Note: I hope this thread doesnt degenerate into a flame war. These two builds have always threw me off and I hope to learn something.

There's two CHP engine builds,Hot, Hot, Hot Cam and New Wave TPI .

Both of these buids use vortec heads, GMPP 1.6 RR, Hot cam, but the dyno numbers really throw me off.

Carb Hot, Hot, Hot Cam
rpm torque hp

3,000 371 212
3,200 381 232
3,400 399 258
3,600 412 282
3,800 418 303
4,000 419 319
4,200 419 335
4,400 423 354
4,600 422 369
4,800 419 383
5,000 415 395
5,200 407 403
5,400 399 410
AVG Torque: 408

New Wave TPI
rpm torque hp
3,000 407 233
3,200 409 249
3,400 407 264
3,600 419 287
3,800 419 309
4,000 426 324
4,200 421 337
4,400 414 347
4,600 402 352
4,800 387 354
5,000 370 352
5,200 353 350
5,400 340 350
AVG Torque: 398

What really suprised me were the following facts.
1) The Carb build was a 'junkyard' build used to highlight the possibilities with a junkyard l05, vortecs, and a Hot Cam kit.
2) In Contrast, the TPI build was a trick setup with large runners used to promote a very expensive TPI setup by Scoggin Dickey.
3) The two builds were published by the same mag.
4) The average Torque for the carb was much higher, despite it being a junkyard build
5) The below 3000 RPM range that the TPI setup could have beat the carb was not provided by the TPI dyno. it was availabe to 2,600 on the Carb dyno.
7) Of course you cannot directly a/b these two builds, but you have to give all the advantages to the Scoggin Dickey setup, because their numbers were used to promote a very high priced TPI setup. The other Carb build was most definately built with so much care. Even then did the carb setup make more average torque.

Why is this so?

 

Probably used a stock .bin to run the TPI

 

I know most of my TPI bretheren will be insulted from what I'm saying, but the fact of the matter is..... Fuel Injection was designed to manage fuel and air, as well as gas mileage and overall driving. It was never meant to 'out-perform' the Carb, as far as Horsepower and Torque are concerned.

Carbs are just 'considered' a little more sloppy, as far as fuel and air management, whereas TPI is PRECISE. But this doesn't make it 'stronger' than a Carb, just more reliable and precise.....

 

The TPI set-up is what it took to get the same HP as a carbed 350 HO with a lot less cam. You didn't mention 52cc TB, 1-7/8" long-tube headers, aftermarket runners (and I assume ported plenum, but I don't know if they did that).

They also didn't say anything about the PROM required. I assume they're using some sort of SD setup.

I'll always vote for keeping and improving the induction you currently have, for a street driver, anyway. TPI was designed to improve fuel economy, reduce emissions, and give a good seat-of-the-pants impression. It delivered on all counts. Put it on a dyno or take it to the drag strip, and you reveal what it wasn't designed for.

 

Excellent Point!!!!!

 

I think Morley & 5-7 kid brought out part of what I'm looking for. I was looking over the article in my chevy hi perf book to answer the questions posed here and ran across something worth noting.

The peaks of 427 lb-ft of torque and 354hp at relatively low engine speed are strong but by no means optimizedd. According to Scoggin-Dickey's Nickey Fowler, they performed this test using the stock '87 factory F-car fuel and spark curves with slightly larger 24 lb/hr injectors.

Ok, this partly answers it for me. I must have looked at these builds 20 times and missed that.

Strange, you would think that Scoggin Dickey would have put more effort into hawking their very expensive TPI setup. They changed out runners, valvetrains, headers, etc. but didnt get into chip burning.

hmm.

Thanks for the replies. The comments I get in this website to questions I have are very helpful. Plus, this didnt degenerate into those My induction is better than yours debates better left for the playground.

 

MAF is more forgiving of displacement/cam changes. That's probably why they used it. But, that held them back on the top end.

Sounds like Scoggin-Dickey found this harder to pull off than they thought it was going to be when they started on the project. The holder of the checkbook probably told them to cut the losses and get something out on the street.

 

Nice. Thanks for helping me cut through the BS there. The most interesting thing I found, as Ive already stated, was the torque averages. though Im hard pressed to arrive at any hard conclusions now.

Since there are so many unanswered variables here, theres hardly anything left to glean from this --If your speculation about Scoggin Dickey is true, then the only lesson to learn maybe that modifying your TPI setup can be difficult and can dramatically lighten your wallet.

 

I want to dispose the myth that carbs are unreliable. A well maintained Carb, which means- fuel/air filter replaced regularly, and clean gas used, will run for a damn long time , and you don't even half to worry about corroding wires, or fragged sensors.

