shouup

im undecided on if i should purchase a 350TPI car and start modding or if i should get a 305 rs and buy long block to swap in over the winter. To get a nice looking 350TPI camaro im guessing ill have to spend upwards of 5-6k whereas a 305 rs i could spend 3-4k and put the other addition 2-3 in a 355 long block. I would like to go tpi, but like most people, im all about performace. It seems the tpi guys have trouble hitting the power marks that the carbed guys are achieving in ease. Is this correct or am i comparing the wrong cars?

jrg77

Get the car that is in the best all around shape. Chances are it will be a TPI car. for a few more hundred dollars you can changes intakes and be at the cutting edge of third gen tech (aside from dropping in a LSx).

You will save yourself some hassle by starting with the fuel system you want to use. Changing systems can get pricey, and time consuming chasing down wires and connections.

Have fun.

Jason

shouup

i have no problem with carb, my last mustang was carbed and i loved it. i know how to work on a carburated car where as fuel inejection can lose me kind of quickly. Basically i want to go with whatever will give me the most power. Will carb of tpi give me the most power in the end? even with and HSR intake and heads some 3rd gen owners with 350's are only pulling off 13's....thats seems a little slow to me.

Bunker82

You know how to work on carbs, don't really know FI, want max hp, and want it to be inexpensive. Sounds like carbed is the way to go for you. "In theory" FI makes more hp, but I have never seen convincing evidence of this in practice. FI's advantages come in everyday street manners, but even then, a well tuned carb can come pretty close.

shouup

yeah, i always here that FI is better for max HP also...but looking around at quarter mile times it seems like carbed guys are doing better and getting ALOT more HP with their combo's. Maybe it has something to do with the years behind the design of the carbed intake compared to the FI? maybe not...its just a theory. Anyways, i think i will be purchasing a 305 tbi rs and dropping in a 355 gustaf log block. Its only 300HP but that can be changed with better heads. Thanks.

jrg77

The whole thing with EFI is precise fuel metering in relation to the use and environment. That translates to a brader power range, better fuel economy, and lower emissions. If you are looking for max effort only then going carb is better simply because the industry has more experience with it and the costs are cheaper. IF you want the performance around town, on the highway, AND at the racetrack without enormous adjustments before each excursion, or spending gobs on wasted gasoline, then EFI is a better choice.

Jason

Kevs87Z28

well under that statement what are carbs even around for? IMHO the only thing FI is good for (besides wasted money on PROMs, Sensors, and intake upgrade after upgrade) is MPG. if you truelly want power and dont mind knocking off a few MPG then do what almost all drag cars do....carb it.

jrg77

Proms = Jets Everybody has more than one
Sensors help you keep from detonating it (which can happen with either BTW if you don't tune appropriately)
Folks have just as much of a challenge picking their intake/carb combo as the intake/throttle body in EFI.

Like I said the reason it is still around because there is a long lead time on the learning curve. Way more people have done it with carb. If it is easier is is simply because someone is able to point you in the right direction. To get the tune correct you still need to check your A/F ratio, and you still want to listen for detonation and monitor your timing. EFI just makes the tools work together.

It was stated in the beginning that he wanted to go TPI. I don't know why, but if that is indeed what he wants then it is cheaper to start out with that then go from one system to the other. Power wise it really does not make a difference. The difference occurs when your want to do something else other than race.

I don't have a preference at all. My car is carbed now. Start in the direction you want to end. That is all I'm saying.

Jason

Kevs87Z28

well speaking from somone who has a 305 tpi i say carb it. tpi has a lot of low end but up high at highway speeds if you try to get into it, it is very slow going. at least in my all bolt on 305.

either way tpi is like a brick wall when real performance is desired. once you swap to hsr or superram its not tpi anymore but they still have their limits as well. most people arent out to make the power to exceed the limits of these tpi-look-a-likes though.

I am spending a fortune swapping to carb and a 350. i wouldnt be doing it if i liked tpi. at first i did but after a few highway races agaist friends for giggles and no danger other then to ourselves, i quickly saw the lack of power up high.

its not very often on the street that a civ!c or something will wait until the next light for a race so low end only matters at the strip or a light. anything from a roll and you stand a good chance of loosing.

besides for the money you spend to get a tpi car, then swap the intake/TB to something aftermarket, then get a custom prom, and sensors breaking all the time and codes driving you nuts; you can get a carb car, upgrade to aftermarket, and come out with money to do exhaust, suspension, appearance or whatever you desire.

