ALFAGTV6.COM

[gtv-racer]

It's looking good. That's a lot of supercharger belt, slippage won't be a problem!

Greg,
http://www.hiperformancestore.com
http://www.okinjectors.com

Thanks Greg!

Did the belt calculations from your book. Lot's of good info there!

[Duk]

You will probably find a few interesting challenges because of having a very large volume between the throttle body and the intake valves.
Idle speed control is difficult if you plan for it to be controlled by bleeding air into the system near the TB.
If you are using an ECU controlled valve (either stepper motor or PWM), you can end up with some unfortunate hunting. When the engine speed slows down, the computer starts to bleed in more air. Because of the distance the air has to travel, the engine speed can continue to drop before the air reaches the cylinders, so the computer may open the idle speed control valve more/longer. By then the initial bit of air has started to reach the cylinders closely followed by the greater amount of air that was also let in. This results is the engine revving much higher than it should and the computer compensates by cutting off all idle speed control air flow and then the engine drops speed. When engine speed drops enough, the idle speed control again tries to do its thing and the cycle starts again. End result = 1 hunting engine.

The potential solution is if you can use ignition timing to control idle speed. Having the idle speed control valve much nearer to the plenum chamber may also help.

Another bit of fun that again comes from having that large post TB volume is that after closing the throttle from a full throttle high rev burst (like during a gear change), the engine speed can sometimes hang rather than drop off straight away. Using a closed throttle deceleration fuel cut feature can help a lot here.

[Greg Gordon]

I have actually dealt with this issue on my dad's supercharged Nord. We had about the same amount of plumbing from the throttle to the intake valve and less engine displacement to deal with it. Here is what I found and what I did.

First of all, we used a MANUAL idle control valve. Pull it out (open) for cold starts and warm up. Shove it in once the engine is warm. This totally eliminates any issues with the ECU getting confused about where to position the valve. Problem solved.

Next, as Duk mentions, use your systems fuel cut feature to cut off fuel with the throttle closed at about 2000rpm. That way you get instant throttle closed response even though there is still a lot of air to get ingested when you let off the throttle.

Set the fuel to come back on about 300-400rpm above idle speed. Otherwise it will drop way below idle and have to climb back up and hunt for a while.

If these things are done it will behave perfectly EXCEPT when you let off on the throttle below 2000rpm, then there will be a slight delay in response, but at that RPM it's just not a big deal.

I think the current version of my book explains some of this. If not I need to update it.

Of course all this goes out the window with high overlap cams.

Also, I want to clarify, response to increasing throttle is never the issue here. It's closing the throttle that can cause some chaos.

Greg,
http://www.hiperformancestore.com
http://www.okinjectors.com

[gtv-racer]

oke guys, i'll keep that in mind. Never even thought of this. But i am a rookie so i afford this
thanks!

Today it is mounting interior day. My back was not so happy while engine tuning and lieing in the car on the backbeam beneath the back seats...

Hope it is on the road at xmas. That's if they are not salting the roads.... Damn winter.

[gtv-racer]

some new updates. Built myself an whole new intake manifold. Its a dual plenium style one for better prearure distributian.

The original one had to less space between the hood an manifold. And a water intecooler has so much advantages. So i built one in right away.

Some pics now:

So this is built in the manifold for the equal distribution:



in progres:




The end result without finishing :




Gonna test it very soon. The first dive is already done with the original manifold and without the charger on the driveway adn i'm happy:

http://www.youtube.com/watch?v=Cf9NAg4h ... ature=plcp

Supercharger is in now. Let's hoop it al up

[Mats]

So, maybe I don't see the design properly but have you added a wall around the inlet tracts? For added blockage?
Less is more?

[gtv-racer]

So, maybe I don't see the design properly but have you added a wall around the inlet tracts? For added blockage?
Less is more?

yes, but better afr control for al separate cylinders. Very important when you don't use water methanol on stock internals and 0.6 bar, 95 octanet and maybe some more boost i geuss..

[gtv-racer]

short video of supercharger drive:

http://youtu.be/u-2KcTQ6KbQ

And the new pleneum in place:

[Mats]

It would be interesting to have a shoot-out between a plenum like yours and one with the trumpets spaced apart. I believe the problem often is insufficient volume around the trumpet inlet and walls adjacent to them like yours will make it worse.

[gtv-racer]

i'll first see how this one works out. I can alway easely incerease the volume above the trumpety and/or lose the internal walls. The part where the intake runners are is about 120 mm and with preasure chambers it is about 240mm wide. the internal height is about 40mm.So it isn't very small after al. I think because of it's long disign it looks a lot smaller.

[Mats]

This is a video of a plenum simulation a friend of mine did a while back, his job is to simulate turbos and intake parts for major car companies so he knows his shit...

http://www.youtube.com/watch?v=0ft7W_2PbYI&sns=em

As you can see in the video the mass flow around the runner entry when the valve opens is VERY localized and anything that blocks flow or removes volume around the entry will reduce performance. I had a wall about 25mm from my inlet edge and it was very obvious that it was hampering the flow in that runner, moving it 20mm improved things a lot!
The height over the inlet is not as sensitive as the volume on the sides.

[gtv-racer]

oke mats. thanks for the info. So what you say is that i should dump the walls around the trumpets? nice vid. i'll give it a tought! Sounds reasonable. Maybe if it is possible you can let your friend take a quick look at it. if it's not to lot to ask of course? Feal free.

[Mats]

I would love to be able to have him do simulations for me but sadly it won't happen. Mine was done as a sort of skunk work just to check an updated simulations algorithm on the company computer cluster, an over-night run. A once in a lifetime kind of thing. Too bad. It would be incredibly nice to check out different designs.

Since you already have the plenum made, run it and unless you have performance issues never think about it.
If you however cannot let go of the thought, make another plenum according to the large volume around runner entry theory and do an A to B comparison and become a hero in your lifetime (at least to anyone on this forum)!

[gtv-racer]

haha, oke mats. No problem. i Totaly understand it. I'm thinking to add some preasure sensord at 3 places obove the trumpets. If i get pulsed preasure drops i know where there from.
Thanks for the info. It wil help to trouble shoot in the future.

[Mats]

Need to have serious update frequency though...