im not too sure what comparisons we will have, it all depends on time and who has them.

for example the version we gave to SP... it would be great to see a comparison but its working for them and im not sure if they will decide they care to really put something else on there and retune the car to see the direct difference.

right now we are only building 2 of the front throttle ones, one for me, and one for whoever wants it. most likely by the time my car is together again, my engine bay will be too highly customized at that point for me to bother going back to a OEM replacement setup to see the difference, but if time allows i will definatly want to... if someone has a cosworth to lend at the time, but i cant justify buying one just for it.

since i no longer own/operate a performance shop, doing that type of back to back testing is a bit of a pain... hopefully i can provide something. because i would definately like to know for sure how it compares, but at the same time i will be running it either way because i know its going to at minimum support my power, and its going to let me do a lot of things i want to do with my engine bay layout

 

Fixed ***

 

Not being argumentative just a good conversation for the entire community. Agreed?

An RB or JZ straight 6 is not a V6. The biggest things that I note with the JZ and RB plenums is that the single entry directs air to the FRONT face of the runners. On a V6 a single entry would be forcing the air to travel around the backside of the runner and then into the throat. This is a failing that I noticed on the Cosworth manifold. Another theoretical visual problem is the lips of their horns seems very undersized compared to the overall cross section of the horn. Also the lip is finished on the bottom side with a convex radius. This should be a flat or convex radius mirrorring the top of the horns radius.

JZ and RB plenums also use a sloped venturi design to increase velocity to the last cylinders for more equal airflow. It would be immpossible to do this with a V6 single entry.

As you mentioned big HP cars are at shops capable of making new piping, I agree. Along the same thought line these shops should also be more then capable of taking an extra 30 to 60 minutes to remove a manifold. I rarely have to access coils except every 20K miles or so for plug replacement. If the entire build and install is done correctly this should the norm not the exception.

Compromising plenum volume for access is essentially moot based on my above thoughts, which in turn makes throttle placement a non-issue. So we come back to the fundamental fact that it is better to feed the runners from the front side as opposed to the rear. This can only be achieved with twin throttle.

Nissan agrees with the twin throttle principal on both their factory mass produced HR motor and on their Super GT (JGTC) GT500 car. I'll try to locate the exclusive photos I have of the GT500 car's engine bay but the huge plenum volume will be a big suprise. Its literally as wide as the engine and ~4 to 6" tall.

 

definately agree with the things you are saying, not an arguement just conversation!

what you are saying about how the intake ports are facing the outside on the VQ, making the twin side feed throttles make more sense is definatly correct. in one exception tho! im not sure you have seen our runner design, ours are very short and face more upward, near a 45 degree angle up and outward... so its not much of an issue with a front or rear throttle... but i do agree that side feeds could offer more, but i think in our situation it will be negligable.

some thoughts now on the sloping plenum with the inline engines.... (we did that with our stock throttle one for VQ, but really only to clear the hood). there are other things than the plenum shape itself that will effect natural airflow if you are simply flow benching a static airflow situation (which doesnt matter especially on a boosted engine)... such as inertia... the fact that the airflow needs to take a sharp bend to get into the front runners... the air would naturally prefer to pass right over them and continue straight towards the back of the plenum (back being relative to where the throttle enters). this brings us back to the OEM side feed style like the HR or even Tims SFR dual throttle manifold... i think that would be superior for static airflow testing in terms of cylinder bias.

without a ton of solid information publicly available on presure wave tuning (helmholtz) ive often wondered if the non parallel (relative to the runner inlets) plenum surface ends up having unequal pressure wave tuning to the cylinders... i dont have the information or background to realize if the pressure waves are bouncing back more from the displacement of the plenum or the physical "back wall" of the plenum... am i making sense? im typing fast at work lol.

