NA Engines: Factors that increase torque

[pamotorman]

On my truck block offshore motors we did heads, cams, intakes and cubic inches and blowers with intercoolers
and I agree with you 100%
Inboard/ outboard
too much cam is bad

x2 on intercoolers as you have a unlimited supply of cold water why not use it

[Zmechanic]

Ehh..
"In terms of total charge density coming from intake, for a N/A engine that's TO THE MAX with 127% VE (as compared to pumping displacement), the rule of thumb breakdown is:
100% cylinder displacement
4% Fill of combustion chamber
18% Inertial ramming
5% Wave tuning "

I was writing the question about all those statements how the hell you define them separetely (like how the Inertial ramming isn't the wave tunining.closely related but not all the same.
But

Whoa. This thread came back around. I forgot I even said this in here. The list was not meant to be an indicator that you get to just tweak those levers completely independently. Rather, it's a way to see how much each effect contributes to the overall greater than 100% VE number. Or thought of another way, those are the amounts of VE gain you can get if you harness each of those effects as close to ideally as possible.

The inertial ramming and wave tuning are dependent on very many of the same design parameters, so you're not really going to be able to get just one or the other unless you take the system to a crazy corner case.

[Race Engines]

A specific real-world example: Larry Widmer's work on the Honda B16 4-valve DOHC has shown (at least to his satisfaction, and he's smarter than I am) that a single slot connecting the 2 intake valve reliefs improves power despite the chamber volume increase and resultant loss of static CR - the flow leaving the valves improves by getting dome material far away from them whenever possible.

</rant>

Do you have a pic of that slot to show?

[MadBill]

The cover of David Vizard's latest BBC book illustrates the concept of 'porting' a big intake valve relief for better overlap flow.

[ajbeng]

Resurrecting an old thread, on an old BMC 2 valve with a heart shape flat floor combustion chamber where the plug is way off centre at the edge of the chamber angled in, you are aways limited with compression on a track focused engine because the head starts getting thin and the only pistons available are flat tops which obviously if run +.005” give good squish, but I keep thinking if you where to open the chamber up by tapering the walls out to meet the gasket & designing a piston with a tapered crown that protruded into the chamber angled towards the plug, you would loose squish but gain quench & CR which would hopefully speed up the flame travel gaining power……

Does my theory work?

[mag2555]

You would be reducing a factor in terms of intake air flow called pressure recovery even more so then what might be taking place from not having a heart shaped chamber FLOOR in doing that.

Have you experimented with a long reach plug ?

Even if you had to roll over the extra unused threads that might stick out into the chamber so as to not have glowing hot spots this would be something to try.

If you find a plug that could be used in this way you might want to start off with a one step colder plug just to be on the safe side .

Can you post up a picture of this chamber if you would?

[ajbeng]

The first 2 are what I had the idea of doing, the 4th photo is the current heart shaped chamber setup, obviously the BMC B series isn’t a crossflow so that doesn’t help matters, & the 3rd photo is a late 2v 4 cylinder combustion chamber, similar to the chambers used by Volkswagen in their late pre crossflow 8v golf engines.

[ajbeng]

Yep use a long reach plug already.

[gunt]

i think there is more in the question
increase torque , trough out the rpm range , or a peek tq number , do you want this in a rpm range , or just torque , as in under 5252 , or torque to drive up hp at higher bhp at revs

[Tom68]

i think there is more in the question
increase torque , trough out the rpm range , or a peek tq number , do you want this in a rpm range , or just torque , as in under 5252 , or torque to drive up hp at higher bhp at revs

I'm picking up bits and pieces but I'd love to see a discussion with a full list of engine building decisions that can help to maximize torque and a rough idea of just how impactful each decision is.

Forced induction and increased displacement are the obvious gains, so let's leave them off of the table. In a naturally aspirated engine, for a given displacement, what are the design decisions that can increase engine torque output? (What do we start to see in nA engines with ft lbs:cubic inch ratios of 1.3:1-1.5:1 or even higher if that's possible...?)


Here's my starting list of things that I've heard increase torque (or prevent torque loss to ultimately result in more flywheel torque), but I don't have a great understanding of how impactful these are:

[*]Exhaust tuning -my understanding is this is always step #1 and the most impactful or one of the most impactful items
[*]Compression ratio- kind of obvious, right?
[*]Intake tuning- Long runner tuned lengths when you want to stuff the most air possible in an NA cylinder
[*]Head and intake design that focuses on flow VELOCITY
[*]Efficient fast burn, high swirl combustion chambers that burn quickly
[*]Piston & ring packages that prevent leakage AND minimize friction- [edit]just read an article that showed 10+ft lbs improvement across the whole RPM range from using zero gap seal rings-way more than I expected
[*]All engine friction reduction - less power loss
[*]Well-timed sequential port fuel injection events- improves low RPM torque, anyway
[*]Piston top shape? -I've heard whispers and rumors that dished pistons of certain shapes may make for a faster burn that enhances torque slightly (pistons that mirror the shape of the chamber above, for example) -I'd LOVE any assessment of how much this helps; I'd imagine its incredibly minor
[*]Rod Length?
[*]Cylinder height to width ratios?
[*]Colder intake air charge -improves torque across the RPM range, correct?

In the same vein: If faster burns increase torque does that mean that higher octane fuel, which burns slower, decreases torque?


Adam

If some of the factors in the list simply move torque around then call that out; if they maximize torque across the RPM range (like better sealing rings and colder air intake temps) then call that out to.

This is about learning about theory and just getting a "brain dump" about factors that impact torque, so no need to "choose an RPM.
Adam

[gunt]

ok so i missed that

well then , compression , highest airflow with the smallest CSA and a small cam to run the rpm range , both manifolds will be a factor , then as you want hp you move the tq up the rpm range with changing the cams / and manifolds again with the end result redowing the head and cams from there all depending on where you want the rpm range .
but all the factors like ring seal and so on will machening will result in more tq no matter what the rpm range is

there is a debate for deck height as weather an engine will achieve will achieve ture dynamic rotating compression ,
we have a specific engine widly used in rallying and it lacks in tq but always reved to 10,000 , as you can imagine at this rpm any increase in tq will give big gains , so we are stroking +2mm and not boreing as much as to keep with in clasification , and see where this leeds us ,
i reckon this will change alot of other items