How much difference is there in Multiport EFI with single seperate throttle body set up properly vs individual throttle body injection per cylinder, hope I worded this correctly, especially if you may boost it in the future. TIA, I know one thing there has to be a tremendous difference, because there is a huge price difference, I think I may be the first, I am having an intake manifold from CI sent to extrudabody to be worked over for multiport injection, any replies, please answer in general terms for I am not educated in EFI.
professional opinion needed
- Thread starter Broncitis
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'TBI/CFI which is where the injector or injectors are in the throttle body. Expense wise there is only one body and there tends to only be 1-4 injectors. Intake manifolds are pretty much the same as carbs so you save some money if no one makes a multiport intake for your motor. Performance is good but the risk is the fuel coming out of suspension as it travels around the twists and bends of the intake to the head/valve and you tend to have unequal runner length which can also affect the final AF mixture that ends up in each cylinder. A variant on this would be to use multiples on things like a dual quad or 4:2 intakes.
Multiport is where there is 1(or more) injector(s) per cylinder mounted as close as possible to the intake port of the head. Typical systems use one throttle body and better ones use a mass airflow sensor. The idea is that there is going to be less chance of the fuel coming out of suspension because the fuel is introduced as late into the path as possible. Another variant is how the injectors are timed. Some multiports were fired all at the same time, others were fired in batches. By the late 90's I think most cars are now sequential injection which means the individual injectors are timed so they dump the fuel as the valve opens. Again the theory is you are going to end up with more accurate control because less chance of the mixture to go wrong on the way in. Im not sure how individual throttle bodies would benefit unless you had individual O2 and or EGtemp sensors and the ability to trim the timing and pulse width of the individual injectors. Seems like all it would do is make for a lot of complication and fabrication. Would probably look really cool though!
Im really not sure how all this plays into boosted applications
Multiport is where there is 1(or more) injector(s) per cylinder mounted as close as possible to the intake port of the head. Typical systems use one throttle body and better ones use a mass airflow sensor. The idea is that there is going to be less chance of the fuel coming out of suspension because the fuel is introduced as late into the path as possible. Another variant is how the injectors are timed. Some multiports were fired all at the same time, others were fired in batches. By the late 90's I think most cars are now sequential injection which means the individual injectors are timed so they dump the fuel as the valve opens. Again the theory is you are going to end up with more accurate control because less chance of the mixture to go wrong on the way in. Im not sure how individual throttle bodies would benefit unless you had individual O2 and or EGtemp sensors and the ability to trim the timing and pulse width of the individual injectors. Seems like all it would do is make for a lot of complication and fabrication. Would probably look really cool though!
Im really not sure how all this plays into boosted applications
Since you sent an intake to the extrudabody folks, you must have looked on the website at the pics & videos. The individual TBs definitely look super cool.
I'm not sure that the performance difference is worth the cost though. Unless you do it for the same reasons people really put tripower setups on their rides... Coolness factor 8)
Boosting a 6 tb setup will take a big enclosure & make sealing that much more difficult. You can adapt a fox body Mustang 5 liter throttle body to the CI intake & throw a carb hat style enclosure on that a lot cheaper than the setup that extrudabody has. I would guess that it would be very close to the one they are working on for the Z car they have on the website.
I don't want to sound as if I'm dissing extrudabody... heck I even had a post on here where I pointed people in their direction. I think that they have a good product at a decent price but it can get spendy when you start buying 6 of those things along with the little widgets & sundry items that you need for a complete setup.
Do it anyway you want... just post pics
I'm not sure that the performance difference is worth the cost though. Unless you do it for the same reasons people really put tripower setups on their rides... Coolness factor 8)
Boosting a 6 tb setup will take a big enclosure & make sealing that much more difficult. You can adapt a fox body Mustang 5 liter throttle body to the CI intake & throw a carb hat style enclosure on that a lot cheaper than the setup that extrudabody has. I would guess that it would be very close to the one they are working on for the Z car they have on the website.
I don't want to sound as if I'm dissing extrudabody... heck I even had a post on here where I pointed people in their direction. I think that they have a good product at a decent price but it can get spendy when you start buying 6 of those things along with the little widgets & sundry items that you need for a complete setup.
Do it anyway you want... just post pics
The only potential advantage of multiple throttle bodies is that, if properly done, it mitigates unequal length runner issues.
Is that worth the cost and extreme extra complication of running 6 tb's? No freaking way. Not unless you are racing for a living (and even then, probably not)
And now when you add in wanting to boost it, it makes even less sense.
I would be willing to bet that the performance difference between a 6 TB setup and a single TB MPFI setup using a CI manifold is negligible.
