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i admit that i think too much but do you suppose its possible to run dual ' carbs ' with TBI kind of like the old dual quads. i know it would be completely unnessesary and take some thinking but it would be cool wouldn't it , and isn't that what its all about. :toocool:
go for it all you need to do is mount another TB and tie into from the first TB. 4 wire hook up.:cool: :HMMM:Quote:
Originally posted by 53 Chevy5
i admit that i think too much but do you suppose its possible to run dual ' carbs ' with TBI kind of like the old dual quads. i know it would be completely unnessesary and take some thinking but it would be cool wouldn't it , and isn't that what its all about. :toocool:
Chevy put some dual TBIs on Corvettes, Never seen one run realy well!
never seen one, but with a computer and few sensers it should work.:cool:Quote:
Originally posted by randywrench
Chevy put some dual TBIs on Corvettes, Never seen one run realy well!
crap, it's been done before? oh well, never mind then. the pickup is going to be a daily driver mostly for the wife and if you say they didnt run too well i think i'll really forget about it.Quote:
Originally posted by randywrench
Chevy put some dual TBIs on Corvettes, Never seen one run realy well!
GM called this system Crossfire fuel injection. Only used in 1983 and1984 corvettes I think they put them on F bodys one of them years.
you gonna make it run better :rolleyes:Quote:
Originally posted by 53 Chevy5
crap, it's been done before? oh well, never mind then. the pickup is going to be a daily driver mostly for the wife and if you say they didnt run too well i think i'll really forget about it.
was i suppose to send you something today chev. 5 ? if i was i did.:confused:Quote:
Originally posted by lt1s10
you gonna make it run better :rolleyes:
with the help of your diagram, i hope so. :)Quote:
Originally posted by lt1s10
you gonna make it run better :rolleyes:
did you get that guy stright on the vet randywrench ?:cool:Quote:
Originally posted by randywrench
GM called this system Crossfire fuel injection. Only used in 1983 and1984 corvettes I think they put them on F bodys one of them years.
let me know when you get them. **) :toocool:Quote:
Originally posted by 53 Chevy5
with the help of your diagram, i hope so. :)
Havent heard back from him, found out you only need the L wire hooked up to make it charge.
will do, it wont be running as quickly as i'd hoped, going to get some work done on it. getting bored, ballanced, crank polished, seats in the heads. but then it'll be good for many miles.Quote:
Originally posted by lt1s10
let me know when you get them. **) :toocool:
thats what i couldnt understand with the interl. reg all you need is a ground for them to work. :confused:Quote:
Originally posted by randywrench
Havent heard back from him, found out you only need the L wire hooked up to make it charge.
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:whacked:
.all the fuel is going into the intake just like it would with one TB. the o2 would do the samething it allways does.:HMMM:Quote:
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:whacked:
wouldn't it work if you had two o2 sensors, one for each set of injectors ?Quote:
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:whacked:
wouldnt change anything you dont have but 1 computer.:HMMM:Quote:
Originally posted by 53 Chevy5
wouldn't it work if you had two o2 sensors, one for each set of injectors ?
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. :cool:
Quote:
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.:HMMM:
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 :cool:Quote:
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.
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......
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? :HMMM:Quote:
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......
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..Quote:
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? :HMMM:
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. :cool:Quote:
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..
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?
all of this talk almost tempts me to try it. the biggest hangup right now is i would have to cough up big bucks for a dual quad intake for a 348 and not know if it would even work good. another thing is i know i wont have enough cam and exaust to handle the fuel. i'm going to be sitting at 300 hp with this motor so mabey one unit would be the smartest. ( still not the coolest though :toocool: )
you need to get what youve got working first then worry about that. :HMMM: :LOL: :LOL: :LOL:Quote:
Originally posted by 53 Chevy5
all of this talk almost tempts me to try it. the biggest hangup right now is i would have to cough up big bucks for a dual quad intake for a 348 and not know if it would even work good. another thing is i know i wont have enough cam and exaust to handle the fuel. i'm going to be sitting at 300 hp with this motor so mabey one unit would be the smartest. ( still not the coolest though :toocool: )
I don't think it's possible to use the GM ECM to run the proposed dual throttle bodies, at least not without a substantial amount of work.
