XJNKY

So, I posted this question on JF too, but I like Cherokee Forum, so let's see what you guys think.

I'm very slowly gathering parts for a stroker build (have been for 3 years, I'll get there one day). I've been reading about the supposed benefits of the 99+ horseshoe intake (better air distribution, more even runners?). So, that got me thinking, I've seen older straight 6's with multiple carbs, why not multiple TB's on a custom intake instead of just one large over-bored TB? Seems like it would be simple enough to machine a plate, cut the intake, and have someone weld the two together. Linkages could be fabricated fairly easy. So I did a little research, and found just a little info on the (failed) Hesco Double Trouble intake prototype, which apparently did just that, but also just gave the 4.0 more air than it could handle. I found this over on NAXJA :
Seems logical enough. So, my thoughts are that if you were determined to make a custom manifold anyway (I'm not, but it seems like it would be a fun project if I had the setup to weld Aluminum) why couldn't you just run two 2.5L TB's? I'm sure dual 2.5TB's would adequately feed a stroker. 22hp seems like an unlikely gain, but you know how those internet quotes go...

Someone discuss this with me. Call me an idiot or something. I'm just looking to spur some technical discussion. Curiosity has got ahold of me.

How would you manage the MAF or IAC?

Anyone want to bite on this one?

macgyver35

Without going into too much technical detail, even if you get past all the other technical and logistical nightmares, I think this would be extreme overkill, if not outright detrimental, even for a stroker. The only reason to do dual throttle bodies would be to provide enough air to match the amount of fuel being delivered. Unless you are going to put some kind of crazy-high output injectors and fuel system, you don't need two throttle bodies. Just because you have two TB's doesn't mean you are actually going to get any more air in the cylinders to support higher fuel rates unless you turn to forced induction of some kind. And even if you are going to build a 350+ HP stroker, your better, more reliable, and technically feasible option is to put a Mopar or Banks supercharger on the thing and call it done.

Why reinvent the wheel when there are options that already work well with existing fuel and engine management components, and has been engineered and tested for long-term performance and durability.

Oh, and however you end up making more power, don't forget that you have to keep in mind all the components in between that get the power to the road. Trans, U-joints, clutch.torque converter, etc. Figuratively speaking, you can't just throw a V8 in a go-cart and expect a good outcome.

99 Purple XJ

A guy on here tried a dual tb setup he gave up on it after a while its alot of work for not so much gain

Gorillaxj

Agreed, I ran a 60mm TB (had a member on here bore it for me) Ran awesome. the stroker will be enough.. trust me, the work for duel TB's isn't worth the effort. it would probably be close to the same work/cost to turbo/SC charge it and you would have a lot more gain.

Make sure you use a really good machine shop... Mine failed me and bored the cylenders to tight and eat up the pistons skirts in 900 ish miles... (i used one of teh top 2 machinists in my state, still happens!)

offroadordnance

The older engines had fuel distribution issues due to the wet manifold design. Fuel was delivered by the carb in the central location and some cylinders ran rich and others lean. Fuel atomization issues related to air velocity, jet size, Venturi diameter, runner length, were minimized with multiple carbs. There were also issues with fuel sloshing out the bowl vents at extreme angles. Side draft carbs, such as Webber's didn't have the problem and were an option on early Rovers. FI with a dedicated injector per cylinder resolves the distribution issue ensuring the same A/F cyl to cyl. I wouldn't use the old multi carb intakes as a basis for dual or ITB. ITB's are great for high revving motors that benefit from short runners.

Metmknice

Go with something like Hilborn Injection if you do something like that.

XJNKY

All excellent points!
See, this is the sort of semi-technical discussion I was hoping to spur.

Although, I don't really think it would be all that expensive. A 99+ horseshoe intake I already own, a plate of Aluminum, some machine work, some welding labor, and a couple junkyard TB's from 4cylinders... not nearly what a Supercharger setup would cost.

But the carb vs MPI argument is rock solid. The thing you're looking at with different intake runner layouts is air velocity, not necessarily fuel distribution. In this case, I suppose you'd be arguing fuel atomization (due to velocity@ the injector location) as your real difference, and I'm not really sure 2 intake ports (TB's) would dramatically improve that situation. Probably wouldn't be any more effective than one of those stupid throttle body spacers.

