TURBO CHEROKEE

[collin430]

I'm starting to gather all the parts I need to boost my XJ! The only think I'm not sure on is what size injectors to get for the extra fuel I'll need? Some say 30lb injectors is to much some say it's okay. Just looking for your opinions. My jeep is not a stroker but does have a mild cam in it. Thanks for the help!

[jeepxj3]

Stock 22 pounders are good for 190hp
30 pounders are good for about 260hp
36 pounders are good for about 315hp

I guess it depends on how much boost you plan to run and how much power you want to make.
What is your plan for tuning?

[collin430]

Stock 22 pounders are good for 190hp
30 pounders are good for about 260hp
36 pounders are good for about 315hp

I guess it depends on how much boost you plan to run and how much power you want to make.
What is your plan for tuning?

I was talking to a friend who builds racing engines and he said if I run low boost ( around 7-8psi) that i shouldn't really need to tune the computer should compensate but I'm not sure yet, if I need to tune timing ill get an MSD 6AL box, if I need to tune fuel I'm thinking an adjustable fuel regulator. Still a work in progress

[SkylinesSuck]

So many people have no idea how forced induction works. It's not how many psi. It's how many cfm the turbo flows at different boost levels. That might sound academic, but 8psi from one turbo could mean 200hp and 500hp from a different turbo. You design your build around that, not how many psi you plan to push from an unknown turbo.


And your friend who builds race engines is clueless. Run, don't walk from his advice. Also, you won't be able to tune the way you described. You need to spend some time poking around the boards to see what other people have built and how before you even consider this project.

[collin430]

So many people have no idea how forced induction works. It's not how many psi. It's how many cfm the turbo flows at different boost levels. That might sound academic, but 8psi from one turbo could mean 200hp and 500hp from a different turbo. You design your build around that, not how many psi you plan to push from an unknown turbo.


And your friend who builds race engines is clueless. Run, don't walk from his advice. Also, you won't be able to tune the way you described. You need to spend some time poking around the boards to see what other people have built and how before you even consider this project.

Okay cool thanks, I'll look into the cfm then. And I've looked around a little but not many people are giving much information on how to tune an obd 1 vehicle. All I've seen is spicing into the exam with a msd. Thanks for the replies guys I really appreciate it!

[jsawduste]

For all intents and purposes you really can't tune a SBEC/OBD1 vehicle.

[collin430]

For all intents and purposes you really can't tune a SBEC/OBD1 vehicle.

I know that's why I'm trying to find other ways to do it.

[jsawduste]

Convert it to JTEC/OBD2.
Simple swap.

[collin430]

Convert it to JTEC/OBD2.
Simple swap.

How simple is it what all do I need? New wiring harness?

[collin430]

If I did the math correct my cfm is 821

[SkylinesSuck]

I was referring to the cfm of different turbos you might install.

And I'm no help in the tuning of OBD1, sorry. One thing I can tell you is your friend might be thinking a small turbo at low boost on a MAF'd car *might* not blow itself up. MAP is completely different. Many MANY older cars are MAP. That's why I was saying you should wholesale disregard whatever he says. What race engines does he build?

[collin430]

he races in drags, ive only seen 2 of the engines hes built, a 357 and a 454 big block bored out to something i cant remember. for the obd 1 problem if i were to get an Apexi safc2 and spliced it into the main harness you think it could possibly work?

[SkylinesSuck]

I think you could use one to tune OBD1, but they would be woefully inadequate to tune a boosted application.

[SkylinesSuck]

An SAFC just intercepts the signal from the MAP sensor to the ECU and lies about what kind of vacuum (or lack there of) the engine is seeing. The ECU combines this info with a number of other things including air temp and predetermined tables in the ECU to say how much fuel and timing the motor gets. Problem is the stock MAP sensor is only capable of seeing vacuum or "0" which is WOT on an n/a vehicle. Any turbocharger/supercharger works by creating "boost" which would mean a number higher than 0 which your sensor just can't read. People with OBD2 have the option of running a 2 bar+ MAP sensor and reflashing the ECU to interpret it correctly, but nobody reflashes OBD1 that any if us know of.

If you are serious about doing this, I'd look into some type of piggyback ECU with an extra injector and figure out a way to control timing. One of the OBD1 experts will have to chime in on that part.

[jeepxj3]

I think that the Split Secont FTC1 or the AEM FIC would do it. They both can control bigger injectors or extra injector and timing.