Don Terrill’s Speed-Talk

Have you seen power gains by not using to high exhaust lift?

Erland

Not the complete answer by any measure, but when I tested rocker ratios in a near-stock TPI 305" Chev, 1.6 rockers picked up 10-12 HP over the 1.5s on the intake side but +/- 1 HP on the exhaust.

I'm not sure there is a complete answer Bill.

On the engines I've played with in the software, which is way less than a lot of you guys and mostly limited to 70a/80s Ferraris seems to say what I'd expect

Exhaust needs less lift than intake...that makes sense since the valves are smaller so the same % flow happens at lower lift.

But, if the exhaust flow is low, then getting the valve open faster can be more helpful than adding duration and adding lift does just that. I have a buddy that does Harley pretty well who's given me a ton of pointers of porting and he pretty much always the same or very similar lobes intake and exhaust and was horrified to see I had longer duration in my exhaust cam in the FrankenFerrari......but it's lower lift too and the flow is a touch lower than I wanted and quite a bit lower than he uses %wise. My intake cam has steeper ramps but the software says it's just too much for the exhaust side to use and a bit more duration is better than faster ramps/more lift. When I say more duration its 5 deg@.050", but 12 seat more, but only .420 vs .450 lift.

Another thing is see it doing, much again makes sense, is it loves the last set to basically remove the accel/deccel portion of the cam. I played around with the last one day and got it perfect but thought it odd it liked more on intake, then I pulled up the cam profile data the lash exactly matched a big turn in the ramp slope.....and I've seen specs from mechanical ohc cam factory stuff like this, I remember a maserati wanting .011-.013" On the intake, tbat s not expansion, that's removing the ramps the cam designer worked so hard to add.

ive always wondered if you have a given "lobe area" how a longer duration & lower lift vs shorter duration & higher lift would compare for area under the curve and what characteristics would specifically dictate one or the other. e.g. for a 4V would there be a trend and a different trend for 2V due to the relative efficiency difference during blow down

If you increase lift. Lets say by increasing rocker arm ratio that you increase area in all the different zones.

If you increase duration you need to decide how to adjust that area.

For these 3 examples there was no change made to the exhaust.

_______I__N__T__A__K__E
Rocker_Arm_Ratio_=_1.650_________Valve_Lash_=_0.0210

Intake_BTDC_(IVO_to_TDC)_=_4.559
Intake_Pumping_(TDC_to_BDC)_=_106.103
Intake_Ramming_(BDC_to_IVC)_=_15.992
Intake_Overlap_(IVO_to_EVC)_=_25.558

VALVE_____Lift______Opens___Closes__Duration
_________________Deg_BTDC__Deg_ABDC_____________Area
_________0.00000____47.69_|__84.37_|_312.05_|__61.01
_________0.00600____44.55_|__80.80_|_305.35_|__60.99
_________0.01000____42.73_|__78.67_|_301.39_|__60.98
_________0.02000____38.71_|__73.99_|_292.70_|__60.91
_________0.04000____32.32_|__66.84_|_279.16_|__60.69
_________0.05000____29.68_|__63.94_|_273.61_|__60.56
_________0.10000____18.96_|__52.59_|_251.56_|__59.70
_________0.15000____10.52_|__43.84_|_234.35_|__58.68
_________0.20000_____3.06_|__36.19_|_219.26_|__57.27
_________0.25000____-3.97_|__29.07_|_205.10_|__55.41
_________0.30000___-10.85_|__22.20_|_191.36_|__53.71
_________0.35000___-17.79_|__15.20_|_177.41_|__51.04
_________0.40000___-24.96_|___7.98_|_163.03_|__48.74
_________0.45000___-32.52_|___0.38_|_147.86_|__45.30
_________0.50000___-40.80_|__-7.88_|_131.31_|__41.46
_________0.55000___-50.19_|_-17.26_|_112.55_|__36.16
_________0.60000___-61.45_|_-28.50_|__90.05_|__29.76
_________0.65000___-76.72_|_-43.55_|__59.73_|__20.32
CAM
_________0.00600____56.01_|__92.95_|_328.96_|__39.04
_________0.01000____50.50_|__87.43_|_317.93_|__39.00
_________0.02000____41.86_|__77.65_|_299.51_|__38.83
_________0.04000____30.98_|__65.35_|_276.33_|__38.48
_________0.05000____26.89_|__60.95_|_267.84_|__38.29
_________0.10000____11.47_|__44.82_|_236.29_|__37.07
_________0.15000____-0.70_|__32.36_|_211.67_|__35.53
_________0.20000___-12.08_|__20.95_|_188.87_|__33.37
_________0.25000___-23.72_|___9.23_|_165.51_|__30.83
_________0.30000___-36.39_|__-3.48_|_140.13_|__27.21
_________0.35000___-51.53_|_-18.59_|_109.88_|__22.27
_________0.40000___-72.76_|_-39.65_|__67.59_|__14.31


