ITB SETUP

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Originally Posted by A20A1

I'm confused though... why do they switch from MAP to TPS on ITB's?
I don't see how TPS can sense load.

once the manifold vacuum drops to 0 and you're running off the venturi signal.

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With the "alpha n" or whatever, the tps doesn't sense load, it tells the ecu what load it is. With an x y graph of tps vs rpm, there will only be one manifold absolute pressure for every intersect point. So the ecu knows the map press for every load point, if it is tuned properly. So why do they use the map sensor instead? i'm guessing more accuracy..

As far as your question about what when the vacuum is all gone, what? The map measures in absolute press.

And with carbed motors, the Only time the pressure difference across the carb, not velocity, directly acts on fueling is when the choke is closed. The throttle is behind/below the venturi. What meters fuel in a carb is that with airflow, pressure and velocity are inversely proportional. The more velocity through the venturi, the more press difference across the booster/whatever that little thing is called, and the more the fuel gets pulled out.

Yeah at WOT the mani vac is 0 and you're running on the primaries and secondaries. Vs when the throttle is closed and you have manifold vacuum working the idle.

So the absolute pressure is different then say the 0 mark on a vac gauge?

i had myself completely talked out of ITB's just for pure driveability factors. If you can pull this off (jigga) and maintain total driveability (which is totally doable, you are going to run a vacuum resevoir arent you?) my kudos go to you. You most certainly have the unique thing down man.


Pushin whips like i wouldn't believe man!

Ok... accordtheory i just want to mention one bit of information in your post that i completely disagree with. You say that ITBs are not a performance gain. If thats true then why does every fast NA motor run them. Think about it F1, bike motors, BMW M motors.

As far as the switch to TPS... as far as i know its becuase you can get extremely accurate tuning with that. However, it then becomes like a carbed motor and is very weather sensative. That is why most street vehicles use MAP or MAF or some such way to measure the air flow or pressure because then the tune changes much less with weather changes

I want to see how well this works mostly because it is different. I bet it won't work very well but that's ok, it's an experiment right?

The ITB vs single plenum debate is not over. Check this guy out...

http://cgi.ebay.com/ebaymotors/SR20D...QQcmdZViewItem

It's essentially a set of very short ITBs with a large single plenum and throttle body. I've read all that stuff on H-T about single plenums vs ITBs, interesting stuff. Part of the problem with ITBs and the A20 is that you need really long runners to do it properly. I did the calcs once and came up with like 17-18" for 7000RPM redline. Which means that the trumpets will be very close to the firewall. I still might try to put some together this summer if I get motivated enough. Also with runners this long you need large throttle bodies that are positioned a good ways from the head. Going by the numbers, 45mm throttle bodies are barely large enough. 50mm would be better. This is going by the rules of thumb though, so no idea of this would actually work for real.

The lumpy MAP signal can be handled with an accumulator tapped from each of the runners. Sized correctly it should provide a decent signal although the stock ECU will probably throw a fit. A decent aftermarket ECU would handle it. Add a radical cam though and you get into alpha-n territory (TPS based fuel control).
A note about alpha-n, it's not as accurate as MAP sensing because it doesn't sense actual engine load, but assumes that a given throttle position at a given RPM will equate to some amount of air intake into the cylinders. Thereby requiring a certain amount of fuel. With a high power output engine, accuracy generally isn't as critical, especially if it's usually running full out.


MAP or Manifold Absolute Pressure is just another way to measure pressure that doesn't rely on the atmospheric pressure for reference. A MAP of 0 means no pressure or complete vacuum. Standard atmospheric pressure is approximately 14.7 PSI or 100kPa MAP. It's the same idea as the Kelvin scale for temperature.

C|

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Originally Posted by A20A1

Yeah at WOT the mani vac is 0 and you're running on the primaries and secondaries. Vs when the throttle is closed and you have manifold vacuum working the idle.

So the absolute pressure is different then say the 0 mark on a vac gauge?

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About the idle thing, I forgot about that. However, is more it the diff in press across the throttle blade that makes that work, or the high velocity past the edge of the blade creating a low pressure area? Probably both, I don't know.

I don't really understand your question about absolute pressure.. But any time air is present, it has pressure. Atmospheric press is 14.7 psi at sea level, the oem honda map sensor can measure from 0 to about 24.7psi absolute (10lbs of boost).

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Originally Posted by Zufer

Ok... accordtheory i just want to mention one bit of information in your post that i completely disagree with. You say that ITBs are not a performance gain. If thats true then why does every fast NA motor run them. Think about it F1, bike motors, BMW M motors.

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Well, there you go, you just won the argument. Come on, you really think it's that simple?

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Originally Posted by cygnus x-1

I want to see how well this works mostly because it is different. I bet it won't work very well but that's ok, it's an experiment right?

