Ok, before you read futher. I'm not bashing anyones intake designs. I complement all of you for trying something not done before. I do like the power gain figures on all of them and it sparked alot of interest to get my gears rolling. I have just tryed looking at all, and wondering what thoughts were put into creating them, ranging from engineering, sizes, materials, flow paterns, etc. ANYTHING.

That said, I have seen things I dislike in all posted so far.

SO...

I've debated on trying my own design. So I started hunting because I know runner length, runner diameter, and plenium size, bends, all make a difference.

My findings on my 3.4....

est tq at 3500rpm, 1.375 (cross section in sq. inches), with length of 24" from valve to plenum.

est tq at 4000rpm, 1.56, 21"

concluison:
low tq rpm= long runner, smaller diameter
high tq rpm= short runner, fat diameter

(turbos should use short n fat )

I can not find crap on plenum size except:
small= fast response, less hp
large=high hp, slow response.
size ranges from half ci to double ci
(turbos should use small )

Materails:
While I am not good at welding, I would have to someway "tack" this up, and send out to weld. Dont like steel, aluminum is expensive, and finding someone to "weld" it is HA! But I do have alot of carbon fiber laying around from a pervious project. Findings on this is that raw carbon fiber disperses heat FASTER then aluminum Not sure about it combined with reson yet. Time for more searching


Questions?
Ccan anyone point me in direction for more exact info on plenum?
Does anyone know length of gm runners? How much of each one is in what part?
Anyone know gm's plenum size? Looks DAMN SMALL!
Anyone have a spare lower 1/3 I could buy? Prefure a 3.1!

 

correction made on above post.

runners are not rated in "diameter", they are rated in cross section square inch.

so if my calculations are correct:

1.5" diameter pipe = 1.7671 sqin
1.4375 = 1.623 sqin
1.375=1.4849 sqin
1.25=1.2272 sqin

 

Stock runner length is like 26", IIRC... If I go drag my intake setup back out, I could tell ya...

The cross-section of the runners is NOT my problem with our stock intakes... it's the length/plenum volume/bends, that is the problem. The middle and upper section have to be replaced.

 

Also, I like a plenum, of approx 80% of the total CI of the motor itself

Turbos should NOT use short/fat, unless MAX STRIP power is what you are after. On a street car, you will MUCH prefer a mid length, mid sized cross section. You have the turbo to pack in the air (pressurized) so runner cross section becomes less important, in relation to runner length/bends.

 

thanks doward.

I finally found someone that quoted from some book... 50-70% of the displacement.

26" runner, good lord
what is stock plenum size, .5l or something?

What was gm thinking?

 

What was GM thinking?

'Dammit... 2.8L to move that heavy *** thing? Gonna need to really work with that torque....'

 

kinda makes you wonder how the n/a 301 moved the 2nd gen f-bodies..

If you could modify the base manifod & relocate the injectors, put fuel logs o them & have the upper plenum going straight down into it, that could work for you. In fact, make it adjustalbe to increas/decrease eh plenum legnth (yeah, I know, solinoids, clearances, and seals.) this could also let you remove the valvecovers w/o major surgery

 

good one doward,

Project, I'd love to do 6 throttle bodys with velocity stacks. Imagine peoples faces when I pop the hood!!

But I just want to replace the upper 2/3 of the thing. I'll keep the base. Trying to decide if I want to "tune" for some revs, or for some torque.

Then come up with a design, and part of that will include possibly trying to make valve covers removeable. Along with possibly installing a fuel guage on the rail, and making it visable.

Right now, I am having problems figuring out how truelows intake fits below the hood. theirs not alot of space between stock and hood

 

I've always been partial to the Falconer intake look. This is a Kinser on Bruce Levin's bigblock Vette. That kindof wows most people.

 

Then, I got something up my sleeve to make John go wow also- Steve Millens (Of Stillen) twin turbo V6 Nissan pumping out about 850hp through dual carbon fiber "plenums" feeding each turbo.

 

My thinking is that the bottom intake is a poor design.
Why?
Not long enough base intake runners.
Edelbrock corrected this with their intakes for 2-4 bbl carbs (by increasing the HEIGHT of the intakes).
That said, ya conquer the bottom intake first then add up top.
Fitting new intake under the stock hood?
NOPE on that part!
Making intake outta carbon fiber is a great idea!

