At WOT ITB's and Single/Dual Throttle makes no difference. Runner length from the tip of the horn to the face of the valve is still the same which determines your TRQ curve. Plenum volume would also be the same. ITB's are often confused as making more power just because they're ITB's. This is incorrect. ITB's provide exceptional throttle response first and less restriction second. The additional PEAK HP is due to the shorter runner length and high revving of the engine. Again BMW is a great example. Euro M3 came with ITB's and runners approx 5" shorter then the US M3. Also the plenum volume on the Euro car was larger. Other then that motors were essentially the same. Euro had solid lifters and a a higher redline, US had hydrolic lifter and so a lower redline. US engines make 240 BHP Euro engines make 300+ BHP.

The motor you posted is what is used in the Super GT series for 2007 and 2008 in the Z and GT-R. Its a V8.

From 2004 to 2006 they used the VG30DETT. Here's a photo I've found on Wikipedia:



You can see they continue to use ITB's but with twin intakes. One for each turbo. I have also seen other versions of this motor with plenum volume at almost twice the size (or maybe its not plenum volume but horn length???). This also makes the piping bewteen Turbo and IC and IC and Intercooler MUCH shorter. This equals MUCH better throttle response and less lag.

Restictors are a bunch of crap! Super GT uses ballast as the true way of keeping cars competative and its the only true way to "restrict" an engine. I have a client with a custom built VQ35 making 400HP on the engine dyno through a 37MM restictor (SCCA GT2). It dynoed out on my Dyno Dynamics at ~320RWHP with restrictor. This is with a stock modified lower intake manifold, modified lower plenum and modified APS Upper Plenum. Due to contractial obligations I can't show you pictures but the modifications are minimal overall.

I still come back to the fact that Nissan, the OEM manufacturer with about a gizzillion more $$$ then any of us and more importantly a quadrazillion more brains cells has decided for the GT-R a factory turbo VQ based motor to use TWIN throttles and TWIN plenums. I mean isn't this just reinvent the wheel thats already been made?

Without a doubt the Jenevy ITB's with twin plenums or at a minimium twin inlets (so air is brought to the front of the horns) with single plenum will be the best of all world's. This is needed becasue of the angle of their throttles. Tune-ability, throttle reponse, high RPM power and the ever important "WOW" factor.

Does anyone have a price on the ITB's?

 

like i said before....bottom line is you cut the hood or compromise,you'll never get a straight shot or the plenum volume you want without settling on this conclusion.

 

agreed on all counts. for our front throttle.... in my car i am considering doing a V-Mount setup so that the IC pipe can come out the top front of the IC straight into the throttle. Of course, that isnt much of a likely option for most customers as the time and expensive on these now old cars cannot be justified in a V Mount for most unless they can build it themselves. Even if I go that route, it will be after finalizing the design to fit with stock radiator setup the best I can. The 90 degree elbow will definately suck, but it wont be any worse than the 90 degree elbows already on the IC to TB pipe in the greddy kit towards the IC end. Its not optimum, but a compromise that should hopefully not sacrafice too much. As an alternative to the V Mount, I have also thought about going to a vertical core IC with an outlet on each top corner that would come around the sides and Y at the throttle, allowing the 2 pipes to be slightly smaller diameter would dramatically reduce the radius of the throttle inlet pipes versus a single large facing one way. I am not thinking a lot about the MAF since anyone at the type of power to justify the short runner intake like ours isnt going to be running on the stock EMS... well, maybe someday with the recent flash stuff coming out, but ill jump that hurdle when we get there. Idealy, we are planning to cast the lower half (the run with the runner horns) in a way that we can machine the casting to be used for front or stock throttle manifolds, and just have a different plenum cap. We also plan to have the casting leave the runners closed and pretty solid so that the secondary machining can be customized to slightly vary the taper angle and size of the stacks and possibly a little bit of runner length option.... but of course if we go too tall with our runner design it will shroud the stacks under the plenum cap.


