ok so i got a real good deal on a skunk2 70mm tb that i couldnt pass up. my setup is a full gsr with 81.5 pr3's, 3 angle valve job, skunk2 stage 2 cams, supertech complete valve train, blox intake manifold, 3" intake with bpi vs, tri-y header. will i lose power and torque? if so i am goung to put it up for trade for a smaller tb.

 

you really do not need a TB that big on an NA motor. 68 is the biggest id ever run. 65 would probably be optimal for your setup

 

i understand that but will i lose power? is it worth going and and finding another tb? how big or little is the difference between the 65 to 70?

 

No

 

5mm or .197" for you people stuck in the dark ages.

 

what i mean how big is the difference hp&tq between the 65&70? what i am trying to say is am i losing 15hp or is it something stupid like 1 or 2hp? i put up a thread on a local forum for either a 62mm itr or another 66mm sk2. i want this setup to run well together so if a 60mm tb is what i need thats what ill get. i am not a fanboy who assumes bigger is always better. i just got a great deal on it.

 

no what? a little more info would help me thanks

 

lol...dark ages eh! 5mm vs 0.196850394 inches....... I'll stick with 5mm, much easier to remember.

Not sure if you will actually loose any physical power but you will more than likely move your tq up in the RPM range from what I have read and seen. I hear it is supposed to quicken throttle response as well. But that is hearsay. I've never done it myself.

 

well since i dont take my car up to 9k+ i am guessing it would be better to go with a smaller tb? I am not really getting straight answers but i have someone with a 62mm itr who will trade me and give me 100 on top should i jump on this?

 

yes you should do that trade

 

think of it this way, how many CFM does your intake and head flow? You would be amazed how much that 62mm TB will flow CFM wise, more than enough for the rest of the motor and it will help keep air velocity up which is always good

 

not sure howmuch they flow its just a blox manifold, 3" short ram with velocity stack, and a 3 angle vj on the head never flow benched it. i amm going to do the trade.

 

exactly probably the same or less than that 62mm TB flows so its a smart choice

 

get it port matched to your im

 

no you want your opening larger than your tb by about 4mm to create an anti-reversion step

 

sounds like a plan

 

Does this anti reversion step actually do anything? Is there any proof of over boring the manifold opening begin of any actual benefit? I can see it working if the reversion was based on an individual runner basis... harmonic wave tuning.

Here is the data that I have compiled from the OEM Honda plenums that I have. Now I have no absolute scientific evidence to this other than a formula. And the formula is not so "pie to the 3rd crap" scientific ether.

Runner length, from the back of the valve + the plenum volume (space between the mouth of the runner to the back of the plenum) = the optimum length for a tuned wave harmonic.

One of my examples;

F22B2

13 1/2" runner + 3 1/2" plenum = 17" x 1.8" ID

• 2nd harmonic, RPM range is from 6911 to 8386 with a pulse strength of 10 percent
• 3rd harmonic, RPM range is from 5192 to 5934 with a pulse strength of 7 percent
• 4th harmonic, RPM range is from 4048 to 4527 with a pulse strength of 4 percent

Is it just ironic that the F22B2 hits peak tq at 4200 and peak Hp at 5500 rpm? Isn't that 3rd and 4th harmonics?

The third and forth harmonics are what the F22B2 are possibly based on. When the 4 runners are not at equal lengths to the throttle body. Would a reversion step do anything for each individual intake port? Remember that the ports are equal length to the back of the plenum.

Am I totally off basis in thinking this way? Please someone bring some more intake plenum reversion info to this thread............

From what I have studied, exhaust reversion works because of the individuality of it. Does this principle work for a shared plenum style intake as well? I'm sure it does to some extent. But I'm sure plenum design has more to do with it than throttle opening.

 

well optimally the head will be set up for it as well with the ports of the intake being matched to the gasket and leaving the manifold alone. alls this does is help keeps the pulse waves and flow from reverting back out of the head. A stock z6 head and manifold has TERRIBLE anti-reversion characteristics. The guy who built the flowbench here, Leshok, tested it and it actually flowed more with reverse flow than standard flow. By changing those characteristics alone you can make a much more efficient and powerful engine.

 

Interesting.

 

shouldnt the tb be 3-4mm smaller than the intake manifold?
(IMO) i would only go port match if i was going turbo which will prolly be never!

 

is that a trick ? if the tbody was three of four mm smaller then the mani that would mean the mani bore is 3-4mm bigger then the tbody ... thats the same thing the other dude said but worded differnt

 

always have the port size the same on the tb and im for perfect flow

 

does this anti-reversion also hold true for all TB to mani to heads?

 

Why don't you just install it and see how it drives? Or is it brand new and you don't want to damage it? Generally a throttle body that is too large is going to affect throttle response at lower throttle angles.