 

there's THIS intake for teh Ellis Juan types.

For teh six cyl peeps, THIS one is for the 3800. Maybe some ideas in these

 

I'm working on 2 different intakes at the moment... 1 is for stock/turbo applications, single inlet/mid length runners, small(ish) plenum, but best of all - WILL ALLOW REMOVAL OF VALVE COVERS WITHOUT REMOVING THE INTAKE. Expected RPM range - 2200-6300 rpm.

The other plenum, is really more of a 'wtf were you thinking John' intake. It's 3000-7000+ rpm. Dual throttle bodies, dual plenums, short runner setup. Killer N/A, basically.

I'm going to finish the stock intake first, hopefully by September. The Dual Plenum Beast will be completed shortly thereafter.

Also building an intake base, that will allow stock/aftermarket manifold usage with FWD aluminum heads.

Got lots of stuff going on, but keeping most of it under wraps

 

i don't like the idea of cast iron block, aluminum heads. if you ask me, that is a warped head just waiting to happen, so i hope that you got your hands ahold of a cast aluminum bowtie block from somewhere. now that(alum bowtie block) is a good combination just waiting for some boost(alum block and heads). talk about something that will take the boost and spit out power, that is it.

 

what's wrong with alum. heads on an iron block? they do it from the factory all the time. these fwd motors, lt1s (in fbodies), umm....lots of others. you shouldn't have any problems with warping a head unless you overheat the motor.

personally, i see absolutely no problem with the base section of our manifolds. the mid section isn't half as bad as everyone thinks it is. the bend at the top of it isn't more than about 45* or so. plus, the casting on that thing is so thick, you can do a pretty good amount of port work in it. the upper section is the most restrictive part. is thought that the complete runner length (including ports in heads) was about 15 inches. i guess it makes a difference as to which "side" you're measuring...but still... something that stuck nearly straight up off of the motor would be about the best thing performance wise but it would look hidious sitting a foot or more up off of the motor, in my opinion.

 

I completely agree with the first part of your statement.



This woulkd be worse and I'll explain why.

Right now the middle and lower intake maniflod sections together are a straight shot at the 45* angle towards the head intake ports. If you come straight down towards the head intake ports from a straight 0* downward angle you would then have a 45* tigher bend into the head and then the 135* bend the other way into the chamber. The 45* runner angle of the middle section is a very good asset.

 

What he said... dagnabbit, you beat me to it :P

As far as teh Fe/Al combo, I'll point you toward the Toyota Supra as evidence...

 

alan the LT1's in the f-bodies are Aluminum block, Cast iron heads. unlike the corvette LT1 which is ALUMINUM BLOCK Aluminum heads. i found this out while doing some work on a bet that a buddy told me he had a corvette lt1 stock from the factory. it was the fastest 200$ that i ever won. because of the different rates of heat transfer, the aluminum heads are not my first choice for a performance application on a cast iron block. now if it were a aluminum block, the they would be my first choice. just my opinion!

 

That wasnt very nice stealing that $200 from your friend, ALL LT1 and LT4 blocks were iron. Very unfriendly thing to do to a "friend"

Oh and if you want to insist that aluminum LT1 blocks exist, if you can bring me one, i'll GIVE you 5 complete LT1's, TWO T56's, a nitrous system, and an LB9/T5 combo.

 

maybe it was a ls1, i dont remember exactly. it was for a 95 camaro z28, it aint worth it, besides who is to say that you really got that stuff? it wasn't my buddy directly, it was one of his friends that runs his mouth too much. by the way just for argument's sake, look around for the engine that the 95 z-cars had in them, cause they are billed as lt-1 aluminum block engines with cast iron cylinder heads!!!!!!! i did the research for the bet and i won cause of it, you are not using your head posting that imo, words may come back to bite you.

 

Words come back to bite you not me, all LT1's and LT4's use din the F body and Y body, were iron BLOCK and aluminum HEADS, use your head and get the correct info before you start a bunch of misconceptions around here. The LT1's used in the B bodys were iron block AND iron heads. Ok I dont have all of what I listed, i've got two LT1 shortblocks, two complete LT1's, two T56's, the nitrous kit, the LB9/T5 setup, c'mon bring me an aluminum LT1 block, tampa aint a far drive, c'mon, or how bout a $500 bet with me that they are IRON block and ALUM heads ? You wont pay up anyway.

