dstefl

I have done some searches and been reading that TBI's don't have a problem with low rpm power loss with a single plane.
So, I was wondering if anyone is running the Weiand 7525 and what they think of it. And also if it will fit under a stock hood.
I will be putting this on a 350 I am building. Here are the spec's:
Ported Heavy casting 882 heads
1.94 1.50 valves with 3 angle valve job
Flat top pistons
9.0:1 Cr
'71 4 bolt main 350
204 duration .451 lift intake
214 duration .476 lift exhaust
Flat tappet cam
I have to stay emissions leagal so i need an intake with EGR. I was also thinking about a Edelbrock Proformer, or the Holley 300-48.
Any input is greatly appreaciated!

ShiftyCapone

iTrader: (7)

I belive that Dewey316 runs this intake but he will chime on to confirm later I am sure.

TKD89RS

i got it, and it fits

9c1Caprice

I have always wanted to see this hypothesis (single plane intake w/ TBI and no loss in torque) tested.

It seems to contradict statements and hard data that runner length and cross section is important to the construction of a torque/hp curve. This pressure wave theory also applies to the exhaust side as well.

Sure, were dealing with single and dual plane intakes. There are structural differences between these intakes that derive from their intended carb'ed uses, such as an open plenum in the single or design features intended to increase the booster signal in a dual plane. However, it is my understanding that runner length and cross section are the most important variables in intake runner length and size is one of the best ways to affect the engine's power curve. On the other hand, there is a great deal of overlap between the intended powerbands of intake manifolds such as an edelbrock performer RPM and a victor jr that these differences may be hard to detect without a proper a/b comparison.

Does anyone have a proper a/b comparison to support these claims?

I am very interested in this subject and just applying standard scientific methodological criticisms to the subject- do not take them personally.

EDIT- In hindsight I noticed that this might be threadjacking. If anyone cares to answer, maybe it should be in a new thread.

BronYrAur

iTrader: (1)

IIRC I think it was Grumpy that ran his engine with a wide array of different manifolds, some single plane and some dual plane and the 7525 was the best in comparison to all others according to him. I think the big advantage of a single plane with TBI is that the large plenum of a single plane helps increase the air flow capacity where TBI is usually limited.

Dewey316

Yes, i have the 7525 manifold. but i have not installed it yet, i am waiting to finish the heads, and dyno the Lo3 as it is

BronYrAur -- yes your theory is correct, the larger plenum volume SHOULD help. like i said, i got the idea from a few very smart people, who say it will work. i will test it :-D

dstefl

It would be very interesting to dyno a dual plane, and then a single plane. I understand that carbs would loose power because of the design but i guess i am not sold on the fact that TBI won't. I have been researching intakes for a little while now trying to find the best one for my setup, and the single plane is most appealing. My only concern is the loss of torque at low rpm. My motor isn't going to be a screamer, will be a mild 350.
Do you know of any installation issues with it?

va454ss

iTrader: (1)

I don't have back to back dyno runs to compare, but the single plane is the way to go.

My engine is as responsive, if not more, with the single plane compared to the dual plane.

All you have to gain is mid and upper rpm performance.

You don't lose any low end response with a single plane.

Carbs need a strong vac signal at low rpms to be responsive. TBI is not a carb; it sprays the fuel in, where a carbed setup must draw the fuel in with engine vacuum.

83 Crossfire TA

iTrader: (2)

Anything that helps a carb get a better signal (vacuum, indication of what the engine is doing) will make the setup more responsive, especially with throttle position changes. Dual plains help this since they separate the cylinders and even only let half the cylinders work on half the carb at a time with a much smaller plenum area.

None of this really matters with TBI since the ECM can be programmed to respond to a greater range of conditions more accurately and the vacuum that the actual TB unit is subjected to is irrelevant. Secondly, anything that gets the injector pod up higher helps with fuel atomization and flow, and increasing plenum volume lessens the effects of a TB that's too small, both significantly helping the TB setup.

??? 882's are lightweight castings. They're all pretty much the same. If you want heavyweight castings you need to start with a different casting number. Any head with a scalloped edge by the outside (under the spark plugs) head bolt holes are lightweight castings.

