OK, so why do the IDF Throttle Bodies work so good?

[drmiller101]

anyone can throw any set of idf's on any air cooled engine, and have it run danged good.

You are saying everyone needs to build and tune and tinker and do a bunch of math stuff to build a bunch of plenums and runners, and then you SHOULD be able to duplicate, or possibly increase performance compared to the thrown on IDF's.

My question was has anyone EVER built a 2100 ish cc engine with plenum or single carb which can duplicate peak horsepower of the thrown on IDF's.

the answer is NO. IDF's make more peak horsepower then any single TB or carb system with plenum or runners.

[SUbuggy]

ok.

has ANYONE built a 2180 with 150 plus horsepower with a single TB using ANY plenum?????

I am talking about a type 1 engine, air cooled, no nitrous, no turbo, NA.

thanks.

while not a 2180, i have a 2332 NA that is a single TB plenum that put down 155hp TO THE WHEELS, as measurd on a dyno dynamics dyno. i specifically mention the dyno by brand because the DD chassis dyno is well known for being "stingy" with their HP calculations. given a 15% drive train loss, than you are in the ballpark of 180+hp.

[1955cc66bug]

ok.

has ANYONE built a 2180 with 150 plus horsepower with a single TB using ANY plenum?????

I am talking about a type 1 engine, air cooled, no nitrous, no turbo, NA.

thanks.

while not a 2180, i have a 2332 NA that is a single TB plenum that put down 155hp TO THE WHEELS, as measurd on a dyno dynamics dyno. i specifically mention the dyno by brand because the DD chassis dyno is well known for being "stingy" with their HP calculations. given a 15% drive train loss, than you are in the ballpark of 180+hp.

Sweet! Care to give out the specs on the system?

[Paul H]

There are quite a few reasons why major car manufacturers use plenum/runner manifolds
nothing to do with power,economy,driveability
1 Noise-they are quieter for sure

that only depends on the application.

No actually they are are all quieter due to the sealed nature of the system with only one TB outlet.
The same on a ITB setup would require a complex air box with complex attachment system


2 Packaging - getting it all neatly into the engine compartment

actually not true either. many of the runner systems purposely have to either (a) compromised in exact volumes and length and (b) made even more complex and expensive with S-patterns cast in to get proper operation. Twin banks of ITB's would be far cheaper and easier to stuff under the hood than a very complex plenum.

Actually yes you are correct it probably would be just as easy to get a single bank of ITBs in the same space with a similar sized complex air box but No it certainly wouldn't be cheaper and it certainly wouldn't be easier-As far as expense goes the more complex intake would only be a few more hours for the designer and the toolmaker so negligable extra cost for the OEM-assembling a multi throttle sytem into a sub assembly is another job in it's self with a LOT more parts


3 Assemblability- bolting a sub assembly to the engine in a production line

It makes no significant difference either way. A jig would be built...and the engiens are made on a sperate assembly line anyway.

True so long as you ignore the other extra production line assembling the multi throttle sub assembly

4 Less moving parts with 1 throttle and no fancy linkages or couplings
to deal with
This is not even close to being true half the time. Typically TB's on plenum systems usually end up in very disadvantageous places due to having to stay out of the way of the runners and or becauuse of engine position. Not to mention, that TB's with plenum systems are usually more complex because of the need to plumb into them...IAC, many more vacuum ports than are necessary with multiple TB's and more ancillary systems. Spend some time in the junkyards looking at a vasy range of plenum system TB's and you will find that most are much more complex than what few ITB's are out there. Plus...most have an air straightner insert...almost are are tuned in size specifically to the engine application they go on. This many times also requires an adaptor piece or an insert to be pressed in if a universal TB body is to be used on a family of cars.

Uh ! Lets look at the LS1 intake versus an aftermarket multithrottle -8 throttle plates,8 spindles,16 throttle plate screws 16 spindle bushes,linkage parts etc etc basically 8 times the compononets-idle valve ! = 8 vac ports and associated plumbing. All the single throttle bodies I saw on modern engines seem very accessible
with some of the complexities coming down to emmision control equipment that would be very difficult to implement on a multi throttle system

The two pics below pretty much sum up the whole cost/packaging/assembly/complexity v performance arguement.Top pic is a ITB set up for the LS1 and the bottom is the factory style injection moulded version $1000 v $100.You'd need to make an airbox for the TWM to bring noise levels down and I doubt it's then fit under the hood plus it'd probably take 1 man the best part of a day to assemble it.But hey what's the point of making that work of art when the plastic OEM performs better



5 Throttle resolution better at low speeds
Very true....and its also true that throttle resolution is better at a wider range of rpm and power bands than ITBS. This also requires VAST amounts of tuning and testing to accomplish. It aint cheap.

