I'll have to recalculate my intake length and maybe upgrade to LRMAF and 3.5 " tubing......I'm surprised you didn't reuse the stock Elbow and plenum and just smoothen everything up internally just to see how and if you gained power......Is the Frankentein IM plenum larger since the power seemed to flow stronger into the 7k range? You're really good with math and that FLT Racing formula info....I was good in math back in the day so I'll try it out to see what length is best for my setup now!

All that would be is a SSIM with a little polishing. Been there, done that. So has half the forum with proven results and info.

Almost all of my lengthy research returned evidence that I would want at least 120-140% larger than engine displacement for the plenum volume and that I would want to force the "smaller" TB to become a venturi to make up for not going with a bigger one. Now if I reused the stock plenum and elbow, I would be nixing the majority of my theorized gains. Race teams that must use intake restrictors do the same thing on a larger scale, they go with a giant plenum and larger piping on each side of the restrictive part.

This plenum is just over 270 cubic inches, which is nearly 130% of the engine volume. Rough estimates (don't have exact calculations) of the stock intake manifold are closer to 180 cubic inches. The stock elbow not only splits the flow and makes for unpredictable results with the shelf cut out (look at streetz huge AF differences across banks with a SSIM...), but is also too small to give the desired venturi effect.

How's your driveabilty on the street now? That FTL info stated a intake plenum volume should be within 40-50% of engine displacement....Does that mean (+ or -) 40-50% 108.5 cu in -325.5 cu in or just within 40-50% of the displacement 90.80- 108.5 cu in?

Our engine is 213 cubic inches. The FTL site is saying 100%+40-50%. I didn't completely trust them for that info and instead found info from tons of other sources that supported it.

On the street, initial tip in throttle response is a little bit slower due to the larger plenum which was fully expected. I was actually expecting to have large low end power losses... but that's not the case.

wow man, that intake gave great gains, would be intersted in hearing price on one... also has anyone figured out how to use a 5.5th gen maf on a 4th gen? id like to get a 3.5" setup made

I find yours pretty similar to theirs.........
http://www.speedforceracing.com/inde...roduct-request

Yep quite similar. Bigger plenum volume and elbow cross sectional area on my little creation, though. The SFR has the advantage of custom runners and velocity stacks, though.

Where is the TB? mounted to the back of your plenum? I don't see how you got 30 some odd inches to the battery unless the curved elbow is part of it. Stock location only allows 17-18" with a velocity stack and stock battery position

The elbow and TB are included in the length. The entire intake leading up to the plenum resonates. That includes elbow/TB. When at WOT, the TB itself is nothing more than part of the intake pipe.

This picture here shows a better shot of their plenum size.....should be a pretty good bolt on for most....I'm sure a tune would be needing to really benefit the most though!!! Their velocity stack design is more like want I was thinking....wish i knew someone on this forum that run this on a N/a setup I'm very interested but, I'm really curious what Jaypee did using an OEM intake and how he made so much power....he must be running a standalone.....

Yeah, I would think it is a good bolton for most as long as they properly matched those ports to the oval shape of the LIM. The velocity stack design would have required me making full runners that were oval in shape towards the bottom with a smooth transition from round to oval. That would have been a serious endeavor with much more time spent though not out of the question for me to make. Again I point out the small elbow and smaller plenum. You, yourself were sure that my 3.5" elbow was even too small. A 3" pipe is over 50% less cross sectional area (flow potential) than 3.5".

Not to say their manifold would perform worse than mine, but the differences may cause theirs to perform better lowend/midrange and mine top end. One big benefit here is that I wouldn't be caught dead selling my design for 1099 dollars.

In terms of jay_pee, just a TS flash + AFC tuning. Different dynos give different results. Most of his dynos previous to the 276whp numbers were in the 264-271 range which honestly is not way above and beyond what is expected of a well bolted and tuned VQ35DE. He ran lots of 12.9s, 12.8s, 12.7s in the 106-107 range before those 12.5 and 109 trap PB runs that were probably the combination of full track prep (weight reduction, power steering) and perfect conditions. Also want to note that his was not a stock IM, it's a fully ported and polished SSIM. The SSIM is no slouch with supporting mods.

