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 Post subject: Re: BLP 5124 blocks
 Post Posted: Fri Sep 21, 2012 6:03 pm 
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Your Log looks like it was still in the 11.5 range? Guessing that was with the 92's? what was the weather like on that run? I would try 90's make a couple of passes then throw the 92's in and makes a couple more noting the mph. I am running 86/94's in my 1050. See how she runs this sunday in 50 degree's!

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 Post subject: Re: BLP 5124 blocks
 Post Posted: Fri Sep 21, 2012 6:46 pm 
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Yes, 92's were in it on the log. The air was good. I don't have measured weather numbers.

Shrinker, the timing is locked at 37. It idles in gear.

I made Mark's adjustments and I hope to get it back to the track next weekend.


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 Post subject: Re: BLP 5124 blocks
 Post Posted: Fri Sep 21, 2012 7:23 pm 
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Ron Gusack wrote:
Yes, 92's were in it on the log. The air was good. I don't have measured weather numbers.

Shrinker, the timing is locked at 37. It idles in gear.

I made Mark's adjustments and I hope to get it back to the track next weekend.



You can go here and select your track and it will give a fairly accurate DA for that day.
http://www.dragtimes.com/da-density-alt ... ulator.php

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 Post subject: Re: BLP 5124 blocks
 Post Posted: Fri Sep 21, 2012 8:55 pm 
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Using that site, I get 1131 DA


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 Post subject: Re: BLP 5124 blocks
 Post Posted: Fri Sep 21, 2012 10:55 pm 
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OK I thought it was a locked timing engine because when you lock the timing and then set the idle mixtures the idle mixtures have to be too lean. If you had an advance curve and ran less timing at idle you would give it more fuel at idle and it would be a better thing, it would have more power at idle and actually respond with more power at the top end because the cylinder temp and exhaust conditioning would be more consistent.


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 Post subject: Re: BLP 5124 blocks
 Post Posted: Sat Sep 22, 2012 9:55 am 
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shrinker wrote:
OK I thought it was a locked timing engine because when you lock the timing and then set the idle mixtures the idle mixtures have to be too lean. If you had an advance curve and ran less timing at idle you would give it more fuel at idle and it would be a better thing, it would have more power at idle and actually respond with more power at the top end because the cylinder temp and exhaust conditioning would be more consistent.

Locking the timing made it idle much cleaner and pit driving was better, but I don't know for sure which carb I had on it back then.


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 Post subject: Re: BLP 5124 blocks
 Post Posted: Sat Sep 22, 2012 6:42 pm 
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I dont think you will bother but there is always an optimum timing and mixture for idle thats different to the rest of engine running. Just locking it only found one option. You dont have to run 20 degrees of centrifugal advance etc like a stocker it may only need 6 or 8. It depends on the chamber burn speed. It sounds to me like this is a slow burning engine at idle.


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 Post subject: Re: BLP 5124 blocks
 Post Posted: Sat Sep 22, 2012 6:46 pm 
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ET will vary from run to run with out locked timing...

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running E85
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 Post subject: Re: BLP 5124 blocks
 Post Posted: Sun Sep 23, 2012 1:51 pm 
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I've never understood the locked timing thing, as far as power is concerned. I hear guys claim that they make more power with the timing locked, but I don't get it. I always thought max cylinder pressure at X ATDC had the greatest force on the crank and as rpm increased, so did piston velocity. That fact made advancing the ignition timing critical to keeping max pressure at X crank degrees ATDC.

So I'm in the camp that claims locked timing just makes the engine happy at low rpm, but probably hurts overall power. I have no idea if stockers and super stockers run their timing locked or not. If Barry says locked is more consistent, I'll keep it locked. My main reason for putting a 2 circuit carb on is to try to make the car more consistent. I've got more power than I really need.


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 Post subject: Re: BLP 5124 blocks
 Post Posted: Sun Sep 23, 2012 6:06 pm 
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Locked timing is a bit like varying the AFR at max torque to max HP. Its wrong. But its done because the engines have other issues that are hard to sort out and the determination is not there go through the processes. An engine with correct combustion that produces the most cylinder pressure anywhere in the rev range or load range must have a consistent AFR and variable timing. Properly done scientific tests with perfectly vaporized fuel have proven time and time again that the AFR for maximum load at any point in the rev range is the same, it doesnt need to be richer at max torque and leaner at max HP. The reason why that is done by racers is because the engine cant vaporize the fuel at high RPM (max hp). The problem is in the design of the cam and heads but what people do is adjust the carby then call it quits.
The timing aspect of an engine is influenced by the burn speed. The max cylinder pressure has to occur at the optimum crank angle(just like you said). The stroke rod ratio and the burn speed determines the timing to do that. The burn speed is referred to as Mass Fraction Angle The actual point of crank angle has to match the amount of fuel mass burnt with the piston speed to get the most crank effort. This is where people adjust the carby, they lean it out at high revs so that the mass fraction stays correct, the timing should be altered but they dont do that. EFI people understand this part of combustion better than carby racers.


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 Post subject: Re: BLP 5124 blocks
 Post Posted: Sat Sep 29, 2012 8:22 am 
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This is the only data I have from last night. The green line is the afr with 90 jets and 2 flats up on the floats. The pink is 92 jets. The car was .2 and 7 mph slow in the 1/8 with better DA. It's a little leaner but doesn't appear to be any smoother with the floats up. It ran much better after lowering the floats. I never remembered to activate the logger on any other passes. I'll try 88's next time out unless the consensus says otherwise.
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 Post subject: Re: BLP 5124 blocks
 Post Posted: Mon Oct 08, 2012 1:46 pm 
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Location: Auburndale, Florida
Is that a small tire car you're running? Do us a favor. When you post these logs it would help to see the driveshaft RPMS also.


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 Post subject: Re: BLP 5124 blocks
 Post Posted: Wed Oct 10, 2012 5:54 pm 
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nomad wrote:
Is that a small tire car you're running? Do us a favor. When you post these logs it would help to see the driveshaft RPMS also.

Bruce, Drive shaft RPM isn't hooked up. The tire is 30x9. Are the AFR spikes from the little wheel stand the car does? It seems to calm down in high.
The run below is with 88 jets and 1493DA
Image

This run is with 90 MJ's and 700DA. The AFR is a little leaner.
Image


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 Post subject: Re: BLP 5124 blocks
 Post Posted: Sun Oct 14, 2012 8:12 pm 
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I sent the graph above to Racepak tech support to see what they thought about the spikes in 1st and 2nd. They told me the graph looked normal, which seems wrong to me based on some of the logger posts I've seen.

I'm not sure where to begin to try to smooth out the spikes, but if i get it smooth, but rich, will jet changes move the whole line toward lean?

I remember reading that increasing MAB will make it taper toward lean at the top of high, but what will it do to the spikes?


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 Post subject: Re: BLP 5124 blocks
 Post Posted: Sun Oct 14, 2012 9:08 pm 
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Ron Take a look at my graph in my AFR thread, its doing the same thing going towards lean before each shift. Curious to see what u do to fix it also.

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