i was referring to the MAF reading correct due to tube dia, not length. if any one is in the spokane, wa area you can test drive my 8 and see how if feels compared to other 8s i would enjoy the input

You have to have the right Maf tube diameter and lenght (before and after the sensor).
It would be useless to see how this mod works compared to another rx8, you should do some dyno pulls and datalogs with the same car and the different intake solutions.

Back in the day, people were roadracing motorcycles with similar success, some with wire wheels, and some with the much stiffer cast wheels. The suspension settings (springs, shock damping, forks, etc.) between the two groups however were much different. I find removing the stock strut brace to make a small but noticeable difference. Going to a 6-pt upper and lower brace made a huge difference in the other direction. I'd rather have a stiffer body and softer (more compliant and controllable) suspension than a soft body and stiff suspension. Every manufacturer from Porsche to Ram truck is going this way. (Compare the 1970 Camaro SS with its 2010 counterpart). Feel free to do it your way, but that doesn't imply another is wrong.

Back at you. I never said it was wrong, just unnecessary. Since my car is only used for competition I don't care about things like NVH rattles or a host of other concerns that manufacturers attempt to address in a daily driver situation. Your assumption that it's a handling performance part is only that, the same for assuming my setup. Never mind that most seat of the pants perception evaluations fizzle when put to the objective performance test. Unfortunately this kind of mentality isn't back in the day, it still lives on ....

have you looked into some of the aviation guys and their intake work/experimentation?
You have reduced a lot of dead air space so response time will be less. But as far as power is concerned---dont know?
You are doing the right thing in monitoring your a/f's and trims (what are they by the way?)
and in open loop that really wont matter much.
How are your vacuum readings?
OD

vac is ~15, ltft is at 15.8. a/f at wot gets down to 11.6 at upper rpms with a upgreaded fp. my last two tanks of gas have been 18.9mpg and 20.1mpg. this friday i am going to the drag track to fine tune the cai length. ill let you all know how my times go

Fair enough.

The problem is finding "objective" tests. I tried for a bit to measure chassis deflections but couldn't come up with a scheme that both worked and didn't cost a bundle. Race teams (and OEM's) have those resources to "do it right". However even within a group of identical race cars, the chassis settings are often very different depending on driver tastes and driving style. There are many examples of one driver hopping into a teammates car (to score points for a championship run) then going back out and crashing because of the different setup. (Which is why this practice has been banned in modern times.) Even if the metric is entirely measuable, like lap time, how one achieves that can vary significantly. Agreed that most seat-of-the-pants evaluations are bs, but even you allow that not all are. I don't consider that unfortunate, I consider it part of the fun.

As much as I'd like to agree with you OD, I doubt if there's much useful from aviation for cars. Airplane engines are essentially single rpm units, living 95% of their time (for the standard units) in the 2300 - 2600 rpm range. This vastly simplifies intake design. It's also one reason why attempts to "fly" car engines are generally unsuccessful. Think of a spectrum of ~200 hp engines ranging from genset/airplane/american big-block V8/Honda VVTEC/Renny/crotch rocket/. Moving a Ninja engine into a Chevy pickup truck or the reverse would be unwise. In the same way, it's usually unwise to sacrifice a wide powerband for a higher peak output in a street-driven car. You might end up with great power at 8000 rpm and be unable to avoid stalling at a stoplight. The mod being discussed (shortened runners) will likely move things in this direction. Whether the results are desirable depends on the taste of the user. YMMV.

vacuum is a little low? Watch for leaks? It would make the trims and any tuning a nightmare.
Dont worry about open loop readings as much as closed loop. The high trims suggest a possible leak?
Keep on rotoring on!
OD

yea there was a broken T, so vac is closer to 17 now and ltft at idle is 14.3 and wot is 7.8 with a a/f of ~13.4 7-9k

well other then low end tires killing my ets, i got my tube length where it works best. wot a/f ~12.8 with a ltft of +8.1 and stft 0.0. next up dyno

well here is my final setup, low end tq has dropped but still has useable power by my standard. next step is to cobb tune ssv and apv timing around the new system

looking forward to reading some dyno numbers

Where is the MAF?

right behind the heat shield

Just left of the shield? If so then I think I see it. Is the tube long enough to not cause issues?

Another Home Run post by Team.

A little feedback from our own testing and some observations:

-Using our fully tunable Grand-Am Bosch 4.3 ECU (about 20K without Motec and chassis wiring harness) we tried several different intake lengths. Intake to throttle body diameter was kept to match up to the I.D. of the throttle body.

-We rented a dynojet here in Indy for a few days using several different intake styles and lengths that we pre-made to make smart use of the dyno time. This included air filtration which ranged from a K&N style to a Fram square/rectangle style in a gigantic air intake just over the radiator. This air opening ran the entire length of the top of the radiator opening.