agreed, we do not have much to offer in tunability of the runners. While we can adjust the runner length most likely from where it is being the shortest, to probably another inch, thats about all.... but then again an inch on top of where we are probably isnt more than 1.5" shorter than the revup... ill have to measure my revup unit in comparison and let you know the difference. We have quotes on the casting... our piece is, as you can see, much less complex than the cosworth, and the way that we want to leave the runners solid and machine them secondary means it can be a 2 part mold, the cosworth unit i cannot even comprehend how troublesome it is to cast.

i can actually tell you exactly what is lost in midrange with that design, as we DID actually do a comparison test of the intake before we gave it to SP. We tested it on a 270ish rwhp NA car using standard 03 VQ intake with no spacer or anything... i cant remember if he had the revup lower, but i dont think so. Keeping in mind, this is not a boosted car... it lost about 10rwhp thru the midrange and then evened out around 6500 and then the rev limiter hit so we couldnt see if there would be any NA gains.... of course this manifold is runner length tuned for near 9000rpm in NA application... we tested it knowing that, and just hoping that we may have got lucky and built the worlds first sacrifice free racing manifold... but obviously that was a fail LOL. it looked promising that if the cars bottom end was built to handle higher RPM and possibly had an aggressive cam to boot, that it was going to climb higher, but the 6800 or whatever rev limit stopped that test in its tracks.

now, the big question that we need to find out thru testing, is how much of that loss the midrange will translate to a boosted car, even a 500-600rwhp car... once you hit a psi or 2, which happens nearly instantly, i think that loss will be unseen and then the gains on top will take over, but thats a test away... for top end power i hardly have any doubts, i cant fathom that this unit like we gave SP wouldnt outflow the stock unit once your flowing big air. based on Chris' recent post, perhaps SP will have time to test that for us on their car.

fortunately we have more displacement and VVT. that alone will allow us to go more aggressive on the intake and cam tuning without cutting into the low end to the point of completely killing the powerband... but of course everything is still a compromise. But, one thing to keep in mind, our cars at 600 rwhp make so much torque, that bringing the power band up a bit can make the power more useable and quicker, with less wheel spin struggle.

ill let you know soon when our length compares to the revup lower... it might not be all that much shorter, and i think we can add an inch as an option before shrouding the velocity stacks. we'll see.

 

cutting the hood would be the ultimate solution for optimizing a front center throttle... but pretty soon ill give you guys some more details specs showing that we were able to get the throttles transition to the plenum to be rather unrestrictive.

but for displacement, i continue to disagree with you guys... there is a lot of space on top of that engine so long as you offset your boundries.

 

thanks!

i am learning solidworks personally... all of our creations have gone from concept to reality in mastercam CAD software. my business partner, brandon, is amazing with mastercam and can draw anything the 2 of us think us... so this baby is just as much his as its mine, if not more... i would say the concept lends to be a bit more mine, but the actual reality of it is more his LOL.

but ya its all drawn in CAD, and the software creates the tool paths and we basically load in a solid chunk of aluminum, square it up, and hit the green button.

 

minimum volume should be the displacement of the engine.....minimum.above pics of the v-8 suggest what is ideal.

 

