Max EGT
 

i have read some past threads on this but I didn't find a real solid answer. I have a Whippled 496 with a forged bottom end, Raylar cam, ported stock heads and Lightning headers. It has an EGT gauge off of the #2 cyl tapped into the exhaust port on the head. Just cruising it runs around 1350 but when I push it it starts to climb above 1400 and I back out of it. Can someone tell me if above 1400 is safe. I have bumped up the fuel press a bit but it didn't seem to made a difference. The plugs look good.

What is the best way to reduce EGT's? Does high octane fuel (race gas) help?

Aluminum can melt @ 1220*. I would say 1350 is high.

and you would be correct ... especially in this case if it happens very quickly as implied.

This is why I am confused. I've read other post with motors have no problems at 1500*.

Even though the EGT reads a certain temp, only a percentage of that transfers to the piston/heads etc. There are far more qualified people than me that could give you specifics on what is safe.

During running, the combustion chamber (ie: head comb chamber, piston top + rings/ cylinder wall) will have a boundary of air/fuel that protects the metal surfaces. This is caused by proper a/f ratio and the metal surfaces being cooler. Therefore, combustion temp can, and is, be much higher than the melting point of the surface metals.

When you run too lean, all of/or part of the boundary layer can disappear and that's when parts melt.

Kind of fascinating stuff huh. Always amazes me too. :ernaehrung004:

Does anyone know if race gas or 100ll would lower the egt's. Also, how big of an affect does water temp(motor) have on it?

yes and no on the fuel. in a lab setting, a 100 octane low lead like avgas will burn more slowly and give you a small incremantal reduction in egt. but that isn't a solution in general and certainly NOT a solution in your case.

the observation is made above about egt vs what is actually happening inside a combustion chamber. with out getting into the nitty grity of it, that observation is essentially correct. but having said that, there is a lifetime of empirical data that says that when you are seeing 1400 f, 2" out of the port early on in the load profile then you are serious asking for trouble almost immediatly... and thats on a normally aspirated motor. while my experience with superchargers is limited my experience with turbos is pretty extensive and i can tell you that if i was seeing data from the car that suggested 1400 before the extreme end of the longest straight then i would be putting a LOT more fuel in it pretty quick because that motor would not survive for the length of the race.

as for fuel... your selection of fuel type is very specific relative to the configuration of the piston tops and combustion chambers and comp ratio . those define the burn rate and that is a function of the fuel chemestry. the upshot being that you select the fuel first to suit the motor THEN you adjust the fuel curve to suit the load profile and gives you good af ratios at your desired revs.

now im sure there will be 86 posts now that describe how people run over 1400 ALL the time for hours on end with no ill effect. fine. be my guest

all im saying that it would not ever occur to me to do that on a forced induction motor.

Thank you for your input!

I have just been running hard for short burst due to the high temp. But I would like to get it addressed so I can see how fast she will go. I'll try adding some more fuel and see how it responds.

you said 1400 was on port 2, it might be a little higher or lower on a different cylinder. maybe add a intercooler would be best option if you dont have one

Running lean and in the 1400s at WOT will make the most power and if built for it wont hurt anything.We like to see around 1450 at full boost.One of the big problems we face is keeping the rear holes as cool as the front of our engines even with 3 stage pumps etc.
Most of the time while running in our boat we can have a 75 to 100 degree difference between our front hole and rear temps at WOT . So if our front holes are 1400 our rear is probably to hot.So if you are monitoring your temps with just one probe be sure to hit your hottest hole first.
For a bought the same price as a tank of race fuel you can add a methanol injection set up run 93 and with proper sized nozzles for front and rear and you will be with in 25 degrees front and rear .You will also pull 200 degrees or more out of your combustion chamber temps even with added boost..
If methanol injection isn't in the cards at this point. If it were me with your set up I would try and keep your hottest hole no hotter than 1400 by adding more fuel and play it safe.
www.iceinjectionsystems.com
Good Luck!
Good luck!

It does have an intercooler. I run about 8psi of boost. Temp sensor is in the forward most cyl on the starboard side.
Attachment 358574

I run 1575 at full throttle. 20+ lbs of boost but intake temp is only 120 degrees. Have never melted anything.

Call Dustin at Whipple and ask him. He will tell you exactly what it should be.

559-442-1261

I am not sure of your description of where you have the EGT probe mounted, but it reads that you have the probe in the port of the head itself. The proper location for the probe is about 1/2" out from the header flange on a right angle to the tube it self and preferably on the bottom of a marine header, which I know can be difficult to place because of the water feed tubes sometimes. If you have the probe in the port of the head or on a bad angle you can get some strange inaccurate readings. With a supercharger on a 496 with lets say 5-7lbs of boost its not unusual to see 1350 temps under boost and load, any higher than that (accurate reading) is pushing the envelope and the fuel curve and possibly timing advance should be reset to lower the EGT's a bit. Remember with supercharging you need 93 octane fuel minimum and under boost of this level your effective compression ratio is about the equivalent of 15-17 to 1., combustion temperatures here get hot and the pressures are the reason supercharged engines wear out rings quicker than normally aspirated engines. Be careful, check with Whipple on the program and EGT's and protect your investment!

Best Regards,
Ray @ Raylar

water/alcohol injection would help on this...

egt's
 

Hi guy's. Just signed up today and was curios as to what others were running for temps.
I have a genV 454 stroked to 490 w/a holley 420 (no chiller yet) and a pair of holley 800's, Clay Smith 306 cam. I also ran 1425 at wot and idle at 800+/- a few. My probe is installed 1" from the manifold flange in #2 (Stainlees Marine Chambered Manifolds) with custom made full length dual walled pipes. The boat is an 89' Arriva 24 @ 38-3900lbs. I ran 70 mph with a Mirage 25P 3blade. Unfortunately, after the 7th time out this spring I melted #8. I don't believ it was from the high egt's but rather detonation. Btw, I'm looking for a 502 bare block genV. Anyone know of one for reasonable price in the Phx area. I've got it in my blood and there's no cure found yet. Happy new year to all. :ernaehrung004: