S/C Intakes

[VX Monster]

Originally posted by paultvx
Yeah.. I expected it'd run 92 octane. (Aftterall, there's no such thing as free horsepower.) Wishful thinking got the better of me. You know how it goes...

Paul,

This is contrary to a bunch of posts on the other board lately; the consensus there is that high octane in a VX is a waste. I'd think (others may correct me) that the S/C would not impact which gas you'd use, since it's still the same engine.

I'm *so* exposing myself to an onslaught here...

Based on the pictures I saw of the SC... looks like it was designed to work with the stock airbox... it doesn't look like the MAF sensor locatiion is changed.

If I make a intake kit for a NA car, it should work with the SC... right? I'll be getting a filter through work in a week or so, once I get it I will start the prototyping work. A thread will be started for that to keep you guys informed. Keep an eye open.

Oh BTW, the kit will be quite a bit cheaper than Calmini's kit.. and that kit has no heatshield. [/B]

FWIW, I like the idea of a decent heat shield. Bear in mind that the air intake is in front on the stock engine, but the S/C flips it to the rear of the engine. Don Moody already has something for the stock setup; you might want to just do something for the S/C enhanced crowd. Just a thought.

[paultvx]

I'm going to take a chance here... I think both parties of the SC fuel debate are correct.

I've been messing around with forced induction for a while now. Almost had a 400HP VW GTI... then life happened. Anyway, the Apline SC being a low boost system, it shouldn't *require* 92 octane. We're not talking about 9 psi and 100+ HP gain here. In the world of forced induction, 4 psi is really not that much. However, I wouldn't say that lower grade fuel is fine for all situations.

The VX's motor was not designed or built with forced induction in mind. Being naturally aspirated, it has relatively high compression ratio. Typical force induction motors have compression ratios of 8:1 or 9:1 to help avoid predetonation. There are other factors involved, like air/fuel ratio. But, compression ratio is one of them.

Since the SC's boost is low, lower grade fuel is probably OK for general use. However, I wouldn't say it won't ever ping. Amount of engine load, altitude, and numerous other factors can come into play and push the fuel's limits. A ping here and there will take their toll on the motor's internals in the long run.

I have to admit, the SC kit is pretty tempting. I almost jumped on it. But, having owned a SUV (Jeep ZJ) and a sporty canyon carver (GTI) I think it's best to have one of each. An SUV can never be as good as a sports car in doing what the sports car does best. And the sports car can never do what an SUV does best.

Perhaps my driving style has mellowed with age, but I actually find the stock VX's power to be decent. There have been times where I miss the GTI's ability to pass several cars with one quick excursion into the opposing lane. Then, I remind myself that being a few cars ahead is really not that important. One of these days I'll pick up a project sports car to fill the need for raw HP and speed.

Making a high riding 4000lb vehicross faster just isn't very cost effective... not saying there is anything wrong in doing it. If I had the means, I'd probably do it just for grins. It's just that for the cost of doing it... I can probably build a certain sports car into a 800 HP monster (no joke).

In regards to the intake... I thought the SC was made to work with the stock airbox? That's what it looked like to me in pictures posted on the pvmuffler page. Is the production kit different from what's shown in the pictures?

The kit would consist of a cone/cotton filter + heat shield. The heat shield mounts to the engine bay via one or more mounting points used by the stock airbox. The MAF would then be secured to the heat shield. It'll basically be like the Calmini kit, except instead of a bracket, you get a heat shield.

Whatever goes on between the MAF and the throttle body shouldn't matter (as long as the hose is long enough). And if the SC is designed to work with stock airbox, the intake kit should work for both SC and NA cars.

It's probably possible to make another kit that consists of a cold air scoop attached to a duct to feed cold air to the space the heat shield will create. Come to think of it... for those who do a lot of river/creek crossings, it's probably better to keep the stock box and have a snorkel for the box.

[paultvx]

Insomnia. So, I checked out vmag and did some reading on the Don Moody intake. Yikes. Looks like he had some unhappy customers. Not knocking the product... have no personal experience with it so can't really say anything concrete about it.

I think there is a misunderstanding on what was said earlier. The intake kit I will attempt to make consists of: heat shield + filter. Based on my experience from making a kit for the VW I used to have, and my friend's Eclipse Turbo... the factory plastic intake ducts are good enough to keep things cool. The only time heat might be an issue is when the vehicle is at a stand still (i.e. sitting at a red light).