yes but the IC piping is a function of just the IC piping... that car probably has a v mount or alike and can run the IC pipes over the top and straight in. for that car and any factory twin turbo V6 like the GTR.. .the twin plenum and throttle makes the most sense for symmetry and layout... the only advantage of 2 intake pipes versus one is being able to "dispense" the airflow into the plenum(s) with more control in attempt to more equally distribute the air to each cylinder. That exact engine you posted could have a single entry large in the middle and its not going to flow any less, but for the angle and length they have their intake horns at, it would end causing it to be like how you were saying the cosworth and stock is, with the airflow basically coming in behind the horns and having to come all the way around. and thats not exactly a 1000hp engine is it? how high does it rev? it may be hard to compare the function of that intake versus ours (ours being the one im working on)... what i mean is, im trying to personally compare that intake to ours on the type of engine we intend ours to go on, not a fair comparison because i know nissan engineers can by far out-do us... but what im getting at is that i dont know that that intake is really comparable in function for the 1000+hp VQ
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on a V motor is always makes mroe sense to do twin everything... but we were stuck with one throttle on the original VQ, so thats pretty much why we stayed with it. While i think the twin throttle would be cool, we also figured that our manifold already required a lot of changing thigns around to get in the car, if we added having to use a twin throttle, it would be even worse as people would have to wire it, hope it works right, and source another throttle or a pair of smaller HR throttles. i think that while that would be cooler all and all in the end, its just too expensive and impractical on our now old VQs.... once I boost my 370z, we will definately keep the twin throttles for the intake we make

 

you would be surprised at how easy to is to fit that... i wish i felt comfortable at this time telling you exactly what we got last time we measured, but ill say its significantly more than that. we have been doing custom intake manifolds here and there for one-off customer cars various makes and models for a while... im pretty familiar with the minimum displacement a plenum should have for its application.... the hard part is deciding where to stop... i dont really know at what point, if ever, it becomes too big. based on ITBs with no plenum, it would appear that there is no too big? cause open air ITBs have endless displacement LOL.

i can imagine that a really small plenum might aid throttle response at the very low end for tiny displacement engines, but i would think that most performance intakes are long past that. if i can get some solid reason or evidence that there is no actual "too big", then brandon and I can pull the trigger and make this sucker ginormouse... but for now we were just staying reasonable and figured from there all we can do is test it, and then try something bigger and test it. our design can accomodate spacers much like stock for testing higher displacement without having to build an entirely new prototype.

 

omg make an f/i application and id be all over this

 

If I get more hp with this setup...thats cool...but what I really want is the same at less PSI...If I get both....Charles is a God

 

I'd tend to disagree with you, as it's really not that quantifiable. The plenum you use for an ITB is, by it's nature, not the same plenum as you would use for the single throttle body setup. This is why you can't just toss an enclosure on an ITB and expect it to work properly. There is quite a lot of design work that goes into it, as you know. So, the potential for hp is far greater with the ITB setup, as it lets you adjust runner length, lip design, taper angle, etc to suit (within the confines of the engine bay you're working on). What restricts that is of course the packaging. The BMW is a perfect example of what I'm saying - the throttle bodies differed, and so did plenum volume, so as a result the power differs too, but within the confines of the engine bay, they still made more power. You also have the ability to balance the individual cylinder air to fuel trims with an ITB, something not really afforded to you with the same degree of accuracy, with a single body setup. The downside to the ITB is of course overall complexity, tuning, driveability, etc. But it's like anything else - the results are determined largely by the people involved, punching the keys, and the overall design.



absolutely - they used a range of horn lengths and I believe taper angles too, depending on the track. Each requiring it's own specifially designed plenum. No wonder the program costs them so much per car, per year! But again, they are not dealing with the space limitations we are with the unibody and a rad support persay - full tube chassis cars give you alot more options for this stuff. I've been knee deep in this stuff for nearly a year now, as it's something I've been working on steadily for my own car (albeit NA). I have not even given thought to the plenum side of the equation, for the simple reason that the cost involved is more than even the ITB's set me back (I decided to not go with Jenvey's, wanted to try something in a bit of a different direction). On my own setup, just as an example, I have way more runner length than stock (significant amount) and a much better flow angle vs any of the stock setups (revup or non). I have not compared it to an HR setup yet as I have not gotten my hands on one to play with.


