c.a.r. Wrote:There was a "rumour" and I state that it was a rumour as there was nothing to back it up, on the GTi6 forum some years back, that the XU7 alloy head was found to be superior and the inlet ports were deliberately restricted to make the car slot below the XU10 XSi engine rated at 136bhp (if memory serves me). This was either to make the XSi marketable or lower the insurance groups on the 1.8 models (more likely I think).

c.a.r. Wrote:Grant,

You're beginning to get on my tits now.

Facts:
RS manifold fits onto 1.8
Improves throttle response
Causes flat spots

Unknowns:
Gives a definite performance gain / More power
Overfuels / Underfuels

We don't know whether the flat spots experienced are caused by over or under fuelling, running rich or lean. My car definitely used more fuel which would suggest it over-fuelled, but we don't know whether that accounts for the entire rev-range, without seeing an AFR graph print-out - something nobody has been able to obtain yet.

If you're happy with it then that's good, we're happy for you son. But unfortunately time and time again this manifold swap has incurred 'similar' problems for the majority of end users who carry the modification out.

The above two quotes do not 'contradict' one another. If you re-read more carefully I state that the larger TB imrpoves throttle response, for obvious reasons that anyone - engineering background or not - could understand. However after returning to the standard, plastic intake manifold as found on the 1.8 and 2.0 XSi the 'overall' (crucial word) performance was imrpoved. This is probably because the AFRs were matched better with the parameters which the ECU values are programmed to, so better power and torque could be felt by nothing more than your very own "bum dyno" from the driving seat. Economy improved also, but it was still dire because the aerodynamic characteristics of the cabriolet model are somewhat crap in comparison to a hatch.

Being overly critical isn't the same as having a discussion. I'm keen to know how you have made your conversion work, as you seemingly haven't used any different components to the rest of us. It could be that your ECU is a different model perhaps (I thought the Sagem unit was standard), or that a sensor reading is out. Of course it could be what I suggested earlier in that you might not have noticed where these flat spots lie as yet, depending on how much you use the car.

I'm no engineer and don't pretend to be - I learn by reading and experience. I don't claim to have a superior understanding of the ins-and-outs, but I do have a pretty extensive experience with XU7s in different states of modification and I'll chime in where I can.

(08-07-2012, 06:17 PM)Niall Wrote: The gti6 heater matrix hoses will fit with a bit chopped off the ends. I had them on mine perfectly.