John Speake

I am talking about ignition advance tuning with the SharkTuner. Sorry I wasn't clearer, I'll modify my post now....

victor25

Rob, you should basically get about 1lb of boost per 1000 rpms. So a little push on bottom, and then a big shove on top.

rgs944

Watching football so don't have time to tell the whole story but my SC was unhooked for about 20 miles today due to a small clamp issue. Wow what a difference. I really don't know how I ever drove the car without boost. What a dog, I know its not but it really does suffer by comparison. Now I know the big big difference all the way accross the rev range.

Fabio421

When you say it was "unhooked" do you mean the charge air hose was diconnected or was the belt removed from the SC'er?

rgs944

The tube was unhooked so I am sure there was a parisidic draw that normally is'nt there in NA form. So that would account for some of the huge difference.

JWise

The parasitic draw estimate I've seen listed is approximately 1/2 the gain, i.e. if your supercharger is adding 100hp, it takes approximately 50hp to drive it. Combine that with less than optimal fueling and ignition for your suddenly blower-less configuration and you might only be generating 220rwhp or less - not nearly what a properly tuned S4 would provide. As such, I wouldn't be so quick to declare it a "dog".

JakeS2

My ''puppy'' pushes 280rwhp due to wrong mixture, should be getting 290 or so next summer (John Speake, I'm sending my MAF your way son) That's without a blower. This is a ~120tml example.

John Speake

OK !

rgs944

I knew that it was robbing power but that is more than I would have thought.

Fabio421

When I read your post, my first reaction was " Wow! That sounds really high." So I googled it and lo and behold, I came up with this chart. It sure is alot higher than I would have expected. I found it on this website, http://fepower.net/



Horsepower Consumed by Centrifugal Supercharger

Superchargers require power to run, and we thought it would be an interesting experiment to try to determine just how much power was required at various boost levels. To start this test we removed the supercharger belt from the 489" supercharged engine and ran it on the dyno naturally aspirated, to get a baseline horsepower curve. Then, we re-installed the belt and put an adjustable restrictor on the outlet of the supercharger, with a pressure sensor at the outlet to measure the boost. After some experimentation we were able to adjust the restrictor so that at 6000 RPM we got boost levels of 7, 13, and 17 pounds. We also monitored the airflow through the supercharger at these different levels. Boost and airflow at 6000 RPM are plotted on the graph at right, along with the horsepower loss for each pull, as compared to the baseline run. From the graph it is clear that it definitely costs some power to run the centrifugal supercharger

JWise

My info came from one of Ptuomov's posts, as I certainly don't qualify as an expert on these matters. While the exact amount may not be known, it seems pretty clear the parasitic loss is significant.

Speedtoys

FWIW, I turned 370rwhp/340tq at 7psi on the full base kit, no additions/changes to it on the fat 80mm pulley..and weak California water-gas. Pulling a ton of timing up high.


I think there is 10-15Hp on the table with dyno work, and the finished intake system that will soon be shipping.

FredR

Your expectation may well be reasonable but I suspect those charts are not. The compression duty required to move 1800 CFM at 7 psi of boost is about 55 bhp which pro rated to Victor's base kit suggests more like 40 bhp of parasitic loss.

You wll get a more meaningful appreciation of this if you look at John Kuhn's website and look at his numbers. Compare his power to similar boost levels on a supercharger kit and I suspect you will find a difference of about 50 bhp at the same boost level- I wonder why?

Put another way, if Victor's kit required 130 bhp to drive how long do you think his alternator belt would last? I suspect it would snap the first time the motor was wound up. Similarly, if you had to take 130 bhp off John Kuhn's magnificent numbers would you bother with a s/c?

The turbo is effect a free lunch whereas a supercharger is most certainly not.

Even the write up on that test does not make much sense to me. To get those numebrs I suspect the folks doing that test effectively killed the efficiency of the supercharger to get those numebrs.

Regards

Fred

Courtshark

That's pretty solid, though it's interesting to see the hp and torque numbers diverge so much when stock they are about the same. Big hp gain, but only about 75% as much torque gain. And torque is what you feel in the seat of your pants. Any idea for the divergence cause?

Could the timing issues be gas related?

Lizard928

Those numbers are exactly what I was expecting.
Plumb the IC with a proper water system and you will gain more power and be able to put down more ponies!
The fact you have to pull tons of timing up top says the air is too hot. This also means that your AFR will have to be readjusted as colder air is much more dense.