The GM injectors are low impedance (Lo-Z), usually around 1 ohm cold. Doubling the load would almost certainly overheat the drive FETs. You'd have to intercept the drive signals from the ECM, then buffer them individually for the four drives.
Use only the original O2 sensor, having two in the circuits is no better than having two watches - you're left with the question "which one is correct".
Plan on custom code for the ECM. It has a base fuel map which it follows in a rough manner, maybe within 10% of stoic. The O2 sensor just fine tunes the mess. With the dual throttle bodies and injectors the ECM will probably be off the map (pun intended).
You may be better off using a pair of aftermarket throttle bodies, then pick up 8 Bosch type injectors off eBay.
Typical throttle body :
http://www.auto-nomics.com/cgi-bin/s...rt=10850-002-D
You can also find a small EFI controller on ebay, the MS EFI units work well. You can put together a radical looking system for around $500-600. Just set it on top of a dual quad manifold.
FWIW, the Apple IIE has more horsepower in it's little 6502 processor than all but the most current automotive ECMs. The newest crop are DSP based, but still only in the 33MHz range. It's this bloated pig called windoze which has led us to believe anything less than 3.8GHZ is too slow to be useful.
A multiport would be a nice aproach, but I'm not aware of any single plane or tunnel ram manifolds available for the 348/409 engines. The fuel logs would be a pain to implement with a dual plane manifold. You'd really like the port runners at the same elevation to make life easy.
Regards, Mark
i like the EFI idea but i miss the experimenting :cool:Quote:
Originally posted by drg84
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?
i got nothing else to think about while the motor is getting work. well, mabey i could finish putting the rearend in, sandblast the frame, paint it , set the body on do the rest of the body work to it and paint it , finish the interior and air conditioning, put the windows in and install an air freshener in the mean time **) .Quote:
Originally posted by lt1s10
you need to get what youve got working first then worry about that. :HMMM: :LOL: :LOL: :LOL:
that could tie you up for a few hrs.:HMMM: :LOL: :LOL:Quote:
Originally posted by 53 Chevy5
i got nothing else to think about while the motor is getting work. well, mabey i could finish putting the rearend in, sandblast the frame, paint it , set the body on do the rest of the body work to it and paint it , finish the interior and air conditioning, put the windows in and install an air freshener in the mean time **) .
I'm going to be doing a dual TBI setup on my shortbed chevy. Holley makes the throttle bodies up to 1000 CFM, and they make the Y adapter to connect the 2 to the computer.
I'm doing dual 670 CFM Throttle bodies with 85PPH injectors on a chipped up computer.
Quote:
Originally posted by Colbycheesiest
I'm going to be doing a dual TBI setup on my shortbed chevy. Holley makes the throttle bodies up to 1000 CFM, and they make the Y adapter to connect the 2 to the computer.
I'm doing dual 670 CFM Throttle bodies with 85PPH injectors on a chipped up computer.
let me know that works.
I'm working on this project as we speak. I have a 1990 Camaro with a 302ci motor. I picked up the Offenhauser dual crossram intake along with two TBI to 4 bbl adapters. This is kinda my homage to Duntov. Working with Dual 850CFM TBI units. Problem right now is getting the linkage made. Olny going to use one of the throttle position sensors. Just hoping that I dont have to screw with the wiring to bad when I split the injector signals......
Also for better O2 readings I upgraded to a 4 wire......
The Crossfire injection can be made to work nicely. The biggest drawback is the very simple ecm that ran them. There's a cure for that though, although it's not cheap.
http://www.turbocity.com/product_inf...roducts_id=455
http://www.turbocity.com/product_inf...roducts_id=358
http://www.turbocity.com/product_inf...products_id=20
Guess you really, really have to want to be different.
Then there's this http://www.megasquirt.info/ which the magazine people say works very nicely for under $200.
And it's completely tunable.
http://www.carcraft.com/techarticles/116_0403_mega