With proper quench and good tuning you could run significantly more compression on pump gas, even on a very tame engine. Especially if whoever ported your heads knew what they were doing and got some good swirl numbers. Unless you're planning on running boost or doing heavy towing under warm conditions you'll gain power, responsiveness, gas mileage and lower emissions with higher compression.

MrDude_1

i think he ment, heavily ported, 882 castings.

joshwilson3

Will this 7525 fit on a 305 with stock TBI under a stock firebird hood? Since I is supposed to be good, I might try it if it will fit under my firebird hood with an open element. What type of plate did you use when you set your TBI on that carb manifold? Do you have a part number? Also, is this 7525 with EGR or without it?

Do you guys know anything of the Weiand 7547?



Here's a link the to Holley site.

www.holley.com/HiOctn/ProdLine/Products/AMS/AMSM/7547.html+Weiand+7547&hl=en&ie=UTF-8]Weiand 7547 Single Plane[/URL]

Do you think that this thing could work and how does it compare to the 7525?

Dewey316

the 7525 is with EGR, the 7547 is very similar, but does not have EGR.

TKD89RS

mine fits fine, and im using the holley adaptor plate. and a holley TBI.

r90camarors

The main advantage to a single plane, as above stated, is the larger plenum and ability to draw from both bores. And it has been said that you can add an extra 1,000rpm to the lower range (i.e. rated at 2,500-7,500rpm would be 1,500-7,500 with tbi).

I noticed great gains by simply opening up my adapter plate and getting a very narrow and crued single plane effect with my rpm airgap, which I account to drawing air from both bores per cylinder as opposed to one. If I find a descent single plane for vortecs I may swap over.

With that all said, It is still important to keep the heads and cam in mind when selecting an intake. I'm not sure about the heads dstefl, but I think the cam and intake will work well together.

9c1Caprice

I find the hypotheses described within this thread to be facinating, and address the structural designs intended for carbureted inductions that could be a drawback for TBI systems.

However, the pressure wave aspect of induction, which seem to form the first chapter of most performance literature as well well as the induction and exhaust portions, seems to be left out here.

If we consider a build for a street automatic 700r4 transmission (idle to 5500 rpm) why is the pressure wave aspect and runner cross section/ length of a dual plane intake overcome by a open plenum of a single plane intake

I guess my question is, since a holley 670 tbi flows 473.69 cfm @ 1.5" HG and a 350 revving to 5500 rpms

350 X 5500 / 3456 X .85 = 473.45 cfm

-does this mean that a holley 670 tbi can support the air needs of this engine with a split plenum

or

can the large opem plenum of the single plane intake compensate for the smaller small block tbi limited air flow by allowing the tbi to breathe through both bores.

But then that begs the following questions ..How is flow rated on these tbi's - one bore or two? Or does using a split plenum manifold cut the cfms of the TBI?

dstefl

I am running 9.0:1 compression because the 882 heads have 76cc chambers. When I dump them and get some good heads with 64cc chambers my compression will be like 10:1 or so.
I have done some research on these heads and I though that the lightweight castings started in '74. These heads are from 71. Also, the instructions that came with my Fel-Pro gasket set had a diagram that showed you how to identify weather they were the heavy or light casting.
Eventually I would like a better set of heads, so my main concern was weather or not the intake would work with the cam and TBI. It seems that there is a lot of people in favor of the TBI and Single plane way of thinking.

r90camarors

9c1caprice,

The tbis are rated for both bores, though that has been some rescent debate as to what HG the holleys are actually rated at. But honestly, going from personal experiance and working around the 2bbl tbi leads me to belive it is rated at 3" hg with the pod on and injectors spraying, as opposed to the hoped 1.5"hg.

I go off of the theory that more plenum space can help "equal out" if you will, the low flow rating of the tbi. I'm not to sure on the exact physics behind it, but basically it has to do with the time between cylinder fire, as the plenum "fills up". I'm still unsure how it effects MAP readings though. I can go into more depth, but it seems as though you have researched the topic. Basically though, this theory is actually seen in the 502 ram jet. The monster makes 500hp using a stock tpi style (twin 48mm bores) throttle body from what I understand. The large amount of plenum in the ram jet off sets the small bores.

