Lately i've felt as if my northstar has been a little under power. I didn't think to much about it because i figured i was just getting used to the power or it was out of tune or something. After re-building the motor I never did a HP run on the G-tech to actually check and make sure everything was operating properly. Well, last week I decided to do a G-tech run on the way to an autocross and discovered I was down a significant amount of power.

When i first installed the northstar it was completely stock with headers and it produced 300.5hp and 312 ft lbs at the wheels on a dynodynamics dyno. After the dyno I thought it would be interesting to see how the G-tech compared. With it's current settings the g-tech read 220.7hp and 220.1ft lbs (remember this for comparison later). I then rebuilt the engine with some mild porting done to the heads and a larger set of headers. I had kind of expected to see the wheel horse power bump up to 320-330 on the dyno.

So after my G-tech hp run last week I was astonished to see those numbers had fallen to 171.6hp and 180.7ft lbs. My first thought was that something was seriously wrong with the engine. I ran a compression test and all seemed well. The plugs also look great and the engine runs well aside from the loss of power. At this point I figure it's the lifters leaking down at high rpm because occasionally i have some lifter ticking. But i figure before i tear it all apart I should hook up the laptop and do some data logging.

Almost instantly i found the culprit. At wide open throttle at around 6500 the MAP was at 69.4kPa!!!! No wonder it felt like it was down on power, it was pulling over 28kPa of vacuum. So i looked back in my logs to when i did the dyno tuning and back then it was only pulling 7-8kPa of vacuum. Because of the size of my air filter, in 5,000km's it had clogged up enough to cause significant losses. So i removed the old filter and ordered a K&N. The new filter has about 3.75 times more filter area than the crappy old ractive cone. Here are a couple pics for comparison.




I put the new filter on today and did another G-tech run and data logged it. Now i'm only pulling 4kPa of vacuum at WOT and 6500rpm, and the power numbers have risen to 241.6hp and 233.7ft lbs. Assuming a linear relationship between the g-tech calibration and the dyno i'd expect to see it lay down 329rwhp and 331ft lbs on the dyno. Now comparing back to the small dirty filter, 171.6hp and 180.7ft lbs corresponds to approximatly 233.6rwhp and 256ft lbs on the dyno. So just changing air filters gave me almost 100hp gain!!!!

Moral of the story is ractive cone filters have sh*t all for filter area, and you should buy as large a filter as you can possibly fit.

New to new may not give you that large of an increase but the smaller one will clog up that much faster. Thanks for the info, very good to know.

quote Originally posted by cptsnoopy: New to new may not give you that large of an increase but the smaller one will clog up that much faster. Thanks for the info, very good to know.

Exactly. With almost 4 times the surface area the filter won't clog up nearly as fast. The fact that the air filter needs changing before the oil filter really says something about it's filtering capacity.

Nice info there, and btw how much did you had the heads shaved? (To gain compression). Did you do the intake and exhaust too? Do you have any pics?

THanks!
JG

I heard through the grape vine that a few stickers will help on low HP maybe a v-tec. lol.

Yeah, I don't care what anyone thinks The K&N filters work great.

Vinny

[This message has been edited by vinny (edited 10-09-2008).]

The gain was due to really poor condition of your old one. Although K&N flows a little better than stock, your NOT going to get 100 hp from a filter. A guy in California that has a speed shop did a test on a new Magnum 5.7. For our national LX Club he brought the results of dyno test to our First Nationals. He tested about a dozen different filters and cold air intake systems all on the same car. The biggest gain he got was just over 2 hp and some were actually worse than stock system. I like using K&N myself for only one reason...water dont hurt them and they can be cleaned and reused for years.

I have that exact K&N filter with a 3.5"(?) opening. Reads 98kPa at WOT throughout the range. I'm happy.

BTW, did you scrap the MAF? I bet those are somewhat restrictive and good for a few HP. I just built a new flanged tube.

[This message has been edited by ryan.hess (edited 10-09-2008).]

K&N web site has some formulas for you to calculate the right filter size for your engine size. For V8s it will probably be a little larger than what you may think. I know for sure that many V8s here run a real small filter and they are loosing power for sure. In this area for a V8 I would stuff the bigest one just to be on the safe side.

