OrangeC4

I have seen more TPI owners going to a Carb setup, and was wondering the advantages. Mainly because I was considering the same thing, but wanted to get some more information on it first. My first car was a Z-28 and I liked a lot more how the the engine was setup, a lot easier to work on.

randy814u

Me too.

vettmech

A proper running TPI setup is vastly superior to a carb. A carb CAN out perform a TPI for 1/4 mile or other racing but you will give up driveability and fuel economy. The TPI can be modded to run as good or better and still have resonable economy and driveability. I love mine and it's the first time in my life I haven't owned a carb of some kind and I'm DAMN good at rebuilding carbs and modifying them. If your TPI isn't doing what you want it to then let us know here on the forum........ a lot of people here know all about them.......... so In a nut shell the only advantage I can think of to a carb setup would be tha possibility of having that NASTY AA/fuel dragster idle.......... then ya need to run the guts out of it to clear the engine from flooding ......... :lol: :lol: :lol: :seeya

dlmeyers

Replacing fuel injection with a carburetor would be like removing the CD player and replacing it with an 8 track system. Yes, fuel injection can be more difficult when problems occur but the gains are usually around 20-30% in power and fuel economy, not to even mention emissions. Carburetors are basically wrong 99% of the time. They are set up for an average of conditions. And yes, in some applications, in certain motor setups, vary narrow applications, (like 1/4 mile dedicated cars), you MAY see a carb outperform fuel injection setup. It would be very very special. Duntov went to fuel injection for a reason.

It does take some additional effort to learn fuel injected systems, how they work, what components do what, but with a little reading and a basic understanding of combustion engines, it all makes sense. This list can provide and excellent reading list, and with all of about 5 manuals, you could become very knowledgeable and proficient with fuel injected systems. And yes, spending $600 for a used Snap On scanner (bidirectional and can work with about any car) is a pretty good chunk of money, at $75 an hour for labor these days, gets paid for pretty quick.

In summary, repacing a fuel injected car with a carburetor could simplify repairs. It would also loose performance and fuel economy. Resale value could be offset by just replacing the fuel injection when selling the car. If you have to pass emissions, no way.

You decide.

dlmeyers 90 coupe zf6 3 speed shocks

vader86

I can see why 84 owners would want a carbed setup, but not someone with an L98.

Carbed cars are always running either too lean or too rich, youll lose fuel economy greatly.

randy814u

Very good points. Thanks :seeya

yoslambo1@cs.com

:rolleyes: let me tell you first hand if you put a carb on your car you wont be dissappointed! just think no more stupid check engine lights, no more i computer, no more special tuning bs, no more stupid relays.....basically no more bs! if you really want to get rid of your headaches drop me an email i have some good info how to change your setup to carb. trust me you wont be dissappointed. :cheers: p.s yes fuel milage sucks but boy the car rips! :jester :p:

want2drivemy85

Orange, I went the carbed route and changed back to tpi. Yes there are more involved problems with the tpi (cpmputer controlled). But if you think about it, the money you spend switching over to a carb can also be used to upgrade to a 165 or 730 ecm and help with tuning issues on the 870. I spent 700 bucks switching over to a carb. Also I felt on my car that I lost alot of low end torque going with the carb. If you don't have problems with the puter, try porting your intake, larger runners, cam change, different heads, etc. You can get that car to run, just takes a little time and money. Good luck with whatever you decide! :cheers:

yoslambo1@cs.com

i think if you rejetted your carb you would have gobs of torque....i do. :yesnod:

J Z06

This is a touchy one. Lots like carbs, lots like fuel injection. I have had more problems with tuning issues(Stock ECM,re-burned chip) than I care to remember...and this is with Lingenfelter doing the tuning..so anything is possibe... NO ONE is above making mistakes.

A good example here would be a friends car, it is a 1990 IROC that had a LPE 383 in it a while back. It had minor idle search upon cold start, but that was resolved with a fuel pressure adjustment. In search of more power, my friend pulled that perfect engine(Which NEVER gave him a hint of trouble EVER...spark knock, oil consumption, tuning trouble etc, no problems) He took that engine and installed it in His "B" Car, an '82 Z28 ...but with a Holley 750 and Victor junior intake manifold. The engine is still quite strong(Still the same compression etc, 11:1) but it is lazier down low(Compared to the super ram that was formerly atop)...it loads up from time to time...and simply put isn't anywhere near as day to day tolerable as the 383-SR was(And it's been tuned by some top people as well).