When it comes to tbi, it is kinda tricky. For example (numbers for example as well). Say each cylinder requires 400cfm. But the holley tbi is only capable of 335cfm each bore. So with a dual plane you would need to add more plenum (spacer) to satisfy each cylinder. However, too much could result in power loss, etc.

However with a single plane, each cylinder has access to both bores, thus satisfying the engines need without tampering with the intended setup of the intake.

Hope this came out sounding ok, it's late so I'm not all there....not that I ever am

AJ_92RS

If you click on the sticky at the top, you'll see that I posted a finding in a Holley Performance book that the 670 TBI is rated for 670 cfm @ 1.5"/Hg.

The common problem with a lot of people modifying their engine to high HP monsters is the inadequate fuel delivered by only 2 injectors.

IIRC, a 400 HP engines needs 105 lbs/hr injectors figured with 85% duty cycle (DC) @ .45 BSFC.

AFAIK, the highest you can get is 90 lbs/hr at 80% DC.

That means a limit of 320 HP at 80% DC, or 340 HP at 85% DC @ .45 BSFC.

With an open plenum, the two 90 lbs/hr just became 1 big 180 lbs/hr injector.

This, theoretically just gave you the ability to use two, more common, 55 lbs/hr injectors from a GM 350, such as the LO5, and make ~400 HP.


I don't know if I'm 100% accurate, but you get the idea of why an open plenum may not be a bad thing for TBI.

Of course the problem with making 400 HP requires a lot of cam. The overlap of such a cam may reap havoc with the MAP. I'm sure there are ways around that, but the guys on the DIY PROM board would know for sure.

83 Crossfire TA

iTrader: (2)

All FI TB's are supposed to be rated at 1.5", just like a 4bbl carb. I'd be surprised if they aren't since the bore size is about in the right range for the published flow numbers.

Um, I'm at a loss here. How did you get 400cfm? If that was a realistic number then no heads that I know of would not be a significant restriction on most engines (how many heads do you know of that flow more then 200cfm/port, what about 250 or 300?). I think that you're working on a mistaken premise. First you have to remember that only half of the cylinders fire during each engine revolution, and with most street cams there is very little overlap between intake events of different cylinders.

83 Crossfire TA

iTrader: (2)

AJ, the reason what you're saying isn't exactly accurate is that we're talking about how much a fuel injector can feed we're already typically talking duty cycles in the 75-90% range. That means that at WOT the injector is going to already be open 90% of the time, and whether it is spraying into an open or divided plenum makes no difference about how much that amount of fuel can feed.

AJ_92RS

Who's Andy?

83 Crossfire TA

iTrader: (2)

Woops, sorry... I'm really dragging today... fixed that... sleep...

AJ_92RS

Now that I know you're talking to me, I'd like to know why you think an open plenum makes "no difference about how much that amount of fuel can feed".

I'm going to refer to carbs here for a moment, only for visualization purposes.

Let's say I have a 350. I have a 650 cfm carb. I have a dual plane intake manifold.

The driver's side of the carb provides 4 of the cylinders (#1, 4,6, and 7 to be exact) 325 cfm of air along with 22 cubic feet of fuel at 14.7:1 A/F ratio.

If I run an open plenum intake, the carb now provides all 8 cylinders access to 650 cfm of air AND 44 cubic feet of fuel at 14.7:1 A/F ratio.

AAMOF, if I were to run a dual intake, it's recommended that I use a larger carb (like a 750) just to help offset the split in cfm that dual plane intakes produce.

A single plane intake would be better suited with a 650 cfm carb for increased velocity on a street driven car.

Same with a 2", two bore TB and the injectors. The Holley TBI flows 670 cfm @ 1.5"/Hg, and with two 55 lbs/hr injectors (leaving out DC for ease of math) an open plenum intake gives each and every cylinder access to 670 cfm of air, and the equivalent fuel as one big 110 lbs/hr injector.

