Jump to content

2.9" pulley vs. 3.3".....


FuelSlut

Recommended Posts

I am sticking with my 2.85 pulley but am hoping to make a quantum leap this weekend by installing bigger injectors and getting a fresh tune from Zippy.

 

I know what you mean though about running out of money. I just want to get the most from my setup and I think I'm close... :chevy:

Link to comment
Share on other sites

  • Replies 30
  • Created
  • Last Reply

Sorry. Guess my 2.85" pulley is a 'tweener... got from South Florida Pulley HQ. Basically a 2.9."

 

Just like Fuelslut when I dove into the Radix world I didn't realize the '04 fuel system wasn't gonna cut it with a smaller than 3.3" pulley.

 

Gonna bite the bullet with SVO injectors and try to get her running right. :P

Link to comment
Share on other sites

I did run a 14.1 with a 3.3 pulley on stock 20's but hardly tread. I pulled off a 14.3 on 22's with hardly any tread, so there might be a gain with that pulley.

 

this still does not make sense to me... i cant quite follow it... please explain this

 

thanks

george

Link to comment
Share on other sites

I have ran the stock 3.3 and the 2.9 on the dyno with my set-up. I was able to pick up 30HP and 50lbft of TQ. The only other mod on the two runs was my custom intake and some tuning. I was actually talking to Richard (BigTex) about them a little while ago.

 

FWIW, I see great improvements in going to a smaller pulley. I have a 2.8 and a 2.75 sitting on the shelf. I just need more fuel! I go lean in the upper ends (450's in HP and 480's in TQ).

 

I also have one of my dyno runs on the same graph as Rick (dounome) for a great comparison of Radix vs. Vortec on our trucks. I am just waiting for his permission to use his graph (just being nice :happysad: ).

 

:driving:

Link to comment
Share on other sites

tune that is currently in my truck at the moment if from pcm for less... meant for the 2.9" but lacking timming for the 2.9" so i should be alright...

What do you mean meant for the 2.9", but lacking timing for the 2.9"?

 

If the tune is meant for the 2.9", then that means timing, fueling, VE, PE, etc.., is meant for the 2.9".

 

is any of this making any sense to anyone? or does it just seem like im insane? im getting a lot of feedback as if i didnt go from the 3.3 to a 2.9 pulley at one time...

I think you're confusing yourself. Just go run the 2.9 pulley and let us know how it went. That 2.9 isn't going to break anything, so stop sweating it so much. You're not venturing on uncharted waters, or anything.

Link to comment
Share on other sites

I think you're confusing yourself.  Just go run the 2.9 pulley and let us know how it went.  That 2.9 isn't going to break anything, so stop sweating it so much.  You're not venturing on uncharted waters, or anything.

 

Ive been running the 2.9" for months now... if you read the first post in this thread i am going to see how it runs with my current tune and modifications but with the 3.3" pulley that is designed for the blower to run at peak efficiency. It is in my belief of theory that i am (with the 2.9) wasting 50 horse power.

 

i'm not confusing myself, i'm just not quite sure i am explaining it properly for people other than myself to understand... because...yes... i do confuse myself at times, this is not one

Link to comment
Share on other sites

Alright George,

 

When I ran the 14.1 my truck had the radix with the 3.3 pulley on it. At the time, I ran it at the track on stockers with 30 % tread or so left. I figure boost is 5-6 psi. I then changed the pulley to a 2.85 from South Florida Pulley HQ with a boost gauge. I had about 8 psi then. I then made a home made ram air intake, changed my exhaust, changed my clutches, 160 stat, and had a tune from Bryan. I figured with the extra power the 22's shouldn't have mattered that much. Any how, my best run was still a 14.3. The weather stayed about the same too. Hot and humid :banghead:

 

I am not sure about the specifics on the radix, but from what you are going by, you may get some gains. From my experience, I would think so too. I hope this clears up something.

Link to comment
Share on other sites

Ive been running the 2.9" for months now... if you read the first post in this thread i am going to see how it runs with my current tune and modifications but with the 3.3" pulley that is designed for the blower to run at peak efficiency. It is in my belief of theory that i am (with the 2.9) wasting 50 horse power.

The 3.30" pulley is because of the 10:1CR, which doesn't like higher boost, not because it is the peak efficiency. Initial issue of the Radix for our truck was a 3.10" pulley.

 

It all goes by the blower rpms. You need to pull up the map for the MP112 compressor. your shift rpms, or the high end of your engine rpms, dictate the blower rpms.

 

For instance:

7.75"(crank pulley) / 3.30(blower pulley) = 2.35

 

2.35 X 6000(shift rpm - not sure what yours is) = 14,100 blower rpm

 

It would be 16K rpm with the 2.9".

 

If you refer to a compressor map, you can see where 14k rpms falls with respect to it's efficiency.

 

Your assumption that you are losing that much hp from going to a 2.9 from a 3.3 would go against the times that others have done with the stock pulley over the 2.9. If you did go and check and found that you're making a better time with a 3.3 pulley, either your tune is hosed, or your blower is. Because the logic just isn't there, IMO.

 

I have run the 3.30", 2.90", and 2.75" with my Radix. The 2.90" made the most power because it didn't create all the heat issues and loss of power from it, that the 2.75" does.

Link to comment
Share on other sites

well.... I was wrong... very wrong... ran a 14.1153 @ 94.55 mph... that is 7 tenths slower than what i was running with the 2.9" pulley..... Zippy... we got some work to do (if ya dont mind) - needless to say, i slid the 2.9-er back on tonite.... what a waste of time, but oh well... maybe someone could get some use out of this information... (as if it were news to anyone anyway)

 

well... there ya have it folks... i need to uhhh "get muh tune on"

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.


×
×
  • Create New...