either how, you could taper the plenum the same with the runners laid out how we do it... but in the current design of our front throttle we have not. we are trying a flat version. i would compare it more to what you see on a lambo or ferrari, where its perfectly flat above all runners. we thought about putting a diving wall between each bank of velocity stacks and having 2 plenums, which would work dual or single throttle, you need to connect them for pressure balance anyway

now those cars use 2-4 throttles coming in from the side yes, but they are also NA applications where static airflow bias is a bit more important since its not such an extreme pressure transfer when the intake valves open. i personally believe that as the pressure diffential increases (higher boost) between the cylinder (on the intake stroke) and the plenum, that the static airflow dynamics will become more and more trivial.

your right on the servicability issue being somewhat trivial... but it matters to me to be able to check the plugs inbetween every run on the dyno and at the track since i am aiming for near 1200hp.. a watchful eye becomes exponentially rewarding as power climbs.

now, i dont agree with the comment on compromising displacement for throttle placement... we ahve not done that at all. ill say that our plenum has a metric ****-ton of displacement already, and we ahve the room to expand in 3 directions for more if it ends up too small! the plenum can cover the entire engine over the valvecovers and still have a single throttle.

the GT500 cars should have HUGE plenums... think about... say your are running ITB... your plenum displacement is now equal to the mass of the planets atmosphere... no matter how much air your engine is sucking in, during the entire period of the intake valves being open your pressure differential will never drop... if you are going to put a plenum on your ITBs it may as well be HUGE to maintain that advantage... or even if youre not ITBs for that matter!!!

more thoughtful posts to come when im not at work!

 

there are definatly a lot of dynamics in intake manifolds, and packaging is what will stop anyone in their tracks trying to optimize each one of them... all you can do as try and compromise on meeting as much of them as you can and test it out and see how it goes.

runner length
runner shape
runner taper
velocity stack shape and size
velocity stack placement relative to one another
plenum displacement
plenum shape
throttle(s) inlet angle and its effects on static airflow

a lot of things to juggle

 

a picture from the SP car intake we built... this is the lower plate for that intake... our front throttle lower plate is a lot like it... you can see why i would say having a front or rear throttle isnt exactly the same as when you have the runners facing completely outboard like the stock and cosworth

 

on that note also... if someone wanted a twin side throttle version, it would be no big deal for us to machine a plenum base plate and cap for that... i just personally want the symmetry and layout of the front throttle... sort of like the SRT vipers... a friend made 1725rwhp in his 97 viper using the SRT manifold with stock front throttle body, only cut off and raised the roof to increase displacement (i still always thought the displacement was too small even after that but the car is tuned with 10 egts and 10 widebands so with every cylinder individual tuned it at least wont hurt the motor, only a power holdup at that point.. notice the EGT probes at each port and the O2 bungs)

 

Dave - keep in mind that GT500 cars also run weeny restrictors and run individual throttle bodies, not a single common plenum design. The great things these cars don't have is a unibody Not to mention, they are NA. Way harder (overall) to design a proper NA manifold than it is to do it for boost. As Charles eluded to, when you're forcing the air into the plenum you can get away with alot that just isn't even thinkable when you're asking the engine to ingest the air.



I don't even want to know the cost to design that manifold, let alone build it. I'd bet the first one would easily have bought you a new Z !

A twin setup can certainly be executed nicely, and quite cleanly as well, but definitely requires more thinking, alot more cost, and a bit of fanagling. But, you also get into the cost issues (probably not a huge concern for those who would legitimately buy such a part, and have the setup to warrant it, but it is part of the equation), not to mention having to then think about the entry point from the rad support (depending on the turbo kit). A single entry system where the throttle body is placed dead center, just over the front timing cover, and a single pipe can run through existing channels without really having to hack anything up. Sort of like the LS engines do it.

 

OMG I WANT ONE ...I WANT ONE Charles please get me one

 

lol the front throttle lends to a bit more exotic appearance than the typical waffle iron VQ intakes

if you want the entire car, its for sale, 225,000$ IIRC

 

 

I may be able to loan you mine, depending on the timing... Please let me know when you are ready to run a comparison.

