Boost and Timing Questions

[Mystery Fan]

Is there a rule of thumb for horsepower gains for boost and timing, for instance.

1 lb. of more boost equals "X" horsepower, from 10 lbs to 11 lbs.

1 degree of more timing equals "X" horsepower, let's say 17 to 18 degrees.

This assumes no issues with A/F or Knock.

Just curious to see thoughts on more boost less timing vs. less boost more timing.

Thanks

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[jrsimon27]

1 pound of boost at least 10whp
1 degree of timing more at least 10whp

 

[MyLilPony]

Is there a rule of thumb for horsepower gains for boost and timing, for instance.

1 lb. of more boost equals "X" horsepower, from 10 lbs to 11 lbs.

1 degree of more timing equals "X" horsepower, let's say 17 to 18 degrees.

This assumes no issues with A/F or Knock.

Just curious to see thoughts on more boost less timing vs. less boost more timing.

Thanks

depends on the dyno but I have seen 1psi =10-30whp depends on the type of boost as well (Turbo>Supercharger) kind of thing ... timing 5 to 10

 

[ProChargerTECH]

1 pound of boost at least 10whp
1 degree of timing more at least 10whp

That is about right...

If you see sell then 10 hp gain per degree, STOP.
If you see less then 10hp gain per PSI added, STOP.

Thats my easy "rule of thumb" to keep motors together.

 

[Phoenix]

That is about right...

If you see sell then 10 hp gain per degree, STOP.
If you see less then 10hp gain per PSI added, STOP.

Thats my easy "rule of thumb" to keep motors together.

nah man, keep going. all motors love 45psi and 20 degrees.

once.

 

[MyLilPony]

nah man, keep going. all motors love 45psi and 20 degrees.

once.

"I live my life a 1/4...BOOM...Fawk..."

 

[Phoenix]

"I live my life a 1/4...BOOM...Fawk..."

:lol:

my 2nd timed pass at ennis i ran a GTO. i was a moron and ran on 1/8 tank so the car starved for fuel and went into limp home mode. i stayed in it, beat the goat and prayed i didnt fuxxor the motor on the return road. drove it home that night.

you can win a race even with the check engine light on. you run over a second slower than normal though :frusty:

vendors, contact me for destructive testing of parts at my email.

 

[dubster99]

Generally see 10-15 wheel per degree of timing.

 

[Cory S]

My setup picked up 28whp going from 20-21.5°

From 17 to 20°, 44whp gain.

 

[engineermike]

Interesting topic!

The basic rule of thumb is each psi of boost is worth 6% (of NA power) more. So at 410 rwhp, 1 psi is worth about 25 hp assuming spark stays the same. Turbos get more. Another way to think about it if the SC is positive displacement is that flow is proportional to blower speed. So, if going from a 3.875 to a 3.75 pulley, air flow will increase by 3.875/3.75 = 1.033 = 3.33% increase. So at 700 rwhp, one pulley increment is roughly 1 psi, and .033 x 700 = 23 hp.

I believe Dustin Whipple once posted that 1 deg spark is worth about 20 hp at this power level and spark timing. He's also made reference to it depending on how far below Maximum Brake Torque (MBT) you are and he is correct. The further off from MBT you are, the more it affects power. 1 deg at 12 deg total timing is worth a lot more than 1 deg at 23 deg total.

Looking a little more scientifically, on the Predator:

After doing some math based on the cal, 1 psi makes a difference of about 26 ftlb at the crank, or about 33 rwhp. However, the borderline knock timing would retard 1.4 deg to avoid knock. Conversely, MBT also reduces by about .25 deg, which offsets the loss somewhat. What this means is that you might have started 8 deg below MBT but increasing boost 1 psi meant you were now going to be 8+1.4-.25= 9.15 deg below MTB, netting a loss of 1.15 deg spark as compared to MBT. Clear as mud?

The Torque Ratio indicates it loses 0.7% torque for 2 deg reduction, 1.7% for 5 deg reduction, and 5.2% for 10 deg reduction. (Note: spark delta TR is only defined up to 0.9 load.) You can see that the more you retard, the worse it gets per degree. At 700 rwhp, that would mean only 2-3 hp for the first deg of timing lost. However, in the 10 deg reduction region, you're losing 7 hp for every degree of timing. Keep in mind that this is a 9.5/1 motor. The same table for the gen3 coyote shows more loss with timing reduction.

To make matters worse, cam timing and A/F ratio both can be adjusted to allow more spark, but as with boost, it's a give and take relationship with an optimum somewhere in the middle. Cam timing can move borderline knock 5 deg and MBT can move it as much the other way. You might sacrifice some pumping losses by running non-optimal cam timing, but if you can run within 7 deg of MBT vs 16 deg, then the net might be a gain. Same with A/F ratio. Optimum power might be at .85 lambda, but if you can run .80, lose 5 hp from lambda but gain .5 deg and 10 hp from spark then you net an increase in crank hp.

 

[Midwestracer]

Interesting topic!

The basic rule of thumb is each psi of boost is worth 6% (of NA power) more. So at 410 rwhp, 1 psi is worth about 25 hp assuming spark stays the same. Turbos get more. Another way to think about it if the SC is positive displacement is that flow is proportional to blower speed. So, if going from a 3.875 to a 3.75 pulley, air flow will increase by 3.875/3.75 = 1.033 = 3.33% increase. So at 700 rwhp, one pulley increment is roughly 1 psi, and .033 x 700 = 23 hp.

I believe Dustin Whipple once posted that 1 deg spark is worth about 20 hp at this power level and spark timing. He's also made reference to it depending on how far below Maximum Brake Torque (MBT) you are and he is correct. The further off from MBT you are, the more it affects power. 1 deg at 12 deg total timing is worth a lot more than 1 deg at 23 deg total.

Looking a little more scientifically, on the Predator:

After doing some math based on the cal, 1 psi makes a difference of about 26 ftlb at the crank, or about 33 rwhp. However, the borderline knock timing would retard 1.4 deg to avoid knock. Conversely, MBT also reduces by about .25 deg, which offsets the loss somewhat. What this means is that you might have started 8 deg below MBT but increasing boost 1 psi meant you were now going to be 8+1.4-.25= 9.15 deg below MTB, netting a loss of 1.15 deg spark as compared to MBT. Clear as mud?

The Torque Ratio indicates it loses 0.7% torque for 2 deg reduction, 1.7% for 5 deg reduction, and 5.2% for 10 deg reduction. (Note: spark delta TR is only defined up to 0.9 load.) You can see that the more you retard, the worse it gets per degree. At 700 rwhp, that would mean only 2-3 hp for the first deg of timing lost. However, in the 10 deg reduction region, you're losing 7 hp for every degree of timing. Keep in mind that this is a 9.5/1 motor. The same table for the gen3 coyote shows more loss with timing reduction.

To make matters worse, cam timing and A/F ratio both can be adjusted to allow more spark, but as with boost, it's a give and take relationship with an optimum somewhere in the middle. Cam timing can move borderline knock 5 deg and MBT can move it as much the other way. You might sacrifice some pumping losses by running non-optimal cam timing, but if you can run within 7 deg of MBT vs 16 deg, then the net might be a gain. Same with A/F ratio. Optimum power might be at .85 lambda, but if you can run .80, lose 5 hp from lambda but gain .5 deg and 10 hp from spark then you net an increase in crank hp.

always the best reply's

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