1994 G50/Q45 Cold Air Intake prototype finally built

[qsiguy]

I've been working on this project for quite a while and just hadn't gotten around to fabing up my prototype. I finally got it done tonight. It turned out good I think. My welding leaves a little to be desired since this is stainless and it's a little harder to weld cleanly but the next ones I do will probably be tig welded by a friend of mine so it'll look pretty. I will be making at least 3 of these and will be selling them all. I was going to be using one but am working on a turbo system for this car so I won't need it. I don't have the final price yet but it will be around $175-$200. It's all stainless steel and I'll include an air filter like the one in the photos and stainless steel bolts. The lower mounting bolt is from the old air box and uses the existing threaded bolt hole.

I had previously removed my entire stock air intake system including the piping behind the bumper and below the headlight. I'm not sure if this unit will fit without removing the stock equipment. The hole I cut in the fender is 4" but it could be smaller. I used a hole saw and the metal wasn't too thick so it cut relatively easy.

If you jack up the driver front of the car and unbolt the inner fender well you could install the air filter that way. I didn't have my jack with me while doing this so I was able to remove 3 screws in the front portion of the plastic under the air filter location and pull back the plastic and get it in from there. I did have to push pretty hard to get that plastic down far enough to get the air filter in.

I only have the prototype completed now. Anyone whos interested in one let me know. Since I was going to build one for me anyway I just ordered parts to make a few. First come first serve. Don't know if I will make more or not, depends on interest I guess. When I sell the prototype it will obviously be cheaper than the next two as I will be sending them out for welding so they will look a little nicer.

Here's the photos of the unit and the install.

Before cutting

4" hole for down pipe.

4" hole 2nd view

Test fit

Bottom view of down pipe

Bottom view with air filter installed

Top view after CAI was finished with 80 grit glass bead

CAI before bead blasting

CAI after bead blasting

CAI after bead blasting view #2

CAI closeup after bead blasting
Modified by qsiguy at 10:09 PM 4/27/2007

[Q45tech]

Inside the oem air box there is a metal horn [flare] that matches the MAF to essentially what is a free air space after the filter. This was done to MATCH the acoustic impedence of the pipe from plenum thru TB to and thru the MAF.

Changing things can affect the tuning and accuracy of the MAF. This might be negative or positive and vary in small rpm increments. You would need to flow bench the entire system to see any improvemnts or problem caused by resonation.

The oem air filter being close to the MAF straightening screen help dampen the acoustic reflections that occur in any round tube.Base on years of experiments the best restriction improvement will be 4" H2O................as the oem only has 6.5" H20 restriction at 6500 rpm and it is not measureable below 4,000 rpm

At speed the oem system can make the convoluted ducts and passages almost transparent to restriction due to the pressure build up infront of condenser/radiator......................why the inlet horn was placed where it was.

Anyway oem restrictions only occur from 5,500 rpm up due to the low air flow rate.

The engineers tuned the oem system to also help 55 mph MPG.

Think twice before you second guess a Million dollars worth of engineering effort since this was a one of a kind design and no parts were cross used on any other Nissan.

Nice metal work job!

If you examine the MAF voltage output [with an oscilloscope] you will see the actual gulps of air transformed into a voltage...........^^^^^^^^^^^^^^^^^^^^^^. whose sine wave shape mimics the intake cam lobe shape and air flow since each flow is 90 degrees apart and 248 degrees of flow occurs you have acoustic over lap.

at 600 rpm =20Hz [600/2=300 x4cyl=1200/60=20] and 6000 rpm 200Hz.

[maxnix]

Not sure what is gained from moving the intake to a lower pressure area.

The design of the resonance chambers and the OEM inability to flood may well be lost, and fo what gain, if any? Would have to have back to back dynamometer runs and accelleration runs to accurately assess performance.

Nice metal work, but seal the cut out before it starts corroding.

[elwesso]

certainly does look cool!

[qsiguy]

The cut out will be sealed, it was late last night and the wife was waiting on me. I have a few finishing touches still.

Not intending to start up another debate as to the functionality of the "CAI". It sounds good and is better then the MAF adapters that put the air filter in the engine bay, which is what was on my car before. Not sure why you assume the air filter is in a low pressure area as there is an opening in the front bumper that sends ram air directly to the air filter. I know how some of you feel about modifying the stock airbox but there are many who are doing it just the same. I'm sure the stock airbox is perfectly functional but rarely is performance the SOLE goal in designing parts for a vehicle. They have to concider economy, sound volume, and many other issues. Now I got going on the debate!

Anyhow, if anyone wants one let me know, if not I'll stick them on e-bay. Just sharing the info and my project. Thanks for the compiments on the workmanship.

[qsiguy]

Correction to the low pressure concept. You may be right that it could be a low pressure area IF your stock air box system is still installed behind the bumper. With it removed there is nothing in that area and it has a clear path to the bumper openings.

[speedingminivan]

I might invest in one if I saw some dyno benefits...

