I finally got the dual exhaust mounted up to the headers and now I understand, with that much back pressure loss, I'm losing boost. My question is, without having a boost guage yet, how much boost am I possibly now losing? The Whipple was rated at 8 psi out of the box, if say I lost 2-3psi with the exhuast and I install a smaller pulley to get back to 8 psi, will I see a hp gain over what I had before the headers & exhuast?

 

Yes

 

boost doesnt = output.

 

Boost = Increased output
Lower boost due to lesser restriction = Same increased output with less increase

Reduction of pulley to retain 8 pounds of boost after mods = increased output from mods + increased output from smaller pulley and, ah F it

It'll go faster, yes.

 

I'm having a hard time getting my head around this. Correct me if this is wrong. I'm making more hp with the headers and exhaust, but less boost. If I change the pulley to get my original boost that I had before the headers and exhaust, I will gain additional hp. If this is so, can I also assume that the motor is as safe from detonation as it was before I added the exhuast mods? And, according to the Whipple install manual, the fuel pump and injectors are good up to 12 psi, should I go with an even smaller pulley, to say, 10 psi? I'm just looking for advice from some of the s/c gurus here. I want the maximum performance without having to take it to the next level and building the bottom end.

 

Boost is simply a measure of restriction.

Reduce the restriction (intake, headwork, cam(s), exhaust) and your boost will drop. But that doesnt mean your output will, it just means that the SC will have to be worked harder to SEE the same amount of boost.

To answer your question, anytime you decrease the restriction in a boosted motor, you INCREASE the efficiency. This is a good thing. The motor isnt being worked as hard, and that will be very niticeable if you keep an eye on the EGTs. They should lower a good deal

Your fuel pump and injector "boost" ratings are irrelevant. I really hate it when they apply ratings like this.

What you really need is a CFM rating. Seeing that a motor is just a very large air pump, and you need a set amount of fuel for every bit of air it injests.

Do you have any tuning device? Or even a wideband?

 

I've got an XCal 2. Forgive my ignorance, but I want to be sure about this. With my new exhaust, the motor is now more efficient, but if I increase boost, I'm back to where I started with the stock exhaust in relation to the efficiency, but I will generate more HP? Of course. I understand that if I do this, it would require a good custom tune. Other than the obvious of getting a bad tune and causing a break, is there a better way to increase HP this easily and cost efficient?

 

Ok can some one clue me in on this equation ---^

 

A good tune is PRICELESS.

Do keep in mind the old saying.

Fast, Cheap, Reliable. Pick TWO.

Slapping a smaller pulley onto the blower will increase its output. But it will also increase it's air output temps (whish also lowers efficiency). And we all know that heat is the devil in any motor.... especially boosted ones.

Also, once you get to the point of increasing boost to bring your respective boost readings back, you are to the point of finding the weakest link. Normally that weakest link is non-forged pistons.

 

Simple:

CFM = output

All an engine is is a big airpump. Get it to process more air, and you will get higher output.

 

You should be able to safely reduce the size of your pulley to achieve pre exhaust psi with minimal change to the programming. (*assuming its been tuned)

928 Motorsports sells pullies on ebay, and they provide you with a formula to calulate supercharger RPM and safe ranges. Check them out

 

Thanks for the info, but I have been talking to Doug @ BamaChips and Whipple and both agree that a 3" pulley would be safe for my application. I pulled the trigger and ordered it. Of course, I understand the tune is the key to this mod. Doug told me the 3V are good for 500hp at the wheels with the stock internals, but feels more comfortable staying at 450.

 

I am getting ready to order a 2.5" for my powerdyne. I only run about 7 psi at top end, around 3-4 psi normal driving (that would be my wife, I see 7 psi alot more often )