I'm considering putting a turbo on my WJ grand Cherokee, 4.7l v8. I can have the pipework done fairly cheap, I have the oil system organised etc, my only concern is, aftermarket tuning is quite expensive. These cars don't have enough aftermarket support.

If I have a stock ecu, and I plan to run 7psi, what kind of problems could I run into? and are there ways around aftermarket tuning? Eg, retarding timing etc.

I don't want a powerhouse, I don't want more than 7psi, I just want a bit more mid range power.
I also just thought I'd add that the stock compression ratio is apparently 9.5:1 which may be too high to begin with.

tech savvy replies only please, I'd prefer not to hear opinions from people who don't have experience with this

 

9.5:1 at 7 PSI isn't a big deal. That said, once you've gotten 7 and its all worked out the itch to have more will come, building in a little overhead couldn't hurt. You will probably need to run premium fuel all the time. At what altitude do you live?

As far as tuning, there is no way around it... you will have to do something, and it tends to be either a lot of time or a lot of money. I can't speak to specifics about your particular platform but I am sure megasquirt is an option, maybe start looking there. People on this forum build all type of obscure things, its doable.

 

What year Grand Cherokee? You should upgrade injectors and fuel pump I don’t think the stock setup will support the aprox 118 extra hp . You don’t want to lean out that 4.7 . You’d be fine with 9.5 cr with good fuel. As for tuning there is minimal options but there are a few people on here that added a turbo to a
4.7 IIRC Duner has done it.

 

I'm in the middle of the same thing. https://www.theturboforums.com/threads/turbo-4-7-jeep-vs-4-8-chevy.383227/#post-2019335

I'm putting a trigger wheel on the 4.7 and Megasquirting fuel and spark, in a piggyback fashion. I also got some Hellcat injectors thanks to the fuel line recall. You have to use bungs to make up the difference in length but no big deal.

The hot side was easy, I stuck it under the floor next to the transfer case, but getting a charge pipe up to the engine is challenging. I'm going to have to go straight up against the floor, and along the back of the t-case and transmission with 2 1/4" pipe. Might use 2" to save me some headache, as that will flow more than enough for a 4.7l

 

2003. I was thinking that the stock stuff may lean out at high rpm, but I don't take it over 5000rpm anyway. Will a better fuel pump and set of injectors flow better, if there's no tune?

 

The way to do it would be to install the fuel pump like a Walbro 255 which should cover you til 500hp and it’s not expensive and put the injectors and tune in at the same time. Megasquirt may be your best bet. If they make blowers for your 4.7 Jeep they have to be tuned it might be another good option to see what they are tuned with.

 

I'd honestly be looking to avoid a tune, as the only aftermarket ecu stuff I've found is more than I paid for the whole car. If the car can't utilise 7psi as it is, I'd rather take the boost down to a point that the current stuff can make use of. Even if its 4psi for example.

 

There's really no good way without a tune. You may get away with a couple psi with good fuel, but hardy seems worthwhile. Maybe a small wet shot?

 

Isn't that for a very short term use?
The turbo and fitting is around $400aud, if I can utilise 4psi without a tune and only gain maybe 30hp for example, it's still cheaper than any other mod I could get for that price. That's the only reason I'm taking this path.

 

The turbo itself is a tiny amount of the entire cost. There is a lot more $ in the support systems that allow it all to live together. You can't throw a turbo on a modern vehicle with no tuning or fuel and expect anything but a catastrophe.

You must provide fuel for the additional incoming air.

 

Nothing says you can get away with 4 psi. Many of the 4.7's are a crap shoot in na form.

 

You kinda can. It has been proved time and time again, but it depends on the vehicle. I'm happy to upgrade the fuel system if needed, bu

and do you think an upgraded fuel pump and bigger injectors will be enough to utilise any of the boost, without a tune? The cost of an aftermarket ecu is quite high, and a tune is almost equally as high. There is no support for these where I live. So if the choice is between pump/injectors and dropping boost, or paying a total of 3-4k to have 7-10psi, I would rather the first option, as I'm not looking for a stupid power increase.

 

Anytime you go larger on the injector you need a tune.

 

And what about a 3rd party tuner that can trick the ecu? rather than purchasing an aftermarket, tuneable ecu?

 

That's a reasonable way to go, there are some decent mail order tuners around.

 

I think Duner was using an FMU. I'll have to go back and re read.

Megasquirt ECU's aren't that expensive and offer a lot of options. ($400-ish range)

AEM offers the F/IC-8, which is a true piggyback ECU, it goes in between your PCM and the engine. It allows control under boost, and spoofs signals so the PCM doesn't turn on the check engine light. ($400-ish)

If you watch ebay Hellcat injectors (600cc) are going for $200-$300 for a set of 8.