USB B1 With HT3B

[Lucas5477]

I Have a Bell USB and just got a new HT3B. Has anyone tryed this combo with twins?



Lucas

 

[Hohn]

I've been researching twins to the point where almost every vendor and person who already has twins is sick of me calling and PMing.



I REALLY like a USB on top because of the high pressure ratios it can generate. IIRC, Pius also has a WSB which is still on the map at 58psi!



With twins, I figure your total airflow (lb/hr) comes from the big charger. The PRESSURE that the air is delivered at comes more from the small charger.



I think of it this way: start with a high pressure-ratio small charger (like a USB) that can do over 4:1, then multiply this already-high ratio with your large charger. Thus, an HT3B running at 2:1 give you 8:1 overall. (2*4=8). If you have a larger charger that can efficiently go 3:1, then you are at 12:1 overall, which is plenty for well over 100psi of boost.



This means the large charger has to be big enough to feed the small one at whatever pressure ratio.



Personally, I think an HT3B is too small to match with a USB. I'd go B2, Ht4B/C, or Big Brother.



Even if not perfect, the Ht3b will spool quickly with the USB and give you a lot of air. The high PR of the Pius turbos gives you a lot of options. You can always swap out the 3b for something bigger later.....



The idea is mass quantities of cool air. I think your combo will ROCK!



Let us know how it goes!



Justin

 

[Lucas5477]

Hohn, Thanks for the info. I just started to look for parts and find out what I’m going to need to do this project. I think that the WSB would probably be a better choice with the HT3B. But I already have a USB so that's what I’m going to try. I just hope that it combined with the HT3B will spool up somewhat reasonable.



I did talk to pius a couple months ago and he told me that we would have to do some different things to the USB to set it up for twins. I think he was meaning that he wants to take off the internal wastgate and go with an external wastgate set at like 22-25 psi on the USB not sure what else he wants to do to it maybe a different exhaust housing. He also said that he wants to use another wastgate after the big turbo to wastgate it too.



Right now I’m just trying to do as much reading on twins and what the different setups are and what people have been having luck with. I’m not sure how I’m going to have it all set up yet. But I already have a USB and a HT3B so those are the two turbo I will be using in the set up.



Lucas

 

[Hohn]

It's complex, but a dual-external gates are the way to go IMHO for twins.



The gate for the big charger can be much smaller than the gate for the small one, as the bypass flow on the large charger is going to be much less.



I think Most singles being converted to wins use should go to a smaller housing with an external gate. You'll also gate it at a lower pressure. Remember, your twins will never spool faster than the small charger or its own. That means you want a little smaller housing to give you spoolup to spare, then pop open the gate to prevent choking the flow.



Justin

 

[Cooker]

Sorry if I am a little less educated when it comes to twin setups but could you please explain to me why WG'ing the big charger is a good idea? Just so it is easier to control the peak boost of the engine? Thanks.

 

[Jim Fulmer]

Sorry if I am a little less educated when it comes to twin setups but could you please explain to me why WG'ing the big charger is a good idea? Just so it is easier to control the peak boost of the engine?



Mine is a good example, I could use a gate in my hot pipe to slow the B/B now, overall control in this situation, let the engine make the exhaust and if you don't need all of it then bleed it off to the exhaust pipe.



Jim