Weird boost gauge readings - solved!!!

[ateick]

Finally got some snow here so took my Viper out with newly installed hurricane 190 kit. I added a AEM AFR and boost gauge. Boost gauge is connected to the multi-T coming off the throttle bodies. When at idle I'm only getting a 0 reading. I know I should be in to vacuum. When I accelerate or rev the throttle it goes into vacuum. Drops back to 0 once at a steady speed. Never goes above zero into boost.? Any thoughts?

 

[sledheadgeorge]

Have to have a load on the motor before it builds up boost

 

[ateick]

Have to have a load on the motor before it builds up boost

I have. I have been for a test drive. 1/4, 1/2, WOT -- no amount of throttle will take the gauge past 0 and in fact applying throttle does the reverse, it moves into vacuum until you come off the throttle again. Steady throttle will keep it at 0.

 

[ateick]

The Hurricane instructions indicate to "Install supplied vacuum hose manifold to rear nipples as shown in pic. Install vacuum hose from multi-T on vacuum manifold to blow off valve, PC5 map sensor optional boost gauge and install plugs in unused ports."

I've done all that. Is this the best location to get a boost reading? Is that perhaps why I'm getting the strange readings I'm getting. But no that doesn't make sense because the MAP sensor and BOV needs to see vacuum and boost as well. Ugh.

 

[ateick]

Ok tested some things last night. Boost gauge works properly with bike pump and suction. Disconnected everything at Multi-T coming off the vacuum lines attached to carbs and plugged in just the boost gauge and NO VACUUM OR BOOST at all when running. I get the same condition I described above.

Went back to Hurricane's two pager of instructions to look at the image of what ports on the carb to attach to for vacuum line (because that's what I followed) and compared it to MPI's detailed instructions and the suggested ports to tap into are COMPLETELY different.

Hurricane (doesn't even look like the correct carb to me)

MPI instructions. Looks like my carb and it even has the one line coming off the furthest port on the carb on the left which I believe runs to a pressure sensor.

HELP!
I don't know the function of all the ports on the carb. Anyone have any insight (before I tear this whole thing apart) whether the way I have connected the vacuum lines (again as per Hurricane's instructions in the first pic) would cause a no vacuum/boost situation since it is vastly different from the MPI pic?

 

[MrSled]

I would connect it like the 2nd pictures shows..

 

[MrSled]

Have to have a load on the motor before it builds up boost

I agree.. if the motors not being loaded it will not show boost. You will not see any boost on the stand free wheeling the sled.

 

[ateick]

All righty. I believe I have it figured out!

If you are doing an install of a Hurricane 190 kit DO NOT follow the diagram provided in their two page instructions when connecting the vacuum lines.

I went home at lunch and tore this thing apart and looked at the ports that Hurricane had suggested to use. Below is a picture of the two ports on one of the carbs. The upper left one is the Hurricane suggested one, the lower right is the correct one that MPI highlights very clearly. The suggested port seems to be one-way or have some sort of check valve maybe?

Now just got to put it back together and everything should be fine.

The scary thing is that I went for a rip with it hooked up to the wrong ports so of course the BOV wasn't working meaning the intake side was super pressurized when off throttle and the MAP wasn't getting any info.
Note to everyone - BOOST AND AFR GAUGES SHOULD BE CONSIDERED A MUST with these kits or things can go sideways fast.

 

[MrSled]

All righty. I believe I have it figured out!

If you are doing an install of a Hurricane 190 kit DO NOT follow the diagram provided in their two page instructions when connecting the vacuum lines.

I went home at lunch and tore this thing apart and looked at the ports that Hurricane had suggested to use. Below is a picture of the two ports on one of the carbs. The upper left one is the Hurricane suggested one, the lower right is the correct one that MPI highlights very clearly. The suggested port seems to be one-way or have some sort of check valve maybe?
View attachment 151090

Now just got to put it back together and everything should be fine.

The scary thing is that I went for a rip with it hooked up to the wrong ports so of course the BOV wasn't working meaning the intake side was super pressurized when off throttle and the MAP wasn't getting any info.
Note to everyone - BOOST AND AFR GAUGES SHOULD BE CONSIDERED A MUST with these kits or things can go sideways fast.

exactly the best way to learn.

 

[ateick]

Ok super frustrated. Looking for help. Tore everything apart. Changed the vacuum lines to the ports suggested. Hooked everything back up. Still reads 0 on Boost gauge at idle. Still not showing any vacuum. Is the multi-T the best spot to tap into for a boost gauge? At a loss here.

 

[MrSled]

Ok super frustrated. Looking for help. Tore everything apart. Changed the vacuum lines to the ports suggested. Hooked everything back up. Still reads 0 on Boost gauge at idle. Still not showing any vacuum. Is the multi-T the best spot to tap into for a boost gauge? At a loss here.

You have to be missing something or you boost gauge is shot. I have several sleds teed in just like MPI and it works.

 

[hellflyer]

Wish I could help with this but I took it apart in March and can't remember where the hoses where hooked up. I didn't have a boost gauge either. But I'm not sure if would see enough vacuum to register at idle.

 

[TPAY243]

Follow the instructions per Hurrican, when you get it back together check your BOV, I'll bet ya it's junk i went through several of the cheap plastic ones before I bought a good one and since then no more problems.

 

[MrSled]

Wish I could help with this but I took it apart in March and can't remember where the hoses where hooked up. I didn't have a boost gauge either. But I'm not sure if would see enough vacuum to register at idle.

should show at least -2 to -3 vacuum at idle.

 

[TPAY243]

Not if the BOV is seized up or stuck, the piston in the valve will get stuck open and won't let it pull vacuum at idle.