Reply With QuoteDon't know diddley, but I think you should be around 1,400'.
There's probably some people who know a lot more than me on this subject so how hot is to hot?
With my turbo motor the EGT at a cruising speed is around 1350 but if I run at WOT 20 lbs boost / 6800 rpm for a few seconds the temp goes up to 1800 + eek!
So then I'm inclined to richen up the max rpm point on the fuel maps and the EGT's go down as well as the HP.
At the 1800+ EGT the motor pulls incredibly strong.
I never ran a EGT gauge before now and don't really know what is the norm. I've asked around and no one seems to be able to give me a good answer on the EGT's
Most say reading the plugs is the best and the EGT gauge is not the best way to tune, only a reference.
I think there is more power to be had here but I am cautious about the temps I have seen.
Maybe a turbo motor reads a lot higher EGT because of the exhaust backpressure?
Running 20 lbs boost relates to 20 lbs backpressure also.
I have the thermocouple mounted in the head about 1" from the exhaust flange.
Any input?
Don't know diddley, but I think you should be around 1,400'.
Don't know what to tell you about EGT's in a blown application...
I ran EGT regularly when I raced normally aspirated motors. I relied on it extensively during testing...so much, in fact, that if my EGT wasn't working (thermocouple failed, etc.), I wouldn't even bother going out to test.
Used in conjuction with other readings, such as plugs, stopwatch, baro, even a dyno, etc., you can get a relatively accurate idea as to how to set up your motor for particular applications, races etc.
In my experience, for example, the use of a stopwatch, jetting and plug readings would set me up for a particular road course. All this time, I would watch my EGT and note the temp based on my fastest lap times. Then, as the day went on and the atmosphere changed, I could watch the EGT change and adjust jetting accordingly and stay on top of my game. Further, when I went to various other tracks away from home, jetting for max power became a snap because it was based on my knowm EGT temp at peak engine performance.
Different experienced people will give you wide temp variations as far as what is acceptable/maximum EGT. Personally, I'm known for being frugal and lean toward engine reliability. For this reason, I would usually run 1250-1300 farenheit but be perfectly willing to run as high as 1500 farenheit if the competition required me to do so. I never had a major failure even at 1500 degrees nor did I ever run into anyone else that did (of those others that read EGT).
Please remember that I have no idea how this experience with normally aspirated motors should reflect/compare to your blown motor. I would think, however, that if you are producing greater power with your engine at 1800 degrees, then you should probably be referencing all the other components that indicate just how your engine is taking it...such as plugs, oil temp, etc.
I would strongly recommend that you speak with some long-time professional turbo motor builders that have more experience at this and can help you determine what is right for your application. Ray Hall, Paul Pfaff, etc.
Good luck,
LO
[ September 07, 2003, 06:34 PM: Message edited by: LakesOnly ]
I think you will find that 1600 F is the TOP of a motor that will LIVE. I've built a ton of turbos (ski race) and blowers (drag and ski race) and the 1800 F number sounds (like rolling a floor jack over you dick) bad. Once you realize what happened, it's too late to care. Play/ enduro motors will live at 1450/1550 F, and drag race only, who cares? Just load in another bullet, after this one melts. Have you tested you EGTs for accuracy? 1800 F sounds like a down payment on a new motor. (or at least the valves and seats)
I am currently dealing with same exact thing, I just installed egts today, I installed them in manifold before turbo. I can tell you i Have been flying and building turbocharged airplane engines for years . peak lean is about 1700 degress any thing over that and things start to melt. I know if they are installed after the turbo the temp is around 150-300 cooler due to pressure. the gauges will vary in temps. I doubt your is reaching 1800 but it does definitly sound like its lean, lenghts and connections change every thing even soldering the thermal couple after bolting togther changes the temp a little. but as long as they read consistant thats what is important. I am going to test my boat monday night or weds morning and I will let you know the results. I am only running 10 psi of boost. But I am having some lean issues at cruise at 0 psi boost. I will let you know what mine read. I am sure if you do a plug reading you will find that it is lean on top end. Thats my two cents best of luck ,cause running a turbo motor lean only takes 3 or 4 seconds to melt. I have already melted a few sets of JE pistons Ken
bigkatboat:
...the 1800 F number sounds (like rolling a floor jack over you dick) bad...
LO
When we dynoed twin turbo gas motors, we would not let the turbine inlet temp get above 1600F. Something to keep in mind: for a turbine inlet temp of 1600F, the EGT's at the ports would be around 1350F-1400F. The EGT was higher at the turbine inlet than at the exhaust port. Your EGT at the exhaust port is 1800F, but your EGT is hotter at the turbine inlet.
Why do you say 20psi boost relates to 20psi back pressure?Did you measure it?
Nubbs:
Why do you say 20psi boost relates to 20psi back pressure? :confused Did you measure it? [/QB]No, I didn't measure it but I was told that by the turbo guru that I bought some of the components from.
From some more asking around I've done evidently there is a problem that you can get with too rich a mixture called " stack firing " where lots of fuel is still burning going out the pipe. I'm thinking this is the problem I'm experiencing that is causing the high temps because if I richen it up slightly even just 7% the engine won't peak out. Then it seems the EGT went down not because the mixture was better but because the engine wasn't burning all the fuel and the top RPM was way down.
Even with the temps I've read I haven't noticed the headers or the turbine housings glowing red yet.
Of course I only held it at WOT for 4 or 5 seconds.
I've seen blower motors on a dyno pull and the headers were glowing red after 5 or 6 seconds.
Thanks for the input and opinions,
Keep it coming
Unchained, Your are rite on track!
evidently there is a problem that you can get with too rich a mixture called " stack firing " where lots of fuel is still burning going out the pipe. Is your thermocouple at the header flange?
[QUOTE]Originally posted by FastTimmy:
Is your thermocouple at the header flange? [QUOTE]
Yes,
[img]http://www.***boat.com/image_center/data/500/220thermocouple-med.jpg[/img]
If it's still burning on the way out it would defininely read the hottest at the point where my thermocouple is installed.
I've been running it this way for a while now and it hasn't caused any problems but I want to figure out a solution. I always feel like I'm right on the edge of too rich to clean out.
If I hadn't bought the EGT meter I wouldn't have noticed the high EGT and just tuned it until it pulled the hardest and got the highest RPM to the jet pump(same thing). In a way I feel the EGT meter is messing me up.
It makes sense that less fuel would make less heat.
One thing I notice with this Haltech system is the range of adjustability you have.
With Carbs, changing jets makes very small incremental changes in the mixture.
With the EFI you can change the mixture by large volumes.
You can make monumental errors if you don't watch out.
At WOT / 20 lbs. boost the injectors are open 7.5 milliseconds per revolution and that's too rich.
There is probably the equivalent of less than one drop coming out of each injector per revolution.
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