I once felt the same was you do, but JPrevost explained it to me. I was hesitant to believe him at first, but after pondering the concept for a while I realized it really is simple logic. I.E., he is right.

Now taking into consideration the formula that is used to determine the cfm the engine will use....

350 cid x 6000 rpm = 2,100,000 / 3456 = 607 cfm.

That's at 100% VE.

Even at 90 % VE (which is about right for a modified 350)...

607 cfm x .9 = 546.3 cfm.

Well within the range of a 670 cfm TB, even when flowed "wet".

If there's something in there you don't agree with, or understand the concept of, explain yourself, please.

As far as how much loss will be seen in low RPM torque, it's hard to say (as someone mentioned) without seeing back to back dyno runs with only an intake swap and appropriate PROM tuning.

Dewey316

AJ,

the point you are missing, as that to make a certain amount of HP, you need a certain amount of fuel. it comes down to the laws of physics, there is only so much stored energy in so much fuel, dual plane or single plane doesn't make a diffrence for fueling the car.

it DOES make a diffrence for airflow. what it comes down to really is having the pressure drops on the intake stroke, effecting both bores, not just one. remeber how all of this works, the ONLY way for air to flow through a TB, or carb, ect. is to have a pressure diffrence. this pressure diffrence is created by the piston moving down in its bore on the intake stroke, creating a vacume. in a dual plane designe, only 1 bore see's vacume for each intake stroke of 4 cyl. so basicly 2 cycles per crank revolution. with a single plane, both bores see that pressure drop per intake event, so you get 4 cycles per crank revolution.

now that is the basic part of it, there is alot more at work here that give you benifits, but reality is, you still have to fuel it, you cannot get away with smaller injectors. remeber with a carb, you still modify the ammount of fuel, not all 670cfm carbs are set up to fuel the same.

9c1Caprice

I would really like this topic to be reviewed and tested by some of my favorite automotive magazines, like Car Craft or Chevy High Performance.

Is it anyone's experience that they would take a reader's topic like this and make it into an article? I would really like to see this topic explored in depth. While it seems uncertain that it may provide a sort of 'airflow panacea' to our TBI induction systems, the solutions the single intake manifold provide as stated here demand to be explored in greater detail. As we all know, TBI is a growing form of induction, and as the corporations start to take notice of the market demand, they usually work off of the research of the hot roddng community. If we address these issues early and aggressively, it could benefit us in ways we couldnt have imagined.

I think ill write the magazines listed above right away and hope they perform such a test. I'm anxious to know what the results are. Are there any more good magazines to which I should write?

Dewey316

i would try the chevy only ones first. CHP, GMHTP, heck maybe even some of the pontiac magazines.

i would really like to see more TBI related stuff in the mags also. this isn't exactly a new idea, more of one that has been rehashed.

this is a quote from a thread from earlier this year (febuary). DanW had done the single plane on TBI a long time ago, and i beleive Grumpy did it back in the day also.

9c1Caprice

I like it. Im drafting the letters now.

AJ_92RS

You did nothing more than confirm everything I said.

Evidently you're missing the point of having both injectors available to all the cylinders and why you don't have to run two 90 lbs/hr injectors any longer.

Using 90# injectors in a dual plane, the #1 cylinder only has that injector supplying it with fuel.

In a single plane, it now has two, count them... two 55# injectors supplying fuel. Those two injectors act as one 110# injector (again I say theoretically because it's not THAT simple).

Since only one cylinder fires at once, there's no split with a single plane.

If you can't understand this simple concept, maybe I'll start using blocks and Legos for you to be able to picture it easier.

Dewey316

i know the point you are trying to make, it is not accurate though.

you cannot fire the injectors twice as often, like you would need to do to make them act as 1 110# injector. if you try to use 2 55# injectors and assume it will act the same as having 110# injectors on a dual plane, you are forgeting how the computer fires the injectors, you would have to fire them twice as often to supply the same ammount of fuel. if we are talking about running at 80% DC, you cannot double that, 160% DC is not possible.

RBob

iTrader: (1)

With a dual plane there is only the one injector feeding a cylinder, however, there is also only one TBI bore feeding that cylinder. 1-for-1.

