JPrevost

I've been running a lot of simulations lately for our formula team and for fun I put in my motor. It isn't prefect but it does say 330hp with standard long tube headers and high rise dual plane. Anyhow, I ran the simulations with my tri-y headers with gutted cat (not off-road pipe), exhaust cut-out opened, and the 2" bore Holley TB vs the same thing with a 3.5" monoblade throttle body. Not only did the 3.5" have more peak power but torque from 2000rpm on was substantially higher. I'm talking nearly 20 ft lb all the way up to redline. I'll attach a graph later tonight to show some interesting facts. Stuff like the gutted cat have almost no effect vs an off-road pipe in it's place.
So even if you do have just a few modifications I hope you have done the ultimate tbi mods or plan on doing them in the near future. If you've done a cam swap, all exhaust work, and intake manifold then I do recommend going to a 2" bore TB asap. I knew my motor was being held back with a Holley TBI but I had no idea it was so much. I tried going to the track last friday but for some reason they were closed. There was a line at the gate and people were pissed. I drove 45miles for nothing. So I'm going this friday (so long as they're open). Looking for mid 13's first pass and in full street trim. Next time to the track I'll drop the front bar, remove STB, play with tire pressures.
Oh yeah, and the simulation software I'm using is Virtual 4-Stroke. By far the best simulation software I've used to date. With our little F4i motor running through the 20mm restrictor we were dead on from the actual dc dyno numbers (except anti-tuning peak). I might be looking into GT Power soon but I'll have to see what our budget is like. I'm also going to flowbench a stock TBI vs Holley's vs stock with ultimate tbi mods.

Dewey316

Jon,

i would be interested in those graphs.

also, what is the deal with a 3.5" monoblad? is this some sort of modfied TB you are making for youself? as far as i can tell the flow would be signifiacly greater with a 3.5" single round bore, than 2 2" bores, the surface area is about 50% greater. the only problem i see with something like that would be injector placement, my first thought is that it would be hard to place 2 injectors in a position that would be great for fuel delivery. i would be very interested in some more info on this!

JPrevost

I'm at work right now but when I get back on campus I'll post the graphs.
The monoblade was just something I through in there. Keep in mind that the simulation software we use only has port injection and direct injection, no wet-flow because that adds to the complexity. ALTHOUGH.... there is a way to "inject" any gas or liquid anywhere along the flow path. I'll see if I can simulate it.
As far as making my own TBI, nah, more like cutting up 2 stock TBI's, welding them together and running with that. I figure 4 1 11/16" bore's should be plenty for my motor. I'll simulate that next. Then I'm going to mess around with the plenum size. Then maybe futz around with designing a port injection dual runner (dual resonance/plenum) intake manifold

Dewey316

i think they way to go about a monoblade, would be something like this

JPrevost

Here you go. I'm running the simulation now on the 4 1 11/16 bore TBI hack I've got in mind.
What I would like to do is get data on headers for f-body's.
This simulation software is all about flow, not actual. The advantage of flow is that it gives good comparison data but is usually 2% off from actual .
If somebody would mind posting primary lengths and y-pipe dimensions for edelbrock, hooker, slp 4-1, and full lengths I'd be more than happy to test them all.
Again, a reminder that these charts are not actual but simulated to only show obvious traits for tuning.

va454ss

iTrader: (1)

How would a TB with 2.2 inch bores compare to the above?

That is what I'm using.

Bill

GNVAIR

Excellent info!
Here is a thought/idea for you. Rather than going to 2 throttle bodies, why not make a mono blade throttle body out of a stock tbi throttle body.
I was recently at my friends fabrication shop, where he is currently building a twin turbo Impala SS. It has an Arizona Speed and Marine billet mono blade throttle body for the LT1 intake. I am sure that I could possibly modify a tbi throttle body as such on the Bridgeport that I have access to. This would probably solve most of the air flow problems. I would love to hear some thoughts on this.

http://www.brammo.com/ultima/buildjo...s/P1010021.htm

va454ss

iTrader: (1)

I just talked to the guy that modified my 454 TB from 2.0 inch bores to 2.2. I asked him about the monoblade idea, and he didn't think it possible. If you are going to modify one to monoblade status, why not start with the biggest one (454)?

Bill

Dewey316

i have thought about that idea too, but i probably not skilled enough to fabricate it. i would think for somone who knows what they are doing, making it a monoblade would be fairly easy.

some more thoughts on that though, are if you go too big, you may start going backwards.

JPrevost

Here is the new results with the 4 barrel 1 11/16" bore. The advantage of using the smaller bore is obvious. Not only is it plenty of air but if done right you won't have to grind away at the square bore flange to get it to fit. Only other solution is to get a fancy adaptor plate or a dominator flange intake.
Again, these are only simulations but as you can see the torque curve is near the 380 factory rated ft lb ratings at nearly the same rpm. 3800rpm from GM and 4000rpm from my simulations. Notice the mono-blade is closer to peak torque at 3800. I must be pretty close .
Anyways, I'm working on building a good relation with the flow bench "master." He's a Ford guy but at least it's domestic! Oh yeah, and the flowbench you see most magazines use is sitting in the corner of the room with dust on it. It's a POS compared to the setup they have. Most of there testing is sound and resonance but it's still a superior flowbench.

va454ss

iTrader: (1)

So, has anyone tried to modify a GM TB into a monoblade design?

After looking at mine, I don't see where it would be so tough. The injector pod could remain similar to stock with the center leg removed.

This would great where a vehicle has to pass the visual inspection.

Bill

91blackgta

That would be great, but what intake would you use. You couldn't use the factory intake.

va454ss

iTrader: (1)

You would use a TB to Holley square pattern adapter installed on a carb manifold of your choice. You would remove the divider in the adapter.

Bill

GNVAIR

Here are some more thoughts on the tbi air flow issue.
A friend (who happens to be a big time LT1 guy) were talking about my truck and I was telling him how I dont have any problem with fueling it. It appears that it is air flow limited.
He questions how that can be as the throttle blades on a 454 throttle body are 2 inches and larger than a production L98/LT1 throttle body. The only answer we can find is the fact that the injectors are mounted right in the air stream of the throttle body.
If the engine was multi port using the same computer and throttle body I would be willing to bet you would see a substantial difference in power.....especially at the top of the tachometer.
So in closing, I would like to see actual air flows of the following:
Stock 305/350 throttle with and without injector
454 throttle body with and without injectors
Holley 670 throttle body with and without injectors
and for some little extra we could throw in a stock 94-95ish LT1 throttle body to give us something else to compare with. LT1 guys can make well over 400 horses with their stock throttle body and it has smaller blades than most tbi throttle bodys.
I feel that you will find a major increase in airflow with the injectors removed and thus, that will be your restriction.