Single Filter box for trip webers ??

[240ZX]

Maintaining cold air to any type induction system, NA or EFI is a plus up in performance. With appropriate placement of the air inlet, one can benfit from the ram effect as well. So don't fool yourself into thinking a cold air induction system won't benefit a NA system. Thats a fact Jack!

Tom

[gnosez]

I was looking at the TWM cold air induction box myself earlier this week as I was thinking of replacing my ITG single filter on my triple 44mm Mikunis and called Rebello to see what they thought. They believe that the cold air box will become a warm-hot air box over time and without a heat shield it will only trap more hot air in front of the carbs. They suggested a better heat shield (good for 5-10 rwhp) and a cold air duct leading to the carbs. Of course I will need to rejet the carbs and dyno the engine with the hood open.

A little metal, an assortment of jets, and some duct work will do as opposed to spending over $350. on a cold air box. Thanks Dave....

[Curtis240Z]

I made my own cold air box which pulls from the stock 280Z hood louver. Check my gallery for pictures.

[TBK1]

curtis did you notice any performance diff!

Floor almost dry ,Time to get bac kto playing!

[dogma420]

It's 'not a fact jack' and don't call me Jack.

I mis-stated the previous post--replace carbs with specifically SU carbs, and that is what I should've said. Ram Air and Cold air induction does not help SU carbs is what I meant to say.

Go ahead and do cold air induction and do ram air with SUs--it doesn't help, it even lessens performance per people who have done it. The previous Z therapy owner (the Scott guy everyone despises for other reasons) had stated this a long time ago to me, after he tried it on his race cars. I can't remember, but the current owner (who is a member here) might have backed it up too, I can't remember.

I'm basing what I said on personal experience of others when I was thinking of doing it. I'm NOT saying the same holds true for any other type of carburator, just with the SU carbs, which operate much differently than any other NA carburetor you would put on the Z.

I wouldn't just bring this up because I'm blowing smoke. I don't waste time typing this kind of stuff out.

Actually, for most carburetors, the 'ram air' effect would be true; on SUs which rely on vacuum to draw the air/fuel mixture into the motor, Ram air doesn't help SUs at all--think about how the SU draws air in based on vacuum--it's inherent design means ram air isn't going to help. I'd have to find the evidence, but I went through this research 3 or 4 years ago--imo at the very least, cold air intake with SUs with the ram air effect, lessens performance of SUs.

[geezer]

I agree Dave. You can not regulate an optimal air/fuel mixture in this manner. A complete system is needed. Sure, it will benefit a car running full out for a quarter mile if correctly jetted. Also modern fuel injected, electronic controled vehicles, but not a street driven, carbed car based on 60's technology.

[dogma420]

I've seen the ram air setup on triple carbs, so I'm not saying that it doesn't work on cars that 'squirt' fuel into an engine (which means anything other than SUs)...and obviously, fuel injection is helped greatly by these items.

[Curtis240Z]

curtis did you notice any performance diff!

Yes. I originally had my cold air box when I was running triple 44mm Mikunis. I have an Air/fuel ratio meter in the stock clock housing and after installing the cold air box my mixtures were now lean. So adding more gas to correct the mixture with no other change means your engine is making more power thus needs more gas.

[TBK1]

well maybe I will shelve this project for now, not looking to have to rejet and not knowing whether the mod is benifical! Thanks for info guys!

[bjhines]

Here is my ram air box... although I would use the TWM airbox in a heartbeat before I made another one of these...

DCOE-45 series 152 with consecutive serial numbers... TWM manifold with their $$$ linkage...

Does it make a difference??? ABSOLUTELY IT DOES!!!! The metering is much more stable over a wide variety of conditions... street and track...

I have DUAL O2 meters installed from my previous SU install... I added a switch and welded bungs for 3 runners... I can monitor and compare any 2 of the three carbys for float level issues...

They are in PERFECT TUNE... just listen here... 130MPH redline in top gear haulin arse!!!! DEAD ON 13 to one... all the time every time... at any speed in any weather...

in fact I ran a similar airbox on SUs... It makes a huge difference... I even used the factory air cleaner with an extension hose on the snorkle with FANTASTIC results in the distant past...

Drawing air from the engine bay is dumb... especially considering the carbys are right on top of the headers and right behind the radiator's hottest area...

To add insult to injury most folks slap a flat plate on the carby inlets and completely IGNORE the benefits of the AIR HORNS in the factory air cleaner... That is one stupid upgrade right there... The runners are supposed to be as long as you can get them within the tight confines of the strut tower.... over 12" long at least... ditching the AIR HORNS is really really dumb...

[bjhines]

Ohhh... The Webers AND the SUs have balance ports on the intake mounting face of the carby body... as long as these ports are inside the same airbox as the intake horns... the carbys will balance out any RAM AIR pressure effect... SUs AND Webers... AND Holleys for that matter...

There is nothing special about the SUs that would make them perform any worse with a RAM AIR style airbox...

The Ram air effect is nil... very small pressure changes... The reason for doing this type of airbox is to get COLD AIR... Not high speed supercharging...

For anyone who thinks that your cold air box will become a heat sink.. install a freaking heat sheild and insulate your headers.. even then... the person who said that is taking a leap off the nebulous deep end... I can GUARANTEE that the air in the engine compartment is MUCH hotter than the air in a "hot" cold air box... Jeeeeeessuuusssss... gimme a break... people will spout fountains of BS at the drop of a hat...

ANYONE who has compared these mods side by side has first hand knowledge that CAI WORKS... ESPECIALLY on carbys... carby are MUCH MORE PRONE to heat issues than fuel injection systems... It is a sin to tell anyone that CAI is only useful on FI engines... That is exactly opposite from the TRUTH... Carbys can benefit MUCH MORE from a CAI system... for many different reasons...

[gnosez]

Actually bjhines, the person who I quoted saying that a heat shield and a duct bringing in cold air vs a "cold air box" works just as well if not better, was Dave Rebello. I'll stick with his advise, even if he is talking off the deep end since he got me 319hp@crank out of my 3.2L w/44mm Mikunis.

That fabricated box looks great and would indeed be a pain to build. I will add the heat shield, put in the ducting, fab up a semi enclosed box, re-install my O2 sensors, dyno and re-jet the carbs. I'll post the results in the spring after I take the car back out on the track.