Is that worth the cost and extreme extra complication of running 6 tb's? No freaking way. Not unless you are racing for a living (and even then, probably not)
And now when you add in wanting to boost it, it makes even less sense.
I would be willing to bet that the performance difference between a 6 TB setup and a single TB MPFI setup using a CI manifold is negligible.
Thanks guys for the info and reinforcing what I thought, at this time all extrudabody is doing for me is mounting injectors at a proper angle and installing a fuel rail, I am having injectors installed to support 250 HP, someone mentioned a 5.0 throttle body, its a serious consideration at this time, I have not made a final decision yet on the management system and just how many sensors I really want to go with, I would really like to keep it as simple as possible, there are so many out their I am having a hard time deciding, affordable fuel injection seems to have a very nice web site for a huge selection of choices and alot of info to read. The other thing I would like to mention is Kevin at Extrudabody is very very good to work with and helpfull, plus made in the USA, I really like that.
One thing to watch out for on injector size is that if you get them too big you may have idle issues. The bigger the injector the more time it takes to physically open and close. Lowering fuel pressure (variable regulator) helps but if you get to low the spray pattern is crap. Hopefully your control system will allow you the range to get them to run right. Thats one thing I like about megasquirt is there is a wide range of applications. Thats also the downside is there is a lot of adjustments you have to understand. My advice would be to get it working without the boost first so you know your mechanicals are good and you get comfortable with your control system.
The problem with too big of injectors isn't how long it takes them open/close - they all essentially have the same min pulse width.
Its that, when the injector is too big - the minimum pulse width allows too much fuel.
So what you end up with is an inability to lean the motor out enough at idle.
This is a fairly common problem with built motors.
Its that, when the injector is too big - the minimum pulse width allows too much fuel.
So what you end up with is an inability to lean the motor out enough at idle.
This is a fairly common problem with built motors.
Update, after looking at intake and aluminum head, kevin at extrudabody has decided to put the injectors in the head, better angle and stilll about 2 1/2 to 3 inches from lip of intake valve and a better shot at the valve, we are still debating throttle body, the only major decision I am 90% sure of is I am going to use retrotekspeed.com for my ecu, sensors and wiring harness, I like their price concept and ability to deal with later boost. At this time I am going to start with 24# low impedence basic bosch injectors to fall between 200 and 225 HP., My end Goal is a realistic 325 HP with about 10 to 12 intercooled boost, if I can do it with less boost I will. I will soon start looking for the best radiator out their I can use.
Small update, we are going to use an 87 to 93 chevy tbi, since the TPS and IAC are highly compatible with RETROTEKSPEED.coms EMS, it has two 44 mm butterflies and flows about 670 CFM and Kevin at Extrudabody will remove the injectors and modify it to become a stand alone TB at an exceptional price, between extrudabody and retrotekspeed it will cost me about 2200 dollars for the entire MPFI, to me its a bargain, but then again I can easily afford it . By the way, Kevin was not to excited about the manifold, but he sure likes the aluminum head and says the bosses on the head for injectors and distant to intake valve were very well thought out.
The retrotech Holley looking TBI is a cool looking setup. Is the 670 something they measured or just guessing? Holley sold a TBI with 52mm bores as an 'upgrade' to the stock GM one that they called a 670. Without knowing the pressure its a useless number anyway. I have one of the 52/670's on my Cadillac 500. At 4000 rpm (crazy fast for that application) WOT MAP is still reading ambient so I assume that means Im not restricting the flow. On a 200 that should me more than enough.
Be sure to post how getting the thing to run goes.
Be sure to post how getting the thing to run goes.
CFM thru a TB is almost irrelevant in a dry manifold. The TB simply becomes an air valve into the plenum. As long as you can control the opening rate at which airflow goes thru the TB, you could use a 1200cfm TB on a 200 with a dry flow manifold.
You don't have to worry about maintaining air velocity thru a venturi. There's no fuel mixing to be done, and no fuel dropout issues in the manifold.
You don't have to worry about maintaining air velocity thru a venturi. There's no fuel mixing to be done, and no fuel dropout issues in the manifold.
Hey thanks all of you guys, I really use your input as to if I may have missed something or may be going in a wrong direction, alot of anxiety was relieved when some of you I respect thought the GM TPI conversion was a good choice, it seemed to easy and inexpensive to be true, although Kevin at extrudabody has been a great source of knowledge and very very helpfull even when it came down to that I used very little of his product in reality, he probably did more machine work for me than anything, very nice, patient and helpfull, I wish I could send business his way. He and Mike are first class.
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