4.0L Whipple performance

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I recently installed headers and 4.0L Whipple on the car with 4.0" pulley and 10% overdrive crank pulley. This was "supposed" to result in about 17-18 psi max. Was running 16 psi with the stock 2.3L and could count on max boost below 3000 rpms. Now at 4000 rpms I'm only seeing about 13 psi, at 6000 15-16 psi. The boost curve is more like a centrifugal blower than a twin screw, at least from what I've experienced on the past. Is this normal for this blower? I was able to find another dyno graph from a car running this blower but with a 23# pulley, and he hit max boost at about 3200 rpm. Just wondering what others are seeing.

Todd
 

2011 gtcs

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I don't have a big Whipple, But I do have a big KB. I have also noticed that the bigger twin screw SC don't reach max boost at low RPMs like the TVS does, My KB makes around 15psi on the hit and climbs to 19psi at 6k right before I shift.
 

stangfreak

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Im pretty sure bigger motors have different rules but in the 03 cobra world, anytime you guys go with a bigger blower, you need to spin them at there efficiency level. big blowers need big boost. so yes they will build up boost like that.
 
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Here is a dyno graph of a 4.0L on a 2012 GT500 running 23 psi. It is hitting max boost at about 3300 rpm. Are you saying this is because it's running at higher boost and will thus hit max boost faster? My boost curve is nothing like this.

Todd

4.0L_whipple_boost_curve.jpg
 

2011 gtcs

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It's not the boost level I'm concerned about, it's the latency in reaching max boost. The headers shouldn't effect that.

Todd

I noticed when I was running a 3.75 upper pulley on my KB I would only see 13psi till almost 5k then it would finally climb to 15psi. And now with the smaller pulley the boost does seem to come up faster. Maybe try and put a smaller upper pulley on and see what happens. are you running the 4.0L on a stock 5.8?
 
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Yes, stock 5.8. That's the problem, the max hp level I'm getting, around 790 in 4th, is at what I feel is a safe limit for the motor. The car however feels slower on the street below 5k rpm than with the TVS which is where I'm at 95% of the time.
 

kierrea35

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That's the only problem with a bigger blower. If you don't run big boost, it's gonna feel like a dog at lower RPM. I had that problem with the 2.8KB on my previous 03. It was seeing 16lbs due to the headers.
 

serickson1

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The dyno graph looks the same as my 4.2 KB with a 4" pulley…..I was at 25psi by 3800RPMs and made 1100+ @ 7000RPM's…..if you look closely at the graph it looks like max boost is closer to 3700 than 3300...
 

2011 gtcs

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The TVS is a TQ monster blower and makes great power as well. The big twin screws need to be spun hard before they start making any big power. I just finished my ARH headers today and the car feels so much more responsive, I felt after the KB I lost so much low end TQ and the headers seem to have brought that back.
 

02GTKB

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The TVS is a TQ monster blower and makes great power as well. The big twin screws need to be spun hard before they start making any big power. I just finished my ARH headers today and the car feels so much more responsive, I felt after the KB I lost so much low end TQ and the headers seem to have brought that back.

How was the install of the headers? I am doing mine once my kb comes in
 

kierrea35

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How was the install of the headers? I am doing mine once my kb comes in

Not sure if it's the same as others install them, but I removed the motor mounts to install. The passenger side had tons of room,while I had to finesse the driver side a little. All my bolts were pretty easy to get except the bottom middle driver side bolts. They were a real bitch because of the hard water line that runs near the block. It could have been a problem due to the 2" primaries.
 

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How was the install of the headers? I am doing mine once my kb comes in

It was a nightmare lol. I ended up dropping the K member and that made things super easy, but I still wouldn't want to do it again.
 

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