Well I do have a spare TB with all the trimmings, maybe I'll throw that on there this weekend and see what happens. My idle doesn't go higher than 1700 or so for more than a second or two at the most so its not out of control, just weird. It may be getting a tiny little leak from somewhere I haven't found yet, but i doubt it. Whenever you remove or replace a TB you do the PCM/idle relearn procedure, it basically allows the ECU to read the idle characteristics of the engine and adjust itself accordingly.

 

while you're at it, you should see if the ge tb fits

 

I don't see any reason why it wouldn't fit, but I don't know what benefit would be found from using one either. That and no one has one they will sell me for CHEAP. I paid next to nothing for the spare TB I have for the GD and it came ready to bolt on.....

 

from what i've heard (possibly just rumor) it's a bit bigger with a bigger butterfly...

but i haven't seen one to verify... yeah finding them cheap right now will be a problem...

 

Just as a follow up the idle relearning procedure was definitely worth. Today I've been driving the car and she was much more responsive than I remind, with 2 adults, 2 babies and aircon on. So far, so good. This week I'll have the pulleys and flywheel replaced, hope to get something good to report

P.S.: I payed attention to the high idling period/blue led at cold start: it lasts about 2 minutes. This ECU setting seems really dummy: yesterday there were about 30°C and I bet 1 minute warm up would be way more than adequate, especially because I never warm up when still, I simply drive smooth and keeping low revs (shift at 2K) until blue light turns off. But this ECU setting doesn't seem to me so smart...

 

it is there to "just to" keep an even flow!!!!!!!!!!

the heart has valves "just to" pump blood evenly

 

An update for the masses of people who care LOL The manifold is holding up well, no leaks or problems with appproximately 8,000 miles of daily use under its belt. As the temps have begun to climb into the 90s here I am watching with interest to see if anything changes (or blows up) The single largest benefit I have seen is that the A/C no longer effects the cars ability to get up to speed, and maintain speed once there. My fuel economy has remained at a steady 40 MPG throughout, seldom dropping below 37 (with heavy A/C use) The code 0507 CEL continues to elude my efforts to cure it, but it doesn't seem to hurt anything so I haven't killed myself trying. As time has gone by the CEL returns after being cleared sooner and sooner, leading me to believe that the problem is in fact a sensor attached to the TB responsible for idle speed (if there is such an animal)

 

And it turns out I was wrong again! Imagine that. The top of the manifold where I accidentally ground through had begun to leak again. The uber-glue i used to patch the holes had hardened and settled through the holes and was screwing up idle vacuum. A fresh application of glue and shes as good as new! Maybe better in that this time i made SURE the mother ain't leakin' I was rewarded today with a drive to work that wasn't interuppted by the CEL. Yay!

 

So, did you gain some power by modifying the stock upper plenum? More torque? Better Responce maybe?

Marko!!

 

Marko, Any gains are in the top of the power band, up high on the tach. The car pulls significantly harder from 4K to redline now than it did before the modifications. I can't quantify the gains as I have never dynoed the car. Maybe someday when I have the time and money.

 

...and below 4K does she loose anything?

BTW I would be interested in swapping my small plastic runners with L15A metal(?) one and checking the differences...

 

You know he was talking about experimenting with smaller runners awhile back..... Maybe there was a low end power loss then, but his manifold was leaking at the time.... I was wondering the same thing as you about how it was under 4K.

 

A friend of mine borrowed me an old book about engine modding (when electronic was not yet an option) showing the ideal geometry for runners. On the web I found something about runners length, but not yet anything on internal geometry.

I'm trying to link a scan of the page showing ideal internal runner geometry. Any comment/idea? I'm very skeptical Honda and aftermarket vendors have runners with such a geometry...

Picasa Web Albums - seppstefano - Engine Modding

 

In the very old days of big valves, high compression ratios and 108 octane leaded gasoline, flow velocity was not as important as flow volume and in the early sixties long tube manifolds started showing up on American high performance engines as a way to increase flow velocity but the runners were still uniform in diameter for the full length... I think that there was more experimentation on the flow benches of motorcycle racers than by automobile racers mainly because there was less work involved and back then auto heads and intake manifolds were of cast iron and motorcycles were of aluminum and easier to work with plus motorcycles were air cooled and couldn't run the high compression needed to make power with long duration racing cams and so they realized the need for flow velocity to broaden the power band of their engines and utilized velocity stacks and the type of shaped runners as what is in the picture you posted... Squeezing the flow gradually as pictured and the gradual expansion in diameter to match the port opening will put more air into the combustion chamber that of a runner of uniform diameter. It's hard to do 4 of them and get them to be all flowing the exact same amount of air so it is best to remove material in very small increments doing a portion of at a time on all of them and then proceed to do another small portion one at a time as many times as it takes.... It is easier to remove material than replace it..... On some cylinder heads metal has to be added before port shaping can be done and depending upon the power characteristics you desire, intake runners could be likewise.

 

I have experienced no loss of power below 4K. I still haven't got around to trying the runner diameter reduction experiment, but it is coming soon. Reason being that the dreaded 0507 has returned again! I know it is because of the holes in to manifold roof that I made by accident. Plugging them has proven nigh on impossible over the long haul. Sooooooo, I'm gonna cut open my other manifold and mod that one! This time I'll be more careful with the grinder LOL . My plan is to glue PVC pipe into the runners coming off the manifold to size them down by about 1/4 inch. This should be a lot easier than messing with the aluminum lower runner, which is obviously curved. If I see some kind of positive result, I may get the lower runner extrude honed to a degree, but not as radical as the upper mani. I don't think the engine can use THAT much air without a cam swap and some serious tuning.

 

I wonder how it would have been worse! My ''improved'' DC Sports header gave me a fair amount of torque, but i think that the Intake manifold and ECU are holding me back now!! I can't hardly wait to work on, at least, one of those two issues!! :P And if i could take the time to modify my Fujita Short Ram to act like a cold-air, or direct cold air on it, i think it could'nt hurt either as my Scan-Tool tells me that my IAT (Intake Air Temperature) are in the 90° range.... And it is commonly known now that every 10° drop of IAT give +- 1% increase in power... Not much, but it could only cost a couple of dollars at the hardware shop!! Like a certain Cold Air Intake i did on a friend's Escort ZX2 with a couple feets of Shop Vac hose on the stock airbox!!

Marko!!

 

I am still working on my Frankenbox intake. When finished it will mate the OE airbox with a ram air scoop to the Rogue cowl scoop I have. I want to try this route because the A-Spec CAI I have is really only a sorta not so hot intake when you get right down to it. The filter sits an inch off the transmission, so after a hour of driving the IAT is about thirty degrees cooler than the water temps! Do the math on that one kids! I don't want to think of how much power i'm losing....

 

On my Fujita SRI, IAT are going in the 115 - 120°f range when standing still in the traffic jams... when i'm at highway speeds, it's dropping in the 80 - 90° range!! But there is still power to be gained there!!

Marko!!

 

Hi all,
Marko, how did you tweak the DC header? Did you wrap or coat or what else?

Ah, BTW the lightened flywheel and pulleys I mentioned a while ago let my small 1.246cc engine rev much better. Car feels really lighter.

 

Where can I find info on valve and runners diameters for the several engines of Jazz/Fit?

Do you think that a silicon hose would be functional as an "experimental" runner?

Stefano