Topic: Installing aftermarket air intake on 90 YJ

[chardrc]

I dont know. Thats why i am asking, But I cant really see much of your airbox. My 90 has three tubes coming out the back. Two thin and one thick.

those 3 tubes are vacuum hoses.. the big one is PCV in, and the other 2 are for the vacuum motor for the hot air door thing. take a look at this pdf... its basically what my 1990 is like except the TAC sensor part...
http://jeepgarage.free.fr/OWN/vacuum%20diagrams.pdf

[vprsrul]

let me get this straight - you're telling me that you're using the same filter in your 900hp (sorry, whp) that you use in your Jeep? Are we talking nitro? Just because in that case your oxygen is coming from the bottle and not thru your air filter and the dyno is completely irrelevant. not sure what we are comparing here. and no, you cannot possibly have 2 filters that have different filtering properties with the same flow rating, it's not possible (same size filters) - as for filtering properties that is a downside, no question about that but you compare a plugged filter with a brand new one which is defeating the point, compare 2 old ones or brand new ones. 

HAHAHAHAHA,  the 2.5 air filter sure will fit in my airbox of my truck(well my dads truck now :-(....... but it will fall right down into the bottom and go into the intake tube..... and im sorry I meant 900 ftlb of torque and 500hp, and you are wrong about the filters my friend.  a new k&n filter has very little filtering capabilities until it is about 60% dirty, so basicly the dirt is the filter..... and on an internally unmodified engine it requires an oem filter to be 80% occluded to show deminished power and economy on the majority of engines with no actual power gains coming from "just" and air filter replacment unless the one being replaced needed to be.  Its the hype that they sell everyone on with these filters and they don't give the full picture.  I used to buy into all that hype myself, but now realize the biggest loss in most intakes is the baffles, resonator box, and location of the incoming air to include the temp ofthe air where it is entering from.

[sharpxmen]

HAHAHAHAHA,  the 2.5 air filter sure will fit in my airbox of my truck(well my dads truck now :-(....... but it will fall right down into the bottom and go into the intake tube.....

my point exactly - you have a larger filter (the size matters) - your 8HP gain there just by replacing the filter is pretty good actually

and you are wrong about the filters my friend.  a new k&n filter has very little filtering capabilities until it is about 60% dirty, so basicly the dirt is the filter.....

actually I said the same thing, the better flowing filter will retain (filter) less dirt

HAHAHAHAHA,  the 2.5 air filter sure will fit in my airbox of my truck(well my dads truck now :-(....... but it will fall right down into the bottom and go into the intake tube..... and im sorry I meant 900 ftlb of torque and 500hp, and you are wrong about the filters my friend.  a new k&n filter has very little filtering capabilities until it is about 60% dirty, so basicly the dirt is the filter..... and on an internally unmodified engine it requires an oem filter to be 80% occluded to show deminished power and economy on the majority of engines with no actual power gains coming from "just" and air filter replacment unless the one being replaced needed to be.  Its the hype that they sell everyone on with these filters and they don't give the full picture.  I used to buy into all that hype myself, but now realize the biggest loss in most intakes is the baffles, resonator box, and location of the incoming air to include the temp ofthe air where it is entering from.

I don't work for KnN, it was just an example but by the looks of it (what you just posted) you probably missed this part at the beggining of the thread, so give it a read maybe that clears the issue 

buy a k&n filter and put it in your stock airbox. increase the opening in the front sheetmetal below the headlight and replace the  narrow square tube with at least a 2.5'' tube. remove the restrictor in the back of the airbox - that will give you same airflow as an aftermarket CAI. You can go even further by getting a larger airbox from pick and pull (junkyard) and get a KnN for that one and for best results replace the plastic/rubber hose with an aluminum pipe 2.5'' in diameter and use couplers and a reducer to the airbox if that opening is larger - this setup should be good for at least 350cfm if not 400, more than you need for the 4 banger.

