Turbo Xs SBC

[Ho0ked]

Question, I have a turbo Xs SBC and since I put my 50 trim on it hiss's at idle while engine is running. Is this normal ?

I don't recall it doing this when I had my T25 on there.
The SBC is currently 4 turns out from closed, and only getting about 12 psi on my turbo.....


Did something happen while it sat in my living room zip tied to my fan shroud while I put my turbo on for 4 days ?

 

[project_tsi]

I think you mean MBC (manual boost controller), right?

Anyways, is your new 50 trim internally wastegated? If so, then the the actuators spring rate is different then what it was on your old turbo, and now the boost your running now, is not the boost you were running w/ your old turbo, due to the different actuator spring rates.

Another thing, if it is a MBC, MBC's seem to have a sweet spot for adjustment. I have a internally gated 50 trim and I remember adjusting the MBC too far in and any way I went, I could only get 14 psi. So I took off the MBC, took it apart, cleaned, and started from the beginning. Now my MBC is adjusted correctly, and I can boost 25 psi daily.


Hope this helps. _Dan

 

[ddavisaf]

By SBC he means Standard Boost Controller. Which is simply the model.

The hiss is normal since it's not a ball and spring type of MBC. It's a bleed valve. Make sure you've got the vacuum lines hooked up right.

 

[project_tsi]

I don't know, maybe your 50 trim is too big for a bleeder type MBC and its overrunning possibly? Maybe try switching to a ball and spring style MBC and see if that helps, as well as follow my info from my 1st post.

 

[oldman]

1. With the Turboxs mbc, it being a bleeder type valve, don't hook up your pressure source to the BOV line because it's part of your vacuum system and will draw in un-metered air during idle or part throttle. I know you no longer have the nipple on the compressor housing but tapping one will get rid of the hissing during idle.

2. Are you sure the mbc is hooked up properly? The Turboxs unit is hooked up completely opposite as a ball/spring type mbc. The bottom nipple is the pressure source and the side nipple inline with the adjustment knob goes to the actuator.

3. Perform an all out boost test run by leaving the actuator nipple open. If in fact you're able to boost past 12psi, mbc is the problem.

Good luck.

 

[Ho0ked]

First off thankyou for the ideas

secondly,Dumbass me

Forgot to run a boost leak test, guess what ?

Thankyou slowboy for not including a throttlebody elbow gasket to go along with my new elbow

Leaking like a sieve, can't get more then 5 psi using a bicycle pump without the elbow hissing like a pissed off snake

So Since I'm running the wastegate straight off the bov line to test static spring rate and I'm still only seeing 11-12 psi I "assume" that the elbow is leaking enough to cause my turbo to not go past 11-12 psi...............


No other leaks, I didn't see a need to boost leak test from the beginning because the slowboy frontmount kit pipes and clamps fit super nice and snug and perfect fitting



BTW after denting my water pipe, I got a nice little drippy drip leak of coolant from the pipe where it attaches to the housing thingy on the belt end of the block, not sure what I wanna do about that yet...... but its slow enough to last a few days a I think.



As far as tapping the compressor housing , I'd rather not go through the hassle if I can help it.....I'm tired after 4 days of building this car


on a side note BOTH cooling fans fit back into the car with no problems whatsoever



So I;m going to cut a gasket out of gasket sheet in the mourning and redo the elbow, wish me luck........

 

[project_tsi]

First off thankyou for the ideas

secondly,Dumbass me

Forgot to run a boost leak test, guess what ?

Thankyou slowboy for not including a throttlebody elbow gasket to go along with my new elbow

Leaking like a sieve, can't get more then 5 psi using a bicycle pump without the elbow hissing like a pissed off snake

So Since I'm running the wastegate straight off the bov line to test static spring rate and I'm still only seeing 11-12 psi I "assume" that the elbow is leaking enough to cause my turbo to not go past 11-12 psi...............

No other leaks, I didn't see a need to boost leak test from the beginning because the slowboy frontmount kit pipes and clamps fit super nice and snug and perfect fitting

BTW after denting my water pipe, I got a nice little drippy drip leak of coolant from the pipe where it attaches to the housing thingy on the belt end of the block, not sure what I wanna do about that yet...... but its slow enough to last a few days a I think.

As far as tapping the compressor housing , I'd rather not go through the hassle if I can help it.....I'm tired after 4 days of building this car

on a side note BOTH cooling fans fit back into the car with no problems whatsoever



So I;m going to cut a gasket out of gasket sheet in the mourning and redo the elbow, wish me luck........

Always run a complete boost leak test, you never know what your gonna find out, especially w/ new parts.

That drippy leak from your water pipe? Thats the pipe that goes into the water pump, and whats leaking is the o-ring. Mine did the same. I ended up having to pull the turbo off again, and replace the o-ring. It sucked ass, but it fixed it. Its just that the o-ring has been in that exact same position its whole life, now it was moved, and it won't seat or seal again, due to the fact that it had basically hardened.

As for tapping the compressor cover, if your going to have to pull the turbo to fix the water pipe, then tap it. It took me 5 minutes tops. It was the single most best easiest mod I have ever done, and I'm so glad I did it. You need a 11/32 drill bit, a 1/8" NPT tap, and a 1/8" NPT fitting w/ 90degree angle and 1/4 hose fitting on other end, Thats all.