TWM/Weber manifold flow

[Ron Earp]

Mike,

Unfortunately the article did not show the development of the formula, which I think is critical. You'd essentially, at some points in the model, be dealing with the physics of a standing wave in an open pipe and this will play into where your resonance frequency is and how it is going to flow. The formula, in my opinion, was rough and over simplified, but, I'll do more work and find out more details.

Filters - you mentioned running K&N filters on the indivdual stacks. There was one person here, might have been Hershal, or Wayne Presley, but it might have been Jerry Jansing (sorry, got out of the garage, late), that saw a 45 rwhp drop with the filters (tea strainer type) in place - I'm working from memory and didn't use the search. But, worth looking into since you are not too far off what you wish to see and this could definitely put you in the ball park if indeed it is a real effect for you.

Ron

 

[Mike]

Thanks. I'll check into that with the new air horns.
Mike

 

[Jim Rosenthal]

Isn't the big difference here that with Webers you have to have enough vacuum signal to pull the fuel over into the venturi, where with TWM or any FI system the fuel gets injected under pressure? So, if I have this right, you don't need nearly as much venturi, if any at all, in the TWM system. Which means less flow restriction, which means more air flow, which means more fuel burned, which means more power. Just curious...I don't know all this math etc.
Sixties GT40 race engines were, I think, always set up with Webers on the SB cars- 425 to 450 hp from what I recall. The BB cars all had 4bbls, Holleys. Made enough power to go real fast, although much of that was axle ratios. /ubbthreads/images/graemlins/driving.gif

 

[Ron Earp]

Hi Mike,

I've got feelers out to find out about that dyno run I remember from years ago with the big drop with filters. I think it was Wayne Presley for sure.

As far as the throttle bodies, how large are yours? Are they really 48mm all the way through? Weber carbs, as you probably know, are done on bodies size - so 48mm IDA, 42mm IDFs, etc. - and then are choked down using a sleeve inside so that a 48mm IDA can at max have a 44mm diameter hole due to the sleeve/choke. Your 45mm webers on your F car were certainly choked and didn't flow like a 45mm straight bore.

Your EFI system, as Jim pointed out, should not have that, but, I wonder if they are named 48mm on body size but there is some internal difference. I'd get some air horns on there, ditch the filters, and see what happens.

Ron

 

[Neal]

I ran with and without the "tea strainer" filters on the dyno and saw a 15hp decrease.

You'll look like an altered funny car with those 17" horns! /ubbthreads/images/graemlins/driving.gif

 

[Ron Earp]

Neal, what was total output of the motor and how did yours compare with what Mike is trying to get?

 

[Mike]

Thanks, Al. Gary at TWM says my 48's flow 340CFM.
Mike

 

[Mike]

Hi, all. Just talked to JC Performance, out in Grover, Ca. (they have a good rep. building various GT-40s. Nice picture of one of their cars on TWM's site, under Ford v-8).
They have experience with 8 stack fuel injection for SB Fords. Joe (owner?) said right off the bat that my straight tube and air-filter on each stack was the worst, robbing lots of air flow. He was big on the longer (~4") bell mouth air horns. I just went ahead and ordered their 90mm horns. I'll post the results when I get them. (I'll try doing the 'patch' air-filters on the rear clamshell inlets, like somebody described sometime last year. Can't remember who).

Ron, he repeated the statement about people getting lots of RPM from these systems...on SMALL engines. Cyl. size up, RPM peak down. Good luck with your new motor. Be interested what kind of numbers you get.

Merry Christmas, y'all
Mike

 

[Ron Earp]

I hope that will work - I'll be interested to see. I know my motor has a good spec with hooked up on the single plane Victor and Demon carb, but this weber thing, well, for the larger motors it is looking iffy.

Faili - did you ever dyno yours?