just a bit more explanation here: your goal is to have minimal pressure drop at the required cfm - the pressure drop is related to pipe diameter, roughness coefficient (how smooth is the pipe inside) and the length of the pipe, so for longer pipes you want larger diameter, the smoother they are the better (mandrel bent aluminum, stainless or steel are best - cast plastic is rougher so it will have higher loss but you can get away with larger diameter). all the high perf filters have a cfm rating but the higher the number the better as it will result in less pressure loss which directly affects your VE - for example the difference between a 2'' pipe and a 2.5'' pipe for 20'' of length the pressure loss at 200cfm is 0.27psi, between 2.5 and 3'' is  0.05 psi - so the benefit of going to 3'' in this case is minimal, from 2 to 2.5 is more significant - of course there are other factors like couplers and bends - the smoother the whole assembly the less pressure loss and better airflow to the engine.
EDIT: using same parameters, the 1.5'' pipe vs 2.5'' pipe press drop difference is 0.9psi, going to 1.25'' gets the pressure drop difference compared to 2.5'' to 2.5psi for 200cfm - so you get the idea. The 2.5'' diam for Jeep seems the right compromise between the size and pressure drop, going to 3'' will not result in significant gains but at 2'' will be considered restrictive.

and to clarify something, you need to add a bit more fuel to the mix to get the best out of modding the intake - i'm not saying you'll gain 50HP but is good for about at least 4 if you get it right.

[vprsrul]

my point exactly - you have a larger filter (the size matters) - your 8HP gain there just by replacing the filter is pretty good actually
actually I said the same thing, the better flowing filter will retain (filter) less dirt

I don't work for KnN, it was just an example but by the looks of it (what you just posted) you probably missed this part at the beggining of the thread, so give it a read maybe that clears the issue 
and to clarify something, you need to add a bit more fuel to the mix to get the best out of modding the intake - i'm not saying you'll gain 50HP but is good for about at least 4 if you get it right.

Thats not what I posted either, I saw NO gain with just the filter, but with a complete intake ie tube and high flow cone filter I saw 8 hp at the wheels but none when the truck was mostly stock compared to the factory airbox and filter or k&n or airaid filters.  You are correct about adding fuel to one extent, air may get in faster but you will also have to address the exhaust as well.  I am certainly not trying to argue with you because you definatly make a valid point, but I was trying to enlighten you as well to the myth of the k&n filters(any oil types really).  yes its nice it will last a long time but it also allows debris in, overoiling the filter will also damage your maf as it did on several diesel trucks i have worked on, same affect on a gasser but I have yet to work on one at this point other than my own.

[sharpxmen]

Thats not what I posted either, I saw NO gain with just the filter, but with a complete intake ie tube and high flow cone filter I saw 8 hp at the wheels but none when the truck was mostly stock compared to the factory airbox and filter or k&n or airaid filters.  You are correct about adding fuel to one extent, air may get in faster but you will also have to address the exhaust as well.  I am certainly not trying to argue with you because you definatly make a valid point, but I was trying to enlighten you as well to the myth of the k&n filters(any oil types really).  yes its nice it will last a long time but it also allows debris in, overoiling the filter will also damage your maf as it did on several diesel trucks i have worked on, same affect on a gasser but I have yet to work on one at this point other than my own.

Neither the TBI or the MPI Jeeps have a MAF sensor - they both use a MAP sensor which cannot be harmed by the oil on the filter. So for all intents and purposes of this thread (Title: Installing aftermarket air intake on 90 YJ) not sure how is it relevant. The original poster asked this question as he could not find one for a 1990 YJ and i suggested an available (and cheaper) alternative to an aftermarket intake with almost the same results, i had no intention of discussing the dyno results of some diesel truck with which i have absolutely no experience or to discuss the pros and cons of aftermarket intakes, not to mention that in this case if you go offroading and it's a dusty trail it takes 2 minutes to put a stock airfilter back on to make sure it keeps the dirt out. If the thread title was "Is there any benefit on installing a KnN filter on xyz vehicle" I would have stayed out of it. My point was: rather than spending money on an aftermarket intake and piping use the current airbox, get a high flow filter, open the inlet, open the outlet, replace the connecting hose with a smooth metal pipe (ideally use a mandrel bent pipe and create an adapter to the t/b) and you will get almost if not the same results as the aftermarket intake for $30 or so.
the reason the aftermarket intakes have a more significant gain is because it addresses all these little things in one package which by themselves could be too less to notice but added up are something you could put your finger on.

