Factors for low end power gain/loss

[JiP]

Was going to post this under "Heads up"..but decided its new topic time..

A 2g head is better for the '64 block because you'll get better low end torque. The 1g head will feel less powerful in the lower end of the power band where you actually keep the engine most of the time. But it's a matter of choice really. The 1g intake side flows better, the 2g exhaust side flows better. Most people use 1g intake stuff, and 2g exhaust stuff. I think the best combo is a 2g head, 1g TB, 1g intake mani, 2g turbo mani.

This is where I get confused...what factors attribute to low end power gain or loss? Even a cai makes you lose low end power...but why? Cause in my head I can only see that there would be increased airflow across all rpms and therefore should be increased power across all ranges.

[Kain]

Well, how good is your grasp of physics and chemistry?

If it's as poor as mine, you probably wouldn't understand the full explanation, but I'll give a crack at giving the readers digest version.

See, it's all about the mixture of air and fuel, as well as how well it fills the cylinder. When you add more air flow, the cylinders can get completely filled at lower RPMs and it takes more effort to suck in and blow it back out. But, at higher RPMs since the whole process is happening at a much faster rate better air flow allows more optimal filling of the cylinder. Too much air/fuel mixture is bad, because you're "choking" the engine. Too little, and it's gasping. Kinda like when you breathe. You don't want to breathe as deeply as you can all the time now do you? But at the same time when you're running a marathon you don't wanna be breathing through a straw. An engine is kinda the same way. Make sense?

[JiP]

Kinda makes sense. If im understand correctly, the low end power loss is because you are filling the whole chamber up with air which is a good thing...but that takes more energy to expell the air efficiently after combustion so thats why it drags the engine??

[seth98esT]

can you guys please talk about this here I am trying to compile all talk about headswaps here

[JiP]

<div class='quotetop'>QUOTE(seth)</div><div class='quotemain'>can you guys please talk about this here Â*I am trying to compile all talk about headswaps here

</div>

But this isnt about headswaps this is about low end power for all mods. From head's to cai's

[Dark Anghell]

<div class='quotetop'>QUOTE(JiP)</div><div class='quotemain'>Kinda makes sense. Â*If im understand correctly, the low end power loss is because you are filling the whole chamber up with air which is a good thing...but that takes more energy to expell the air efficiently after combustion so thats why it drags the engine??</div>
I'm not sure if this is 100% correct. Because if you think about it, when you have supercharger installed on the car, it provides large amounts of compressed air into the engine. The amount of air is constant because the supercharger is driven by the engine, and after a certain point it doesn't produce any extra HP, that's why superchargers ase so great for track and any even that requires low-end power.
So what in the world am I talking about? If supercharger gives extra air even at idle, and still produces HP, how can an air filter which does the same thing make you loose your low-end power. You will actually gain it. But to make the most out of the filter and exaust you need proper tunning. I noticed that galats run a little rich at higher rpm, so when i turned down the fuel for 1-4000RPM range, i saw some little inmprovement in the way the car feels.

[JiP]

Pav the way you wrote your reply is the way I am thinking however it can not be correct. If you do a quick search on the web for "losing low end cai" or something like that, million sites come up talkin about adding aftermarket filter setup gaining mid and high end power and minimal loss of low end. In my case low end power sucked, horrible response even fiddling with the afc didnt improve things. If what Kain said is correct and i understood it correctly, (it makes more sense to me), then an upgraded exhaust system would make a big difference with allowing the new larger amount of air in the chamber to be explled easier. uh..i think.

[jiul]

Hey Kain, what you say about air extraction is true, but it is true about all heads ( and all engines for that matter).
So why do 2g heads evacuate faster or beeter then 1g?
Bigger ports, bigger valves, different flow pattern. different cams, I mean what exactly is the difference ?
If this question is silly I am sorry but I know nothing of either 1 g or 2g Dohc heads.

[Kain]

<div class='quotetop'>QUOTE(jiul)</div><div class='quotemain'>Hey Kain, what you say about air extraction is true, but it is true about all heads ( and all engines for that matter).
So why do 2g heads evacuate faster or beeter then 1g? Â*
Bigger ports, bigger valves, different flow pattern. different cams, I mean what exactly is the difference ?
If this question is silly I am sorry but I know nothing of either 1 g or 2g Dohc heads.</div>


2g heads actually flow less well than 1g. That increases bottom end torque. Kinda like the opposite of Honda engines. Like the '64 is stock (hp/torque numbers similar) They have smaller ports (can be rectified with machine work) and I think smaller valves on the 2g. I'm like you and know relatively little about the DSM heads. I'm just reiterating what I've gleaned from guys who have worked with them. All I know is when you get too much flow you get a "Honda-esq" engine that has huge top end power, but feels sluggish on takeoff. That's not good for a street driven car in my opinion.

[jiul]

I have deffinetly read that porting 2 g heads can hurt low end performance, I just haveno clue as to why?

Now I am trying to figure this out logically ( not my strong point LOL) and all I can come up with is more questions.
1) the bigger ports somehow prevent full combustion not probable.
2) the bigger posrts somehow affect the entry flow of mixture into the chamber, more probable.
3) I have no clue and I am dying to find out from someone who knows.

