g.orruņo

Hi!! someone knows a 928 with carbs???
what is better? carbs or throttle bodyes??
thanks

SQLGuy

Carbs are easier to modify without needing knowledge and tools for software and electronics, but, IMO, they are otherwise completely inferior to fuel injection.

Fuel injection can provide exactly the right amount of fuel, reacting faster to changing conditions, and correctly compensating for changes in temperature, altitude, engine load, and even octane. Carbs are (early) last century technology; when they're exactly right, they're still an approximation, and they don't react well to even such things as sitting for a couple of weeks, let alone driving from my town (at 6000 feet elevation) up to a relatively nearby town (at 10000 feet elevation).

g.orruņo

but if you have a 6 litre engine with carbs and 6 litre engine with throttle bodies... who have more hp??

Mongo

Most setups that look like 'carbs' are individual throttle bodies, or ITBs. Standalone engine management systems are almost always applied to these setups.

markiii

the one with the better tune

g.orruņo

thanks

IcemanG17

they should be close to the same HP.....BUT the injection system will maintain that power level for longer with wider variation in weather-altitude etc..... The injection also has the ability to run knock sensors for an even higher state of tune...to achieve even more HP, but with HUGE amounts of time to get it right

SQLGuy

If everything is done correctly, the fuel injected one will always have more horsepower.

Even if you pick an RPM and load where everything is perfect for the carburetors, the fuel injection system can deliver exactly the same fuel at that point, and without the drag of pulling air through the venturis, and without taking up volume within the intake runners for fuel, and with the ability to time injections for better valve cooling and better atomization.

But, if you have a modified engine, and you don't know enough about how fuel injection works, and don't know how to create or modify engine management software, then you'll probably have a better chance of getting good power out of that engine with a carburetor than you will by having the stock fuel injection DME try to figure out what your modified engine is doing.

g.orruņo

i am boing a 6.5 litr engine, i have haltech ecu, by the moment i dont have problem, but when i finished my engine and i have to program the ecu.... i can find some problems...because i never program a ecu jejejeje

123quattro

This actually isn't true. In any port injection engine, the fuel is displacing some incoming air. Only in a direct injection engine where fuel is injected into the cylinder after all the intake/exhaust valves are closed do you not displace incoming charge air.

Lizard928

German,
Tuning the car with standalone EFI is the easy part. Getting it running first is the hard part.

SQLGuy

I was talking about displacement in the runners, not in the ports.

With port injection you are still going to have the benefit of air-only in the runners and you are going to have a lot of atomization taking place right at the back of the intake valve, with the fuel being higher density until that point.

Also, if you're running sequential injection (which, yes, I know, the 928's don't), you'll be injecting the fuel into about a 2 cubic inch volume of non-moving air. Then, when the intake valve opens, you'll pull in that fuel, very recently vaporized by the heat of the intake port/valve, along with that whole column of dry air from the runner. Direct injection will still have an advantage, but it's not as big of an advantage as the one port injection has over TBI or carburetors.

hacker-pschorr

The highest horsepower OEM applicaitons (L88 Corvette is one example) all had a four barrel over ITB's.

Thre are different theories as to why......

SQLGuy

My experience has been the opposite. Getting it running was relatively easy. Tuning has been a never ending story... there's always at least one more thing you want to tweak/improve. As one of the guys on the MS forum put it: once you get into to tuning, you'll start swapping out parts just as an excuse to tune, and you'll start criticizing OEM EFI systems as to what they could have done with, for instance, a bit of extra accell enrichment, etc. ;-)

After running my MS setup for two years I recently went back and built a new intake manifold and fuel rail, just to see if that would clear up some of the tuning issues I was fighting. That chapter is still in progress....

SQLGuy

Historical, non-emissions, and non-SAE NET rated power, seem to me to be questionable examples.

Honda gets 240 modern HP out of a 2 liter normally aspirated engine in the S2000. Do you think they could do that with carburetors? Maybe, if they didn't have to meet emissions requirements... but they still would get less drivability and less total power under the curve.