is it posible to have "correct wave" tunning with shorty headers?
and would a cam with a tight lobe seperation have bad affects with shorty headers if you had minimal back pressure. the reason i ask is i have a 400 small block with pocket ported/bowl blended SR torquer 2.02/1.6 heads and a Comp cam 270H ground on a 106* lobe seperation. the specs for the cam go like this:
@ .050 int 6* BTDC 38* ABDC
@.050 exh 38* BBDC 6* ATDC
the cam is installed at 102*. the compression is around 9.5. and I'm using an RPM intake.
I chose the cam to use with long tube headers but since then i have removed it from the vehicle that had them. now i'm running into clearance issues with the car (88TA) and clearance issues with header to sparkplug interference(even with the shorty plugs). so far the only long tube headers that seem to fit are the Super Comp headers, and i do have the straight plug heads but they "relocated" the plugs for us, how nice of them!
any insight would be aprreciated. thanks.

 

is it posible to have "correct wave" tunning with shorty headers?
-----------------------------------------------

yes , with the collector length or the entire exhaust system length

the "wave" tunes in at "double lengths"

example=> best negative wave tunes in at 20 inches

then it will again tune in at 40,80,160 inches
same with primaries

but each "length segment" increase gives you lesser gains

the 20 inch would be best or most Torque

likewise
worst positive wave tunes in at 60,120 ..those points hurt torque

 

Max Race,

RE: Negative Wave/Pulse

In addition to those lengths, will harmonic tuning occur at 60", 100", 120" ,etc. (1/4, 1/2) wavelengths as well?

Or...

Is the positive wave a result of the 'reflected' pulse which occurs
at 60", 100", 120"?

 

good negative wave at overlap period=>
ex. 20,40,80,160,320

bad positive wave at overlap

example=> 30,60,120,240

dyno test correlate upper 90.0 percent to the above examples

----------------------------------------------------

you might think that you could again halve those numbers,
and it would still work , but it doesn't

it seems good negative wave definetly follows in "double multiples" of the original best collector length that makes the best peak torque

you can use the collector length to fool the engine if primaries might be too short
--------------------------------------------------------

Is the positive wave a result of the 'reflected' pulse which occurs
at 60", 100", 120"?

the 60 and 120 , but not the 100 in that example


also with SuperFlow Air Turbine ontop of carb, you can easily measure effects of positive / negative waves
they show up in Ve readings ....as wave either helps Ve or hurts Ve ...especially noticeable below 5000 rpms

 

Interesting stuff Larry,


It's late so the brain might not be working but with the 20" length would work well with a large overlap area where a 30" length (which is the common length on most street headers) would work better with a smaller overlap area camshaft.

I would think it has a lot to do with RPM level also.

How about the placement of the overlap peak in relation to the header lenght?

Bret

 

all the lengths 20,40,etc

i posted were just examples of effects

they are not the actual lengths that would work

all you do is find the best 1st Collector length
that makes the best possible peak torque or average torque
and then it will be "double multiples" of that length for best negative wave peaks centered on the overlap period

the total Collector length would be measured "internally"

from where Primary pipes end "inside" Collector -to- exact point where "internal length" dumps into atmosphere .

this works almost 100.0 % percent of time , so far

my Shop / Dyno is out in country, 3 miles away from City

so "all" my dyno test with exhaust headers are "OPEN" header tests ..i always try to use customer's headers , and total exhaust system if they want to try

that way , engine is always "tuned" with their headers they actually will use in their Race Car

 

Alright...I'm a little further into the book. The last clarification helped (Thanks OldSS).

It seems the further I read, the more this gets over my head and it's only the 2nd chapter!

For those that have read the book, he often inserts roman numerals
mid scentence in parenthesis, but I can't seem to figure out what
it means?

IE: Further experiments (XVI) show the effect of...

Is this pointing to a footnote, or is it some sort of engineering script, etc.?

He also mentions the term, "touring engine". Is that just a label
for a non-performance grocery-getter?

Lastly, page 34 shows graphs of exhaust pressure vs. piston position.

Looking at any single graph:

Are those graphs snap shots of the exhaust pressure during an
acceleration period between 1000-3000 RPM

or

Is it a snap shot of ONE cycle of combustion at a steady RPM?

The reason I question this is because it's an average pressure
representation.

All else is going well. I'm learning why V-type motors and coupling
certain exhaust ports are beneficial for torque production. Gotta
love new information.

