WTB, What to avoid , best VFM?

Thanks also has anyone had a set of OEM one ported by Harvey and what was the difference?

 

megan racing unequal length headers

 

had my headers ported (harvey) when i was running on a standard ECU, found the car spooled better and had better off and on boost performance than before, porting headers was the only change i had made at the time.


great VFM in my opinion

 

Agreed on porting.

If you want to go further a good set of headers will allow scope for bigger power. Careful of the unequal length ones as many dont like the lack of scoob rumble. I have HKS ones which still retain a fair bit of the original noise.

Watching it being mapped with these on made me glad I have them

MB

 

Did you mean equal length ones? I have OBX E/L manifolds, and they are very good - lose a bit of the rumble - but gain a bit of a scream!

 

Sorry, yes - meant equal ones

There's also a theory that unequal ones create a smoother gas flow, as the 2 are pulsing at different rates, (with piston cycle) rather than in tandem (aqual length) which would create more of a bottleneck as all the flow comes at the same time.

MB

 

Sounds like that's backwards. The point of equal length headers is that the exhaust pulse from each cylinder has the same distance to go, so the travel down the exhaust spaced out evenly. The cylinders don't all fire at the same time, so the exhaust pulses won't all try to come out at once.

With unequal length headers the pulses take different amounts of time to get down into the main part of the pipe, since the RH cylinders have a far shorter path than the LHS ones. As a result of that, although the cylinders are firing evenly spaced, by the time the pulses of gas hit the main section of the pipe you get 2 very close together then a gap then 2 very close together, and that is what makes up a large part of the Scooby noise.

So with Un-equal you are getting "Pop pop......pop pop.....pop pop....." whereas with equal you are getting "pop..pop..pop..pop..pop..pop.."

The reasoning you gave is the reason that they switched away from un-equal to equal for the Spec-C and others.

 

porting by Harvey = top value mod.
as for next step up, I went for GT spec genII's on group buy, they look very trick

 

also of the aftermarkets, Is there a difference between MY's as I thought that all EJ20's were the same as far as headers went?

 

I see what you mean but I was talking with Bob about it the other day and it made sense then!

MB

 

Given the off beat burble if would suggest that the gas flow through the headers is equally spaced between the left and right hand cylinder bank, which if correct would imply that the flw through the headers doesn't all come in one go.

MB