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By dazq
#9370
But what if the engine is accelerating? This rate if change over 1 revolution could be considerable especially in a revvy 2cyl? I understand thats the reasoning behind more teeth on the trigger, shorter trigger time gap makes less room for inaccuracy due to change in rpm.
By noisymime
#9407
I can put together a decoder for this fairly simply, but as mentioned it is very low resolution.

During cranking, particularly on something like a 2 cylinder engine, the rotational speed of the crank can nearly double/halve within a 90 degree window. This is the reason why higher resolution wheels are usually preferred. It's fine to say this is the speed at tooth #1 so it should take x ms to reach tooth #2 80 degrees later, but if they happen to be around the start/end of a compression stroke then there's no way that estimate will be accurate.
By mmonsterski
#9435
noisymime wrote:During cranking, particularly on something like a 2 cylinder engine, the rotational speed of the crank can nearly double/halve within a 90 degree window. This is the reason why higher resolution wheels are usually preferred. It's fine to say this is the speed at tooth #1 so it should take x ms to reach tooth #2 80 degrees later, but if they happen to be around the start/end of a compression stroke then there's no way that estimate will be accurate.
Correct... That's why original ignition module just fire at 3 tooth below 1000 RPM :) ( Something about 10 BTDC )
Image
(There are two characteristics - one for partial and one for full load)
By noisymime
#9440
That's fine then, there has been an option added recently for fixed cranking timing on decoders such as this, so I can implement that. I'd forgotten that the 2 cylinders aren't 180 degrees apart on these engines, so that should work fine.
User avatar
By Kelvinator
#10721
Hey, im still pondering what car to put my Speeduino in but it looks like im fairly set on a Rover V8 now (since the MR2 sold).

Looking into it, the car is already EFI, but a very primitive Lucas/Bosch system. Most of the system is straight forward, but im trying to get away with not removing the crank pulley and fitting a trigger wheel. Ultimately im fine with not controlling the spark if i cant, im mainly after fuel control. Still want to run distributor for originality.

Can the Speeduino accept something like this? The standard distributor has a toothed wheel, with 8 evenly spaced teeth and a VR sensor. No TDC marker.
Image

Apparently on Megasquirt you can run an HEI module if you want to control the coil/timing.

http://www.msextra.com/doc/ms1extra/Ign ... htm#gm7hei

This is how the system is setup standard,
Image
By dazq
#10723
Kelvinator wrote:Hey, im still pondering what car to put my Speeduino in but it looks like im fairly set on a Rover V8 now (since the MR2 sold).

Looking into it, the car is already EFI, but a very primitive Lucas/Bosch system. Most of the system is straight forward, but im trying to get away with not removing the crank pulley and fitting a trigger wheel. Ultimately im fine with not controlling the spark if i cant, im mainly after fuel control. Still want to run distributor for originality.

Can the Speeduino accept something like this? The standard distributor has a toothed wheel, with 8 evenly spaced teeth and a VR sensor. No TDC marker.
Image

Apparently on Megasquirt you can run an HEI module if you want to control the coil/timing.

http://www.msextra.com/doc/ms1extra/Ign ... htm#gm7hei

This is how the system is setup standard,
Image
Yes speeduino will run this ok for fuel , but it is a bit low resolution for ignition tbh.
The trigger wheel kits are pretty easy to get hold of and easy to fit see here for an idea
http://www.megasquirt-v8.co.uk/ms_3-5_etc.php

If you do go full spark you will need go keep the bottom of your dizzy anyway to run the oil pump(just cut n machine the top off leaving just the shaft stump)
User avatar
By Kelvinator
#10724
Ah excellent, thanks for the reply. Im guessing its "basic distributor". Im presuming itll still play nicely with the standard distributor, vacuum advance and all?

If i were to replace the standard 8 tooth wheel in the distributor with a 24 tooth wheel (with a missing tooth or two), would that be sufficient to also run spark?
By noisymime
#10726
Kelvinator wrote:Ah excellent, thanks for the reply. Im guessing its "basic distributor". Im presuming itll still play nicely with the standard distributor, vacuum advance and all?

If i were to replace the standard 8 tooth wheel in the distributor with a 24 tooth wheel (with a missing tooth or two), would that be sufficient to also run spark?
For purely fuel injection the vacuum advance etc won't make too much difference, however if you go to the higher tooth wheel and do ignition then you'll need to disable any advance that gets applied to the wheel.
By dazq
#10727
Kelvinator wrote:Ah excellent, thanks for the reply. Im guessing its "basic distributor". Im presuming itll still play nicely with the standard distributor, vacuum advance and all?

If i were to replace the standard 8 tooth wheel in the distributor with a 24 tooth wheel (with a missing tooth or two), would that be sufficient to also run spark?
Yes ,basic distributor

Also if you keep the dizzy for spark distribution once speeduino is doing the calcs when you lock the dizzy be careful, the rover v8 suffers badly with crossfireing to the wrong plug if lockwd out in the wrong place .
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