Hey there,
I'm considering two possible engines to put in my 92 firebird 305 TBI. The LS1 comes with the computer intact but the RamJet 350 comes with a "MEFI 3 controller". Does this controller eliminate the need to replace the ECM?? I see lots of info on LS1 swapping, has anyone worked with the RamJet 350 and if so, could you recomend which to be the best one for my case, if not another one all together? thanks.
-Duncan from Virginia

 

Welcome aboard.

A few guys and magazines have done the RamJet in a 3rd gen. The controller doesn't "eliminate the need to replace the ECM", but it will control the engine without help from the now brain-dead ECM.

Someone a while ago was working on converting a RamJet to be controlled by a TPI computer, I don't recall hearing how that came out.

Emissions may be a problem because the RamJet is open-loop and not programable.

 

I agree on the non-programmable MEFI-3 controller, but why couldn't he use the sensors he currently has on his 305 (would have to add a MAP sensor most likely) and use his 305's computer and harness? How/Why would that be any different than someone sawapping in a TPI 383 for their old 305? (Like I just did) He would definitely need a custom chip done but probably not too much different (if at all) than any other higher output 350 or 383 setup.

The only thing I can think of that he might run into trouble with is the EGR, but I believe Scoggins Dickey, and possibly some others, have a kit to get that working as well (some variation on their TPI Vortec manifold EGR kit). May need to have a vacuum port or two plumbed into the plenum as well (worst case). If he wanted to stay with his current transmission and driveshaft set-up, that would certainly be a lot easier and cheaper than an LS1 swap wouldn't it?

Just my opinion, and maybe I missing something. Am I? What? It's still a SBC....



- Vern

 

It all sounds do-able on paper.

Just need to hear from a do-er.

But, you could just install the motor as-received, and it will run just fine. TCC lock-up and emissions would not be covered by the controller.

 

hhhmmmm.... So what exactly does this MEFI controller do exactly if it isnt programmable and doesnt cover all the engine functions? Just what functions does it not cover other than TCC Lockup and EGR Valve. From reading about the RAMjet, the ads for it make it seem like you just bolt it on, hook up the fuel and go and let the controller do all the work. Correct me if I'm wrong but is TCC Lockup something specific to automatic transmissions, mine's a 5-speed. Also, It's my understanding that an EGR serves no other purpose than to lower flame temperatures to reduce the amount of NO gas produced. I could care less about any tree hugging features that would dilute my charge, even without one I'm sure it would be cleaner than my ragged old 305 smoke stack. One worry might be if there is no EGR then maybe the engine may run a bit hot, right? thanks again guys. I'm just a mechanical engineering student, they just teach me the numbers, not so much the hands on.

 

Good choice on major Anyways, the ram jet runs a open loop system like five 7 poined out. It odes not use an 02 sensor like you stock set-up does. Therefore you cannot adapt your comp[uter to work with it. However, you only need to use the computer that it comes with (beauty of EFI crate motors). You will need an upgraded fuel system to handle the high fuel pressures that multi port set-ups require. The ram jet comes with everything you need to complete the swap. That is minus exhaust and fuel upgrades of course. Hot Rod mag did a great swap into a 3rd gen. I will dig up the link for you.

 

You aren't paying attention in class...

The controller covers all of the engine functions. It doesn't cover all of the vehicle functions.

You did notice the footnote about "For off-road or pre-1975 vehicle use only."

 

Right! The factory setup on the RJ350 uses a fixed fuel and timing curve (hence no o2 sensor). If you make any engine modifications from what they send you engine-wise (and recommend exhaust-wise) at all you'll throw it out of whack and be looking at a new ECM and chip, and probably a harness too. Sounds good for a "plug and play" type person, but not for a "tinkerer" like most of us.

Just my two cents....



- Vern

 

Just to clearify on the Ramjet 350's MEFI controller. I have
recently bought and now in the process to wiring up the
Ramjet 350 crate motor in my car. My Ramjet 350 DOES
NOT have the MEFI 3 controller, but the newer updated
MEFI 4 controller, which uses a CLOSED LOOP operation
controlled with 02 sensor and air intake sensor. It still
DOES NOT use an EGR system, but this updated controller
will help reduce emissions (along with a converter) and a
smoother idle due to better air/fuel ratio control with the
help of the additional sensor inputs. The previous MEFI
3 controller is now discontinued, at least for the most part.
There may still be some Ramjet 350s for sale with the older
computer out there. Also, this controller has been offered for
the Ramjet for at least a year now. So, this news is actually
nothing new to anyone but to people who don't research
on it first!