AFM or no AFM that is the question...?
Discussion
They are both standard - top photo is an S3C originally equipped with catalysts probably now removed and has lambda sensors in the exhaust manifold, so no AFM. Basically it is the next update that Ford did to the 2.9. So your engine is an earlier version and the 3c has a later version.
And heres another one - spot the sensors in the exhaust
And heres another one - spot the sensors in the exhaust
Edited by chiefyo on Tuesday 3rd September 14:47
It's an S3C.
These sense engine load with a Manifold Absolute Pressure sensor (MAP): a little black box near the centre of the bulkhead, connected by a vacuum tube to the plenum, instead of the AFM's.
They also should have catalytic converters (although many will have had these removed). They have lambda sensors (HEGO's) on the exhaust manifolds (which were required to maintain suitable conditions for the cats), and they use a different ECU which has inputs from the HEGO's and the MAP, and no AFM sensor inputs.
There is a theory that they should also have a slightly different engine with hydraulic valve lifters (the S3's should be solid).
It may be that an engine with hydraulic tappets and cats would theoretically deliver a little less power (due to restricted rev. range and restricted exhaust flow). It may be that exhaust oxygen feedback (ie automatic mixture regulation) might deliver a little more (due to improved combustion efficiency). TVR never published any differing BHP or torque figures for the S3 or S3C.
The cat setup must have been a more expensive option from new, but I suspect TVR's using whatever Ford crate engines they could get their hands on, would have been more important.
From other people's comments, I suspect the major problem of AFM's is their fragility and potential unreliability. The MAP seems a simple and reliable device; its complexity is in the ECU, where it belongs.
Mine's a legal, decatted S3C with a solid-tappet engine, and I think that's probably the best setup. Other opinions welcomed!
These sense engine load with a Manifold Absolute Pressure sensor (MAP): a little black box near the centre of the bulkhead, connected by a vacuum tube to the plenum, instead of the AFM's.
They also should have catalytic converters (although many will have had these removed). They have lambda sensors (HEGO's) on the exhaust manifolds (which were required to maintain suitable conditions for the cats), and they use a different ECU which has inputs from the HEGO's and the MAP, and no AFM sensor inputs.
There is a theory that they should also have a slightly different engine with hydraulic valve lifters (the S3's should be solid).
It may be that an engine with hydraulic tappets and cats would theoretically deliver a little less power (due to restricted rev. range and restricted exhaust flow). It may be that exhaust oxygen feedback (ie automatic mixture regulation) might deliver a little more (due to improved combustion efficiency). TVR never published any differing BHP or torque figures for the S3 or S3C.
The cat setup must have been a more expensive option from new, but I suspect TVR's using whatever Ford crate engines they could get their hands on, would have been more important.
From other people's comments, I suspect the major problem of AFM's is their fragility and potential unreliability. The MAP seems a simple and reliable device; its complexity is in the ECU, where it belongs.
Mine's a legal, decatted S3C with a solid-tappet engine, and I think that's probably the best setup. Other opinions welcomed!
chiefyo said:
Just to say - super job ! Reminded me of my new-from-the-factory S3C circa 1991, they fitted the rocker covers that I had had chromed, and stuck the badge on to the plenum chamber for me but managed to get it t'other way around to yours. (Just in case anyone should say yours isn't original because they didn't fit chromed rocker covers...) 
Gassing Station | S Series | Top of Page | What's New | My Stuff