Custom Intake

[John(XJ)Jeep]

Well it took a little while but I'm throwing up my idea here. Now it has gone through a lot of changes and from
what I was able to test it with since I have no access to any flow bench that can get exact numbers or even
a good estimate at this point in time is with just by feeling and watching debris fly through it heh heh, but the
difference is measurable easily by eye. I have done a rudimentary flow test with the air hose with the original
intake and the modified intake that I am currently running and was satisfied with the gain in flow but the margin
was almost undetectable but was able to discern the difference by eye. Enlarging the bore of the inlet
of the manifold to 71mm did produce better flow rate. For most of you that was/or is pretty obvious.

I don't actually feel (meaning I'm not exactly sure) that there is so much a difference in fuel delivery between
runners that it should matter. I could be wrong or right since any information I have found about has fierce counter
arguments. Judging by the amount of debris and runoff around my injectors, valves, chambers, runners at the head
ect. when I rebuilt my engine there is possibly none but of course that can probably be answered by a reader I don't
have and for the moment don't even have access to one. So I just went on with my hunch and started building
anyway.

Now this is totally experimental and it should yield a good amount of R&D to me after a real life test but I think
it should succeed with great measure. The concept was to have an intake that acted like a velocity stack setup
mixed with a plenum configuration, lol I don't know what the best words would be but it's a little hard to describe.
It's not a brand new idea by any means but It should be somewhat new to the 4.0L engine which is the only reason
I'm really even bothering with this so bear with me if it flies in your face to some of you. For the longest time I've
always wondered why there really isn't much aftermarket support in terms of on-road performance upgrades for the
XJ's and MJ's. Of course, most Jeep guys think that our vehicles are the purest for the off road but I always thought
because if our unit-body design, one of the lightest and surprisingly most aerodynamic (try not to laugh, I'm serious)
of the the Jeep brand why not more people used it on the street scene? This makes it hard to make anything work
for us. So I like to experiment and I hope this actually helps us all. Along with experimenting with the suspension
which will come on another thread I want to make the baddest XJ there is on-road.

Alright, now that I got that out of the way. Here is some pictures of what I'm building. Like I said it looks a little
ugly now but it works and it works far better than I thought it would.


This is what I started with, stock intake and some I guess "upper" TB's from two 2K Lincolns from the scrapyard.
I get to chop off that ridiculous Chry-Co symbol and basically use 2 ford TB's, to some, not a very good start heheh!



Now I'm modifying the TB's to adapt. I needed the bottoms flat so what do you do? If your me you file them, good thing I'm
a great filer I managed to file them flat to match the machine ground block. Which was incredibly hard and time consuming
but was no problem to do. I also decided to lessen the angles of the TB's above the bore and smooth them out. All it I did
was really trumpet the bores a little more trying not to change the shape too much.




Now building up on aluminum cast is a hard thing to do especially if you hadn't done it before and decided to do it on a project
such as this, with a stick welder mind you. So it looks shitty but they are solid and strong and at this point that is all that really
matters sure as hell you can see I didn't care about looks. Anyway I digress, I had to build up the walls of the ports so that I had
material to weld the extra aluminum to make the mounting flanges.

 

[John(XJ)Jeep]

Here I make the rest of the plenum body pieces and the transitions for the TB's. Now here is an issue with the transitions, this section here
will more than likely act like a collector than just one of the sections. In this section I expect the intake charge to slow down bit here and
may cause a problem with turbulence. But since nothing is together yet I won't know for sure how bad it really is. It is minute but maybe if
I'm lucky what's going on behind the butterflies will compensate for this. All n'all I will be making better pieces for this section in the future.




I make some extra welds to fill up some gaps in between the plenum flange and the runners. As you can see I gave the runners a bit of a porting and
squared the port shapes to better match the straight line running of the plenum. This part here need to be flat as well also done with a file, also took
forever to do. I weld the back piece on and tack the side pieces on as well. Starting to take shape.




Now this was a little tricky to do but I managed to get a decent airtight weld but it looks like ass hahahah! I'll probably clean it up and redo it and probably
paint it over to make it look somewhat nice, but you know.. Anyway, I weld in the connection for the vacuum lines and drilled hole which are ready to tap
and put in the remaining walls of the plenum. I tack the spacer plates to the top piece and cut out the middle section in a "C" shape so I can get in there
with the welder and so it doesn't look too much like ass. In the last picture you can see the flange and it's an abrupt wall there well there is going to be a
baffle there to help direct air and proportion the airstream (hopefully) in the roughly the proper amount to each runner, if I said that right. It is a very hard
shape to get right so I'm still working on that at the moment but in essence it is nearly complete. TB linkage and placement is the last phase and hopefully
I don't get too much trouble there.



There is still few tweaks I may need to do to it before I permanently cut off access inside but very little is left. As I said before this setup flow like crazy for
what I can tell. I can get better flow using my own lung power 10 inches away from the opening than using an air compressor at the opening on the original
intake manifold, that's the difference. But of course that doesn't mean jack to some of you and as of now it doesn't mean as much to me as well until I get
the TB's and intake tubes on and test it against the old modified setup.

I will be working on it all this week and hopefully I can get this finished by next week along with my SS exhaust, engine and trans mount too.
I'm hoping the intake and exhaust mods will take well and substantially boost the performance of this motor. I will give final details when I'm nearing
the installation.

 

[XJEEPER]

Wow! Amazing project with limited tooling. Anxious to see the net results.

 

[Talyn]

Nice work!