OEMs go to great lengths designing throttle body walls,adding vanes on to plates variable rate linkages etc to acheive this so are definately better and as most cars are driven at below 20% throttle for most of their miles it makes sense to work in this area but it certainly doesn't help with power.With correctly sized ITBs and manifolds there would be no noticeable difference above 20% throttle

6 Easier intake air routing and filtration

Not even remotely simpler. Take a closer look at a large number of plenum systems. What looks easier to the quick glance...usually requires several peices of injection molded ducting and a totally different sheet metal pressing to be welded into a car getting a plenum system. Not to mention the vacuum control devices for that ducting, clamp systems etc.
Same goes for a ITB system with the afore mentioned complicated air box and attachment system for split banks of ITBs double everything up
7 One peice combined manifold single TB is very cheap to produce once tooling is paid

Once you take a look at most plenums...and havee a bit of experience in the casting and molding industry....youwill find that to be 100% incorrect. Most complex multi-cylinder plenums require seriosuly complex multi-part casting molds. These can have in some cases ...almost as many parts as an engine block cast. Pick one up sometime...and I'll be happy to outline the seperate mold parts....both internal and external. every so many parts, the intire interior mold set of said master mold must be re-surfaced. Most ITB type most are a simple two part mold with finish CNC milling. Plenums cannot be done this way. The CNC systems cannot reach inside.

I know a bit about casting and the tooling is very complicated but once done they only have 1 part to put in the CNC with only a few ops so overall it works out a lot cheaper.Modern core tech would mean perfectly acceptable finish inside

It's all about the strict emmision control-multi throttles are a nightmare


Agreed ...multi throttle systems are very hard to control. But plenum systems have been around...purposely......for performance reasons...long before a single person on this planet cared about emmission. They were used on aircraft to make HP long before cars. The fact that they can produce better emmissions (in specific cases)...is only part of the picture. Virtually every high HP luxury gas guzzler out there uses a plenum system....go figure!

That's right even the gas guzzlers need to pass emmisions and after all they are only like 2 econo engines rolled into 1 and they are made by the same OEMs cutting the same production costs-BMW I think have a recent engine with ITBs maybe they did it for laughs or maybe they decided the plenum system wasn't up for job and didn't care about the extra production costs

These will be first and foremost in the manufacturers minds after which they can tweak it to give
best results in the power department.If they weren't bound by these contraints and they put the same
amount of R+D into a ITB system there would be big improvements in the power department
Back on to VW and the P/R they produced-it's all about packaging

Same goes for plenums systems on ACVW. There have been no factory R&D into flat engine plenum systems since 1976....save for Subaru...and the yare using a plenum system to GREAT effect!
They ain't that great and the old Alpha fitted with 36 IDF's was certainly a nice car to drive and the injection ITB version was even nicer


Type 4 engine lid,vanagon engine lid,type 3 engine lid-didn't have much choice really did they

Totally untrue....in the 411/412/ two and four door....TWO entire upright type one systems could be used under either of their hoods. The same could have easily been done with a type 3....just like the type 4....which simply opted to ditch the back luggage area and make a storage behind the back seat.
They had room to use any intake system in the world on these cars and they opted for plenum type. The vanagon and busses are the same. There are no constraints for intake space on any of these vehicles...save for the type 3 and 4 station wagon variants.

Not that familiar with the 411 as they were all scrapped over here but getting dual IDFs in a type 3 requires some horrible squat manifolds and short filters.
Vanagons with WB engine you won't get IDFs in there with modding the engine lid. Most of the T4 engined buses over here had dual solexes most of the injection plenum stuff went to USA for the stricter emmisions

ITB's are way way more tunable than any plenum system and can be tuned anyway you want
either maximum top end power,maximum torque,maximum mpg or a compromise of all.

They are NOT more tunable at all....they are just easier and cheaper to tune. Big difference. And still....everything uses plenums.

Tune them
just the same with runner length,runner volume,throttle size,throttle plate position,ram pipe length etc
the sky is the limit and the sky is your plenum

This is just as true with plenum systems as it is with ITB's....excpet there are effects and benefits from a properly designed plenum that you cannot get with ITB's....which is why ITB's are not as flexible over as wide of a range of RPM.

And the reality is there are no plenum sytems available for reasons discussed before and as all the runners need to meet at the plenum it would
be virtually immpossible to make and optimise the system with these contraints and engine bay contraints combined.The only advantage of a long runner system
is creating smooth throttle response just off idle up to 2000rpm after which a correctly tuned ITB set up would dump all over it

The only thing holding you back is same as the PR system which is lack of variety in the parts availabilty
as the generic IDF pattern 48mm manifolds is about your lot-you got a choice of straight or offset

And the same issues hold you back with availability of plenum systems for ACVW.