[qsiguy]

doubt you'll see any. I'd be willing to bet you won't loose power over stock (but I'm sure the gentlemen above will disagree) and if you hear it you'll love it. Sounds amazing. I will not be making any performance claims. Although, if you currently have a maf adapter with a cone filter inside the engine bay I guarantee you will get a performance increase.

[speedingminivan]

Well if you ever get the chance to put it on a dyno we'd certainly be interested in the results

If anything this might help out the turbo guys.

[superuber]

Very nice! I think you need to give yourself more credit. You did a real nice job. Now go bolt that turbo on and never mind the critics!

6 DAYS TILL CARLISLE!

[maxnix]

....if you hear it you'll love it. Sounds amazing. I will not be making any performance claims. .

So this is all an exercise to increase intake noise?

[qsiguy]

Thanks Super, nice to get compliments for your hard work. Believe me the turbo is the first thing on my mind. I have pretty much everything sitting here next to my desk, turbo, bov, wastegate, gauges, flanges, EPROM programmer, and in the garage I have 20 feet of 2.5" tubing, a bunch of U-Bends, new tension rods, tokico shocks, california customs springs, and more I'm surely forgetting. I have a Zeitronics Wideband O2 monitor on the way. Just picked up $800 worth of stuff from Joe @ Infiniti. Needless to say, the car should be a new one by the time this project is done.

[sijoko]

Props to QSIGUY for building a real cold air intake system. Yes, it will actually pick up cold air since that is the spot that the Active Q uses for its heat exchanger. It is also a high pressure zone, that is why you'll see louvers inside the wheel well to let the air flow out.

As far as performance, I experimented a while back with a long tube that moved my Stillen filter into the same spot as QSI's design. It worked. The longer tube did affect my torque band a bit but it didn't hurt performance compared to the stock setup. Of course, my design was not anywhere near as professional as what we see here.

[speedingminivan]

So you're saying there's a good possibility of performance gains?

[Q45tech]

Contrary to the concept of hot air rising the closer the intake is to the roadway the hotter the ingested air is.

A nice semi exhaust stack sticking up 10 feet would ingest cooler air.

Cold air is relative compared to the air in engine bay after flowing thru radiator and radiantly heated by engine.

A simple sensor inside the flex hose feeding TB after MAF or better inside plenum might be very instructive.

Ever notice the inside center vent on fresh air is 10F warmer than ambient?

With so many spending on sound system I've wonder why someone doesn't create one for underhood sounds.

[maxnix]

With so many spending on sound system I've wonder why someone doesn't create one for underhood sounds.

Or at least buy a used OEM CAI from a "performance" buff.

[ryannico]

I would also like to install cold air intake but i'm sure which will fit and the with the best performance. I need more research on this.

[db_autotek]

Great Work! I know you spent some time on this! I'm working on a cold air setup myself, which will use intake tubing through the stock hole behind the headlight, and go to a filter behing the bumper / under the headlight. I'm not criticising you, so don't take it that way, but I would be concerned with water in your setup. There is frequent rain here and roads always flooding in the summer. My friend siezed his 99 Accord V6 with a cold air intake just like this, becuase he didn't use the AEM water bypass baffle. Now, becasue of that, I'm paranoid against big puddles and cold air kits. I'm not flaming you, I just would rather stick to my plan. Consider cutting a 2.5 inch space in the tubing and inserting a watter baffle.

See:http://www.aempower.com/ViewCa...ID=20

[QShip]

Great work!! Don't stop what you're doing!!

[qsiguy]

Great Work! I know you spent some time on this! I'm working on a cold air setup myself, which will use intake tubing through the stock hole behind the headlight, and go to a filter behing the bumper / under the headlight....

That will put it in almost the same place as my air filter but mine is about 10-15" further back than the headlight. We don't get rain all that much and I don't drive it daily so it's not as big of a concern for me. The only other water safegaurd I will be doing is putting a filter sock on it which repels water and larger garbage. K&N makes some and I'm sure some other companies have them as well.

This system will only be on my car for a short time as I'm in the process of installing a turbo on it so I will be using pretty much the same intake pipe for my compressor plumbing. If you guys think this filter location is asking for trouble the flood gates will open when you find out that my air filter will be under the rear of the car after the turbo is installed! It's not for everyone and to each their own!

[qsiguy]

Thanks again for the compliments. Regardless of what some think I believe it's a good upgrade. They have their opinions just like everone else. They claim that there aren't gains in doing this but they don't have any more proof than I do that the OEM box is better. It's all opinions and number crunching. I am going to drag out the complete OEM air box system and take a photo of it in case some haven't see the whole maze of plumbing that Infiniti spend "millions" designing.

By the way, I have parts for a couple more CAI's and until I make them there are some options on how it's put together. For instance if you want it to turn go and forward behind the headlight and have the air filter installed somewhere behind or under the headlight I can do that too. So if you are interested and have the cash let me know and I can put together a custom setup for you. I'm not going into business doing this so first come first serve and I don't know if I'll ever do any more. Something more involved won't be cheap so be prepared to spend some cash. I already have quite a bit of cash in the stainless and the flange cutting and for something more complex the labor will be higher. If no one speaks up I am just going to copy what I've done and put them up on E-bay and try and get some of my cash back.

