I get how the imrcs work, opening up when you need more intake, fine. And our throttle body is dual bore, which opens up the other one when you need more air too. Isnt this redundant? I would think that with the imrc's you would want a single bore (oval) throttle body wouldnt cha? Im also guessing that you could eliminate the imrc's if you want and not lose low end torque, but youd have to learn where the accelerator opens up the second bore. am i right in this assumption? also...does anyone know where i can get one of them intake extentions from the cobra that will relocate the tb ontop of the intake?
Question about TB and IMRC's
- Thread starter MrWilson
- Start date
Grifter
Well-Known LVC Member
intake extensions?
the TB is a dual bore yes, but both butterflies open at the same time. the reason behind why its a dual bore, twin 55mm butterflies flow ALOT of air. i dont know the number off hand though. that would take a big round TB to flow the same amount of air. to find out the surface area of air that would be flowing through a dual 55mm TB, heres the equation
A=Pi*R*R (Radius squared)
A=3.14159*27.5*27.5=2375.8 sqmm *2 (2 bores) = 4751.6 sqmm of surface area
thats about the same as a single 78mm TB. thats a huge TB. its much easier to fit dual 55's in that space, than a single 78mm.
the TB is a dual bore yes, but both butterflies open at the same time. the reason behind why its a dual bore, twin 55mm butterflies flow ALOT of air. i dont know the number off hand though. that would take a big round TB to flow the same amount of air. to find out the surface area of air that would be flowing through a dual 55mm TB, heres the equation
A=Pi*R*R (Radius squared)
A=3.14159*27.5*27.5=2375.8 sqmm *2 (2 bores) = 4751.6 sqmm of surface area
thats about the same as a single 78mm TB. thats a huge TB. its much easier to fit dual 55's in that space, than a single 78mm.
Grifter said:
Oooooh - Math - Ick
Grifter said:
no offence but thats not true. Go take off the intake tube and play with the throttle connection. you will see that at about 1/2 throttle is where the second bore opens up.(its like a secondary on a carb) The reason its dual bore as opposed to one massive oval is for the intake air velosity. the air moves in faster through two ports rather than one. but if your looking for massive ammounts of air imo the oval would be the way to go, otherwise it seems a little redundant to have the dual bore and the imrcs? maybe im wrong, but thats my oppinion.
94m5
Dmaup's Daddy
on a gen 1 VIII, yes it is progressive. On gen 2s it's not.
I think It has something to do with port velocity at low RPM's
I think It has something to do with port velocity at low RPM's
Grifter
Well-Known LVC Member
REALLY? wow. that makes no sense at all!
i guess they got it right on gen2's
what were you talking about an intake extension?
i guess they got it right on gen2's
what were you talking about an intake extension?
That is a way of controlling the velocity of air on the gen 1. The gen 1 intake manifold also has a lot more runners than the gen 2. To control velocity of air on the gen 2 they gave it the real dual throttle body setup that opens at the same time but less intake runners.
94m5 said:
isnt that also the idea of imrc's? redundancy?
Grifter said:
i remember back a year or two, i saw that you could buy the part ( i dont know what its called) that connects the intake manifold to the throttle body...but not directly like it does stock. let me try to find it again.
yea..heres a pic.
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Grifter
Well-Known LVC Member
isnt that a Bullit intake? thats a 2v intake, but i'd be curious to see if you could make it fit a gen1 intake. i dont know what gains that would have, but it would simplify the cold air intake situation for you guys.
Yes, that's a bullitt intake for a 2V. I don't believe the two are compatible.
IMRC's exist to improve low end torque by increasing the length of the runner. Longer runners = more torque. Shorter runners = more top-end horsepower. With IMRC's, you effectively can turn a long-runner intake into a short runner intake at WOT in order to more effectively match intake runner design to the intended usage at that moment in time.
I didn't know Gen I cars had progressive TBs - that's wierd.
IMRC's exist to improve low end torque by increasing the length of the runner. Longer runners = more torque. Shorter runners = more top-end horsepower. With IMRC's, you effectively can turn a long-runner intake into a short runner intake at WOT in order to more effectively match intake runner design to the intended usage at that moment in time.
I didn't know Gen I cars had progressive TBs - that's wierd.
Dr. Paul said:
no offence paul, but how exactly does closing the imrcs turn the runners from short to long. I realy dont know, but in my logical thinking it doesnt seem to do either or. As it looks to me...There is a runner for each intake valve. With the imrc's "closed" your getting air through only one of the valves (i dont know what the heads look like, and its prolly like any other head on the intake side(4 ports not8), and im prolly 100% wrong, but this is what im thinking.) and then when the imrcs open, your just getting more air. And even if its 4 bores on the head, it would do pritty much the same thing (giving more air) it would just be like taking that bore and porting it out instantaniously, would it not? IDK, it could just be my immagination, but thats how i see it.
Dr. Paul said:
i know thats for a 2v, but i remember seeing one for the 4v'r somewhere along the line. thats just a pic of what im talkin bout.
02LSE96LSC91SE84TC
Dedicated LVC Member
GenIs are definately proggressive, it is strange. The secondary doesn't even appear to open fully. It is opening opposed to the direction of air which strikes me as odd too. Is there something that can be done to improve it? Would it be worth the bother?
02LSE96LSC91SE84TC
Dedicated LVC Member
Would have to see a GenII, but I'm willing to bet the throttle cable would need to be modded. Thats not exactly hard. Still wonder if it would make much difference. Probably in throttle response but not WOT. Then again if the blade were turned 90degrees, it should make it alot easier for air to flow in. Hmmm. Has anyone ever bothered messing with a GenI TB at all? The GenII has a different style intake yet same hp. Back to the original question, Is it worth it?....
02LSE96LSC91SE84TC
Dedicated LVC Member
Its probably one of those, to little increase of power to try it things, it can't say if I agree or not. Got me thinking, cars in the garage partially apart now anyways. I'm going to go drink a beer and stare at it.
MrWilson said:
There is no offense taken. The opening/closing of the IMRC (or similar variable intake geometry device) changes/restricts the path that the air must travel before reaching the cylinder head intake port. There is not a runner for each intake valve, there are only four intake ports just like other V8 heads.
Airflow velocity affects low-speed and off-idle torque characteristics. Velocity can be controlled with runner design, and many other factors that make up the volumetric efficiency of the motor. Variable intake designs, such as those implemented by Ford with their modular motors are just a way to compromise between all-out performance, and appropriate daily driver manners.
Paul.
Dr. Paul said:There is no offense taken. The opening/closing of the IMRC (or similar variable intake geometry device) changes/restricts the path that the air must travel before reaching the cylinder head intake port. There is not a runner for each intake valve, there are only four intake ports just like other V8 heads.
Airflow velocity affects low-speed and off-idle torque characteristics. Velocity can be controlled with runner design, and many other factors that make up the volumetric efficiency of the motor. Variable intake designs, such as those implemented by Ford with their modular motors are just a way to compromise between all-out performance, and appropriate daily driver manners.
Paul.
i see why you like pushrods so much
i prolly knew that, but just being on the slow side tonight. Thanks paul.
JC1994
Dedicated LVC Member
Hell ya....:I :IJoeychgo said:
02LSE96LSC91SE84TC
Dedicated LVC Member
Those aren't the MarkVIII heads. They are divided right to the valve. Thats a later model head.
Dr. Paul said:
while i do truly appriciate OHV>OHC, and i also believe that...i do think that OHCs have much more potential, the problem is their potential is not for the every day hot rodder, unfortunatly.
94m5
Dmaup's Daddy
yup, thats a C, Head
Marks use B
Marks use B