But not in my world

So to sum things up IMO the plenum system obviously can be made to work well but most of the reasoning behind it is nothing to do with
performance.The availabilty of $10 throttle bodies in junkyards will always attract the hobbyist but lets not confuse better with cheaper.
Any further discussion on this subject needs to be backed up with some hardcore dyno results and real world examples way too much theory
that can't be backed up here and since the P/R system can only realistically be applied to aircooled motors that don't have upright cooling not sure
why the subject gets so much air time
Cheers
Paul

[Paul H]

ok.

has ANYONE built a 2180 with 150 plus horsepower with a single TB using ANY plenum?????

I am talking about a type 1 engine, air cooled, no nitrous, no turbo, NA.

thanks.

while not a 2180, i have a 2332 NA that is a single TB plenum that put down 155hp TO THE WHEELS, as measurd on a dyno dynamics dyno. i specifically mention the dyno by brand because the DD chassis dyno is well known for being "stingy" with their HP calculations. given a 15% drive train loss, than you are in the ballpark of 180+hp.

I'd like to see the power/torque graph on that as I have a DD. Was it with or without fan belt?

[miniman82]

My question was has anyone EVER built a 2100 ish cc engine with plenum or single carb which can duplicate peak horsepower of the thrown on IDF's.

Does the average VW owner have the drive, enthusiasm and intelligence to carry out such a system? No. Most VW people only care about looks, they could care less about actual real world perfomance. Besides the fact that IDF style carbs on a flat 4 engine are practically a steroetype in VW circles, it's no wonder no one is putting any effort at all into a properly designed plenum system (factory aside). My feeling is if you personally do not take the time to develop something, you ought not to wonder why no one else has. Other's reasons are likely the same as your own.

Any further discussion on this subject needs to be backed up with some hardcore dyno results and real world examples, way too much theory that can't be backed up here

So 'the debate is over' because you say so? Who are you, Al Gore? What there is here, is SOUND theory. This isn't just a bunch of people saying 'oh, I think it would work tits man, try it out!' While I disagree with Ray on some issues, he's spot on here and you should listen. BTW, I have a dyno sheet so I'm qualified to talk about this.

since the P/R system can only realistically be applied to aircooled motors that don't have upright cooling not sure why the subject gets so much air time

I see... So I guess the VW engineers were quite dense in thinking they could make a single TB and upright cooling work?

That's strange, because THEY DID it 2 times! There's the German intake, and the Mexican one.

Also, I'm not the only one who's done a plenum system, but I didn't do it for performance reasons- for simplicity. There's simply less things there with a single TB: no linkage, less pipes, less crap cluttering the bay up. In the long run, it's a lot less hassle than those PITA dual TB's. granted I have a turbo, but I'm with Ray on this one- a well thought out plenum system will get very close to the output of an ITB system, all it takes is development.

[Paul H]

My question was has anyone EVER built a 2100 ish cc engine with plenum or single carb which can duplicate peak horsepower of the thrown on IDF's.

Does the average VW owner have the drive, enthusiasm and intelligence to carry out such a system? No. Most VW people only care about looks, they could care less about actual real world perfomance. Besides the fact that IDF style carbs on a flat 4 engine are practically a steroetype in VW circles, it's no wonder no one is putting any effort at all into a properly designed plenum system (factory aside). My feeling is if you personally do not take the time to develop something, you ought not to wonder why no one else has. Other's reasons are likely the same as your own.

Any further discussion on this subject needs to be backed up with some hardcore dyno results and real world examples, way too much theory that can't be backed up here

So 'the debate is over' because you say so? Who are you, Al Gore? What there is here, is SOUND theory. This isn't just a bunch of people saying 'oh, I think it would work tits man, try it out!' While I disagree with Ray on some issues, he's spot on here and you should listen. BTW, I have a dyno sheet so I'm qualified to talk about this.

since the P/R system can only realistically be applied to aircooled motors that don't have upright cooling not sure why the subject gets so much air time

I see... So I guess the VW engineers were quite dense in thinking they could make a single TB and upright cooling work?

That's strange, because THEY DID it 2 times! There's the German intake, and the Mexican one.

Also, I'm not the only one who's done a plenum system, but I didn't do it for performance reasons- for simplicity. There's simply less things there with a single TB: no linkage, less pipes, less crap cluttering the bay up. In the long run, it's a lot less hassle than those PITA dual TB's. granted I have a turbo, but I'm with Ray on this one- a well thought out plenum system will get very close to the output of an ITB system, all it takes is development.

