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Gen1 9 sec drag race question

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2
1
Exp. Type
Drag Strip
Exp. Level
3-5 Years
Canada
I have a coyote gen 1 and its on a supercharge vmp gen3r. I have also put bbk1/34 open headers. I want to compete in a 9 second drag race. Am I going to face any back pressure issues on a boost of 30?
 

Mad Hatter

Gotta go Faster
5,317
4,329
Santiago, Chile
😅 Had to laugh! But, in the end, Hp is Hp so what the heck.... No idea about so much boost, or what to do with it, but BBK headers don't seem to be very compatible for the idea. No collector or even a nub of a spike, just four tubes welded together with out a care in the world.
 
6,581
8,586
it also depends on the idea of "boost of 30", there is a huge difference between a belt driven centrifigal blower and a positve displacement (roots) type blower. All the guys running centrifigals are talking about 30psi of boost, that's because those units don't come on immediately, but spool up so the load on the engine is not as much, the positive displacemnt units, like Kenne Bell, spike right off of idle putting a much bigger load on the engine internals, you're all in within a few hundred RPM.. a totally differnt application. The centrifigals are more like turbos, and they create less heat than a roots. Overall, the turbos and the centris will produce more HP because of less parasitic drag, and overall more boost (once you get to where they work) but the roots will always be the king of the street because of their off idle HP characteristics.
I'm old enough to remember when the pro stock national record was 9.90. now days pretty much anything will run in the low 10s and even high 8s. I would simply copy the design of the Cobra Jet drag car that you can buy from Ford.
 
Last edited:

Dave_W

Cones - not just for ice cream
1,029
1,337
Exp. Type
Autocross
Exp. Level
20+ Years
Connecticut
It sounds like you're using this kit:
If I'm reading that right, the kit includes "92 mm / 3.5 in supercharger pulley for 11-12psi" and "Rated at 850 HP and 700 Ft/Lb."

If you run a 315/30-18 Hooser Drag Radial, it has a 26" diameter. Plugging in a 3600 lbs. car weight, 800HP, 6800rpm redline, and 26" tire, this calculator give you a 9.43 1/4 mile at 142mph, with an ideal gear of 3.71 - pretty close to the 3.73 on a GT.

So, if 12psi gives you 850HP and you only need 800HP to run ~9.5, I'm not sure why you want to push 30psi. This page has a list of pulley sizes and boost for the Gen 3R (click the Show More button)
Note that is says "We do not recommend running over 27psi, excessive boost or RPM will void the warranty on your VMP supercharger"

There are a few episodes of Engine Masters where they dyno test with blowers, and there are 2 basic lessons across them all - 1) always use E85 instead of gasoline to get increased charge cooling, and 2) manifold pressure does not dictate horsepower, intake charge mass does. The engine is just a big air pump, and it burns molecules of fuel and oxygen that have mass. Increasing manifold pressure can be one way of increasing the mass of oxygen moved into a cylinder, but so is increasing the density of the intake charge, improving head flow, optimizing cam profile, etc.
 
To bluntly answer your question, if your gen 1 coyote is stock it will not handle 30lbs of boost. Rods in the gen 1 are the weak spot. It is generally accepted that 700ish HP is limit of the engine, thats around 12-14lbs of boost. The good news is, you dont need anywhere near 30lbs of boost to run a 9 second quarter mile. 700 will get the job done with the right gear, tire and suspension. PD blowers are brutal off the line so. 3.31 gear and a 28" tall tire on a 15" wheel is where I would start. Depending on track prep, you need to figure out if you can do a anti-squat set up or if you will have to do the old school squat.
 

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