I don't understand why most intake kits on the market these days are made of mandrel bent metal tubes... aside from the fact that it might look good under the hood. A metal pipe would conduct heat much better than a plastic hose would. That heat would transfer to whatever air is flowing through it. Not having a heat shield on a setup as such also defeats the purpose. Even if the metal pipe does keep intake charge temperature a little lower... what's the point if the motor is gulping down hot engine bay air? and the 3.5 does run a bit on the hot side (just like the VW VR6.) Someone mentioned they noticed their gas mileage drop with the Moody intake. I wonder if increased intake charge temp is the cause. Hot air... less oxygen... less efficient combustion... more pedal input to get the same performance as before.... maybe?

Anyway, my thought is if you use a good heat shield... one that seals OK against the hood... and one that basically acts as an airbox that encloses the filter... so that you supply the intake with plenty of cold air... there would be enough cold air running through the plastic intake hose to make ambient heat transfer (from engine bay to hose) an insignificant issue.

So basically, the goal is to provide the motor with air that is as cold as the stock airbox provides... but use a cone filter that has more filtration surface area than the stock panel filter. Same cold air as stock... just more of it.

I estimate the heat shield + filter will probably end up being $100 give or take $15. And, it should work with the Alpine SC since it doesn't really matter where the throttle body is located.

SC folks, can you tell me if the MAF and filter remain fairly close to the stock location? What I mean is... is the end of the platic hose in the same stock location or close enough to it (where it meets the airbox)? If you use the SC with the stock airbox, would you have to relocate the airbox at all?

[VX Monster]

paultvx,

This is what I love about this forum. Look at all that information. Paul - thanks for the brain dump, and feel free to do more.

And if you decide to do that kit, keep me in mind!

[paultvx]

I'm definitly going to make a heat shield... just a matter of when I get my hands on a filter. Hopefully soon.

After the heat shield, a carbon fiber intake tube to go from throttle body to MAF/filter.

Then, perhaps a full carbon heat shield. Best material to use to shield heat... The carbon bits won't be cheap though because each unit will have to be made to order by hand one at a time.

[Zu4two]

The compression ratio on the Isuzu 3.5 liter engine is 9.1:1.

The manufacturer of the SC recommends 92 octane fuel, so that the timing is not prematurely retarded from knocking.

There has been some research into the effects of a cold air box/cone filter on the VX. Search on the Vmag board under cold air box.

[ScottinMA]

Paultvx,

The vacuum or airtemp sensor is near the throttle body on the Alpine and the MAF is located just behind the airfilter. In order to avoid cutting wires to accomodate the new "hole" for the vacuum sensor (which is now closer to the filter than the OEM design), a rubber tube was inserted into the elbow "hole" and the tube was cut to length and the sensor inserted into the other end. This avoided a splice in the wiring and I've had no problem with it. On the other hand, the SC intake supplied with the Alpine is further away from the fresh air source and I would be interested in your design.

[Baxman]

Paul, you might also check threads on V-Mag regarding "the Don Moody Intake" for an example of how NOT to design, market and deliver a custom intake for the VX...

Rick

[SGT.BATGUANO]

With regards to wiring problems, I was wondering why an extension cable(s) couldn't be provided. What I'm referring to is something along the line of an extension cord or wire bundle with the appropriate male and female connectors on the ends? This might cost a little more , but it beats having to try to s-t-r-e-t-c-h wires (never a good thing). The proper connectors would ensure environmental protection and avoid the dreaded splice

[paultvx]

Originally posted by Baxman
Paul, you might also check threads on V-Mag regarding "the Don Moody Intake" for an example of how NOT to design, market and deliver a custom intake for the VX...

Rick

Already did. Scroll up.

[paultvx]

Originally posted by Zu4two
The compression ratio on the Isuzu 3.5 liter engine is 9.1:1.

The manufacturer of the SC recommends 92 octane fuel, so that the timing is not prematurely retarded from knocking.

There has been some research into the effects of a cold air box/cone filter on the VX. Search on the Vmag board under cold air box.

With 9.1:1, the system should be able to handle upwards of 9 psi with 92 octane gas. 92 octane with only 4 psi is REALLY playing it safe. Nothing wrong with that. Slight overkill... but nothing wrong with do so at all...internal motor repairs are very expensive.

However, a good aftermarket rising rate FPR (fuel pressure regulator) and a higher rated fuel pump is probably more cost effective in the long run than running high octane gas.

[paultvx]

What's the diameter of the flange on the MAF (where a cone filter would mount to)? Is it 3"?

Instead of waiting for my completely incompetent boss to supply me with a filter (which he promised... lying sack of ____ ), I think I'll just order one from NOPI and get the heat shield project under way. Strike while the iron is hot.

It's dark and cold out, thought I'd just ask instead of freezing my butt off while taking the airbox apart. Okay, okay. I'm lazy.

Oh, and I'll probably need a volunteer with an SC to see if the prototype heat shield will work with the SC too.