 

[CobraMarty]

Looks good. Wasn't that dual TB tried in the past and there was a clearance problem and ? hit the brake booster?

 

[Talyn]

Yes there was one that hit the brake booster. It used two stock throttle bodies.

Hesco's take:

 

[CobraMarty]

Nice, what ever came of that HESCO intake. Ever made? Available?

 

[Talyn]

I'm sure they will make you one if you ask.

 

[XJLI]

That thing is bad ass

 

[John(XJ)Jeep]

Ye there was that but I solved that problem. I needed 10.5" of clearance and got it at
10-7.16". It just clears it, I thought I was gonna need a different Brake Booster but I
made it work.

The only major issue is hood clearance, because I'm jacking up the engine to lower it the
intake tubes stick way up so I need to modify my hood to clear them. But that problem
was taken care of too anyway because I'm building a big bubble cowl on it (Mustangish)
on the outer body lines of the hood.

 

[Dr. Dyno]

That thing is bad ass

Indeed it is, but I bet it would cost a lot less to make your own Double Trouble. Unfortunately I see three problems with it.
Firstly, you wouldn't be able to use the throttle cable bracket in its original position, so you'd need to modify it (or fab another one from scratch) and shift the cable towards the front.
Secondly, you'd need two intake tubes (one for each TB) so somehow you'd need to fab a custom Y-pipe from the air filter. That's challenging enough because of the lack of space and potential hood clearance issues.
Thirdly, with two TB's you'd have twice as much air as normal bypassing the throttle blades when they're closed so you'd have a very high idle. You'd need to block half of each bypass slot so that you have half as much air going through each TB but with an even distribution in the manifold.
Hesco's DT didn't go beyond the prototype stage but I'd take my hat off to anyone who could pull this off successfully in his Jeep. Mmmm, now that's got me thinking about what to do as my next project.

 

[John(XJ)Jeep]

Thirdly, with two TB's you'd have twice as much air as normal bypassing the throttle blades when they're closed so you'd have a very high idle. You'd need to block half of each bypass slot so that you have half as much air going through each TB but with an even distribution in the manifold.

The first two problems mentioned I already have solutions for but the third one I'm still trying to decide
on what to do about that. Since these TB's don't have the vacuum and idle motor adjustment's on
the upper's there's no real way to implement them physically. I only need one off of one pipe so I could
fab up a box with idle step remotely and route from one of the vacuum lines or build something directly
to it. Another option is to file the butterflies for a tighter fit and create a mechanical bypass which is
very hard but can be done also, less mess with extra parts but I have to babysit the throttle till it warms
up. There really is no other good ways of doing other than those two. Right now it kills itself with the
idle motor so I had to grind a slot so air can bypass with it fully shut, it forces itself to shut and stays
shut for the entire trip. It would be safe to assume that it's not really integral to the idle staying normal
since after it's warmed up it idles normally without problem while the step motor pretty much disabled itself.

Anyway one of those two options will end up be used. I'm going to try the single pipe source and route
through the vacuum tube and if that looks too ugly and does the same thing what it is doing now currently
I'm just going to take it out completely and modify the butterflies to make a mechanical bypass.

Currently the TB's don't have bypass holes in them and I have noticed on my first intake that it didn't have
them either. It would not let enough air through for the motor to run. So I will test that first and see what I
need to do after wards.

 

[Vanimal]

just weld on a plate for an idle air control valve somewhere on the manifold. an early ford one would be simple to mount, however i'm not sure if it will plug and play with the jeep's electronics. never looked at the jeep one as i havent had a problem with my heep yet (knock on wood).

 

[Dr. Dyno]

There really is no other good ways of doing other than those two.

You could drill a small hole in each throttle butterfly instead and block off the idle air bypass slots altogether.

 

[seanyb505]

What if you just modified one of the TB's to be closed at 0% throttle? As you give it the beans it functions like a normal TB, but it does not let air through at close?

 

[yossarian19]

So, aside from epic coolness what would a double throttle body intake do for the average xj? I just don't see it except maybe in a heavily ported head w/ cam & stroker, but even then a 68mm tbody should do it?
Aren't you just way out flowing the head at this point?
But...
Epic cool.

 

[CobraMarty]

My thoughts. Same basic stock manifold but with larger/multiple TB.
Where is the bottleneck? What do you want to boost? Low end TQ, or high end HP?

I could see more with this design with shorter runners and a larger plenum.

Still excellent work.

 

[Driftunit]

Wow, ill say custom lol

 

[O-Gauge Steamer]

So, aside from epic coolness what would a double throttle body intake do for the average xj? I just don't see it except maybe in a heavily ported head w/ cam & stroker, but even then a 68mm tbody should do it?
Aren't you just way out flowing the head at this point?
But...
Epic cool.

Insofar as that goes, both a 68mm (have one...) and a 70mm TB are available from F&B.

But the cool factor of multiples can not be denied. The ultimate, of course would be 6 small TBs mounted in a near horizontal orientation. Which I dimly remember as having seen the photos of. I think the guy used TBs off of a motorcycle but, could be wrong...

Still, a centrally mounted IAC could be fabbed up to resolve the idle issue. Given what has been done so far, a simple addition to a great looking piece of work.

 

[XJLI]

I
But the cool factor of multiples can not be denied. The ultimate, of course would be 6 small TBs mounted in a near horizontal orientation. Which I dimly remember as having seen the photos of. I think the guy used TBs off of a motorcycle but, could be wrong...

I would do ITBs in a second if it could help make my jeep sound like it had a BMW S50 motor in it...