How about you show us your dyno results
on your engine plenum v ITB's
VW made systems for 50hp stockers
You made your system because it was cheap as usual so lets not confuse cheap with good

OH care to pass your opinion on the LS1 intakes above ?

[miniman82]

How about you show us your dyno results on your engine plenum v ITB's

It would likely make the same power, because it's turbo. Without the turbo, it's not gonna matter what intake system you put on it, because the 7.3:1 compression it has will stop power production long before a shortcoming in the intake tract will.

VW made systems for 50hp stockers

True, but that doesn't seem to be stopping people from making huge numbers...

Just because something comes from a 50hp engine, doesn't mean it's not suited to more power production. By that logic, there should be no way the ignition system from a 75hp Ford Escort can do duty on a 175hp turbo VW engine, but it certainly does- on my engine.

You made your system because it was cheap as usual so lets not confuse cheap with good.

Ooo, burn.

I already told you why I did what I did, so stop putting words in my mouth. Simplicity, nothing more. If I wanted cheap, I'd have drilled the stock end castings for injectors instead of buying injection parts from CB Performance.

OH care to pass your opinion on the LS1 intakes above ?

No, this is a VW site.

[Paul H]

How about you show us your dyno results on your engine plenum v ITB's

It would likely make the same power, because it's turbo. Without the turbo, it's not gonna matter what intake system you put on it, because the 7.3:1 compression it has will stop power production long before a shortcoming in the intake tract will.

Undocumented BS

VW made systems for 50hp stockers

True, but that doesn't seem to be stopping people from making huge numbers...

Undocumented BS

Just because something comes from a 50hp engine, doesn't mean it's not suited to more power production. By that logic, there should be no way the ignition system from a 75hp Ford Escort can do duty on a 175hp turbo VW engine, but it certainly does- on my engine.
What's that got to do with anything

You made your system because it was cheap as usual so lets not confuse cheap with good.

Ooo, burn.

I already told you why I did what I did, so stop putting words in my mouth. Simplicity, nothing more. If I wanted cheap, I'd have drilled the stock end castings for injectors instead of buying injection parts from CB Performance.

Whatever

OH care to pass your opinion on the LS1 intakes above ?

No, this is a VW site.

Thought you might pass on that one

[miniman82]

True, but that doesn't seem to be stopping people from making huge numbers...

Undocumented BS

OK fine, go ask turbo Bob, Mario, Minami, Chip, and all those other people ON THIS SITE! Don't take my word for it.

Whatever

No, not whatever. I don't have much money, that's a fact. Wanna change that? Tell Congress to give the Armed Forces more than the piddly inflation adjustment we normally get. Wanna get butthurt about my cheap ass correcting you? Not my problem.

Thought you might pass on that one

I will. And when you care to debate this subject as it relates to the VW engine (not a V8) again vice being childish, I'll be back.

[raygreenwood]

Uh...dude...the LS-1 plenum? is NOT $100. Some were plastic and the plastic contained in it is about $10...sure. Many depending on which model...were cast aluminum. Still...only about $50-60 worth of aluminum. That does not include inserts and TB....or development and mold costs.
A mold like that plenum costs (just to make the mold)...somewhere north of $1 million dollars for a "family" type injection mold if its plastic....with several parts up , about 1/2 or 3/4 of that cost if its a metal casting mold. Thats for the mold only. this does not include development modleing, testing, dyno work, computer modeling and track work. It would not be uncommon to have about $10 million invested in a part like that. Without labor costs...that actually brings the part down to about $40 a manifold without TB. But...it take $10 million out front. By the way...they made about 250,00 Ls-1's between 1999 and about 2005.

Conversely, they will probably build only about 2,000 to 5,000 of those ITB intakes. They are an ancient design...the same as pretty much used on anything from D-type jaguars to shelby cobras and mustangs. Nothing under the TB's requires any real design or airflow work. Small spaces with no runners. The base under the TB's can (and probably is) cast from a single ablative polyester core sand cast (dirt cheap) CNC finished (cheap) with a universal TB (made in a family mold cast and CNC finished cheap). Still...all in all quite expensive. Right?

But...if they had deemed that ITB's would be the way to go for better all around..... anything..... on those same 250,000+ cars....the base and TB shells would have been cast in one family mold (probably sand and polyester). That mold system is far less complicated than the plenum mold above.
All cavities on a runnerless system like that can and will be reached on a six axis CNC mill. No nut inserts are needed. No TB's to bolt on because they would be all one piece except for the shaft assemblies and eight throttle assemblies on the production line are no big deal.....compared the fact that there would be very little R&D, testing, dyno and track time required to produce a mass production ITB system....as compared to what would be reuired as inital outlay in cash for a plenum system.
In the end....the cost would be roughly the same.

