Street Car Peak Power Where Is Best

[Bsa]

Well tell me share to the group rather then being negative if you can help me and other people out then y not do it that's y these forums are here to help people solve problems not shit on them when they come up with a new idea and having a go.

[zebra]

So..I take it you only created this thread so people can blow smoke up your ass and tell you it is a great idea yadda yadda yadda

If you cant handle people giving you constructive criticism (or even criticism in general) than Don't make a thread on a large public forum.

[Bsa]

Found this on google its what i was trying to tell you but you wont listen

When dealing with air movement there is a latent or potential energy Static Pressure (Sp) and a kinetic energy Velocity Pressure (Vp). Both pressures combined make up Total Pressure Tp. When you put a gauge on you invariably measure Tp unless you are smart enough to install a pitot tube..

So reading off a gauge can be a little deceptive in giving a true indication of what the air is air doing. But lets assume the air is travelling at say 30m/s open throttle into the plenum. Well you know that some of the air will continue as flume until it hits the opposite wall of the plenum, but a large percentage of the air will slow down. The plenum is therefore a cushion box and is designed to proportionaly raise Sp in relation to Vp which is especially desirable for when you have a manifold of pipes all requiring change in direction of common supply flow at different times, like intake pipes do. Of course the plenum will tend to knock out a lot of the pulsations coming back up the intake pipes too.

If you haven't twigged yet, it's the difference in static pressure regions that causes the air to flow and it's friction losses and dynamic losses (flow separation) that reduce the flow.

Now here's something worth pondering. A lot of plenums have a throttle body coming in on one end and the intake pipes lined up from front to back. As the air streams into the plenum the Vp starts to reduce and the Sp starts to rise accordingly, but this will favour a higher static pressure approaching the end of the plenum. To overcome this you really should taper the plenum so that Vp is relatively higher than or equal to that at the TB end, thus making the Sp more uniform throughout. The ends of the plenum should also overhang the first and end intake pipes to provide some cushioning and thereby helping the first and last intake pipes.

What volume should the plenum be you ask? Well a factor of two (2) times the engine displacement is freely bandied about, as is 65%-80% for three cylinders (use two plenums for a six), 50%-60% for fours cylinders and 40%-50% for V8s, but really the best size is going to be determined empirically and I can really see a 6 litre plenum on top of a3.0 litre six using the 2 times rule of thumb LOL..

Some people swear by small capacity plenums to provide smooth engine response, others swear the opposite. The pundits will say the plenum should increase in size as you chase higher rpm, but this will make throttle response worse and low end power will suffer.

Obviously decreased lag should occur with smaller plenums. At first glance a smaller plenum should offer higher plenum/cylinder differentials (P1V1= P2V2), thus better flow and more impedance to blow back during valve overlap, an advantage when using long duration cams. But also consider there is less volume and the suction stroke cylinder may be grabbing air from the other pipes/runners, thus reducing VE overall.

This calculator actaully has some thought behind rather than rules of thumb. Mind you it was only a fleeting thought. Boundary layers ppfft who needs them.

[Bsa]

I'm not trying to get credit or a pat on the back this thread like the title stating where would people rather there power. And seeing as it's 3000 to 6500 the stock runners are perfect for the job why change something when it going to help me out? If the peak power was 4000 to 7500 I would of totally changed directions and designs this is for a street market not a racing market where people buy the best stuff. I'm happy to be told I'm going in the wrong direction but after everything iv ever read and been told there are 2 people telling me differently and I'm stupid for having a go that's not criticism that's just being a pain in the ass.

[zebra]

You really don't seem to understand where we are coming from, there is more to plenum/intake design than just numbers.

BMW for instance went through something like 15-20 intake designs for the 4L M3 V8....and they have a dozen engine boffins all working together on the same thing

and the fact that there is WAY more things that affect the power band than just the intake.

[Bsa]

I can make as many as I want no big deal. If a make one that works then im Charlie shiening ( winning ) if not I'll cut my losses and accept I couldn't do it

[GTScotT]

Make sure you have individual cylinder temp bungs on the exhaust..... Off the bench it might flow different on the motor, you don't want one cylinder running leaner than the rest and melting pistons.

Just sayin'

[Bsa]

Good idea mate I talked to the bloke that will flow test it and he suggested running it in the dyno first as that will give a clear indication of it working properly as it may flow well when tested but it will act different on the car due to pulsation and turbulence

[DVS JEZ]

U can hold the temp gun bsa. We will have to flow test each injector Note it and note which cylinder they go into. I doubt they will flow identicsl and we dont want skewed egt results thinking its ur plenum causing it

[GTR_JOEY]

See isnt this far more constructive now .....