Very true, but it still comes down to packaging and costs, which is always the hurdle people have to overcome in the aftermarket. The considerations the OEM has and the considerations people in the aftermarket have often run divergent, so that balancing act is crucial. As a one off project, where budget really isn't a primary concern, there are all sorts of cool stuff that can be done (heck, you could make an intake "header" if you were so inclined!). But when you're making something to reach the widest possible target, even within a specialist realm, compromises inevitably have to be made

 

It's the balancing act. Massive plenum volume is great on paper, but it's the way the runners, lip angle, even the way the common shaft that ties each body together is designed, and how those interact within the confines of the plenum, that determines the "ideal". It's like saying "my heads flow xyz cfm". Sounds great on paper, but what does it really mean? Nothing in the grand scheme of things without lots of other factors being taken into consideration. The cool thing about this stuff is that as one side gets propped up on the see saw, you can often juggle things to balance it out again. If your selection of throttle body, or throttle shaft restrict you in one area, you can often change things on the plenum, or the angle the body is mounted at, or the thickness of the lip of the body, injector placement, etc, to bring things back to center. What you find with the ITB's, and what makes it often such a challenge, is there rarely is no such thing as an ideal - there are rather a series of "really goods" for a given rpm range, given levels of cfm, etc etc.

 

We disagree and I know why. You're looking from the perspective that ITB plenums are VERY different from single throttle plenums. What's not being accounted for is the WHY. The assumption is because ITB's REQUIRE some special type of plenum. This is the wrong perspective. We have to start with the understanding the ITB's are from a race pedigree. In these higher levels of racing where the design of the plenum makes a difference you will see focus on extracting every last HP from a motor with no regard for idle, partial throttle or EMS. Racing requires the engine to be on the BLEEDING edge of performance. This means that the plenum design, as small of a part that it might play, must be designed for the specific application.

I will again use BMW as the reference when it comes to the ITB field. They offer the most engines with ITB's both for racing and as production vehicles.

The easiest example is the BMW S54 Engine used in the '00 to '04 M3 and M Roadster/Coupes. These engine came with ITB's from the factory and BMW Motorsports has produced multiple Racing CF versions.

OEM Plenum - 333RWHP



BMW Motorsports CF Plenum





This plenum was used on the M3 CSL in Euro which produced 360 to 380 BHP with the same redline as the US M3. The only other difference I could quickly find between the CSL and US versions is a upgrade to the headers. Obviously the plenum design does not increase power as significantly as we might believe assuming some power was gained through aggressive tuning (hand-built motors) and the headers. Regardless this plenum is a mechanical bolt on affair for any S54 motor.

NOW I'm gonna kinda blow your mind. Tomei is a VERY well respected Nissan tuner. If anything they were most likely involved with all of Nismo's racing engine development or at least part of it for the VG and VK JGTC engines.

The R33/4 GT-R RB26 is an FI ITB car (not sure about R32). See the example here:



Note there is no throttle on the entrance to the intake plenum and the throttle linkage on the top of the plenum to control the ITB's.

Now Tomei made their one off drag car. Here's a picture of the motor:



Notice anything different? Plenum is essentially the same. The only addtition is a simple single throttle body.

Links to more info on the car.

http://www.tomei-p.co.jp/_2003web-ca...drag_sale.html


Thanks I wasn't really looking for agreement I was making a point for phunk's benefit. We can all assume that that's the only reasonable explination since they are power limited in that class to 500HP.

I've watched your project! Awesome results! I knew you would head towards ITB just wondered when. I hope in your testing you get the chance to adjust runner length and taper to see where the power can be lost and gained.

 

No mas on this thread Dave..... make the Autronic thread instead

 

nope, I fully understand that ITB's have nothing to do with plenums at all - the two are mutually exclusive. However, if you are looking to enclose ITB's into a plenum, they must obviously be designed around one another, which is what I was saying.

With the BMW engines, and the GTR shown, etc, again it's all about that balancing act. They are choosing different routes to the same end for different reasons. The fact that the GTR is maintaining twin turbos and not using any sort of cam advance on the exhaust side, I'm sure has something to do with why they chose the single. Serviceability might be another reason, I don't know.