Ron

 

[Neal]

Best pull: 462HP / 455TQ
Below is a graph of a typical pull.
Don't mind the oil pressure. /ubbthreads/images/graemlins/blush.gif Ended up pulling the high volume oil pump and replacing it with a standard one.

 

[Ron Earp]

Neal, what sort of webers did you use?

Looks like you are rolling over on power around 6200 RPM, and, with your displacement according to the forumla you'd be using 42mm or 43mm chokes, probably in 48mm bodies. Is this close?

I'd like to know how to get these things to produce power in the upper region on a stroker like yours but it doesn't seem possible according to theory. On a 289, yes, but on a 331,342,347.351 not to mention the big strokers, it doesn't seem to work well. In fact, it gets worse as the displacement goes up and one could end up with a huge torque monster that won't pull high RPM.

I have to say though, your motor looks stout and I'd be happy with it! /ubbthreads/images/graemlins/banana.gif

Ron

 

[Neal]

This motor has new 48IDAs from Pierce Manifolds. 43mm chokes. I used hydraulic roller lifters and we did get some valve float above 6300rpm. I think you are right about the top end though. Plenty of power for the street! /ubbthreads/images/graemlins/wink.gif

Below is a desktop dyno curve of my setup.
Interesting comparison.

 

[Ron Earp]

The weber flow diameter prediction was right on the money!

 

Ron,

You asked about the Dyno??? My new excuse now is , I have to wait to get registration tags. It’s a long story, but bottom line is I had to re-register the car (Republic of "K"ali rules!!).

I have to tell you though, this motor screams,,, what does it put out?? I have no idea, until I Chassis Dyno the car again (should be this April, If I get my tags). Here are the specs on the motor (btw, I have the same exact 48 IDFs as you);

Cam- Solid Roller, custom Comp Cams 838-16
Intake lift- .602 Exhaust- .608

Duration @ .050- Int 236 and 242 exhaust

Edelbrok Vc Jr heads 210cc, 60cc combustion, 2.05 intake and 1.60 exhaust

Compression 10.5:1

The engine builder (BADASS Racing) mentioned the same thing as what is on this tread,,,,everything will be in by 6200-6400 RPM! He has been after me to chassis dyno the car and post the numbers here.

 

[Steve Toner]

[ QUOTE ]
If you want the looks and the performance, has anyone ever tried running Webers (or injection) grafted onto a single plane manifold? If it worked I'm sure there would be scope for a casting run. Just a thought, but what would I know. Now shoot that one down in flames!! There must be all sorts of reasons why it won't work, or it would have been done before, surely. Maybe it has been done before and doesn't work. Does anyone know anyone who might have tried this?

[/ QUOTE ]

Inglese has a kit that will let you bolts 2 DCOEs in place of a Holley. If you wanted to try quad IDAs or whatever, you'd have to downsize them because they'd all be operating in parallel instead of one barrel per cylinder... So probably a lot of cost for no real gain (but people say that about Webers anyway /ubbthreads/images/graemlins/smile.gif )

 

[Russ Noble]

Steve.

The real gain is purely to get the look without sacrificing the performance.The people running quads now, have already spent a fortune on the looks and copped a top end performance penalty for their trouble. Twin DCOE's wouldn't cut the mustard appearance wise! Easy enough to order IDA's with small venturis suitably jetted I would have thought.

Personally I prefer the 4 barrel setup because of the performance, simplicity and cost. If everything had quad Webers and then someone invented the 4 barrel I suspect it would be heralded as a major advance on the Webers for those three reasons! /ubbthreads/images/graemlins/twocents.gif

Regards

 

[Ron Earp]

[ QUOTE ]
performance, simplicity and cost. If everything had quad Webers and then someone invented the 4 barrel I suspect it would be heralded as a major advance on the Webers for those three reasons! /ubbthreads/images/graemlins/twocents.gif
Regards

[/ QUOTE ]

I think you are 100% correct! It is looking like to get high RPM performance out of a larger displacement motor, as most are using, webers are not so easy to work out. EFI tbodies are a different story since >48mm bodies and >44mm chokes (actually no chokes used, but you get the idea) are not a constraint - 50,52,55, and 60mm tbodies exist whereas any weber bodies over 48mm are gonna cost a bundle.