The ITB vs single plenum debate is not over. Check this guy out...

http://cgi.ebay.com/ebaymotors/SR20D...QQcmdZViewItem

It's essentially a set of very short ITBs with a large single plenum and throttle body. I've read all that stuff on H-T about single plenums vs ITBs, interesting stuff. Part of the problem with ITBs and the A20 is that you need really long runners to do it properly. I did the calcs once and came up with like 17-18" for 7000RPM redline. Which means that the trumpets will be very close to the firewall. I still might try to put some together this summer if I get motivated enough. Also with runners this long you need large throttle bodies that are positioned a good ways from the head. Going by the numbers, 45mm throttle bodies are barely large enough. 50mm would be better. This is going by the rules of thumb though, so no idea of this would actually work for real.

The lumpy MAP signal can be handled with an accumulator tapped from each of the runners. Sized correctly it should provide a decent signal although the stock ECU will probably throw a fit. A decent aftermarket ECU would handle it. Add a radical cam though and you get into alpha-n territory (TPS based fuel control).
A note about alpha-n, it's not as accurate as MAP sensing because it doesn't sense actual engine load, but assumes that a given throttle position at a given RPM will equate to some amount of air intake into the cylinders. Thereby requiring a certain amount of fuel. With a high power output engine, accuracy generally isn't as critical, especially if it's usually running full out.


MAP or Manifold Absolute Pressure is just another way to measure pressure that doesn't rely on the atmospheric pressure for reference. A MAP of 0 means no pressure or complete vacuum. Standard atmospheric pressure is approximately 14.7 PSI or 100kPa MAP. It's the same idea as the Kelvin scale for temperature.

C|

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I don't have time at the moment to get into the benifits of ITB's, and especially the physics of it all.. That will come later..
I just have to clearify that the intake mani you posted is no where near ITB's the only thing it has incommon is the velocity stacks and it's an intake...
Itb's are called so because they have individual butterflies/ throttle bodies..

If you do the calculations but change it for the second or third pulse or something like that then you get shorter runners. I forget but I posted a link to intake mani design and it shows a work around to the long runner problem.

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Originally Posted by A20A1

If you do the calculations but change it for the second or third pulse or something like that then you get shorter runners. I forget but I posted a link to intake mani design and it shows a work around to the long runner problem.

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Yes. As you increase the order of harmonics the length decreases, but so does the strength of the reflected wave. Here is a runner length calculator:

http://www.bgsoflex.com/intakeln.html

With an 18" runner length you get the following:

# Input length is 18 inches
# For 2nd harmonic, RPM range is from 6527 to 7920 with a pulse strength of 10 percent
# For 3rd harmonic, RPM range is from 4904 to 5604 with a pulse strength of 7 percent
# For 4th harmonic, RPM range is from 3823 to 4276 with a pulse strength of 4 percent


Actually for a 7000RPM redline a little longer might be better.


C|

Accordtheory... i don't think its that simple.. in fact i know its very difficult to get it all to run right. However, i do think that there is a lot to be gained power wise with ITBs. Maybe they aren't any better for peak power but you would be hard pressed to get such a flat torque curve without them.

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Originally Posted by jigga89SEi

I don't have time at the moment to get into the benifits of ITB's, and especially the physics of it all.. That will come later..
I just have to clearify that the intake mani you posted is no where near ITB's the only thing it has incommon is the velocity stacks and it's an intake...
Itb's are called so because they have individual butterflies/ throttle bodies..

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Yes, I understand that, and I wasn't saying that that intake IS an ITB setup, but that it's similar. The important aspect of ITBs is the straight, tapered, tuned length runner; e.g. the velocity stacks. This is what creates the reflected wave. Of course with that ebay manifold there is a huge plenum so the throttle response won't be as quick as a true ITB. The common plenum though creates additional opportunities for wave reflection, so tuning is not as simple as just runner length.

Anyway, my point was only that there is still much research going on with intake design. And that ITBs are not necessarily the final word in high performance. I am by no means an expert in this area.

C|

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Originally Posted by Accordtheory

Well, there you go, you just won the argument. Come on, you really think it's that simple?

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im going to agree to disagree with both of you. I dont see very many N/A Drag cars running them, mostly because you dont gain THAT much. You see them in M motors, bike motors, and F1 cars because of the throttle response, plain and simple. After sharp deceleration (in F1) they want to be able to hammer it and get right back up to speed. You dont see it in drag cars because you dont need throttle response (a lot of it anyway...)

But i do agree somewhat with Zufer, you do see an increase in horsepower with ITB's, but alot of that has to do with the removal of all restrictions in the intake system.

I agree ITBs are very good for throttle bodies. I also did state that i don't think there would be much gained for peak power. However. There is a lot to be gained for the rest of the powerband.

Like you say... for drag racing this doesn't do a whole lot. But i doubt anyone on here is building a legitamete NA drag car out of a A20... except maybe rjudgey. But he is running carbs still i believe. As far as jigga's setup. It may not be optimal... but i bet it will make a big difference in flattening the torque curve. Oh and i fail to see how it isn't ITB's... It has 4 runner, and four throttle plates. It just isn't straight like most setups.

the formula fpr throttle body size is complicated
revs times capacity divided by something else to find the cfm your motor need s.
the simple way is for power you want short runners of a large diameter
if you want a motor that makes good torque thru the bottom end and mid range a medium lenght and diameter runner as in factory size is good and allows scope for mild mods
if a bottom end monster is what you want go for long narrow runners.
this is more a biased towards carbs but at end of day its all about air speed in the port and across the valve
i want power so going for 45mm itb

I'm not saying in any way itb's are better then a regular intake set-up.. You could easily get more power out of a good intake mani and correct sized throttle body..
I don't remember the measurements at the moment, but the itb's are a huge differents over the stock size tb, and even bigger then most aftermarket..
But the throttle response will be so much greater then that of a single itb, whiich will serve the purpose the car is being built, road racing, and handling, possible even to be seen doin gymkhana..

