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Old 08-29-2015, 05:47 AM
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I bought a F.A.S.T. system for mine and monitor all the time, not sure what Joe uses.

Originally Posted by BBCLiberator
So what wideband do you use?
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Old 08-29-2015, 08:21 AM
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Originally Posted by BBCLiberator
So what wideband do you use?
I have a portable NGK powerdex unit. It is very basic, with an easy to read large display, a calibration mode, and uses a NTK oxygen sensor. Most use bosch sensors. I used it on several engines, including my own, and have good luck, still on the original sensor. Downside is, NGK is no longer making it. There is another company making it now.

http://www.ebay.com/itm/Ballenger-Mo...a3bd58&vxp=mtr

Lots of options though out there. AEM, Innovate, Fast, etc. The Fast meter, is available with dyno cell cables, which are longer, and work well for boats with long run of 22ft cables to the dash. #170602 These guys seem to have the best price on it from what I have seen on the web.

http://www.dfperformance.com/airfuel_meter.html
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Old 08-29-2015, 08:57 AM
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Originally Posted by MILD THUNDER
I have a portable NGK powerdex unit. It is very basic, with an easy to read large display, a calibration mode, and uses a NTK oxygen sensor. Most use bosch sensors. I used it on several engines, including my own, and have good luck, still on the original sensor. Downside is, NGK is no longer making it. There is another company making it now.

http://www.ebay.com/itm/Ballenger-Mo...a3bd58&vxp=mtr

Lots of options though out there. AEM, Innovate, Fast, etc. The Fast meter, is available with dyno cell cables, which are longer, and work well for boats with long run of 22ft cables to the dash. #170602 These guys seem to have the best price on it from what I have seen on the web.

http://www.dfperformance.com/airfuel_meter.html
First off, great read! I am planning to buy new carbs this fall as I absolutely hate the demons. I will also be adding bungs for O2 sensors.

Silly question - do you run 2 AFR screens at once or move them back and forth between engines? I see they have a 2 sensor option but I assume that's two sensors per engine (both exhausts)?

Thanks
Jim
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Old 08-29-2015, 09:49 AM
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Hey Jim. I would run both sensors on one engine. Find out which side runs leaner. Tune off the leaner bank. Then do other engine. Once you know lets say your odd banks are the leaner ones, you can then install your sensors in each engines leaner banks for further tuning.

Carbs are certainly not as good as port efi as far as optimizing fuel mixtures , and cyl to cyl distribution. But they can be made to work well, and be user friendly, and reliable. Later i will touch base on supercharger carbs.
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Old 08-29-2015, 06:41 PM
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Originally Posted by MILD THUNDER
Yes, Really helps when you are running a long duration camshaft. Thats one of the nice thing about some of the new programmable ignitions from Daytona sensors, msd, etc. You can have lots of timing at idle, bring it back once off idle, then bring it back in gradually, or quickly, or based on a map sensor value, etc. Locked timing is cool for idling, but on certain setups, can really cause issues.
Can you lock out the timing with the DUI distributors?
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Old 08-29-2015, 10:56 PM
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Originally Posted by MILD THUNDER
I have a portable NGK powerdex unit. It is very basic, with an easy to read large display, a calibration mode, and uses a NTK oxygen sensor. Most use bosch sensors. I used it on several engines, including my own, and have good luck, still on the original sensor. Downside is, NGK is no longer making it. There is another company making it now.

http://www.ebay.com/itm/Ballenger-Mo...a3bd58&vxp=mtr

Lots of options though out there. AEM, Innovate, Fast, etc. The Fast meter, is available with dyno cell cables, which are longer, and work well for boats with long run of 22ft cables to the dash. #170602 These guys seem to have the best price on it from what I have seen on the web.

http://www.dfperformance.com/airfuel_meter.html
Cool thanks, who installed your bungs, and do you have pics?
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Old 08-30-2015, 02:51 AM
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Originally Posted by MILD THUNDER
Hey Jim. I would run both sensors on one engine. Find out which side runs leaner. Tune off the leaner bank. Then do other engine. Once you know lets say your odd banks are the leaner ones, you can then install your sensors in each engines leaner banks for further tuning.

Carbs are certainly not as good as port efi as far as optimizing fuel mixtures , and cyl to cyl distribution. But they can be made to work well, and be user friendly, and reliable. Later i will touch base on supercharger carbs.
Joe, what bank on your motors is running leaner, if at all?
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Old 08-30-2015, 07:56 AM
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Originally Posted by Bawana
Joe, what bank on your motors is running leaner, if at all?
On mine, they are actually almost dead nuts. But, I think that is due to the straight lobe blowers. When I ran the Fast dual channel better, the banks were just about .1 to .2 max different from each other. However, some engines, can be off quite a bit from bank to bank. Plus, cyl to cyl. Since the AFR is taking an average of the 4 cylinders on that bank, we gotta remember, that while the meter might show your target AFR number, but certainly can have a cylinder running leaner or richer than that number.