For some reason we derailed the thread in this back and forth about KnNs and MAF and other stuff which is off subject and could be a thread on it's own so i'll stay out of it since i feel i got carried away and turned this into something else rather than what was meant for.

[C.Redbeardd]

Thanks sharpxmen. Anymore ideas to maybe put a little more performance back into the 90? My options seem rather limited compared to the later years.

[sharpxmen]

Thanks sharpxmen. Anymore ideas to maybe put a little more performance back into the 90? My options seem rather limited compared to the later years.

you could try to give it a little bit more fuel by increasing the Fuel pressure - chadrc has posted this link in another thread (don't want to take credit for it, so that is thanks to him, but it's good info so want to share it) - it's a pdf that explains the TBI fuel injection and also explains the way you adjust the fuel pressure - but do the high flow intake first and make sure you monitor the pressure when increasing it, you don't want to add too much (baby steps is best).
http://jeepgarage.free.fr/OWN/fuel%20injection%20system%20tbi.pdf

[C.Redbeardd]

Thank you so much. Ill let you know how it goes, or if i run into any problems. 

[sharpxmen]

Thank you so much. Ill let you know how it goes, or if i run into any problems. 

cool, post an update once you get that air-hog installed, interested to see what the first impression is.

[C.Redbeardd]

buy a k&n filter and put it in your stock airbox. increase the opening in the front sheetmetal below the headlight and replace the  narrow square tube with at least a 2.5'' tube. remove the restrictor in the back of the airbox - that will give you same airflow as an aftermarket CAI. You can go even further by getting a larger airbox from pick and pull (junkyard) and get a KnN for that one and for best results replace the plastic/rubber hose with an aluminum pipe 2.5'' in diameter and use couplers and a reducer to the airbox if that opening is larger - this setup should be good for at least 350cfm if not 400, more than you need for the 4 banger.

Sharpxmen, what did you mean by the 2.5 tube? Like just pick one up at an autoparts store and switch it out? What kind of tube?

[sharpxmen]

Sharpxmen, what did you mean by the 2.5 tube? Like just pick one up at an autoparts store and switch it out? What kind of tube?

any pipe that you can adapt there will do.

not sure what the tbi airbox has, but the mpi has a square tube that is restrictive compared to a plain 2.5'' diam round tube - your goal is to get cold air from behind the grill where the square opening is under the headlight (so that would be in front of the rad so it's not heated). Increase that square opening to a round 2.5'' and use a 2.5'' pipe or tube (can be even the drain pvc tubes from home depot but in that case i would go with 3'' as they are quite thick). Exhaust pipe works too, it's fairly smooth inside. you can also use flex hose, the aluminum one is sturdier - that one can actually be cut and opened inside the airbox and you can use some resin/epoxy to glue those edges. If not you can always go with a piece of exhaust pipe and find a way to secure it to the airbox.

if you keep everything at least 2.5'' in diameter you have minimum restrictions, so keep that in mind - if you use something that is not smooth inside then better to go to a larger diameter like 2-3/4'' or even 3'' (for the aluminum flex hose for example)

[C.Redbeardd]

ah gotcha. I believe that hose is curved downward too?

[dwtaylorpdx]

Be sure that when you increase the hole through the sheet metal by the headlight that
the air box inlet kind of matches it, but don't run a tube from the airbox through the hole
by the headlight. 94 YJ's had that stock and there was a tsb to cut it off or remove it
because they hydro locked some engines off-road. (It specifically a Off-road  problem in the tsb)

Howell used to sell blueprinted injectors for TBI, there is only 1 body for the "egg"
injector but several flow rates.

Dave

[C.Redbeardd]

you could try to give it a little bit more fuel by increasing the Fuel pressure - chadrc has posted this link in another thread (don't want to take credit for it, so that is thanks to him, but it's good info so want to share it) - it's a pdf that explains the TBI fuel injection and also explains the way you adjust the fuel pressure - but do the high flow intake first and make sure you monitor the pressure when increasing it, you don't want to add too much (baby steps is best).
http://jeepgarage.free.fr/OWN/fuel%20injection%20system%20tbi.pdf

do you you think you could also post the link to the thread?

[sharpxmen]

do you you think you could also post the link to the thread?

i think i can 

http://4bangerjp.com/forums/index.php/topic,7576.0.html