two pronged heads

[Gandi699]

was it/is it nonsense about the heads better better?

[Gabbastard]

Someone tested a pair of them against each other and apparently thdy flowed about 7-8% better. Not much, but it appears true.

[Chipwizards]

I tend to see slightly less power on the later heads, regardless of ECU version fitted.
I suspect that the passages for the cat heating air pump disrupt resonant waves a bit, or possibly harms flow on the exhaust side. Typically 3-5 bhp less is shown on the same spec engine with the later (low emission spec) head.

[axsaxoman]

never seen any difference which head --once you start tuning +use a stand alone --suspect it was just a better map in later ecu.

[Chipwizards]

I've mapped cars with both ECU versions on both engine versions John and the later engine usually tends to show a few hp less than the early one of similar spec otherwise.

I haven't actually done a back-to-back between the heads on the same engine in the same car so can't say 100% for certain but as a general rule the early heads seem to average around 155 with 708s, decent exhaust and induction and the later ones around 150, and of course I optimise the fueling and timing on the dyno in every case so I'm sure it's not an ECU difference causing the difference.

[axsaxoman]

I've mapped cars with both ECU versions on both engine versions John and the later engine usually tends to show a few hp less than the early one of similar spec otherwise.

I haven't actually done a back-to-back between the heads on the same engine in the same car so can't say 100% for certain but as a general rule the early heads seem to average around 155 with 708s, decent exhaust and induction and the later ones around 150, and of course I optimise the fueling and timing on the dyno in every case so I'm sure it's not an ECU difference causing the difference.

I am assuming the airpump type head has the unit disconected and blanked off the hole in head--but hey you could be right --when I,ve done it usually alot of head work as well +maybe bigger valves etc

[Liam_]

I was under the impression the fabled two prong head is the one with the two prongs on the front but without the fresh air pump exhaust hole on the right hand side - so early MK2 before 3 plug ECU.

Not convinced it makes much difference at all myself.