LSA blower only making 4psi

[VodeAn]

I just want to run this by everyone and see if my thoughts make sense.

I have a LSA blower on a LS3, the blower is 10% overdriven at the crank and fully ported w/ a 90mm throttle body, but the setup only makes 4 psi.


Motor specs:
stock ls3 compression 10.7:1
stock ls3 heads
LS6 Cam
4" Cold Air Intake
1 7/8 longtubes
x-pipe
no cats

Now I realize that boost is a measurment of restriction and that a bigger, better flowing/breathing motor will make less boost for a given supercharger setup compared to a smaller / poorer flowing motor.

My line of thought is that the stock LSA blower on a stock lsa makes 7-8 psi
Adding longtube headers to a stock LSA usually makes the boost drop by 2-3 psi
A slightly larger cam also makes boost drop by a couple psi
A 10% overdive adds 2-3 psi

So I guess my question is as follows:
Am I really flowing enough air that even with my 10% overdive I'm only seeing 4 psi? I thought I'd be around 6-7.
If so, I'm considering changing the upper pulley to spin the blower even faster, future plans include a magnuson heartbeat but I was hoping this would keep me happy for a while.
Does anyone have data as to how much air a stock LSA blower provides at certain RPM's on stock pulley? I know I can look at logs of a stock CTS-V to estimate this but I'm hoping someone may have some flowbench data.

I haven't checked for vacuum leaks with a smoke machine yet (because I don't have one), but I can't hear or see anything obvious.

Thanks

[cc-rider]

Yeah that does seem a bit low. You've already mentioned everything that came to my mind for what might affect it. One thing you might want to look at is the bypass valve. It may not be shutting properly and letting some boost leak out. I don't have a LSA so I'm not much help on this, but I seem to remember reading some threads/posts about how the bypass valve on a LSA has some adjustments that have to be set properly. Check into that. I may be wrong.

A good resource for you in this would be ADM Performance. They are some guru's on the LSA.

Good luck.

[VodeAn]

Thanks, I thought I set the bypass correctly, but I check it.

I forgot to mention it has the ZL1 lid too.

[rao]

If you have all of the components of the stock bypass valve in place the bypass valve won't fully close unless the solenoid is energized (which is what happens on a LSA) or you can remove the solenoid and the bybass will work properly without any electronics.

[Dustins]

Do you have any pictures of it removed?

[rao]

The part removed attaches where the PCV hose is zip-tied.

[supergt99]

im going with bypass valve. im seeing 10psi with my lsa blower 2.75 pulley, with ls9 cam and long tube headers.

[VodeAn]

I have the solenoid vacuum lines connected but the electrical connector is not plugged into anything.

Okay so the consensus is for me to remove the electronic solenoid and it's lines and run only the one line you have there into the port between the rotor pack and throttle body? or remove the solenoid and still run both lines?


If so I can do this tonight/tomorrow and report back.

[VodeAn]

im going with bypass valve. im seeing 10psi with my lsa blower 2.75 pulley, with ls9 cam and long tube headers.

What motor is the LSA blower on with that combo?

[ABADZL1]

http://www.lingenfelter.com/mm5/merc...8#.VP3IiSI5BhE

[jmyers09]

I had the same problem after installing a ported blower with 2.5upper pulley. I removed the boost dump solenoid and plugged related ports and went from 4 to 11.5psi. This is on a 11.5:1 ls3 with 233/247 cam.

[VodeAn]

Changed to the setup rao posted,
Running vacuum line only, it's fixed alright, I blew the tires off at 70.
Thanks everyone

[larrySS]

Changed to the setup rao posted,
Running vacuum line only, it's fixed alright, I blew the tires off at 70.
Thanks everyone

I have an LS3 with LT headers and 233/248 627/610 cam , what do u think ? I will get a good boost with LSA blower ??

thanks

[VodeAn]

What's the lobe separation angle and overlap on the camshaft? Also, will you be running stock upper and lower pulleys?

[stonemonk9]

https://www.youtube.com/watch?v=hYQ1jZ1l1tU

There is a adjustment for this....

[nighttowl]

What's the lobe separation angle and overlap on the camshaft? Also, will you be running stock upper and lower pulleys?

+1

What cam?

if its not a FI spec'ed cam, you are most likely boosting part of your air fuel mixture out the exhaust

[VodeAn]

https://www.youtube.com/watch?v=hYQ1jZ1l1tU

There is a adjustment for this....

My issue had nothing to do with the adjustment. An improperly adjusted bypass valve would not have been fixed by swapping vacuum lines around.

The problem was I had the factory electronic control solenoid hooked up in-line, but no ECM control over the solenoid since this blower is swapped onto G8. If you hook the vacuum lines up like a stock CTS-V, but don't have control over the solenoid, the bypass valve will never fully close under acceleration. Setting up the lines like rao posted is the correct way to fix this issue.

There is another way I discovered to fix the issue using just the pressure side, but it does not allow the bypass to open during cruise, which defeats the purpose of having a bypass.

[daniel6718]

anyone still have the pictures rao posted?

[SUTTERERMAN85]

https://www.bing.com/images/search?v...x=4&ajaxhist=0

Hook up your bypass like this. It works correctly and will be in bypass in cruise.