Her Majesty's DBS Restoration Update: Engine Dyno Day
Gebruder Gumbold
San FranciscoPosts: 549MI6 Agent
Dear AJB Friends,
A long awaited and much anticipated engine dynomometer run day resulted in a win for Her Majesty's DBS!
All the years of waiting, setbacks, problems, bad parts, etc are over and I am pleased to present a very happy engine, and a most powerful one to boot.
The business end of the dyno: The special flywheel is bolted onto the balanced Aston Martin flywheel, and the engine will drive the dynomometer. A huge outdoor water tank takes the energy from the dyno- it has to go somewhere!
We rigged up a temporary exhaust from an old race car. The standard DBS exhaust will be slightly more restrictive, but will only cost 1-2 HP. Same with the air cleaner and air box.
The projectionist's booth. Absent in the photo is the apple strudel from and Italian bakery...
Time for a run: First session was break in at 2800RPM, with varying load, simulating a climb up a gentle hill. This seats the rings and gets everyone acquainted inside the engine. I noticed that after a period of time that the oil pressure, although good in quantity, varied slightly at first, but settled in to a dead on value. That is when I could tell, even by the sound, that she was happy, and broken in. Couple of changes made at break in: We changed some jets to go richer on idle and on the main circuit. Weber 45DCOE carburettors have very easy to change jets- all you need is a screwdriver and a box of jets. Changed to 150 Main from 145 factory, and 200 Air Corrector from factory 125. This is chiefly because of California sea level and air density, and that Her Majesty's engine is of a 4,7 litre capacity, increased from the factory 4 litre.
Those 2 washing machine hoses are the crankcase breathers, which go to a catch tank in this case, but route into the air box when the car is on the road. Before break in, we were concerned about blow by oil and vapour, but the rings seated rather quickly, and the catch tank was empty. A VERY good sign. I attached the air box and air cleaner for the power runs, to accurately simulate the real world power. The factory and most dyno figures are with no air cleaner, which will restrict air flow, and,consequently, power. Turned out to be a minimal loss.
...And away we go!
Factory Vantage Spec: HP: 325 (est) @5750RPM Torque: 290@4500RPM
Her Majesty's DBS: HP: 350 (est) @5850RPM Torque: 348@3800RPM
We were extremely conservative in our RPM rev limit. The huge, and telling firgure that pops out is the torque- that is what moves the car. A whopping 348 is up there with the DBSV8! The torque comes in far earlier as well. That longer stroke 12 counterweight special crankshaft paid off! This will be a nice, mid range revving, low RPM torque engine, which is exactly what a DBS gentleman's Grand Touring car should have. Let the Ferraris buzz up to 8000RPM and last half the miles, I'm happy with a powerful and smooth engine, even with 3 Weber carburettors. Quite chuffed at the results, and as soon as I can go and collect her when she is removed from the dyno, I shall endeavour to install all the needed parts, and pop her into the eager engine bay....
Thank you to everyone for your kind words and support. Back in the workshop tomorrow to finish installing the offside SS sill covers and B-Pillar aluminum trims.
Cheers,
Tom
Comments
Can't wait to see the final ... Keep us informed