-All pulls were performed using our normal testing methodology: Same rear tire pressures, same gear, same oil, water and differential temp. Same tune. Same fuel.

-Remember that you're looking for small power changes and not 40 or 50 hp so consistantcy is key in your testing procedures.

-We started with an intake tube about 4' long from the throttle body. We then whacked off 5 or 6" at a time to see what went down. This was a "gross" test just to determine big changes. We ran 3 pulls at each length to see any differences. Even with stable temperatures you'll see at least 1 hp or 1 ft. lb difference in each pull. Think about this for a second rookie bloggers---this is about a 1/2% power when your recording 200+ hp. 1/2 a %. Variations in your measurement devices (dyno) can often be the source of the variations (like using a sundial as a lap timer).

Our findings:

-If you could have a long intake that extended out in front of the bumper and used a bell shaped intake prior to the actual intake tube, you'll make are 2 ft lbs more torque than anything else we tested.

-Very smart engineers at our testing event offered that intake length contains a "resonance" that is a natural frequency generated by air flow through a space. I'm not smart enough to talk about this however I believe it's similar to when you crack a single window open in your car and hear the wind buffeted and your ears hurt.

-Short length intakes (a few inches in front of the throttle body) produced very poor numbers for us which validates the longer lengths.




A few observations:

-I would invest in EGT's to measure temp delta's. My assumption would be that the rear rotor is getting more air and the front less. Air doesn't like to bend and THE VELOCITY of the air in a rotary is more critical (IMHO and talking to guys that make custom intakes) THAN THE VOLUME. Which is why porting of this motor doesn't provide huge gains like prior 13B intake ports (again, IMHO).

-The stock O2 sensor using the stock tune is a POS and you need (NEED) to understand just how much this is effecting your testing. Your O2 sensor is measuring A/F from BOTH the front and rear rotor and averaging (my understanding) of the two rotor combustion events. If your rear rotor is getting a ton of air and the O2 sensor reads this, depending on target A/F your ECU will pull fuel. If your front rotor is not getting as much air AND the ECU pulls fuel, this will further lean out the front rotor. This is not good btw. Boom. Boom is not good. One way you measure this is EGT sensors (which we use). The other way are individual O2 sensors (which we have used). Note to smart guys, we couldn't do invididual cylinder trims because that would require Bosch engineers to get another 10K of my race budget and our 3 rotor friends at SpeedSource don't use this. They use 1 O2 sensors. If readers of this comment don't understand this DO NOT CONTACT ME asking what this is all about. Do your own research rookies and learn something.

In summary and for those that read this post and take some contributions as gospel, please understand what's being done and tested here along with how it's measured. This is not meant to be a negative evaluation or comment in anyway but rather a better understanding to readers of how this methodology works. Our friend here is doing some Wright Brothers work and his findings will be helpful to this forum.

Happy Rotoring,

E

Side note: We have reconnected our stock OMP using a block off plate from the internal engine oil and now use a remote reservoir to pull 2 stroke oil. Findings to follow.



-I'm not going to bash your seat of the pants testing but you should do some research here as well. There is a reason why NASA rocket scientists don't build space craft based on seat of the pants feel.

That's the entire reason the RX8 runs the variable intake shutter valves to start with :)

I'd say just from looking at it, that all that the modification has done is dropped some low end torque, and the car now feels faster via the arse-dyno because you feel it pick up back to the original level once you get into the middle of the rpm range.
Going via the seat-of-the-pants, you tend to feel changes in torque much more than they feel the actual torque level (it's why most turbo engines feel faster than they actually are), so it can be very misleading - you can reduce the torque at low rpms and it'll feel the same as if you added some higher up...

I greatly enjoy reading your posts Eric. They are technically precise and well-reasoned, but also gracious to the newbies and hobbyists. Probably the best thing us "tweakers" could do is leave the car dead stock - but that wouldn't be much fun. :hahano:

Holy Shit... Eric's post is a Grand Slam

Reminds me of the earlier header and intake post(s).

I modified and tried all kinds of crazy things in my early rotary days. Some of them were neat ideas and others would completely stupid. Has anyone ever modified the inside of their intake manifold with Bondo? I have! I learned all I could technically but there is nothing that can replace actually trying something. I found that at times there were some things that I didn't think could possibly work yet did and other things that seemed like they would obviously work but didn't. I applaud the OP for at least trying different things, even if they don't work out. Even a bad result is a result and is a contribution to knowledge. The key to it is to be able to measure differences and show results rather than rely on the butt dyno. One thing to know when it comes to runner lengths is that getting longer won't just keep lowering the rpm powerband and shortening the runner won't keep moving it up. You'll hit different harmonic orders and at some point a longer runner will make more power than many shorter ones and vice versa.

this exactly.

thanks Eric for the post

subscribing for dyno results