Yesterday I started a thread in this section describing how I had cleaned the throttle valve and inlet manifold tract to remove the soot crud that had built up from the EGR gases, I said that it seemed to run a lot better with more go and I hoped there would be a decrease in fuel consumption as it had always been a dissapointment to me.

 

Tonight I did the 2 x 10 mile return trip to the running club, a trip I do 3 times a week always on empty roads & at the same speeds & always getting the same (indicated) fuel consumption of 45 mpg, tonight it was 53.6 mpg a 19% improvement in fuel economy, even compared to the overall figure on the Maxidot of 47 mpg it is a 14% improvement.

 

I will see what the brim to brim MPG figure is on the next few tank fill ups to see what the overall improvement is but am very pleased with a job which was rewarding to do and cost nothing.

Edited 7 September, 20205 yr by J.R.

 

Were it the venturi of the carburettor of a normally aspirated engine then I would not be surprised at the improvement but for a forced induction engine its unexpected.

 

Now I am wondering what the back of the inlet valves look like, I think I might buy a USB endoscope or remove the manifold to see.

Edited 7 September, 20205 yr by J.R.

that's good! was it easy to get to? how long did it take you to get to the relevant part?

You have to work a bit blind but as I am a bit blind I find that quite easy! Doing the job a second time would be easier because you know what is where and what the fastener head sizes are.

 

If you remove the U shaped intake trunk from the air filter to the snorkelling box on the bonnet slam panel it gives much more room.

 

10 minutes to remove the throttle valve approx, disconnect connector, slacken hose clamps, remove bolt holding disptick bracket then 3 bolts holding assembly to manifold (might have been 4)

Not even half way through the first tank of fuel yet so its early days but the overall maxidot consumption figure (reset to zero on fill up) is already up to 51.6 mpg compared to the previous 47 and I have only done one journey longer than 10 miles so it will definitely go higher, my regular 2 x 10 mile return trips to the running club are now returning 57.5 & 58 mpg it was never above 45 mpg before (all maxidot figures so higher than actual brim to brim figure).

 

The short slow journey consumption around town may be slightly increased its hard to tell but that was always reasonable, what was wrong was that it did not improve on longer steady speed journeys, now it has significantly.

 

And other than the first time (which freaked me out) there has been no more engine shuddering on shut down.