View single post by NigelK
 Posted: 09-02-2015 11:41 am
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Joined: 07-16-2014
Posts: 164
Dear Forum Users

I’m posting this chart more to catalyse debate than anything else…

It shows engine torque and lambda readings (I managed to extract these from the tuner) from my GT with different airbox setups. Some of you have suggested that the dip in torque at 3500rpm might be a progression issue. The lambda figures show i) a leaner mixture of 0.9-1.0 at cruising revs (2000-3250rpm) providing optimal fuel economy, with a richer mixture of 0.75-0.85 at higher revs to optimise performance, and ii) that the progression from leaner to richer mixture (which starts at just over 2500rpm) does not coincide with the dip in engine torque (which starts at 3100rpm).

Mike Taylor tells me that the lambda figures are consistent with what one would typically expect from an in-tune Excel 912HC engine. They also suggest that carburation is not a significant contributing factor to the dip in engine torque at 3500rpm. Rather, this dip is driven primarily by the tuned exhaust length combined with the intake length. Mike reckons I might be able to smooth out the dip with velocity stacks – there is room for stacks up to 70mm length in the Excel airbox without removing the panel filter.

But, as I do not notice the dip in everyday driving, it’s not something I feel the need to fix any time soon.

Best wishes,