I was thinking that it wouldn't be worth it to change my 4.2L head to 4.0L because then I'd need a 4.0L header and exaust work and crap. I figured the money would be better speant on a v8. I'm planning to at least get a EFI system from a 4.0L for the better driveablitly and to eliminate the stalling the BBD does on hills. Now I just though, since I have an iron manifold, why don't I try to put a turbo on then (like from those 2.2L dodges?) I see them in the junkyard. Good idea? It should go good with the EFI, yes no? I just did my smog last month so I don't have to worry about it for 2 years.

I have a new turbo from a GM 3.8 I keep thinking hmm..... I wonder..... ??????


Then I remember....


Oh yah I have 360's and 401's never mind....



:flipoff2:

Bad idea for two reasons:

1. The only gain you'd get from a turbo would come at high RPMs. (Worthless for a Jeep unless you mud it.)

2. The turbos they put in thos Mopar 2.2s (Charger, Laser XE, etc.) almost universally shit the bed after about 60 or 70 thousand miles.

HTH,
Jake

Originally posted by Jakesteramalamajama
Bad idea for two reasons:

1. The only gain you'd get from a turbo would come at high RPMs. (Worthless for a Jeep unless you mud it.)

Jake

that is part of the question... a couple of drunks last night sitting at the bar started thinkin about JYD Turbo's and how they could be made to work for rockcrawlin... this is the basic question/possible solution we came up with...

4.0L motor that you want all your HP & Torque at 1500RPM

2.0L Eclipse Turbo (motor 1/2 the size)

put the eclipse turbo on the 4.0L the turbo will see twice as much airflow in the 4.0 thus making all its power at 1/2 the RPM as it does in the eclipse... now this does not help you at all at higher RPM so then our discussion got deeper what about 2 2.0L turbo's in parallel plumbed so you could close one off when rockcrawlin and open up both of them when "ROCKRACING"

Did we have toooo many beers last night or might this work ???

I'm a little blurry on the topic of turbos, but I think that the impeller on the turbo works very similar to a torque ocnverter. actual hook-up depends on velocity of gas past the impeller to overcome the stall. either way, I don't thing the 4.0L car rev fast enough to get good gains from a mitsu turbo. maybe a turbo meant for a diesel would work better, but they flow gobs more than a gas engine.

either way, there's a few sources for AMC turbos.
Turbo city used to make a kit, I dont' know if they still do.
and there's some freak out there who twin turbos amc 360's that supposedly will make a CJ do wheel stands.

Too many :beer:s :D

I don't think this is a true statement:

Originally posted by redruM
the turbo will see twice as much airflow in the 4.0 thus making all its power at 1/2 the RPM as it does in the eclipse

In terms of little car turbochargers, airflow isn't really the enemy, it's inertia. A smaller, lighter turbine spins up faster than a larger heavier one because of inertia. A larger turbine moves more air. This is why you see a lot of Hi-Po sports cars with twin turbos. One is the little "low speed" turbo that spins up to speed really fast to prevent turbo lag and the other is the big turbo that lags far behind the engine but pumps a ton of air into it once the engine is screaming.

That said, what you REALLY need is a BIG turbo off a diesel that's designed to move more air without spinning so fast, thereby mitigating much of the lag problem. The veins on the turbines are differently shaped so that they optimize airflow at a lower speed and so don't need to be 'spun up' as much.

If you get too big though, a 4.2 wouldn't move enough air to spin up the exhaust turbo enought to get the intake compression turbo to operate efficiently. If I had to guess at what might work well with a 4.2, I'd say try using a turbo system off one of those 4-cylinder Isuzu diesels that come in the NPR and GM's little cab-over box truck (basically a re-badged Isuzu). You'd also almost certainly need an air-to-air intercooler on there. A 4.2 is one hot-running engine (every 4.2 I ever saw ran around 210-215) and all that heat would sap your power unless you cool that air back down before it hits your intake.

I worked my way through college as Diesel Technician for Ryder Truck. ;)

Jake

There's a book called Turbochargers by Hugh MacInnes you should read. It's been a while since I read it, but if I recall correctly the compressor needs to be matched to the engine. You should try to find a turbo that was designed for a similar sized engine. A Buick 3.8L turbo would be better than a 2.0L turbo. Once the compressor is matched, you adjust when it kicks in by changing the turbine housing. The tradeoff here is if you use a small turbine to get boost at lower RPMs, then it will restrict the exhaust at higher RPMs.

Very odd that this subject came up....

I am glad it did though, I just bought a Garret T-25 turbo from an eclipse.

The eclipse had a 2.0L 4banger and I have a 2.5L, the eclipse revs to 7 grand and I go to 5.

This might get interesting but I only have $160 in an almost brand new turbo.

Keep any info coming, Gramdpa expect a PM/email from me. ;)

Those DOHC 4 bangers get more HP with and without their turbo than a 4.2L. Why wouldn't it be a good idea. :confused:

Originally posted by Taso Stambolis
Those DOHC 4 bangers get more HP with and without their turbo than a 4.2L. Why wouldn't it be a good idea. :confused:

All I was trying to say is that you can't just slap any old turbo on any engine and expect it to work perfectly. (There's an outside chance that it will work, but the odds are against it.)