_______I__N__T__A__K__E

Rocker_Arm_Ratio_=_1.814_________Valve_Lash_=_0.0229
Intake_BTDC_(IVO_to_TDC)_=_5.022
Intake_Pumping_(TDC_to_BDC)_=_116.685
Intake_Ramming_(BDC_to_IVC)_=_17.598
Intake_Overlap_(IVO_to_EVC)_=_28.118

VALVE_____Lift______Opens___Closes__Duration
_________________Deg_BTDC__Deg_ABDC_____________Area
_________0.00000____47.78_|__84.48_|_312.26_|__67.10
_________0.00600____44.91_|__81.19_|_306.10_|__67.09
_________0.01000____43.21_|__79.22_|_302.42_|__67.06
_________0.02000____39.46_|__74.86_|_294.32_|__66.99
_________0.04000____33.42_|__68.02_|_281.44_|__66.80
_________0.05000____30.89_|__65.26_|_276.16_|__66.65
_________0.10000____20.70_|__54.41_|_255.11_|__65.88
_________0.15000____12.71_|__46.10_|_238.80_|__64.86
_________0.20000_____5.72_|__38.91_|_224.63_|__63.41
_________0.25000____-0.80_|__32.26_|_211.46_|__62.02
_________0.30000____-7.10_|__25.95_|_198.85_|__60.34
_________0.35000___-13.35_|__19.68_|_186.32_|__58.00
_________0.40000___-19.73_|__13.25_|_173.53_|__55.71
_________0.45000___-26.30_|___6.63_|_160.33_|__52.70
_________0.50000___-33.25_|__-0.35_|_146.40_|__49.30
_________0.55000___-40.82_|__-7.90_|_131.28_|__45.59
_________0.60000___-49.30_|_-16.37_|_114.33_|__40.36
_________0.65000___-59.26_|_-26.29_|__94.45_|__34.04
_________0.70000___-71.93_|_-38.84_|__69.23_|__25.19
_________0.75000___-93.96_|_-60.37_|__25.68_|___9.07


_______I__N__T__A__K__E
Rocker_Arm_Ratio_=_1.650_________Valve_Lash_=_0.0210
Intake_BTDC_(IVO_to_TDC)_=_3.590
Intake_Pumping_(TDC_to_BDC)_=_105.139
Intake_Ramming_(BDC_to_IVC)_=_30.389
Intake_Overlap_(IVO_to_EVC)_=_44.825

VALVE_____Lift______Opens___Closes__Duration
_________________Deg_BTDC__Deg_ABDC_____________Area
_________0.00000____47.73_|_115.53_|_343.26_|__67.11
_________0.00600____44.28_|_111.60_|_335.88_|__67.09
_________0.01000____42.27_|_109.26_|_331.53_|__67.07
_________0.02000____37.86_|_104.11_|_321.97_|__67.00
_________0.04000____30.83_|__96.25_|_307.08_|__66.76
_________0.05000____27.92_|__93.05_|_300.98_|__66.61
_________0.10000____16.13_|__80.58_|_276.71_|__65.67
_________0.15000_____6.84_|__70.95_|_257.79_|__64.55
_________0.20000____-1.36_|__62.54_|_241.18_|__62.99
_________0.25000____-9.09_|__54.71_|_225.61_|__60.95
_________0.30000___-16.66_|__47.15_|_210.49_|__59.08
_________0.35000___-24.29_|__39.44_|_195.15_|__56.14
_________0.40000___-32.18_|__31.51_|_179.33_|__53.62
_________0.45000___-40.49_|__23.14_|_162.65_|__49.83
_________0.50000___-49.61_|__14.05_|_144.44_|__45.61
_________0.55000___-59.94_|___3.74_|_123.80_|__39.77
_________0.60000___-72.32_|__-8.62_|__99.05_|__32.73
_________0.65000___-89.11_|_-25.18_|__65.71_|__22.35

Stan

In Dynomation 6 output does it provide any values for lobe /valve area or overlap areas?
Thanks

pastry_chef wrote: ↑Fri Oct 13, 2017 10:49 pm In Dynomation 6 output does it provide any values for lobe /valve area or overlap areas?
Thanks

No, not that I see not in -5 or -6. There is a graph where you can look at lift vs angle, but only 1 design at a time.

....I'm not convinced the area was any real meaning though. This kind of sort of came up on a thread about port choke point and the valve curtain is the choke most of the time, but Im not sure choke point is right...in that if the cam is designed correctly the valve will be open enough for the flow you have and opening it more won't help (over cammed) so the valve isn't choking anything and adding more area under the curve will not add flow and may very well hurt flow.

Thats what a program like dynomation or engmod4t do for you, they help you figure out when and where more cam helps without you having to guess based on something like area curves. I think I read CamKing has some formulas he follows and Burn Stainless told me their soft spits out the "optimal design" based on bore, stroke, head flow, cam timing....in both cases I THINK there has to be an assumption that other stuff is already optimal....so that is add a cam or headers that "make the best of the other parts I have" vs "what are the best parts" which is what you get when you try changing everything, but it takes a lot of time....I've probably spent a few hundred hours playing with stuff for my project car and bought the -6 upgrade to play "what if" some more

Changing the rocker ratio changes the lift, but it also changes the duration so you do get a somewhat different answer when you add lift at the cam lobe or by changing the rockers.

