Geeeeez! Questions... . questions! Some of those I just don't know. You can give BD a call for specifics. To ensure you get correct info, I wouldn't even talk to whomever answers the phone (front desk/salesmen). Immediately ask for "Johnny, Your Turbo Guy" as if you know the fellow. He is the guy that designed their twins. He is a retired Holset engineer and considers working for BD "fun" now-a-days. Really smart fellow and loves to talk so give him a ring.
RDietze said:
that horsepower range being from 450-550?
logically; i don't see how the primary is the bottom turbo and the secondary being the top one?
do you have good turbo whistle out of your exhaust with the twins - even at idle?
I believe their recommended HP range is 350 - 550. They spool pretty fast, so driving around with them at 350hp is not painful at all. During the winter when it is -20*F, I drive around on stock power. Logically you wouldn't think so, but the big bottom turbo is your primary. Small top turbo is your secondary. The Secondary should be a fast spooler as its purpose is to provide some air while the primary gets going, which takes over as your main source of air for top end flow. The incredible air density that you get from dual stage compression is what makes twins cool so much better than a single, and is actually a side benefit of twins that was not in the original design intent back in the day, but realized later. Pretty neat. I use to have a lot of whistle through the exhaust, but added a short 10-inch resonator just after the down pipe to help quiet the exhaust down some (I have a short muffler). I don't have much exhaust whistle after that. Sounds like a jet turbine under the hood though. They are pretty loud.
BCarmicle said:
AK RAM, Have you monitored backpressure with the BD Twins?
Not yet. I have everything to hook up a drive pressure gauge, just haven't gotten around to it. I plan to have it in for next racing season. As hard as I'm running them without an external gate, I probably don't want to know though.
Saccowboy said:
..... cheapest i have found them advertised was for 3900. does anyone know of a place that carries them cheaper? how much did the studs install run you guys that have had it done? i also purchased a banks intercooler and high ram. what will this do to boost pressures and will it allow me to get more hp out of the twins by dropping the egt's?? thanks
You must be looking at Jegs. There are cheaper sets to be had, but that is the cheapest "advertised" price you will find. I would put in a call to PT-Motorsports (
http://www.pt-motorsports.com/ ) and get a quote from them. May be surprised. I installed my studs myself. Figure on about 5 hours labor in addition to the cost of the studs. I have a techni-cooler sitting in the garage also. Install will be a while as I have to grind the BANKS logo off the high ram (can't have that :-laf ) and polish it. I may not even use it. I'll have to see how well it polishes up. John at BD has done a lot of work on intercoolers and could fill your ear full. He designed one for BD that will be out in January. In short, replacing the stock intercooler is a VERY good idea and will yield significant benefits in every aspect... . boost, EGTs, power making ability, if you plan on making significant power. If your engine is stock, don't waste your money.
RDusch said:
AK RAM,What size exhaust housings is BD using on those turbos?
This is about all I know and has been posted here by others. The secondary has a 14. 77cm exhaust housing. The compressor wheel is 56mm and turbine is 84mm. The overall top to bottom is approx 49mm vs. the average Hx35s 39mm. This is why the inducer doesn't have to be as large as your probably expecting. The quicker spoolup comes from a more efficient turbine wheel / housing design and a really tight . 50ar compressor housing.
The primary is the big secret. The exhaust housing is considerably larger than the secondary, which is almost 15cm, but I have no idea what its actual size is. No one will say. It is the largest S300 bearing and turbine housing available (there are many variants) with a custom cast compressor housing and milled billet aluminum compressor wheel (verses standard cast wheels). The wheel is extremely light and spins extremely fast. On our rigs at about 600hp, the B2 (which is an S400) spins at 85 to 95,000 RPMs, and their primary spins at 130,000 rpms. The compressor housing is slightly smaller than a B2, but the smaller housing and lighter wheel allows it to spool twice as fast as the B2 and the higher rpms allows it to flow the same lbs of air per minute than the B2. John is very proud of this turbo and almost had a cow when I told him I was going to replace it. Their first production kits came with an S400 on the bottom, but they felt this primary would better suite more people on average, which means more kits sold. Their S300 primary costs over twice what the S400 costs.
The benefit to higher RPMs with aluminum extended tip wheels is they flow a lot of air (testament to my no smoke runs), but the braw back is higher discharge temps due to the air being compressed so much more than the bigger sets. Adding an external gate would bleed off too much exhaust gas energy and slow the top turbo down to much, which relies on the higher RPMs to generate the air that is expected. Together, this limits usable horsepower on the 3rd Gen trucks to about 500hp (2nd Gens are slightly more), but spool is instant. They will make plenty on race day if you don't mind getting a little warm. At my power level, I see 1480*F max without the water on as I pass through 100mph in the 1/4. I ran last season with my wastegate opening immediately (at less than 10 lbs of boost) in an effort to control over spool. John tells me to keep the wastegate closed until I'm at max boost and my temps will drop considerably. RPMs are really important to this set performing well. I will try that next race season.
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