BD Tow Twins

[daveg]

Does anyone have info on BD's tow twins for the 3rd gen?

I installed a set on a 04. 5 and am seeing the boost gauge peg past 60psi with TST on 4X5. So far BD has not been able to resolve this issue.

I am not seeing this problem on my own 2nd gen.

 

[AK RAM]

Sure.



Did you preload the wastegate actuator on the secondary by backing it out three FULL turns (not half turns as most end up doing)? The top turbo is set for 40psi as it comes for use as a single. It has to be adjusted correctly for the twins kit. This is the most common mistake as most swear they set it correctly when in fact they are starting with only 1&1/2 turns preload, which would put them at over 75 lbs of boost with little fuel (not good).



Beyond the first full three turns, each half turn should drop boost roughly 5psi. Seems I remember a max of only 54 to 58 lbs of boost with the TST by itself set per the instructions. I see 67 lbs on occasion as I sit now and 63/64 lbs daily with the BD twins.



Are you using a digital boost gauge or a gauge that records max boost like the X-Monitor? Sounds like it is a 60 lb gauge... . is it?

 

[daveg]

The top turbo wastegate came preset at 40psi as you said. I ended up adjusting it to start opening at 15psi and made a stand-out wastegate cover so the wasegate could open more. The stand-out wastegate cover helped and is what I also did on my own setup to keep boost below 55psi. Also, the stock cover leaks when the exhaust brake is engaged. BD's gasket didn't help. When they punch the dimple in the wasegate cover, they warp it.

The gauges are Pricol.

 

[AK RAM]

It looks like you did everything right.



The only suggestion I would have is to maybe have the wastegate start to open even earlier to help get boost under control. The 3rd Gens do build boost slightly faster than most 2nd Gens. On mine, the wastegate starts to open at 10 lbs (actually just a hair below 10), and I still see 67 lbs of boost. If yours is starting to crack at 15 lbs, add in a few more lbs for over spool before the gate can get boost under control, and I can see where you may be hitting 70+ lbs of boost rather quickly.



I tried to make a stand-out wastegate cover for mine as well, but couldn't make anything that worked well while keeping the edges flat enough to still get a good seal. I ended up staying with the dimpled cover and that little dimple only lets the flapper open about half way. I bet the stand-out cover really helps with keeping drive pressures low.



You wouldn't be interested in making another cover and selling it to me would you?