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. mark6052

    mark6052 Member

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    Brain, I understand you are new to this all. I have seen ALL the questions you post. may I suggest you go to casper and spend sometime with kevin. I met him this last jan. he is a class act, and seems to be a very nice guy. (plus he has an awesome shop) the best thing that has happened for me over the years is being around some of these guys that have been there and done that. I learned long ago that the BV is NOT an idle mixture screw. as you now see.
     
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  2. Scouder

    Scouder New Member

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    Thanks Kevin, I was hoping you might stumble on to this little ramble. I thought you might have some tricks for up here.

    I hadn't thought about advancing the cam to capture some cylinder pressure, but it's a great idea. My cam is 114, set straight up. When I get a chance I'll bump it up a little and see what it does.

    I'm still looking for a reason to make the trip over to your neck of the woods. When I get over there I'll look you up.

    Did you guys get some track time with the new ride? A little nicer than the old one? :rolleyes:

    -Brian
     
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  3. Mike Canter

    Mike Canter Top Dragster

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    To correct what was said early....adjusting the blade gap and the BV does in fact set the idle mixture. We set the blade gap to a known measurement that will give us the idle speed we want then we adjust the BV to give us the correct fuel and between the two of them we get the correct idle mixture. Like I said earlier you can pretty well tell when you are close because if you blip the throttle you should have a crisp off idle response. Backing up what Bruce said earlier it is MUCH MORE important to have the correct staging mixture that we can tell by having the EGTs around 625*. If you are too lean on staging you are going to have poor off the line response and start heating your motor/EGTs too fast. Too rich at staging and you will put the fire out in one or two cylinders and they will take their time to re-ignite and producing power. So if while staging you see one or two cylinders drop way down on EGT then you are going to have to lean it out just a small amount until they stay up there.

    AS far as what is happening with your EGTs on your back cylinders when you richen up the mixture is caused by pooling of the fuel in the intake manifold. When you get so much fuel from being too rich the fuel stops atomizing and drops and collects on the floor of the intake manifold so now the back cylinders see way less fuel than the front cylinders.
     
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  4. Les Mellows

    Les Mellows New Member

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    Flow

    If the Car has Aerated nozzles in the Ports and the system is run "hard" to the other end . You may Hear a Pop out there , and then be searching for the failure as it is not distinguishable at IDLE and depending on the port CK pressure this still may not become evident until 1000'. I have seen on a WAR motor after looking dilligently for 3 or 4 starts that it was not found and each time the car went further "testing", Until the panel made it very apparent the issue was still there . When the nozzles were relocated to the place they lived the year prior the car was again fine, after the idle was adjusted ( aerated mnozzles change the idle circuit and BV) reflowed everything back to normal , this is the time you begin replacing the disfiguered pistons as they appear . The damage is dependant on the Chamber and quench area and also your density altitude( it will run lean and draw/syphon air once the fuel is being forced through the ports ).
     
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  5. Mike Canter

    Mike Canter Top Dragster

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    Thanks Les. I knew somebody had to have done it.
     
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  6. Alkydrag

    Alkydrag Sr. Dragster

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    We run an RPM data logger in our Pro Street car. The thermocouples are the small 3/16 probes (I think they're 3/16). I've always used the 1/4" probes, and from what I understand, the smaller ones are a lot more sensitve then the 1/4" probes. I was like scouder. It was driving me nuts trying to figure out why my temps were sky high and we never burned it down from beaing lean. Everything indicated they weren't as high as they were telling me. Based on past experiences and the amount of fuel coming out the pipe at stage, they were reading about 300-400 degrees high. We would go through the traps at 1400-1500 degrees and the plugs and bearings looked great.
     
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  7. Alkydrag

    Alkydrag Sr. Dragster

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    That would be a bitch to find!!!
     
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  8. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    couple of things

    Couple of things I noticed wasn't mentioned. As a disclaimer I don't think these are necessarily things Scouder needs to do.

    Nobody mentioned adjusting the idle check to control head temp. The BV is the preferred method, but just stating there is another way if you like your stage flow but want more or less head temp.

    Also, I always recommend putting several air bleeds in the injector to go up or down with idle without having to adjust your idle adjustment screws. When you do that, you change the barrel valve. It's a lot easier to start with a standard opening then pull bleeds out or put them in to control idle rpm.
     
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  9. Chuck Maruniak

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    Barrel valve

    First of all, make sure the notch in the barrel valve shaft is between 12 and 1 o'clock. Then, check your idle relief valve and make sure it is around 2 1/2 to 3 pounds. It doesn't matter if your hat is hooked up or not because you are just checking the flow through the valve and with air, the nozzles don't create enough back pressure to matter. Check your port check valve and make sure it is between 8 and 12 pounds. You can adjust that to your liking later. Check your throttle plate and make sure they have around .010 clearance on them. Some times the reason you get what you are getting is because the plates don't have the correct setting before you adust the barrel valve linkage. If you have any questions feel free to call me at 330-352-8908. Chuck!
     
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  10. Scouder

    Scouder New Member

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    Chuck,

    Thank you for the suggestions. I never did get the EGTs down, but in spite of that, all seems to be well. When I got the barrel valve too rich it would start to separate the EGTs from front to back, so I leaned it back out until the the EGTs came back together and left it there. It turned out that 80% was where that happened. The blades ended up being .008 at 1800rpm. My biggest concern was that it would build head temp too quick, and I would be hot at stage. On my first outing, I went from start, through the burnout, and back to the stage beams in 1 minute, trying to make sure I stayed cool. As it turns out, the back of the head had only picked up 30 degrees from startup, so my fears were unfounded. Next time I'm going to try to take a little more heat from the warmup to the line, and take a little more time doing my backup and stuff. It'll just take a few times to find the right combination to get the right head temp at stage.

    If I had just done what I was advised to do in the first place, and not worried about the EGTs, everything would have worked fine.

    -Brian
     
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