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Rolling road tuning or DIY


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I've done about 100 miles on rebuilt engine on bike carbs, with race cams, ported inlet, lightened flywheel, 1.4 to 1.6L conversion using different rods n pistons. Shallow sump with shortened oil pick up and racing baffle plate. s

I have gone to round 4000 rpm on 2nd gear. I am using a default tuning map with megajolt.
It runs spot on. I'm using a KS3 Phormula knock sensor  and everything seems fine up the 4000 rpm I have taken it.

My question is; Can I tune it using a KS3 knock sensor and some sort fo timing light?

I have always wondered how do they hear for knock on the rolling road when it is very noisy?

I was at a rolling road once and it seems to me they were tuning it to AFR , so they kept advancing it and keeping an eye on AFR.
Maybe from thier experience they are able to know from AFR when to stop advancing.

There is no way anyone can hear for pinging. It is so loud in there lol
No wonder DIY tuned engines pop on rolling road.

I think it would be safer for me to use a knock sensor. Atleast you can avoid damage.

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Noise cancelling headphones fed by a tube or amplifier? The knock ding/ping is very distinctive over the usual rattle and whirr. Phormula sell them.

 

You could always force knock to occur on your engine at low load 1500rpm by advancing timing at that rpm by 2 degrees until the KS3 reports it and you hear it too (their own instructions say don't rely solely on the KS3). Then you know what to listen for and that KS3 is working. Reduce it back after this experiment.

 

Then try the same at 2500rpm and see if the knock occurs at 1 degree higher or 1.5 or 2 higher. That establishes the safest rate of advance for your engine, usually 1.5 degrees per 1000rpm. 

 

If you can't bear to do that, then pay the money for rolling road, making sure they can cope with your  Megajolt ECU or you may end up paying £60 an hour for them to learn how to program it. Make sure they are happy with bike carbs too.

 

Over about 3800rpm max advance is determined by combustion chamber shape. You can't make the flame front move any faster away from the spark plug. Ignite too early and the rising piston compression stroke is partly wasted and power stroke does not hit max speed at optimal crank angle. Think of pushing a child on a swing, it only rises so high and your arms can only move so fast downwards.

 

Rolling road tune can work cell by cell on an ECU fuel map leaning from rich (12.5 ish) and then advancing to see if it brings any power loss back without introducing knock. Often leaning increases torque at 13.2 ish, but does increase chance of knock under load, so then needs less advance, losing the advantage. Under low-load partly closed throttle the cylinders are often only partially filled with new air and fuel, (especially with race cams and large overlap as exhaust gas can be sucked back in) so less fuel is needed. 14.7 stoich is responsive engine and emission gases are easy to control with catalytic convertor. 

 

Doing that with carbs is more work as the AFR range varies so much more (flow not mass).

I see mid 15 cruise to occasional 12.0 at high load transitions.

 

Popping on a home tuned car is usually unburnt fuel igniting in the exhaust. 

 

DIY you'll have to match flat spots in responsiveness to situations and engine load/rpm before correcting and checking. KS3 will keep it safe. Measuring acceleration accurately and repeatably is hard as an amateur. 

If car is already feeling smooth I fear you are likely to only get marginal gains from ignition map change; unless you intend to change fuel octane or add extra combustion cooling, like water or meth injection. 

 

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Steveo: 

 

4th pdf from bottom is the default megajolt map im using.

 

 

@DVD; I'm surprised how smooth this default map is running. EVen though I have not really taken it past 4000 rpm, Just feels smooth.  Wonder if I should give it a go at ragging it lol

 

I think to set up KS3 you have to atleast red line it, then you have the max limit, you then store this number. so if for any instance the device reports viberation above this number, it alarms.

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