Mikael

Any chance of this with ceramic bearings and a kevlar belt?



Or should i just start saving for the new XB- something.


I'm waiting for you to chime in Larry

MislMan

You can definitely over-spin the BD-11A head unit, internal belt breakage is usually the failure mode. It all depends on what pulley combination you are using and what RPM you want to limit yourself to. 43K RPM is basically the limit for the BD-11 head unit. Spin it faster (you might get by for short bursts) and you get out of its efficiency range as well as over-tax the internal belt. I wouldn't worry about hurting the bearings but the internal belt is the thing that breaks most often. That is the limiting part of this head unit.

Note that the Powerdyne internal step-up ratio is 3.05, other unit from Vortech and ATI are usually 4.10 (there are exception so you have to check)

Formula for calculating impellor RPM:

(crank dia/SC dia) x RPM x step-up ratio = impellor RPM


Crank pulley SC pulley RPM Step-up ratio Impeller RPM
Diameter Diameter

6.0 3.12 6000 3.05 35192
6.0 2.93 6000 3.05 37474
6.0 2.70 6000 3.05 40667
6.0 2.70 6300 3.05 42700
6.0 3.12 6500 3.05 38125
6.0 2.93 6500 3.05 40597
6.0 2.70 6500 3.05 44056
6.5 3.12 6000 3.05 38125
6.5 2.93 6000 3.05 40597
6.5 2.70 6000 3.05 44056
6.5 3.12 6500 3.05 41302
6.5 2.93 6500 3.05 43980
6.5 2.70 6500 3.05 47727
7.0 3.12 6000 3.05 41058
7.0 2.93 6000 3.05 43720
7.0 2.70 6000 3.05 47444
7.0 3.12 6500 3.05 44479
7.0 2.93 6500 3.05 47363
7.0 2.70 6500 3.05 51398


Crank pullies can be found at http://www.aspracing.com. Usually have to ask for them to be custom made. No big deal, take about 2-3 weeks and cost @ $150. The crank pulley will aid in lowering belt slippage versus the smaller SC pulley.

If you run an automatic you are probably safe since an auto doesn't usually get revved past 6000 often. A 6-speed may be a problem since many 6-speed folks rev their motors too high hoping for more power or simply miss a shift or shift late in the heat of battle. This trip to 6200 and beyond breaks internal belts.

Hope this lengthy reply helps. I will be away from the board for a couple of weeks since I'm having major back surgery tommorrow. If you have real questions please email me and I'll reply when I can get back on a computer (couple of weeks at best).

Also, from my last talk with Powerdyne, if you want more than 6 lb. boost don't be waiting on the XB-1A gear drive head unit for F-bodies. It won't be anytime soon (if at all, since LT1 F-bodies aren't a big players to their operation). The upgrade price would most likely be in the $3K range and you can get a Vortech S-trim set for 9-12 lbs. for that (Tom Byrne is one place) and sell your Powerdyne to recoup some money. If you like the quiet power then go for the S-trim SQ (super quiet) so you get little or no SC whine.

Later ... Larry S.

Erik 94TransAm

Thanks for the help larry. Its for an LS1, so i hope to be making over 400rwhp on 6psi, which is a great amount of power. I just get a little jealous when i see the other guys pushing out 9psi.


Thanks again and best of luck with the surgery.


Mike

MislMan

Just remember that boost readings are a measure of restriction along the flow path. You could have a high boost reading and still make less power than someone with a lower boost reading but with a free flowing flow path (intake, heads, exhaust). This is also why adding good flowing heads can make your boost reading go down but the RWHP & Torque goes up.

On a stock LS1 I'd be more concerned with the head gaskets staying in the motor above about 5 PSI.

Later ... Larry S.

bodie

I've never understood that. If you get better flowing heads it lowers the psi? Isn't the more psi you have the more power times your base power you have (ie 7 pounds would be roughly 150 percent of your base horsepower before boost). So that sounds like if you get better flowing heads it lowers your power.

Omega

More restrictions (stock heads)+ boost (ex: 10psi)= HP1
Less restrictions (better heads) + boost (same setting as before = HP2 [showing less boost ex: 8psi]
Less restrictions (better heads) + more boost (back to 10psi = HP3

HP1<HP2<HP3

Less restrictions (better heads) = more air into the cylinder = more power. [at a lower psi level]

That should make sense.