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Can someone tell me what the temp reading that I should be tring to get to is?
Thanks

90ca18det wrote:Can someone tell me what the temp reading that I should be tring to get to is?
Thanks

Temp on idle mix?

It will take a long time for any change to show up in the steel of the exhaust header.

i don't think temp really matters much. what matters most is the air fuel mix being the same across all cylinders producing about the same mean temperatures.

match417 wrote:i don't think temp really matters much. what matters most is the air fuel mix being the same across all cylinders producing about the same mean temperatures.

I'm with you, 417.

I've tuned a lot of sled motors using my IR thermo as a tool. But I don't shoot for a specific temp..too many variables. From machine to machine and is use of the IR( how far from port the reading is taken, material/thickness of pipe etc.) And, once the pipe has heat it takes quite a bit to see any change(can't turn the air/fuel screws and watch the temp rise and fall). Hell you can bring the revs upby 1000 and it takes about 30 seconds for that to show up as external heat. I get a run condition that I like by traditional means and then use the IR to find out where (tempwise) that specific engine reads when running well. And then use it to ensure that nothing changes too much.

EGT gauges at least give you fairly quick acting reflection of current conditions (probes in head pipe using a standard like 100mm from piston edge/valve face)..but even those are being eclispsed by sniffers.

match417 wrote:what matters most is the air fuel mix being the same across all cylinders producing about the same mean temperatures.

That is correct; however, you can still try to work close to a certain idle temp, say at 1500 or so. Some people who have done it can share it with you. I think my header temps were around 580 at 2k RPM.

reelrazor wrote:It will take a long time for any change to show up in the steel of the exhaust header.

That may be true with Cast Iron, but with these thin wall steel headers, you can see changes fairly rapidly.

That may be true with Cast Iron, but with these thin wall steel headers, you can see changes fairly rapidly.

I use my IR on sled expansion chambers all the time (18 gauge). They are usually quite a bit thinner than 4s bike exhausts. You will see an increase in temp semi rapidly, but once it has heat, you aren't gonna see it cool unless you stop all heat input (shut it down) and then start from low again. My point is you are not gonna turn the screw a 1/4 turn and see the temp go up or (especially) down 50°. All I realy look for with my IR is equality from cylinder to cylinder

And running egt and seeing 1200° inside the pipe will show in the 500°s on the surface with IR.