 

[Ian Clark]

Hi Ron,

I love this thread, lots of great information coming in from various sources. When both data and theory point in the same direction real knowlege is gained.

We go through this on each customer car. What engine, induction, ignition, gear ratios, intended use budget (notice budget comes last in a GT40 project!)

About 8 Stack / Webers vs 4bbl the most important question is intended use. As it's become clear from the data, Webers work very well on higher rpm small engines and lower RPM larger engines.

Torque is what gets the job done and placing it in the usable portion of the power band is paramount to street or track performance. So a car primarily used for the street will not be a high RPM screamer if you want to keep bottom end torque so you can put around town.

The next engine we're doing will be a 347 on Webers, a combination that's new to us. Intended use street, cruising and occasional track. This thread has already helped us, thanks again and keep it up.

Cheers

 

[Ron Earp]

Hey Ian,

It has been a good thread for me too. I know what you are saying about torque and the power band. But, for my motor, I made the decision some months ago to work with the Audi box without alternate gear sets, 01E boxes, etc.

Which means, I need something that makes power up high to suit the short ratios of this box. Just like you said when you consider the gear ratios, intended use, etc. - I wish to see if a Audi box will do the job and use the car for track work.

So, I need some 7800 RPM action with the stock ratios, otherwise, 1st and 2nd are just too short and 5th runs out of steam too early if one works around a 6000-6500 RPM limit.

If I'd had a smaller motor, like a 289 or 302 it'd be no issue. But, it is an issue with a larger motor, at least a little. The theory says the 44mm choke will allow the 342 to make peak power at 7000 RPM. So, that isn't too bad. I think what I'll end up doing is ordering some IDA in this configuration but, you know what the biggest problem has been so far - ordering them.

Inglase and Top End both say "No, we sell them in the stock configuration and you'll have to purchase 44mm chokes later - we'll set them up stock, you'll like it". No, I won't like it - it'll fall over at 6200 RPM. They don't seem to believe that "yes, I have built a motor and cam to pull to 7800 RPM, and yes, I do want my power there". The problem I've also found is that if you have to purchase the larger chokes later, as well as all the jets, tubes, etc., it costs a fortune. I'll keep working on it, has to be a way to get them configured close without having to purchase tons of stuff extra.

Now, there might be a lot I don't know here too, in that there are all sorts of issues in setting up a set to work with my engine, cam, etc. but I think it possible.

Ian, have you guys taken delivery of one of the new CAV cars?

Ron

 

[Ian Clark]

Hi Ron,

I was just thinking about that, you have to buy 48IDAs with standard jets, air correctors, emulsion tubes, venturies, accelerator pump bleeds etc. then you have buy a whole bunch more to set them up, it doesn't seem right.

Of course you can't buy the carbs in part form to build up to spec, the suppliers are buying "standard 48IDAs" and stocking parts to suit. So there you go, maybe they should package the carbs with a "tuning set" of brass and venturies for your application, at least then you only get one sticker shock.

I've kicked around the idea of using the Ford/Yamaha SVO Taurus V8 for a twin cam screamer type application. The GT40 already sounds like an old formula 1 car with the sequential exhaust, 6,000 already sounds like 10,000 whats 7,800 going to sound like, wow...

Anyways, for track use and being able to keep the RPM up in the power band you should have car that's easy (relative term on a race track) to drive. Also it won't be "cammy" so the power delivery will be predictable. Can't wait to hear your driving impressions

On the new production from Autofutura, my hat's off to John and Jean for the extensive updating of the earlier chassis. This will save me a couple of weeks of work per car and the global customer base all gets the best components and improved functionality.

Cheers