How much boost does a stock M62 Gen III make?

[Drewster]

How much boost does a stock M62 Gen III make?
Is is ok to T off of the Charcoal canister line to measure?


Andrew

[J Wikoff]

You can tap off any of the lines that come from the vacuum tree by the BCA.

[Drewster]

thats what i thought for the tap. i was seeing 2psi max at WOT. i thought that was really low. did come out of vacuum quick but i had expected around 7psi. i dont know what the M62 can put out. (vac was good at idle,18-20 in.hg)

[J Wikoff]

There might be a leak in that line or the canister bleeds off positive pressure? Cap the line off to exclude the canister and try again. You should get about 7 psi. The gauge shows 0 when the engine's not running, right?

[willwren]

Moving to the proper section.

There are some possible questions related to the fact that this is a swap:

1. Is your evap system tied in to the vacuum manifold as it was stock? This would be 'post inlet', not pre-inlet? Any boost indication would only be seen at the vacuum manifold closest to the nosedrive.

2. Is your BCA and BCS properly controlled and connected both in terms of vacuum and in terms of the BCS solenoid (electrical)?

3. What are you using to measure the 2psi of boost? Be specific, links if possible.


Test your BCA mechanically using the red link in my signature.

[Drewster]

instead T ing into the Fuel Pressure Regulator sense line as shown in the links, i T'd into the next one up on the vac tree which is the Evap charcoal canister.
Boost control actutator tested on the bench before install and after intall solenoid was tested as per links and all looks proper
all vac lines are stock configuration. im seeing good vac
good posibility about the evap canister bleeding boost. i will check without the canister connected.
Confirming that i should see about 7psi boost.

[Drewster]

i also used a vac/ 30 psi mechanical pressure gauge. i then added another pressure gauge to confirm my first gauge was proper. pulled vac with hand held tester on test rig to confirm no leaks.
ill post again after running without the evap canister line.

[willwren]

If the BCA and BCS are working properly, and you don't have belt slip, it's physically impossible to have too little boost. It's not possible for a supercharger in our application to physically under-boost by itself. The only possibility is boost CONTROL. That comes down to the BCA function primarily. Boost indication may be another factor.

[J Wikoff]

Good point about the BCS. Take the vacuum elbow off the bottom of the BCA and test your boost again. If it goes back up, check the wiring to the BCS. If the wiring is fine, replace the BCS.

[Drewster]

looks like i had T'd into the line for the Trans modulator which also T's into the primary vacumuum block when i did my first test.
tested direct without the T and now showing 5psi and climbing to 6psi at the top of the RPMs.

ill also see if i get any more boost with the BCS bottom vac line off
thanks for the tips.
Andrew

[J Wikoff]

You should get a few more psi than that. Stock gen 3 pulley, right? Any other mods? Roller rockers or anything else that helps move air in/out of the cylinders will lower the boost because there is less "boost stacking".

[willwren]

Adding your swap and mods to your signature would help us a ton.