CARB CARB CARB

Nihilanthic

Not trying to fan the flames too bad here, but there are EFI systems you can put in that wont kill top end...

Like, holley has a TBI kit. Basically it bolts where a carburator would, so you get a quick and dirty TBI. Easier to use, blablaba, but expenxive.

There are also multi port injection systems... pre-drilled manifold *bungs for the fuel injectors* and the fuel rails and all that good stuf.

Personally, I have no prob with it, but its expensive! I wish the TBI system was cheaper, I'd like that over a carb for just ease of use and the fact that it doesnt get messed up with high gees or need all these linkages and pins for the secondaries that tick me off. heh.

Barry85Iroc

If you want to make horsepower.....look at what the pro's run. Carbs make more power.

Nihilanthic

well what is the advantage of a carburator then, besides being cheaper?

Kevs87Z28

what he said.

fuel injection in whatever form is expensive, time consuming, and just overall a big headache. when you start desiring performance and money is involved it is more efficient to go carb. fuel injection is only good for gas mileage. prom burning is an advanced skill and again cost for equipment for a DIY can be costly. so to sum it up...

carb=cheap, ok gas mileage, easy to tune/operate, limitless, no start? must be spark or fuel... gettting fuel..... oh look a fouled plug or hey no coil spark....nice

fuel injection=$$$$, special equipment for tuning, good gas mileage, limited power, codes, sensors, having your car shutoff at 80 on the highway (my experience) over a maf power relay then spend 100 buck to tow it home and spend hours checking then find out the cause is a 6 dollar relay...sucks

Kevs87Z28

end rant

Nihilanthic

.... why does a carburator make more power, and why would EFI be somehow a bottleneck? Flow or A/F ratio?

Also, what about how carbs get messed up at high G-forces or being at a weird angle?

jrg77

They are all expensive. It just depends what you want to accomplish.

My introductory experience with carbs matches some of the challenges mention above. Just change relay to vacuum hoses.

The pros run carbs because the rules say run carbs, and they are making enough power to not really need to change. The other reason is that EFI lets you set stuff up and bury it in the code. It is a lot harder to police cheating when a code controls something rather than a physical part. If the rules allowed it believe the pros would run it.

The fastest cars on any track you pick that has had both formats at the top of their game has been and always will be EFI. You can simply control the combustion better over a broader variety of variables and make consistent power.

The C5R Le Mans car Definitely does not use carb. And I bet it is just as fast around any course in common with NASCAR.

That Cadillac CTS-V is not carbed, and probably shouldn't when trying to race against Audis and BMWs.

Racing's orignal intent was to demonstrate cutting edge ability to go fast reliably. The cutting edge is EFI. The fact that there's a learning curve does not indicate that it is inferior, just earlier in its development. Imagine what EFI will be when there is as much time in it as there is now in carbs.

Think about it. A streetable emissions legal 500 HP Corvette is on our doorsteps that revs all the way to 7000rpm. You can NOT do that with a carb, even at the same displacement, and certainly not at the same price. If you could then there would be no need.

EFI represents something very simple. Change. The things that survive the longest aren't always the strongest. Most time ots the most adaptable.

Later

Jason

BT283

iTrader: (3)

Carbs are the way to go fast. If you have TPI and decide to put a head and cam package on it, more than likey you will blow it up before you get it to run right. I have a carb on my 91 rs and it runs 12s and only a Trick Flow heads, .470 lift cam and a busted 700 but on the other hand it is cooler to out run people with carbs on EFI

Nihilanthic

Dude... comparing a carburator to a TPI manifold is apples to oranges.

TPI is batch-fire MPFI. However, the INTAKE MANIFOLD is set up for low end torque. If you got a 0-5500 rpm manifold and a carb on it you wouldnt have a high revving supeerpowerful car either.

I'm talking about the same everything, but one has a carburator, and the other either has a TBI, or a suitable throttle/air meter thing where the carb or TBI would go, and 8 injectors in the manifold, fuel rails, etc.

you can drill bungs in a carb manifold for EFI, and then replace the carb with the throttle plate assembly and the air metering thing. MAP or MAF or whatever.

