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JLT CAI vs headlight pulled CAI

3.6K views 29 replies 17 participants last post by  Ratt Fink  
#1 · (Edited)
Everyone knows the JLT CAI is tops for making power on the dyno. And the track. It can be attributed to many factors (piping, large filter, not exposed to engine heat...).

But I am wondering how a properly setup RAI (NOT EXPOSED TO ENGINE HEAT)would perform at the track compared to the JLT..

say a modified box that would get fresh air from the headlight area. Would require some hacking of the headlight frame/bucket area...

I have to think that exposing it to forced air would be better than "in the fender".
 
#3 ·
IMO, in a supercharged car as long as the air is the same temp I don't think it will make a difference. My reasoning is that with a blower car you'd have to be going pretty darn fast to be getting any kind of ram air type effect that I think you are eluding to. When it all boils down, remember that a supercharger is nothing more than a large air pump. blowing air at a higher pressure on one side and sucking it from the other. Again you'd have to be going pretty fast to build enough pressure on the "sucking" end of your supercharger to pressurize the air inlet.
 
#5 ·
The way I read it he was asking to compare a JLT intake that gets its air from the fender well to a setup that would get its air from a removed headlight area. He also reffered to an RAI, doesnt that stand for ram air intake?
 
#6 ·
I think a good ram air would have a decent effect on boost at high speeds. Considering that ~100mph is enough air pressure to hold my body up in freefall I'd assume that there is some pretty good pressure developed even above about 60mph with a ram air. We all know that restrictions on the intake side reduce boost and hp so force feeding the intake should cause more power. Where is black2003cobra with his superior math skills to calculate it out for us?
 
#7 ·
Well maybe someone could do the math for us but Do you realize the amount of air flow that is being pulled in through your intake? I seriously doubt that equals the amount of air that would be funneled into the intake at 100mph, or even 150mph. The reason that 100mph is enough to hold your body up is because of the amount of surface area you expose to that wind. I think the actual number is closer to 120mph. There is not a lot of surface area that you would be trying to funnel that 100mph air into to get any kind of ram air effect.

I have a shaker intake on my car and before I put on a CAI I did some testing on the system. If I blocked off the stock air inlet with and only used the ram air scoop and air inlet from it channeled into the intake I lost 2mph in trap speed in back to back runs with stock intake inlet unblocked. I repeated this test on several different trips to the track so the drop in trap speed wasn't do to heatsoak or anything else.
 
#14 ·
That's kind of my point...This past Fri night I drove the car to the track on my 18's and was trapping 127.xx all night. (1.9x 60' times...)

Pulled the headlight and trapped 128.xx This was on a warm motor with consistent 15 min ice cooldown period.

My problem with the Steeda CAI is that during staging the IAT1 creeps up quickly. I need a box that'll be closed off from engine heat, but open to accept air from headlight.

I know Ram air may not be as beneficial on a SC car, but the idea of positive pressure from outside has to have a good impact when compared to an in the fender setup... The question is how much

I dunno, maybe it's just the fact that I was putting cooler air across the filter.
 
#9 ·
True, but the shaker intake has huge bends and is nothing close to straight. I've heard something like you cut down your CFM by 20-50% with each 90* bend in HVAC. You make a good point about the surface area. I can actually fall as slow as 90mph when i "puff up" and over 150 in a sit, but yeah they use 120 as an average speed.
 
#10 ·
I will do some datalogging tonight, hopefully I dont get pulled over by the COPS.

I have a 12" Filter on mine, with a stock intake tube, I will do both comparisons at full operating temps. I always run without a headlight at the track, the cooler the motor, or air in the bay, the more power it will make
 
#11 ·
I know I did a lot of back to back same day testing w/ 9" open filter with heat shield and tube from fog light/12"open filter w/tube from fog light (both with headlight out and 4" upper pipe) vs the equvilant to my JLT high boost 12" setup. (had the 4" upper pipe and I fabbed some 4" abs plastic to the fenderwell which is a crude version of what my JLT is now. My 9" filter went over 200* IAT2's before I got into the top of 4 gear. My 12" filter was in the 180-190's if I recall. And my fenderwell/JLT air kit was in the 170's max. All same day, all back to back. IAT1's were very close within a couple degree's. I also datalogged my JLT at Atco '05 race(track temps were 145* air temps were in the low 100's. With ice in my Blown03 box at 27psi I saw a max 133* IAT2. There is a huge difference. All street testing was done with no ice. It was mid 90's outside and humid.
 
