building my own efi intake

[lyonsy]

hey
iam being to look at building my own intake manifold for a xflow engine and what it to pull like a train for from about 3000 on but still be very plyable below that.
i found this on intake pulse length runners in this section
The basic fromula is:

L = T x V / RPM

Where

L = inlet track length in inches
V = speed of sound, approx 1100 FPS
T = time for the pulse to travel to the end and back, expressed in degrees of crankshaft rotation. Use 90° for this value, if you want to know why you're going to have to read the book.

which if i want the manfiold to be working best at 5000 rpm it needs to be 19.8in long or 15.2in if i decide to rev it to 6500.
iam looking at running twin throttle body of about 50mm for the front 3 and back 3 cylinders.
whould it be better to have a pelnium chamber for each throttle bodie or have them mounted to all 3 runners sort how extractors are reduced down to 1 exhaust? .
whould balance pipe's be beifical between pelnium chambers if i made them that way?
thanks no doubt ill have more questions some engough
skid

 

[Thad]

Three little notes,
Runner length is measure fron the valve seat.
Length should be for rpm where you want peak power, that is not the same as your max rpm. Your engine needs to pull to max rpm. eg Had TZ 350 Yamaha, tune for top end 8000 - 12,500 rpm, impossible to ride on the street. Darn near had to pedal from stop lights, then BAM! Sort of either on or off.
Measuring curve runner or port track, long distance + short distance / 2.

 

[lyonsy]

hey
yeah about 5000rpm is where i want max power so its still street drivable and ill only take it out to like 5500 mabey six on the circuit.
also whould throttle body injection be more benifical then port injection due to allowing more time for the fuel to mix with the air?
skid

 

[Thad]

How many angels can dance on the head of a pin?

Which is better TBI of port injection? There a good debate?

IMHO port would be better, 6 injectors rather than 1 or 2, and at a higher pressure should mean better atomization, sprayed on the intakevalve.
OEMs have all gone to it, don't know of any auto manufactors still using TBI.

 

[lyonsy]

hey
yeah the only 2 reason iam thinking tbi injection as i seen a video of mid 90's reanult F1 engine on a dyno and it was running tbi injection (looked awsome whent the throttle cracked there was this mist around the trumpets then you see it sucked in the engine as it hit 12000rpm 8) ).
if i where to run tbi it whould have to be 6 thorrottle bodiesorta like a webber's but ju8st better meatured fuel.
the other reason is the little hole cast in the head and inlet manifold creates a dead spot in the manifold and costs hp with carby setup's ive seen this gain 20hp when welded up with no other mods on a 250xflow.
so when measureing the intake length i measure the top then the bottom and divide by 2 to get the length :
what has been a decent computer these days to
thanks
skid
ps not sure never seen an angle lol

 

[Geezer 300]

I've dated a couple of angels in my lifetime

 

[Thad]

Seen the same on a Ferrai, the F-1 injection is WOW but not true TBI as we think of it because there is an injector per runner/ cylinder. Wanted to do the same for the system I was trying to build by having the injectors located on the plenum in front and across from each runner. No room.
True TBI as we know has a central injector location for several cylinder or all.

 

[lyonsy]

hey
ok so what whould you call this type of injection then as its basicly what id want to run and whould you locate the injector before or after the throttle bodie.
i think i whould have enough room with the cortina engine bay to run this type of setup.
so now what size runners whould be ideal same size as port?
skid

 

[Thad]

Good question.
Me, I'd call any system with individual injector for each runner "port injection" irrespective of location from entry of runner to just in front of valve.
In the system your are thinking of, where would the air flow sensor, MAF be located. Don't think MAP or manifold pressure would work, not enough vacuum. F1 run in a very narrow RPM band and the ECU is actually simpler than street vehicles, need only RPM and an O2 sensor to function. All other data is known and preload for each race.

OK, you want to injector at entry of runners. Imagine six runners into a log plenum, on one end a throttle body and in front of that the MAF airflow sensor. Injector bungs are welded in plenum oposite each runner so aimed as to inject in the entry of the runner. VIOLA!
The injector bungs available are for Bosch injectors same as Ford uses. About 1.125" long and can be turned to be a cone shape and set into the plenum about 1.0". The Bosch has a 17 degree spray pattern so the gap from injector tip to runner entry needs to be +/- 1.25" giving a plenum width of 2.25". Can be less but not more, if gap is greater, the injector spray will impact on to area around runner entry, not into.
And if you want to see injectors spray then put a polycarbonate window in the to side of the plenum ala the 60s clear distrubiter.

