Weakest Link

1/4HORSE · 02-10-2002, 02:31 AM

I've got a 2000 gt with some simple mods(pulleys, throttle body,etc.) I'm planning to buy a blower some time this spring or summer.(don't know which brand or type yet) I've read at many sites that both the tranny (t45) and the bottom end of the 4.6 is kinda weak...

What I'm trying to find out is #1 How much boost could I run ? #2 How much hp and/or torque can the engine and the tranny withstand ? #3 Is there any preforance to which brand or type of blower I should look into i.e.(vortec,paxton,roush etc...roots type or centralfugal) Thanks for all your help.

Hammer · 02-10-2002, 06:58 PM

The T45 and the rear end are not weak, they just weren't designed for applications with high-torque numbers...

My stock T45 lasted about a year with about 450 hp at the crank. I'm currently looking at a Tremec TKO for replacement.
The stock rear end could use some work right about now too, so I expect to do some work back there also in the spring. (Bearings, Shims and seals)

As far as blowers, the amount of boost you can run on a near stock setup is usually determined by what type of blower you are looking for.
With a roots type, I would stay around 6 psi.
A centrifugal blower, about 8 psi.

I would advise some engine work before going any higher than that.

As in any blown application, watch your compression ratio and be safe out there...

95GTS · 02-11-2002, 03:02 PM

One big thing that'll help your tranny is an aftermarket shifter. The rear end, like Adam said, is a good one. The 8.8 is actually pretty strong. When you go to really sticky tires like slicks is when it starts to take a toll on the rear end.

The roots blower will give you more torque right off the bat because it doesn't have to spool up like the centrifugal. But the centrifugal has the advantage on the upper end of the hp range in the higher rpms. Both will help greatly with hp and torque. Just depends on your combination/application of mods and use of the car as to whether you need the power a little sooner or a little later. Just look at Adam's stang running 450hp with the centrifugal.

blue00gt · 02-11-2002, 05:07 PM

As far as the stock bottom end of the 4.6 goes, 400-450hp is about the limit from what I hear.

1/4HORSE · 02-12-2002, 06:52 AM

O.K. thanks for the info. But one more question. If I buy a roots style blower you say to run about 6psi...how come the centrifugal can run at 8psi ? Is it because the roots makes so much more low RPM torque or is there some other reason , and will the aftermarket pulleys effect the performance of the blower ?

Hammer · 02-12-2002, 10:05 AM

The recommended PSI differences are just in the nature of the beasts. One of the reasons is certainly the high torque output at low rpms of the roots style.... along with other issues that others may be able to explain better than I....
Remember that output doesn't necessarily directly respond to boost numbers. Case in point: An intercooled setup can produce more horspower at 8 psi than a non-intercooled unit at 10 psi.

As fas as pullies go... Almost every blower setup I know of either comes with their own set or expects you to use the stock pieces.

02-11-2002, 05:07 PM	#4
blue00gt Mustang Addict Join Date: Jan 2001 Location: McKinney, TX Posts: 1,294	As far as the stock bottom end of the 4.6 goes, 400-450hp is about the limit from what I hear. __________________ Strike down the unroadworthy! 2000 GT Atl. Blue: '03 Cobra motor - 465rwhp/473rwtq, T-56 6-speed, full MM TA/PH & tubular K-member suspension, Saleen body, 17" Torq-Thrust II's, M/T ET Street radials, and lots more '94 Rio Red Cobra: All the bolt-ons, 3.73s

02-12-2002, 06:52 AM	#5
1/4HORSE Registered Member Join Date: Feb 2002 Posts: 6	HAMMER O.K. thanks for the info. But one more question. If I buy a roots style blower you say to run about 6psi...how come the centrifugal can run at 8psi ? Is it because the roots makes so much more low RPM torque or is there some other reason , and will the aftermarket pulleys effect the performance of the blower ? __________________ QUARTERHORSE My Mustang

02-12-2002, 10:05 AM	#6
Hammer AKA "Dr. Evil" Join Date: Feb 1999 Location: South Fork Ranch Posts: 1,721	The recommended PSI differences are just in the nature of the beasts. One of the reasons is certainly the high torque output at low rpms of the roots style.... along with other issues that others may be able to explain better than I.... Remember that output doesn't necessarily directly respond to boost numbers. Case in point: An intercooled setup can produce more horspower at 8 psi than a non-intercooled unit at 10 psi. As fas as pullies go... Almost every blower setup I know of either comes with their own set or expects you to use the stock pieces. __________________ Uncle Sam "What the hell is up with all the gauges? Calling Captain Kirk, your ride awaits... Phasers on stun...."

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02-10-2002, 02:31 AM	#1
1/4HORSE Registered Member Join Date: Feb 2002 Posts: 6	Weakest Link I've got a 2000 gt with some simple mods(pulleys, throttle body,etc.) I'm planning to buy a blower some time this spring or summer.(don't know which brand or type yet) I've read at many sites that both the tranny (t45) and the bottom end of the 4.6 is kinda weak... What I'm trying to find out is #1 How much boost could I run ? #2 How much hp and/or torque can the engine and the tranny withstand ? #3 Is there any preforance to which brand or type of blower I should look into i.e.(vortec,paxton,roush etc...roots type or centralfugal) Thanks for all your help. __________________ QUARTERHORSE My Mustang

02-10-2002, 06:58 PM	#2
Hammer AKA "Dr. Evil" Join Date: Feb 1999 Location: South Fork Ranch Posts: 1,721	The T45 and the rear end are not weak, they just weren't designed for applications with high-torque numbers... My stock T45 lasted about a year with about 450 hp at the crank. I'm currently looking at a Tremec TKO for replacement. The stock rear end could use some work right about now too, so I expect to do some work back there also in the spring. (Bearings, Shims and seals) As far as blowers, the amount of boost you can run on a near stock setup is usually determined by what type of blower you are looking for. With a roots type, I would stay around 6 psi. A centrifugal blower, about 8 psi. I would advise some engine work before going any higher than that. As in any blown application, watch your compression ratio and be safe out there... __________________ Uncle Sam "What the hell is up with all the gauges? Calling Captain Kirk, your ride awaits... Phasers on stun...."

02-11-2002, 03:02 PM	#3
95GTS Git jiggy Join Date: Oct 1999 Location: MO USA Posts: 865	One big thing that'll help your tranny is an aftermarket shifter. The rear end, like Adam said, is a good one. The 8.8 is actually pretty strong. When you go to really sticky tires like slicks is when it starts to take a toll on the rear end. The roots blower will give you more torque right off the bat because it doesn't have to spool up like the centrifugal. But the centrifugal has the advantage on the upper end of the hp range in the higher rpms. Both will help greatly with hp and torque. Just depends on your combination/application of mods and use of the car as to whether you need the power a little sooner or a little later. Just look at Adam's stang running 450hp with the centrifugal. __________________ 1967 Mustang Coupe