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post #1 of (permalink) Old 05-27-2002, 03:02 PM Thread Starter
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turbo in a 258... crazy?

ok, i asked this on the amc bbs and got one reply. so here i am sitting around because its raining like mad and i dont have a garage and dont want to get struck by lightning, suppose i could clean the house or something, but why when i can think about more junk to do to my jeep.

so anyway i'm thinking how practical would a turbo be on my 258?

how easily could i put it on?

could i use headers with it?

would i want headers with it?

how much boost should i go with?

what would the risk of the turbo housing cracking in the water when wheeling (due to high temp and cold water)?

what should i get the turbo from?

ok, so maybe its a dumb idea, but if it's feasible it may be worth a try right? if i never made any mistakes i wouldnt know anything. there is a guy i found who has a turbo from a ford (XR4TI) with about 6lbs boost on a 258 in an old gremlin so it can be done, but can it be done to a jeep, and is it worth it ??????

ok, i need a beer
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post #2 of (permalink) Old 05-27-2002, 03:07 PM
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Re: turbo in a 258... crazy?

258 not a good motor for a turbo. They don't rev fast and high enough to make it worth while.
post #3 of (permalink) Old 05-27-2002, 03:08 PM
 
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post #4 of (permalink) Old 05-27-2002, 03:31 PM
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Re: turbo in a 258... crazy?

Since you're asking for opinions, Here's mine:

Not a good idea. A good turbo installation is no easy task, or cheap. Look at the differences between a factory turbo engine and its non-turbo version; usually the camshaft and everything above the connecting rods, and often them and the crank too.

That's because a supercharged engine needs a lower compression ratio, bigger intake and exhaust system, and stronger everything else. I don't think it's a good idea unless you have a really good kit.

My guess is that you could swap in a bigger engine cheaper than a really good turbo kit, and have an engine that's just as strong and more reliable.

Turbos become attractive where there are weight or size limitations in the vehicle, or some outside factor like tax rates or competition formulas. Or because a manufacturer doesn't have a bigger engine but needs more power.

I'm not against turbos - I have two Volvo 7-series turbos and love them - but I think a nice healthy Chevy small block would be more fun.

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post #5 of (permalink) Old 05-27-2002, 06:04 PM Thread Starter
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Re: turbo in a 258... crazy?

another dream quashed :-)

time for another beer...

seriously though thanks as usual guys
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post #6 of (permalink) Old 05-27-2002, 09:02 PM
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Re: turbo in a 258... crazy?

can be done a blow thru would be the way to go or a blow thru MPI Seeems to me a company by the name of Bear was making turbo kits for the AMC/Jeep 232 and 258s.
You might check out Turboforce.com
They have a few Am inline turbo pages. If you want it bad enough you could do it. look at the Ford turbo 2.3s Or even most diesles that are out there today. they dont rev fast at ALL. they use turbos.
and by the way 258s are pretty soft on compression anyways so....

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post #7 of (permalink) Old 05-27-2002, 10:50 PM
 
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Re: turbo in a 258... crazy?

New guy, so I'll take it easy on him....

*so anyway i'm thinking how practical would a turbo be on my 258?*

Inline 6 cylinder engines are a pain in the a$$ to turbo. Too long of an exhaust plenum to keep a decent mean pressure up for the turbo exhaust turbine.
-----------------

*how easily could i put it on?8

It's a pain in the a$$ if you are going to build it yourself, and the kits cost plenty of $$$.
------------------

*could i use headers with it?*

NO. All exhaust is collected into one manifold to feed the turbo. Most of the time you won't even have to run a muffler afterwards.
------------------

*would i want headers with it?*

Repeated, Redundant questions...
Ok, now I'm getting the hammer out....
-----------------

*how much boost should i go with?*

It's not too likely you are ever going to have to worry about that problem...
With extra long collection plenums for exhaust gasses, and the small bore/ long stroke and odd firing order of the I-6 engine, you probably aren't going to make much boost in the first place.

