2.9 RR + 4lb lower = 14 psi????

[BLWN]

Any body running a 2.9 and 4lb lower how much boost are you making? I am peaking about 14 psi as soon as I get into boost and then it tapers off to 11-12 psi. I searched a little and seen some suggest the boost dump valve mod from nitrous pete. Do you think this would help? Any other ideas? I don't think it is belt slip, I have the 3pc idler and changed to a shorter belt even though I see minimum belt dust.

Thanks,
Brad

 

[Rwick7]

I see about 13 or 13.5 with just a 2.93...somehting doesn't soudn right. How is the weather?

 

[78mphgpr]

In sticky Florida air (100% humidity), my 2.93 only is staying between 15 -14.

 

[sambandit]

Sounds about right, I get that same boost with a 2.93 & 6lb. I don't think you have slip, the boost just WILL drop off like that. Nothing you can do about it!

 

[tommygun]

My 2.80 makes 13lbs by itself

as for teh dump valve just unplug it and it will do the same as the mod and takes about .25sec LOL

 

[stangfan]

6# lower/ stock upper/2 1/2 catted (2 cat. vs 4) H-Pipe/stock cat-back with 2 1/2 inch weld-in flows makes 14 - 15.5lbs of boost based on the ambient air temp/humidiy.

What's your exhaust setup, air intake setup (cold-air, etc), air temp/humidy when you tested? Also, what kind of boost was your car making when it was stock (Seems like they all varied based on sever params.?)

All these params. make a difference...

 

[lRageATMl]

sounds about right to me, I have a 2.75 upper and a 4lb lower and I see about 16-17psi.

 

[geepaw]

HEy guys...I'm relatively new to the mustang world....whats a 2.92 2.9 etc.. is this the pulley diam? what's the 4lb about as well?:shrug:

thanks!

 

[SStupid]

answers

Originally posted by geepaw
HEy guys...I'm relatively new to the mustang world....whats a 2.92 2.9 etc.. is this the pulley diam? what's the 4lb about as well?:shrug:

thanks!

The 2.93, 2.9, 2.8, 2.7 are all pulley diameters, in inches, for the upper pulley on the snout of the blower. The stock diameter is somewhere around 3.5 inches. I can't recall exactly. The reasons for switching to a lower diameter pulley is to increase the number of RPMs that the Eaton is turning. The more revolutions the blower turns, the more boost you get, until the blower becomes inefficient (around 16K RPMs at the motor's 6500RPM redline). After the 16K RPM mark, the blower requires almost as much horsepower to turn it as it's making (parasitic loss.) The 2.93 is the smallest diameter upper pulley you can run without reaching the 16K blower mark.

The 4lb lower is a complete pulley/pulley cage kit sold by Metco. The kit comes with either a 2, 4, 6, or 8 lb lower. You increase the size of the lower pulley to increase boost. The "4lb" designation means just that: you get 4 extra pounds of boost at full throttle and hopefully through the entire RPM range. These kits are very expensive, but you don't have to worry about belt-slip that is seen with the 2.93 and smaller diameter pulleys. There is a rumor that the lower-pulley kits cause some sort of destructive harmonic that causes main bearing wear. I have not seen data on this. Hope this helps, and enjoy your Mustang!

 

[geepaw]

thanks for the info!

I'm goin thru withdrawels...my 03 is in the shop for the tick issue :??:

my 98 civic is my beater, handles great..but with 1/4 the torque...man I miss her!:cryying:

 

[BLWN]

I have the Borla Stinger Catback as the only exhaust mod and the Steeda CAI. I have the bypass unplugged, but was thinking that maybe the boost valve is not adjusted properly.

It was only in the low 70s with not too much humidity. I know that alot of people loose boost up top and I didn't think mine would be any different, just figured I should peak at more then 14 psi.

Thanks for the responses.

 

[BLWN]

Any other ideas?