19 replies to this topic

[KernowCooper]

yes simply reconnect it and let us know how it feels.

[Jedi Master]

Ok, so I did a 3 hour run this morning: M6, M40, M25 onwards. Reconnected the vacuum hose before starting the engine. Normally, I need full choke and its lumpy and chugging until he warms up. Old Blyty kicked into life with half choke, and I was able to kill the choke shortly after start-up without him stalling. I did a short 15 mins of B-roads before getting on the motorway and the improvement in throttle response and engine pick-up was instantly noticeable. Since having the Stage 1 kit and various other upgrades done, I've always thought that the throttle was a bit 'thick', and when slowing down and speeding up you needed to give quite a lot of movement in the throttle to get a decent change. Now the response is instant, and seems like less effort. The 'feel' is totally different, as though the engine 'wants' to run up to speed rather than walk. When cruising at speed on the motorway, I've had to learn how to control the speed to keep things constant. The induction roar and air-sucking noise from behind the speedo has always been a good indicator, but I noticed that I was over-throttling, but without seeing any acceleration. I've been regularly testing this theory by coming off throttle, which reduced the air-suck and induction note, but didn't see me lose any speed. This clearly demonstrating that I was using more fuel that I needed to. Now, the throttle seems 'right'. There is a very small margin between off/on throttle and when balancing the throttle to get a steady speed, the engine sounds and feels normal. Slightly come off the throttle, and speed decreases. Slightly on throttle and speed begins to increase. I don't think I have more power or faster accellaration, but the drive it better. And, I'm definitely using less fuel, probably because of the way the throttle is now responding and the way my right foot has adapted to it. Idle is very slightly up compared to before, but I did suffer the odd stall here and there previously when coming off agressive throttling.

Somy conclusion is this; the vacuum hose should be in place! I'm guessing that Minisports RR tuning approach is all focused towards power, which doesn't need the function provided by the vacuum hose. That's OK for a track/race car, but for the road it seems pointless.

Happy for comments/feedback!

[mister bridger]

I assume when you had the vacuum tube disconnected you blanked off the spigot at the carb end? If not it will have been sucking in loads of air and running very lean

Edited by mister bridger, 03 January 2015 - 04:14 PM.

[KernowCooper]

With the vacuum connected what your experiencing is a increase in torque, thats why its driving better.

 

I'd not be using a RR where the operator sets up a engine and advises to run without vacuum advance on a road car. There are experts who have spent thousands of hours on dynos and road who all advise that vacuum advance is required on a road going engine, for all the reasons you have listed in your experience from the test.

[Jedi Master]

I assume when you had the vacuum tube disconnected you blanked off the spigot at the carb end? If not it will have been sucking in loads of air and running very lean

Yeah, it was blanked off!