I did run a 12.6@108 today with full interior, PS connected, over half a tank of gas, and my whole toolbox sitting in the back seat... So obviously his times can be reproduced

http://forums.maxima.org/1-4-1-8-mil...ml#post7941062

I saw that vid today...be careful out there!!!! And I read you post religiously.....Yes I did think your intake was gonna fall flat at higher rpm...and yes I was wrong! The SPR intake elbow looks like a 3.5" tube but the elbow radius is tighter than yours....but like yours power is sustained on a flat curve toward redline! I wish they would have shown the rpm table though!!!! And yes that price is steep!!!!

I have the feeling my redline is a little higher than the one in that dyno (by about 500 RPMs if that is a stock redline... Mine is set to 7200 and was for the dyno. It shows 7000, but guessing his equipment was a tiny bit off), but the numbers look similar to mine regardless.

That elbow is certainly 3". Want to know how I know so certainly? Look at the TB flange. It would have to be stepped down from 3.5" to 3" in order to mate up to the TB properly if it was 3.5"... However, notice it goes straight on into it. The TB is 3" OD (76MM), 2.75" ID (70MM) just like 3" pipe.

nice man!!! full weight, daily driven, everything in the car is the way to go IMO thats really what you car can do everyday. great times man...

Notice both dynos were done on a 6 speed car in 4th gear. Look at the speed on mine compared to the speed on the example dyno. Definitely revving out a good bit further and still staying flat.

I currently have a Frankencar intake, and am stuck on deciding how/if to modify my current setup. I will definitely be adding a velocity stack and switching over to an AEM dryflow filter to get away from the oiled K&N I use presently.

Where I am stuck however is deciding whether to stick with the Frankencar midpipe, or to reincorporate the helmholtz resonator. I recall from older forum threads that the helmholtz resonator smooths out the power delivery curve, although it does drop peak hp a tiny bit. What route do you think I would be better to take? If I do reincorporate the resonator would I be best served to add in a short mid-pipe to avoid having an overly short intake length?

My car strictly sees road use, and I have no plans on ever hitting the track with it, so I suppose drivability for the street is the major concern for me.

Sorry for the question but the ftl website didnt really explain it for me, where do I want to have accoustic resonance? Do i want it at redline? Or do i want it ~500rpm before so i actually get to use the resonance for a power bump? Because we just tap the redline and then shift.

Stick with the midpipe IMO. hemholtz was tuned for a stock intake and IMO i believe it causes more turbulence when used apart from the stock setup.

Bump. Legit question.

I'm an A/T DEK, since I'm auto wouldn't I want to resonate at a lower rpm? Or is the 5.5-6k ideal for our engine?

For example, if I wanted to resonate at 4.5-5k I would need a length of about 38" (using 3.5" intake piping and maf) would this shift my power band to the left or would it just yield less hp then resonating at 6k?

No. It's a bit different than that. No matter the length if your intake, your engine wont peak at certain RMP{'s with just resonance tuning pre IM.

You still want peak airflow/hp @ a higher RPM. And somehow extend that rev limit. We need it with these long AT gears.

As a sarcasm note, just put the A32 IM on there, you'll peak @ 5200 and lose about 50whp from there to red line

Case in point, you always want to be climbing in HP, no matter your tranny. If I had a choice, my peak hp would occur @ 7000. Best for shift points, etc.

Ok I see what your saying, thanks!

This is really cool information. I made a spread sheet of rpm vs. intake diameter and it gives the tuned intake length in inches.

intake tuning.doc

If anyone is interested, the intake tuning formula solved for L (length of intake) is:

L = ((nV/F) - 2.4D) / 4

L = intake length in meters
V = 340 m/s
F = Resonant Frequency
D = Diameter of intake tubing in meters
n = 1

I did the same thing last nite on a little post it but I'm probably the only one that can understand it good job

Did you check out the attachment? It's interesting to note that piping size has very little to do with the resonant frequency.

Thanks for that spreadsheet, ajm. It helps put all of those numbers into perspective.

Well yea the resonant frequency is basically selected in order to find what piping you would need, maybe I'm misreading your post

The dominate variable is length, and diameter of the tubing maters little when tuning to a certain frequency. I supposes that increasing the diameter of the tube does make the air mass larger, but at the cost of velocity. If you consider momentum=mv, then increasing m while reducing v (larger diameter tubing) would not have as much of an effect as simply increasing m (longer tubing). Or maybe I'm off base since the discussion is about resonance.

