H22toF20

I'm stumped. Their should be no way you didn't make power with a 70mm header back.

Gernby

I forgot to mention, the wideband sensor that was used at the S2000 dyno day was inserted into the muffler tip. The value that it showed was about 0.5:1 leaner than what my OEM primary O2 showed in the datalogs. When I asked the dyno operator if he thought his sensor was accurate, he said that it typically reads about 0.3:1 lean. That means to me that my primary O2 reads about 0.2:1 rich. Therrefore, I think the actual AFR;s that I was hitting for these tests was about 13.0 - 13.4.

Gernby

[WRONG]Well, I think a good theory is that all Hondas are NOT created equal. Maybe the stock exhaust on the RSX's really sucked. I'm sure some Hondas probably get gains from big exhausts, but I think it's clear that a well tuned '06+ AP2 with bolt-ons will not show significant gains from it. I think Honda just designed a really friggin' awesome stock exhaust![\WRONG]

Somebody send me an HFC!!!

bpaspi

[QUOTE=H22toF20,Jan 13 2011, 10:56 PM] I'm stumped.

Gernby

Manifold pressure will always drop as RPMs rise, since vacuum will always be created when the engine draws in air at a faster and faster rate. Wadzii did a test recently where he fabricated a custom intake manifold with a large diameter throttle body and a large diameter intake to see if that would give gains, but I believe it showed no gains.

The DBW AP2's have larger throttle bodies from the factory that are the same size as the SOS big bore TB. I even tried out one of SOS's big bore DBW TB's, and it showed no gains.

I'm sure there is some sort of bottle neck somewhere, but I'm certain it would have to be INSIDE the engine. In the same way that I've proven that this 70mm exhaust and test pipe does NOT make gains, I have proven that my intake DOES make gains. I've also shown that my car made more power than all 10 of the other NA S2000's at our club dyno day even though a couple of them had much more significant mods than mine with FlashPro tunes. The fact that mine made over 150 ft-lbs at 4K RPMs with only an intake, injectors, test pipe, and tune is amazing to me!

Gernby

BTW, here are some plots for my car when it only had a test pipe and NO TUNE. Note how friggin' lean it was getting, especially when VTEC engaged. You can also see how much more timing I'm running now.


Since the ignition timing and fuel was so out of whack, the "efficiency" was kind of backwards. Efficiency shoudl drop as RPMs rise. You can also see that manifold pressure dropped in a more linear manner as RPMs rise. This is because the stock intake doesn't really have any "resonance", so there's no RPM where it flows more efficiently, like there is with the PWJDM. The fact that the PWJDM does have 2 resonant humps makes it look like pressure drops more than the stock intake, but that's just an illusion.

bpaspi

Vacuum is created everytime when the pistons are going down during intake phase. Also at very low engine speeds.
If the intake system is not restricting the airflow, no low pressure would be measured inside the manifold (taking the bernoulli effect aside).
Only if the piston speed is higher than the airflow can follow, a low air pressure is generated. It's a clear indicator for an intake system that doesn't work very well in high speeds. But let me qualify my statement - for a street car it is absolutly well designed. A race engine would be different.

I'm not talking about Throttlebodies - I'm pointing at the manifold. It has several functions for driveabilty of the engine. It must be small volumed so that Throttle response would be good, it must have equal lenghts for all cylinders to the plenum chamber, it must be big to provide enough air to the cylinders even at high engine speed, it must be designed so that every cylinder gets the same amount of air (cyl.4 criteria).

I don't agree on this one. Because the lower airpressure must be inside the engine not measured inside the manifold in this case.

b.r.i.a.n.

are you serious? how are you going to get the ignition timing tables correct on the street? if you're going to magically guess off some base map you're doing it wrong.

in this case though, this soft dyno can help you get to the vicinity of mbt but like i've said before there are way too many variables to take into account. the road (bumpy, elevated, etc.), tire spin, etc.

b.r.i.a.n.

i completely agree lol

unlimitedpower

Nice job Gernby. I'm sure there are a lot of people out there stuck on the
bigger the better.. which is obviously not the case. But this has been
well known since the beginning has it not? Cat backs are for
sound/weight.

B.R.I.A.N- just FYI, Mercedes Benz (I know positively) and i'm sure
all of the big manufacturers use soft dynoes extensively for engine
development. Also, many racing teams use soft dynoes
exclusively. Makes sense.