Fuel Nozzles in Rear of Blower

While walking through the pits at the Snowbirds in Bradenton last weekend, I noticed that almost all of the blown cars had nozzles mounted in the rear top of the blower case behind the hat. I saw as many as 6 nozzles back there. All of these blowers were 1471 or larger.
These same cars usually--but not always--did not have any nozzles in the rearmost part of the hat itself. It did not seem to matter if it was a Hemi, 481x, or Chevy.
We were the only ones who did not have these nozzles and I was wondering if I was missing something, or is this just a case of "We do it 'cause they do it, and they are fast".
I have been reducing the amount of fuel in the back of the blower to get the idle temps balanced out, which shows up on the EGT's, but not on the ET slip.
Is this just a high boost thing? Just for blower lubrication? Or.....

Kendrick

 

We do it to even the fuel out and wet the rotors evenly. Run as much fuel in the hat and top of the blower as you can, seals it up and lowers the boost temp. By the time the air and fuel come out of a retro-high helix its all at the front anyway, so more fuel at the rear lubes and seals better.

 

I am sorry I missed you. Which car was Adams? There were a lot of extremely cool PM's there with Manzo and Newberry helping a few. I only talked to a few people outside of the Open Outlaw class that we were in, they all seemed quite busy, and some were very intense, possibly due to the level of competition.
Unfortunately, I do not have a delta discharge blower. It is the one BDS refers to as an "air-lock" which is a conventional (read: not hi-helix) 1471 with strips and is open on the bottom, a regrettable choice in hindsight, but there you go.

Back to the nozzles.
It sounds like I should add them back there in spite of my choice of superchargers and just deal with the huge variation in idle temps, or are there other options?

 

Prtobably won't work on all manifolds, but we put one nozzle thru the back wall of the manifold.
The spray tip was pointed straight down at the manifold floor.
Hooked it to the distribution block that ran to the hat & blower nozzles.
Some of that nozzles fuel goes into #7 and some into #8.
Had to lean the port nozzles on those 2 cyls slightly to get them back to where they were during the run, and it sure helped equalize the idle temps on 7 & 8.
Thanks,
KG

 

We had a blower with nozzles in the rear. So we did "lube" it that way too.
So I agree with all that.
Like several said, forcing it all out the delta hole is what makes the rear (idle) lean.

Lots of ways to get around that, moving the blower back, adding "dribblers", etc.

It was a very small nozzle we put in the back wall of the manifold (34).
This was quick and easy. Other cyls idled at 450*, 7 & 8 were about 850*. This change brought them right around, and only took one pass to get the back 2 port nozzles dialed back in.

On the Indy (Chevy) manifold, the front 1/2 of the floor is lower, and the front cyls have "dams" so the fuel already pools in the front. The rear is raised (highest point of floor) so the fuel can't puddle back there. Just how they made it.

Leaving off a launch control, the engine seemed to respond better coming off dead idle (approx 1800 rpm) to the launch setting (approx 3600 rpm) when the idle temps were closer.

After opening the throttle, that nozzle really becomes just another port nozzle.
I would guess it would atomize as well as the other port nozzles do.

I would agree that if we brought the rpm's up and then staged, there is a better way of doing it. But staging at dead idle and then matting it when the last guy rolls in (especially on a "quick" tree) we wanted/needed it to come up as clean as possible. To us, clean meant having the idle temps within 100-150 degrees.

I agree we may have been worrying about nothing.
It certainly never hurt itself when the idle temps were spread out.

Thanks,
KG
www.blackreignracing.com