As far as LS1's go they are all aluminum block AND aluminum heads, the trucks got a similar version of the Gen3 engine with iron blocks and aluminum heads, though I believe some of the 99 or so units were iron/iron it wasnt for but a production year, maybe two.

And yes a 95 Z28 has an LT1

 

LT1 = Fe block, Al heads.
LS1 = Al block, Al heads.

 

yup, all lt1s and lt4s are iron block, aluminum heads. the caprices and impalas that got lt1s had iron block, iron heads. i just helped one of my friend's do a cam and port work and everything on his 96z28. block was iron, heads were defenitaly aluminum. i think his alum. heads were lighter than our iron v6 heads! ls1s are alum. block/alum. head combo; as was stated above. as far as z28r i c e r having that stuff...i'll vouch for him. he has tons of parts laying around. i have been to his shop on more than one occasion. i bought my 3.4 from him just a month or so ago...

 

personally i don't care what they were made out of, i dont' like the 350 block no matter what you call it. this subject is not worth arguing like kids on. i do believe it was on camarodotcom or something like that, i did a search on google, and started going down til i found what i was looking for. iguess i was was wrong, i will give him his money back. somewhere in my clutter at home i got the website and a print out of what i found word for word! i will look for it and make sure that you all get to see it that way it gets out that they are wrong

 

if you choose to go the carbon fiber or fiberglass route, make a mold out of styrofoam. once you have made the plenum and runners, melt out the styrofoam with acetone or any other paint thinner. the weight savings with this type is tremendous, although the cost effectiveness might not be there. if you go on ebay you might be able to find some intakes for cheap to use as a platform

 

from what I remember of my friends 301 it didn't move the second gen

79 bird with an auto and a 301 just didn't move at all
why do you think some of them came with a turbo? this way they could at least keep up with traffic now


almost wonder what would of been faster his car or my 1.6L accord

 

Been doing some reading, and I read that about the foam and thinner Has to be a specific foam though.

Not doing it for weight, but that is another advantage.

I already have the carbon fiber. Already have some resin, but I dont think its the right type. Have yet to look.

Only thing I really need is the bottom 1/3, and some resin.

I'm going to try an CAI on the grand prix first to play. Dont have to worry about the high heat on that, so I can use current resin.

Main thing, I need a design!! Going with 3.4 style will take my torque band in wrong direction. Going with something like truelo's kinda defeats the point of me trying to get rid of bends (although they are smoother and more gradual). I need ideas!!!

 

couldn't you follow something in the same basic direction as the tpi intake manifold or am I missing something here?
if nothing else what about the style of intake they use on the ford EFI motors with the plenum rather then being mounted directly above the intake manifold move it off to the side this way you get to keep the longer runners and also instead of mounting the tb on facing the fender just move it to the front of the plenum.
only thing with that though is your might need to at that point reqork the intake ducting and so on so I'm not sure there.

granted these ideas alone might not work but they are a a place to maybe think a little bit. sometimes the best ideas come from copying someone elses and just tweaking a little bit from there to fit your desired application.

 

Go to the Cadillac Dealer & duplicate what's used on the 3.5 under the hood.

 

Take 60*V6 RWD block
Add FWD heads (stage 2-aluminum)
Use current top of 2.8-3.1 Intake, so all our current stuff fits & works, easiest.
Create the bottom intake manifold & the inbetween runners.
Done.

 

Now I have a friend that works at a shop that only works on ZR1s and those blocks are aluminum.... AND WICKED

 

Don't for get this when designing your intake.

 

please explain what that chart is for?

 

Just another college bookworm building something on paper rather than the real world. The thought of that chart applying to real world senerios is so rediculous because you have no runner dia and bend changes, no plenum size for feed, and no engine displacement that is sucking the air.

Its probably some chart on some website that some backyard engineer did for his own specific motor that was very highly unlikely a 60*V6 intake manifold.

You can't build one to a chart, you have to make one to get a chart. Its like benchflowing heads.

 

Actually GM High Tech and Performance did an article on TPI a while back that compared most of the TPI components that are out there, and which cams would be good to go with each setup. If I can find it I will scan it and post it.