Like Grandpa Jeep said, the Turbo has to be sized for the application. If you put on a turbo for a smaller application than the one at hand it's more likely it inhibit airflow than improve it. You may be forgetting that there are two aspects to a turbocharger and that any benefit gained on the intake side in the form of CFM down the intake can easily be rendered impotent by the drag of trying to force all the air flowing out of your big old 4.2 past that little exhaust-side turbine.

By all means, if you have the time and inclination to do so, slap a 2.2 turbo on your 4.2 and post the results. Prove me wrong! I won't mind. We'll all learn something. I'm just trying to say that, more likely than not, it won't work worth a shit.

Good luck,
Jake

There have been several discussions on turbos in the 4.2 over on the amc board:
http://pub8.ezboard.com/bamcforum

I seriously looked into it as well after a few too many one night and realized that it would be way more trouble than it's worth. The biggest pains in the ass in trying to fit a turbo would start with the plumbing, then figuring out how to run the intake, if injected its obviously easier, but if you are running fi you are going to have computer problems unless you get a new chip burned, if you are carb'ed you have to either go box or bonnet and worry about sealing that and not blowing up your carb. then there is the problems of heat dissipation, maybe an intercooler, proper lubrication, and where to put all of this. think there was some talk on ORC SWB about this as well. it was a cool idea and i'd love to see someone do it, but imo it aint worth it for the minute gains you'd get.

-web
:grinpimp:

Originally posted by webjeep
There have been several discussions on turbos in the 4.2 over on the amc board:
http://pub8.ezboard.com/bamcforum

I seriously looked into it as well after a few too many one night and realized that it would be way more trouble than it's worth. The biggest pains in the ass in trying to fit a turbo would start with the plumbing, then figuring out how to run the intake, if injected its obviously easier, but if you are running fi you are going to have computer problems unless you get a new chip burned, if you are carb'ed you have to either go box or bonnet and worry about sealing that and not blowing up your carb. then there is the problems of heat dissipation, maybe an intercooler, proper lubrication, and where to put all of this. think there was some talk on ORC SWB about this as well. it was a cool idea and i'd love to see someone do it, but imo it aint worth it for the minute gains you'd get.

-web
:grinpimp:
well even if you get a couple PSI one of the huge benefits will be that altitude won't affect your engine. It will still make the same HP. So you don't even need to get crazy to have a good reason to do it. If I did it it woudl be after doing EFI. I figured I could make a exaust manifold to turbo adapter at work(machine shop).

After having lots of turbo experience and little offroading experience (relatively speaking) I'm against use of any turbo setups in slow offroading usage.

I'll get to the turbo size thing in a second... but as far as why I'm against 'em...

You will create heat everywhere. Incoming air charge, coolant temps, exhaust, everything. Melting wires and such is a constant concern. Crawling & idling for hours gives you no airflow, so you better have some nasty fans. I'm not sure, but I believe all the Jeep I6's have intake & exhaust ports on the same side... now you are creating a ton of heat right under your intake too. Intercooled? Better have fans on those too. Run the air too hot, or the coolant too hot, you'll detonate and destroy the motor in no time. I've done a lot of turbo tuning. Have a turbo setup that isn't tuned well.. and you'll bitch about it constantly... I've seen all aspects - poor drivability, poor mileage, poor throttle response, detonating due to too much timing, high EGT's from too little timing. You can screw these up on any engine, but on the engine that isn't turbocharged OEM, you'll be starting from scratch and you better make sure you follow through.

As far as turbo sizing, you will have to size it for the application and engine. The exhaust pressure created before the turbine housing (and in the housing) will govern the spool up & response of a turbo. If you have a larger turbo, it will take longer to generate that pressure, and longer spool up time. If you have a very small turbo, you will have a very responsive turbo, but if you spin it to higher RPM, you will generate too much pressure in the turbine housing, causing the turbo to overspin, which can cause turbo damage, overboosting which can cause engine damage. So turbo sizing is crucial, but you can find something that will fit your application. Boost wouldn't be instant, but would be responsive. My guess is that it would annoy the hell out of most crawlers, as the boost response could come up fairly quickly in such an application. Imagine having 100-200lb-ft increase in torque with a slight tap of the throttle... wheelspin, tip your rig... you can see the implications.

I dunno, just seems like a nightmare waiting to happen, when you can get a decent HP V8 that's very reliable, streetable, and with great mileage for cheap.

that was way too long, sorry for rambling...
hope it helps someone..

I don't plan to ever use the turbo on the trail, it will be for street/highway use only.

I don't see how I could possibly get a street legal V8 in my TJ cheaper and if I did I wouldn't be able to knock it back to 4Banger power when I hit the rocks to keep breakage to a minimum.

hmm, you got some great points on the slow nature of 4wheeling. Maybe an eaton supercharger from a Ford Thunderbird SC or GM 3.8L would be better. They're on ebay a lot.

I see problems with keeping a cylinder head in place on a 4.2L.
With the extra manifold pressure, cylinder pressures during combustion will be much higher. 4.2L head bolts are not that strong or numerous. I think the left front head bolt would be the first to give you problems, since it threads into a proven weak point in the block.

No doubt about it Robert you can't run normal boost levels on an engine that wasn't designed for it. More reasons then just that too.

Got to have a custom wastegate, I have not been able to find one that opens at less then 5 psi which is what I am currently looking at as max boost.

You could opt for 0 boost/ vacuum I guess, anyone have anything to say about that? It should still provide a respectable increase in power at the top end.