4 inch intake? Anybody have on 3.7? Was thinking to make one for my self, but since stock size is 3.5 around MAF, retune is a must...
Need some imput.

Thanks

 

Over a month old thread but you got no help so.. A drop in k&n filter had proven to be only ~4hp less than Takada with way less heat soak. The sri allow more air but that's not our biggest issue, if you personally made a 3" intake pipe that was 100% smooth borland led to an area it could breath fresh dry air with limited heat then yes it would be beneficial. As far as the 4" portion you might just be allowing unneeded air to linger around to absorb the heat. Just delete the reservoir and k&n drop in filter and you'll be fine or order an age sri or wait and watch for an ct-e icebox.

 

Already made my self 3.5 intake. Did not want to retune it so went with 3.5.... With any sri power will be lost and loosing power is not an option for me. And there would be no air "lingering" in 4 intake...

 

Not true

 

100% true, unless you driving with hood open or in cold winter temperatures. Heat soak is worst power grabber.
I love short arm dyno results with hood open lol.

 

No, it isn't true at all. When you are moving (aka driving) you have airflow through your engine bay and you will be drawing in cool enough air to not make a difference. What a N/A or positive displacement supercharged motor will gain more power from is an intake that is the shortest, largest (but not bigger than your smallest obstruction AKA throttle body or MAF housing), straightest, and largest filter size possible. Obviously this will be limited by the size of the motor (a motor can only pull in enough air as it can use in N/A form). Another thing that is key on a N/A or positive displacement supercharger setup will be the largest throttle body possible. Again, this will be limited by how much air the motor can use. I can go into more detail if you want but these are facts, and facts I gathered by building motors.

Notice here my intake is as straight as possible 4", the throttle body is 90mm, the MAF housing is 4", and the filter is as large as I could fit. I do have a shroud on to get fender air but it does nothing. If anything it keeps the filter cleaner. This setup made 456rwhp N/A and is only 331cid (5.4L).

 

Oh and another thing is get away from heat soaking steel tubing intake. Make your own out of either aluminum (you can put heat reflective tape on it if you want), or a thin wall plastic. Steel is the absolute worst thing possible.

 

I am sorry, but you are wrong here, when car is moving air turbulences under hood will make sri suck hot air. Going low speeds up to 30mph, and higher speeds 50+mph was the worst intake temperature increase at MAF sensor. We took data couple times.

Here is an example for you:
My old sri setup on Infiniti vs longtube design both 2.5 at MAF (it made extra 18whp, and lots of torque at midrange):




I have to agree, intake tubing should be straight as possible before TB. And yes, it can be short, but it must have big velocity stack. and it must have access to fresh air (like factory setup). But like I said before, heat will kill any benefits of short arm (and this rule applies to any NA engine).
Now there is another example:
On VQ37VHR (dual TB's) 2.5 tubing vs 3 inch tubing made 10whp and this just with MAF scaling. Stock TB's size is 59mm (one per bank), TB's were send to Maxbore and bored to 64mm.
These extra 5mm per bank did not make any difference on the dyno and this is with free flowing exhaust. What we saw, is that velocity stack is a huge addition to the intake..
So not every engine will respond same way to the same modifications, what worked for you when you were building engines , it doesn't mean it will work on my Infiniti and Acura....
Just to sum up, SRI with same size tubing and not enclosed filter, will lose whp, unless hood is open, or filter have access to cool outside air.

 

So you're telling me that you think you gained 18whp by making your intake suck in cooler air? I can assure you that, that simply isn't true and there is more to the equation than that. All motors react the same way and what works on one will work on the next. Reading more into your post, you changed quite a bit. Keep it apples to apples, oh and you can never see intake improvements on the dyno as the car is static. I measured my gains at the drag strip which is actual proof. MPH doesn't lie.

But you guys can do what you wish.

 

cold air and big velocity stacks, fans blowing in front.... Keep in mind it is two tubes going in intake manifold not one and restriction free exhaust....
I was just giving some insight on intake that i was working on. And you said that temperatures under hood will go down when the car in motion, that was not the case according MAF readings....
And SRI was harder to tune because intake temperatures were jumping all over the place.... All good Thank you for your suggestions.

 

A dyno chart will definitely help the argument here.

As a general rule, the specified hp gain, as a result of an aftermarket cold air intake mod on a naturally-aspirated engine, is the maximum hp gain which is located at near the redline of the engine rpm range.

Minimal to no hp is added to the low rpm range. The hp gain is gradually increased as the rpm goes up in the mid-rpm band.

So in practice, one really has to keep the engine rpm close to the redline, in order to realize the full 18whp gain for a naturally-aspirated vehicle.

Torque-wise, the gain is virtually unnoticeable for a heavy mid-size naturally-aspirated sedan.

 

Again, I will have to disagree, my biggest gain was at 5000-6300rpm rage VQ37VHR and not so much on top, lost of torque in the middle. I will repeat one more time, to achieve good gains on intake side, free flowing exhaust is a must.
You'll have to believe me, torque wise it was really noticeable. Even on MDX, after jpipe and cats installation torque was more noticible....
I will post 2 dyno charts (not my), both of them on same tune, first stock intake vs 2.5" longtube, 2nd one stock intake vs 3" longtube with MAF scaling:








I really dont think similar gains could be achieved on J37 with intake only... Was talking to Rich from RV6 few years ago about intake, but he was not interested of making one. There is Dyno of my MDX on his website if you interested (tuned vs untunned)..

 

^^^^^

Agree with you, when you have the complete front-intake-jpipe/header-rear-exhaust setup.

But my point is on "cold air intake" being the only mod, with the remaining car stays OEM stock. The gain is minimal at the low end, and maximum gain is near the redline.