Thanks in advance for answering the question!!

 

well, i don't think i got my answer that i was looking for. probably because i didn't say it rite. the cam i have is relatively mild on a 106* lobe seperation. but i need to know if using shorty headers is going to adversely (negative) affect my 400 over long tube headers.
heres my other question. so basically from what i understand from what maxsoftware said, you really cant "sonic wave tune" a street engine with an entire exhaust system, because it would in a sense have one LONG collector. so the only thing you can do is work on "ZERO" back pressure.
i can afford to lose some torque down low but would like to keep the mid range very healthy.
and now im just grabbing at thin air but, does anybody know which headers will "properly' fit the SR torquer heads with out plug clearance issues?
THANKS, Tom.

 

you really cant "sonic wave tune" a street engine with an entire exhaust system, because it would in a sense have one LONG collector.
=======================================

exactly opposite => you "CAN" tune your exhaust system length
with wave tuning

what i meant was the Collector internal length "includes"
the entire pathway till exhaust wave dumps into atmosphere

from where Primaries end "inside" Collector ...thru the internal lengths of mufflers/tailpipes/etc till dumping into atmosphere

if you have open header race car with just header collector you would tune for that wave

if you have same race car , but decide to install complete exhaust system including mufflers/tailpipes, then you would use one of the "NEXT double-multiples" of length ....which ever next length would be closest to what total length was under race car

 

and for more "wave tuning" insight ;

ever notice the intake manifold runner lengths are very much shorter than exhaust header lengths

yet both can be "tuned" to coincide or phase-in at overlap period

Intake= lower air temperature, slower wave speed fps...so shorter intake runner length

Exhaust= higher air temperature , faster wave speed, so you have to give wave further to go to phase negative wave reflection to peak centered on the overlap period.

=> longer exhaust pipes -vs- intake runner lengths

 

the cam i have is relatively mild on a 106* lobe seperation. but i need to know if using shorty headers is going to adversely (negative) affect my 400 over long tube headers.
====================================

the tighter lobe centers
the more overlap period
the Lesser the Compression Ratio
the lower the engine RPM operating range

the more effect header lengths/diameters have on engine performance

 

the tighter lobe centers
the more overlap period
the Lesser the Compression Ratio
the lower the engine RPM operating range

I'm confused by this. I always thought and logically believe
that more overlap is effective in the upper RPM range.

Because of the extended overlap, wont the exhaust pressure
be generally higher at low RPM due to lower exhaust gas velocity?

Once RPM builds and allows for more exit velocity, will this not
improve VE% at higher RPM?

 

I'm confused by this. I always thought and logically believe
that more overlap is effective in the upper RPM range.
-----------------------------------------------------------------------
yes ...but also the opposite=> the more overlap period ...the more time there is for exhaust dilution/contamination of
incoming air/fuel mixture if positive pressure wave exist during overlap because of incorrect header lengths/diameters at "lower RPM ranges"

Low RPM = more time

more time = wrong lengths/diameters "can" really make big losses

at lower rpms

 

maybe i should have posted it this way ;

1-the tighter lobe centers
2-the more overlap period
3-the Lesser the Compression Ratio
4-the lower the engine RPM operating range

with conditions 1, 2, 3, and 4 results in the following ;

the more effect header lengths/diameters have on engine performance

 

soooooooo can i get away with shorties or am i better off going with the Hooker Super Comps like i was going to go with. the shorties would just be easier to install. But if i have to I'll just fabricate off from the Super Comps.
i'll list my entire engine combo if it helps
.040" over 400
deck is set at 9.005"(.005" deck hieght)
5.565 rods
forged TRW 2552 dished pistons
Childs&Albert ZGTF sero gap 1 piece rings(file fitted)
COMP 270H 224@.050" 106* LSA installed at 102*LCA
SR torquer Heads 67 CCs, 2.02/1.6 pocket ported/bowl blend, valves back cut and Exh.valve radiused(face)Int.valve straight cut(face), 3 angle valve job, polished chambers.
Comp magnum rockers 1.6 INT/1.5 EXH
RPM air gap intake
holley street avenger 770
HEI with MSD moduel and MSD coil.
I beleive this combo is worth about 390HP/470 LBS torque, of course with the correct headers.
SO which headers do you recomend?
the hooker Super Comps are 30" long and 1 3/4" primary