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Discussion Starter · #1 ·
I'm thinking about using a high speed retard. I've been told that it will give a bigger top end charge. I'm running 40 degrees in 14:1 555 BBC. Thinking of taking out 4 - 6 degrees. What do you think ? Thanks - Steve
 

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pig hunter
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btw 1-2* not 4-6 and it makes a differance in a few cars not all...may i ask what head your useing to have 40* as your total timing??
 

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I pull 3 degrees out of mine using the N2O window switch in my ignition box...............It is worth it.........with my stuff at least.
 

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from what ive seen the higher the rpm of the engine the more it has made a difference. if you only crossing at 7000-7200 your not gonna see much. maybe .3-.4 in mph. if your spinning it to 9000 you might see 1-1.5 mph. just what ive seen from my limited dealings with it
 

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Discussion Starter · #8 ·
Thanks guys. It sounds like it doesn't have as much effect as I was told. But that's ok.
 

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Why would you want to retard timing when you have less time to light the fuel at high rpm? I would try to pull 1 or 2 degrees out right after peak torque and roll it back in by peak hp.
 

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Most have this deal all wrong,Study your dyno air fuel or your car AF readings,engines VE best at peak torque, and as they approach peak HP and after peak HP the fuel curve starts to richen up,just before this point start to slope in more timing to burn the fuel about 2-3 degrees ,most engines we have done this with on dyno have made 5-15 HP,some of the highly developed stuff shows little or no gain,while the sportsman stuff usually gains.Most drag race engines want more timing on the launch,timing retarded at peak torque and timing added after peak torque as engine starts to go rich.Bill C.
 

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High gear is when the motor is grunting the most. Typically in the lower gears the motor is not as loaded due to gear multiplication.

In general, the motor will like a little bit more timing in the lower gears and a little less in high. Most dyno's do not have gears. in my experience a motor coming off the dyno and on to a track will want more fuel and less timing in general.

The fuel tuning is just the opposite, a little less in lower gears and a little more in high.

This is of course assuming you have a good tune up in the car before you start.

This is one of the reasons that a projected nose spark plug works well in a modest race engine. The projected plug acts hotter at lower rpm's and colder at higher rpm's. Of course at a certain point of cylinder pressure/heat you can't use them.

Blessings...........Ron

Blessings...........Ron
 

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If you look at a typical spark curve for a any specific speed load point, you will see that if you have a high enough octane fuel you will get to a certain point which is called "MBT" (minimum spark for best torque). Advancing spark beyond this results in the torque starting to drop off. People that are retarding spark on the big end and making gains most likely are over advanced in the first place and that is why the car picks up. If the spark curve is optimized you shouldn't have to retard. Just my opinion
 

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Given the varying acceleration rates, I would imagine the engine would like a totally different timing map in each gear?

Each combination is going to react different to the varying loads and rpm's/rates based on comp ratio/fuel used, spark plug/location, chamber/piston design/quench area, rpm range, water/intake tract temp ect.... But if you know the acceleration rate of each gear, you could map each rate on the dyno, then just adjust the whole curve according to vp/grains at the track.

I can see some combinations picking up with just a high gear retard, but imagine it would be better putting some back in at some point/rpm in the run if your system is capable.
 

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Given the varying acceleration rates, I would imagine the engine would like a totally different timing map in each gear?

Each combination is going to react different to the varying loads and rpm's/rates based on comp ratio/fuel used, spark plug/location, chamber/piston design/quench area, rpm range, water/intake tract temp ect.... But if you know the acceleration rate of each gear, you could map each rate on the dyno, then just adjust the whole curve according to vp/grains at the track.

I can see some combinations picking up with just a high gear retard, but imagine it would be better putting some back in at some point/rpm in the run if your system is capable.

I'm pretty sure you know this, but this is were the Inertia Dynamometer comes into play to duplicate going through the gears on a race track.

You'd have a pretty difficult time duplicating what an engine see's on the race track in first or sec gear with a water brake.........in my opinion:p

Blessings.........Ron
 

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pig hunter
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i agree with everyone above lol.. all have great points
 

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Since we're talking drag racing...some guys unknowingly limit their engine's combination because they see damage either on the dyno or the track and back off " things"* to keep it safe. 99% of the time the damage initiates right around peak cylinder pressure, (peak torque) so paying close attention to the timing during that period can let you put more power back in the engine that you may have pulled back on.

*things = compression and cam timing.
 

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what box do you have jake?

Cody
Mallory Digital 6.......sorry bout the delay. My engine is a little different animal.........lack of compression and a heavy car. But I spin it to 8500.............so I leave with a bunch of timing, and yank it back out at the top of all 3 gears............it is worth a repeatable 1-1.5mph.
 
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