I suspect there would probably be an increase in throttle response, but it would probably be marginal(?)

So, anyone have any thoughts on the supposed 22hp gain rumored to have been found on the Hesco setup? Seems unlikely to me, especially since I believe it was insinuated to be on a stock 4.0L. Maybe it was supposed to be 2.2hp...?

XJNKY

You have to admit though, it'd look awesome...

...

Just kidding, I'm not that stupid.

Gorillaxj

If you just weld on a plate and randomly locate the TB's then sure it could be cheap... I thinking the proper way of flow testing them to make sure the runners where all being equally fed, then having it tuned on a dyne to maximize the HP gains which I am almost sure the 22 HP setup was., programming/dyno time is not cheap, redoing the manifold for changes more then once almost doubles the cost of the manifold as well. Its adds up. you could be able to turbo almost any car with a Home made setup for about $1500 +tuning. I based the amount from above stated cost of $4500 in total cost for a one off manifold tested ect... obviously it could be done cheaper, but as accurate with the 22hp gain or more? questionable. not saying don't try, but 22 HP isn't enough to justify $1k IMHO.

Throttle Body Spacer
Myth: Adding a throttle body spacer will increase the intake plenum volume for more air and a higher velocity intake charge. Also, rifling an aluminum spacer helps air flow into cylinder head with less turbulence for more power.
Our Thoughts: Depending on the application, a spacer works wonders on a carbureted or a TBI-injected engine in which the air/fuel mixture atomizes and flows through a wet manifold, but results are less drastic on a MPI engine in which only air flows through the intake.
Claimed Gains: 10-15hp
Actual Gains: 0-3hp
Notes: With our Red and Mileage Master projects, the largest power increase we've seen on the dyno was 1hp.

1 HP is a normal difference from one dyno run to another same car, same dyno, same day, its not a real increase. I don't think one would hurt, but I don't see the $$ being worth it.

if anything at all. A bored throttle body will though. A factory TB is 60mm at the top, and 58mm at the bottom, I noticed a difference with a 60mm straight threw. I would imagine a 62mm on a stroker being better, but it was still great with a 60mm.

I don't know anything about the hesco setup so I'll leave that to someone else.


On a side note... hope you have your bases covered for cooling.

XJNKY

I think we're talking about this on two entirely different levels. There's a difference between fabricating it and engineering it. But, for the record, I have the ability to do both (well, simulations, not actual testing). I have access to fluid dynamic simulation software, so, technically I could model all of it, and run simulations to try to find the best location in respect to velocity and even distribution. I wouldn't, of course. I'd probably measure the distance between the intake ports, and split the difference. Not the most scientific method, but that would be my baseline for the simulations anyway.

But, that's all hypothetical, because you guys have all presented some pretty solid cases for why it's a pointless endeavor.

And it's not like I'm getting ready to start on building the stroker this weekend or anything. Like I said, I've been slowly collecting parts for the last couple years. It's one of those "one day" projects. I have a 4.0 with 220K from the same year XJ, and a donor 4.2L from a junkyard to scavenge the crank and rods from (obviously, they'll visit the machine shop first). I've got all the gasket sets, head bolts, horseshoe intake, and a few other miscellaneous parts. Still trying to decide what bore to go to, and whether or not it's worth the extra ponies to try to run a high compression setup. My understanding is they're harder to keep cool, and whatever small power gains come from them are not worth the headache, or premium gas.

Which, btw, my current setup is a 3 core and 160* thermostat, with a 2 year old cooling system flush. In 98* summer heat, I still never get over 160 going down the road (even towing), and rarely touch 200 crawling on the trails. I did actually get it hot once last summer, but I popped the hood, smacked the thermostat housing with a wrench, and it dropped 30* in about 20 seconds. "Someday" I'll upgrade to dual electric fans... just don't have a need to yet.