 

the rpm the harmonics hit would be the same though regardless of dispalcement, plenum size, runner dia and such


harmonics are based upon the length of the runner though granted other things can also create harmonics but he seems to be keeping the harmonics soley on runner legnth and that would be the same either way feeding a 60*v6 a 90*v6 or a flat v8 or whatever

though will at least say I don't know how accurate the graph is being I haven't and won't do the math because I'm too lazy right now :-)

 

ok, but what does all that mean?

Do I wish for it to be in red, green, etc?

 

Well I never went to collage...
I have not made an intake, for that I would need a car.
Over here in Japan there are not any cars worth working on.
(as in I don't have my camaros over here)
I made that chart. I charted every length of runner and harmonic rpm range I thought you might be able to use on a street or race car.
I made this chart so every one can use it and maybe make there car a little faster.
Knowledge is power, that's all there is to it
I am trying to make a Boost harmonics chart (boost makes the runners act as if there longer lowering the harmonic range rpm)
See the rx7 guy know all about it, his car came from the factory using natural harmonics’ of that engine.
There engines can use shorter runner and less rpm's and still use the harmonic ranges be cause of those flanks, it's all most like 1 runner feeding 3 cylinders.
It applies to every 4 stroke engine (diesel or gas).
Not rotary, not 2 stroke.
It all starts with:
C = (square root of) y x R x T
That (upper case C) gives you the coefficient of air stiffness @ room temp.
c = (square root of) C/p
p = absolute pressure air @ sea level @ 20'C
c (lower case c) is the speed of sound.
That is the all about the air going into the engine.
I don't have the notes for valve timing any more.
I use the length of runner and the speed of sound plus how fast the valves are opening and how long there staying closed.
The harmonic pluses are timed so the valve is open as the pulse is approaching the valve so when it opens it is push/sucked in.
2nd harmonic pulse; all that means is the intake valve shuts, a harmonic pulse bounces off the valve it goes up the runner and back down (the valve is still closed d'oh) so it bounces off the valve goes back up the runner and back down again. This time as it moves trod the valve the valve opens.
The black in the graph is no harmonic pulse (for that range).
There is a 1st harmonic pulse but the runner would have to be in the 6-10 foot range to use it on an any thing near street engine.
The 2nd pulse increases the value of p 10%
The third 7% and so on.
(increasing the valve of p on a turbo engine is very cool)
For the colors I just picked them, no real meaning but for there values.
I guess I should have drew it a little more like a turbo compressor map with the values of T, little c and p plus others written on the side of the x and y plots.
If you don't under stand ask, don't flame.

 

You can see my chart any time on my cardomain site.intake page
There are a few other things on there too.

 

the harmonics still apply to a rotary motor being they act as though they are a 4 stroke 4 cylinder motor
and part of what they did with the 89-91 rx7 was to work with the tuning of them to make the intake tract act as though it was variable legnth and it made q decent amount of difference to horsepower production
as far as runner legnth I don't think what came on my rx7 is really that short of a design. they are prolly a good 18-20 inches or so I'm assuming. been a while since I looked under my hood so I can't say for sure right now

 

For those that don't know what all that means.
Increasing the value of p 10% is like adding 1.5psi of boost free.
The second harmnic range could basicly boost engine out but by about 10%.
I’m working on a boost harmonics chart.
I don’t have all the numbers but it looks like each Bar of pressure slows down the value of c enough to make the runners on my chart act as if there 10% longer.

 

Ok then explain this.

If youre thoery is correct and the harmonic pulse "bounces" of the close valve and back up the runner, then a runner half that length (say an 11" runner instead of a 22" runner) would deliver would travel back up to the plenum and reditribute the second half of that pulse to the runner with the valve open.

See here, what most people forget is that a NA motor sucks the air from the intake runners. It is not pumped through them like water in a garden hose. Its all about flow in and out of the cumbustion chamber- it how much it can slurp through the straw.

This is why a larger plenum comes into play so positively because it reduces the vacuum draw that each runner suction created so there is more volume to feed each cylinder without causing as much back and forth turbulance fighting which runner to go to.

 

Dual Plane Intakes.

 

Now thats a great point Karl. Hence why a dual TB and Dual Plenum setup would ultimately be best because it gives twice the recovery time since the bank that just fired is sheilded against the bank about to fire do to the firing order and the draw of each plane. Its what they ultimately did with the 4th gen intakes trying to split them yet the path was too great from only 1 TB.