All in all, if you think a carb is a set it and forget it, you couldn't be more wrong(That's my take from what I'd seen) EVERYTHING requires some fiddling to some extent. I will say a carb seems easier to tune due to less obstacles like this sensor and that sensor etc.

Just my .02 on this topic.

vetracer

It depends on what you want to do with the car. The first question I am asked at the races is why I chose a carb over the TPI. Granted, the TPI looks really cool, but I run a carb on my race car because it is a race engine designed to spin up to 7000 RPM. You don't see NASCAR cars equipped with fuel injection, either, as FI systems don't run well above 5500 RPM.



[Modified by vetracer, 9:14 PM 9/20/2002]

SPD DMN

It is because they are against the rules. If NASCAR went to a fuel injected setup, they would be even faster.

The main difference in Carbed versus Fuel injected is the first can be "tuned" by the local 60 year old mechanic on the corner, the latter has to be updated in the computer programming. The carbed setup will also not pass emissions testing which is fine if you are not in an area they test.

vetracer

But they won't run well above 5500 RPM. Winston cup cars turn 8,000+. My dyno sheet says 615 hp/545ft-lbs torque at 6400 RPM. Good enough for me, especially with a $1300 carb vs. thousands more for FI.

dlmeyers

Restrictor plates are hard to install on fuel injection systems. Have seen videos of tech folks checking plates during certain NASCAR events. Tech folks are very thorough. Don't have a clue how this could be done with FI.

dlmeyers 90 coupe zf6 3 speed shocks

JoBy

That is only because a carb is not smart enough to tell you when something is wrong.

AquaMetallic94LT1

Carbs are easier to maintain but do not have the driveability that fuel injection offers. Fuel injection can adjust for day to day changes in air temp, pressure and humidity. You'll find most successful drag racers monitor the weather conditions at the the track and change their carb jetting on a race by race basis so they get the most hp out of their setup for each race.

Fuel injection can also be tailored so that each point in an engines rpm band can be set to the air fuel ratio that gives the maximum safe power. Carbs must be jetted to keep the engine from going too lean at any point in the rpm band. Carbs air fuel metering can vary as much as 10% from leanest to richest as the air flow increases through the carb so the engine might be at 12.5:1 at a lower rpm point and 11.4 in the higher range. You'll see this kind variation if you look at dyno runs of carbureted engines.

Fuel injection computers also provide a computer controlled spark curve. Street engines require a spark curve that cannot be generated by a mechanical advance system. A typical street engine will operate better with a lot of advance at lower rpm, less in the middle of the rpm band and increasing and leveling advance in the upper rpm band. Part throttle requires additional advance based on engine load which can be controlled by the computer more precisely. Non computer controlled engines use vacuum advance to handle the part throttle spark advance but vacuum advance cannot generate a curve the will give the best part throttle performance. Spark advance is not as big an issue for drag racing engines because they operate at full throttle and run in the 2000+ rpm band. A mechanical advance system can generate the advance curve needed by a racing engine.

NASCAR teams would love to get fuel injection. It would eliminate the need to adjust the jetting on the carbs for every race and keep the engine air fuel ratio curve at the desired values throughout a race. The air temp, air density and humidity change enough during a race to give a fuel system that can adjust for those changes an advantage over carbs. There is no reason that a fuel injection cannot be used at the high rpm range that NASCAR runs. A team would just have to modify the carb intake they use now to take the fuel injectors, bolt on a plenum of the correct size and a throttle body to control the airflow to get the same airflow performance they have now with carbs. Consider that Formula racing cars run at 13000+ rpm and they are all fuel injected with systems that have wideband O2 sensors to maintain an accurate air fuel ratio.

AquaMetallic94LT1

390 cfm throttle body would do it or one with holes the same size as the restrictor plates.