#12 ·
I know I did a lot of back to back same day testing w/ 9" open filter with heat shield and tube from fog light/12"open filter w/tube from fog light (both with headlight out and 4" upper pipe) vs the equvilant to my JLT high boost 12" setup. (had the 4" upper pipe and I fabbed some 4" abs plastic to the fenderwell which is a crude version of what my JLT is now. My 9" filter went over 200* IAT2's before I got into the top of 4 gear. My 12" filter was in the 180-190's if I recall. And my fenderwell/JLT air kit was in the 170's max. All same day, all back to back. IAT1's were very close within a couple degree's. I also datalogged my JLT at Atco '05 race(track temps were 145* air temps were in the low 100's. With ice in my Blown03 box at 27psi I saw a max 133* IAT2. There is a huge difference. All street testing was done with no ice. It was mid 90's outside and humid.
F8L besides the cooler IAT's did your short times or MPH differ from one set up to the other?
Thanks, Mark
 
#18 ·
IMO, you're not going to have any help from any "ram air" on a blown application. As for pulling out the headlight, the only reason people gain there is due to the cooler denser air they are allowing the filter to breath in. If the vehicle is already sucking air in from an area that isn't subjected to the extreme underhood engine heat, like the 12" JLT CAI system, then this will be as good as you can get.

Regards...
 
#21 ·
I have picked up to 3 mph with headlight out with 12" filter......so naturaly I always have it out if I am at track.

James has a JLT CAI 12" kit on the way for my car now......so I don't have to worry bout pull headlight out and due to just an open air filter I had underhood.......Might even pickup some Mph and HP.

He is going to dyno car as soon as it installed and put on.....

:beerchug:
 
#22 ·
I know 2 guys with the same upper that made 45x/45x with a JLT to my 46x/48x with the K&N FIPK Gen II

Different things work for different cars I guess.
 
#24 ·
If it's not the "ram" effect, but the temp of air change by removing the headlight that is giving the ET then the best thing to do is get the filter where the air is cooler ALL the time, not just when at high speed.

Ok, I have both style kit to make all sides happy, but have never sen the RAI make more power... on the dyno.

So lets say you take the time to build a sealed box that only gets cool air from the headlight area and the hole in the fender apron. You will be blocking the filter from air in normal driving conditions and still get higher IAT 1's due to the filter under the hood. Yes, it's blocked off, but that box will get hot as well. Those with the Steeda, take a temp reading of that S.S. shield after a run or a hour of driving. It's hot, it surrounds the filter and the air around the filter will be hotter as a result.

If you want to do this you might as well keep your stock air box and cut the front off.

OR, you could get the filter in a cooler area 100% of the time with the JLT CAI and 12" CAI.
Between Tommy (F8L), Dave King, James @ RWTD and many others who have data logged and posted there results of much lower IAT1's and 2's with a full fender well kits, you know the powers there, but it's up to you to get it to the ground.
Tommy has by far done the best of data logging at the track and on the street and uses the JLT to get that silver monster down track.

Bottom line is if your IAT's are lower the car will make more power.

Thanks guys,

Jay
 
#28 · (Edited)
Any bend right before the meter is going to create turbulence (especially the flex tubing like you're stating), which in turn will throw off VE, which in turn will throw off spark and fuel calculations. Please *never* do this!

JLT's 12's CAI system is fine in this regards, because you have over 6" of straight tubing before the MAF (actually I believe it is a solid 8"+).

