Poor low speed driveability

[boy83]

I have an 83 sc with 120/104 camshafts, tec3, twin plugs, ssi, sport muffler, 98 Mahle p&c 10.2 compression ratio, Magnecore wires, gt3 fuel pump, carrera intake, wide band o2 sensor.
It runs well above 3000 rpm. It surges below that.
Do you think more tuning would smoothen it out below 3000 rpm?

[Steve@Rennsport]

Hi,

If you are using a Carrera intake manifold & throttle setup with 120/104 cams, this combination will never run properly under 3K due to intake reversion.

The solution is either less camshaft or another intake system such as ITB's or carburetors.

[kenikh]

Originally Posted by Steve@Rennsport

Hi,

If you are using a Carrera intake manifold & throttle setup with 120/104 cams, this combination will never run properly under 3K due to intake reversion.

The solution is either less camshaft or another intake system such as ITB's or carburetors.

Reed valves?

[Henry Schmidt]

Steve is absolutely correct. The cam is entirely too aggressive for most EFI systems. Excessive overlap seems to be the culprit. The lobe center on a 120-104 is 100. I would think that any lobe center less than 108 would create intake pulses that would be difficult for your EFI system to overcome.
If your system can substitute idle vacuum with some other data perhaps you can cheat the system. I am not by any stretch of the imagination an EFI expert so with a cam this aggressive you may be fighting an losing battle.