EFI, Crower intake, idle problem

[Hocky]

This is what I got:
Chevrolet 547cui BB
Crower stacked intake with 8 x 2.9" throttle plates. Modifed to EFI and split the axles.
Autronic SM4 EFI
Autronic R500 CDI ignition (8 coils, wastefire)


My problem:
Have made some test starts and tried to get a stable idle. When leaning out the fuel to get to a nice 14.7AFR a get cylinders "sneesing" up thru the intake. I know this is because some cylinders is going too lean
I have made some adjustments to the throttle plates trying to get them all in sync. Have also tried to get them synced with a Uni sync tool.

I know the intake is not 100% in the axles and the plates maybe not all seal 100% but very very close.
I have can not use the idle screws at all and the plates are as closed as they can be. If I open the throttle with the idle screw I get to high idle. Some throttle plates vibrate (opens a little) sometimes and I have a feel that its maybe a plate thats a little to sealed and the cylinder is making the plate open by vacum.

I know that I must make new axle bearing and maybe replace the throttle plates and axles but not now.

Any advice?
Drill a small hole in the throttle plate?
How to get all plates to seal better?

Getting frustrated

Pictures here,
http://www.hocky.se

[camcojb]

As far as the A/F I have never seen an IR EFI setup that was happy idling anywhere near 14.7:1 A/F. Mine wanted to be 12.8-13.2 at idle and was very happy there. It could be 14.7:1 or leaner at cruise areas, but not idle. One thing I learned a long time ago is give the engine what it wants, don't get hung up on the numbers. If it idles better at a richer A/F that what I do.


As far as the idle speed, it's obviously pulling air from somewhere. If you can richen the idle and live with the butterflies closed for now that'd be my suggestion, at least until you can re-do the shafts, etc.

Jody

[lil427z]

take some timming out at idle.
rick k

[Hocky]

Originally Posted by camcojb

As far as the A/F I have never seen an IR EFI setup that was happy idling anywhere near 14.7:1 A/F. Mine wanted to be 12.8-13.2 at idle and was very happy there. It could be 14.7:1 or leaner at cruise areas, but not idle. One thing I learned a long time ago is give the engine what it wants, don't get hung up on the numbers. If it idles better at a richer A/F that what I do.

As far as the idle speed, it's obviously pulling air from somewhere. If you can richen the idle and live with the butterflies closed for now that'd be my suggestion, at least until you can re-do the shafts, etc.

Jody

I noticed that its ideling fine at ~12.5AFR but I can smell it too. I have not made big investements in a one of the best EFIs on the market to live with it

I do believe that even if I get the shafts ok it will not be 100%. When I open the throttle with the idle screw its to unsensitive.
Im considering creating a adjustable pass thru channel bypassing the throttle plate (like on some production cars).

[Hocky]

Originally Posted by lil427z

take some timming out at idle.
rick k

Autronic uses timing to handle the idle. It uses a table with the RPM on the x scale and user configurable y (TPS, MAP, LOAD...).

Now the engine is ideling 900rpm at 10degrees of timing and I do believe that this is rather low already.

I can also make adjustments to each cylinder on the timing or fuel. This is also done in a table with RPM on the x scale and user configurable y (TPS, MAP, LOAD...)
I have tried to put some more fuel (at low TPS) to the cylinders going lean and this is helping some.
When trying to add/reduce timeing on these cylinders I get no effect that I noticed.

[camcojb]

Originally Posted by Hocky

I noticed that its ideling fine at ~12.5AFR but I can smell it too. I have not made big investements in a one of the best EFIs on the market to live with it

My point was that 14.7:1 may not be the ideal A/F for that combo. You can force it there if you like, but that doesn't make it right. Every IR setup I've tuned or seen tuned likes to be richer at idle. Maybe not all the way to 12.5, but definitely not 14.7:1.

I've had cars "smell" at 14.7:1 also.

Jody

[69 L88 Camaro]

You got the engine hot and set the butterflys to be completely closed without it running before you began and know about the beveled edge of the butterfly and the install of them right? Need to know where you are at in this project. How much camshaft?

[Hocky]

Originally Posted by 69 L88 Camaro

You got the engine hot and set the butterflys to be completely closed without it running before you began and know about the beveled edge of the butterfly and the install of them right? Need to know where you are at in this project. How much camshaft?

I have assembled the intake with the butterfly correct I do believe. The beveled edge is more or less totally sealing in the runner.

I have a Lunati solid camshaft. 254, 264 @ 050 and 620, 620 lift, 110 loob separation. In the specs it say rough idle but did not get any problems with my King Demon carb before but i know its not the same.

[69 L88 Camaro]

Hi,
Don't get fustrated with your setup it will just take a littile fine tuning to get your combo happy. The one I have now is a stickshift so it is a little more forgiving about coming down to idle as i jump off the throttle but I will talk about what I have seen. The butterflys will flutter. I have tied my runners together underneath the manifold with 3/8" steel tubing into a common plenum to soften the pulses of the I/R manifold. The plenum is quite large but fits easily even with the roller lifters and splash tray. I have used a plenum on top for power brakes and IAC applications but wanted to hide this one. My butterflys and shafts are quite high like your Crower intake and I try to do all my adjustment HOT. I will back off the idle stops (one per side) and adjust the splitters and cross shaft so all the return spring pressure is on one set of butterflys. Then I loosen the butterfly screws and tap the top of the butterflys with the plastic end of a screwdriver. Not a small screwdriver. Then tighten the butterfly screw. As I move to the next set I tap on the bottom of the butterflys I had just done to help them unstick. You may hear them squeak and pop open as you do. Now close the next set with the splitters and continue setting the butterflys. Start farthest away from the return springs and work your way toward them. Then visually adjust the stops and splitters to fully closed. Crack the butterflys open slightly with the stops and start the engine setting the splitters and stops and cross shaft monitoring the uni-sync. Start farthest away from the return springs. I have had to do this a couple of times but then eveything stabilizes and now all I do is keep the shafts lubed. With the fueling I run open loop at idle and like camcojb said give the engine what it likes. I have tried different timing settings. Retarded softens the engine but heats the exhaust. I use alot of advance. If it is a little smelly at first don't run it in a closed garage. If the I/R intake was easy you would see more of them but when you get this done you will be very proud and happy you took the time to get it "right". With all the throttle blade area this will have alot of power with not much throttle opening. I made a cam type throttle linkage like a 660 Holley tunnel ram carburator secondary to make this less aggressive with the stick. With the automatic it was easier to drive. Let us know about your progress and ask any little question you have. My EFI is setup in Alpha Numeric by the way.

[Hocky]

I have all the runners connected to the MAP sensor now with tubing (only 4mm). Maybe I will get a small plenum on that to slow down the sensor readings, they are not stable at the moment. It probably wont help the idle of the engine but maybe the timing map.

I will try your way of adjusting the throttle plates. I have not tapping the plades the way you do with a screw driver. I used a finger and tapped

How close do you get the cylinders with the uni sync?

Do you get fuel on the underside of you throttle plates when fully adjusted?

Tnx
Hocky