Do you really think....looking at the complexity of that NON-MASS PRIDUCED ITB unit...that a cost difference of $1000...versus $40 dollars for any mass produced piece whose cost is spread out over 250,000 vehicles.....that the comparaitive cost is really some kind of significant indicator?

If that ITB unit were indeed the very best thing to use...they would have put it into mass production.....and the cost of it will ALWAYS...end up being a fraction of what a limited run unit would cost....spread out over a zillion cars. Also....it would end up looking nothing like what you pictured. It would be black glass filled ABS with aluminm velocity stack bells and steel or aluminum inner TB inserts (in that manner they could change TB sizes at will during the injection molding process).

In short...cost has nothing to do with it. Both systems could be made for comparative dirt when put into mass production. But in getting off the ground, plenum systems are much more expensive....investment and development wise.

I do agree that ITB's...could be much more advanced...if as Miniman82 put it.....there were enough interest for the development cost to be spent. The very same goes for plenums...except....for 98% of the world applications they HAVE spent the development money...and are reaping the benefits...just not for our vehicles.

It appears to me...that you are making assumptions as to why the major car companies put one system into mass production over the other...based upon a personal preference...when there has never been enough comparative direct, properly matched data in testing between the two systems on an otherwise identical engine optimized for each system... to definately support one position or another.

Right now....in the world of cars in general.....plenum systems are king because they can be fine tuned to give the very best HP and efficiency over the widest possible range. Unless you are racing....where ITB's are prevalent....but not yet king either, ITB's are not that practical.

An example of the real future would be the 500+ hp engine in the Audi R8...which uses what looks like are technically ITB's....funny thing is...without the external plenums outside of the velocity stacks...which straighten the air...and where all of the mass airflow metering is done...(and where the actual twin TB's are )......otherwise it is a hybrid of ITB and plenum.
Why spend money on ITB's...when to me the hybrid between the seperate metering of the ITB...without the turbulence of metering plates actually at the ports....is where its really going. Its still a plenum system with single TB's controlling whole banks of cylinders. Ray

[raygreenwood]

So to sum things up IMO the plenum system obviously can be made to work well but most of the reasoning behind it is nothing to do with
performance.The availabilty of $10 throttle bodies in junkyards will always attract the hobbyist but lets not confuse better with cheaper.
Any further discussion on this subject needs to be backed up with some hardcore dyno results and real world examples way too much theory
that can't be backed up here and since the P/R system can only realistically be applied to aircooled motors that don't have upright cooling not sure
why the subject gets so much air time
Cheers
Paul

The subject keeps getting air time...because people like you...keep making sweeeping statements about plenums versus ITB's....with very little to back them up.
When someone build and engine with ITB's....maxes it out to the best of its ability and then slaps a plenum system on it....of unknown volume ratio, with engine cam, displacement and exhaust dynamics not matched to the plenum and TB used...and then proclaims that the ITB's obiosuly make more power so they must be superior...........while steadfastly ignoring that virtually every engine made uses a heavily tuned plenum system (even many of the fastest and most pwoerful cars in the world use plenums...when they could afford otherwise)....you will always get an argument. Ray

[Paul H]

Ray can you cast your opinion on the std 2.1 water boxer intake system as
it seems to be your prefered subject whether or not it is an ideal design
or a compromise by VW for packaging/whatever reasons. It looks good to me.
Just that I know people who have put 40 idfs on these motors with modified
engine lids and they are claiming big gains in all around performance and
boasting big dyno numbers.

[Paul H]

No, not whatever. I don't have much money, that's a fact. Wanna change that? Tell Congress to give the Armed Forces more than the piddly inflation adjustment we normally get. Wanna get butthurt about my cheap ass correcting you? Not my problem.

Obama doesn't have any spare cash as he's spending it all on window tint and leopard skin interiors for his fleet of pimp limo's
not to mention sending to boys over to Afganistan for free training in the art of war.

Dude I think you do pretty good work with the junkyard stuff -so no disrespect to ya

[miniman82]

No, not whatever. I don't have much money, that's a fact. Wanna change that? Tell Congress to give the Armed Forces more than the piddly inflation adjustment we normally get. Wanna get butthurt about my cheap ass correcting you? Not my problem.

Obama doesn't have any spare cash as he's spending it all on window tint and leopard skin interiors for his fleet of pimp limo's

BWAHAHAHAHAHA!!! LMFAO!!