Judge Ito

I took a customers car to the Dyno. A 1971 datsun 1200 with a turbo intercooled 13B on a Holley carburador. It took me 2 hours and 7 dyno runs to fine tune only 12lbs of boost. man I was so tired from taking off the carb. jets back and forth(the car was way to lean) when I finally got a nice mixture I could only go for 12lbs of boost. I know a carb. could be tuned to make some power, but man thank god for programmable Fuel injection. O and after all this tunning, I was able to pull out 320rwhp @12lbs of boost. I took my truck with a stock ecu and made 320@10lbs of boost..

Evil Aviator

Hehehe, I feel your pain. A few weeks ago my local carb guru set up my 1Gen. Screwing jets in and out, bending float tabs, and starting & restarting the engine just seems so archaic compared to simply bumping the injector pulsewidth up or down from inside the car. Gee, I can hardly wait until the winter when I get to change the jets out again and re-tune my 1Gen for the colder weather - NOT!

Judge Ito

I feel your pain too. On turbo engines FI is the way to go.

Evil Aviator

LOL, I would have ditched the carb on my 1Gen a long time ago were it not required for the racing rules. FI is the way to go on ALL engines, IMO.

AJC13B

Slightly off topic...but how do you change mixtures with mechanical injection?

Evil Aviator

I guess it depends on the system. All of the mechanical FI systems I know of are the CIS (Continuous Injection System) type, which basically leaks fuel into the engine constantly, with the leak rate increasing and decreasing based an a sensed airflow rate. On aircraft, I have seen the mixture controlled by either restricting the fuel return line, or with a valve on the metering jet. Also, some aircraft have automatic mixture control to compensate for atmoshperic conditions. I don't know how the mixture control works on automotive mechanical FI, but I guess it would be similar. Mechanical FI has many advantages over a carb, but you can't control the mixture every 125rpm or every 6% load like you can with EFI.

This may help:
http://www.auto-solve.com/mech_inj.htm

AJC13B

Thanks mate!!

silverrotor

iTrader: (1)

This Is the beginning of a LONG thread.

rxrotary2_7

i always wondered that about mechanical FI myself. nice link, i will have to look into that more indepth.

peejay

Other types of mechanical FI are basically mechanical RPM-TPS systems - they dump fuel in based on throttle position and RPM. As you can imagine, it's simple. Not the best way to do it, though, since the amount of fuel needed per cylinder changes at different RPM (representing the VE curve) so if you make it right for one RPM range it's too lean or rich at other ranges, unless you make the system more refined and therefore less simple.

Bosch K-Jet (aka CIS) is a beautiful system, originally quite simple when it debuted on the '57 Chevy and Corvette 283/283hp, then Bosch bought the rights to the system from Rochester after they gave up on it (dual quads made as much power for less money) and they developed it into K-Jet. Bosch added first Lambda (oxygen sensor) control, and then computer control, and it was used up into the 90's on cars like Audis and Porsche 911's. (Porsche was still playing with two-valve aircooled monstrosities on a vaguely updated Super Beetle chassis, so we'll forgive 'em for using a 40 year old GM fuel injection design... )

680RWHP12A

i lke carburators, they are way less expensive than efi and if you know what you are doing they work almost just as good.... my biggest complaint from the carburator guys is poor idle and excessive fuel consumption,, i jut remind them thats what happens with carbs but think of the money you saved!!! thousands!!! and they agree....ive used webbers, mikunies, nikkis, all with very good results....with experience carbs work great! my 12a nikki blow through setup made 540whp! if anybody needs carb blow through advice please contact me at www.rotaryshack.com

NZConvertible

Thousands?! Jeez, you need to shop around...

wickedrx2

you guys can complain all u want about carbs and say they dont do as much power but no one cant put down that the fastest rotary was a carburated turbo for years , far as tunning goes if u know what ur doing with a carb set up its pretty easy to tune just chabge some jets and ur running , its not that complicated a s a fi where u got to deal witha lot more parts

Evil Aviator

What "fastest" rotary are you referring to? All of the Racing Beat world record holding Bonneville RX-7's in the last decade have been fuel injected. The Kudzu and 787 race cars are also fuel injected.

So how many Indy cars are running carbs nowadays? (FYI, the year is currently 2002, just in case you don't realize it, LOL).

peejay

All Pro Stockers have carbs...

You can't really judge by what race cars use because race cars can only ue what the rules allow!

Saying "F1 cars don't use carbs" is pointless, because F1 cars are heavily regulated. For that matter you can use that same argument to say V10s are the best piston engine configuration. F1 uses fuel injected because that's what the rules say, just like Pro Stock uses carbs because that's what the rules say.