70hp change from eevn a dirty filter to a clean one is not quite possible

yeah, you would need a clogged solid filter to see that big a differrence. using a cone in the engine compartment on the fiero is worthless. you may as well use a paper filter. you have to get that oujt to the fender area and seal it so you pull in some cool air.
with those calculated numbers you are throwing around, adding cold air will add about 200 hp over an "in compartment" air intake.
in reality you might get about 1 hp per 10 degrees of temp differrence over in compartment vs outside cold air, on a well breathing good motor.

quote Originally posted by THE BEAST: btw how much did you had the heads shaved? (To gain compression). THanks! JG

I didn't shave the heads, I used cometic mls headgaskets from CHRFab.

quote Originally posted by rogergarrison: The gain was due to really poor condition of your old one.

Obviously, the subject was to attract some attention and show what kind of a difference a good filter can make over time.

quote Originally posted by ryan.hess: I have that exact K&N filter with a 3.5"(?) opening. Reads 98kPa at WOT throughout the range. I'm happy. BTW, did you scrap the MAF? I bet those are somewhat restrictive and good for a few HP. I just built a new flanged tube.

MAF is long gone and my opening is 3". I'm looking at increaseing the throttle body size from 75mm to 85mm next.

quote Originally posted by 2.5: 70hp change from eevn a dirty filter to a clean one is not quite possible

It most definatly is possible. Look at the numbers. With the engine only getting 2/3's of the air it needs, it's probably only going to make 2/3's of its power.

quote Originally posted by tjm4fun: using a cone in the engine compartment on the fiero is worthless. you may as well use a paper filter.

Which is why the filter is mounted in the drivers side stage 2 side scoop. All it gets is cold air. The ractive cone filter was paper, it just doesn't look like it.

quote Originally posted by Zac88GT:

Not to be rude, but the first thing to cross my mind when I saw these photos was "WTF was he smoking when he bought that tiny air filter?"

Well at the track I was running a 15.6 with my stock 2.8 4 speed, without ANY filter I got a 15.50, my filter is pretty much on its last leg, so there is something to gain there.

Air filter changes seldom help produce horsepower, they just help you regain what is lost if a restrictive element is used. For instance the 2.8L runs the same horsepower with or without a filter. The right filter makes no difference but the wrong filter does.

------------------
87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by Zac88GT: Obviously, the subject was to attract some attention and show what kind of a difference a good filter can make over time.

More credible measurements probably would've been realized via testing and comparing results for:

1. The dirty, very small air filter
   
2. The new, very small air filter
   
3. The new, much larger air filter

You tested only air filter items 1 and 3. Testing air filter item 2 as well likely would make the testings' results more credible.

quote Originally posted by project34: More credible measurements probably would've been realized via testing and comparing results for: The dirty, very small air filter The new, very small air filter The new, much larger air filter You tested only air filter items 1 and 3. Testing air filter item 2 as well likely would make the testings' results more credible.

Ask and you shall recieve. Thats exactly what I actually did, i just didn't post results from number 2.

Filter__________G-tech HP________G-tech TQ__________kPa drop from 2000-6500
Dirty small_______171.6_____________180.7_____________________28
Clean small______229.0_____________228.1_____________________8
Clean large_______241.6_____________233.7_____________________4

[This message has been edited by Zac88GT (edited 10-10-2008).]

Ok so the engine now has a filter the size it needed in the first place? The one it had to begin with was severely undersized for the engine. Thats a whole different ball of wax than going from just a dirty to clean air filter. It didn't matter that it was K&N either.

I am still surprised that much HP was reduced by restricting air in the first place.

Try a carbed car, close the choke all the way and see how much power you have with WOT, lol.

quote Originally posted by project34: More credible measurements probably would've been realized via testing and comparing results for: The dirty, very small air filter The new, very small air filter The new, much larger air filter You tested only air filter items 1 and 3. Testing air filter item 2 as well likely would make the testings' results more credible.

quote Originally posted by Zac88GT: Ask and you shall recieve. Thats exactly what I actually did, i just didn't post results from number 2. Filter__________G-tech HP________G-tech TQ__________kPa drop from 2000-6500 Dirty small_______171.6_____________180.7_____________________28 Clean small______229.0_____________228.1_____________________8 Clean large_______241.6_____________233.7_____________________4

Thank you for now posting the results from all 3 air filter tests, Zac88GT.

quote Originally posted by 2.5: Ok so the engine now has a filter the size it needed in the first place? The one it had to begin with was severely undersized for the engine. Thats a whole different ball of wax than going from just a dirty to clean air filter.