Comparing a well set up carburator to a TPI that was good for its era but sucks by modern standards (didnt breathe well at high rpms, batch instead of sequential fire, yadda yadda yadda) is apples to orange dude.

I was asking if Carbs have any advantages to a properly set up, COMPARABLE EFI setup, besdies budget.

jrg77

The specific answer to your question is no. The reason is very simple. You can manage the air/fuel ratio to a far tighter constrant with EFI. When givn the proper airflow you can match the fuel requirements over a broader rpm range and thus make more power under the curve. That fact that you can get better gas mileage, and lower emissions is a plus. Even before the gas crisis and EPA they were trying to do fuel injection.

It is all left up to your wallet now.
Jason

Nihilanthic

alright, now what I wanna know is....

just how much woudl a TBI or a MPI kit cost, anyway?

I'd maigne the TBI would be cheaper, except that the injectors it has would necessarily be larger than individual MPI ones... and the MPI would require its own pre-drilled (for the injectors) manifold to go with it.

I guess getting a megasquirt ECU and JY injectors would make it a hell of a lot cheaper, lol.

Still, any quotes? If TBI isnt that expensive I might as well get one rated for the HP my engine is gonna put out and pop that sucker on top of my damn intake manifold - but what kind of gain would I actually get? The carb works great now for driveability and throttle responce, believe it or not. Mechanical secondaries and a stick are awful nice. Would I save with fuel economy enough that I'd get a return any time soon?

CaptPicardsZ28

If your going to go with tpi and plan on modifying it at all, plan on buying your own prom burning equipment and doing it yourself. Took me 16 months to find out my chip was burned wrong buy a reputable company. After I bought my own equipment my cam went out due to fuel wash because of the incorrectly burned chip. I spent 2700.00 on EFI including HSR setup and prom burning and decided after the cam went that I was tired of trying to tune it. Switched to carb and it cost me 2500.00. Sold all my EFI stuff for 2K. I am not sorry I did it. TPI intakes will basically flat line at 4500 rpms. They are not made for more than that. If its just a daily driver stick with tpi. Just my

Sorry if I'm a little late getting in the discussion...

HorseflyDF

My 89 celica GTS
has a fuel injector to each cylinder.
and I can rev to 6500-7000 with the automatic tranny.
When It reaches 4000 rpms there are butterflies
in the intake runners that open up and it superchargers
with the additional rush of air.
Is the reason for this because its overhead cam engine
that it can rev up so high and not bog out?
My camaro bogs out when I try to go wot everytime,
at highway speeds.
4bbl holley . vacumm secondaries.
When I gradually step on the throttle its ok. (700r4 tranny.
with 2.73 rear.)

Nihilanthic

The butterflies just change if one or both intake valves allow air to flow in. This way it can maximize velocity at low total airflow so it makes higher torque at lower rpms, but not RESTRICT (let both flow) at high rpms. Toyotas done that for a while.

Also, being EFI, it perfectly regulates fuel spray to go with the air flowing in.

Vacuum secondaries dont really do that very well I dont think. I got mechanical secondaries on mine and a manual and it never really bogs on me.

But yeah, vacuum secondaries are just 'cracked' open and let engine vacuum suck them open further. Also, a vacuum secondary carb (or even a mechanical one if you use your foot properly!) use a similar trick to what your toyota uses to help make sure it limits the area air flows through when its at a low total flow to maximize velocity (and vacuum) when at that low flow, but then let it open up more when the flow is so high it would restrict going through the two smaller barrels (or just one intake port).

Carbs need vacuum pulses to regulate how much fuel is drawn out of it. Thats why the two small ones are used for daily driving or just low load conditions. "Rolling on" lets it actually begin to suck hard enough that it creates the proper vacuum in the carburator to suck the fuel out.

Yeah, physics is a bitch, but if you tune it right you could get around it.

And it seems other than price and some difficulties, EFI is the way to go.

Barry85Iroc

Yeah, if you got DEEP pockets. You'll need a computer to tune it, and to tell you what's wrong...........If you can get a sponsor (someone to foot the bill) EFI MAY be the way to go.