I don't race F1, I don't race LeMans, I don't race at Bonneville. I also don't race Pro Stock. I doubt anybody else here races any of those, either.

So let's dispense with all that BS and just look at the facts...

AJC13B

Nikki 4 barrel > All

Judge Ito

I think he is talking about the 1990 turbo II Rx7 that belongs to a fellow drag racer named "Rafaelito" this car has put down some impressive numbers on the old Cartech twin carb turbo set up. 7.66@177mph. We could debate all day about FI vs carb and they both have some positive out comes. But it's no secret Pound for Pound FI is #1 by the way. that Rafaelito turbo II Rx7 got so tired of fuel starvation(from small fuel bowl's designed for low boost) and hurting apex seals, that Rx7 is on his way with some FI. let the debate beggin..

Kenku

Actually, I used to have the technical regulations for Formula 1 around... IIRC, fuel injection isn't mandated. Circular pistons are, V-10 configuration is, displacement is, but I don't think fuel injection is. With the amount of computer controls on 'em though, I don't see it as being sensible to run a carb though. Especially given the budgets...

From what I've seen, FI is better if you have the budget for it and the ability to tune it. Which isn't to say that carbs can't make as much power, but across the whole powerband with good response is more tricky.

Now... I have no budget. So I'm going to be using a Nikki when I build up a spare motor. As much as I'd rather use EFI... well... I have something like half a dozen Nikkis sitting around. Will I get any less power with a Nikki? Prolly... I don't know how to tune it. Someone really experienced at carb tuning could probably get just as much power out of a Nikki as I could with EFI... but I can sit there with a laptop and tune EFI myself... and dammit, I'm going to stop ranting since it really doesn't matter and I'm just adding more fuel to the fire.

zyounker

FI is not more expensive then carb. It only is if you don't want to be a little inventive

Ok, converting a 12A to FI.

Megasquirt fuel computer ~$200
weber style maifold ~$300
TWM TB ~$300
injectors(2x$50)

That is roughly $900. Now how much do most of you spend on your weber carb & manifold? i know i spent about $800 for a nice one that was rebuilt.

Now with the weber setup after you purchased it, how much did you spend on extra jets or f-tubes, or the other parts you have to change out to tune???


It adds up to roughly the same in the end.. FI might be $100-200 more, but it will be alot nicer


-Zach

Kenku

Actually... been looking into that too. Sent a mail off to some people who do something like the Megasquirt, but customized... which, come to think of it, I don't really...

... argh. Yeah. Still don't have the money for a megasquirt right this second, but...


Thinking a little more... FI vs. Carb debate that I've seen in other places turned into a generation gap thing. Young ***** like me preferring FI because we love computers and understand them instinctively, and older folks preferring carbs because that's what they grew up with and know how to tune. But I'm probably overgeneralizing... my dad for example was completely mystified by the Nikki on the ITA car we have for quite a few days.

rxrotary2_7

i heard he was going FI a while ago...has anything hapened with that yet? does anyone know?

i remember seeing a rx2 from australia running 7's or low 8's with a draw through system...who was that? i could have sworn i saw it on a fast fours and rotary video... maybe i will have to pull them out and watch again.

Judge Ito

It's a done deal. the Rafaelito turbo II Rx7 is FI. Haltech 4 injectors N2o for now.. later i guess they will change over to alcohol fuel..

kabooski

Even you Ito have to agree when It comes to N/A

Holly Double Pumpers and 52mm Webers combined with Bridge can't be beat!

NZConvertible

Whether it's NA or turbo is irrelevant. EFI will still produce better overall results. Peak power (which seems to be all the carb guys care about) is about airflow, so whatever set-up flows the most air will make the most power. But even if airflow is equal, an EFI engine will have a much better spread of torque because of the considerably more acurate fuelling.
Replace that carb with a 50mm Weber-style double TB (which will outflow a 52mm Weber carb because there's no chokes or emulsion tubes restricting flow), or even better a 55mm one, and you'll have more power and torque, better driveablity, lower and smoother idle, lower emissions (if you care), no vapour lock, etc, etc.

Your carb just got beat!

RX-Midget

Lets see...
Used Weber 45DCOE - $100
Rebuild Kit for Weber - ~$40
RB intake for 6-port 13B(same as needed for above FI) - $130
Jets, e-tubes, chokes, ect - ~$75
Even trade with friend for a 48DCOE - Free

So for about $345, I got my project running. Yep it still needs a little more tweeking, but for me that is half the fun. Yeah, FI may give me another 5hp, but I'll take the hit (for now at least).
Now I have to think how I want to spend that extra $555......I already have the correct intake for the TWM TB and I'm in the process of making a direct fire trailing ignition, so I guess the Megasquirt would work. Hummm?