Before some of you start debating the necessity or functionality of a custom "CAI" again, don't bother. You are beating a dead horse, so to speak. Everyone's heard it a thousand times. You've stated your opinions now let the people that are interested discuss the options. I would appreciated it. Thx I don't make any performance promises, I'm just saying here it is if you are interested. Also, some can use my design and modify it and make their own to suit their preferences.

This is a car that you can get relatively inexpensively and for me it's a good platform for a project or "toy" that I can modify and not feel guilty about it. It's been paid for for years and now I am fixing it up the way I see fit. Whats the fun in leaving it stock?

[db_autotek]

I agree completely!! Do what you want to do, it's your car. I've already got heat for taking out the factory airbox, but damitt it sounds good and scares the local Civics. Keep it rocking!! By the time you've calculated all the differences in 14.7 air pressure and bla bla bla then you've completely lost the whole point of the whole thing: To have fun learning.. probably replacing fun with a big headache.. next thing you know your girlfriend gets replaced with a large bottle of Excedrin.

[sijoko]

It seems whenever someone tries to do some performance mod to their Q, the peanut gallery kicks in with the negative comments. I wish we had more performance minded Q owners here. I miss Rob (rsiwicki). He did stuff to his car instead of just talking about mods.

There are a few others like him on the board but most are satisfied with doing safe things with their cars like new rims, aftermarket radios and muffler deletes. Those things are okay but if you want more power you have to go out and get it. No one is supporting the Q in the aftermarket. We, the owners have to do it ourselves.

[PopPop]

I understand how you feel Shane! Like you said everyone has an opinion of Q Mod's some positive and some are negative. We learn threw trial and error when dealing with our G50's. We have to keep in mind that everyone isn't trying to achieve the same goal on this forum. Some like bone stock non-modded Q's and others are always looking to upgrade performance while others are looking to increase the Q's daily drive ability. You can offer to give a bone stock non-modded Q owner a 100 additional HP and even at no cost and they won't except because this is not the goal that they are looking to achieve. Where someone like James, Wes, Rob or yourself wouldn't hesitate even at the cost of drive ability. I love the CAI and it has benefits in performance increases and sound no matter what other may say. This is coming from someone who has experimented with both stock and custom CAI systems not just going on what I have heard or what data says should be the case. From a dead start you loose power or torque but, mid and upper end ranges you can feel the difference. My CAI is still in the engine compartment but, is less than 3 inches from the factory air duct so it draws in air from this area and not from the engine compartment. Cooler outside air comes threw the factory duct and what is not drawn in by the CAI is forced around the outer portion of the filter which pushes away the hot air. These pic's are not new but, will give U an ideal on what I'm talking about. My dyno run was also made at that time with just the CAI and no other performance mods. Dyno is ran by one of the top import guys on the east coast who's imports produce 900 plus HP!

[Q45tech]

Based on hundreds of measurements the best you can achieve is 7" H2O with nothing in front of MAF so the cone and pipe might get you to 2-3" H2O.An improvement of 5" H2O or 1.2% less restriction.....................3 HP is nothing to sneeze at.

Especially since the cost is less than the usual $100 per HP.

[ponzy]

Ok. Shane,If the price is right, I'll get one. But i guess il b needing a design with a water buffer and if possible no metal work(newbie). We have lots of rain here. Pls email me the pricing. [email protected]. Thanks a lot.

[qsiguy]

Ok. Shane,If the price is right, I'll get one. But i guess il b needing a design with a water buffer and if possible no metal work(newbie). We have lots of rain here. Pls email me the pricing. [email protected]. Thanks a lot.

I doubt you will be able to put one of these in without at least a little cutting. I'm using 3.5" tubing to keep it the same diameter as the MAF opening and the OEM opening behind the headlight is more of an oval shape. I could get you a filter sock or find one of those water baffle devices talked about above. I think the filter socks are more than adequate as they are used all the time for filters that are subject to direct spashing. As long as you don't submerge the filter you shouldn't have any trouble if you have a sock on it.

Also, I need to know what design you are interested in, one like the one shown that I already have designed or a more custom one. I'll email you and we can discuss what you want.

[qsiguy]

PopPop, I love the tube you have from the TB to the MAF. I was thinking about doing something with that when I get the turbo plumbed in. You dont' have the TCS do you? Maybe someday I'll pick up a non TCS TB and swap it out. Mine doesn't work anyway and is just more junk in the way.

[db_autotek]

good work again.. Looks alot better than my jiggy-rig. You have re-motivated me, tomorrow I'm gonna get out there and machine mine up right.

[db_autotek]

PopPop, tell us which tube you used for the TB to MAF. It looks like many I've seen back in my honda days. Did you find one that was about right???? Share with the group mang!!