[jiul]

<div class='quotetop'>QUOTE(JiP)</div><div class='quotemain'>Pav the way you wrote your reply is the way I am thinking however it can not be correct. Â*If you do a quick search on the web for "losing low end cai" or something like that, million sites come up talkin about adding aftermarket filter setup gaining mid and high end power and minimal loss of low end. Â*In my case low end power sucked, horrible response even fiddling with the afc didnt improve things. Â*If what Kain said is correct and i understood it correctly, (it makes more sense to me), then an upgraded exhaust system would make a big difference with allowing the new larger amount of air in the chamber to be explled easier. Â* uh..i think.</div>

JIp, when you say an updated exhaust system what do you mean? Kain says that bigger exhaust ports hurt low end, so what exactly would you update? Hedder length maybe?

[Kain]

Restricting intake/opening exhaust = more low-end torque, less top end hp I.E. the way the Galant is when completely stock.

Opening intake/restricting exhaust = less low-end torque, more top end hp. Most modern cars that have more hp than torque

Like I said, this also has to do with Chemistry, as in air/fuel mixture. As well as scavenging effects within the cylinders. And the whole thing gets really funky when you start forcing the intake charge into the cylinders or changing up the chemistry with a foreign substance (nitrous). If I had a better grasp on the whole thing I could explain it better, unfortunately I just don't know how to explain it better.

[JiP]

What I'm saying is:

opening intake/ opening exhaust, should even out and give you both hp gain as well as torque.

When I mean upgraded exhaust I mean a header, downpipe, maybe even port the exhaust side of the head to make it flow better this way you are not as kain said having a big intake with restrictive exhaust and thus losing low end torque.

Logically I would think that having a larger intake would require a larger exhaust. However I think the 1g and 2g heads exhaust side are the same size, which would make sense that your losing low end on the 1g head because you have much large intake. So the exhaust side should be opened up and things should even out and see gains in both hp and torque.

[jiul]

OK now its getting really contradictory.
First Kain says that 2 G flow less well then 1G and that's what makes the engine torquier.
Then you, Jip, say that improving flow will make more torque.

[JiP]

OK now its getting really contradictory.
First Kain says that 2 G flow less well then 1G and that's what makes the engine torquier.
Then you, Jip, say that improving flow will make more torque.

I think your kinda missing the concept. Work with me now lol..

The 1g head has much larger intake ports then the 2g. Both have the same size exhaust ports if theres a difference its very little. The 1g head will flow more air into the engine then the 2g obviously because its intake is larger, however being that it has such small exhaust ports, it can not effectivly blow out all the exhaust air. The 2g, having smaller intake will not suck in as much air as the 1g, thus doesnt have that much problem blowing out what it has. Thats why its torque is good, while 1g torque falls in the low end, it cant blow/suck the exhaust quick enough.

Im saying, take that 1g head, and port the exhaust side, so that now you are getting the propper flow on the exhaust side to match the increased airflow entering the engine. This should sole the torque loss issue. Becuase like the 2g smaller intake, with exhaust, the 1g has larger intake, but the same small exhaust of the 2g, it would make more sense that with a larger intake, the exhaust should be slightly enlarged also.

Now how much to port is another question...are there formulas somewhere for this?

[Kain]

The 2g's Turbo manifolds are also better flowing. The 1g's Intake manifold is better, but has a HUGE restriction at the TB elbow (despite having a larger TB). The 2g has a better intake up to the turbo though. So, in the end the best bet is to take the best parts from each and put them all together. It is confusing, but that's also what makes it interesting. I don't think there's a formula, in fact I think most people are still trying to figure out exactly what happens when aftermarket parts are installed (remember, the performance aftermarket as such is barely a decade old) That's why people are constantly doing dyno tests.

[seth98esT]

wheres the restrictiveness in the 1g tb?

it flows straight through...
(actually this is the nt tb, i forget what the turbo tb elbow looks like :oops:)

[JiP]

Kain is refering to the 1g Elbow, which the 2g elbow is a bolt on swap, just like the 2g exhaust manifold. The beauty of the headswap is that it opens up the doors for a bunch more engine performance parts, intakes, cams, springs, cam gears, etc etc..

And there must be some sort of formula to calculate the size of a port needs to be to expell an amount of air, I would guess that porting the exhaust so too much would be a bad thing, like putting a 3" exhaust system on a non turbo car.

[IllestGalant]

I think one way i have heard this put between low end and high end is that wether it is dealing with exhaust or intake... If you have more air at idle going in and coming out and then you add even more air with porting, cold air intake, or heads or whatever, you are loosing vacum because it is a lot harder to pull a vacum from a bucket than a straw ya know. Then once you slam the throttle and the engine draws in more air, the cai, header, head, etc... you are suppling the engine with more room for that extra air resulting in better high end. Or maybe I am just a moron? I like how KAIN said how would we like breathing through a straw when running and how would you like breathing in buckets of air when your sitting down.

[JiP]

This is too confusing. No one has ever been able to really give me a full out answer. All these buckets and straws are making me dizzy