Twin Plenum Ignition advance

[gacksen]

Hello,

as i have put the custom twin plenum on the engine some weeks ago looking for
advice in regards of ignition timing. engine is a 4.6 eales unit with different cams
heads etc and and a canems ecu.

dyno plot before the twin plenum :



made several runs on the autobahn with the standard map and having an eye on the AFR gauage.
car was running at full WOT in the 13.2-13.5 compared to 12.5-13.0 before so gave the girl
a little bit more fuel that it went back down to 12.5-13.0 at WOT until the rpm end.
ignition total comes in with 28 from 2500 onwards until the end at WOT.

the general consensus seems to retard the ignition with a larger throttle body but why and
at what point in the WOT rpm range ? i am running 98 octane fuel only.

Edited by gacksen on Tuesday 4th August 11:26

[gacksen]

have thought about some dyno time once the outside temps of 35C or 95F will come down a bit.
what i have done had been just to alter the timing by one degree from 2500
upwards to 29 and downwards to 27 to see if a difference can be noticed.
the spa oil temp gauage shows me the engine runs much cooler with retarded timing to
27 but does not have the punch up to 4500 rpm as with 29. timing at 29 the oil
temp goes up quite quickly.

[gacksen]

maybe youre right conclusion would be to get an oil cooler in

[gacksen]

blitzracing said:

Not really- as I understand it engine temp goes up if the ignition is too retarded as more of the heat generated when the mixture is burned goes into the engine instead of pushing the piston downwards, but there are so many variables, that's why you measure it on peak torque to prove the maximum power is derived from every piston stroke when the timing / peak burn point (12'ADTC) is optimised.

best will be to put it on tue dyno with different maps and see what happens.

[gacksen]

MPoxon said:

That is pretty impressive figures from a 4.6. What is the full spec of the engine and cam if you don't mind me asking?

x bolted 4.6
some sort of stage heads from eales
eales cam
canems ecu

cant tell that much as engine had been in the car when i bought it and up to date never opend up. should be in plus minus similar spec to the one phazed has as per dyno figures.

as for the sense or nonsense of a twin plenum the primary goal had been better throttle response and that has been fully accomplished. the overal feel of the car accelerating is different to before. if it makes sense power wise in chasing some horses cant answer. is it worth buying custom headers for 2k and getting another 15 horses ? if you think so you have them if not .... not...

[gacksen]

had a short stop at the local dyno today. guy was awesome as usual doing multiple runs in the lunch break.
difference in timing of 2deg was barely noticable. more important is to get the fueling sorted. car does
like it to run in the high AFR 12´s. if low 12`s power and torque will drop. gain with sorted fueling and ignition
another 8hp and another 10 lbft. problem of course the missing base with the standard plenum to compare.

[gacksen]

Kokkolanpoika said:

I have build dozens of rover engines, and what i have dynotested those, usually WOT ignition advance should be near 28deg over 3500rpm or near 4000rpm.. If you have got more advance say 25deg@2500rpm you might lose over 20Nm of torque..
Ignition curve should be linear on RV8.. Approx 4.6l engine will need 8deg idle speed advance and max advance should be approx 28deg@+3500rpm..
All depend´s on engine compilation..

total advance is all in at 3500rpm. strange thing had been that with fueling corrected at both linear curves with 27 or 29 there is almost no difference in torque or horses. will check the ignition with the strobe those days to see if anything is alright. as per my understanding is to aim for max torque at least possible avdvance and once peak torque is over tjat is around 4500 then start to advance more.