I'll get back with more later...

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Originally Posted by Zufer

As far as jigga's setup. It may not be optimal... but i bet it will make a big difference in flattening the torque curve. Oh and i fail to see how it isn't ITB's... It has 4 runner, and four throttle plates. It just isn't straight like most setups.

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Hmm. My hunch is that the torque curve will be anything but flat :lol: but I guess we'll find out sooner or later.

And Jigga's setup IS an ITB. The ebay link I posted is NOT an ITB.

Anyway, this is Jigga's thread so I'll stop spamming it up with the ITB vs single plenum debate. We already have a thread for that elsewhere. :D

C|

if any thing, once its all set up and tuned he'll gain a bit from the mid range up to the limiter without any tailing off due to inlet restriction.
as long as the exhaust can keep up with the extra gases it'll work fine
the first thing to change is the exhaust first and then work on the inlet once you run out of air flow.
but since he's already made the quad throttles the next step would be cams to use the xtra availible air.
i learned at tech college doin a pre trade how to check inlet restriction and what the limit is.
hook up a vacum gauge before the butterfly and one after and take a full throttle full load reading of each gauge
if you have more than 3 inchs hg drop across the throttles you need a bigger throttle set up
but seeing that the secondary butterflies on a b20a are about 45mm i dont see him running out of air flow there.

looks great bro

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Originally Posted by jigga89SEi

I'm not saying in any way itb's are better then a regular intake set-up.. You could easily get more power out of a good intake mani and correct sized throttle body..

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What the hell...? I actually laughed out loud when I read that. You're the one doing it and you say this? Well, good luck with your setup, anyway.

way to take a quote out of context. He later mentions that the throttle response will be much better which is what he is after.

I didn't take anything out of context. I just said it made me laugh that he'd say that. and it still does.
here's a link to a dude selling his TWM's, read why..for some reason I find this amusing also. He must not have had it tuned very well..or something.http://cgi.ebay.com/ebaymotors/TWM-I...spagenameZWDVW

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Originally Posted by Accordtheory

What the hell...? I actually laughed out loud when I read that. You're the one doing it and you say this? Well, good luck with your setup, anyway.

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whats wrong with that...il slap on my skunk 2 mani and 68mm tb and il dyno it right after and see if i get any improvement....better than my stock manifold

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Originally Posted by Accordtheory

I didn't take anything out of context. I just said it made me laugh that he'd say that. and it still does.
here's a link to a dude selling his TWM's, read why..for some reason I find this amusing also. He must not have had it tuned very well..or something.http://cgi.ebay.com/ebaymotors/TWM-I...spagenameZWDVW

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Well for starters.. I'm not goin after the fastest or highest hp accord... Wicked killed that with his swap... I'll have that title later tho, :naughty: (hoptfully), with something the likes of 3geez has never seen.. But that project is still classified TS, Eyes Only.. Anywayz.. From the get go starting with the A20, I already new even with all the money I could through at it.. It still wouldn't be "amazing".. So why try?.. I want it to make people go wow.. Our cars, when hooked up do that anyway.. But I want to be unique...
As far as that kids explaination for gettin ride of those ITB's, that makes me laugh..

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I had this mounted on a Honda B16 Engine. The filter shown will just clear the firewall in an EG Civic. The injectors in the setup are the ones it had in it when I got it. I'm not sure exactly sure what they are. The RC 310's I was running are still in my car. I used a Honda S300 to tune the setup. In my opinion, this is good for a drag racing setup, but no so good for a road race setup (which is what I am doing now) (1) so I switched back to a more conventional setup and am selling this one. They look awesome on an engine and make lots of top end power on the dyno. (2)
Sold as is with no known problems. Everything included is shown in the pictures.

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(1)You want mid to top end for road racing, why would you let your rpms fall below 3000? ITB's are virtually useless at low rpms, Your not tuning for power at low rpms, you tuning to reduce bog.. A big difference.. Why would you want ITB's in a 1/4 mile drag? 1/2 maybe.. But it can be related to turbo lag, you have to wait, but the itb's will still not make as much hp as a turbo.. Therefore, IMO, the only reason to use ITB's for drag is to sound really fucking cool when you WOT going down the stretch..

(2) He said it himself, high end.. Proper tuning would change that from mid to high end.. Either he was new to racing, or he thinks more horse power is whats gonna win his races..

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Originally Posted by MessyHonda

whats wrong with that...il slap on my skunk 2 mani and 68mm tb and il dyno it right after and see if i get any improvement....better than my stock manifold

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Uhh..maybe you missed my point? I was just saying, he's the one doing it, and he's not blindly 100% positive on all fronts, like most people probably would be.