Test conditions:

Intake was the same, never altered, since we know this can lead to erratic MAF readings. I left it the same in order to see how it was affected by b pipe modifications.

Testing done on same stretch of road, 40-45ºF, 8 - 12% RH. Ambient pressure ranged between 23 - 24" Hg.

I should have gotten area under the curve readings, but I was not interested in that. my only interest was top end power because I'm a ricer. But seriously, that was not in the context of these tests, as I know that these modifications would directly affect top end performance more than anything else.


Make a long story short.

I didn't like the rasp the test pipe gave my set-up (Cattman gen I headers, test pipe, +Cattman B pipe, stock rear).
Added 25" resonator and another 12" spiral 'straight through muffler' for resonators.

Result:

CM-H/stock cat/CM-b/stock rear --> MAF % peaked @ around 6200, flat lined, then began to drop (- ~3%) from 6600 - 7100.

CM-H/test pipe/CM-b/stock rear--> MAF % went up, and peaked @ 7100.

CM-H/25" res/12"straight thru muff/stock rear --- MAF% reaches peak @ 6300, and holds until 7100 (+/-0.5%)

Very happy with the sound, but might delete the 12" muff, since he might be the culprit for the slight loss.

100% no rasp.

Conclusions:

Stock muffler is not restrictive ( )

My computer convulsed (2 spyware programs has a misunderstanding )

My data is limited. Only reason I have those #'s I posted above, is because those are the ones I had written down, the rest are corrupt/damaged.

Data I have:

I only have a short 5800 - 7100 burst from set-up # 2. And 0 - 95MPH from set-up #1.

But, since my current set-up is # 3, I can do more logs on it, and compare with the little data I do have from set-ups #1 & # 2.



Will post data as soon as I gather it.

 

You installed a louvered core resonator? If so return that ****. Get a walker/dynomax resonator if you're on a budget.
http://store.summitracing.com/partde...5&autoview=sku

They sell those at Advanced auto as well under the Walker brand.



So stock cat is hurting you up top... I might need to install my test pipe again then after the equal length ypipe

 

Got it from summit. Walker perforated. Had the louvered core on my old A32 .

Thought of getting a 3" louvered inorder to keep flow path 2.5", but that didn't work out. I knew Cattmans was perforated, and 22", so I though a few more inches might help, and the bullet type muffler was there to control rasp.

 

Very interesting stuff indeed, good job.

Im wondering, did you ever do similar datalogging when you had a stock catback? I wonder how much of a difference in MAF V % stock vs aftermarket catback really makes.

 

I wish I did but back then, I had no means.

I was able to dyno 233 w/ stock catback though.

There's a 30/70 chance I might dyno this weekend.

 

That Thrush unit is what I have on my car as a resonator. Sounds good, at the very least I'm very picky about sound, too. It's relatively straight-through.

 

I got a damn rattle though. Need to hit the uncle up for his grease pit to asses the situation.

 

NmexMAX this is good info you have here. Do you have any other airflow % comparison runs?

Mods- This sort of information would be great to have if compiled into a sticky.

 

I can do some if you guys want when I tune in a couple of days. Such as CAI top end vs. no filter top end. I know a few people that run no filter at the track.

 

kevlo that would be great.

I wish I had some sort of data logger. The most I can do is get an average before and after of peak airflow % (that I would get from my SAFC) after a few mods. Coming up I have things like gutting the IM, replacing stock catback with WSP catback, OBX headers (with 2.5" custom flex and outlet, not the 2 1/8" crap they come with). But my SAFC wont tell me where that peak % is made, so Im not sure how useful this would be.

 

For sharts and gangles.

 

I'm trying to understand this. Obviously we want to keep the MAF % Voltage high b/c it shows that air is continuously entering the engine. So, with different exhaust setups, the MAF % will reflect if the exhaust begins to choke up top? Just trying to understand in layman terms.

 

Yes, but it's not limited to exhaust.

It reflects general air usage, and any change in many items (not only exhaust) will reflect air flow.

Here's a helpful link.
http://forums.maxima.org/showpost.ph...8&postcount=59



** Wow, look at that... I just took a glimpse of that linked thread and saw the Z33 VTC curves on there... .. . . Mine look nearly identical..

 

I got the louvered resonator with 2.5in inner diameter, but the guy at the muffler shop installed it with the louver openings facing the muffler. Isn't that backwards?

 

Supposedly it helps flow. Still, perforated core > louvered core with respect to flow.