Dyno Day! Question for engine builders - A/F correction factor for dry dyno headers?
05-29-2014, 05:53 AM
#1
Dyno Day! Question for engine builders - A/F correction factor for dry dyno headers?
Engine is going on the dyno today. Unfortunately it does not look likely that I will be able to run my Lightning headers on the dyno, since they don't have provisions in the booth to run water to them. Scared my headers will crack if I run them dry.
Considering this, is there a correction factor or a specific A/F number that you look for when running an engine that will be a marine application? I do plan to run my flame arrestor on it, but in addition to the wet exhaust you also have the sealed off engine compartment in a boat (which I suspect is a negligible factor.)
What A/F numbers should I expect to see at idle, cruise (3000 RPM) and WOT? From the reading I have done on here from guys who are running them widebands on their boats, it appears that numbers in the high 11's and low 12's are OK to run in a boat. Sounds like numbers in the teens start getting a little lean and in the danger zone.
Also, what BSFC numbers should I expect to see?
For reference - 489 BBC, 9.25 CR, AFR 265 ovals, Dart oval intake, Lightning (or dyno) headers, stock T-bolt IV ignition, Holley 800 cfm carb. Cam is mild HR with specs in the neighborhood of 226/230, .612/.596, 114 LSA. It will run on the dyno with 89 octane pump gas.
Looking forward to your input.
Considering this, is there a correction factor or a specific A/F number that you look for when running an engine that will be a marine application? I do plan to run my flame arrestor on it, but in addition to the wet exhaust you also have the sealed off engine compartment in a boat (which I suspect is a negligible factor.)
What A/F numbers should I expect to see at idle, cruise (3000 RPM) and WOT? From the reading I have done on here from guys who are running them widebands on their boats, it appears that numbers in the high 11's and low 12's are OK to run in a boat. Sounds like numbers in the teens start getting a little lean and in the danger zone.
Also, what BSFC numbers should I expect to see?
For reference - 489 BBC, 9.25 CR, AFR 265 ovals, Dart oval intake, Lightning (or dyno) headers, stock T-bolt IV ignition, Holley 800 cfm carb. Cam is mild HR with specs in the neighborhood of 226/230, .612/.596, 114 LSA. It will run on the dyno with 89 octane pump gas.
Looking forward to your input.
05-29-2014, 06:47 AM
#3
Registered
iTrader: (5)
If your running the flame arrester I imagine they won't be using a flow meter for airflow through the carb. So if your using a wideband 02 in the exhaust if look for 13.1-13.3 a/f on the dyno and it should be 12.6-12.8 in the boat when you put your exhaust on etc. as far as bsfc I don't think high .3's-.4 is out of the question
Last edited by Unlimited jd; 05-29-2014 at 06:54 AM.
05-29-2014, 06:52 AM
#4
Thanks for the help, anyway!
Last edited by Budman II; 05-29-2014 at 07:02 AM.
05-29-2014, 06:53 AM
#5
If your running the flame arrester I imagine they won't be using a flow meter for airflow through the carb. So if your using a wideband 02 in the exhaust if look for 13.1-13.3 a/f on the dyno and it should be 12.6-12.8 in the boat when you put your exhaust on etc. as far as bsfc I don't think high .3's-.4 is out of the question
Gold Member
05-29-2014, 06:05 PM
#9
Results are in!
We made several runs making various adjustments to timing and carb jetting. Last run of the day produced peak HP of 584 @ 5500 RPM and peak torque of 605 ft/lbs at 4750 RPM. Engine had a broad, flat torque curve with 604 ft/lbs available at 3250 RPM, and 580+ ft/lbs all the way from the start of measurements at 3000 up to where we stopped at 5750. This was with dyno headers through the stock flame arrestor, with alternator and water pump being driven. All in all, I am pleased. I'll post the sheets and details later on. Need to get this thing unloaded and in the garage before rain gets here.