On a single plane two injectors are feeding a cylinder, however, there are two TBI bores feeding that same cylinder. 2-for-2.

1 / 1 = 2 / 2 = 1

I run a single plane intake with a 2-1/16" bore 2BBL TBI and 80.5#/hr injectors at 22 psi for 109#/hr per injector. It works.

RBob.

AJ_92RS

That's why I said my math is not 100%

When will you ****ing people learn to READ?!?!?!
I'm not say it doubles. That was theoretically!!!!

They don't have to be fired both at once. Can't the PWM be altered enough so they compliment each other. Don't tell me they can't because that just means you don't know how.

When injectors are fired it's measured in milliseconds, correct?

At 6000 RPM you're talking 1000 revolutions per second. Now, as you may or may not know, that's crank revolutions.

We all know that the cam spins half as often as the crank. So now you're talking 500 intake strokes per second.

You're telling me there's no way that the fuel available from both injector can feed that, even with alternate firing?

If that's true, that just proves how much more the stock TBI system sucks *** for performance. I know you don't believe that. So you need to find a way to MAKE IT HAPPEN!!!

Dewey316

whats your problem dude?

when an injector goes static, it goes static.

as in open ALL the time, alternative firing aside, open all the time, is open. no way around that.

AJ_92RS

I'm not following your point... What size engine are you using? What kind of HP are you making? TQ? What cam? what heads?

What you told me serves no purpose without me knowing the rest of the combo.

AJ make picture.

Now... just so we're clear, I'm not saying that 55# injectors are THE thing to use. It's theoretical. OK?

You can easily see what I'm speaking off... if you feel the need, use the picture to explain why it WON'T work. Please.

AJ_92RS

I don't have a problem. I'm trying to motivate all you TBI lovers to MAKE THIS work.

You have a problem with that???

Dewey316

what does your picture tell us?

i know what a dual plane and single plane manifold look like.

Dewey316

no, i don't have a problem, i have tried to explain what won't work about your 'theory', i you told me to

so if it doesn't double... what does this mean?

if by that, you meant having 2 55#'ers is the same as 1 110#'er then yes, you are right. that is why RBob said ' 1 / 1 = 2 / 2 = 1

same as needing 2 90#ers would be the same as needing 1 180#'er

AJ_92RS

I'm not saying you don't know. But there are OTHER people on this board that don't.

What I want is for you to tell me why both injectors can't feed the #1 cylinder (well each and every cylinder) enough fuel to make 400 HP.

The cfm is there. I've already established that.

Isn't there a way to do a batch fire method similar to TPI?

As I said, I'm not trying to prove anyone wrong. I'm trying to say that yes my math may not be 100%, but the concept is correct. There's no way to dispute that.

Now, how much, I don't know. Since you're the one that knows for sure that 'it won't work', show or if you rather, explain to me why.

Dewey316

we are basicly batch firing.

in TPI cars, it fires the 4 injectos, for the 1 bank, all at once.

if you have 22# injectors, that is 88#'s pers bank, per fire.

equivalent to running 1 90# injector (or darn close) on TBI. don't think of them as as 2 TPI injectors. for what we are tallking about each TBI injector is acting as one whole side of the TPI system.

MrDude_1

umm.... it does alternate fire.


and, well...... theres never been a problem with getting fuel to the motor.... just put larger injectors in or move the fuel pressure up... when you have the system capable of flowing the max amount of fuel needed, then you just burn a prom.. (or 20 hehe)




whats the problem?

AJ_92RS

I feel that you're taking me as playing hardball. I'm not.

I'm just saying, for example...

Let's say someone used two 90# injectors, and I know that using a single plane does not double them as one #180 injector. Theoretically it does, but theoretically I'd like to be a millionaire to. But it's not gonna happen

What I'm trying to find out I guess is can the two 90# injectors on a single plane supply the equivalent of say, one 120# injector, or one 130# injector, etc.???

Rbob says he’s running two 80.5# injectors. So what’s the approximate amount of fuel each cylinder is seeing that as? Not one 80.5#, right? It has to be more than that.