No news on the corrections for the bugs I found, Larry must be struggling a bit.....I can't even imagine how complex the code is for a program like that. I know on -5 and update would come out that said it fixed or correct whatever small thing I'd them I'd see a 10% hp change on a setup that didn't even use the feature the notes said changed and need to shoot out a bug report....everything matter to everything else.

Sorry in my last post this was incorrect for increased intake duration exhaust duration unchanged.

Intake Overlap (IVO to EVC) = 23.196

My software had a bug where it used an increased exhaust duration to calculate EVC point.

Stan

mk e wrote: ↑Sat Oct 14, 2017 7:12 am

pastry_chef wrote: ↑Fri Oct 13, 2017 10:49 pm In Dynomation 6 output does it provide any values for lobe /valve area or overlap areas?
Thanks

No, not that I see not in -5 or -6. There is a graph where you can look at lift vs angle, but only 1 design at a time.

....I'm not convinced the area was any real meaning though. This kind of sort of came up on a thread about port choke point and the valve curtain is the choke most of the time, but Im not sure choke point is right...in that if the cam is designed correctly the valve will be open enough for the flow you have and opening it more won't help (over cammed) so the valve isn't choking anything and adding more area under the curve will not add flow and may very well hurt flow.

Thats what a program like dynomation or engmod4t do for you, they help you figure out when and where more cam helps without you having to guess based on something like area curves. I think I read CamKing has some formulas he follows and Burn Stainless told me their soft spits out the "optimal design" based on bore, stroke, head flow, cam timing....in both cases I THINK there has to be an assumption that other stuff is already optimal....so that is add a cam or headers that "make the best of the other parts I have" vs "what are the best parts" which is what you get when you try changing everything, but it takes a lot of time....I've probably spent a few hundred hours playing with stuff for my project car and bought the -6 upgrade to play "what if" some more

Changing the rocker ratio changes the lift, but it also changes the duration so you do get a somewhat different answer when you add lift at the cam lobe or by changing the rockers.

No news on the corrections for the bugs I found, Larry must be struggling a bit.....I can't even imagine how complex the code is for a program like that. I know on -5 and update would come out that said it fixed or correct whatever small thing I'd them I'd see a 10% hp change on a setup that didn't even use the feature the notes said changed and need to shoot out a bug report....everything matter to everything else.

pipemax uses the term "time area" or something similar

digger wrote: ↑Sat Oct 14, 2017 6:57 pm
pipemax uses the term "time area" or something similar

I have to re-register my copy, I changed PCs and now it says its unregistered so I can't look quick.

I think though that pulses/waves in the pipes are about when valves open and close and tuning is about the time the pulses take to reflect/bounce and figuring out where the crank and valves are at that time. This comes back to what I was saying that a formula can help you optimize say the exhaust to match the heads and cam but can't tell you if the setup is optimal.

Way way back in school I remember optimizing a spring and there were 9(?) equations and no way to solve it...so we ran an "exhaustive search" which means write a program to try every combination and save the best one. That is what the iterator in DM does...or tries to because it doesn't change head flow or intake/exhaust tuning which would make it take days to run on a normal PC, so the answer it spits out for the cam is still just guidance.

.....this stuff is hard.

-6 Rev 13 is out and seems to correct the issue was having...I'll need to play with it some more but in the 30 minutes or so I plated with it now looks right.

The tri-y head thing appears to work the way I'd expect and standards header tuning seems to be about the same as -5....the waves show as stringer in -6 though.

The intake runner length result is quite different from -5 and I'm not 100% sure I believe it....I'll need to play with it some more and wish I had good data to check the output against. -5 wanted me to have a pretty long runner tuned to the 2nd pulse and this made sense to me since the engine has enough flow to rev well past redline, so in my mind it made sense a long runner with strong wave that would restrict flow above my redline came out best...like tuning for mid range. -6 says NO! to that. It wants a short runner ...6" on the 5th pulse is best at 945hp, 7.5 on the 4 is 932, 9.5 on the 3rd is 919 and 13" is 913hp on the 2nd. -5 told me 17-18" was the 2nd and 940hp and 12-13 was the 3rd and cost 20+hp, but gave about the same number for that stack as -6 does. I'm confused. I think 13" will fit under the stock hood so I like that answer but I find it hard to believe a 6" runner with pretty low pulse energy left is best, and its too short to build so I'll never know for sure.....I might be able to do a 9.5, I guess it that is better than 13ish I'll know

Anyway, -6 is different and I don't have data to know which is right(er).

Here's a graph that show what I was talking about with intake tuning. It's a 6" runner vs a 16",both tuned to about the same hp peak rpm, a 9.5 or 13 are also tu bed and fall in between in a shorter is better order. The shames look right, the tuned length seems right but I struggle to believe the shorter is better answer....i would expect the 13 or 16" to be best and at least cross over /under the short runner as tbey move in/out of time. This seems wrong to me......