hello all i know my 800 is not a v8 however it might be soon.
anyway today i removed the anti-tamper cover on my ign advance/retard controler on my v6, i changed it from 1 degree retard to 5 taking it from 11 to 15 so i could get the full use of the 99ron fuel, however on the test drive it felt a little slower above 4k is this what i should be getting or is it that with the mods the car has (exhaust, air filter, de-cat) that i have actually made it runn leaner by retarding the ign 4 degrees?
jago.
ign settings for 99ron fuel
Moderator: phpBB2 - Administrators
unless i understand you wrong - you want more advance with better fuel.
I have switchable tables on my turbo v8 - for std fuel i run quite a conservative map, then flip the switch when i get some decent stuff in it.
Look at the areas around 130Kpa - 150Kpa (in boost) you can see that i dial advance back in when running better fuel.
I have switchable tables on my turbo v8 - for std fuel i run quite a conservative map, then flip the switch when i get some decent stuff in it.
Look at the areas around 130Kpa - 150Kpa (in boost) you can see that i dial advance back in when running better fuel.
monty man wrote:hello, thanks for the reply,
i thought that base ign timing was 10 before TDC or -10 and if you want to run higher octain fuel then you need more time for it to ignight as it's harder to burn therefor needing more retard e.g. 15 befor TDC or -15.
You are right in that a higher octane number will allow you to run more ignition advance before you run into detonation but this will only be of benefit to you if you are having to retard the ignition to avoid detonation in the first place.
The ignition is slightly retarded in a tuned motor because the flame speed has increased and therefore the mixture can be lit later. The other reason is to get you out of trouble because the compression ratio has been pushed up too high for the fuel available, what happens is that the cylinder pressure goes too high just after the mixture has been lit, this causes the still-to-be-burnt part of the mixture to sponatiuosly ignite. This flame front colides with the one started by the spark plug and the result is a hole in your piston. (This differs from pre-ignition where you don't have flame fronts coliding, the whole mixture in ignited by a hot spot in the combustion chamber).
This so called cure for too much compression results in a engine that is not as nice to drive as one with the correct compression for the fuel being used and the right amount of ignition advance.
Your 99 RON fuel will allow a higher compression, it will allow more ignition advance before detonation occurs but unless your mixture is still burning ATDC it won't do any good. Having said all that maybe most cars run slightly retarded from optimum as a safety feature.
Also too much advance at idle might cause the motor to hesitate when you floor it due to the vac advance kicking in.
The proper way to sort this out is to find out how much advance your motor needs at peak RPM (and possibly peak torque) then modify the dizzy so that you get this setting whilst not over advancing the ignition at idle. (Infact you would do this every 500 rpm).
This is all very expensive and time consuming dyno work and will always be a compromise unless you have a mappable system. I have not so on my Rover lump have just messed about with the bob-weights and springs, this is a far cry from what is possible!
By all means have a go using seat-of-the-pants methods, just don't push the max advance too far!
One final thing...running a motor on fuel with a very high octane rating when the motor does not require it may cause you to lose power, the fuel is too stable to burn rapidly!
Regards,
Pete
hi, the main reason i changed the timing was because of the mods. as i have not dones anything to the fueling yet, so i wanted to make sure all was ok,
on the non cat model the ign is set where it is now(15) on mine and cat models are at 11 retard.
i'm going to move it to 13 later and see then as i'm not 100% sure she's ok, however under high load in 4th or 5th (above 4k) she semed to pull better but that could be because she was not below.
still this is all good learning.
p.s. if any one has a pair of nsx DOHC head about could i see if they fit my spare engine
on the non cat model the ign is set where it is now(15) on mine and cat models are at 11 retard.
i'm going to move it to 13 later and see then as i'm not 100% sure she's ok, however under high load in 4th or 5th (above 4k) she semed to pull better but that could be because she was not below.
still this is all good learning.
p.s. if any one has a pair of nsx DOHC head about could i see if they fit my spare engine
