egt's

roofer · 19-09-2005, 07:45 PM

Anybody use egt's on there engines ? are they reliable ? ive been out on my boat today dialling my mad efi in and everytime i went over 6k my egt warning lights come on as the temp goes over 1250, but when i back the throttle off the temp drops instantly, now i dont want to toast my new block but tomorrow im going to go over 6k and see if temp drops below 1250, how long do you reckon ive got before i melt the pistons ?

JamesM · 19-09-2005, 08:54 PM

I would have thought the temp would drop straight away when you back off as the amount of fuel and air your burning drops to negligable levels so the exhaust gas would be alot cooler.

I think 1250 is near the line so I wouldnt risk seeing if it comes back down after 6k. The pistons will melt in the blink of an eye long before you've had the opertunity to decide wether or not its getting any lower.

I think you would be better off richening the whole curve so the temps are low and safe then monitor where it gets hot and cold and try to tune it so its fairly constant Tune it in bands like 500 to 2000 rpm then once the egt temps are constant for this band move on to 2000 to 4000rpm etc. Once your happy with the curve lean the whole curve back off to get a good hotter but not over hot egt temp.

Also wouldn't hurt to ask on S and F as they no alot more about this stuff than me!!!

JamesM · 19-09-2005, 08:56 PM

Also take a look at the tuning instructions for the Brucato PCU as you may want to follow a similar procedure to tune your set up.

Here's the link:

http://www.brucatosvs.com/pcu_instructions.html

JamesM · 19-09-2005, 08:59 PM

The steam wheel refured to in the brucato instructions moves the whole fuel curve up and down!!!

Hope this helps!!!

JamesM · 19-09-2005, 09:08 PM

Quote:

Originally posted by Johnny Boat Dude
I think 1250 is near the line so I wouldnt risk seeing if it comes back down after 6k. The pistons will melt in the blink of an eye long before you've had the opertunity to decide wether or not its getting any lower.

When I said near the line I didnt mean the 'spot on good temp line' I meant the 'oops I've melted my pistons line'

I think good temps are around the 1100 mark.

michaelcaine · 19-09-2005, 09:29 PM

thank god ive got carbs!!!

JamesM · 19-09-2005, 09:42 PM

You reckon!!! Is your jetting absolutley spot on then? You've got main jets, idle jets and vent jets and changing one affects the others. Plus 2 and 5 run hotter than the rest so have to be jetted richer!!!

michaelcaine · 19-09-2005, 09:44 PM

i dont run with main jets,i leave the fuel pump from the garage in the tank!!!!

scottyboy · 19-09-2005, 10:05 PM

Can you tune your mad efi For the fuelling on overrun? If you can you could program it to put abit to much fuel in when you come off the throttle to cool the piston crown? Thats wot we do with big power 4 stroke engines dont know if it will work on a two stroke though?

JamesM · 19-09-2005, 10:08 PM

They do that on car engines because they're on and off the throttle alot where as with a boat engine it may be held flat out for extended periods so it wouldn't help much!!!

scottyboy · 19-09-2005, 10:11 PM

Yeah spose ya right JBD prob cause alot of over fuelling and "flat spots" on a two stroke to thinking about it!

roofer · 19-09-2005, 11:08 PM

The handbook i got with mad efi had some diagrams and instructions missing,they are also missing on the website.
Luckily ive found them on www.sdsefi.com so should be able to sort it tomorrow.

JamesM · 19-09-2005, 11:13 PM

start rich dude!!!

roofer · 19-09-2005, 11:17 PM

Ive got a dial on the dash which can lean or richen the fuel by + or - 50% so should be ok.

JamesM · 19-09-2005, 11:19 PM

Cool!!!

I think 1100 to 1150 is about on the money for exhaust temp but it may be worth doing a search or asking on Scream and Fly to confirm that.

roofer · 19-09-2005, 11:25 PM

Already checked on s&f, most people on there dont rate egt's.
Guy i race with runs his at 1200 and his engines lasted all season.

BluFin · 20-09-2005, 08:09 AM

Most of the over the counter EGT's are fairly crude, From a gas turbine point of view which is where I know them from. They are far more adaptable being able to tune the thermocouple, alternately have slow or fast respose depending on the application. they never rely on one sensor but average the temp from around numerious pickups in the same area damping out errors & flutuations.

roofer · 20-09-2005, 09:38 AM

I got mine from www.digatronusa.com its got a probe for each bank of cylinders,tach, lap times, cylinder head temp. Seems well made and was easy to fit.