[Bsa]

Yeah everything by the books want to do it right and don't want to fry a fresh motor either

[Bsa]

Sure is more constructive good when you have people helping out and willing to see results

[GTSBoy]

You are saying you want to run it on the dyno to check the flow distribution? And we're supposed to be positive about that? Go ahead, do whatever you want. I should know better than to care.

[Bsa]

Rito

Edited December 2, 2011 by Bsa

[DVS JEZ]

Now now kiddie's.

[Tony de Wonderful]

Really I can't see how a Chinese Plazzaman is any worse than an original. It is just a copy of something where the 'worth' is the design rather than the construction which is very low tech. I suppose you can check inside it and smooth/polish any possible imperfection IF they exist.

Unless you are worried about those Chinese welds blowing...

[Roy]

I am with a few others in saying spend the money where you will see value and an increase in performance. But then a part of me is saying go for it, irrespective of the fact that you will probably sink $1500-2000 into it and go backwards (I have done the same thing )

The math is the math, and provided you passed 3Unit High School math you can keep pace with it. What Zebra is saying is correct, you need an understanding of fluid mechanics combined with your reading to understand the best place to start and tweak. Thats a start...you seem to be on the right path with a willingness to experiment...but I hope your tuner shares your interest. 3 or 4 tunes and you will have already sunk over $1000 into the exercise.

I think for what you are trying to achieve you will struggle to see any increase in torque, response etc over std. Its much easier to extend the high rpm power with a manifold then it is to increase torque.

I suggest if you really want to achieve what you aim then ask yourself what compromises do the std Nissan intakes make? Kind of obvious cost is one of the biggest compromises and multi throttle setups are where you will see the biggest gains.

Whatever you design make it modular so that you can easily change runner lengths, bell mouth designs, and plenum volume. I suspect 6 throttles will be too expensive (or you can just go GTR inlets with a tweak to achieve what you want) so try twin throttle which will be a no brainer but if you want your engine bay to "look" good more then perform better then std then packaging will be a nightmare.

I think with about 5K in development you would be able to get a good result but its from changing the whole methodology not just tweaking plenum volume and taking an inch off runner length

[Bsa]

i understand i will spend a lot of money to get it right. iv been looking over a lot of designs from big name manufacures and taking many aspects on why they are good just need to combine all the best designs into one. i agree its a hard task to take on and even harder to prove they work. but if i spend the 5 g on getting a few designs perfect then one day it will pay off. iv been looking into doing this for years and im now understanding how it all works. i plan on making 2 types one for your everyday where responce is needed and one for high rpm racing so short runners ect. yes i know it could be years before i start to actually get some where but im willing to do that. my tuner is being very helpful in everyway jez is keen to see it work but also telling me if im doing something stupid.

[Roy]

You seem to be giving a lot of thought to plenum size and runner length. Have you given any thought to injector location, number of injectors, throttle bodies qty and distance from inlet valves, types of throttle bodies...

By saying you have looked at lots of manufactures I suspect you are missing the big picture, as they are pretty basic (cheap) manifolds made for what is really a limited volume application which is aftermarket Nissan RB world.

If by big name manufacturers you are forgetting what Hypertune/Plazmaman, Greddy etc are doing and reading fluid texts and looking at ports prototype, rally, indy cars, JGTC cars etc are all doing then I think you stand a chance of achieving something better then oterhs are currently doing. Even then you will need a good enough understanding of what they are doing with their FIA restrictors and wat their manifolds are doing for their setups

A good thing to consider , if you are committed to doing this is what in the world of racing runs an inline 6? Then from there what is running a turbo inline 6? Kind of obvious to start at JGTC RB26s that have some freedom on the inlet side of things.

[Bsa]

Iv been looking at a plazma man today and looked at oem 26 plenum the other day I'm going to have a look at a greedy plenum this week. Iv been drawing down runner lengths injector positions pipe sizes everything as I want to get this right. Iv been speaking to many people about how they have gone about it and where they went wrong also the positives. I plan on starting one this week and seeing how I go. My mate in newy will flow test and pressure test it when I'm done. It will be a plenum similar to the plazma man they have it fairly spot on tho I can see where it could be improved. When I get that right I'll move onto something new. At the moment I plan on just doing turbo inline 6s as that's what I have available to me. Roy you know what it's like to have a go at things when everyone is saying it's better this way so I think you know where I'm coming from by doing this. This thread has been a bit unforgiving for me and made me look stupid but typing on a key board is totally different to talking in person. If everyone was to meet me I'm sure people would see I'm not a idiot and that I'm on the right track.