i thought one of the ideas behind a public forum was so that one could ask a question, the right people could answer it, and later if someone else had the same question they could do a search and find the answer?
thats what i get for thinkin...
dave posted right after you did - he did not respond so i guess he is not going to
somethin tells me i am not the only person wondering why BD only offers two choices to put above the primary, a med large 64 or a tiny 57
i really liked this thread, or thought i would when i saw the title. thats cuz i am gonna splurge for twins here shortly. it seems that for my power level a 62 over a 75 is the way to go
make it a great night...
don
Don, I did see your post and was going to reply last night but it was almost midnight when I wrote my last reply... yaaaawn!
I get this question about the sizes we use and why... and honesty I do not like releasing the sizes out personally, let me explain why...
As you know we have one of the top engineers JT working with us and BW to come up with designs that have wide efficiency ranges and single chargers that can be upgraded correctly upgraded to twins.
Most of our turbo designs are based off the S300 and S400 turbo charger. We have a full turbo facility on site that allows us to make in house modifications to these design. Which make comparison between other 64's or 57's apples and oranges. With these facilities and technology our goal is a "best of both worlds" scenarios.
The biggest problem I find, especially on these forums is a lot of guys giving advise based on what works on there truck. Which in most cases is true, but because a particular set up is working on one truck/set up, it does not mean it will work as good on another truck/set up. Example... one truck double stacked no injectors that is used for towing, versus a single stack with large injectors used for racing. Same power range, totally different turbo needs!
What I am getting at here is that we engineer our turbos for the widest possible efficiency range. There may be some single and twin charges that spool faster and there may be some single and twins set ups that flow more CFM on the top end but I can assure you that Super B's Single and Twins will give you the best balance of both, "best of both worlds".
How does this answer your question "why we use the sizes we do" because they help us achieve the balance we are looking for with the right combination of components...
The reason I do not like releasing turbo sizes because a lot of people get misled by them. Most of the time users do not fully understand how the different sizes compare, especially when you start adding extended tip compressor wheel into the mix. For example... in our Tow Twins some say they are too small based on size... some say our Super B Single is the same as stock based on size. Truth is with the correctly matched components a smaller wheel spinning at a faster RPM using the extended tip compressor wheel will produce more CFM than a larger wheel without sacrificing spool up time... So bigger is not always better... how much time to you spend with your foot on the floor fully taxing that turbo versus accelerating from a dead stop light to light? Unless your racing full time, probably less than 1% of the time. Well this is Comp Diesel so for arguments sake lets say 10%.
Hope this helps Dave