At first look from a chassis...
At first look from a chassis standpoint, Paxton’s all-new, Novi 2500 supercharger is cut from the same cloth as the tried-and-true Novi 2000. Internally this blower has the same step-up ratio of 3.50:1, and it is capable of moving 2,000 cfm of air. While we’re confident that T-top coupe is stout, we don’t think we’ll see the 1,300 crankshaft horsepower this unit is capable of producing.
After almost 20 years of being considered one of the best all-around superchargers for push-rod-based Mustangs (since hitting the scene in 1994, the Novi 2000 has been a great starter/8-psi blower on stock 5.0s, or a 20-plus-psi unit on radical stroker engines), it's safe to say that updating Paxton's standard was long overdue.
The changes, primarily in the blower's impeller and volute, appear to be for the good, as the new Novi 2500's estimated peak efficiency of 76 percent, is a whopping 5 percent greater than the 2000, that's just a tick below that of Vortech's NMRA EFI Renegade-proven YSi-Trim supercharger (78 percent).
Paxton and Vortech have waged a civil war for many years on the street and strip, with the Novi 2K proving to be a true beast for street-based Mustangs, and the YSi having an edge on Ponies that cover the quarter-mile—especially when they're turned with cog pulleys. Based on the data we studied before conducting this test, it appears the playing field is level now. The dyno will show us the performance differences and the areas where the new blower hopefully shines over its older sibling.
Unfortunately, we're not pitting the Novi 2500 directly against the YSi in this test. Comparing our results against existing data for the Vortech (for engine packages similar to ours) should provide enthusiasts with a good idea of how the two blowers match up.
A switch to cog-style pulleys...
A switch to cog-style pulleys is another change that we’re really excited about, as cogs (for the most part) eliminate the possibility of belt slippage, which usually impacts boost by the Third or Fourth dyno pull. A 30-tooth (blower)/75-tooth (crank) pulley combination was selected, as we believe it will produce boost pressure that is close to that of the original 3-inch (blower)/8-inch (crank) 10-rib belt setup.
While this compressor-map...
While this compressor-map comparison is completely unofficial, it provides a visual concept of how well Paxton’s Novi 2500 (black data) works at 50,000 rpm, when compared to Vortech’s YSi-Trim supercharger, at 60,000 (red data). The 2500’s map clearly shows the blower’s efficiency over a wider span. “On paper,” more power with more boost (the Novi 2500 can produce 30 psi) appears to be Paxton’s concept with the new piece. We think achieving this will be possible, provided the engine is equally as efficient.
This impeller and redesigned volute are the keys to the Novi 2500’s higher rpm and overall efficiency when compared to its predecessor. The OG Novi features a larger-diameter (but shorter 3.53-inch height) impeller. As you’ll see in comparative data elsewhere in this report, the design generates excellent low-end boost. The 2500’s impeller is smaller in diameter and the volute has been lengthened to accommodate its taller (3.75-inch) stance. The changes move the new unit’s max-rpm window well beyond the 75,000 of the Novi 2000. Note that Paxton does not list the Novi 2000’s or 2500’s maximum speeds as being that high. The coupe’s previous 10-rib pulley combination turned the 2000 to an estimated 75,000 rpm, which actually is alarmingly high for that unit. At that speed, the outer edges of the large impeller usually start to wobble, which leads to the impeller touching down on the volute and wreaking havoc from there. This new design alleviates high-speed wobbling, which contributes greatly to the 2500's efficiency (approximately 76 percent) on the high side.