Don Terrill’s Speed-Talk

1320 Feet MPH Comparisons between V8, V6, S6, 4 Cylinders

( not a Forum Question, instead 1320 Feet MPH Comparisons info )

ProStock V8 500cid -vs- ProStock MotorCycle 2 and 4 Cylinders

even though the CDA of the ProBike is less than that of a ProStocker
the ProBike's 1320 Ft MPH is often 3 to as much as 7 MPH slower )

even though the incrementals at 330, 660 , 1000 are very close in most cases
and even the 660 FT MPH are still very close...but by the time you get to 1320 FT
the more Cylinders + larger CID have more MPH

basically the same thing can be seen even if the CDA's are closer
like in the Automatic/Converter Cars with V8's -vs- 4 or 6 Cylinders
they likewise have lower 1320 Ft MPH than V8 Engines

CDA = the Drag Coefficient x times the Frontal Area in Sq.Feet
CDA = the Drag Area

Maybe you will find out that an eff. engine regardless of cylinder count for the same cubic inches if tired and geared right, will produce about the same et and power.

And figure all at the same vehicle weight and drag numbers and such so the test will be an apples to apples test..

pdq67

pdq67 wrote: ↑Mon Mar 12, 2018 12:43 am Maybe you will find out that an eff. engine regardless of cylinder count for the same cubic inches if tired and geared right,
will produce about the same et and power.

And figure all at the same vehicle weight and drag numbers and such so the test will be an apples to apples test..

pdq67

i realize your "Point of View", however, in reality, it will never workout like you Posted
especially if it were in an "Apples -to- Apples" test .

this becomes very clear when you run the Simulation past 1320 Ft , like just even to 1400 FT is so much more drastic effect
and 1400 + Ft so on, is a tremendous change or difference as Vehicle fights against Wind or Aerodynamic losses

SpeedTalk Forum member GreenLight 's NHRA F/D Dragster 4 Cyl Honda engine
set NHRA F/D Record 7.996 ET @ 161.190 MPH ( 1st 4 Cyl Dragster to run a 7-Second ET )
so this is good Data to compare :

7.996 ET at 161.190 MPH 4 Cylinders at 1320 Ft

a very good V8 Engine hi-Qualifing NHRA Car or Record holding Car , at 7.996 ET will run in this next Section : the slowest V8's MPH in that Group is = 169.34 MPH

169.34 MPH - 161.190 for 4Cyl = 8.150 MPH difference or Loss as the 4 Cyl's HP and TQ Curve ,
fights against increasing Aerodynamic Losses at 1320 Ft FinishLine
if it were a distance like 1400 FT , it would be even a greater MPH difference between 4Cyl -vs- V8

http://www.maxracesoftware.com/bulletin ... ?f=58&t=95

if I may, as I have not posted here often.... does this trend have something to do with - and I may be paraphrasing source as well as content in correctly - Warren Johnson stating that 'the amount of power pulses goes quickest and fastest' ?

Tq vs load/drag?

It is interesting to see, I would have thought the PS Bike would mph better due to size... Thats what I get for thinking.

The aero drag on the bike is probably worse of all of the vehicles?

John Wallace wrote: ↑Fri Apr 13, 2018 8:06 pm The aero drag on the bike is probably worse of all of the vehicles?

Performance Trends has one ProStock Bike listed as :
5.00 = Frontal Area Sq.Ft
0.450 = Drag Coefficient
so 5.0 x 0.450 = 2.250 Drag Area or CDA

Motion Software Drag 2003 has ProStock Bike listed as :
6.00 = Frontal Area Sq.Ft
0.450 = Drag Coefficient
so 6.0 x 0.450 = 2.700 Drag Area or CDA

Pat Hale / SpeedTalk's Quarter Pro has a typical MotorCycle listed as :
6.80 = Frontal Area Sq.Ft
0.550 = Drag Coefficient
so 6.8 x 0.550 = 3.740 Drag Area or CDA

a typical Comp Eliminator Race Car with a V8 usually is :
20.0 = Frontal Area Sq.Ft
0.38 = Drag Coefficient
so 20.0 x 0.380 = 7.600 Drag Area or CDA

so that if i would make a ProStock Bike have a CDA like a V8 Race Car
example = change ProBike from 2.250 CDA or 2.700 CDA .... to = 7.600 CDA like a Car
.... the ProBike 's 1320 Feet MPH would be a lot worse in an Apples-to-Apples Dragstrip test

that's why i stated = if it were a true Apples-to-Apples test between Inline 2 or 4 cyl -VS- V8 engines
the 1320 Ft MPH would be a lot worse or an even greater difference if it were "Apples-to-Apples"

i first noticed the 1320 Feet MPH differences back in late 1980's while writing and simulating
Dragstrip Runs in my ETA software program in DOS QuickBasic 4.50 .. then later 1992 in VBDOS 1.0 and VB1.0 Windows version

below is a Screenshot of 1992 version ETA_Calc ,
which is a little ET/MPH Calculator that will generate ET/MPH/GForce Data every 1 Feet of Distance
it does a pretty good job even on a very fast MPH Super Comp 8.90 ET/MPH with a Throttle Stop

Notice that for a 4 Cylinder F/Dragster with a lower CDA value
the 1320 FT MPH = 161.190 ... is much slower than the various V8 RaceCars,
and that you would probably need to go as slow as 8.30's or so to get to a V8 Race Car going 161.190 MPH

even a C/SM running 8.145 166.42 ...is 5.23 MPH faster than a 4 Cyl running 8.120 ET at 161.190 F/D Record Run

NHRA National Record in F/D Class
F/Dragster 4 Cylinder Honda S2000 Engine
8.120 ET at 161.190 MPH
established April 23 , 2005 No Problem Raceway
Certified by : Danny Garcia , National Technical Director

Would you have a comparison of the ratio of CDA to HP of each vehicle?
(or maybe HP/CDA)

Interesting thread.

