GM 3.8 Supercharger on a 4.0

[89 MJ]

Has anyone on here heard of this? Reading a build thread on a certain orange MJ in Guam (you know who you are) has me contemplating looking into supercharging a 4.0. People of Facebook apparently use GM 3.8 superchargers, but I'm not sure how. I did a little bit of reading, but didn't really get anywhere. I'm not sure if I will do this or not, it will depend on how the truck drives with the new motor, but I just wanted to through this out there now to see if any of you know anything about it.

[derf]

It's possible.  But you'll probably have to fabricate a lot of stuff like the intake and become a whiz at tuning.

[scguy]

From what I've seen, 3800 superchargers are either mounted on top of the intake with an adaptor (which can require you to cut the hood), or side mounted, with a custom intake. 

https://www.boostedtech.com/superchargers/jeep-cherokee/cherokee-4-0-liter-6-cylinder-side-mount-supercharger/

 

You need to rig a new belt setup, fuel management, etc 

 

The other option is an M90 from a Ford 3.8 SC, but it mounts in place of the AC compressor, which I'm not willing to part with. 

 

 

[89 MJ]

11 minutes ago, scguy said:

From what I've seen, 3800 superchargers are either mounted on top of the intake with an adaptor (which can require you to cut the hood), or side mounted, with a custom intake. 

https://www.boostedtech.com/superchargers/jeep-cherokee/cherokee-4-0-liter-6-cylinder-side-mount-supercharger/

 

You need to rig a new belt setup, fuel management, etc 

 

The other option is an M90 from a Ford 3.8 SC, but it mounts in place of the AC compressor, which I'm not willing to part with. 

 

 

I had seen that, but I am hesitant to spend $4,000 on a supercharger. The belt doesn't really worry me, but figuring out the fuel does. I didn't know that about the Ford supercharger. I don't use the AC, so I might look into that. But I would still be hesitant to get rid of the AC because I want to move south sometime.

 

14 minutes ago, derf said:

It's possible.  But you'll probably have to fabricate a lot of stuff like the intake and become a whiz at tuning.

The tuning is my main concern, I don't know how someone would go about that with a Renix system.

[mnkyboy]

The Ford M90 would be the easiest but I don't think either would be all that difficult, there's a guy in the boosted 4.0l group on FB that sells the bracket for the Ford M90 separately or he will sell you a complete set up minus tuning for around $800.

 

I know another guy that was selling the GM adapter but not sure if he still is offering them or not, either way it wouldn't be too difficult to make.

 

There's a few options for tuning, for low boost you could get away with old school methods such as an FMU along with bigger injectors, another option is a piggy back such as Split second, then there's a number of full stand alone ECMs you could convert to which would be best but also the most work.

 

No matter how you tune, you will want to make sure you have a wideband set up so you can monitor AFR along with all your usual gauges.

 

 

 

[89 MJ]

2 hours ago, mnkyboy said:

The Ford M90 would be the easiest but I don't think either would be all that difficult, there's a guy in the boosted 4.0l group on FB that sells the bracket for the Ford M90 separately or he will sell you a complete set up minus tuning for around $800.

 

I know another guy that was selling the GM adapter but not sure if he still is offering them or not, either way it wouldn't be too difficult to make.

 

There's a few options for tuning, for low boost you could get away with old school methods such as an FMU along with bigger injectors, another option is a piggy back such as Split second, then there's a number of full stand alone ECMs you could convert to which would be best but also the most work.

 

No matter how you tune, you will want to make sure you have a wideband set up so you can monitor AFR along with all your usual gauges.

 

 

 

Thank you. I will look into those. What’s an FMU tune?

[mnkyboy]

An FMU is a device that blocks off the fuel return line under boost.  Blocking the return increases the fuel pressure and increases fuel flow through the injectors.

 

An untuned ECM is limited on how big of an injector it can run and still maintain a good idle/driveability, the FMU let's you run smaller injectors to keep the ECM happy but allows the smaller injectors to flow like slightly bigger injectors when you need more fuel.

 

Not as good as a real tune but will work as long as you don't get crazy with the boost

[89 MJ]

23 minutes ago, mnkyboy said:

An FMU is a device that blocks off the fuel return line under boost.  Blocking the return increases the fuel pressure and increases fuel flow through the injectors.

 

An untuned ECM is limited on how big of an injector it can run and still maintain a good idle/driveability, the FMU let's you run smaller injectors to keep the ECM happy but allows the smaller injectors to flow like slightly bigger injectors when you need more fuel.

 

Not as good as a real tune but will work as long as you don't get crazy with the boost

Interesting. Thank you. I’d probably only want to run 6-8 psi. I don’t need crazy power, I just want to say I have a supercharged MJ.  

[ghetdjc320]

You can use a rising rate fuel pressure regulator for the most basic fuel increase under boost. Superchargers have a fixed boost to rpm ratio so they are a bit easier to tune imho. Skankfoot racing makes a nice little turbo setup also. Stand alone efi is what I’ve done in the past but there are several tuning options. Boosted tech has kits for the Renix and obd1 MJ’s and use a split second auxiliary injector controller. It has a built in map sensor and adds fuel in boost. No timing control though and not much tuning. 

[89 MJ]

4 minutes ago, ghetdjc320 said:

You can use a rising rate fuel pressure regulator for the most basic fuel increase under boost. Superchargers have a fixed boost to rpm ratio so they are a bit easier to tune imho. Skankfoot racing makes a nice little turbo setup also. Stand alone efi is what I’ve done in the past but there are several tuning options. Boosted tech has kits for the Renix and obd1 MJ’s and use a split second auxiliary injector controller. It has a built in map sensor and adds fuel in boost. No timing control though and not much tuning. 

