AeroNautical Posted March 23, 2015 Share Posted March 23, 2015 I was poking around my buddies 89 2.5 MJ today, looking for the source of some oil leaks, and noticed fuel lines coming out of his throttle body. And no fuel injectors. But he does have a TPS and IAC, which means it's a computer controlled fuel delivery. It also has a turbine inside of his ducting to the air box. I have never seen this before, my guess is the turbine circulates the air into a vortex, and the fuel is injected directly into the TB air mixture. Literally a computer controlled carb. Is this stock? I've never seen anything like it, but it's pretty bad @$$! Link to comment Share on other sites More sharing options...
benjy_26 Posted March 23, 2015 Share Posted March 23, 2015 The injector is right in the middle of the TB. As for the goofy pinwheel, tell him to scrap it. I can assure you that it's not helping. Link to comment Share on other sites More sharing options...
Rockfrog Posted March 23, 2015 Share Posted March 23, 2015 Haha that looks like one of those eBay electric turbo's ... About as effective as a paper mache' canoe. The "carb" is actually a Renix TBI unit, my buddy has the same system on his 90 2.5 YJ. Link to comment Share on other sites More sharing options...
benjy_26 Posted March 23, 2015 Share Posted March 23, 2015 Don't insult papier maché canoes, man! Those can actually work if made right. ;) Link to comment Share on other sites More sharing options...
Rockfrog Posted March 23, 2015 Share Posted March 23, 2015 Yeah, but eventually they just dissolve into the tissue they are. Still, they would work better than the electric "turbinators" Link to comment Share on other sites More sharing options...
Incommando Posted March 23, 2015 Share Posted March 23, 2015 If you ever hear of "throttle body injection" or "TBI" now you will known what they are talking about. Link to comment Share on other sites More sharing options...
yellaheep Posted March 23, 2015 Share Posted March 23, 2015 Looks like the "Turbo F1-Z"........... :laughin: http://www.ebay.co.uk/itm/TURBO-F1-Z-Air-Intake-Fuel-Saver-ECO-Fan-Universal-Fit-/320527054317 Pulled one of these out of a junkyard jeep a couple years back...... kept it for novelty/conversation piece. Link to comment Share on other sites More sharing options...
Eagle Posted March 23, 2015 Share Posted March 23, 2015 If you ever hear of "throttle body injection" or "TBI" now you will known what they are talking about. ^^^ This. That isn't a carburetor, it's a throttle body injection setup. Instead of one injector for each cylinder ("multi-port fuel injection"), the '86 through '90 4-banger in the XJ and MJ used throttle body injection, in which a single injector mounted in the inlet to the throttle body delivers the fuel. It's not exactly "bad @$$" because, although it's a bit better than a carburetor, it's nowhere near as efficient as multi-port fuel injection. Link to comment Share on other sites More sharing options...
Incommando Posted March 23, 2015 Share Posted March 23, 2015 Looks like the "Turbo F1-Z"........... :laughin: http://www.ebay.co.uk/itm/TURBO-F1-Z-Air-Intake-Fuel-Saver-ECO-Fan-Universal-Fit-/320527054317 Pulled one of these out of a junkyard jeep a couple years back...... kept it for novelty/conversation piece. There is a whole thread gone bad on here somewhere about gee-gaws and mods like that for the gullible to buy/do. It is hilarious. Link to comment Share on other sites More sharing options...
AeroNautical Posted March 24, 2015 Author Share Posted March 24, 2015 Yeah, that F1-Z thing looks exactly like what I found, guess the PO was one of the gullible ones. Any reason amc had this kind of fuel injection when they already had an engine that had multi port fuel injection produced at the same time? Also found a coolant line running through the intake manifold. I always thought the 2.5s were a 4.0 with 2 cylinders knocked off, but there are very few similarities apparently. Link to comment Share on other sites More sharing options...
