Thread: Curious Question..Long

Ok so your saying that causing a faster burn would make partial throttle gas mileage poor?


Interesting, because the article said the less timing you need generally the leaner you can run the motor given the loss of heat energy.

Danja could you elaborate a bit?


And yes I agree with you, I am not trying to come off as being defensive I just get heated quickly. I really do want to hear what you all have to say, believe me I didn't make this thread to try and prove anyone wrong. And by god I don't actually believe for an instance I know what I'm talking about..however i do trust the credibility of the author of this particular book, unless someone can directly tell me the information i gave was wrong, and why.

Thanks.

Dudeman

When I tore down a VE and looked at all facets of the motor that i could see with the naked eye i started to think about what i could and couldn't do with the motor.

I did a ton of research on swirl, tumble, IM design and header design. (all SAE papers I still have) They were showing ecotec and ford motors and the designs they used and a cross section of the cylinder to show how the mixture swirled into the cylinder.

The best IM design is, unfortunately, unable to fit in our cars because it would hit the firewall. But ferrari has it on their 599 12cyl

I also knew learned that for emissions purposes it's better to have fuel injectors closer to the valves but for all out performance it's better to be farther out (like the N1). you get a better mixture with the injectors farther out and you can have a more complete burn once inside the cylinders. The reason why cars high idle during cold start is because all of the fuel is not being burned. the car must reach optimal temp in order to be efficient. Not such a big deal on an all out race motor which can easily see much higher cyl temps than your average street VE but important to keep in mind if you aren't just driving your car at 5k+rpm all the time.

Promoting swirl can only be modified after the fact. meaning the VE head is still only as good as nissan can make it. We can polish, cut, reweld but you are working within the limitations of a factory system. This is your biggest compromise. You want the most powerful timing event possible so what can you alter?

How much money ya got?

I think it's also far to say the more you modify the more you compromise whether that is part-throttle driving or low rpm driving. So you try to make up for by say...adding displacement?

You may want to go with flat faced valves, add a little compression but you are now getting into the $$ since these aren't necessarily off the shelf parts.

I think the best way for you to have more control over what's going on is valve job, valve work, and piston design.

Bottom line is most average guys looking to build a motor only have 1 chance while 'builders' do this day after day for race teams. There are things you should worry about since you can control them as you buy parts for your motor and there are things you shouldn't worry about since you'll never have 5 motors to compare different set ups and see which one makes the most power because it is producing less 'heat'.

Port match
Flat top pistons
Valve work
Degree cams
Standalone ECU

Those are the things that are going to make you power focusing on anything else is academic and you may gain 1-2% more HP and Torque but the amount of money you would spend to get even more detailed would hurt your pocket even more than a car hobby already does.

donttazmebro and others, what do you guys think of reverse flow injector firing? Meaning firing upstream instead of the standard downstream in a MPFI engine? Would this cause the same effect as placing the injectors farther upstream or is placing the injectors far away as possible the best effect? I saw this somewhere, maybe one of my books. I've never seen anyone doing this though, at least in terms of the SR.

interesting, seeing an sr20 head and block how do you think it would actually fit?

More hypothetical than anything else, just wondering if you guys have done this/seen this done or have knowledge of how effective this is for fuel mixture.


Edit: It's in Maximum Boost, Chapter 6 Intake Manifolds page 80. Corky doesn't say much about it except that "Race applications, however, have occasionally aimed the secondary back upstream. Although data are scarce, this may offer slightly better atomization and is worthy of consideration."

This pertains more to the N1 discussion due to the use of secondary injectors.. but I wonder if just a single injector pointed upstream would create the same effect?

I'm not meaning to threadjack, just thought it would be an ideal time to interject a question on this related issue.

i see what you mean, the electronics involved with that would be scary, i would assume he may be talking about long equal lenght runners. it sounds like it's essentially doing the same thing as moving injectors outward. either way you would have to have 8 injectors since you need the traditional ones to cold start the car

Hey don't worry about it, its all the same bible if you ask me.

That is a very interesting idea, definitely worth looking into.


Dudeman

What about adding a spacer for the intake manifold to lengthen the ports and put the fuel injectors farther from the valves? Wouldn't this work? Using the thermotec spacer will also decrease manifold temps and increase the density of air in the manifold.