Interesting. Can one buy this Split Second thing on its own?

[ghetdjc320]

1 hour ago, 89 MJ said:

Interesting. Can one buy this Split Second thing on its own?

Yep. Splitsec.com

 

very simple but overpriced devices

[89 MJ]

10 hours ago, ghetdjc320 said:

Yep. Splitsec.com

 

very simple but overpriced devices

Thanks. I will check into them. 

[ghetdjc320]

1 hour ago, 89 MJ said:

Thanks. I will check into them. 

The boosted tech setup just uses an auxiliary injector controller form split sec to add fuel in boost. The split second device has a built in map sensor that gets connected to the manifold to sense boost and fires an auxiliary injector that is mounted to the supercharger inlet side. They feed fuel to the injector using the Schraeder valve on the newer style fuel rails. It’s a very simple setup but they’re leaving power on the table by only adjusting fueling. 

[89 MJ]

2 minutes ago, ghetdjc320 said:

The boosted tech setup just uses an auxiliary injector controller form split sec to add fuel in boost. The split second device has a built in map sensor that gets connected to the manifold to sense boost and fires an auxiliary injector that is mounted to the supercharger inlet side. They feed fuel to the injector using the Schraeder valve on the newer style fuel rails. It’s a very simple setup but they’re leaving power on the table by only adjusting fueling. 

Alright. I’m not looking for crazy power, just thinking of adding boost to be unique. 

[ghetdjc320]

46 minutes ago, 89 MJ said:

Alright. I’m not looking for crazy power, just thinking of adding boost to be unique. 

6-8lbs is not bad on a good running engine. Good for about 75-100hp

[89 MJ]

15 minutes ago, ghetdjc320 said:

6-8lbs is not bad on a good running engine. Good for about 75-100hp

Oh, that’s a lot of power. It would be cool though. 

[ghetdjc320]

1 hour ago, 89 MJ said:

Oh, that’s a lot of power. It would be cool though. 

Yeah, it’s a big increase but not too much given the displacement of the engine in the first place. You may have already seen these but here is a link to the guy building turbo manifolds and kits for 4.0’s: https://www.ebay.com/itm/Jeep-cherokee-XJ-20g-turbo-kit-1991-2001/324284305882?hash=item4b80d9d1da:g:GTQAAOSwq9ZfUmVa

He’s been here on the club before and own skankfoot racing. Boostwerks also makes a nice turbo manifold and turbo unit. I run a TJ JBA downpipe so the turbo downpipe would have to be fabbed up on my case. The turbo does fit nicely under the intake manifold and keep the engine bay pretty clean. Cleaner looking install than a supercharger imho. And if all your looking for is additional fueling than a rising rate fuel pressure regulator with a boost reference port will work fine. That and an AFR gauge for sure. One with logging like a zeitronics would be best.

[89 MJ]

9 hours ago, ghetdjc320 said:

Yeah, it’s a big increase but not too much given the displacement of the engine in the first place. You may have already seen these but here is a link to the guy building turbo manifolds and kits for 4.0’s: https://www.ebay.com/itm/Jeep-cherokee-XJ-20g-turbo-kit-1991-2001/324284305882?hash=item4b80d9d1da:g:GTQAAOSwq9ZfUmVa

He’s been here on the club before and own skankfoot racing. Boostwerks also makes a nice turbo manifold and turbo unit. I run a TJ JBA downpipe so the turbo downpipe would have to be fabbed up on my case. The turbo does fit nicely under the intake manifold and keep the engine bay pretty clean. Cleaner looking install than a supercharger imho. And if all your looking for is additional fueling than a rising rate fuel pressure regulator with a boost reference port will work fine. That and an AFR gauge for sure. One with logging like a zeitronics would be best.

Thanks, I am familiar with the Boostwerks stuff, but like I said, I’m just trying to come up with ideas. 

[Dzimm]

On 1/15/2021 at 2:20 PM, mnkyboy said:

there's a guy in the boosted 4.0l group on FB that sells the bracket for the Ford M90 separately or he will sell you a complete set up minus tuning for around $800.

 

Do you have any more info on this guy?  I searched around the group and couldn't find him anywhere.  This could be a game changer for me, I'd rather go supercharger but couldn't find a way I liked that didn't cost $4k.

[mnkyboy]

18 minutes ago, Dzimm said:

Do you have any more info on this guy?  I searched around the group and couldn't find him anywhere.  This could be a game changer for me, I'd rather go supercharger but couldn't find a way I liked that didn't cost $4k.

https://m.facebook.com/groups/941680179342225/permalink/1771913219652246/

[89 MJ]

20 minutes ago, mnkyboy said:

https://m.facebook.com/groups/941680179342225/permalink/1771913219652246/

Thanks. He says that everything can be included, but also says you are on your own for tune and injectors. Do you know which statement is true?

[Dzimm]

58 minutes ago, 89 MJ said:

Thanks. He says that everything can be included, but also says you are on your own for tune and injectors. Do you know which statement is true?

I'm assuming everything besides injections and tune because you need a dyno to properly tune as every vehicle is different.  Injectors are also changed based on how you want it tuned.  

 

I'm really tempted to buy one, good price for a kit.

 

[Dzimm]

1 hour ago, mnkyboy said:

https://m.facebook.com/groups/941680179342225/permalink/1771913219652246/

Thanks!

[89 MJ]

1 minute ago, Dzimm said:

I'm assuming everything besides injections and tune because you need a dyno to properly tune as every vehicle is different.  Injectors are also changed based on how you want it tuned.  

 

I'm really tempted to buy one, good price for a kit.

 

It definitely does seem like a fair price.