Any 2.9 gen 4 guys here? Pulley and boost questions

I’m trying to nail down the pulley combo for my car without having to buy a ton of pullies. I thought I had it figured out but it looks like all the data I was looking at were for older gen 2’s and gen 3’s. The gen 4 is supposed to make 1-2psi more with the same pulley than the gen 3, not sure what the gen 2 to gen 3 difference were or if there were any as far as pulley and boost numbers.

I’ve got a ATI 15% lower on the car and the 3.25” that came with the Whipple. Plus my car has longtubes and I’m at sea level. Whipple tech support says the gen 4 2.9 makes 16-17psi with the 3.25” and stock manifolds and the guy I spoke to said he heard 4lbs for a 15% lower. Everything I’ve read says 5-6lbs for a 15% and 3-4lbs for a 10%. I believe they also gave the same boost estimate with the gen 3’s from the old sales pages I’m finding so I don’t 100% trust their figures.

Regardless, if we say 16-17psi - 2psi for long tubes + 5psi for 15% lower it’s 19-20psi total. Maybe as much as 21psi if the 15% does make closer to 6lbs or if the longtubes don’t quite knock off 2lbs.

Can any 2.9 gen 4 on 5.4’s owners chime in with what they’re seeing with what pulley combo and also please note if you have longtubes, cams or head work.

Also even if you don’t have a 2.9 gen 4, if you have another generation 2.9 or a 3.4 or a similar size KB and you ran with both a stock lower and a 15%, how much boost increase did you see?

Thanks.

2011, whatever Gen 2.9 this is, 1 3/4'' LT's, stock 2.9 pulley, stock 5.4 lower pulley.
Boost = 19.40
.

That's going to be a gen 2. That and 3's are what I'm finding all the data on. Gen 4 data is non existent it seems.

My street car is with my Tuner now for a tune revision and check up, expected to be done in the next couple of days. Whipple 2.9 Gen 4 with 3.00" pulley, stock lower balancer, Twin 65mm throttle body, stock long block, stock exhaust with Borla axle-backs. I'm expecting 18-19#s easily at 6000 RPM at sea level; previous Gen 2 with 3.00" pulley was roughly 16-17#s at 6000 RPM.

SCGallo2 said:

My street car is with my Tuner now for a tune revision and check up, expected to be done in the next couple of days. Whipple 2.9 Gen 4 with 3.00" pulley, stock lower balancer, Twin 65mm throttle body, stock long block, stock exhaust with Borla axle-backs. I'm expecting 18-19#s easily at 6000 RPM at sea level; previous Gen 2 with 3.00" pulley was roughly 16-17#s at 6000 RPM.

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Look forward to some numbers

Just looking at blower ratios, which levels the playing field on supercharger revs, you'd need a 3.75" pulley with the 15% to be close to the 3.25" and stock lower balancer. If you needed another couple psi, to compensate for the headers, you'd probably be looking at a 3.5".

I think I'm going to have beefcake send me an ATI "stock diameter" balancer which is actually about 6% overdriven. I think that will put me where I need to be. See where I am with that and the 3.25" pulley and go from there. I can get a 3.125" or 3.0" to bump the boost up to 17-18psi if I need to.

Speaking to Whipple they said a 3.5" pulley should clear the hood but a 3.625" wouldn't... that's not a hell of a lot of clearance lol. So I really don't want to go any larger than the 3.25" that's on it now.

2.9 Whipple, 10% lower, 2.85 upper, should be 21-22psi at sea level. 18psi in Denver (5280’ elevation). Ask me how I know...

Radron2626 said:

2.9 Whipple, 10% lower, 2.85 upper, should be 21-22psi at sea level. 18psi in Denver (5280’ elevation). Ask me how I know...

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What generation Whipple?

Redneckbmxer24 said:

What generation Whipple?

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It is a Gen 2. Not sure what the difference is for Gen 4-5, I know they make a lil more hp per boost, as they are more efficient. I am just not sure if the pulley sizes create the same amount of boost or not.

Radron2626 said:

It is a Gen 2. Not sure what the difference is for Gen 4-5, I know they make a lil more hp per boost, as they are more efficient. I am just not sure if the pulley sizes create the same amount of boost or not.

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Thanks but I’m looking for data for gen 4’s. They make more boost with the same pulley combo than the 2’s and 3’s. Pretty much all of the data out there is for 2’s and 3’s.

SCGallo2 said:

Whipple 2.9 Gen 4 with 3.00" pulley, stock lower balancer, Twin 65mm throttle body, stock long block, stock exhaust with Borla axle-backs.

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Nearly 20#s at 6400 RPM at sea level in above configuration, and boost ramps in quick. I will post dyno results in a separate thread.

My brother has a gen 4 2.9 with a 10% ATi lower and a 3.25 upper making around 17psi elevation is around that 2200ft. Car is 2007 GT500 supporting mods are jba long tubes, off rod x pipe (no cats), Jlt 123mm, ford racing 65mm twin cobra jet throttle body, FIC 1000cc, twin booster pumps. BJ tuned it