Ever wonder if you can get a VAFC to run you Jeep?

[CSaddict]

You can. I hooked up an Apexi VAFC and an MSD BTM in my Jeep today. Fired up first shot. Why an I telling you this? I am turboing my Jeep and need to scale down 36 lbs injectors. You may be interested because you can scale back your stock injectors in cruise and get better gas mileage.

Yes, a VAFC is designed for Hondas with VTEC but you don't need to use that portion. I paid $85 shipped for this unit.

[crosbike]

cool. too bad i have no idea how to do such a thing.

[CSaddict]

Its actually really easy with the ECU pin out. I got it on Shopkey and all the wires I traced back to the components and confirmed with an ohm meter. All you need to do is tap the power, ground, RPM signal, TPS signal, and then cut and intercept the map signal.

[crosbike]

sounds like a bunch of connections i can fuck up.

in all serious what do you think you can do for mpgs?

[XJLI]

dave, do expand on this please. if its just as easy as using this i wont even bother building a custom map sensor and gauge. i wanted to run the big 5.0 injectors on my jeep but didnt want the high lb/hr all the time.

[CSaddict]

Stock 5.0 injectors are 19 I believe. You may be wanting the 24's. I just gave a set of 8 back to the shop because I didnt use them. Basically this unit works like an adjustable map sensor but you can scale the injector depending on the RPM and you also have the load you can adjust via the TPS value.

Keep in mind when scaling injectors with an adjustable MAP or an AFC you will be advancing the timing so plan accordingly.

[Bucket-O-Karma]

This is all greek to me

[XJLI]

right i was looking into the 24s. im pretty sure my stockers are 20 or 21, but with the cowl intake, bored tb, and newer intake manifold i feel like im getting a lean condition when im really on it. are you using a a/f meter as well? what effect does the timing have when scaling back? should the timing be retarded when scaling back on fuel, and advance when scaling up?

[CSaddict]

Im going to be using a PLX wideband. This is the actual one I bought and it was delivered today. www.plxdevices.com/products/dm5/afrsmcombo/ I paid $242 shipped from Needfultoyz on Ebay. They are a great company.

Knowing the exact A/F is the only way to do it right.

The timing advance depends on the MAP voltage being supplied by the Air fuel controller or Adjustable map. If you scale large injectors the timing advance will be greater. Going from 20ish to 24 will not be a big deal. If anything you will see more power and maybe better mileage if you get the tuning down. Scaling injectors back will put you lower in the ignition map and will advance you a bit depending on the RPM.

[XJLI]

so you think going larger than 24 is a good idea? i'd like to know what a stock xj runs a/f wise. i read 14.6 is the ideal for efficiency right? anything to make these tractor motors more efficient is a good thing.

[CSaddict]

14.7 being ideal is in the eye of the beholder. 15.0-15.4 would net better fuel mileage but you would want high 13's wide open up top. I will need to be in the 12.0 range under boost but in the mid 14's in vaccuum.

[Dr. Thunder]

Noob to turbos alert but what do you do when adding a turbo to a non turbo car for the vacuum accessories? Get a pump or what?

[CSaddict]

You will always be in vacuum if you arent into the throttle. Turbo cars only go into boost under load. So, I guess your question is really the brake booster. When was the last time you applied your brakes with you foot deep into the throttle? You don't even notice the lack of vacuum.

[Dr. Thunder]

I was thinking that but, figured I'd ask. What about have pressure going to your brakes, heater controls etc. That's gotta fuck with something. Guess I should have been more specific

[CSaddict]

I have never seen a non factory turbo car where a turbo was added that ever damaged any vacuum actuated components. I suppose in all actuallity it could happen. I have seen it.