The V8 Owners Forum -

Hello all,

Anyone read the "tuning & modify the rover v8" book...by the lloyds....?

max timing for my 4.6 engine.....is said to be 26-28 deg @ 3000 rpm.......

I do have 26 at 104kpa and 36 deg @ 16kpa in my map at 3000rpm depending on map reading

Are my settings to much or ok?

thanks
scott

vacuum sites will tend to use higher timing.

Tuning on a dyno will let you determine what the engine wants

Sounds like a decent starting point at that RPM although your closed throttle pressure of 16kPa sounds a little low, just over 24"Hg if I've done the math's correctly (I hate that scale but more people seem to find it easier to relate to), maybe at 3000RPM you will obviously needs checking. I'd presume you'd only see those figures on overrun though so possibly not too important. You may gain better cruising MPG if you either increased the amount of vacuum retard or maxed out at higher MAP. Obviously many more areas of mapping needed and as Stevie said best done on dyno.

You may also want to look into adding more RPM (centrifugal) advance at higher RPM too.

here's, a pic of my full ignition table, i was just a bit worried i had too much timing......as ive not yet had it mapped......as vems tuning in the UK....is all but none existent...



regards
scott

Hi Scott
A bit more information may be useful if you have it.
Is this a distributor based or multi-coil setup?
Evidently you're measuring load based on Manifold pressure, are you able to see what pressure you are developing when the engine runs via the software?

You may find that at idle your pressure does not drop as low as 16, this area of the table would most likely be used at higher RPM with closed throttle, in other words overrun, depending on your fuelling this may not be used at all


On my system I have added advance at my idle pressure (Only just over half way down) and reduced to 10° at WoT (104kPa) in your case, I also have a column lower than idle where I pick the timing up a couple of degrees in an attempt at anti-stall (not proven yet) and and even lower column where I've backed advance off further to allow me to prevent kick-back or additional load on the starter during cranking. I have 16 columns to play with so can afford a little extravegance!

In your table you have 14° at idle speed regardless of load, that seems quite high in generall but maybe not for your engine in your car but I think would be worth having some increase going down the column.
Most production systems remove vacuum advance at idle by piping the vac' takeoff to the upstream side of the throttle, apparently this is only done for emissions purposes, if that is not a concern to you you may benefit from increased advance at closed throttle as this should allow your engine to run cooler, again I've still to test this on mine but I think it's worth testing

I had 30 degrees max timing on full throttle with my previous (4.6 litre engine with Merlin heads, just under 11:1 CR). Just after max. torque rpm the timing advances to 32 degrees. I need to check but IIRC from 5000 rpm to 6500 rpm. We gained quite a lot power on rollers by advancing that 2 degrees. Further advance to 33 degrees gained nothing so we changed it back to 32 degrees. My ignition is wasted spark and Haltech ECU.

I would say that 36 degrees is too much at full throttle. I also run almost 40 degrees at light loads

some great comments thanks.....as i've still not had my car tuned....since the 5 year rebuild on the engine & gearbox....im just trying to get road miles on the engine.....its driving ok.....but I'm just concerned of doing some long time damage......with higher than needed timing...

Engine is 4.6 GEMS setup
wasted spark
Full Cam Sync
45KPA on idle
16KPA is on overrun, i was unsure how far the table should go.....idle or into overrun?

I'm still learning......so any info is appreciated.

It might pay to start looking for a VEMS tuner again, after the last guy i talked to left for germany to work.....so knowledge for my setup is thin on the ground...

regards
scott