Jeep Driver Posted March 24, 2015 Share Posted March 24, 2015 Yeah, that F1-Z thing looks exactly like what I found, guess the PO was one of the gullible ones. Any reason amc had this kind of fuel injection when they already had an engine that had multi port fuel injection produced at the same time? Also found a coolant line running through the intake manifold. I always thought the 2.5s were a 4.0 with 2 cylinders knocked off, but there are very few similarities apparently. They are extremely similar. Link to comment Share on other sites More sharing options...
87Warrior Posted March 24, 2015 Share Posted March 24, 2015 The heated intake manifold is there to prevent the throttle body unit from icing. Link to comment Share on other sites More sharing options...
AeroNautical Posted March 24, 2015 Author Share Posted March 24, 2015 Yeah, that F1-Z thing looks exactly like what I found, guess the PO was one of the gullible ones. Any reason amc had this kind of fuel injection when they already had an engine that had multi port fuel injection produced at the same time? Also found a coolant line running through the intake manifold. I always thought the 2.5s were a 4.0 with 2 cylinders knocked off, but there are very few similarities apparently. They are extremely similar. I worded that poorly, i know they are similar, but I was referring to the fuel and intake system. Atleast on these earlier 2.5s. The heated intake manifold is there to prevent the throttle body unit from icing. Cool, didn't know that either. Learning alot today! Link to comment Share on other sites More sharing options...
gogmorgo Posted March 24, 2015 Share Posted March 24, 2015 Any reason amc had this kind of fuel injection when they already had an engine that had multi port fuel injection produced at the same time? Short answer? It's cheap and easy. The 4.0 was a new motor. It needed a new intake, fuel system, etc. to go with it. The 2.5 on the other hand had already been in production for several years. Emissions and economy requirements meant that the set-it-once-and-forget carburetor needed to be replaced with a self-tuning system. If they had gone to mpfi, in addition to a new throttle body, they would have needed a new intake system, all the way from the filter housing to the manifold, as well as a new fuel system, pushing fuel to four different places. Going TBI meant they only needed to swap the carb out for a thorttle body, and add an O2 sensor and a higher-pressure fuel pump. They wouldn't need to redesign the intake manifold, air cleaner, or much else, really. Fewer new parts means lower design costs and much less retooling. Fun fact: Computer-controlled carbs are (were) an actual thing. Like with EFI, they use TPS, O2, and MAP sensors to regulate the fuel ratio, only instead of injectors varying their spray, they used solenoids to adjust the metering rods in something very similar to a traditional carburetor. Needless to say, the complexity prevented them from catching on. Link to comment Share on other sites More sharing options...
Rockfrog Posted March 25, 2015 Share Posted March 25, 2015 FYI - the AMC 2.5l was designed based off the AMC 4.2l platform, more or less a 4.2l with two cylinders knocked out. Add in some design changes here and there. The AMC 4.0l was intro'd 3yrs later after they basicly added the two cylinders back in. As for why they used TBI instead of MPFI ... They were too busy working on the 4.0 to fix what wasn't broken, then got bought out, and Chrysler likely did the usual takeover routine, spend a few years figuring out what they just bought, where to go with it, and how to do it. Once that was sorted, MPFI hit the 4cyl. Just my take on it. Link to comment Share on other sites More sharing options...
Jeep Driver Posted March 25, 2015 Share Posted March 25, 2015 I'm pretty sure that AMC adopted the TBI from GM who was already using it in the early 80s. Link to comment Share on other sites More sharing options...
Eagle Posted March 25, 2015 Share Posted March 25, 2015 I'm pretty sure that AMC adopted the TBI from GM who was already using it in the early 80s. I agree. The mystery is why they didn't also use TBI on the 2.8L V-6, which actually did have a computer-controlled carburetor. Years ago I had the local carburetor guru (the guy all the professional and hobby racers in the area went to for fuel delivery issues), and he was reluctant to even touch it. He did finally agree to throw in a basic rebuild kit and set it to default settings so it would run, but he said that carburetor was one of the worst ever used on an American vehicle. Link to comment Share on other sites More sharing options...
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