Maximum Ignition Advance

[Mad Mart]

Can someone tell me what the maximum ignition advance is on a standard Sprint? I think it's about 35 degrees.

What would be the max. adv. on my modified Sprint? My cam has a duration of 292 degrees. I'm not sure what other information is required to calculate this figure.

I'm trying to get a better understanding so I can create a better map for my Megajolt. As I don't have a distributor I am not limited to spring & weight values.

[gmsclassics]

With my STR139 cam I run 32 degrees max advance, but to achieve this the advance weight stops had to be filled away a little, yet maintain a semi normal advance at tick over.

Specification for standard car is a centrifugal advance of 12-16 at 2000rpm (plus whatever static you set) so gives a total in mid twenties. (Ignore vacuum advance - disconnected on my car anyway with Dellortos).

I tune to car to 32 degrees at 2500-3000rpm using a strobe.

When I first did this I found a lot of difference between distributors in what they were giving as standard, due to wear I'm sure.

Geoff

[Mad Mart]

This is the map my Sprint is currently running on. I have it set at 14 BTDC at idle and rising to a max. of 32 @ 3500rpm. under no-load conditions.

The Megajolt comes in two flavours, either tha MAP (Manifold Absolute Pressure) or the TPS (Throttle Position Sensor) for Load calculations. I have the TPS version so the load on the 'Y' axis is the percentage the throttle valve is open.




I'm not sure how much I should retard the ignition for the various degrees of load.

Ultimately I know that a Rolling Road session is the only way to sort it properly but that can work out quite expensive.

[gmsclassics]

Hmmm! A lot more sophisticated than mine.

I suppose mine would be 32 degrees max under load, given that when racing the throttle is open as the car is accelerating right up to the point of hitting the brakes. There is no cruising or partial throttle.

Why not up the ante with a more vicious camshaft? Certainly no point in the expense of a rolling road until you have finished all the setup. Interestingly, mine has never been on a dyno, it has always been about tweaking until it seems right.

Geoff

[Dolly-Nut]

Recommended max advance varies with different setups but 27-31 seems to be the range where max power is achieved with Sprints.

[DF]

get some det cans and go play

[soe8m]

32 max. The head is a good design with a central sparkplug so it doesn't need to be advanced that much. More than 32 and you are going to go backwards again.

Jeroen

[tony g]

Mad Mart, I would be very interested to see your megajolt set up. Im planning one myself and need some input on the hardware etc. What tps did you use and how was fitting it? I'm assuming you are on webers but i will be on su's. Would you consider map sensor better or the same? What and where is your trigger wheel set up?

Cheers

Tony

[Mad Mart]

Tony. There is a thread I made whilst fitting mine, here.

Apparently if you have quite a wild cam then it's best to go with the TPS setup (http://www.autosportlabs.net/Choosing_b ... MAP_or_TPS). I believe my TPS came from a Mondeo. PM me if you need more info.

[geeksteve]

Don't suppose anyone has an ignition map / suggestions for a 1500 do they? I'm building an electronic ignition system (EDIS based, but not Megajolt) and some rough figures would be useful.

Steve