bck

I imagine there are a few ways to do this but I just wanted to get some input. Everyone always mentions tuning by afr but my builder says he's lost a few engines relying on them. His procedure was mainly to richen the mixture to where he got the exhaust gas temps where he wanted them. Generally 1400 or less. Then he fine tuned by reading plugs on the hottest cylinders and adjusting jets to get bsfc numbers where he wanted them. He was shooting for getting bsfc numbers in the .4xx range. So my egts are all around 1400 max after the pulls, bfsc was specifically calibrated to be in the .4s as much as possible and plugs were checked a few times to verify. Afr ratios ended up being in the 10s and 11s a lot using this method. They have a 1 yr warranty so I'm not inclined to screw with them. Just interested in this tuning method from people with more experience.

underpsi68

I used to tune my blown street car using an egt gauge, that was before wideband's were affordable. IMO the problem with tuning by targeting a certain temperature is timing affects exhaust temperature,as well as other variables. Retarded timing will raise egt. I would use the egt gauge as another tool to tune, not the end all.

I'm a nobody but I would tune it on the dyno. The engine will dictate what it wants for a/f and timing. The plug ground strap will tell you where the timing should be.

getrdunn

iTrader: (7)

This will endure being about 28 1/2 pages. Lol. I always use to look at EGT's and AFR's of course with first pull or two primarily focused on EGT's with concern of Pistons turning into the cop on terminator. Problem is when trying to achieve maximum power EGT's can vary several hundred degrees from one engine to another. While on the other hand AFR's will typically make most power with a much smaller window btwn 12 - 13 plus to 1. Both are a great tuning great tuning tools however id lean toward AFR's but that's just me. On the dyno my eyes are dialed in on both with equally importance including BSFC. Ground stap on the plugs are equally important if not one of the most while tuning. That's one thing that don't lie or can ever give off false readings etc. EGT's can easily get thrown off showing extremely high temps from being to rich. Trust your engine builder. He sounds a tad conservative however wants to keep you on the water rather than in the bilge.

bck

It wasn't exclusively egt, but that was one of the first steps. After egts were good, after plugs had been read it was mainly tuned using brake specifics. The O2s just ended up where they were after checking everything else. We did actually lose a few hp while richening it up. He said he was happy with the power / safety margin compromise.

bck

Out of the box was 701 @ 5800 and 670 @ 5200. Ended up losing a bit with jetting and flame arrestor. Hopefully this is the last time this engine goes near a dyno.

https://youtu.be/kjPX-KA4n54

getrdunn

iTrader: (7)

Sounds nice. What cubic inch, intake and heads again? If I remember right 540 plus/cnc 305 or 315's and Edelbrock jr, Bob M cam. Can't remember from old thread you did. I'll bet your glad it's done. Regardless time well spent.

Btw did it like the 1050 the best and did you try 1150 or 1250 by chance.

ICDEDPPL

iTrader: (1)

Tuning on the dyno is nice to get you in the ball park but in the boat is a different story. Unless you drive like a dyno pull.. full throttle from a dead stop everytime
I had to pull 4 jet sizes in the boat because cruise was too rich, mid 10`s (great on the dyno).
4 jet sizes= 100* hotter EGTs, which isn`t much (1340* @4000) (Extra fuel extra cooling Id guess)

Too many factors that affect EGT`s readings to use those numbers to tune IMOP but it is one more thing I use ( along with knock sensors and AFR`s) to monitor what the engine likes as far as timing and fuel or if anything is going avry.

bck

You got the specs right. 305 heads. 454R intake. It liked the 1050 Dom much better than the 986 4150. Went with the QF marine Dom and Daytona ignition. Made within 2 hp of what it made back in Feb with the Crane box and automotive carb with the smooth radius throttle bores. Did not have an 1150/1250 to try. ICD, the boat has O2s so I should know if it changes from the dyno. Most of the fine tuning was done using the bsfc. He wanted it in the .4xx, didn't pay much attention to O2 at all.

MILD THUNDER

iTrader: (3)

I personally, would not use brake specific fuel consumption measurements, to get a tune. It tells you nothing about the actual fuel mixture.

Like anything, the equipment taking the measurments to provide that data, is all based on the fact everything is properly setup and calibrated. Whether it be a fuel turbine, o2 sensor, etc. Timing has an effect on egt, as well as fuel mixture. You can have too little timing, with lots of fuel, and get xxx egt. then you can add timing, pull fuel, and get xxx egt again, except probably making a good amount more power. Most of the time, playing with that stuff, the power readouts from the changes, will tell you what the engine likes.

bck

Well all the above mentioned items were checked several times throughout the runs, remember these engines spent 2 days each on the dyno. Just found it a little different so much weight was placed on bsfc over O2. Where do people tend to like the O2 readings to be?