STILLEN Exhaust & Gen 3 Intake Dynos - 18hp Each!

wstar

I think that's the line of thought Denny is headed down, yes. If the stock intake is already cold air (sounds like it is - honestly I haven't looked to see if the stock boxes are really sealed off from the engine bay and sucking only air from the front ports (the ones that you would enlarge for running the Stillen Gen3 pipes)), and it flows sufficient CFM already to match bolt-on exhaust mods and a little ECU tuning, then intake mods aren't really going to help if you're going to tune the A/F mix in the ECU anyways.

Now, that being said, colder air is always a win, and perhaps the location of the Stillen G3 inlets (filters really) gets access to colder air than the stocks ports hidden back there on the sides of the radiator, especially on a real highway. There are some variables in play there with highway-speed wind coming in the throat of the car, air pressure under the car and near the front intake, and turbulence to deal with, etc.

However, given the impressive dyno results, I lean towards the idea that at least some of those gains on the dyno must be coming from leaning out the A/F mix like Denny's talking about. Hopefully soon we'll get some numbers to sort this out.

Denny McLain

My main experience also is with small block Chevy's, owned three modified import turbo cars but that's been a while and I'm sure a lot has changed. What I've learned from fuel injected small blocks (unlike carburetor cars) is you can have a garbage can for a throttle body and unless it's not getting enough air...so what? Same for intakes. Enough is enough.

This stuff really is a science and it takes a certain amount of air (cfm), at a certain fuel/air ratio, at a certain rpm to make X amount of power. A cooler charge will be denser containing more oxygen per liter of air. Other things like humidity and barometric air pressure also factor in. SAE uses 77 degrees air temp as it reference point.

A stock Chevy LT1 motor makes about the same amount of power as the 370Z and needs about 550cfm at higher rpm to make max power. In other words... No matter how much air you show the motor, it will not pull anymore than 550cfm as that's all it can use at its given power level.

No question there is a benefit from not drawing warm air from the engine compartment (why there is a difference in SAE and Standard hp scales) but any ram air effect is debatable. Some say nay while others say yay. My personal feeling based only upon mid 60's NHRA stock class rules is there is some beneficial effect. They made cars run one class higher if they had some type of scoop or ram air system.

Also did not physically remove the air box but basically stuck my hand down in it and noticed air was coming from somewhere below and in front of the radiator. Besides the filters being a bit on the small side, looks like a well designed system from the factory.

Can it be improved upon? Sure. How much.....dunno. There are effects from turblence, velocity and swirl that show up inside the heads but man, that air is moving tremendously faster. Dunno?

One dyno session to get a baseline really doesn't tell ya that much except what the car is making and wideband 02 readings. What I do know is the cars are very rich and my experience in dyno tuning is proper fuel/air settings are king. Screw the timing, I want somewhere around 13 to 1 fuel air depending upon what the car wants.

If the intake is a restriction, it would show up more after adding the higher flow cats that should increase power, increase the need for cfm of air. Got house guests, but I'll try and get the car on the dyno this week. Do the same trick: three runs for new baseline, pull the filters and lid. Check to see if power or fuel/air has changed.

Denny McLain

Ok........ Let's try posting dyno sheets again.

370Z new cats - Y-pipe picture by dennylmclain - Photobucket

If someone can host the dyno sheet, I'm gladly e-mail them a copy to post.

Anyway, fresh from the dyno and frankly I'm confused like a big dog.

Drove to the dyno shop, the car sat for 20-25 minutes and it only gained 5 hp and lost torque over best run of the first session. Not real impressive by any means. Whoopie do, that's what I get for $1,100.00?? Let it sit five minutes and another pull. Identical to the prior. The kicker that had me confused is the fuel/air was much better almost a full point higher. ??

OK, so if that's all it gonna make, pulled the high flow filters and it sat a good 25 minutes. Made another pull and I'll be damned, picked up 13 hp instead of 5 (294.6 rwhp)!! What is up wid dat? Maybe the filters are an issue now that it breaths better from the exhaust?? OK the filters back in waiting about 10-15 minutes and it made 292 rwhp.

The bottom line we feel the car is very sensitive to heat soak and w/o a water temp gauge, pretty damn hard to get consistent numbers to compare. The conjecture as to why the first two pulls were lower was the car sat with the hood closed and may have heat soaked the intake manifold. Letting it sit with the hood open more than likely had a fairly significant cooling effect on the top end. Basically did the same damn thing last time with the first run just opening the hood being the worst.

So.......there ya go. Basically a 13 hp gain and a slight gain in torque from high flow cats and Y-pipe, but that could be a tiny bit more. OH...high flow filters also. (a waste of money)

We looked a little closer at the intake and the general feeling was the car could benefit some from a straight path shot of air. Asked what car they see the most gains out a cold air intake and it was the LS1 F-Body. They said they typically see a 7-12 increase in hp on those cars. Said if they got 10 hp, they had a good day.

This particular shop is owned by what amounts to my old full time mechanic when I was sponsored by another shop. Pretty salty and the shop produces some pretty fast race cars.His feeling being the car is so sensitive to heat, was to try two lower heat ranges of spark plug and see if that would make it more consistent. Worth a try.

Still feel with the range of numbers just from the amount of heat you see in the engine, the numbers can be fudged quite a bit of someone were to desire so. Especially if the intake was iced. The car varied by 9 hp from the first run to the better ones on each dyno session. Hey......it gained 9 hp!!

Frankly a bit, but not completely discouraged. Will try colder plugs and tuning to see what happens. Unless there is some magic in the variable valve timing tuning, not sure if people are going to see the gains they maybe had hoped for. Like me for example.

Dunno..we'll play some more and see.

azn370z

Did you install the berk cats? Which y pipe did you install? I'm assuming the 18 hp berk dyno was too optimistic??

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2010 k23
H&R sport springs / Spc rear camber arms / SSR SP1 / Berk cbe / Varis cf lip / Nismo S-Tune side skirts

Denny McLain

Yes, they were the Berk cats and JIC Y-Pipe. Got them locally from:

Outperformance Shop - 2009 Nissan 370z Performance Parts

Evidently my car was the first one to try the JIC Y-pipe and obviously the test monkey for fit as they're not on their web site yet. The Y-pipe is extremely well made, the welds are fabulous and fit perfect. Will do a bit of welding myself on occasion (when and if I can get my hands on a welder) and was very impressed with the work. Top shelf stuff. (so are the cats)

Rarely have I been able to duplicate manufacturers results as you always see "best case' outcomes. As mentioned, the was a 9 hp difference just in underhood engine temps and heat soak. Makes it pretty easy to add a fudge factor.

The other issue I'm having is going through a learning curve on what the car likes and how to best dyno the car for consistency. That's OK. I'm learning. There may be a little bit more power from the cats and Y-pipe, but frankly that is about what I was expecting. The radical change in fuel/air was not expected and has taken me back a notch.

Dan is the owner of Outperformance and he had a great next move suggestion: Remove the stock exhaust section after the Y-Pipe, dyno and see what the effects are to determine how efficient the stock exhaust system is. Think that is a great idea as usually on modding a car the first thing I do is make sure plenty of air is capable of going in and out eliminating any weak links. Once I'm comfortable no obstacles are present, then focus at other areas.

import111

That is a damn good idea. I would like to hear the results of that.

Denny McLain

Speaking of damn good idea. Still waiting to hear from Stillen on the intake. The dyno's not even warmed up yet.