Help with idle EGTs. Can't get 'em down...

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by Scouder, May 9, 2010.

  1. Mike Canter

    Mike Canter Top Dragster

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    I would drop the leakdown back from 93% to 88% and try it first and record EGTs then let it cool down and try it at 85% and compare.
     
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  2. jim phillips

    jim phillips ta/fc

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    i run the brad fuel heads and run pretty good im pretty close to bruces my blades are set @12* 44amp msd 30*timing good air waterman fuel pump idle 2400rpms bv 80% i do have k- barrel valve done by jimmy rector there is a difference in mine and the nitro bv in how the spool is done

    my port nozzle opens @12lb

    whats the nozzle size in the hat and the intake and what do you have in the main

    how many gal a min

    after setting the bv mark the flat with something each flat either way will be 2% more are less per flat either way you you can always come back to your mark
     
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    Last edited: May 10, 2010
  3. bruce mullins

    bruce mullins Top Dragster

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    sounds to me that you have a poppet stuck open. (if it's that rich and still lean, it's got to be returning fuel) did you check the idle return poppet for the right direction and check to see if it is stuck open. also take your main line off the front of the barrel valve, shine a flashlight in and slowly open the throttle. you should be looking into and at the spool. is the "V" notch at the top and as you open the throttle does the notch roll towards the back? are there jets in all the places requiring jets ( main and high speed). I would not run it at all until you find out how and where the fuel is returning.
     
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  4. jim phillips

    jim phillips ta/fc

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    after you check every thing and its still to lean put a 100 in the main that will fatten it up for sure then lean it back 10 at a time i would rather be to fat that to lean
     
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  5. Scouder

    Scouder New Member

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    Bruce, I did look at the poppets, but did not open any to look for stuck. I'm gonna turn the high speed poppet around, and take that out of the equation. I'll check the pump saver and the idle check and see if they are holding. BV is setup right. V is at the top on the outlet side, and opens down and toward the inlet. I'll also check the pills.

    When I ran the bv up it was spitting ALOT of fuel out of number one, and I backed it off just enough to get it to quit spitting when warm. With that being the case I just can't get my mind around how it can still be lean. You can see from the numbers I posted above that some of the front cylinders were losing temperature the longer it ran, others gained.

    Where I come from, if you add fuel, and the temps don't drop, then timing is retarded and burning in the pipe. In this case I have run the timing forward far enough to kick against the starter, which helped, but didn't solve it. Sooo, 11.5 compression, 33% overdrive, 8100' density, even with advance timing, cant generate enough cylinder pressure vaporize/burn the fuel fast enough to keep it from burning in the pipe. Sooo, that would mean the extra fuel I'm giving it to cool it is making it worse by putting that much more in the pipe. If that is the case, pulling fuel OUT may lower
    EGTs. Next test (tomorrow after work) will be at 70% leak and advanced timing. It's the only combo I haven't tried yet.

    If that doesn't fix it, and the poppets aren't leaking, then I'm gonna put her at 33 degrees, 80%, 1800 rpm, and run it.
     
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  6. jim phillips

    jim phillips ta/fc

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    70% is way to low i have never seen one that low on a blower motor when the bv is to low the motor stumble when you go to crack the throttle and thats to low
     
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  7. Fuel Cars

    Fuel Cars AA/AM

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    I have a question about the port nozzles being on the same line as the hat nozzles, wouldn't the port nozzles be constantly spraying fuel, even at idle?

    I always thought that the port lines were to be fed from the port outlet in the bv.
     
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  8. REEHL EQUIPMENT

    REEHL EQUIPMENT Active Member

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    Are we checking the EGT's with a Racepak?

    Are the thermocouples sticking out too far?
     
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  9. Scouder

    Scouder New Member

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    Paul,

    The port outlet and the hat outlet on a K valve feed from the same chamber, so they are the same thing, it's just a convenient place to mount a hose. In my case, since I am measuring fuel flow, all the flow comes off the hat port on the valve, through the flow meter, then splits to the ports and hats. What keeps the ports from flowing during idle is a poppet with a higher crack pressure that the hats. Some call it a port check.

    So yes, if it weren't for the port check, it would flow both.

    -Brian
     
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  10. Scouder

    Scouder New Member

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    Robert,

    RPM logger. Thermocouples came from them as well. Dont know if the probes are sticking out too far. I have to make assumptions. I assume the bungs are factory from Dan Olsen, and I assume the probes are non-adjustable. :confused:

    -Brian
     
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  11. Flyboy68

    Flyboy68 Member

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    Brian, are all your egts reading the same before you fire the motor up? Randy @ RPM told me that if one is way out of wack, it will cause that whole side to be off. Also make sure they are all are the same distance in the pipe.

    Josh
     
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  12. Nitro Madness

    Nitro Madness Super Comp

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    I am new this data logger stuff....so far I love the RPM Data Logger....we went testing last weekend and got some run data....seems like our idle temps were in the 650-700 range....and the hot part of the run - 300 or 400 feet out they were 900-1200 degrees (20% nitro)...so we swapped a few nozzles and got them all in the 1050-1150 range by run #4.....they were all 1/8 mile runs....chutes out early due to short shut down area....I have talked with several other Data Logger owners this week as I was concerned about getting over 1100....Jim Stanke said they ran their alcohol car as high as 1300 but that was the absolute hottest they were comfortable with....then Larry Reep said his EGT's were 900 max and over that he would burn a hole....so there must be some differences in systems....maybe too many other variables...our probes are extend 3/8" into the header tube per Randy's instructions at RPM....our plugs looked great but we did not run the car far enough to color them much....not sure if this helps ya much but I'm looking for some comparisons also....
     
