variable intake

[thedarkprince]

a lot of high powered, high dollar cars these days care coming with variable intakes, ones that change the length or flow of the intake. I hear the idea is that a long intake is better for lower end torque and a short one is best for higher end power. I would like to try this on my jeep, if only for the cool factor. I figure making a telescoping intake tube would be pretty easy, and there's plenty of length in that airbox area to get it to move a good 6-8". Anyone tried this or know if it would really do anything other than give the cool moving air filter factor?

 

[BLSXJ]

it is true that there is an ideal intake volume and length for every rpm.

if you want to do this please realise that you need to change the volume between the throttle body intake valves. and that it cant leak!

so break out that tig welder and your spare intake manifold and go to town.




BTW your probly better off just installing a 97+ intake.

 

[red91]

.
BTW your probly better off just installing a 97+ intake.

BAD NEWS...the 97 intake fits the following...

Cherokee 91-99
Comanche 91-92
G. Cherokee 93-98
Wrangler 91-99

you want the 99 up if you go that route

 

[Citat3962]

Probably a stupid question but does the 97+ intake manifold provide a performance increase over the stock 91 manifold?

If so I think I need to find one..... just for grins..

On topic::

The New VW VR6's have a variable length manifold.. the most common complaint on them is the variable length mechanism has a shift rod that rattles to the point it comes to pieces and no longer works... So the OEM's are still trying to figure this one out... might wait and find a Good OEM setup to copy..

That said this would be a massive project for a gain of about 10 HP... maximum..

But don't let me stop ya!

 

[BLSXJ]

oops my bad I thought they changed to intake when they changed the body. my mistake I ment the 99+


go jeep has a good write up

 

[thedarkprince]

I have the 99, and it's got that nice spiffy curvy manifold. So I guess its the distance AFTER the TB that matters, not before?

 

[BLSXJ]

you got it. changeing the distance from the filter to the throttle body does very little example. putting on a snorkel vs cone air filter FIPK setup they may add a few horse power due to ramair effct or more filter area and better less restrictive intake tube butthe length just doesn't really effect it

 

[Citat3962]

Nice gotta find a 99+ manifold and a good HO head to do some DIY porting and a rebuild..
Thanks for the info!

 

[JeepSpeed]

The old Ford Taurus SHO's had a variable type intake way back in the early 90's. It's actually pretty nice to look at, it's got 12 runners, 6 short and 6 long, and it closes and opens the sets at a specific RPM to follow performance.

 

[BLSXJ]

kinda like the honda v-tec

 

[JeepSpeed]

kinda like the honda v-tec

Not really. V-Tec engages different camshaft profiles at higher engine speeds to better match the engines needs. But the effect could be compared to variable length intake runners.

 

[BLSXJ]

I am not a honda guy (woo hoo)

sorry for the bad info

 

[ChicksDigWagons]

Yes, there are two ways to do it I reckon. One is two separate runners with a butterfly to change between the two, this is how every OEM system I've seen does it. The Fords and VWs for sure.

The way I've been thinking of tyring it on my is trombone style. Two aluminum tubes that fit fairly tightly, one machined to accept a pair of O-rings. Use some shock boots to keep out dirt. Then use a stepper motor on a worm-style drive and a programmable microcontroller to adjust the runners relative to RPM and possibly load.

Only problem is, on the subaru I have a limited space to work with, if I put the runners straight out they'd hit the hood. On the Xjs there is quite a bit more room to play with. The 4.0 has a wide enough RPM range that this may be sucessful, but, you'd probably have to use some soft of custom mapped ECU to really take advantage of it.

 

[FUNKYTEE5]

a lot of high powered, high dollar cars these days care coming with variable intakes, ones that change the length or flow of the intake. I hear the idea is that a long intake is better for lower end torque and a short one is best for higher end power. I would like to try this on my jeep, if only for the cool factor. I figure making a telescoping intake tube would be pretty easy, and there's plenty of length in that airbox area to get it to move a good 6-8". Anyone tried this or know if it would really do anything other than give the cool moving air filter factor?

I think that having variable length intake manifold runners would do alot more than having a variable length intake pipe! Just get a 99+ intake and call it good

FUNKYTEE5

 

[explorer]

Not really. V-Tec engages different camshaft profiles at higher engine speeds to better match the engines needs. But the effect could be compared to variable length intake runners.

Again, not really. I'm no expert on Hondas, but I'm pretty sure that they employ variable cam timing, not different cam profiles.

 

[ChicksDigWagons]

The original vtec had a camshaft with two different profiles on it that was hydraulicly shifted over to the other profile. The newest version uses both variable timing and different profiles to acheive even more adjustment. All the major Japanese manufacturers have their own version of this system now.

 

[FUNKYTEE5]

The original vtec had a camshaft with two different profiles on it that was hydraulicly shifted over to the other profile. The newest version uses both variable timing and different profiles to acheive even more adjustment. All the major Japanese manufacturers have their own version of this system now.

Yup V-tec gets the best of both worlds; a nice smooth idling low-end cam profile, and a big fat cam with lots of lift and duration to scream in the top end. That's why they make alot more noise when they hit about 3500 or so. I think it's cool

FUNKYTEE5

 

[thedarkprince]

yup and if tuned up right with an intake and freer exhaust like my old civic, you can feel it pull at the crossove (5,000 RPM on the civic, 6,000 on the RSX, 6,500 in the NSX I think) then again the cutoff on my civic was 8500 and on the rsx it cuts off around 9. I do miss some of that gear flipping toss the car around driving, but you know, I really wouldnt trade my jeep for that, so much better.

 

[2001XJeep]

Yes, variable valve timing is cool. Truly the best of both worlds when dealing with fixed mechanical camshafts and valves. Altering the length of the air intake hose/pipe prior to the throttle body will have no effect, other than possibly increasing intake restriction if you lengthen it too much. The whole point of the variable intake manifold is that changing the manifold's individual runner length changes the intake charge in relation to rpms. Usually longer intake runners equal better low-end torque while shorter runners are better suited to high end horsepower. Our Mazda Millenia with 2.5 DOHC V6 has a variable intake manifold, but no variable valve timing. Just another trick to flatten out the power curve of a small displacement engine and add some needed grunt down low. Works really well, but this is something the average home wrencher could not acheive, best left to the OEM's. The 4.0 doesn't need it anyway, got plenty of low end grunt to begin with.

 

[PapaPump]

I want to see soemone besides F1 using solenoid controlled valves. you have infinite control over lift, duration and overlap. you can have throttless induction and built-in egr for warm up. you could even use it to shut down cylinders in combination with the ignition. also there would be less friction and you wouldn't be limited by floating valves or too soft springs or any of the pushrod/rocker issues normally present. who is going to start this project?