to plug the egr port is leaking bad.

Here's an old pic of the port,


The plug (not installed in this pic) was too small so it went way in and the square part that the wrench goes on is almost flush with the port.
So can I just leave the pipe plug in and seal it up with braze? I've heard all the bad story's about cast iron cracking but when I drive the rabbit I get egt anywere from 250F-1350F in a very short time and the mani hasn't cracked yet so I don't see why brazing it should hurt it especially if I heat/cool it slow.

Thought's??


EDIT: I just brazed it. I removed it from the engine and slowly heated it, brazed it, then cooled it slowly with the torch and so far it hasn't cracked.

[Rabbit on Roids]

just MIG weld it. thats what i did to the port on my VNT. cut it off and welded a patch on. no special heating or cooling or anything.