Blower / fuel at idle

[32bantam]

Hi Spud.....I have an issue LOL...
Switched my 496 Arias Hemi from a 14/71 std helix (well worn in) to a fresh 16/71 HH retro set back to account for the front cut out. I was running the std. 14/71 at 15 to 20 % OD to make approx. 17 lbs. of boost to go 7.0.  My 14/71 std moved 500 cu.in./rev.  You don't list a 16 on your chart but it looks like each inch of rotor adds about 32 cu.in./rev....so I think my 16/71 should make 632. Now to get the new blower to move the same amount of air my old one did at 15% over....I started out with it 15% under.  Hopefully so far so good.

I started the engine and cyl #1 is VERY rich and # two is a close second (90-120 degrees). The other 6 are rich but OK (220-300 deg). It seems to clear up if I rev it.  I had the hat nozzles big in front and smaller to the rear....I switched them, front to back, and didn't make any difference.
I leaned the barrell valve A LOT and it helped. I checked the port poppet and it was at 15lbs. I changed the MSD 20 ignition box...no change. I ohm the wires and all are good. Leaked to barrell valve to get back to my starting point and the problem is back. I opened up the Shotgun blades from .014 to .019 to make sure they weren't getting sucked closed. Just made the idle higher.

So why are the front cylinders so rich? Do I have the blower spinning too slow at idle?  Maybe does not move as much air as I thought?  Too much fuel and not enough air......but I'm not sure why.
Thanks....

[32bantam]

Tested the idle bypass...Good. Made sure the return hose was clear.
With the more I think about this it seems I just way overestimated the air moved by this blower at idle. When I had the barrel valve way lean for standard blower leak it is way rich.....when I leaned it to get the front cylinders to clear up .....the throttle response was good.

[Frontenginedragsters]

Steve:
 Your engine just needs to get adjusted to Arizona air!!

Matt

[Spud Miller]

 High helix blowers always throw all the fuel to the front at idle. The front two are OUT and the back two are burning up. For extreme cases like yours, I employ ball-check nozzle bodies on the front two hat positions. I set them to about 16 PSI and they are completely OFF at idle and on above that. Works great. In one case, we did the front four like that and the engine idled off the back 4 only. Two of those 4 were in the hat, the other two were in the back of the blower.

 Going down the track, the front two will be leanest generally, so the ports are staggered the other direction.

 Spud

[32bantam]

Thanks...at least now I know what is going on.
I want to clarify....hat nozzles larger in the front?
Can I run the front four hat nozzles off the port block? The ports are set for 15 lbs. If not what do the ball check nozzle bodies look like? Do you sell them?
Thanks again...now I can sleep at night !!!!
Steve

[Spud Miller]

Thanks...at least now I know what is going on.
I want to clarify....hat nozzles larger in the front?
Can I run the front four hat nozzles off the port block? The ports are set for 15 lbs. If not what do the ball check nozzle bodies look like? Do you sell them?
Thanks again...now I can sleep at night !!!!
Steve

Hat nozzles small in the front, port nozzles big in the front.

If you could plumb the front hat nozzles to the port distribution block that would work great. Ball checks are easier. The nozzle bodies look exactly the same from the outside, except for no hole. They'd replace your existing bodies. Tiny shims, spring, ball and ball cup go inside and your nozzle screws into it to hold it all in place. We do stock them.

 Spud

[dreracecar]

If the blower winds everything to the front, why would nozzle placement matter in the hat? wouldnt nozzle size just mean fuel volume and cooling?

[wideopen231]

I use to run dual port nozzles with specail BV just for this reason.One set where on at idle and second set only at full throttle.Worked great.Now my system was setup for 14-71 at 56% od and was high helix with delta hole. Also worked with the whipple just reveresed and flipped the nozzle layout.

[Spud Miller]

I use to run dual port nozzles with specail BV just for this reason.One set where on at idle and second set only at full throttle.Worked great.

Yup, more hardware involved and getting two port nozzle holes per cylinder in some manifolds is almost impossible. But works great! Commonly called "Dribblers".

Spud

[Spud Miller]

If the blower winds everything to the front, why would nozzle placement matter in the hat? wouldnt nozzle size just mean fuel volume and cooling?

Well, of course not EVERYTHING goes clear to the very front. Forward is the trend though. Even with a delta or delta-retro opening, putting more fuel in the back of the hat favors the rear of the triangular exit and makes it to the rear cylinders. Blower setback helps a bunch too.

Spud

[32bantam]

I got the engine to idle a little cleaner with the front four hat nozzle change to the 15lb. port block. But not great. Sooooooooooo I odered a 8 1/2" snout and moved the blower back 3 more inches. I will leave the fuel changes as they are. We will see how much that helps.

[32bantam]

At the March Meet and started the car for the first time with the blower set back another 3" for a total of 5" ....two of the hat nozzles plumbed to the ports....and.... just about PERFECT!!!
Took two safe and slow test sessions (7.61 and 7.43) to get data on the blower. I way over estimated the blower out put. (Estimated the 16/71 HiHelix would put out 632 cu.in./rev....works out to 550) Maybe it will get better at higher ODs.
Statred  out with 15% under driven for 12 lbs of boost...second pass @ 10% under got me 14 lbs. The engine needs 18-20 to go 7.0. So now I know what the blower really wants for OD. I give it 3.6 OD and our first qualifier gets us a 7.002 lifting at 6.43 into the run......
OOOps too much blower and I was lucky with my lift !!!!! But now I REALLY know where I am with the blow.
I put the port nozzles the way you said Spud...big in front and smaller to the back and I only need to make a couple small adjustments.
Thanks for the help !!!!!!!!!!!!!!!
Steve
SS3 Race Team