Turbo lag questions - kinda long

[islandglh]

Hi Guys, back after a 2 year hiatus...(Restored vw bus). 1986 Omni GlhT - stock setup was super responsive. Installed Spearco over the tranny intercooler system. i have been really disappointed in the response in first and 2nd gear after the install. There is an adapter on the turbo on log setups going to the throttle body. This adapter had a line going to the egr valve and the pvc setup.
I deleted the egr valve. I'm not sure now if the wastegate line also went to this side of the turbo and then to the wastegate solenoid. I currently run a vacuum line from the wastgate can to the wg solenoid, then from the solenoid to the intake manifold for vacuum. Running the mp computer and also a fwd stage 3 15psi computer. I never see more than 11psi in 3rd gear. The motor suffered from blowby and a headgasket going so I yanked the motor, had a broken ringland on cyl.3. Rebuilt the motor using t2 rods and forged pistons. Added a TU60 turbo that was made for the t1 setup. I have triple checked the cam timing, all vac lines are new etc. Car is the same as before. No turbo response really in first unless your
hitting 4500rpm, second the same. Running 2.5" exhaust with stock muffler. No cat. I know the stock muffler is a hindrance but it shouldn't hold it back this much i don't think. Timing is at 12 degrees. Tearing my hair out trying to troubleshoot this. First thought was to try an MBC and see if I get better response. Second thought was to see if I should hook the wastegate can to the other side of the turbo using the port that is there running to the pvc. I see guys sometimes move there cam a tooth ahead, not sure the ramifications on doing this. One other thought I had was the possibility of a boost leak in the intercooler itself but it all looks good although it is probably 25 years old. Any suggestions or ideas would be greatly appreciated. Thank You
Jon

[Vigo]

Issues on the wastegate line would only affect boost response AFTER the wastegate can minimum of 5-7 psi. If you arent able to build ANY boost at the rpms you used to, the issue is probably mechanical like a wastegate flapper not closing all the way or the wastegate actuator losing tension due to a broken spring on the inside or something like that. To confirm that its a wategate issue just remove the vac/boost line from the wastegate can and leave it open air. IF the issue were in the vac lines, this would result in faster and higher boost. Just be careful because if it DOES build boost it wont stop going up until you let off the throttle. I suspect it will not change anything and your problem will be in the wastegate system.

[4 l-bodies]

Jon,
Good to hear from you again. You might want to confirm with Chris at TU about actual compressor wheel size and if there was any turbine clipping. I've seen some clipped turbine wheels that really effected spool. Johnny Spiva had this exact issue at SDAC this past year with his Consulier. His had very sluggish boost. It ended up being the turbo. My similar GLHT with Spearco intercooler is very responsive. In fact I put on a 60 trim compressor wheel and bigger camshaft to kill a little bottom end. When my buddies drive the vehicle they always bounce off the rev limiter in 1st and 2nd because they aren't used to something reving so fast. Definitely something is not right. First thing I thought was cam timing for sure, but you've triple checked that.
Todd

[islandglh]

I do remember getting the quick spool version. Chris has recommended a 3" exhaust. The block and head have been machined under my ownership.The cam timing does look okay but I am thinking of moving the cam a tooth advanced to see if this helps in response. Does this affect my actual timing settings?
Is it a matter of marking the timing belt and cam pulley at #1 TDC, removing the belt and keep tension on it, move the cam slightly towards the front of the car and place the belt back on. What are the ramifications of doing this. Thoughts?

[contraption22]

What turbine housing are you using?

[Vigo]

1 tooth on the cam is something like 9 degrees. You should NOT need to do something so drastic just to get a minorly 'upgraded' stock turbo to spool below 4000 rpm. I would let go of that idea and focus on finding the actual problem rather than trying to band-aid the symptoms.

Since it is still a draw-through system, it's not likely to be a boost leak because any kind of leak big enough to keep you from seeing 1psi boost until 4500 rpm would also suck air in vacuum and cause all kinds of horrible drivability problems on a draw-through setup.

Log setups are VERY easy to visually inspect the wastegate flapper arm on. I would just go out to your car and rule that out before asking more questions about more complicated things like adjusting cam timing that may or may not have any relation to your actual problem.

[4 l-bodies]

Jon,
What is your vacuum reading at operating temp? Should be 18-21 HG at idle. Anything less and you could be looking at tired motor or retarded cam timing. Remember engine is canted rearward several degrees. You wouldn't hardly be the first guy to have cam timing retarded a tooth. How bout compression readings? Operating temp, HEP disconnected, plugs pulled, TB wide open throttle. Should be 135-150 PSI.
Yes camshaft advance would be bumping camshaft towards radiator (front of vehicle). Timing belt orientation doesn't matter. Just reset crank to TDC with timing window on tranny, intermediate shaft by lining up rotor with #1 cylinder in cap, and align camshaft sprocket arrows with cam cap centerline. You should be using a small mirror to see this properly. There is no need to tear off belts and pulley.
Todd

[turbovanman²]

If it did it after the intercooler install, that points to maybe a cheap IC with crappy flow.

Here's any easy way to check cam timing. Get your adjustable timing light, set it to 12 deg, remove the cam plug in plastic cover, start the car and use the timing light thru the hole, you should be able to see the oval slot in the middle, if not, cam is out. If you have a regular timing light, set the timing to 0 and check the cam timing.

[4 l-bodies]

If it did it after the intercooler install, that points to maybe a cheap IC with crappy flow.

Simon, Spearco intercooler kit. That means Spearco intercooler core. Unless there is a rag stuck in one end of intercooler, flow through intercooler isn't the issue. That cooler is efficent to 275 HP or more.
Todd

[turbovanman²]

Simon, Spearco intercooler kit. That means Spearco intercooler core. Unless there is a rag stuck in one end of intercooler, flow through intercooler isn't the issue. That cooler is efficent to 275 HP or more.
Todd

Sorry, missed the Spearco part,