Air/Fuel Ratio??

[tom1394racing]

On Monday I'll be dyno tuning my RSR Clone.

What should I be targeting for air/fuel ratio??

The engine is:

3.0 1978 SC case
10.5:1 RSR Pistons & Cylinders
Twin Plug heads & Dizzy
DC-60 (GE-60) Cams
46 mm PMO's

[Wil Ferch]

Better informed people will chime-in...but I would say about 12.6 :1 to get good power....letting it drop to 14: 1 or even a bit lower on light load applications. Lastly...don't let it creep up anywhere near 17: 1 under any combo of load/rpm.....

One man's opinion...

- Wil ) just love your car !! .....

[kepperly]

What are you running for induction? Webbers?. If so I would make sure you are starting with the correct ID venturi, which on a 3.0ltr in the state of tune as yours would be around 38mm, in a set of of weber 40 ida-3c carbs. there are sets of venturi tubes avaiable for 46 IDA webers with 38mm ID for even more latitude in tuning.

Keith Epperly 87 slant nose turbo look carrera cabriolet

[tom1394racing]

I am running 46mm PMO's set up as follows:

AV's 4.5
Vens 4.0
Mains 160
Idles 55
Idle Airs 180
Tubes F16
FBCV's 50

[RoninLB]

Originally posted by tom1394racing
I am running 46mm PMO's set up as follows:

AV's 4.5
Vens 4.0
Mains 160
Idles 55
Idle Airs 180
Tubes F16
FBCV's 50

on which engine combo ?

[tom1394racing]

The engine is:

3.0 1978 SC case
10.5:1 RSR Pistons & Cylinders
Twin Plug heads & Dizzy
DC-60 (GE-60) Cams
46 mm PMO's

[RoninLB]

Thx Tom. I find it interesting as I don't have any experience setting up carbs with a package such as your's. I imagine it can be difficult as even a dyno doesn't exactly mimic real world conditions.

otherwise the chart's curve max's at 100%, the top of the graph's border is 105% . The lines under 100% is 95 90 85 and at the very bottom is 80.

[tom1394racing]

Ron

That's a neat chart. Where did it come from??

[RoninLB]

Originally posted by tom1394racing

Ron
That's a neat chart. Where did it come from??

I'm loaded with as much text as possible. Sometimes it hurts as when not connecting that I asked the original poster a question when I thought it wasn't.

Otherwise carbs is carbs. The game is to atomize the fuel mix as much as possible. Just dumping in more fuel doesn't do any good if it can't be atomized.

As Keith was hitting on above it's the velocity and the venturi atmospheric psi drop that allows the expansion of the mix. Itty bitty molecules of mix combusts with more power than the same mix volume combusting as a big drop of liquid. The itty bitty molecules have more surface available than a drop... kinda like you can light a cigarette in a room with a bucket of gas but can't live thru the same volume if it was misted in the room.

btw.. it's a carb eat MFI world imo.

[kepperly]

Thom,
I have set of six 38mm id 46mm od venturi tubes on ebay if you are interested. #8006221713 that id would give you abetter velocity and more effiecient fual atomization than 46mm bores.

Keith Epperly 87 slant nose turbo look carrera cabriolet

[tom1394racing]

Thanks all for the advice.

I'll post results and final tuning specs after the session on Monday.

[tom1394racing]

Here's the link to my dyno results.

Another RSR Clone Project - Dyno Day