Anyone get the Ram Jet intake to run off the TPI comptuer or some other computer.

 

Would be a pretty easy swap. Just the intake is designed for vortech heads, I dont know it that can be redrilled... It may also require a custom fuel rail, for the batchfire TPI.

It doesnt reall have anything on a Super Ram, though...

 

I have been advocating this for quite a while. In fact, I think the 7730 SD ECM and the Ram Jet would be a "marriage made in heaven".

You'd need to add an O2 sensor but this would be a GOOD thing to do. I've seen a number of posts where guys have "slightly modified" their Ram Jet and because it has no O2 sensor for part-throttle, they either run rich or lean all the time.

With the 7730 SD, you can disable all the EGR, VATS, CCP, AIR etc very easily. You'd need to modify the VE tables but it would resemble a VE Table from a Miniram/LT1 setup but it is realatively easy to "scratch up" a draft VE Table and then using the "P730 - Part Throttle VE Table tuning (no PE)" https://www.thirdgen.org/techbb2/sho...threadid=39254 it would be really simple to tune.

It would also be theoretically possible to "marry" a MAF system to it, but I thnk SD would work better.

Don't be afraid to be the first. It's far easier than anyone thinks. ECM swaps are done all the time. It's just that no one has done this one but there is no reason why it shouldn't work.

 

I can almost guarantee you would NOT need a new fuel rail. Batch vs. sequential has nothing to do with the fuel rail itself. Sequential would just tell the injectors to fire individually (via wiring), instead of sending the signal to all of them at once (may need to rewire the injectors for this). I can't understand why GM would make it sequential because it would never have to meet emissions, the power differences are neglegable, the complexity would be higher (wire harness), and the cost would be more. I guess the MEFI 3 is cheap or something.

Instead of trying to get the TPI computer to work with it, is it possible/easy to modify the ramjet's computer to work with modifications (I'm not talking O2 sensors or anything, just things like cam swaps, etc.)? Probably. But, you probably don't have the computer, or else you wouldn't have asked. The only problems I can see with what you want to do are 1) Emissions/EGR/other 2) Vortech heads bolt pattern.

 

The sequential system is good for the LT1 and LS1, but really has no purpose in the Ramjet. The thing is programed rich so the problem of lean cylinders isnt an issue, because the air has no chance of detonating. The thing is EGRless so it will never pass emissions anyway... I am in total aggreement with you.

I dont see the point of this becaue the reworking you would have to do is not worth the 300 and some horses of that motor... and with the Vortech heads patter would limit the aftermaket of hot rodding this thing extremely. Is the header flange bolting different that the standard SBC?

 

To my knowledge, the MEFI 3 is not emissions legal as it doesn't support an EGR or an O2 sensor. As RednGold mentions, the fuel rails has nothing to do with it being "batch vs sequential" - that's controlled by the MEFI/ECM and how it's wired. In fact, look at ALL the guys that are converting LT1 intakes to work on TPI engines. They use the stock LT1 fuel rails REGARDLESS of whether it comes from an SEFI or Batch Fire LT1 (remember LT1s used both).

The MEFI 3 is a simpler device than a SD 7730, but there is currently no "readily available" method to alter the programming. You are stuck having to get some companies that had "contacts" with GM like AS&M to charge you an outrageous price to do a "half *** job".

I would toss the MEFI 3 in a heart beat and go SD 7730. The MEFI 3 is far more limited in it's programming. That's why GM states that the Ram Jet is limited to "pre-emissions" vehicles and was never intended to be a replacement for TPI cars. Though if GM had put just a "little more effort" they could have EASILY made it (just needed an EGR).

 

Actually, it's programmed to run rich because it doesn't have an O2 sensor.

 

The guy I talked to at Pace Parts said using the stock ECM (7730) instead of the one that comes with it would be easy to do, and probably a good idea. IIRC, he also said the RamJet was batch-fired to begin with. Using a 7730 is the only way I'd ever run a RamJet.

 

That's been my understanding too. Though it's irrelevant.

But I can't see GM putting in the "sophistication" needed for SEFI yet not have an O2 Sensor? Also, it's kind of funny, but from some of my "pals" that have been "investigating/hacking" the LT1's 8051, it seems the SEFI systems generally only work in in "sequential mode" at "part-throttle" and go "batch" in WOT.

The rational is that it would require a much bigger (at least 3 times) of an injector to work in "pure sequential mode" timed to the valve's openning/closing when in WOT than "batch mode" where the injector "pulsates" throughout the entire operating cycle of the engine, independent of "valve timing". With "sequential" timed to the valves' opening/closing you only have between 1/4 - 1/3 of the crank's rotation to squirt all the fuel in (based on the cam's duration); hence the 3x larger injector required for WOT IF the injector was "sequential" in WOT.

That is why there wasn't a "noticeable gain" when GM switched from "sequential injection" on the LT1 from "batch fire"...because it's still batch fire in WOT. Sequential is primarily for "fuel economy and emissions".

 

I am surprised no one mentioned this, but I would think the big problem would be the throttle body. A tpi sytle won't work (I think it uses an ls1 tb) you would have to deal with a completely different TPS and IAC. Who knows if the programing can be made to deal with those. There was some guy around here who got a ramjet intake and fuel rails, but I never heard if he got it running.

PS. They are 'Vortec', 'Vortech' is a supercharger company.

 

The reason I ask is because the bare Ram Jet intake is $450, about the same as a high end TPI base. So I was wondering if anyone used it yet without the whole $$$$$ package that GM sells.

 

Damn, I'm starting to wish I'd kept my coorespondance with the Pace Parts guy. He answered a ****load of questions that I asked. I think he said that it uses a 3800 throttle body. I can see what you're thinking (Tas), but from my POV, it'd be close enough to an LT1 that I'd choose the LT1 intake just 'cause it looks cooler. Have you seen the RamJet502's intake? Now something similar to that would look pretty cool on a 355.

 

Yes, you will need the LS1 style TB and most likely "splice" into the LS1 type connectors. But once connected, then it's just an "electrical signal". For the TPS, you'd adjust it to be in the .54-.69 range for idle and make sure you are getting somewhere around 4.00+ volts at WOT. But the "controlling" of the ECM based on TPS reading is all adjustable within the ECM.

As for the IAC, again, no biggy. You'd need to do an initial adjustment for idle. And then the ECM just "steps" the motor. Again, the size and magnitude of those steps may need a little "tweaking" in the eprom but we do that all the time when you swap a cam...no biggy either.

 

With all of these small twueks to the ECU, what ECU would you use? Would you convert to a flash programmable or make a custom chip? Sounds like all of the playing around with it, that you would end up burringing a lot of chips, that is, even if you have access to the hardware to do that sort of stuff.

Converting to a standalone ECU would be pointless, and irrelivant to this point, because Tas is asking if the if it would run off of the - 92 Gm comp?

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Sorry if I sound iggnorant, but I am a new timer to EFI tuning... This is all very interesting though...