If this is one of those things that would only be known from dyno-time, then so be it. I wish I had one of those sitting in my garage. I’d invite you all over for some beer and brats and playtime.

91 GTA Ramair2

TBI single plan.....


Left in jector feed's all 4 lefy cylinders......

right injector feed's all 4 right side cylinder's........


injector to cylinder ratio is 4:1........

91 GTA Ramair2

it's like a carb only with injector's inside it.......

Simple now to hard to understand right??

AJ_92RS

You're missing the point.

And what's with everyone asking "what's the problem"? The problem is, as I said, supplying enough fuel to make more than 330-340 HP. That's the problem with the stock TBI system.

The whole point of this TBI section is to get the most HP from the stock setup to save the money of having to buy a $1400 Holley Commander 950, right?

That's all I'm trying to help do.

If all I'm gonna get is negativity, the screw it. I can get that from my wife. I don't need your help.

91 GTA Ramair2

no no it's for all TBI's stock and or after market guy... but i get what your saying......

AJ_92RS

Since you’re the one that brought up carbs, you should know I'm gonna use that against you.

When using a dual plane carb and a 650 carb, you may need 72 jets in the front and 78 in the rear.

If you pull off the dual plane and use a single plane, you have to rejet the carb DOWN to say, 64 jets in the front and 70 in the rear to offset the fact that now ALL the cylinders have access to that fuel.

I know you're get what I'm saying, I'm just exaggerating the point.

MrDude_1

**vaguly wonders how you're going to suck 330-340 HP worth of air thru a TBI that you're trying so hard to keep dead stock**


umm... ignore that point.


the amount of fuel each cyl sees is exactly the same.(or as accuratly the same as a carbed intake will ever be)

it doesnt matter if its a dual plane or single plane intake.

you're spraying X amount of fuel into the manifold.


if half the air and fuel is going to the left bank and half the air and fuel is going to the right, as in a dual plane.... 1/2X + 1/2 X = X of thoes 4 cyls recieving 1/2X they all get 1/8X.....

if all the fuel and air is going into a common plenum, then each cyl gets 1/8th X



this is a running engine, nothings happening in super slow mo where air/fuel gets sucked into cyl 1... and then the next one, and the next...
its much more helpful to think of it this way... air is constantly flowing into the intake ports.... sure theres a pressure wave when the valve closes and such, but like the ocean, the waves are just energy... the actual air doesnt flow back and forth. atleast in the scope we're looking at.


i think thats where you're going wrong.... as far as we're concerned from the TBIs point of view, all air is flowing into all the cyls at the same time.


the only diff between a dual plane and a single plane is runner length to take in account the mentioned pressure wave...

MrDude_1

its not the amount of fuel thats required thats changed..

its the signal the carb recieves.

Dewey316

Yes, it is a problem. but using a single plane is not an answer, if anything with a radical cam, it makes it more of an issue, becuase the air supply to the cyl. is better, but we cannot push more fuel to compensate. in 'threory' the 670 TBI units, are capable of 400hp probably more. but the fuel is limited. basicly the best we can do, is equivalent to 22# TPI injectors. and it just doesn't supply the fuel the engine needs to produce the power.

the commander950 isn't the answer. it gives you 4 injectors, but IIRC the largest injectors holley sells with the kit, is 85# so you are limited to there. the big boys from holley can't provide enough fuel for more than about 550 HP. the only way to go larger than that, is to go to a dual-quad manifold. use 2 holley 4bbl units, and their special adaptor to run 2 units, off the commander computer. doing that you can approch 1200hp worth of fuel delivery.

AJ_92RS

I guess I'm beating on a dead horse.

Dewey316

EXACTLY!

ding, ding, ding, we have a winner.

that is exactly what happens. in actuality when properly jetting the carb for a single plane vs dual plane, you will likely end up with MORE fuel, forget jetting numbers, when comparing dual-plane to single plane they don't matter, because the way the carb interpurts the vacume signals is diffrent. and that is the reason single planes get a rap for loosing torque, and bad low RPM driveablity. for our purposes, even though you may rejet the carb diffrently, the engine see's the same amount of fuel.