Lesworth

If it wasn't for the Silverstone Classic, I would be going to this. It makes a refreshing change in my opinion!

Just voicing my opinion.

Ran a last test today with a start from cold. It now fires and idles strongly at 1200 rpm and slowly lowers to 950ish as it warms. Sorted! In fact it runs better than the 911 now. This car has taught me a ton about CIS. Now to start planning the next phase - paintwork.

Golf GTI?

Today I thought I would tackle the last remaining 'bodge' that was introduced to get the right level of performance / running / warm idle. This was the removal and plugging of the vacuum signal to distributor timing retard vacuum device. With this reconnected, cold start was fine but the revs were lower (800 rpm or so) but nothing like they were before removing the main air bypass blockage mentioned above. It felt a little sluggish off boost and not as harp as before. There was also a noticeable increase in popping on deceleration. A little timing tweak (slightly more advance) resolved this and it now drives smoothly, with the right level or performance and reduced popping. I now have all the right things connected and working properly, with the exception of the isolated decel valve. They're not cheap! I would like to re-instate this function but not at the price the new ones are going for (500 EUR on Rosepassion). I suspect a second hand one will be a risk if I can find one. I'll just keep my eyes open and just use the car as is for now.

Is there any noticeable change in idle speed when you put your finger over the hole?

No, of course it won't!

Its a solid no from me, until they show as much appreciation for 74 onwards.

Time for an update. While looking at the hot start issue I discovered that I should have a one way 'check' valve after the main fuel pump which was missing. I fitted one and also changed the fuel accumulator at the same time, along with replacement fuel lines. This resolved that problem. So now its just down to hot versus cold idle which is what I have been trying to get right all along. The guy at Rallytec got the warm idle bang on right by blocking the air passage from the boost tube to the three throttle body bypass routes: AAV, Decel Valve and Brake Booster venturi device. He also removed vacuum to the distributor retard vaccum device. As well as stabilising the warm idle, it allowed idle speed adjustment at the idle screw and also significantly improved performance and drivability. The issue is that while cold starts are fine, the idle when cold is awful, hunting and almost stalling until the WUR leans out the mixture as the car warms. I am really not happy living with this compromise. The Rallytec guy did a lot of smoke testing and found there are no external air leaks so there must be air passing through one of the three bypass routes listed above based on blocking the air passage and the effect that had. Simple logic? Blocking just the route to the booster venturi had no affect. That makes sense because its designed to allow air to pass the ensure you get booster vacuum even when on full throttle / boost when there is no vacuum for the booster. The mixture spec must already account for that air to pass. There is also a restrictor (pinhole size) so its only a tiny amount of air anyway. Next I connected the AAV directly to the air outlet on the boost tube and used some rubber bungs to plug the other open outlets so that only the AAV had air from the boost tube and the other two bypass routes were blocked. On a cold start I immediately had about 1300 rpm and this slowly lowered as the car warmed. Hmm, think I am onto something here. The problem is the idle wasn't stable with a lot of misfires. That could be because the bungs I used weren't totally sealing the other open pipes/ hoses. I connected everything up again and re-instated the block and drove the car to make sure the misfires had gone and they had so I put that down to the bungs. Next test was to isolate the remaining bypass device, the decel valve. This has an inlet and outlet for air and in its default state its closed. It also has a signal vaccum hose to the manifold. During vacuum peaks, such as when you release and close the throttle, it pulls open a diaphragm to allow that air passed. This is to avoid a low of unburnt fuel causing backfires and also allows the revs to drop more slowly, improving drivability, for example between gear changes. Its been isolated for a while along with the AAV and booster venturi of course and you do notice its absence a little. there is a little pop between gear changes as you accelerate but it really is barely noticable. I replaced one of the rubber elbow hoses that feeds air from the boost tube with a pair of silicone bungs and remove the blockage at the boost tube so I now have air to the AAV and booster venturi. Cold start; boom! 1300 rpm, stable with no misfires. Reduces nicely as the car warm to that stable warm idle. I also now have an adjustable idle for the first time. I now just need to drive it for a while to make sure its not just a fluke. I'll be taking it to the Silverstone Classic and it'll be parked on the 924 owners club stand all three days if anyone wants a closer look at it.

Is that leak before the air is metered though? If that hole is before the metering plate then I don't think it would affect the air fuel mixture? In my 924 T the hole for the mixture screw is after the metering plate (it works upside down compared to the 911 I think) so I have a bolt and sealing washer in it. If I unscrew the bolt to access the mixture screw with the engine running it affects the idle speed. What happens with yours when the engine is running and you put your finger over the hole? If it doesn't have any affect then I wouldn't worry. My SC doesn't have a plug either. I suspect its more to do with keeping dust out than anything else?

I suspect that the 'good mechanical run through' amounted to a lot more on top of service and clutch. Maybe brakes, suspension, bushes etc etc?

Have you still got both kidneys?

That 'light' have been a heavy weight in nineteen seventy whatever, but today that's relatively light considering its not stripped out to the extent that an Elise is. Most modern buyers of these wont even know who Colin Chapman was is my guess. Geely want to sell these so they have to appeal to more buyers that the Lotus beardies or track day hacks.

1400 kilos, modern interior and no wide sills to clamber over. 3.5 V6 an manual or auto or AMG sourced 2.0 four pot turbo (from the A45) with a DCT. Load of videos on YouTube from the various respected car channels (Carfection, Harry's Garage etc).