Need help.

[rod2190]

Hello I am running 745 manifold with modded k27. B34 block b35 head was running b34 Intake manifold and switched to b35 intake... Last winter when I had the car tuned I was reaching full boost at 4600rpm put it on the dyno today car wouldn't reach full boost until mid 5k's and ideas on what it could be did a boost leak test no leaks. What could be the issue? If more info is needed let me know. Any answers are much appreciated.

[T_C_D]

4600rpm is way late. You have a boost leak you just have not found it.

[rod2190]

Thanks for the response Todd my buddy mike in Canada said u were very helpful. I use digital boost control operated by ms2 I pressurized from turbo inlet to 20psi only thing I could hear have a slight leak (using stethoscope) was the shaft on the throttle body and it was so little I figured it's normal and if I was to buy a new throttle body wouldn't the boost blow the seals anyway? What are the most common failures on the 745 manifold think the manifold is leaking? I'm just stumped just looking for a few paths to go down to figure out what it could be. Usin homemade waste gate adapter and 38mm tial knockoff waste gate

[T_C_D]

Maybe the junk WG is not dealing properly?

[9mil]

Wastegate!

[rod2190]

Have you guys had bad experiences with them before? I am using genuine tial diaphragm and spring but I will switch for a tial but if issue persists what should I look for? Think the turbo is hurt? Could it be ignition settings? Are 745 manifolds known to leak boost? If so where?

[rod2190]

Does anyone sell a waste gate that bolts up directly to 745 manifold that clears the body of the car that's why I didn't use the stock waste gate I have an e24

[stoney]

Sounds like a wastegate issue as mentioned, do you have a boost controller as well? Is it correctly hooked up?

What about any exhaust leaks?

Whats the turbo condition like?

[rod2190]

No obvious exhaust leaks turbo is a rebuilt modded k27 haven't even got 10k miles on it since its been installed using digital boost controller aem solonoid controlled by ms2. Could cam timing cause boost to come on late? I'm building and holding 20psi just doesn't reach full boost until mid 5k rpm.

[9mil]

Sounds like something aint right on the solenoid... you should be at full boost before that like Todd said. As it is getting to boost at some point (not getting and bleeding down) might not be the WG leaking. Sounds like your MS solenoid duty cycle is off.... have you tried running the graph up to 100% and see what happens?- just take the WG signal off and see it runs to full boost quicker.... be careful though! don't over boost.

[stoney]

Cam timing could very well be an issue, you've swapped heads, so its possible you might be a tooth out, worth checking at the very least.

Good idea on taking the wastegate signal off, simple test to eliminate that area.

[marc79euro645]

What does your ignition curve look like?
Mine idles at 20*,goes to 35* by 3000 rpm, then pulls down to about 20* at boost threshold, and drops to about 10* at max boost. I have an manual boost controller on my stock kkk27. I keep it locked down ,so I'm really just using spring. Mine will start to boost about 3000 rpm in typical pull.

[T_C_D]

What does your ignition curve look like?
Mine idles at 20*,goes to 35* by 3000 rpm, then pulls down to about 20* at boost threshold, and drops to about 10* at max boost. I have an manual boost controller on my stock kkk27. I keep it locked down ,so I'm really just using spring. Mine will start to boost about 3000 rpm in typical pull.

Holy crap. 10* is really low.

[marc79euro645]

"Holy crap. 10* is really low."

Yeah, I would like to try to push that up a little. That's still left over from original "tuning", when I was popping headgaskets regularly.
What are others using at max boost for timing?

[Shadow]

I think if you need to run at 10 advance it's better to just lower the boost because
you're not making power even if it's at 30psi I bet it'll make the same power at 10psi with proper timing.

[stoney]

Get it retuned properly, sounds like its just the timing so retarded being the main issue.

Is the new head secured down on to a MLS headgasket using ARP studs?

[T_C_D]

"Holy crap. 10* is really low."

Yeah, I would like to try to push that up a little. That's still left over from original "tuning", when I was popping headgaskets regularly.
What are others using at max boost for timing?

About 17/18 degrees at the rev limit and 14/15psi. Every car and setup is different though. Certainly 10 degrees is not enough.

[marc79euro645]

Thanks Todd. Looks like I still have some tuning to do. Hopefully more power too.