To boost it or not to boost a n/a 2.5?

[nitrohog]

The story goes that I have been looking for a new daily driver to replace my 180k mile 300m. I want something fun, mopar, and possibly turboed. So I have been looking at srt4 neons, some older turbo mopars, lx cars, etc. Anyway, I finally glanced in my garage at my beater 95 Dakota with the dodge (not amc) 2.5 and ax15 5 speed and thought, hmm, I wonder how much that bottom end would take... Lol. So I guess my question to you guys is what will a stock 60,000 mile bottom end take, what should I run for manifolds and turbo, and my biggest question is what is the best way to tune this tbi motor? I'm not looking to spend a ton of cash and I'd probably be happy with 6-8 psi until I decided to build a forged bottom end. But I'm used to building newer stuff with multi port injection and nitrous instead of boost. So I need some guidance from the people who know this era of mopars best.
Thanks for any and all replies!
Jerry

[turbo84voyager]

What you will need from a turbo engine is intake, injectors, fuel rail, exhaust manifold, turbo, distributor. You will need a turbo ecu, sensors and harness or add wires to your harness which might be easier due to the fact the engine compartment is different from the FWD. Depending on the fuel pump used, you might need a higher volume / pressure fuel pump. I am not sure how long a n/a engine will last with boost but with a low amount it should handle it ok. You might need to pull some timing due to the higher compression. The only problem I can see is I am not sure if the 95 trucks have a body computer and if it needs to communicate with the ECU. This might cause problems using a turbo ecu.

Honestly these engine are cheap to build. If you were to do this, you would be better off finding a cheap 2.5 turbo engine and rebuild using your block. A freshened up stock turbo engine will handle quite a but. The RWD has the bosses drilled and tapped for the motor mounts and does not have the balance shaft holes. Otherwise the FWD and RWD engines are the same, but because of this you would need to use your block

[tryingbe]

N/A engine have easily bend weak rod and easy broken pistons, don't do it.

[nitrohog]

Alright, thanks for the input so far. If I'm not mistaken the turbo intake manifold is drilled for multi port injection so all I'd have to add is the wires for the injectors? I don't think it has a body control module but I'm not 100% sure on that. I'm not having very much luck finding a turbo motor locally but I'll keep an eye out. I'm in northern Illinois if anyone has a lead on parts lol.

[bakes]

Do a wiring smec harness swap from a turbo car or van

[moparman76_69]

Alright, thanks for the input so far. If I'm not mistaken the turbo intake manifold is drilled for multi port injection so all I'd have to add is the wires for the injectors? I don't think it has a body control module but I'm not 100% sure on that. I'm not having very much luck finding a turbo motor locally but I'll keep an eye out. I'm in northern Illinois if anyone has a lead on parts lol.

All you need is the pistons and rods from a turbo 2.5, rebuild using your block. You won't be able to throw much power at the AX15 before you run into issues. That bellhousing will allow you to use the r154 toyota trans or possibly the MA5 from a colorado. The factory turbo manifolds will put the TB against the firewall and the turbo inlet facing the firewall also. It has been done with factory turbo/manifolds, but IMO its not ideal.

Do a wiring smec harness swap from a turbo car or van

This. Pull the engine management stuff from a van harness and graft it into a truck harness. Tedious but doable.

[nitrohog]

The trans is another reason why I'm planning on keeping the boost pretty low to start. But the Toyota trans sounds like a good option if the need arises. What other options do I have for manifolds? I only have a mig welder so I'd have to pay someone to modify it for me. I'll start looking for a turbo van harness and the associated diagrams/ pins. This should actually be the easy part for me since its more or less a part of my everyday job lol.

[moparman76_69]

The 89 minivan harness pinout is available online, I'll have to find the link. 89 is a SMEC, 90 would be a SBEC like the dakota. Shouldn't matter which you use. You may be able to use a car harness if you reuse the dakota bulkhead connector, it has the standard 50 pin with engine harness male connector. I was going to reuse the entire 89 mini harness since the headlight and marker light connectors are the same. I may actually still have the one I started to re pin laying around somewhere.

I modified a two piece to put the TB facing forward in the engine bay, and started to build a custom exhaust manifold with a standard t3 flange. I farmed out the welding part of it. I screwed up on the angle of the tubes and made it almost impossible to put the lower bolts in, and then gave up on the project and shelved it.

[nitrohog]

Found an engine from an 89 mini van, all accessories, turbo, fwd trans, harness, computer, etc for $400. It's 150 miles from me but I'm considering getting it anyway. Anything I should ask him to look at for me before I go check it out?

[Vigo]

I have turbo'd a TBI bottom end and had no problems at 16psi, and i have broken stock t2 pistons at 11-12psi, so if you are running lowish boost it comes down to other things besides part strength in the bottom end. You can probably even break forged pistons at 12 psi if things are far enough out of whack.

If you get all your ducks in a row theres no reason you cant run low boost on a TBI bottom end.

You won't be able to throw much power at the AX15 before you run into issues.

You may be thinking of the ax5. The ax15 is a fairly strong transmission that some people use behind turbo diesel and v8 swaps. Most people will say it can handle 300-400 lb ft. If his truck actually has an ax15 i would not consider it any kind of weak point for a low-boost 2.5 setup.

[nitrohog]

I do undoubtedly have the AX15 and 8 1/4" rear end, it also came behind the V6 and yes there are a few V8 swaps out there running it but it wont hold up to much more than a stock 318 if it isn't abused. Ive seen guys put 400HP+ through the little 8 1/4" rear end though LOL. You have me rethinking this whole thing again but for $400 I might still go pick that engine up since it has basically everything I need to make the swap that I may or may not be able to piece together from members on here. Im guessing that I should still run a wideband just to make sure that it doesn't go lean even with the stock tune?

[Vigo]

Yep, because a stock tune doesnt mean your fuel pump isnt failing, your pump strainer isnt clogged, your fuel pressure regulator isnt failing, one of your injectors isnt restricted, etc etc etc. There are plenty of 'normal' problems that will wreck a motor that dont have anything to do with its boost level, and a wideband is good insurance against something like that going unnoticed until it's too late.

[turbo84voyager]

If you get all your ducks in a row theres no reason you cant run low boost on a TBI bottom end.

I agree. The rods are the same lightweight rods that the 86+ T1 2.2 turbos had. Are they as strong as a T2, no but if the factory installed them in turbo engines, they should hold up fine in low boost and resonable rpm's.

[bfarroo]

When I did my 95 dakota I made a hybrid harness out of a 88 TII harness and the stock Dakota Harness. The dakota has the seperate fuse block which is much nicer than the fusable links on the 88. Took me about 2 hours to do the harness. Because the computer is on the passengers side rather than the drivers I had to cut and splice every wire to proper length, solder and heat shrink. I made the Mitsu turbo fit with some creative snaking of the plumbing but ultimately a turbo with the hot and cold on opposite sides would make lift much easier. I cut the stock elbow off and welded a plate on, knocked the freeze plug out of the other side and welded the intake flange on with a piece of tubing to extend it forward. I ran about 7 psi non intercooled. I swapped in a turbo motor with the dakota crank. Never had any problems with the trans at that power level. Used the truck as a DD on and off and as a tow vehicle for my other TM's using a tow dolly. The truck just got to rusty over the years and I junked it out a few years back.

[nitrohog]

I think I could live with 7 psi. And yeah this truck is a little rusty but fortunately I found some cheap rockers to throw on it and I'm not afraid of a little body work. Everything else is solid and its a great little beater truck but lacks about 40 horsepower to be a decent daily driver for me lol.