Don Terrill’s Speed-Talk

Larry, is there a change in required induction length if you increase the charge density with boost like a twin-turbo setup feeding into a single-plane intake on a SBC?

I’m running MAF sensors in my car with EFI and then lambda sensors in the exhaust. I’m thinking that both those together allow me to determine the mass air flow and fuel flow rates with sufficient accuracy. I do also have the “air turbines” aka turbos which have speed sensors, temp probes, and pressure sensors — for second opinion on ingested air mass. Fuel pressure, injector pulse width, and injector flow table give a second opinion on fuel flow.

The one thing that I’m having difficulty with is figuring out how much charge gets thru to exhaust during the overlap and how much hot exhaust gas remains in the chambers. I’m octane limited, so every time I get more charge trapped or I leave more hot exhaust in the combustion chamber, I must retard the ignition. Because the ignition advance has to be changed, I’m having hard time figuring the gas exchange and trapped charge from the torque that the engine produces.

I have Pro 4.50. Is there any way to add merge collectors to the exhaust system and how does that effect the collector tuning?

Since you say low rpm applications it’s critical to get it right, can you show an example of one from a high TQ towing application?

Say from 2500 thru 4800..where the cruise rpm is 2500(max efficiency)and needs a broad TQ curve from cruise rpm to about 4800 max?

Would it give a tri-y spec and long tube 4 into 1?

Did you gain VE through the entire RPM band on the engines or did you lose at higher RPM:s?

Erland

Coincidentally, they were testing collector extension length on Engine Masters this week. They also tested the "paint a stripe on it and where it burns off is where to cut" theory. It was wayyyyy off on the smaller headers they tested. It wanted 24"+ long extensions but the paint burned off after 8 inches.

midnightbluS10 wrote: ↑Sun Sep 06, 2020 5:29 pm Coincidentally, they were testing collector extension length on Engine Masters this week. They also tested the "paint a stripe on it and where it burns off is where to cut" theory. It was wayyyyy off on the smaller headers they tested. It wanted 24"+ long extensions but the paint burned off after 8 inches.

Internet went down here last nite ... just got it back !
Wow , i see a lot of questions

midnightbluS10 , do you have a Link for that Engine Master's test ???

i need to find my Pics and Post ... i did a few tests like that
and i just used a spray can of Krylon Chevrolet Orange paint
and painted a long orange stripe about the length of the Collector .

Here's how i recommend doing it :
make enough Dyno Pulls on your Engine and get it maxed-out on tuning
with your Headers like they are , then have your add-on Collectors/Bolts/Nuts/Gaskets
wrenches, all ready to go , so you can quickly put on the Collectors,
and quickly make another Dyno Pull while Engine is up to temp !

big reason : this Dyno test will only be valid if its made under Full Throttle
and Dyno Load , and quickly done !!! .... so that any extended time warming up your engine
can already start discoloring the orange paint in the wrong area/length because the Engine
is not operating in its RPM Range , and not under Full-Throttle, Full Load yet .

i did some tests like this on my own on a few different Engines ,
and i did a few more, much better Dyno tests , with Chris @ C&S Perf,
with brand new 4 feet long Collector extensions that you didn't even need to paint them,
the new Tubes showed discoloration mark/location easily , still we painted a stripe
just to make sure . We did all the testing like i just described above .

By absolute "Luck" or 50/50 chance ,
the discoloration mark seems to show the correct location to cutoff the Collector part,
we got fooled twice on 2 engines With Chris's Customer wanting to test this ,
we cutoff the Collector where it discolored , repainted over the stripe,
made another Pull, and it picked up TQ and HP ( by Luck ) ... but this time the discolored mark moved further up the Collector ,
so we cutoff that piece there , made another pull , and lost a bunch of TQ ,
repainted over the stripe , made another pull , discolor mark moved up again further up the collector,
cutoff that piece , made another pull , lost even more TQ and HP,
so i told his Customer , i'll give you a free dyno if you let me do 1 more Test
... start cutting off part his real Collector ( not the add-ons ),
( Chris said, 'Ill have my Guy welded it back on if it doesn't work )
Customer said OK, painted a stripe, made a Pull , cut-off part of his real Collector ,
lost even more TQ

i said we could keep doing this painting and cutting till theres no Header Tubes left
all the way to the exhaust ports , the discolor mark will just keep moving
towards the exhaust Ports ! i asked him if he wanted to keep going , he said no , i seen what i wanted to see

 

When Pipemax calculate the waves does the program calculate the wave velocity versus the flow velocity?
Faster outward travel on exhaust and reflection and return can take 6 times the time the trip out took.
Same on intake, Wave travels against flow on valve open and with flow after reflection.

