Looking to build a big block with an 8-71 and efi. I know they say spraying the fuel in up top where the carbs would be is good for cooling the intake charge when building boost. However we were thinking of going port EFI because this car will be driven on the street a lot, and the design of most 440 blower intakes doesn't look like it lends itself for peak response with a throttle body type injection. Might end up going that route yet, just want to research my options first.

Now my question is, does an 8-71 discharge air evenly out the bottom? Or is it more to one side or the other? Just wondering if I'm going to have cylinder to cylinder a/f distribution problems if this is done in a port EFI configuration. Any thoughts or ideas?

The Kuhl 8/71 blower I have has a triangle shaped opening at the bottom-rear of the blower.

But with port EFI, can't you just adjust every cylinder seperatly with sequential injection?

I have asked Rich at FASTMANefi a few times, and he splits the system and puts injectors above and below. He says he wouldn't do it any other way. The uppers seem to be to keep the blower cool, and the lower port injectors keep the engine happy and in its correct A/F.. The older blower intakes do not lend themselves well to this, so the Indy intake is one of the few choices you have....

http://www.fastmanefi.com/images/Supercharged%20EFI%20Hemi.wmv

The blowers that I have run all pushed more air to the front of the manifold.To give you an idea on my old set up 6-71 std rotors,indy manifold,1 to1 drive on indy -13 heads the front jets were some where near 68's and the rear was 29's.The fronts were still warm and the rears cold. A little tip to help this problem is to turn the manifold backwards. It dose work with very little mods and you gain 3 5/8 setback. After that the rear started to show heat. That was only with hat nozzles (class rules)

maybe the older rectangle opening is what you want if you worry about the air being equal to all cylinders but i did not notice it that much with the delta opening on the blowershop blower but it was there forsure.

I'll try sending a message to rich and ask him about what he does.

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But with port EFI, can't you just adjust every cylinder seperatly with sequential injection?

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Yes, in theory. However I wasn't planning on having the capability of individual cylinder datalogging.

I would figure that with the injectors below the blower, the engine would be a lot more responsive and efficient during normal driving. But I've seen so many with injectors above. Do the rotors need the fuel to lube or seal them? I was planning on adding an alcohol/water injection system above the blower to provide cooling and chemical intercooling when in boost. My thoughts were this coupled with the injectors at the intake runners would be ideal.

If after that it was just an issue of the front of rear getting more air, to dial 4 injectors up or down a bit isn't a huge issue. But I won't have the capability to getting each one dialed in to the ragged edge. But I think checking the plugs and the header tubes with the laser temp gun should get me there if I edge up slowly.

if you are going to run a non stripped blower i would say put all the injection in the ports would be ok.i injected up to 1300mL/Min and even tried it at idle i am going to put my snow kit back on even with an intercooler.

Look at it this way. As the motor and blower spin they create heat. The engine has oil and water in it to cool the parts. The fuel also lubes the the parts it passes thru. If you have no fuel going thru the top of the blower it has nothing to lube or cool it. Not that it can't be done but I think the clearances in side the blower would have to be very loose to acount for the heat change and no fuel to lube and cool the rotors. Is there a reason why you don't want to run injectors above the blower. If I remember right enderle told me that buy having port and hat nozzles you will gain 40% more tq.

How about using both, I did on the first blown EFI motor I built, 35 lb per hour on top and 55 lb per hour on the bottom. That was a long time ago and we ended up removing the lower ones and switch to bigger 85 lb injectors on the top. That was 499 inch all aluminum KB street hemi block with Dart cast heads, 10:71 with a Bug or Bird catcher(3 hole ,3000 CFM at WOT), can't remember which Due to mismatch parts from BDS that turned into turd soup It ended up with a Littlefield 10:71 and Motech EFI, that worked good Good luck

Thanks cab, I may go that route yet. I have been considering it as well. It may be a decent compromise between the two different schools of thought.

I think to keep life simple I'd go with carbs. for a street strip outfit. You're not far away. PM me if you want to check out my 8-71 setup. We'll take er for a spin.
Kevin

Rich did the EFI setup for my car. Has injectors both above and below. When I was originally going to do this he said if I was only going to do one of the other I think he said that it should be the ones above; but definitely recommended both. So I bit the bullet and bought a new intake, from Indy (not the Mod-man one) with the injector ports done with fuel rails. Motor was dynoed and put in the car but I have yet to drive it.

Its a 500 cu in wedge motor. Nothing spectacular Indy SR heads, 8-71 Kuhl blower, slightly underdriven (dont remember how many PSI its generating)

It dynoed right at 800 hp @ 6,400RPM, with a touch over 700 ft lb in real early.

Has a lot more in it. The injectors were too small to go much more, but its plenty for me as is.

Vince, did you ever get that camcard for your engine yet?
Just curious.

Yup. Had to dig for it.

275/282 duration at .020
.560/.555 gross lift
114 separation

Here is the Indy intake. Very nice beefy piece. Though dealing with Indy was.............

EFI when using a Roots supercharger

Back when I owned Mopar Engines West we spent some serious time testing various configuration of EFI and Roots blowers. Here are some comments from our testing:

* Throttle Body:
Many people liked the look of the Enderle or BDS “bug catcher”. But these flow so much air that it’s hard to get a stable idle RPM because of butterfly sealing and inconsistent idle return. Also, the tip-in just off idle can be hard to control because the increase in airflow is dramatic with a very small change in throttle. For a street driven car at least one port should be totally blocked off.

*IAC:
Provisions should be made for a remote IAC. This can be plumbed into the back of the injector plate.

* Injectors above or below the blower:
Answer -> both. The injectors above the blower keep the blower happy and the injectors at the ports allow for better idle control and off idle tip-in. Also, running sequential injection allows for individual cylinder control which is much more important in a blown engine (see testing).

Testing:
1) We ran several tests with Roots blowers with fuel delivery only above the blower, and found that the rotation of the rotors can bias the charge causing inconsistent cylinder charge at low and mid RPMs. Also we found an airflow bias toward the front of the engine. When injecting only above the blower there’s nothing you can do about that.

2) For all-out drag engines injector location didn’t matter all that much, but in a street engine control of the low RPM torque is critical to good drivability. I have driven cars where injection was only above the blower (not by me) and the customer was very happy with the set up. However, when analyzing the exhaust with a wideband O2 verified that these engines were set up VERY rich. Far to rich, in my opinion, for a reliable street engine. Plugs were black and cylinder wash was prevalent. You can live with this in a short duration drag engine, but not on a long-term reliable street engine.

BTW: We have used street blowers with no seals, so minimal cooling requirements, and injected only below the blower with great success. Of course a blower like this doesn't create much boost but it still "looks good".