A split pulse exhaust arrangement will probably do the best for an I-6.
If you can manage it, don't go over about 6 PSIG with stock rods, pistons and crankshaft.
-----------------

*what would the risk of the turbo housing cracking in the water when wheeling (due to high temp and cold water)?*

Use a heat blanket and a splash shield and unless you submerge the exhaust housing you shouldn't have a problem.
----------------

*what should i get the turbo from?*

*WHAT* shoud I get the turbo from?*

You mean WHERE should I get the turbo from....
Unless you buy a kit (Highly recommended for beginners!) Garrett AirResearch makes the most tunable turbo charger. (The TO4-B).
Every thing can be changed, impeller, turbine, compressor housing, exhaust housing, even center bearing sections...
Good for guys screwing up a lot so the don't have to replace the entire turbo every time...
----------------

*ok, so maybe its a dumb idea, but if it's feasible it may be worth a try right? if i never made any mistakes i wouldnt know anything. there is a guy i found who has a turbo from a ford (XR4TI) with about 6lbs boost on a 258 in an old gremlin so it can be done, but can it be done to a jeep, and is it worth it ??????*

That particular turbo came off a '79 pace car mustang with 4 cylinder engine.
I'm surprised it can pass enough to keep the 258 fed...
---------------

*ok, i need a beer*

While you are having that beer...
Think about these questions,....

Carb, blow through or draw through?

Draw through means no real heavy modification to the carb, but the compressor will be 'Wet' (fuel in the intake tract) Any backfire or ignition source in the intake and the intake will depart the vehicle in a most spectacular way.
Draw through is also going to give you the most 'turbo lag', meaning the engine is going to be very sluggish until the boost reaches the cylinders...

Blow through,
Blow through means you make the boost, then blow it through the carb, which usually stays mounted to the intake manifold.
This cuts out a little turbo lag (back to this in a moment), and removes fuel from all but the normal intake tract, but you have to spend some time modifying the carb....

Bonnet or Box?
Bonnet means you connect the boost pressure to the top of the carb like an air cleaner.
Makes for a clean installation, but you really have to do a lot of work to the carb! That boost pressure wants out REAL BAD, and it will find a way out if you don't do the carb up in a big way...

Box means you put the entire carb down in a 'Boost Box'. Very little modification has to be done to the carb this way, but you have to consider the fuel system closely when you use a box. That boost pressure will find a way out down through the fuel line, pushing the fuel down and leaning out the engine as it departs...

Turbo Lag...
You will have to find a way to decrease boost pressure when you are at high RPM, let off the throttle a second, then get back into it...
When you have boost pressure built, and you let off the throttle blades, that pressure has to do something, so normally it backs up at super sonic speeds and takes the blades off the compressor impeller.

At the very least, it's going to back up, slow down the impeller (back pressure), and when you open the throttle blades you will have to wait for the pressure to come back up before you make any power...
AND,
With the back pressure up, your waste gate will open bleeding off your exhaust pressure, and you will REALLY be screwed for power...

You will have to find a way to,
1. Keep that boost pressure from backing up and slowing down the compressor and opening the waste gate...
OR,
2. Own stock in the company you get turbo and engine parts from...

Now, to the engine....
The 258,
1. Cast iron connecting rods. These make nice shrapnel when you over boost or make too much horsepower.
2. Cheap connecting rod bolts. See the 'Shrapnel' comment above...
3. 2 bolt Iron main caps. You will be surprised how fast these will scrap bearings and cranks!
4. Cheap Main cap bolts. See 'Shrapnel' comment above... you can literally drive over parts of the crankshaft when the main bolts fail...
5. Cast Iron Crankshaft. See 'Shrapnel' comment above.
6. Emissions camshaft loves overlap, turbos hate overlap.
7. Factory cast pistons tend to wind up in the oil pan.
8. With the exhaust restricted by the turbo, and add boost, you had better use high temp exhaust valves....
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post #8 of (permalink) Old 05-28-2002, 01:54 PM Thread Starter
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Re: turbo in a 258... crazy?

thank you for being gentle TR. i was actually thinking blow through, bonnet, but again it was just a nutty idea that came upon me while suffering from lack of sleep and time off. think im gonna stick with my nice naturally aspirated 258, maybe try the 4.0 head on this one, we'll see :-) thanks again guys.

man, where was this board for my first two cj's, i coulda saved a ton of time and money replacing worthless junk.
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post #9 of (permalink) Old 05-28-2002, 02:10 PM
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Re: turbo in a 258... crazy?

And, just for the record, turbos and not impractical on low-speed engines. Lots of low-speed Diesels are turbo-charged.

Turbos, by their nature, do tend to narrow the power band. High-speed turbo engines tend to be weaker than their naturally aspirated counterparts until the turbine gets up to speed, and low-speed turbo engines run out of air when they wind up.

But getting the turbine to produce its boost at low engine speed just requires designing it for that purpose.
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