 

The exact same thing can be said FOR FI. Checking your connections should be part of your yearly major tune up.

 

I think what 430T/A was getting at was.... There is far less to go wrong in a carb setup than FI. Any properly maintained system can last a long time. It is simply cheaper/easier to maintain a carb than fuel injection.

Somewhere on this board, I saw a mis-spelling: fuel infection. sometimes I think that is not too far from the truth.........

Keep in mind, my car is fuel injected, and I have NO intention of taking a step backward in technology and running a carb. I would like to see anyone get the kind of power TPI produces with a carb, and still be able to get 22MPG on the freeway..... (with no prom tuning....)

 

Oops, too late.

I've had reliable carbs, finicky carbs, and things that have gone wrong with FI. Overall, fewer "driver" issues with FI, and always better mileage.

As I said already, "I'll always vote for keeping and improving the induction you currently have."

 

The freeway is the only place the carb does do as well as the TPI for gas mileage. TPI shines in stop and go driving. I drive my 770 cfm carbed 350 60 miles everyday on the freeway and my interval to the gas station is exactly the same as my 305 tpi motor was in the same car.

Now the weekend is an entirely different story. Stop and go traffic and cruising around I notice a difference. But on the freeway I'm barely in the throttle, there's just not that much difference.

And as far power, it just depends on where in the rpm range you are wanting to make it which is better. And moving the rpm range up is a great way to make more power. Long tube runners just don't like that as much as a straight shot from a carb down to the valves.

 

you know, these carb/fi comments are pretty good. (knock on wood)

Arguing over the internet is pretty weak. Better to do that sort of thing direct and face to face. My $0.02

 

.

 

Whats suprising about those results? The TPI made more torque down low where it's known to do and fell off on the HP up high when the 'tuned' part started working against it and it couldn't flow as much.
The carb made less torque down low and pulled higher because it flows more air.
Sounds as though it did exactly what was expected.

 

I disagree. This highly depends on how you're Carb is set up. The only difference with TPI, is that the ECM is programmed from the factory to get the best results possible.... but anyone who knows about Carbs knows that they can average practically the same gas mileage if they 'really' wanted to in "stop and go"....


Well everyone has their own individual preference. For instance, you utilizing a 770 cfm on you're 350, obviously won't help the Carbs gas mileage on the street. We built a Pontiac 400 about five years ago, and got the greatest all around performance using a Holley 600-cfm..... and the motor pulled like a raped ape.

 

Yes , if I really wanted to I probably could get much better mileage in "stop and go" traffic. But it's much easier on the highway to. And as far as size of carb goes, as long as it is metering air/fuel correctly, you should get the same mileage either way. Mileage has more to do with weight of car being moved, efficiency of the combustion chamber, tune of motor ect...... Driving around under normal conditions you should be using the same amount of cfm whether the carb is rated at 500 or 800 cfm. That's why we have throttle blades. They don't just go wide open anytime you press the gas. They open to the amount of cfm your foot tells it to. And a 770 cfm carb is capable of flowing 300 cfm just the same as a 600 cfm carb is at part throttle. And as long as the liquid fuel is in the right ratio to the air, you should get the same mileage under normal driving conditions. The throttle blade controls the size of the opening. So if the holes are bigger, the blade just doesn't have to be opened up as wide for the same cfm.

 

That would be true if it was a stock tpi. The tpi compared here was the expensive Scoggin Dickey setup with bigger edelbrock runners, bigger throttle body, along with other improvements.
Not exactly what I would have expected.

 

The SD intake is overrated. It's not a performance bolt on as much as just something that allows TPI to be adapted to vortec heads.
Your only as good as your weakest link. The plenum is still small and the TB is still small. The runners while better are still long and are still tuned for a certain RPM. Outside of that RPM the whole sin wave thing just hurts the motor.
I guess I didn't expect anything that much better.

 

The edelbrock runners are rated to 5500. Im not sure what edelbrock TB they used - it doesnt say. The SDickey dyno pulls to 5400 rpm.
I know these 'rated to' figures arent exact, but 5400 rpm isnt exactly high.

 

Thank you for embellishing, as I too am very familiar with Carburetion.... and I very much agree here. I was just pointing out that Carb equipped engines, after proper tuning of course, will get the same gas mileage to that of a TPI (if both employed a 305, and both had the same internals, were the same weight, had the same gearing etc...)), because a 305 is a 305. It burns 'just' the right amount of fuel that is required for it, with the only difference being that the Carb supplies it mechanically.

 

My bad, I see what you were saying now. Seems I didn't need to go into all of that. But it's kind of fun to talk about all this stuff anyway. Kind of helps to solidify the things we have experienced and observed with different types of fuel systems, and sizes instead of just theorizing.