Its been said, a gasoline engine makes it best power at 12.5 AFR. Thats on pure gas. Throw ethanol blended fuel in, and now that number goes down, or "richer". Icdedppl's blown 540's were a good example. We always dyno tuned our stuff, with our own fuel. We go to the local shell or citgo, and that is what goes in the dyno's fuel cell. His engine, simply made the best power, with an AFR of 11.5. We tried leaner, we tried richer, and power wise, 11.5ish was the number. So the old theory that "lean is mean", etc, doesnt hold true for all engines.

A port injected, precisely tuned efi system, can certainly get away with leaner afr readings at the collector. With a carb'd engine, or throttle body EFI, I'd be careful chasing internet textbook afr numbers. Currently, my engines are 11.1-11.3 at wot. I tried leaner, gained nothing in power or speed. I mainly run ethanol blended fuel, as thats all we can get around here.
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Old 08-30-2015, 08:56 AM
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To touch base a little on supercharger carbs...

This is an application, where you really don't want to cut yourself short on carb CFM. One thing superchargers like a roots, don't like, is a restriction on top of the blower. For example.

Your buddy builds a 540 with an 8-71 blower setup. He makes 850HP, with 7lbs of boost, 12% overdriven, and a pair of 750 carbs. Your other buddy, builds the exact same engine, but using a pair of 1050 carbs. He's making 7lbs of boost as well, but blower is only 3% overdriven and made 875hp.. What happened here, was buddy #1, was undercarbed, and to get the boost he wanted, he had to drive the blower harder. We all know what happens, when you spin the blower faster, more heat.

Using this BDS blower calculation figuring 7lbs of boost and 6000 rpm {(CID x RPM) ÷ 3456} x {Boost ÷ 14.7) + 1} = CFM required. Most blower shops, say going as much as 30% larger than "required" is acceptable.

454ci=1163 CFM + 30%= 1511 CFM (twin 750s would be my choice)
502ci=1285 CFM + 30%= 1670 CFM (twin 800s would be my choice)
540ci=1383 CFM + 30%= 1797 CFM (twin 850s would be my choice)
572ci=1465 CFM + 30%= 1904 CFM (twin 950s would be my choice)
598ci=1532 CFM + 30%= 1991 CFM (twin 1050s would be my choice)

Thats a mild setup. How about the guys running more boost? Today with intercoolers, guys are running 9-10lbs of boost, and some are turning engines even faster than 6000. So lets look at a 6500RPM, 10lb boost deal.

454ci= 1433 CFM +30% = 1863 CFM (pair of 950s would be my choice)
502ci= 1586 CFM +30% = 2062 CFM (pair of 1050s would be my choice)
540ci= 1706 CFM +30% = 2218 CFM (pair of 1150s would be my choice)
572ci= 1807 CFM +30% = 2349 CFM (pair of 1150's would be my choice)
598ci= 1889 CFM +30% = 2456 CFM (pair of 1250's would be my choice)

Now, some might read these numbers, and call bs. And it they may be. However, when I look at this stuff, I kind like looking at what mercury racing did in their choice of parts. One thing about mercury racing, is cost is not an issue, and their team certainly spent lots of time with R&D on their engine packages. While very outdated, the old 900sc, and 1000sc merc engines, were 540ci, 6000RPM, running 10-12 lbs of boost. I am sure they tried several carb variations. They could have put any set of carbs they wanted on top of those engines. They put a pair of 1050 dominators on them. I would like to believe, that they did it for a reason. It certainly wasnt for cost, it certainly wasnt for fuel economy. Even the 525sc, the little 454 with 177, that turned 5200RPM, got a 1050 dominator. The numbers I posted, would be right in line with that. (it would have called for 915CFM minimum according to that calculation, and 30% larger would have been 1189 CFM). So you can see, its right in that range.

I know of several guys, who have swapped out smaller carbs, for larger carbs, or even throttle bodies when converting to EFI in one case, saw a gain in boost pressure, without changing pulleys. They had to slow the blower down, to get their boost back in line. This is why I cringe, when I see guys running a 250 blower, on a hot 502, or 540, with a single 1050 carb. Now, can you make big power with smaller carbs, of course. And if going to a larger carb nets nothing, than obviously no point in changing. But, don't spin the blower any harder than you have to. Let the carbs move the air in, not the blower sucking it in. A vacuum gauge under the carbs is a nice tool here.

Remember the big argument of needing boost referenced power valves, so the PV doesnt get "sucked" close at high rpm? Well, that is not an issue, if the carbs are properly sized. If you are ever pulling 4, 5, 6 + inches of vacuum under your carbs at wot, you are severely undercarbed. it was a reality back in the day though, when guys were building bigger engines, cranking the boost up, and trying to run a single small carb to feed it.
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Old 08-30-2015, 04:57 PM
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Originally Posted by Craney
Can you lock out the timing with the DUI distributors?
yes, I run mine locked, seems weird but I removed all the advance weights/springs and used mechanics wire to lock it and twisted tight rotor back on and works fine...
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