Intake manifold blues, please chime in.

[93tracerwagon]

Blog - Emerald Adjustable Length Intake Trumpet Development
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[BongoBennie]

Originally Posted by oil pan 4

You may have to do that.
The 16 inch runner isn't even ideal.
You want more like 24 inches of total length to include the runner in the head.
Longer is better for daily driver motors.

So i have been under hood all day and I found I can pull the manifold from the original position above the valve cover towards the firewall which would add 2-4 inches and a slightly tighter transition. It will also bring the manifold over the header and closer to it, but Im sure I can fix it with heat shielding and header wrap. I figure this way Im adding 25% instead of subtracting 75%.

Thank you guys for your help, I really enjoy this forum even though I wouldn't call myself a hypermiler

[iveyjh]

I don't know if this will do you any good but it's how I got length into my intake runners.

[California98Civic]

Originally Posted by ChopStix

What about a cowl induction style hood scoop? They are not truly "race car" inspiring. Plus on an old car they seem to help in the aero department. One would not likely help your newer car's aero. But it might solve your hood clearance problem.

That's kinda what I was proposing too. But design it with the ecomodder purpose of reducing the (already good) angle between the window and hood. For aerodynamic improvement. It is simpler to modestly modify the hood than the manifold. And if the mod can benefit aero in a fuel economy build... seems like a win. Follow aerohead's general model:

[BongoBennie]

I have been so concerned about if the runners were going to be long enough and never really thought about making them longer, the Geo manifold is a work of art in this respect.. I would definitely have to wind the primaries a bit tighter than that though... How much longer are they than stock? And that truck, how bad ass! Hood work does seem the most logical, Im just worried about people messing with it where I park for work, seeing that hood will give people the impression there is a K20 inside although Id like to see their face when they pop the hood.....

Back to runner length.... 16" stock length..... what are the effects of adding 4"? adding 10"?

adding length is much more doable.

[darcane]

Originally Posted by BongoBennie

I have been so concerned about if the runners were going to be long enough and never really thought about making them longer, the Geo manifold is a work of art in this respect.. I would definitely have to wind the primaries a bit tighter than that though... How much longer are they than stock? And that truck, how bad ass! Hood work does seem the most logical, Im just worried about people messing with it where I park for work, seeing that hood will give people the impression there is a K20 inside although Id like to see their face when they pop the hood.....

Back to runner length.... 16" stock length..... what are the effects of adding 4"? adding 10"?

adding length is much more doable.

A reasonable estimation for runner length was developed by empirical testing by Chrysler in the 50's. Simplified version is:

N x L = 84,000

N is the tuned engine rpm
L is the length in inches from the opening of the runner to the valve head.

Assuming you have another 2" from port to valve, that gives you 18" for your stock intake manifold. The above equation puts you at a torque peak of 4700rpm based on my assumption. Which probably isn't too far off, Wikipedia puts the peak torque of the Honda Fit's L15A1 engine at 4800rpm

Adding 4" puts you at overall runner length of 22" which gives a peak torque at about 3800rpm.

Adding 10" puts you at overall runner length of 28" which gives a peak torque at about 3000rpm.

Keep in mind this is simplified, but it should be good enough for an estimate.

[BongoBennie]

Originally Posted by darcane

A reasonable estimation for runner length was developed by empirical testing by Chrysler in the 50's. Simplified version is:

N x L = 84,000

N is the tuned engine rpm
L is the length in inches from the opening of the runner to the valve head.

Assuming you have another 2" from port to valve, that gives you 18" for your stock intake manifold. The above equation puts you at a torque peak of 4700rpm based on my assumption. Which probably isn't too far off, Wikipedia puts the peak torque of the Honda Fit's L15A1 engine at 4800rpm

Adding 4" puts you at overall runner length of 22" which gives a peak torque at about 3800rpm.

Adding 10" puts you at overall runner length of 28" which gives a peak torque at about 3000rpm.

Keep in mind this is simplified, but it should be good enough for an estimate.

With all the description I still don't know what that translates into in the drivers seat, the looking at the geo manifold I wonder what that car feels like? are the tires going to squeal off the line now? Will the auto trans shift late? I assume it will feel a bit choke on the high end, will it affect shifting under a full throttle run (like will it never shift)?
Judging buy the craftsmanship of the people posting, I don't think anyone here is BSing in the least, Im headed to shop to look at how long I can make it using the factory upper.

[BongoBennie]

OK Im back, Got busy with the cutter and it basically fits within 2-3 inches, I will have short tubes welded on the original head flange and chop the intake is I can try the shortest possible AND the longer possible very easily, I build a loop big enough to double the length. I will use silicone couplers like the SHO manifold pictured I will ALSO be able to make the 3" version rather simply, DBW FTW!

So in the end I can only ask this, If I double the length, what happens to your 1/4 mile ET, MPH, 60 ft? What happens to 65mph cruising and passing power? This car did surprisingly well at 90mph when it was stock, gotta love the aero.

I do have a second Insight as well, it will be a D15 turbo (GT2554r) CNG and Flexfuel bi-fuel system, tri-fuel if you will and 200hp, will be geared really tall as well. I will do that build thread here.

[93tracerwagon]

They will tell you probably all you need to know about the effect of changing the lengths of the runners and the main intake tube to the throttle body.

[gone-ot]

FE is in the lower RPMs...HP (ET & MPH) are in the higher RPMs.