This post will necessarily be long, but I will make every attempt to be concise.

In March of 2007 I finished up with all of the go-fast boltons. I have an 05 6MT sedan, and at the time I had a stillen airbox, mrev+, 5/16" spacer, ichiba headers, kinetix resonated test pipes, stillen first generation sedan exhaust, tuned utec, jwt flywheel, and ngk one step colder iridium spark plugs. Three months later, in June of 07, I dyno'd at the local dynojet sans Stillen airbox, and put down 266/248. Here's the graph:


A week ago I went back to the same dyno. I've already posted about it, but let me recap: I lost ~13hp at peak versus my last dyno. The dyno has not been recalibrated. I had originally thought I was running the stillen airbox a year ago, but looking through my notes I have confirmed that I was running the stock airbox. So no change in mods. I was running 245/40/18 tires a year ago(26.0 inches tall), versus 245/45/18 today(26.7 inches tall). The only other change to the car was the fact that I had to replace a dead battery about a month ago(maybe 1200 miles ago). The final numbers yielded 254/246. Here's the chart:


I posit that the difference was primarily due to the stock ecu's tune being out of whack, with the rest due to tire pressure and tire size. I didn't realize until a couple of days later that my tires were only 25psi.

Here are the two graphs overlaid. Notice that I am running leaner now than a year ago(with the same mods):


After that day, I came home and swapped out my mrev+ lower plenum for my stock lower plenum, but I kept the spacer. Yes, the mrev+(and mrev2) has proven to show nice gains throughout the powerband for most everyone, but I only saw roughly half the gains as most of the publicly posted dynos. Besides, I have not seen any pre-post dynos for fully-modded cars; most were for near-stock. Plus I wanted to wrench on my car a bit. While I was at it, I threw in my stillen airbox with a freshly cleaned filter.

A week later(last Friday), I went back to the same dyno. The only changes being inflated rear tires(40psi vs 25psi), the stock plenum, and the stillen airbox. My numbers were 259/239. Here's the chart:


After that pull, while the car was on the dyno, I pulled the stillen unit and replaced it with my stock airbox(with k&n panel filter - cleaned). The new configuration yielded 266/247, very close to my baseline from last year. Here's the chart:


And here's a chart plotting the stock airbox versus the stillen airbox(stock is blue line):


And finally, here is my latest configuration(stock plenum, stock airbox, bad tune) versus my baseline from last year(mrev+, stillen airbox, tuned):


Although the peak numbers are almost exactly the same, the curves are very different. Analysis in the next post.

 

I put together a couple of excel spreadsheets to aid me in numerical analysis. The cool thing about dynojets is the utility of the Winpep viewer program. If you have your run files, then you can use this free program to chart all kinds of things, and event export the runs to csv files. Right now on my laptop, I have right at 120 run files. So I can do all kinds of analysis.

To help me figure out the distribution of the power, I decided to average the horsepower and torque across the rev range I would see at the drag strip. Assuming I see full traction at 4000 rpms in first gear, I would take 1st all the way to redline(which I don't - another topic). That would put me entering 2nd at 4300rpms. Taken to redline, I would enter 3rd at 4900rpms. From there I would enter 4th at 5500 rpms, until I crossed the finish line at about 6000rpms or 105mph(that's based on averaging 104mph through the final 66 feet). Exporting the run files in 50 rpm increments into Excel allows me to tally only this specific rev range.

Based on last year's baseline(with mrev and stock airbox), I would average 243.02hp/225.69tq. With my new baseline(stock lower collector, stock airbox, bad tune) I would average 238.18hp/220.82. Basically, with my current tune and stock lower plenum I will have lost an average of 4.84hp/4.87tq across the drag racing rev range for my car.

I also compared my latest baseline to the numbers put down with the stillen airbox, using the stock lower collector for both. With the stillen airbox, I averaged 231.31/214.47, or a net loss of 6.87hp and 6.35tq.

Those are the numbers and analysis. No interpretation and no opinion. Take it for what you will.

 

Sucks to see the Stillen airbox loose power

 

thanks for the detailed review.

 

Thanks for sharing your experience and posting up the dyno's. It seems like the curves are better when you were modded. I would like to see a new dyno of your car with the current mods plus a tune. You can't expect too much from modding the VQ. FI is the only way to go if you really want to see some gains.

What set-up do you think will get you the most gains? Any future mods?

Nice 13.2 run...

 

The car is done for a long time. I *might* boost it once its paid off, but that's two years away, and will depend on my money situation then.

I could tune the car myself, but I have no reliable way of obtaining a/f numbers without spending $400 on the Cipher or $400 for the utec tuner wideband. I could sell the utec for maybe $650 and get an uprev tune(local guy does them for $400), or I could go back to sharif for a touch-up tune for about $200. Or I can leave it as it is, got to the track one more time, and sell the utec then and not worry about a tune.

 

I've posted all of the facts but I tried to not interject any opinion into those posts. Now I'll do so.

I *love* the sound of the stillen airbox. The induction noise is just awesome. After like 60% throttle, it just howls. And at about 5500 rpms, my exhaust sounded unbelievable. But I could definitely feel a difference. There's no way its going back on my car.

And I've been driving with the mrev+ since Feb of 06. At full throttle, I can feel the difference in torque under 4k rpms. But after that, my car definitely feels stronger with the stock collector, despite what's shown in the dyno graphs. Also, at part throttle with the ecu still in control(closed loop), the car drives much better and has more part-throttle power than it did with the mrev+.

Now I hope nobody takes this the wrong way. I am in now way saying that either the mrev+ or the stillen airbox do not work. The stillen airbox at least, just doesn't jive with my other mods and my tune. Others may have completely different results.

Both should be for sale in the marketplate soon.

 

Maybe the a/f ratios on the 2nd dyno plot was the cause of the lost hp. Did you ever find out if the "tune" was lost after the battery went dead?

 

Utec retains the tune. But I highly doubt the stock ecu is anywhere close to where it used to be.

What confuses me is the fact that the a/f curves strongly resemble eachother; it's as if the stock ecu is deliberately running .5-.75 points leaner than last year.

 

It's odd that those two changes resulted in more power but almost the same leanish a/f ratio.

 

Thanks for the analysis. I was going to state that the AFR change could have affected your performance in your Before/After runs. But the AFR resemble each other very closely. It does seem as if it runs just a tad leaner with the Stillen airbox. That might have possibly have affected the slight change in power.

On a side note, im glad im doing all my before & after runs on the same dynapack I started off in; I don't have to worry about the additional variables of the tires/wheels.

.

 

^^^ Totally. I'm half-tempted to strap on my drag wheels and dyno with them on. They're 26 inches tall, like my old tires, and they're a good 7lbs lighter each(with tires). Then again, I don't run my DR's at 40psi

 

Bummer about the Stillen airbox

Can't say I'm too surprised though. I wonder if results would be similar on my '04 coupe 6MT.

As you mentioned, I, too love the sound the Stillen makes. Might be tough going back to stock, but if I could really gain 5+whp/torque, it might be worth it.

 

Interesting bro! Whats up with the lines being all wavy like that(looks rough, needs smoothing)? I assume it is your engine management? I am used to seeing graphs look like this more. It reminds me of runs i see when its done on stock ECUs.



So i take it you didnt compare your stock airbox and stillen on the same day either?

Have you messed around wtih the smoothing option?

 

Notice in the upper right corner, that dyno chart is using smoothing 5, the ones he posted is smoothing of 0. Thats the reason right there.