Glowing exhaust bank and power loss at constant revs..
Discussion
Dropped the Griff off today for a much needed Rolling road session today as it wasn't peforming too well.
All turns out ok fuelling/power wise after tinkering apart from a coil that is on the way out(no worries there, get a new one) but the following rather disturbing behavour was spotted.
When kept at a constant revs, the power stays steady for a while, then gradually drops off by 20 or so bhp. The higher revs, the shorter amount of time that it takes for the power to drop off. When this happens, the nearside exhaust bank glows increadibly hot.
The r.road operator thinks that there may be a blockage somewhere in the exhaust. My first thought is that a precat has disintegrated, so its been booked at the local independant (only 50yards from the rolling road..useful) to have a have a closer look and pull them out anyway!.
Has anyone seen this power loss behaviour before?
All turns out ok fuelling/power wise after tinkering apart from a coil that is on the way out(no worries there, get a new one) but the following rather disturbing behavour was spotted.
When kept at a constant revs, the power stays steady for a while, then gradually drops off by 20 or so bhp. The higher revs, the shorter amount of time that it takes for the power to drop off. When this happens, the nearside exhaust bank glows increadibly hot.
The r.road operator thinks that there may be a blockage somewhere in the exhaust. My first thought is that a precat has disintegrated, so its been booked at the local independant (only 50yards from the rolling road..useful) to have a have a closer look and pull them out anyway!.
Has anyone seen this power loss behaviour before?
Do you feel any roughness when this happens? A misfire would quickly get the exhaust glowing, but I would expect exhaust backpressure to cripple the power output before it affected the exhaust temperature. Maybe different if you're under power on the rollers but the exhaust theory just doesn't seem very likely to me. I would start by looking at the state of the plugs and se if they are all running at the right temperature, also check the header temperatures to see if any cylinder is obviously not pulling its weight. Then check whether you are getting a good strong spark under load, and whether the ignition timing is about right.
It does no harm to check the state of the exhaust if they're started on that, and getting shot of the pre-cats while you're at it gets my vote. You can also stick a pressure tap in the lambda sensor hole for a quick sanity check on backpressure downstream of the pre-cats.
It does no harm to check the state of the exhaust if they're started on that, and getting shot of the pre-cats while you're at it gets my vote. You can also stick a pressure tap in the lambda sensor hole for a quick sanity check on backpressure downstream of the pre-cats.
I aint an expert... but this post from General TVR forum might be of some help....
www.pistonheads.com/gassing/topic.asp?t=239140&f=13&h=0
www.pistonheads.com/gassing/topic.asp?t=239140&f=13&h=0
Thanks folks...such a fast response! Its very smooth/responsive/fast now (wasn't before the tune though). Kicked out 209bhp+220lbsft at the wheels (this may be slightly down though looking at posts). Come to think of it, its pinked before now and has had new plugs in there in a service(not long ago) and has pinked since so maybe an injector and the 2 are related....good food for thought that, thanks!
Pre cats are still history though!
Pre cats are still history though!
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