John Wallace wrote: ↑Sat Apr 14, 2018 8:21 am Would you have a comparison of the ratio of CDA to HP of each vehicle?
(or maybe HP/CDA)

Interesting thread.

John ... thanks for the interest in this Thread !

For anyone reading this Thread in future...
in the Picture above :
those various C/SM, B/SM, D/A , ET/MPH incrementals
are real Dragstrip Run Data ... just a Log of good NHRA Event Qualifying Run Data
and the "ET and MPH Calculator" is just simulated Run data of the real incrementals
to see if there are any acceleration problems,
or to see how good the correlation is ,
or to even use the "ET and MPH Calculator" as a sort of "Lie Detector"
to catch anyone Posting "Bogus Dragstrip Run Data"

i don't have actual Engine Dyno TQ and HP Data
for those various Class Cars above ,
to make a comparison of the ratio of CDA to HP of each vehicle or HP/CDA

the simple "ET and MPH Calculator" can calculate the exact HP at the Tire Contact Patch
each Foot of Distance , but to reverse engineer ET Slip back into an Engine Dyno TQ and HP Data/Curve ,
would need a bunch more inputs like this "minimum inputs" in this next Pic below :

Wow! I learn something from every post you make, Larry. Thank you for contributing.

Olds455 wrote: ↑Sat Apr 14, 2018 8:55 pm Wow! I learn something from every post you make, Larry. Thank you for contributing.

thanks Olds455 !

If the issue is the number of power pulses per foot traveled, wouldn't a 4 cylinder at twice the rpm give the same result as an 8 cylinder at half the rpm? What rpm would a pro stock bike be turning, compared to the 4 cylinder dragster? No answers, just wondering how this fits into your data .

ijames wrote: ↑Sun Apr 15, 2018 1:04 am If the issue is the number of power pulses per foot traveled, wouldn't a 4 cylinder at twice the rpm give the same result as an 8 cylinder at half the rpm? What rpm would a pro stock bike be turning, compared to the 4 cylinder dragster? No answers, just wondering how this fits into your data .

the 4 Cylinder F / Dragster 5 Speed Trans 127.6 cid = was 9200 RPM= Clutch Lockup RPM ...... to approx 11500-11700 1320 Ft Finish Line
3.504 Bore x 3.307 Stroke 6.022 C-C Rods

from George Bryce 's ProStock Bike VROD 160cid = "We run it from 8,000 to 10,000 rpm." 9600 RPM point of Peak HP
http://www.yellowbullet.com/forum/showt ... ?t=1915994

ijames ,
Look at the bigger Picture :
notice the acceleration rate of the 4 Cyl Dragster thru the Feet Distance incrementals
now compare 4 Cyl's 60-330-660-1000 incrementals

F/D ( it only took me about 2 Hours to find the F/D's incrementals , just when i was about to give up, i found the ET Slip Data )
60 Ft= 1.078<<--- faster than the V8 Car Group
330 Ft= 3.184<<--- faster than the V8 Car Group
660 Ft= 5.004 - 135.14 <<--- even though the 4 Cyl has the fastest 660 FT ET compared to the V8 Car Group .. the 660 MPH is already being affected
1000 Ft= 6.603 <<---- Look at this 6.603 @ 1000 Ft ... it matches the 2nd fastest V8 Car out of the Group below
1320 Ft= 7.996 - 160.79<<--- now the 4 Cyl 's MPH is rapidly changing -VS- the V8 Car Group ... basically same effect a ProBike -vs- ProStock Car

136.18 MPH - 135.14 MPH = -1.04 MPH Loss @ 660 FT
169.34 MPH - 160.79 MPH = -8.55 MPH Loss @ 1320 FT
** If you create or make a ProBike have the same CDA as a ProStock Car ... the 1320 FT's MPH would be a greater difference than i've Posted !
or Vice/Versa --> give the ProStock Car the same low CDA of a ProBike ... again the 1320 Ft MPH would be a giant difference !

However ... 60ft, 330Ft,660FT , and sometimes 1000 FT .. not much differences ... its really starts showing up around 1100 ft to 1320 ft

if you look closely at my old 1992 ET/MPH Calculator ... thats the reason i had to split up the Number of Cylinders into those Catagories
same thing with Transmission Types / Combinations .... to account for or to predict the 1320 Ft MPH correctly !

Maybe find some 1/8th mile racers ET slips?
(who race only 1/8th mile)

Wonder if it might be because most 1/4 mile race vehicle are geared for 1/4 mile.
Maybe the engine is 'topping out' and not pulling as hard after a set point.
But I guess this still doesn't explain the 4/6/8 cylinders MPH difference probably.



Still would be interesting to see if geared for 1/8th if the incremental would still favor 8 cylinder engine.

John Wallace wrote: ↑Sat Apr 14, 2018 8:21 am Would you have a comparison of the ratio of CDA to HP of each vehicle?
(or maybe HP/CDA)

Interesting thread.

This! At the top end, the drag force per HP has a rapidly growing effect.

What would the numbers look like if you doubled the HP and the weight of a vehicle but left all other parameters unchanged? Could also look at predicted top speed over a many mile course for a more dramatic illustration of the effect.

PS: I don't know of anything in physics that supports the theory of impulse frequency affecting performance.(apart from the extremities of being shot from a cannon vs. a constant thrust rocket )