    #32
  13. bruce mullins

    bruce mullins Top Dragster

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    to be honest, I have NEVER tuned a motor or even been to concerned with idle temps. I will fire the motor up, set check and set the timing, then let it idle while going through the gears, maybe bringing the rpms up to 2500 when shifting and letting it run in high gear for a minute. then check reverse, back in forward, and let idle just a little longer before shutting it off. after this procedure which takes about 3 or 4 minutes, the head temp (i take it off the back of one of the heads) should be around 165 degrees. now something to remember is it will heat up faster if using a FRESH roots blower because the air coming out a fresh blower will be hotter than a weak blower. if the motor heats up to the temp in the warm up time, it's fine. ( just my procedure and opinion) too many people believe that great myth that if it runs on alcohol, the motor should run cold or cool . . . .wives tale!. . . . .
     
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  14. Scouder

    Scouder New Member

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    Bruce, you may have hit on one thing that could bear on this. My head temp sensor is a 3/8 threaded stud type, mounted in the deep recess under the header flange, between cyls 3 & 5, per BAEs instructions. You are taking head temp off the back of the cylinder. I'll bet there is a shitload of difference between the two. The reason I'm concerned with the EGTs is that I'm seeing rapid rises in the head temp. As I posted above, I went from 160 to 182 at an unloaded idle in 30 seconds. If part of that is just the mounting position then I might be less concerned.

    -Brian
     
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  15. Nitro Madness

    Nitro Madness Super Comp

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    Just for comparison I pulled up our run #3 last weekend - (4th run EGT numbers after a few nozzle changes were all closer to 1100, but I do not have that one on my computer at work)

    Pre-stage Idle temps = 528-669-389-504-724-755-777-800
    EGT's at 3.5 seconds into the run = 1069-1233-1160-1117-1109-1206-1139-1147

    This was at 1144 C/A - 526 KB with 175 cc heads - 14-71 Superman @ 18% over = 33 lbs. boost - 20% nitro - 125" car. Static timing was 25 degrees - with 6 degrees out for 1 second

    The run was a 1.00/2.72/4.20 @ 154 MPH early shut off
     
    #35
  16. jim phillips

    jim phillips ta/fc

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    egts 1300 seems high to me when i ran ihra a/fc and had the race pack pro one if i remember right egts were 1050 but that was a venny head motor and back in 2001 and i could tune from there by watching my plugs and bearings


    you cant compare apples to oranges
     
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    Last edited: May 11, 2010
  17. Scouder

    Scouder New Member

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    Good info.

    I just talked to Don at BAE and asked if they had any data on what a max head temp would be on a fuel head with the probe mounted where they suggested. I specifically asked if the had a "holy crap, that's gonna warp a head!" number. They didn't. The only data he could give me was that on their alcohol heads with the probe mounted closer to the deck than mine, but still between 3&5, they stage at 125 degrees. Sounds cold for an engine that has been warmed up and burned out.

    On a fuel head the probe is higher up between the exhaust ports. In fact, it is exactly centered on the port and between 3 & 5. It makes me wonder If I'm picking up some exhaust port heat. I'm gonna borrow a temp gun and shoot the back of the head and do a comparison.

    -Brian
     
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  18. AnimalCrew

    AnimalCrew New Member

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    idle EGT's

    Have just been through similar things with a fresh blower and a new fuel pump. What I found was I don't worry a whole lot about idle temps. I pay more attention to what the temps do at launch. I use a dual port nozzle system with 2 different poppet pressures to adjust temps to where I want them. Thanks to help from Mike Canter and some others, I got this figured out.

    There's a lot more to it than that simple explanation but my point is, as long as your head temp is OK, pay attention to launch RPM temps. For us with Big Chiefs, head temps are normally around 180 at launch.

    Our idle temps are generally spread around like yours are. Leak-down at ~82%

    Troy.
     
    #38
  19. bruce mullins

    bruce mullins Top Dragster

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    running the motor with "lower" timing instead of "max" timing will show a higher exhaust temp. I learned years ago to use a computer as a quick reference check, but trust the plugs and bearings over and above everything.
     
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  20. Jason Bunker

    Jason Bunker Member

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    I agree here with Bruce. Look at plugs and bearings to see how close you are on the tune-up. The Racepak stuff is just a guideline for the motor as far as tune up is concerned. Its not the deciding factor. I use the Racepak to see if the motor dropped a cylinder and when or why. Thats about it. Lots of stuff can effect cylinder temp on an EGT probe. That apparent by all the previous post's(Length down in header, age of the probe, ignition timing, angle of the probe in relation to the port, ETC...)

    I have seen cars that have max EGT's of 1300+, with room in the tune up.
    Also seen cars that have max EGT's of 1050 and they are thrashing in between rounds to fix it.

    Its sad to say, but you need to find that fine line in your combo where your "safe" and where your praying to the gods of Alcoa. Then you can be certain of what you need to pay attention to.

    Just my 2 cents...
     
    #40

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