 

I'm confused then? I thought you said that a ITB plenum is going to be totally different and that you could not just throw a plenum on an ITB set and that it must be specifically designed for ITB's so that they work properly?

 

Hehe working on it today!

 

Correct, that's exactly what I am saying

For a FI application, you obviously cannot have open air ITB's. They need a plenum to surround them. That plenum must be specifically designed for those ITB's, or those ITB's must be redesigned around that plenum. You cannot just take the bodies and put them in an enclosure and expect results -the box must be specifically designed to house those bodies, in the same way that a sub box should be specifically designed around a particular sub. The ITB's behave one way when they are breathing open air. They can act vastly different when they are enclosed in a plenum/box, regardless of how much volume that plenum might hold. I say can, because it will of course depend on the specifics of that engine (head cc, valve diameter, cam lift and duration), and also depend on the bodies being used (going back to runner length, lip thickness, taper, where the shaft is placed, etc). Getting them to act nearly the same in both scenarios is where the R&D of the plenum comes in. That's why it's not really enough to say that plenum volume would be the same whether you have ITB's or a single/dual throttle body (it might, it might not). In the case of the GTR for example, it might be that given the type of ITB's that Nissan uses, perhaps given the body design, the valve timing, cam specs, etc, they are not overly sensitive to the plenum they are placed in. For other engines, this might not be the case at all. That's the only area I disagreed with you

Really the only way to know, is to take a particular car, and try each form of plenum on that car, and retune it accordingly each time. Only then can you really see what setup that car prefers. The ITB setup becomes harder to test, simply because it can be reconfigured any number of different ways. Will be cool to see how this all shakes out on a variety of a cars!

 

OK I see. So my examples of the BMW's make no impact on your thoughts of how a plenum has a minimal effect on HOW the motor reacts? Plenum design is obviously more about optimizing power then getting a car to run properly. You're giving everyone the impression that if they don't have some special plenum designed for ITB's then the car will not run properly. Is that your contention?

We might just be discussing semantics at this point. The issue at hand is the thread started as Jenevy ITB's with a plenum to be used on street cars with a filter. Also we included phunk's design and our personal opinions on how it might be optimized. I just want to make sure there's no confusion on the part of all the people watching this thread and its EXTREMELY technical aspects.

To those that have been reading this and are looking at ITB's for FI or NA this is the pro's and con's:

PRO's
More Power
Better Throttle Response
Tunability for Runner Length - Depending on cars usage, mods, etc

Con's
Price (Isn't it always)
EMS - This is a whole other subject
Fitment and Additional Mods to Work with FI kit or EMS or Both

Neutral

-NA/FI
To OPTIMIZE power the plenum should be designed specifically for the application (None of us has the software, hardware or engineering expertise to do this so its kind a moot point and basically we're using the best guesstimate we can)

It will still make more power if you just put a reasonably sized plenum over the ITB's with runners that have been tested correctly for your application

-FI
You will make more power, mostly due to runner length/taper options
Plenum design is less significant becasue you are FORCING air into the plenum, this allows us to ignore factors of optimizing velocity and venturi effects

 

I'm saying it can be that dramatic, yes. I wouldn't normally have had a reason to study this stuff, but for my own project. If the airbox was the easy part, trust me, I'd be getting one But to start off, it simply isn't in the cards for me, as the design costs and fab costs of just a simple test unit alone are more than the cost of the ITB setup was. It really gives you appreciation for the hows and whys the OEM's do what they do.

Thanks for the edit..we're def. on the same basic page

Just for ***** and giggles when it comes time to do my formal on car test work, I'm going to start first with open filters, then try a variety of filter types. From there, we'll work around the horn design and length, as I've got tons of room to play with on my setup. I've got all the diagnostic stuff here to be able to log the affects these things have on IAT, vacuum, balance between cylinders. I won't have an EGT as there just is no room. I might go so far as to have twin widebands, but I think in my case it's probably not necessary