 

[lyonsy]

hey
nah not messing with log motor's got about 5 xlfows kicking around but still waiting for the thr right block to trun up so i can the el series 4L crank (12 counterweights) which love reving with less harmonics at 5800rpm.
ok now i run 6 throttle bodies with 6injectors spraying just after the blade so as not to have fuel build up on the throttle plate and just before the injectors run a balance tube between all 6 runners with a map sensors whould this work?
if not whould the sytem that toyota uses on the 4age20vblack top with 4 throttle bodie manifold work (not sure there system but iam pretty sure its a map sensor.
iam trying to work out a way to run the injectors right at the end of runners so i can have swerl cut into them so as the charge runs down the runner the turbulance from the swril will vaporize the fuel much more effective along with the high psi injection from the injectors meaning less fuel for bigger bang
do you think this is possible
skid

 

[Thad]

Was referring to a log plenum, different to the cast on log manifold.
It would have a volume of at least equal to one cylinder displacement.

 

[lyonsy]

hey
ahhh sorry my mistake.
so you reckon a plenium chamber with the injectors facing the cylinder.
the only problem i can see there is i then have to try and tune lenght each cylinder to help the next one's which i imagen to be a very difficult task?
skid

 

[Thad]

Are each port lengths, from gasket face to valve the same length and you is can have your runners straight from gasket face to plenum no problem.
Tonight I draw some ideas up, scan an e-m to you, at my desk in Nigeria :roll: 1330 our time so you will get tomorrow.
One advantage with near port injectors, I failed to mention is there is less wetting of manifold especially in curves ofrunners and in a dry flow runner the air flow better, less density and viscosity. another OEM got away from TBI. Just as a point of reference the Ford 300efi is dry flow.

 

[6bangerbill]

Drift,

The calculations involved are not as simple as described.As noted in another forum, 3 separate pulses and waves must be cosidered. These waves actually overlap each other each other at various rpms and are not described in a single formula. The best method I have found is to use an engine development program similar to Engine Analyzer by Performance Trends.I bought my program for $100.00 back when it was a dos format.With it you can input your specific engine details ( including intake volume and length) and see the results in the form of a hp curve. I have an older version of this program and use it daily. It will give recommendations for all three and give "starting points". The final dimensions are up to your desired Hp curve. For example, by shortening the runners on my fs1 aluminum headed 300, changing from 17" to 11" lengths added 70 hp @ 7000 rpm, but destroyed 30 ft- lb at 2500 rpm.

Your plenum idea is a good one, David Vizard recommended two separate plenums forming two 3 cylinder, equally timed pulsed plenums for max hp. He also had plenum volume recommendations for a 6 cylinder engine. The balance pipe can be used for hi rpm to expose more T.B. area. The information was published in Fast Car magazine and describes the intake tuning formulas . He also describes the "Helmholtz Plenum" as an adjustable device.

 

[Geezer 300]

And quit starting off with "hey"

 

[xctasy]

And quit starting off with "hey"

nah man, he's saying "yeh", but the Vjacheslav Trushkin Power Board keeps converting it to "hey".

Something about being in the Pacific, I recon.


Oh, the best power comes when you copy a four cylinder superbike carb or Vee-Eight Supercar EFI set up with one carb or throttle body per cylinder, and the injector down stream or the jet at the venturi in the carb. If you are running a classic TBI injection system like Motec and Haltech, they are just ID or DCO Weber replacements, and have to be placed on a classic insolated runner intake. The peak power is best with those set-ups on distances less than 7 inches and greater than 5 inches from the intake port face. If you are making a custom item with upstream throttle bodies, you can run a HSV Group A Walkinshaw or Rover Vitesse set-up where you still have the stock EFI Falcon injection runners, but you add five inch runners and velocity stacks, and then group a twin throttle body air box which has a small tube between each group of three intake runners. It is therefore an isolated runner set-up like a stock Falcon EFI, but has a combined letter box to allow better high end power.