Ratt Fink, and everyone, in regards to my statement about ram-air for a supercharged situation, yes there would be benefits of having a "true" ram air, but it is near impossible to gain any real ram air effect from what limitations that we have in attempting to achieve such, and that's what I was ultimately getting at. A ram air hood on the F-Bodies was purely a joke, and only worked to achieve cooler air. I have datalogged before/after results on F-Bodies on the dyno and on the road, and the MAF *never* saw an increase in aircharge, even at speeds above 100+ mph!

Sincerely...
 
#27 ·
This is a good discussion. For a car driven mostly on the street, I have to believe that the JLT in-fender setup has to be the best setup to provide cooler air when the under-hood temps are high. It all makes good sense, and has to be the best bet !

For me, though, I use a tube connected from a fog light hole to a large funnel-shaped cone that empties right against a 10" powerstack type filter located behind an Amazon plastic deflector, and feeding through a stock inlet tube to the throttle body. I believe it feeds the blower better at speed, with a much straighter path of the "controlled" air.
When decelerating to come to a stop, and the throttle closed, my engine will not drop to the normal 800 rpm idle with the car moving at anything over 25 mph. It will stay about 1100-1200 rpms, meaning some air is still getting pushed around the TB blades.

Yes, I think a ram system will serve a positive-displacement blower well. Think about any GMC huffer race car, and you know the inlet is designed to catch air as much as it can. OK, that is a "race car". If eliminating restriction did not help, then porting and polishing the blower intake would be worthless, right ? A larger throttle body, or polished throttle body, would also not be useful - velocity would just increase going through the smaller hole(s) if the blower had no problem "sucking". The fact is, adding any amount of extra "pressure" to the suction side of the blower will increase its efficiency and/or increase discharge boost.

Perhaps a JLT in-fender system with a ram-type tube feeding air to it would be of value ? For racing maybe, but having rain, road dust, etc, being blown in there for normal daily driving is likely not the best idea. Keep the ram stuff for racing, IMO.

All food for thought. My car is mostly used for racing.
 
#29 ·
This is a good discussion. For a car driven mostly on the street, I have to believe that the JLT in-fender setup has to be the best setup to provide cooler air when the under-hood temps are high. It all makes good sense, and has to be the best bet !

For me, though, I use a tube connected from a fog light hole to a large funnel-shaped cone that empties right against a 10" powerstack type filter located behind an Amazon plastic deflector, and feeding through a stock inlet tube to the throttle body. I believe it feeds the blower better at speed, with a much straighter path of the "controlled" air.
When decelerating to come to a stop, and the throttle closed, my engine will not drop to the normal 800 rpm idle with the car moving at anything over 25 mph. It will stay about 1100-1200 rpms, meaning some air is still getting pushed around the TB blades.

Yes, I think a ram system will serve a positive-displacement blower well. Think about any GMC huffer race car, and you know the inlet is designed to catch air as much as it can. OK, that is a "race car". If eliminating restriction did not help, then porting and polishing the blower intake would be worthless, right ? A larger throttle body, or polished throttle body, would also not be useful - velocity would just increase going through the smaller hole(s) if the blower had no problem "sucking". The fact is, adding any amount of extra "pressure" to the suction side of the blower will increase its efficiency and/or increase discharge boost.

Perhaps a JLT in-fender system with a ram-type tube feeding air to it would be of value ? For racing maybe, but having rain, road dust, etc, being blown in there for normal daily driving is likely not the best idea. Keep the ram stuff for racing, IMO.

All food for thought. My car is mostly used for racing.
So Ratt gets what I'm saying. And Ideally I'd like to find one of those Amazon or like airboxes to modify like you have done.

Good analogy with the RACE cars S/C intakes... And yes, this is all about getting more at the track. I have not much care if my IAT on the street is 30* higher at any given time...

Can you post some pics of your intake Ratt- The box itself if you've got any?
 
#30 ·
Yes, I have some pics. The Amazon cover on and off the car, and the Ratt Ram Air II system off the car and then showing how it dumps air at the air filter location.