As joe did, we did mine slow rate also in marine trim, that was as accurate as we could get, still changed a lot putting them in the boat mid summer I see low 11 air fuels sonetines a high 10, I am rejetting This week glad I have widebands to keep eye on that, I recommend that on any HP boat.

http://youtu.be/F5sQmgFHOf4

How many of you see a huge change in boat over dyno o2?

Most dyno shops dont simulate part throttle loads. They simply do a full throttle pull, and call it a day. That does nothing for part throttle fuel tuning.

Ryan Retter allowed us to bring the engine up to certain rpms, and partially load the engine and monitor the air fuel ratios, etc. For example, 3000rpm and 0" , 3500rpm, and 2psi boost, etc

From what Ive been learning over the past couple years, is that , a dyno tune on your engine, is only as good as the operator,tuner, and equipment they have. Slapping an enginr on a dyno for unrealistic sweep rates, questionable data acquisition, and 30 year old tuning techniques, is pretty much a waste of time. And in the wrong hands, can do more damage to the engine than its worth.

That was 150 per second starting around 2800rpm to 6500rpm. . We ended up going to 300 rpm per second i wanna say on the next engine. I felt the 150 per second was a bit extreme. My boat would never accelerate THAT slow.

We held mine at peak TQ for how long to monitor A/F? Like 3 minutes just held it there.. That was good to see stable A/F throughout.

Thats why i am so happy to have a dyno in.my own shop now. Mine has manual brake control, i can mimic the way it accelerates in the boat real easy and the 550 hp 502 mpi i just built and dynoed i did numerous part throttle pulls hitting map tables from 40 to 100. By doing this i didnt have to spend 10 hrs driving around in the boat tuning w the laptop. I did all my tuning at 50 psi of fuel pressure, when installed in the boat the tune was a little richer than i wanted almost everwhere so i was able to lower fuel pressure about 5 psi this making "global changes" to get afrs where i wanted with just some small tweaks here and there, Smitty

I may have missed it somewhere in your other post however are do you have wideband o2 installed in your boat? With where your currently running AFR's I believe your engine will like the cooler temps without a concern. I'm probably old school but along with wideband I still like to do plug checks from time to time on hottest cylinder due to equipment failure or possibly inaccurate?

I mentioned earlier regarding seeing extremely high EGT's while jetting was overkill. It was one of my learning days many years ago on BBC with a 420 mb. In a nutshell the the EGT's were so high from way to much fuel/jetting. Fire was blowing out of the hole (exh port) so to speak. Had to bring jetting way down to get numbers where they needed to be. Initially it was a real head scratcher with seeing such outrageous EGT's yet the plugs showed extremely rich. Would have been caught much quicker if the wideband would have not malfunctioned via day one.

What did your engine builder say about your AFR's currently vs when in the boat?

I had egts in my lightning headers years ago in my supercharged Baja and when you got the afrs into the mid 11's the egt temps were past aluminum meltdown (1600+), seen that again since then on dyno when making blown pulls too so to me I dont even bother running them on dyno as they give false results, Smitty

I do have O2 in the boat so I will be able to check/ compare. We haven't discussed changes to be made after installation. I'll probably have to start another thread...

If EGT`s are too high with a rich mixture I`d say it doesn`t need less fuel but may need more timing to burn the fuel off.
I saw lower egts with more fuel. Pulled 4 jet sizes EGTs went up.