Dual VNT 4.0L I6 Engine

[ShelbySean]

Do you think a Dual VNT 4.0L Jeep Engine would be awsome? The engine has almost 200tq at a very low RPM. Imagine what a dual VNT system would do. I figure dual vnt because the vnt came on enginew with 2.2L displacement. 2.2 x 2 = 4.4. Either use a 4.2 or 4.0L Jeep I6. The electronics would be the tough part. I can weld, and machine stuff. What do you think?

[Koreth]

The only thing that comes to mind is the size of the VNT turbo. Wasn't the VNT turbo originally intended for a smaller engine? Like a 1.8 or something? I'm not saying it can't work, but I think the compressors might prove to be too small, especially if the Jeep 4.0 head is a better flowing one than the 2.2L head.

Don't get me wrong, it is an awesome idea, but I think the VNT turbos from the T-IV engine might be too small for the job.

[Ondonti]

I dont think the 4.0 makes so much power that you should be that worried about some sort of amazing head flow. I believe it doesnt rev as high either.

[7MGTE]

I think that it would work well. They don't rev any higher than 5000 RPM so I doubt you would have a problem with air flow. If you wanted some insane torque build a 4.6 stroker using the crank out of a 4.2L. That would be torquey!

[tkelly27]

I assume you want the torque down low for rock crawling? Do you have 2 VNT's just laying around? If so, use them, otherwise you might try the mitsubishi turbos. They are dirt cheap and will spool up fairly quickly.

[DKKNE]

I would think two mitsu turbos woudl work too! I am all for that project. The header would be complex due to having to place two tubos ont he same manifold. Thats alot of weight on the manifold, so I woudl worry abotu turbo placement and also how to brace the manifold for the extra weight.

[GLHNSLHT2]

I'd run dual headers, 3 into 1's like Mercedes use. And I'd use two stock TurboDodge garrett's over the VNT's or Mitsu. It'd flow a bunch better. You've got all the low down torque you should need.

[Ondonti]

I think the vnt would be a better choice. With a rev limite of 5000 rpms you just dont need that much flow. People here make near 200whp on ONE mitsu. THe 4.0 doesnt make 200whp, and two vnt's would be perfect for rock crawling.

I dont think T1's would spool until your rpm's started getting to high to have any fun crawling.

[ShelbySean]

I didn't have any intention of using this idea for rock crawling. I just thought that it would be a cool idea to put that type of engine in a light (or even a heavy car) car, and make a fun muscle car. Put it in a 2 door Jeep Cherokee Classic. Get rid of the 4wd, and make it a solid live axel in the rear. Drop it down lower to give it a more car like look and feeling, ditch the rear seats. Maybe even cut the top and make a new roof with a fast back or trunk. I just think the Jeep Cherokee Classic front end would be a gorgeous front end for a muscle car. Almost Cuda' like. I'm a welder, so its not out my realm of possibility. Just picture it.

I have an 87 Shelby Charger, and I need to put a new floor in it. I figure, if I'm going to do that, why not put a trans. tunnel in it, and make it rwd? I think an inline 6 would fit a lot easier than a small v8.
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http://www.jeep4.0performance.4mg.com/

4.0 Engine Power Ratings

The Jeep 4.0 litre I6 engine is a pushrod overhead valve design with 2-valves/cylinder. The factory power ratings are as follows:

'87-'90 XJ: 177hp at 4500rpm, 224lbft at 2400rpm, redline 5000rpm
'91-'95 XJ: 190hp at 4750rpm, 225lbft at 3950rpm, redline 5250rpm
'96-'99 XJ: 190hp at 4600rpm, 225lbft at 3000rpm, redline 5300rpm
'00-'01 XJ: 193hp at 4600rpm, 231lbft at 3000rpm, redline 5300rpm

'91-'95 YJ: 180hp @ 4750rpm, 220lbft @ 3950rpm, redline 5250rpm
'96-'99 TJ: 181hp @ 4600rpm, 222lbft @ 2800rpm, redline 5300rpm
'00-'03 TJ: 190hp @ 4600rpm, 235lbft @ 3200rpm, redline 5300rpm