Oh, and yeah, I know the TB spacers are a joke. They have a slight gain on TBI or carb systems, but are nothing more than expensive underhood bling on a MPI system. Even if they're rifled. You don't want turbulence at that point in the system (for MPI). The longer you keep the flow in the laminar region, the better velocity you're going to get. Where you want the turbulence is where the fuel is introduced to the system (so basically at the head for us), so it has a better chance to atomize. Any turbulence before the fuel introduction point is just creating unnecessary resistance, and slowing your velocity.

macgyver35

While this may be an "interesting" scenario to discuss and daydream on, I still feel that doing this would be a Rube Goldberg approach to improving performance and gaining power (look him up).

Aside from the nuts and bolts of how to weld and machine a dual TB manifold, areas that haven't even been touched on:

What do you do with MAP sensors?

What about throttle position sensors?

What about Idle air controllers?

Will this even actually cause a higher intake charge of air to support a higher amount of fuel to produce a higher amount of power?

Will this ever pass emissions?

Will it be reliable?

What kind of one-off customized electronic control module will have to be designed and built to deal with the splitting/combing of signals and power to/from all of the above sensors and controls that will integrate with the existing PCM? This isn't duel carbs we're talking about.

I realize that this appears, at first blush, to be a "cheap" project. But cheap is only good if it works well, and doesn't demand reinventing the wheel to pull it off. I still maintain that if you want to build a stroker, and you want to truly get more (reliable) power, you can get a package that someone else has already spent the time and big bucks to properly engineer and test... Get a Mopar or Banks/Eaton/Ken Bell supercharger (gaining you 70-90 HP, not 22), or some kind of turbo if that's more to your liking, and be done. I don't mean this to be insulting, but this quest you're on has all the signs of some back-assward, southern-engineered, "spending a dollar to chase a dime" project, if you even get it to work at all.

I think you're just as likely to gain 22 HP (at somewhere around 4200 RPM), which is about a 12% gain, by putting a properly tuned performance exhaust on it, adding some 4-port injectors and less restrictive air intake. In other words, you won't gain 22 HP. But with what I just mentioned you might gain 10-15, and it's all a direct bolt-on and straight-forward.

And further, even if you got 22 HP added, does it really matter in a vehicle that is geared the way a Cherokee is? I don't see it helping you off-road by much, and it will only come in handy on road if you're trying to burn rubber at the red lights and race it around at higher RPMs.

93XJLI

a fair amount of discussion about it here:

http://naxja.org/forum/showthread.php?t=1070907

by somebody who's running one.

XJNKY

Yeah, those are the sort of issues I was scratching my head about. What to do with all the sensors. The mechanics of it are fairly simple. Machining a plate and mating it to a modified intake would be easy (but require some welding $)

XJNKY

Two things:
First, I think you're grossly underestimating the effectiveness of southern ingenuity... it has turned out some of the best engineering we know of in the automotive world. NASCAR anyone? Ever heard of Roush Performance?

Second, THERE IS NO QUEST! If you don't want to be insulting, then do it by bothering to read the rest of the thread, specifically the parts like this: or this:I basically said "hey, saw this, thought it looked cool, discuss the issue", not "Hey guys, I'm on this epic quest to do something awesome, I'm determined to do it, don't try to stop me, I'm sitting here with the Sawzall in my hand chomping at the bit".

There's nothing more frustrating than logging 100 hours in the last 2 weeks running Finite Element Analysis on a million dollar project, only to come on the internet and have people assuming I'm under the hood of my Jeep with with a bottle of bud light, roll of duct tape, and a section of drain pipe going "Looky here Earle, I'mma build me an inteke!"

Your points are valid, but your presentation...

Parsnip

[QUOTE="XJNKY;2328
There's nothing more frustrating than logging 100 hours in the last 2 weeks running Finite Element Analysis on a million dollar project, only to come on the internet and have people assuming I'm under the hood of my Jeep with with a bottle of bud light, roll of duct tape, and a section of drain pipe going "Looky here Earle, I'mma build me an inteke!"

Your points are valid, but your presentation...[/QUOTE]


There's your problem...you hired Earle, not dale. We all know its not "hey Earle!" Its more like "DALE! DALE GRAB THE DAGGUM FIRR 'STINGUSHER!"
Now that's what I call mechanics