I'd love to find a way to stuff 55 inches of intake tubing under the hood to hit 3500 and 7000 rpm.

You will know someone in March next year after the winter and crap pass up here.....I'm planning on doing this with some cams. Gonna be real nasty!! Already spoke with speedforceracing. Gonna see if I can get them to make that elbow 3.5" for me....

Well the thing is we're specifying the frequency we want, if we were taking the length and plugging it in to find frequency you would see it the other way around To me I see it as the diameter (compared to the length) is small so it doesn't increase the volume as much as an increase in length thus effecting the frequency minimal.

I love this thread. There is not many forums that you can see this type of educated discussion in the general discussion forum.

The biggest difference between the DE-K and the 3.5 is the length, the DE-K has a shorter plenum so it needs a longer intake (TB-filter). The 3.5 has a pretty long plenum, which is why a shorter intake works well on that engine.

is that the reason the InJen intake is so freaking long? I remember people saying it was too long of tubing to be effective. Maybe that was their idea though but because of limited space of hitting the battery they had to bend it that it ended up in the unfortunate position behind the radiator

No they did it that way because they are ricers

Im serious though they just made whatever they thought would sell based on the "cai frenzy" at the time and what they could make fit in with no modifications. But really imho I think you would lose hp with the injen your better off stock or gab. Unless theres a dyno that proves me wrong

The volume of a cylinder is V = pi * r^2 * h. So if we have an intake tuned to 6000 rpm with 3 inch pipe it would be 31.367 inches long. So

If we add half an inch to the pipe keeping it tuned for 6000 rpm would give us

You can see that increasing the diameter my 0.5 inches (16%) gave us a 78 in^3 (35%) increase in volume. The pipe is 0.297 inches shorter ( > 1%) but 16% more spacious and tuned to the same frequency.

However if you increase the length of the 3 x 31.367 inch pipe a mere 3 inches (9.6%) and keep the diameter constant, you've re-tuned the pipe for 5500 rpm.

Therefore a change in the length makes much more of a difference than a change in the diameter with regards to the resonant frequency.

Yea thats why I was saying the diameter in essence is very small compared to the length. Increasing length is whats increasing the most volume. You can in most cases choose to neglect the diameter and still build an intake that would resonate at the frequency of choice.

I looked at the ftlracing site because I wanted to see if they posted it in the case where they neglected the diameter and maybe some of us number (math) guys should read words once in a while.

I hadn't noticed that before i really rather deal with numbers I hate words

Seriously, that's the truth, man. That's why I gave the numerical example above.

I just wanted to make sure I really understood what was happening here so I don't waste my time trying to build one.

The Injen is poorly designed, but effective in it's efforts. Either way, you WILL see an increase over stock, though it may be minimal on the 3.5 especially. If you made an intake that was the same diameter throughout that took the same path as the injen, it would fair quite well on the DE-K I think. The Injen just looks like cobbled up pieces of other pre-made intakes they had lying around, they took what they had and put it together.

Is everybody here a mechanic or somethign...how the hell you all know so much about cars?

I see you just joined.....I'm fairly new myself.....I used to think the same thing..BUT READ READ READ....and then when you get tired.....READ some more....and ask questions....that is how we learn from each other's experience. You will understand if you stick around.

Well I was just wondering whether there was science behind InJens madness. It was the first intake I had. I still think my current setup is superior to all of those and modeled after Manny's.

6"outlet Filter>3.5"BPI>3.5" tubing>LRMAF> PFTB

i'm gonna get rid of my powerrod and ordered a crankcase filter so that I can get rid of my awesome vacuum probe thingy

I think mathematical equations and talking about wavelengths etc is more scientific mechanical engineering talk than mechanic's talk....

hmm.. i wonder if a similar intake to that would give gains on the HR motor.. working out the dual TB of course..

Engineer. Currently finishing my MSc Combustions Engines in Germany (RWTH Aachen), BSc Mechanical Engineering (U of MN)
Yeah, and I read a lot, too. The forums (maxima.org/my350z.com/G35Driver.com...) give you access to others' experiences (plus trying things on your own ), but a more compete understanding can be gain through AEI (SAE), Car and Driver, textbooks, etc.