Dynoing a pair of customer built 548s with Whipple 3.3 4500 carb single flange style blowers (flange is on TOP of blower) with Holley Sniper throttle bodys.
I have dynoed 2.3 and 3.3 Whipple top mounts in past, with standard innercooler /rear mounted throttle body tuning with Mefi I was able to get the AFRS between 10.5 on richest cylinders and 11.9/12.0 on leanest cylinders. In this current scenario were essentially at 10.5 flat on # 1,2 cylinders which really means were BELOW 10.5, its just where my o2s quit working and about 13.0 on #8 with3,4,5,6,7 all where Id like them between 10.8 and 12.0.
Yes, #8 is actually lean and plug shows it, I can guarantee it would melt the piston if left at this AFR
yes, the blowers turned up as fast as we can run it with this combo vs customers stock block/ power goals (7.5 lbs boost /880 ft lbs tq/820 hp)
turning it from a 4.0 upper to 3.625 upper drove #6 that was 12.4/12.5 down into 11.8, it barely moved #8 though about 1/10 of a afr point still close to 13.0.
So its no mystery when you look at this particular 3.3 and you see how it literally shoots 2/3rds of its fuel/air directly on top of innercooler on top of #1/#2 intake ports why they would be pig rich. So far we built diverter plates to try to direct the fuel/air away from 1 and 2, started small and went bigger and bigger. Yep, it changed the AFRS but NOT for the better, just made others like 5,6 also go into the mid 12s and 1,2 go richer yet. So we learned air will turn from a directional plate, fuel will NOT, it just pulls it out of suspension.
Next thing I tried was disassembling one of the new superchargers, tapering/grinding down the abrupt partition /bulkhead under the main case, I would THINK the fuel/air isnt so much turning and going uphill and hitting it but who knows. That richened it about 2/10 of a point.
Tried adding a phenolic 1" 4 hole spacer between TB and blower top, in hopes maybe it will break fuel up/let it open pattern up from the injectors, who knows. It picked up 10 ftlbs/10 hp observed but did ZERO to AFR delta.
Took the 1" innercooler spacer off engine 2 and stacked it on engine 1 on the dyno with thought it would let the air/fuel disburse better, did zero to change AFR spread and had ZERO affect on hp.
Now engines off the dyno, doing other customers dyno jobs to get caught up while we regroup. Whipple tells customer yes there is known distribution issues with this intake and the 4500 single carb flange version 3.3 is the worst and they suggest tearing blower, innercooler, lower intake off the motor and machining the hump in lower intake down 1/2" with a mill which is my next step. I also special ordered a couple 1.6 ratio rockers to try on #8 intake valve, maybe by lifting valve .050 less it will richen up. Gonna attach pics from my phone IF I can figure out how to log on here, Smitty







This was one of the pulls with one of the various diverters we built and tried

So, besides driving down tailpipe AFRS with a bunch of fuel which I have done already, or speeding up blower significantly (already past customers power goal/near safe durable limit of stock gen 6 block IMO keeping in mind going from 4.0 upper to 3.625 upper only richened #8 1/10 of a point, has anyone else done ANYTHING else with same blower to address distribution issues? Driving tailpipe AFR down to about 11.0 average DID bring #8 close to 12.0, it also drove cyl 3/4 into the 10.5 f;at afr reading along with 1,2 and decayed overall power. Again, whipple said machining lower intake floor down 1/2" will "help distribution" but did NOT say how much it will help. And THAT makes me wonder IF this is a known issue, why would they NOT go ahead and machine it from factory when they machined the rest. I encouraged customer to NOT buy these for very reason of what we currently have going on and to buy the rear TB mount version instead. Again, looking at past dyno data the rear TB version does have same rich/lean cylinders, its just not as bad. My guess is the fuel gets churned up better because it goes thru the rotors further, Smitty

One of the pulls

I like the out of the box thinking on trying to solve this.
Those low profile Whipple intake with short runners aren`t great for fuel distribution.
Isnt a 3.3l a little small for a 548ci?

Smitty,

I'm generally good for one good useless idea a day....

Ditch the carb for a TB, and install injectors below the blower, across the length of the plenum chamber.

Thanks. Brad.

Please read thats a EFI TB......

F2,

I did miss that, but it's all the same. The fuel is being introduced at the TB, and not making it to the cylinders evenly.

I was, for the most part, just messing with Smitty. But I do prefer direct injection to carb/TB injection, any day.

Thanks. Brad.

Whipple has a port injected intake with the intercooler built in. Im sure u can get the top plate. Switch the computer to a holley computer and drive the xtra 8 injectors to trim it in. Its obviously more money but u have to put fuel threw a whipple i think minimum 40 % regardless and fine tune the trim with the port injected manifold injectors. Its a sweet setup

Do you have any pics of the intercooler inlet and outlet?

The first pic you can see the intercooler fittings I think they are a -12 ? with an O ring where they seat in the base