Building, racing, crashing race cars with the 750 Motor Club
It’s been a while since I posted here, for which there’s a complicated reason that won’t fit into this margin.
We’re working up now to the next race at Anglesey. As I write it’s warm and sunny outside; doubtless this presages a race weekend at Anglesey with horizontal rain. Having suffered hugely at Anglesey in the past I’m very wary about the weather there.
Well, it’s back to that in-between races fettling period. In fact, it’s a bit more than that for me because I’m going off to Spa again in a while for a couple of days whizzing around the track. Although that’s a trackday and as such I won’t be able to time myself I’m still planning on using the occasion (apart from the sheer rush from shooting up Eau Rouge) to do a bit of testing. As such I’m planning on trying a few new things.
I knew it was too good to last.
I took the exhaust off again and, lo and behold, the cat is showing signs of incipient degradation. It’s got a way to go yet but you can clearly see that the matrix is coming to bits and there are various clearly hot spots which are just about to block up the exhaust.
To say that I’m hacked off about this is the understatement of the geological era. There must be someone whose legs I could rip off… I had had plans to do all sorts of clever things to the car this weekend. It looks, instead, as if I’ll be welding…
Thankfully the new cover and the proper RTV sealant fixed the oil link. Today I started the engine, having first watched the Chinese Grand Prix, and left it running for quite a while with nary a drop of oil. That’s a relief.
As there’s a race coming up at Brands and it’d be really nice to actually make it onto track this time, I’ve been working towards that.
After having made the bump steer gauge I spent a day setting up the suspension very carefully. In order to do so I did something I’ve been meaning to do for ages and bought some bags of sand to make a fake Tim with in order to set up the car properly. With that in place I set the ride height, corner weights, camber, toe and stringed the car. I must admit that when I next build a car I’ll arrange for a setup frame to be easily fitted to the car which will make a lot of this a lot easier.
I’m still working on the car with an eye to the next race, at Brands, and the upcoming rolling road visit.
I’ve added a small stay to the airbox. At snetterton a scrutineer leaned on the airbox and the throttle bodies came adrift from the rubbers that attach them to the cylinder head. This stay should stop this happening. I am, though, probably going to move the bottom end of so that it attaches to the engine mounting, rather than the top of the pedal box.
I got the exhaust back on this weekend, having had to modify the mounting slightly to account for the slightly repositioned can. You can see the “bright grey” mounting at the back of this photo.
Compared to the recent bout of doom and despondency, this post should turn out to be slightly more upbeat.
First up I took the remains of the shattered exhaust over to Andy’s and we welded in a new cat, as seen here. (I really need to get a TIG welder…) Apparently, the cat I had is one of the earliest batch produced by the company that Andy got them from and they now weld the cat canister into the housing. (If you look hard at the photo you can see where there’s some grinding on the top of the housing, this appears to be the end result of where a hole has been drilled through the housing and then filled with weld material after the cat was inserted.)
I’ve now had a chance to have a look at the cat rather harder. Of course, this involves actually cutting up my nice new Tony Law exhaust system which is a bit alarming. Here it is in the vice just as I set about it with a hacksaw.
You can see the lambda boss sitting here. When I took the lambda sensor out it was completely black, symptomatic, I guess, of the thing running incredibly rich and dumping carbon all over everything.
Well, that explains it then. This is the view peeking down the inlet to the cat. The cat is not meant to look like that jumbled pile of bits and pieces.
I got up this morning having decided that the problem was either a) something to do with engine management or b) a blocked exhaust. As you can see it was the latter. This blockage would have reduced the flow of gas through the engine which effectively is what was causing the rich mixture.