'93-'95 ZJ: 190hp @ 4750rpm, 225lbft @ 3950rpm, redline 5250rpm
'96-'98 ZJ: 185hp @ 4600rpm, 220lbft @ 2400rpm, redline 5300rpm
'99-'03 WJ: 195hp @ 4600rpm, 230lbft @ 3000rpm, redline 5300rpm

To see the Power Curve Graph
http://www.wjjeeps.com/misc/curve_40.jpg

Over 200+trq from 1,200 to 4,600 RPM's!!!
Imagine with Dual VNT's!!!!! INSANE!!!!
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[afsautoworx]

Id just use one big turbo....youve got torque to spare.

[Ondonti]

If you want big power, twin 16g's would be fun, or for a single, maybe a t04b 62-1 or a Garret T61 or even a GT3582 (gt35R) or a gt3782

[jdawg]

the newer 4.0's like the last couple years they were made had a 2 peice exh manifold cause of the cracking issue. They are the front 3 cyl's and the rear 3 cyl's. May help a little

[ShelbySean]

I need some flow numbers for the 4.0L and the heads on the vnts at all RPM ranges. Then I can cross refrence them to see if doing a Dual VNT would take full of advantage of its streghts vs. using a single large turbo/dual small regular turbo's.

Koreth - "The only thing that comes to mind is the size of the VNT turbo. Wasn't the VNT turbo originally intended for a smaller engine? Like a 1.8 or something?"

Fine. 1.8 x 2 = 3.6 vs. 2.2 x 2 = 4.4. I think at least the turbo's can hadle the flow on the 4.0L if the vnt was used on the 2.2L, and was able to take it.

[Ondonti]

as far as flow goes, they should be fine for most purposes. They wont be perfect but the 4.0 definitly flows a LOT less air then a twin 2.2's.

[LebaRoman]

I was thinking of this project for a while but ended up dropping it.

The 4.0L is not a good engine. The intake runners are all different length. The intake and exhaust manifolds are on the same side, so the 2 turbos will be constantly heating up your intake manifold. The intake and exhaust ports are angular (crosssection view) and don't flow well, not to mention the ancient inline arrangement of all the valves. Plus it's a pushrod, so it wont rev!

Turbos are good for high rpm, if you want low down torque use a supercharger. If you think you can use the small VNTs for a low revving engine and torque, all you'll get is wheel spin in 1st 2nd and 3rd past 3000 RPM.

Then there is the fitment issue. An inline 6 is much harder to fit into a "longitudionaly challenged" compartment of a FWD car. Just think what's longer 6 cylinders or 4? So the small V8 would fit easyer.

Then there is the weight! The 4.0L is a big block of cast iron, and you want to add 2 turbos, maybe an intercooler also? And all that will be sitting infront of the front wheels! Just imagine the weight distribution! The car won't even be suited for drag racing, and I don't even have to mention the understeer.

Next - drivetrain! The jeep 5 and 6 speeds were not made to handle major hp and tq which you are probably seeking with those 2 turbos. Between the steel driveshaft and the solid axle, the tranny will probably be the first thing to die.

And the biggest issue. VNT SUCKS! Too many vacuum lines, too many solenoids, too much sensor input and computer processing. Get 2 T3s.


My suggestion. Use the 3.5L V6. It's all aluminum and it will fit alot easyer and can be pushed back furter. 24 valves are better than 12. It revs much higher, 225 HP stock vs 190. It uses the same transmission as the HEMIs so it wont fail. Don't like automatic - the HEMI guys have made some T5 swaps with the dakota bell housing I believe. Don't quote me on that, I researched the subject a long time ago, before I had to research fault codes and vacuum line diagrams. The biggest issue would be decompressing the engine, 9.9:1 - not turbo friendly. And you'll have to weld some custum fuel rails, the stock ones can't even handle the pressure of the NA engine, but welding doesn't seem to be a problem for you.

Oh and a SOHC 90 degree V6 souds very close to a V8, if you're going for the whole muscle car feel.