desperado Posted August 3, 2006 Report Share Posted August 3, 2006 Need some opinions. I have a 1 ton Chevy with a 454 (7.4L) TBI in it. the TBI is heated with the water circuit that feeds the heater core. I am considering bypassing the water flow to the TBI. The only thing I can figure it's for is quick heatup's in the winter, but I could be wrong on that. I am hoping that it will increase the fuel economy some as the thing drinks fuel like there's no tomorrow. I have already found the fan clutch was locked up causing it to drink fuel, but I want to do what I can with it. This EFI shit is all new to me, I know heating a carb is pointless except for emmisions, and I don't care about that. Quote Link to comment Share on other sites More sharing options...
evan9381 Posted August 3, 2006 Report Share Posted August 3, 2006 TBI = throttle body inlet? im guessing? its one of the cheap/free/common mods a lot of people do on the hyundai boards im on... on our TBs theres the inlet/outlet nipple right next to each other...we just pull the hoses, and either get a new hose and loop it around, or a small pipe in the 2 tubes you just pulled to let the coolant flow thru...it keeps the coolant from surrounding the throttle body and keeps the intake temps down a couple degrees (very minor, but a couple) and gives a TINY better throttle response Quote Link to comment Share on other sites More sharing options...
twistedfocus1647545489 Posted August 3, 2006 Report Share Posted August 3, 2006 TBI= Throttle Body Injection. An early form of EFI where the injectors (in this case 2) are mounted on top of the throttle body and spray through it. Kind of the gap between carburetion and Multi-Point EFI like on your Hyundai. As far as blocking the water passage heating the TBI unit, its possible that it could help with mileage by decreasing the temp of the air charge, but older GM TBI systems seem to be very inflexible to change and I wouldn't be surprised if it caused some other drivability/tune issues, especially when it's cold out. AFAIK you're on the right track as to what it's purpose is, quicker warmup/emissions compliance, but the factory tune is done with all of these kinds of things in place and it doesn't take alot of deviation to cause other problems. I have not personally done it, though, and it might be worth a try. Quote Link to comment Share on other sites More sharing options...
Lustalbert Posted August 3, 2006 Report Share Posted August 3, 2006 Warm air is less dense. removing the heater will cause the air charge to be more dense, and will require more fuel. If you want, port the EGR valve to flow a little more, so you will be running more inert gas in your intake charge. What kind of #s are you getting? I have a 455 with a 7.4 TBI unit, and it gets about 18. You could consider ditching the stock computer and going megasquirt so you can play with the a/f ratios. Also, is the stove installed on you exhaust manifold? I provides hot air (less dense) so it will hurt fuel economy if it is not installed. Quote Link to comment Share on other sites More sharing options...
evan9381 Posted August 3, 2006 Report Share Posted August 3, 2006 sorry...guess i was thinking of something else and FWIW, in my hyundai, the injectors are on the IM about 1" from the head shooting directly into the intake valves...about 14" in distance from the actual TB Quote Link to comment Share on other sites More sharing options...
twistedfocus1647545489 Posted August 3, 2006 Report Share Posted August 3, 2006 sorry...guess i was thinking of something else No problem. I wasn't meaning "hey, you're wrong". I was just pointing out that TBI is kind of the evolutionary step between carburetors and more modern Multi-point systems used on engines today (which is the type you were thinking of). Multi-Point systems use an injector per cylinder and are typically located on the intake manifold very near the intake runner of the head (like on your Hyundai). It makes for better efficiency and flexibility b/c your intake just has to flow air, and not a mix of air and fuel that you have to hope stays atomized and distributes evenly (as is the case with Carbs and TBI). Quote Link to comment Share on other sites More sharing options...
evan9381 Posted August 3, 2006 Report Share Posted August 3, 2006 yeah, i didn't take it as that. good explanation though...learn somethin new every day Quote Link to comment Share on other sites More sharing options...
Clifford Automotive Posted August 3, 2006 Report Share Posted August 3, 2006 believe it or not that hot water keeps your butterflies from freezing.... true story not just in the winter Quote Link to comment Share on other sites More sharing options...
desperado Posted August 4, 2006 Author Report Share Posted August 4, 2006 As far as actual numbers right now, less than 8 per gallon. Mind you the fan cluth is locked up, so I am running a 5 blade fan at full speed all the time. And it's a dually crew cab, so even as big as your car is Andrew, it's alot smaller than my 24 feet, 7400 lb truck. Now I see your point about the air density, but will it not also make more power with denser air? My thinking is that more power means lighter throttle, equalling out to less fuel. Banks sells an exhaust and header kit for this motor claiming better fuel economy through better air flow. Again more air is also more fuel, but better flow equals better over all efficency, at least that's what I am thinking. But the megasquirt idea does have merit as well, I could tune it for being unloaded, and lean it out a bit, then when it's needed I could retune it. I don't know alot about a megasquirt. Can it be as simple as a switch? Or would I need to push up a new tune to switch it. I am planning on having a laptop on board anyhow, so it wouldn't be a big deal either way. (Nice thing about having that big a vehicle). Hell, I am planning on having a couple camera's on the outside, maybe I need to look at a PCMCIA video input card as well, the camera's are 12 volt, and I have that more than covered anyway (140 Amp alt and 3 batteries). Either way, let me know if I am way off track with the air density thing. I suppose I could just do it, but I am already in process of replacing the fan clutch so that will give me a large change in fuel economy before I even get to the TBI heater. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.