But a dual plane has no itake plenum volume so it falls on its face at higher rpms were the siongle plane shines.

This is why I still think my design is going to work great because there is enough plenum volume to both 1) feed the runners at low rpms without sucking air from the others until velocity picks up and 2) it has the shorter runners to feed quickly from the larger plenum when rpms pick up.

 

Second Point
The Corvette King Of The Hill LT5 Intake set up with it's varible runner length & also the "second set up runners" opening at a set rate of "vacuum or RPMS"...
A very costly set up, that probably worked great.
But not having that car in my driveway to test this theory....LOL......
Remember the Rochester engineers were given two requirements about our MPFI unit designs...
Under Hood Fitment
Cost.

 

Other cars got a setup similar, as I know the Geo Storm GSi did, maybe it has some parts you could use to play with It didnt get the two sets of injectors, but it's DOHC motor did get two smaller sets of intake runners with butterflies in one set.

Some food for thought

 

That is harmonic cross talk.
I'm not going to worrie about it because it is a hard item to put down on paper.
If I was going to make a plentum I would make it so the pluse can bounce off the other side of the plentum and not go down a nother runner.

 

Might what to read my big cam theory.
On a big cam it starts with over lap.
The intake valve opens as much as 15 and some times as much as 20 degrees (20 is more for 14,000rpm motor cycle engines) BTDC.
The exhaust valve closes lets say 8-10 degrees ATDC when the piston is moving down there is still exhaust getting blown out.
At low rpms this is bad. exhaust gets sucked into the intake runner at low rpms while there is vacuum in the intake. To take full advantage of this there must be positive pressure on the intake valve at high rpms when the intake valve starts opening at 15 degrees BTDC There is a slight vacuum in the combustion chamber. because the exhaust valve opened before BDC, letting the exploding gas blowing its self out. but I'm not going to get to far into that yet.
As the intake valve starts really opening with the piston at 5-8 degrees (I mean open enough to let some air move) BTDC. There is intake air being sucked in and getting forced into the chamber chasing out the exhaust while the piston is moving up in the cylinder.
As both valves are open there most (about 1/16'') at the same time and the piston is at TDC the exhaust is sucking all of its self out and the intake air is starting to force its self and it is taking over.
Once the exhaust valve closes all the way the intake air is trapped and the piston is moving down.
The intake valve is open its most well after 90 ATDC. Its open it's most around 30-50 degrees before BDC depending on if its a big turbo cam or big N/A cam.
And closes as late as 40 degrees ABDC (don't think I have seen any that close later than that), that is when most of the air is sucked into the cylinder (ABDC). Yes there is a lot of air still getting sucked into the chamber because the runner air was accelerated during the time when the piston was between around 90 ATDC and full valve open. So now that the piston has stopped and is now moving up in the bore air is getting forced into the chamber by means of some unseen force.
At this point the engine is super charging its self. The amount of self super chagrined is determined by a lot of factors, rpm, runners, intake harmonics, valve timing (mainly intake open ABDC), spark timing comes into play a lot when you do FI and more.
The self super charging really starts with the exhaust opening well before BDC on the power stroke and the exhaust blows its self out creating a slight vacuum sucking the piston up the bore and some times contaminating the chamber with oil if you don't have good oil control.
Then back to the top and start it all over again.

 

Please do not share any more of your own *Big cam self supercharging* theories and *unforseen forces* (was how you put it?) with us, thank you

Are you '87blue's cousin by chance?

 

C'mon now dont be an ***, he isnt talking out his, do a little research on intake pulse resonation and supercharging effect on natural aspirated engines.

Heck take a look at the lame TPI engines thirdgens were stuffed with, they used this, unfortunately gm tuned them for too low of an rpm range, the LS1 was tuned for a much higher range, even his charts show the general idea between both although I dont think i'd agree with the lengths / specific effects, the LS1 has a much shorter runner than a tpi and has a very raised rpm range where it makes its powerband, a good part of why guys running LT1's arent too impressed when getting into a LS1 car, the LT1 pulls a lot harder down low with its strictly open plenum no tuning short runner setup as opposed to the LS1 which is actually tuned for higher rpm by design.