3.2l Track Engine w/46IDAs running rich...

len911 · 04-15-2007, 05:59 AM

I have a track car with a 3.2l engine using 46IDAs that seems to be running rich. The original carb setup was done with my Supertrapps with no disks. Since the original setup, I have installed the disks back on the Supertraps. I believe the additional back pressure is causing the engine to go rich.

Engine is a twin plugged 3.2l, ported & polished, using Pauter rods, Ti retainers, 964 pump, Cosworth 11:1 pistons and an Elgin cam similar to a GE80.

Engine comes into its own from 5500 up and could probably spin to 8K easily, but I never go over 7.2k. There is really no flat spots, but exhaust looks/smells rich. Car pulls nice but there is a lag (bog down?) at about 3k to 5K that could be caused by the cams or perhaps due to carb richness.

Carbs are currently using 60 idle jets, 160 mains and 165 air correction.

I'm trying to lean it a bit, should I go with 155 or 150 mains? Should I change the idle jets?

I searched and I could not find any info on setting up large carbs on engines bigger that 3.0l.

Thanks! Lou

Henry Schmidt · Henry Schmidt's Garage

60 idle
200 air correction
200 main jets
F3 or F5 emulsion tubes
40 or 42 venturi

I know it sounds strange but we have had exceptional response to this configuration on large race engines.

Good luck

len911 · 04-15-2007, 06:23 AM

Thanks Henry!! Regards, Lou

bob barnes · 04-16-2007, 10:05 AM

Len,

I am curious. I have a 3.0L Race engine with 95MM Cosworth Pistons, 46IDA, and Elgin cams making 290HP with Phase Nine mufflers. My Woods built 2.9L with Elgin's GE-80 eq. and 46IDA made 283HP. What HP are you achieving on the Engine or Chassis Dyno? Your numbers and Henry's are way off! Running 40MM and changing to 42MM venturii or vice-versal will make a major change in tuning and jet selection. I have ran the 46IDA on every race engine I had from Ginther, Yates, Andial, and Woods.(1974-2006). The 3.2L needs the PMO carb but 46IDA will work with some lost of power. If you are making more power than my motors, I will leave it up to your and Henry's numbers.

My Opinion,

Bob

Turbo_pro · 04-16-2007, 10:37 AM

Hi Bob
You state that their numbers are way off but don't offer any alternative. I'm certain it was just an oversight.
I'm sure we would all like to hear your alternative jetting numbers.

Steve@Rennsport · 02:24 PM

Hi Len:

Exhaust systems make a big big difference in jetting, torque & HP. These engines are VERY sensitive to header diameter, length, and secondary lengths.

What do you have for headers? Did you simply bolt the Supertrapps to the collectors?

IMHO, Supertrapps do not work anywhere near as well as a proper race muffler system incorporating a crossover (dual-inlet mufflers do qualify) and individual mufflers on carbureted engines result in AFR curves that are far from being linear. If you retain the Supertrapps (with sufficient discs to make power, I would strongly suggest a crossover tube.

I would need to know your current venturi size to offer any jetting suggestions.

bob barnes · 04-16-2007, 11:01 AM

Jim,

There are no numbers until we know what size venturii, Emulsion tube, Cams, etc. That is why I asked for HP numbers. If someone is making more power-my numbers are not important. The engine needs to be dynoed-chassis-or engine dyno and then we compare. To get the numbers I have on my race engines, $5000 worth of Dyno time was expended at $1500/engine session. The last chassis dyno at 911Design,, close to you, cost me $600. Every tuner wants to start with a different starting point with jets and Venturii size. Woods has been the best I've worked with. Dyno the engine so we can compare info.

Bob

len911 · 04-16-2007, 01:08 PM

Gents, engine was dynoed at 260HP (@6.6K) & 194 Ft/# using a Dynapack dyno. I was not happy with the timing as was set on the car at the time. It was so far advanced that it would ping under load as soon as I got on the power. I have since adjusted timing to 26 deg @ 6k and I'm very happy.

Running 1 5/8 headers. Unfortunately, I do not know the venturi or emulsion tube size.

The engine pulls very strong from about 5.5k onwards (to at least 7.5k) and it is probably due to cam selection. I'm sure that it is probably making more HP now that at the time that it was dynoed since the runs were halted at 6.6K.

I'm not complaining or not happy about the way it runs, but since it was set up with open Supertrapps, I'm just trying to optimize mixture to compensate for the addition of the disks.

I'm leaning towards going with 155s instead of the 160s. Easy enough and relatively inexpensive to do. I was just looking from some direction from the experts since I do not want to muck with it too much.

I figured that if the 155s don't work, I can always go back to the 160s and live with it...

I probably would like to eventually go with a 2-in 2-out exhaust. At that time, I most likely take the carbs apart to get all pertinent info since it will be a brand new ball game...

Thanks for all your replies... Lou

My exhaust system...

bob barnes · 04-17-2007, 07:47 AM

Len,

The Venturii size is important to know if you want us to be able to give you any data. The air correction jet will be smaller with a larger venturii-likewise it will require a larger one with smaller venturii. Steve mentioned the importance of the exhaust! The headers could use a size larger for the Elgin Cams you are running. I'm assuming you are running Elgin's315/300 -100lc.
Maximum Torque is around 6000RPM so I would change the Mufflers to Phase-Nines available from Smart Racing or run Open megaphones. Single ignition or Twin-plug?

Bob