fuel/boost ratio

Anyone know what would be a good fuel/boost ratio for a c rotor screw motor before it is to lean were about 0.335-0.345 plugs are still good?thanks

 

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Plugs look pretty much the same as when they went in. Thats why I ask the question I thought we were getting close on the fuel/boost ratio but plugs look great but egt's are around 1180-1200 degrees I know egts are just a number and high egts could be a number of things was just looking to see if I'm way out on my fuel/boost ratio. Thanks

 

ratio

I have .3 ratio for the first second of the run and then substantially richer the rest of the way down the 1/8th. 1080 max egt. My plugs show some heat. The cad is completely gone from the face.
I think the car will go quicker if I lean it more downtrack. The bearings are perfect and other guys are 1-1.5 gpm leaner than me.

I've had the plugs look like new before but it was always soft tuneups with lower boost.
I'm at 60 psi now with a BAE5 at 2510lbs. Went 382@195 mph in 1700ft air. Is it going to take hot plugs to make it go faster?

BTW I mostly run the R5671a plug. I mixed in a set of 6061's and they read about the same. Not scary, but showing some heat.

 

EGT should be for reference and not the number that you go by. Plugs and bearings dont lie. Trust them over a sensor.

I always just pull up all 8 EGT's and make sure they all follow the same path. Thats all they are used for to me. You can see if one is slow to light or if a hole goes out altogether.

And like Will said, we indeed have a cylinder that shows its consistently 80-100* warmer than the rest and in reality its one of the coolest.
Ive seen guys chase EGT's around and "balance" the motor at idle in the pits and be pumped about how great they are then go out and smoke 3 pistons out of it by 800ft with an EGT reading of "only" 1000*.
Ours goes through the finishline with temps around 1190-1220* and haven't hurt a slug, ever. Fuel Volume, to a point, is your friend. Don't forget that. Fuel=HP as long as you can burn it.

Compression, mag(lead), cam timing, etc... These are things that some often leave out. Cant run a C-rotor deal with 10.00:1 the same as one that is 12.25:1.

 

Had this on the dyno, I asked, is there anyway the egt is in the wrong pipe?

Is anyone using fuel flowmeters and air flow meters on the dyno to get air to fuel ratios?

Or using O2 sensors in each pipe?

 

Keep in mind "I'm just a welder"..........but how many times have we seen 1200 on thermocouples, but plugs look brand new, but a guy is afraid to mention he's "running it safe" by retarding it 6-10* (or his marks are off), which simply means the fire is now in the pipes right on the sensor !
Add timing and the temp drops 200* at stripe and picks up 3 tenths !
IT HAPPENS !



Bob Meyer
Meyer Race Cars / San Diego
2014 Our 49th Anniversary

 

How many teams pull timing out at top end? Does it add mph?? Also Mike where do we find your plug reading article?

 

I have to ask -- how can you guys compare EGT temps --unless your EGTs are located in the same place on the header, and at the same depth into the pipe ?

Are we assuming just a bit ?

Love these types of posts , just wish the OP's were sharing more of their particulars , otherwise the smart ass in me wants to say -- just put the car up to the phone ------------

 

Egt

EGT (thermocouples) serve really very little purpose in drag racing. Because everything happens so quickly in drag racing that the thermocouples used can't start to keep up. Try this, take a TC and heat it with a hot fire like a butane torch, it will take 8-10 seconds to reach around 1000 degrees. There is technology that will measure this in nearly real time but is serious $. TCs do provide some comparative data, if a number is different run to run then something has probably changed.