The injector is always best sitting right where the stock Bosch injector sits on any port injection machine. The exact amout of power and torque can be trimmed by running the right bell mouths before the throttle body on a classic Weber ID/DCO or Haltech/Motech set-up, where little things like 1/8" radius curves on the throttle body and altering the ram length before the throttle body can influence things a great degree.

The key is this. A venturi carb system like tripple DCOE 45's, or triple IDA's or Dell Orto DHLA 48's CAN make more power than any EFI set-up because the fuel can be sucked in twice as the 3 rd order intake pulse create reversion. Adding velocity stacks, or stub stacks, or even a flat plate 3/8" away from these tubes can raise torque without hurting peak power.

The creating of low end torque via grouped intake runners is an enemy to top end power, unless you do dyno testing. Then you come up with a set of David Vizard style rules.

General statements from David Vizard require a total reading of the book. We are all just fools trying to discover wisdom in his ancient proverbs.

 

[6bangerbill]

Thats what the balance tube is all about, use an adjustable restrictor inside the balance tube for experimenting. An adjustable plenum volume is helpful too. You can experiment with carburators, efi, or constant flow injection on a plan "b" designed manifold.Build a system, test it either dyno or drag strip. Always build in adjustable tuning method for plan "b" changes. After a little experience you will discover that your first try is always wrong. Finding your combination takes alot of work, trial and error. Mostly error and trial.
If you were working on a bent eight, you could just buy a proven combination but what fun is that? Million dollar engine builders will gladly take your money, they are worth every dollar because they spent the hours needed to make the big technical advances. And thats why David can make a living writing tech articles, most of us appreciate the insight he gained from his years of testing his ideas.

Dont get me wrong, don't copy David, his testing is specific to his combination. If you can verify with a engine modeling program do it, measure v8 racing manifolds for volume and length, read everything you can get, look at winning combinations (not nostalgia engines), and do all the calculations you can.
Be cautious 4 cyl,6 cyl,v8 or even v10 intake tuning are totally different and some technology doesnt transfer directly. As an example, a v8 intake plunum recieves suction pulses every 90 degrees, an inline 6 open plenum recieves pulses every 120 degrees. This makes a real difference when choosing cam overlap and intake runner lengths with a plenum intake system. In a v8, one cylinder is at tdc with both valves open( at overlap position), while one cylinder is half way down the intake stroke. The intaking cylinder gets more burnt gases from the overlaped cylinder than fresh air from throttle body. Low end torque, idle quality, and converter stall speed are all really affected. In contrast, the 6 cyl engine has 30 more degrees to close the exhaust valve and behaves much better at low speeds even with a close lobe center cam. So, bigger cam overlap without losing low end torque with more mid range and top end! Say Yeh! We dont need no stinking v8 polluter.

 

[6bangerbill]

Drift,
Here are some pictures, hopefully not too big ( new at picture posting). This manifold fits the fs1 head cnc ported (gmpp) w/ stock size 2" valves (modifying for 2.04 tianium intakes) for a 300 ford. Tuned for max of 7500 rpm. Note: the distributor will have to be move to the timing cover and be replaced with a hilborn pump(shorter!).



Will start on plenum next.

 

[80broncoman]

Why not make a wild intake? Variable length runners can be done much easer than you might think. Ever look at a Ford 4.6 truck intake?
It uses a tube that turns slightly to let the air go straight down (6 oclock)for the short length or the (5 oclock) where it enters the same runner and the air must run around counter clockwise making the length much longer.

For a 300 you could have the short entrance at 3 oclock and the longler entrance at 4 oclock with the air running clockwise.

 

[6bangerbill]

I read an article and saw pictures of that manifold; could not figure out how both runner sets entered the plenum or plenums. Pretty complex piece, but dyno charts showed a 70hp increase in upper rpm hp with the shorter runners. It is my opinion that the loss of low end torque on a long stroke 300 ford six, with a short runner manifold, can be compensated for with a nice low geared transmission like the 4r70w and little higher stall converter when used with a light weight roadster like mine, and adequate compression and cam selection. Or maybe im just lazy. The extra crankshaft degrees between cylinder firing should increase low end torque over that expected from a 302 v8 too.