Thread: dual TBI ??

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Originally posted by drg84
I think that theres a reason that this system wouldn work too well. Remember, gm TBI style fuel injection is based on the o2 sensor and the crankshaft sensor. System runs rich, leans back the injectors, system runs lean, richens it out. Now, with one set of injectors there is an even draw from the set. However, with a dual set there is now 2 injectors per cylinder, each one covering 2 clyinders. As such, when the system registers a rich code, there is now two seperate systems to lean. But, if the engine has one set running correctly and one spraying too much, there is no way to compensate. Same applies if it is too lean. Simply put, "too many chefs ruin a soup" Were you to actually run this type of system, the best bet would be to run two independant manifolds for each se of injectors. Then run your O2 sensor for two cylinders on each bank. In effect, this would have the EFI setup of two V4s but the power, ignition and fuel economy of a V8. If Anyone follows me

.all the fuel is going into the intake just like it would with one TB. the o2 would do the samething it allways does.

Originally posted by drg84
I think that theres a reason that this system wouldn work too well. Remember, gm TBI style fuel injection is based on the o2 sensor and the crankshaft sensor. System runs rich, leans back the injectors, system runs lean, richens it out. Now, with one set of injectors there is an even draw from the set. However, with a dual set there is now 2 injectors per cylinder, each one covering 2 clyinders. As such, when the system registers a rich code, there is now two seperate systems to lean. But, if the engine has one set running correctly and one spraying too much, there is no way to compensate. Same applies if it is too lean. Simply put, "too many chefs ruin a soup" Were you to actually run this type of system, the best bet would be to run two independant manifolds for each se of injectors. Then run your O2 sensor for two cylinders on each bank. In effect, this would have the EFI setup of two V4s but the power, ignition and fuel economy of a V8. If Anyone follows me

wouldn't it work if you had two o2 sensors, one for each set of injectors ?

Originally posted by 53 Chevy5
wouldn't it work if you had two o2 sensors, one for each set of injectors ?

wouldnt change anything you dont have but 1 computer.

Lt1, your looking at it wrong. Your assuming the cylinders will stay in perfect harmony all the time. but you know as well as i do that compression changes, cylinders run differently, ect. Thats why them made multiport. But with only one O2 sensor to handle two throttle body, the very concept is flawed. Whats the point of having 2 efi systems if your going to have them based on one input sensor?

no youer looking at it wrong drg i never said it would or wouldn't work i don't know.if the IFI is getting close to 100% it cant do an more no way but he is putting this on a 348 so it might do some good i don't know. he said that's what hot roders do (try things)so i told him to go for it. you said it wouldn't work. in my younger day i would have rigged it up and tried it without asking anybody. if it had work id told somebody if it hadn't worked then i would have been a couple 100.00 lighter and knew something for sure instead if guessing. ive spent a small fortune in my lifetime proving myself wrong.

Originally posted by 53 Chevy5
wouldn't it work if you had two o2 sensors, one for each set of injectors ?

How about multi port injection, 8 injectors and only 1 oxygen sensor, they run really well!

[QUOTE]Originally posted by randywrench
How about multi port injection, 8 injectors and only 1 oxygen sensor, they run really well! [/QUOTE


the more injectors you run then the more efficient the motor will run, and 2 -o2 sensors will run better than 1. youer fine tuning it then. everything you add to the computer incoming and out going, the more efficient it will run. i not sure what % a computer car runs but i guess when its right its close too 100% a factory carb. car runs around 80%. so there is room for a lot of improvements.

DRG84, I don't see why there would be a problem with the computer being able to control that. This isn't 1978. I have a calculator that can solve 3rd order differential equations. Any computer today can certainly take a couple measly input parameters and calculate an output parameter. 2 throttle bodies or not.
The only way a computer could compensate for individual cylinder variations due to compression and crap like that would be if there was an 02 sensor in all 8 primary pipes. Then if it was mpi it could vary each injector individually.
8 inputs and 8 outputs is still NOTHING for a modern computer to calculate.

Originally posted by tcodi
DRG84, I don't see why there would be a problem with the computer being able to control that. This isn't 1978. I have a calculator that can solve 3rd order differential equations. Any computer today can certainly take a couple measly input parameters and calculate an output parameter. 2 throttle bodies or not.
The only way a computer could compensate for individual cylinder variations due to compression and crap like that would be if there was an 02 sensor in all 8 primary pipes. Then if it was mpi it could vary each injector individually.
8 inputs and 8 outputs is still NOTHING for a modern computer to calculate.

well put tcodi and if we are talking along the same lines i think somewhere along the line then the next step is not nessery or wouldnt be cost effective. with the computer it could be made to do most anything you wonted it to do

ther is a company that sell this already in a kit ! i have seen there ad in the back of a magazine . i cant find the ad here at work because i dont have any magazines here . but look in carcrap or camaro rod one of the two will have the ad in it .

Only problem I see would be the injector drivers in the ECM, I'm not sure they could take the load of 2 throttle body's,although theres lotsa companys out there doin performance upgrades that might be able to solve the problem......

Originally posted by HWORRELL
Only problem I see would be the injector drivers in the ECM, I'm not sure they could take the load of 2 throttle body's,although theres lotsa companys out there doin performance upgrades that might be able to solve the problem......

he is putting this TB off of a 350 on a 348. im not sure but i dont belive that the computer would run the motor lean to the point of burning a hole in the piston no way. i think it would show up as something else before it got that bad, even if you didnt do anything to it. a good chip wouldnt hurt, but i dont belive nessary. any opinions on this?

Originally posted by lt1s10
he is putting this TB off of a 350 on a 348. im not sure but i dont belive that the computer would run the motor lean to the point of burning a hole in the piston no way. i think it would show up as something else before it got that bad, even if you didnt do anything to it. a good chip wouldnt hurt, but i dont belive nessary. any opinions on this?

Don't think ya understood my post, didn't say nuthin bout it runiin lean, I was referring to the injector driver in the computer (Quad driver) it'll only take so much load before it burns out..I'm just not sure the stock quad driver would take the load of 2 throttle body's, But I'm sure someone can update the drivers to handle it..

Originally posted by HWORRELL
Don't think ya understood my post, didn't say nuthin bout it runiin lean, I was referring to the injector driver in the computer (Quad driver) it'll only take so much load before it burns out..I'm just not sure the stock quad driver would take the load of 2 throttle body's, But I'm sure someone can update the drivers to handle it..

sorry about that HWORRELL you had a good answer and i think you are right. should not have used your quote i kinda went off somewhere over in left field with a dif thought. so far ive pretty much gone by the book on these things so its hard for me to talk about what it might do, im gonna have to do something about that. i wouldnt have though it would burn them out though, but i guess it could.

Wow, this has become one amazing thread. Nice to see this much input As for the %80 remark Lt1, your right. There is room for improvement. But based on current computations, its more than possible. Based on an outdated downdraft with 1984 technology, it wouldnt work. We have to remember that computers are constantly updating. In 1984 the top of the line was a AppleIIE with 740K of memory running at somewhere around 7 mhz. And even then, the automotive computers had not had the required sensors to evaluate differing running conditions. Anyone who has worked on a newer system knows that the computer can actually read misfires due to differences in voltage off the plugs. Basicly what im saying is that a dual TBI would be possible, but with a system that can read the engine, not guess at it. But if your taking that route, a Multiport would be much more effective. A cheap and easy way to accomplish this would be to locate a engine with the sensors already in place for a multiport setup and program the computer for dual TBI. Then it would run decently and still have the shock value. In fact, i wonder how much it would take to update a Cross-fire system?