In the table immediately above, Zac88GT actually is showing that a much larger horsepower increase is realized by switching from the dirty small filter to the clean small air filter (+57 G-Tech HP) than is the horsepower increase realized by switching from the clean small air filter to the clean large air filter (+13 G-Tech HP).

However, for purposes of comparing the horsepower efficacy of a K&N air filter to a Brand X air filter, a more revealing comparison probably would have been that involving a new, large K&N air filter to an equally new and equally large Brand X air filter.

quote Originally posted by Zac88GT: Ask and you shall recieve. Thats exactly what I actually did, i just didn't post results from number 2. Filter__________G-tech HP________G-tech TQ__________kPa drop from 2000-6500 Dirty small_______171.6_____________180.7_____________________28 Clean small______229.0_____________228.1_____________________8 Clean large_______241.6_____________233.7_____________________4

Interesting... Still another 10hp in there.

If you correct the clean readings to 100kpa you get ~250.

quote Originally posted by ryan.hess: Interesting... Still another 10hp in there. If you correct the clean readings to 100kpa you get ~250.

You're running a bored out throttle body right? What size is it and is it just a bored out stock one or a totally different unit? I was thinking about trying to adapt a 85mm LS1/LS6 throttle.

K & N have a formula to determine the minimum size of their filter to run
Id highly recommend looking at that for anyone considering using their products

------------------



87 Fiero GT 5sp with Vortec L35 4300 Turbocharged V6
Bully Stage 2 clutch
Syclone intake manifold and engine management with Moates adapter and chip burner
Air/water intercooler and Devil's Own progressive water/alky injection
50lb injectors, 3 bar map sensor, Walboro fuel pump and Jabasco Intercooler pump
LM1 wideband on custom manifolds and 3" stainless exhaust system
T31/T04B H3 turbo and a S10 caliper conversion.
Murphy's Constant Matter will be damaged in direct proportion to its value
Murphy's Law of Thermodynamics Things get worse under pressure.
Arthur C. Clarke "Any significantly advanced technology is indistinguishable from magic"

K&N even has a very light cloth filter cover that keeps the crap off your filter. Just buy two, put one on and every so often, swap them out and throw the dirty one in the wash.

quote Originally posted by Zac88GT: You're running a bored out throttle body right? What size is it and is it just a bored out stock one or a totally different unit? I was thinking about trying to adapt a 85mm LS1/LS6 throttle.

Yeah, it's a stock one bored to 80mm.

I have always been a beliver in K&N. We used them on the 2 stroke asphalt karts I used to race and they took a heck of a beating. Washed them every race and the motor always worked well.

I have a K&N in every car I own including the IMSA.

Very interesting. Any pics of the cone installed? What's the K&N part number?

------------------



"Friends don't let friends drive stock"

PART NUMBER!!

JG

The K&N part number is RE-0810. I'll see if i can snap an installed pic tonight.

quote Originally posted by Zac88GT: The K&N part number is RE-0810. I'll see if i can snap an installed pic tonight.

I can't really get any good installed pictures without removing the wheel and inner fender but these might give you an idea.
This is throught view through the side scoop.


This is looking from the engine compartment down the intake tube.


And this is looking up from under the car.

What size tubing did you use and do you have any additional pics near the throttle body down towards body of the car?

A couple years ago one of the major hot car mags did the filter comparison thing. On a very healthu V-8 they went from very small to very large filtering, and on a 550 HP motor they got neglegible differences, less than 5 HP. Of course a small filter will reduce performance much quicker as they dirty up.

quote Originally posted by Zac88GT: ...because occasionally i have some lifter ticking. But i figure before i tear it all apart I should hook up the laptop and do some data logging.

...this seems a bit odd to have 'lifter ticking' on a DOC engine...but whatever...

As stated, yes there will be an improvement as other indicated - small dirty filter to a new big filter...

quote Originally posted by madcurl: What size tubing did you use and do you have any additional pics near the throttle body down towards body of the car?

It's 3" tubing.

quote Originally posted by Zac88GT: It's 3" tubing.

Thanks. Once I pass CA smog regs I need to copy your idea (if you don't mind).

quote Originally posted by Mickey_Moose: ...this seems a bit odd to have 'lifter ticking' on a DOC engine...but whatever...

They have lifters.