 

Should have my z running again around July/august... Unless the 370 distracts me too much!

 

We're definitely not opposed to doing some comparisons with a few manifolds. Our car, charlies car, either would be great test mules. We'd have to get the other manifolds everyone would like to see results on so maybe Charlie and I can work on setting something up.

Chris

 

I have a very small finders fee.......just order two of whatever you decide and I'll send you my shipping address......

 

Very nice craftsmanship!

You mentioned SolidWorks in an earlier post. Do you create a 3d model and generate CNC paths to mill one of these plenums? I suspect there is still quite a bit of hand finishing work. That is one gorgeous piece of aluminum!

I'm just curious, so if you feel that revealing that information would jeopardize your work in some way, you don't need to reply.

 

For the results I am looking for ...I will help Charles get the off the ground

 

I understand charles points on the stock location TB, but I think that he has shown that he can make something that will flow well (with proper cams of course)....afterall SP is spinning up at 9000RPM on his first model.

Can't wait to see the results of the front style TB.

Don't forget you're going to need a billet girdle on the bottom end too to hold it together.

Tom

 

I have seen you intake manifold. A beautiful piece to say the least! If that is your basis for the discussion then, yes, a single throttle has little effect flow wise.

I will speak from personal experience though regarding the piping leading to the single throttle. It sucks. Repositioning the MAF and getting a 3" pipe to fit on the SFR manifold was not fun. Servicability then became an issue. Also adding a 90 deg bend just before the TB never helped power. Installing an IC with a second outlet or adding an outlet to the existing IC (depending on kit) suddenly becomes much easier and serviceability is again restored. This is assuming that the user has a standalone, which they should if looking for those type of power levels, since twin maf's are not easy to integrate on a non-HR motor.

One downside to the integrated horn that you are producing is that there is no tune-ability to the runner length. Runner length is so important to WHERE torque is produced on the RPM scale. I mean I want to have my cake and eat it to! Also from a cost perspective there are many generic horns available that could be cut and "tuned" to specific setups. The HUGE chunk of aluminum and massive time involved in machining is VERY expensive. Casting takes time and volume. Cosworth is proof of that.

I'm looking from a road race perspective as that's the bulk of my focus. I'm curious how much lower RPM TRQ is lost from the short runner length. In road racing the motor needs to produce a broad power band so that coming off corners there is power available and then down the straights there is power. This is even more important for a heavy Z chassis. A light car like a Lotus Elise or S2000 doesn't need that torque.

Also with the horns not being integrated I would be able to tune the manifold to the course that's being run. Short tight tracks = longer length Long high speed tracks = shorter runner length.

Road racing to me translates much better to the street car then other forms of racing.

I'd like to go back to the JZ/RB vs VQ part. I've driven a 550RWHP Supra (Single)@18PSI and a 550 RWHP (Twin) Z@16PSI. By far the Z was faster and MUCH easier to drive fast. The JZ/RB technology is made to produce super high RPM peak torque (@~7K RPMs!) which in turn gives a large Peak HP # but is very misleading. Reving to 9K+ RPM on a consistant basis shortens the life of the motor considerably. Esspecially on an V6 which has its own inherent vibration problems.

And again to jump around a bit. If I want different horn lengths some that might be significantly longer then in your design then a single center feed throttle will be feeding the horns from the backside. Again never a good idea and a compromise.

 

I agree on this.

There was a dyno day up here at the end of last season. There is a local guy with a RB25 swapped into his 300zx. He was having some vacuum issues that day but on the dyno on pump I made 546rwhp and it was a rather linear pull. After mine was the RB25 car. It was almost humorous to listen to......mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmBA. Like 10 seconds of nothing followed by 1/4 second of full power (and I actually made more power do to his vacuum issues). I can see how the RB/JZ would be less drivable compared to a VQ at same levels.

Tom