Erland

Erland Cox wrote: ↑Mon Sep 07, 2020 2:20 pm When Pipemax calculate the waves does the program calculate the wave velocity versus the flow velocity?
Faster outward travel on exhaust and reflection and return can take 6 times the time the trip out took.
Same on intake, Wave travels against flow on valve open and with flow after reflection.
Erland

by Erland Cox » Sun Sep 06, 2020 3:10 pm
Did you gain VE through the entire RPM band on the engines
or did you lose at higher RPM:s?
Erland

hi Erland , i could not exactly tell if you were asking me "Did you gain VE through the entire RPM band on the engines
or did you lose at higher RPM:s?"... or the previous Poster ??

but remember that NHRA SS Hemi many years ago that had 140+ VE on my Dyno , but 20%VE was going out the exhaust,
it picked up a whole bunch of HP with spreading the Cam Centers , lost 20% VE in process , but picked up a bunch of HP

if you look at this BBC Dyno comparison pic in this Thread ... notice that with add-on Collector , there are some upper RPM points
where the add-on Collector hurt the VE% ... but HP still increased .... this effect is same as the SS Hemi ...
both Customer's Intake and especially Exhaust Lobes had too much Durations ... increasing some of Mixture going right out the exhaust Ports
( overscavenging ) , but the Air Turbine shows an increase in VE% and CFM, but some is going out the exhaust Ports !
So TQ and HP are decreasing !

Click on this Link to see Pic :
download/file.php?id=25135&mode=view
---------------------

Yes PipeMax calculates both Wave FPS velocity ( superimposed ontop ) and Gas Flow FPS velocity
and i did see some of that effect you stated ! . ... i changed that in PipeMax v3.98 years ago to reflect that .
Its slightly different at some Harmonic lengths from what i've noticed... its not a constant effect !
So equations have a slight correction .

When Pipemax calculates VE, is it trapped VE and not false VE with blow through losses?

Erland

Erland Cox wrote: ↑Mon Sep 07, 2020 3:39 pm When Pipemax calculates VE, is it trapped VE and not false VE with blow through losses?

Erland

its always Trapped VE it calculates
it can be reversed-engineered if you have very accurate
Fuel Consumed Lbs/Hour + Flow numbers + Port FPS, BSFC, Air/Fuel Ratio , and Dyno day weather conditions

i'm making it a lot easier in version 5.0, but it will be months away .

Is Pipemax going to get smart enough to predict and warn for overscavenge?

Erland

Erland Cox wrote: ↑Mon Sep 07, 2020 4:21 pm Is Pipemax going to get smart enough to predict and warn for overscavenge?

Erland

it should be doing that now !

also : "its always Trapped VE it calculates"
let me correct a little , its "Potential Trapped Volumetric Efficiency % PerCent" termed in v4.50, but will be "actual Trapped VE%" if and only if
you measure both Intake and Exhaust CenterLine Lengths + their corresponding CC volumes
then adjust Port velocity FPS input values until you get exact matchup between PipeMax and your measured Port Volumes .

input what Cyl Heads Flowtested at Cam's theoretical max Valve Lifts without correcting for Valve Lash

you must always input actual Weather conditions
then in Weather Calculator click [ Apply ] in Menubar ,, then cliclk [Recalculate VE% + Apply ... etc ] choice
then adjust [ Intake System Volumetric Efficiency % PerCent Loss ] value until you get exact matchup
between PipeMax's Peak HP and your Engine Dyno flywheel BHP Peak HP number

and finally you adjust Air/Fuel Ratio a little at a time until PipeMax's calculated
Fuel Consumed Lbs/Hour + BSFC both exactly matchup to your Engine Dyno Data ,

then that is your actual Trapped VE%
and should be real Air/Fuel Ratio it took to correlate all this !

i know its now a big "Hassle" all these Steps
but v5.0 will be a bunch easier, and very much greater overall accuracy

I have another question about V4.50.

Is there any way to use a stepped primary tube?

frnkeore wrote: ↑Sat Sep 12, 2020 2:50 pm I have another question about V4.50.

Is there any way to use a stepped primary tube?

i hope i understand your question correctly ?
it seems a strange question ??

its very easy in PipeMax v4.00 to v4.50.... just choose it
this choice in 3rd column ( under EXHAUST DATA )
( Default= Race Header • Single Tube diameter size )
then choose
Race Header • Mutiple Steps

Race Step Header ... calculates 2 or 3 Step style Header Specs
Race Step Header with Muffler .... 2 or 3 Step style Header Specs , includes exhaust system specs along with H-Pipe and X-Pipe locations