57 replies to this topic

[klivins]

Cheers jaydee
The head is now in the hands of specialists...
Valve guide tolerances, valve lapping, and head skimming is ordered.

[klivins]

Here are the report of what has happened since.
The valve guide tolerances was too small. The engineers enlarged them to within specs. Now the noises are gone. Will take the mini out on the road tomorrow. Seems I have profiled the needle ok-ish up to 4000 rpms. Didnt want to rev her too much on the idle.

[jaydee]

Glad you got it sorted!!

[klivins]

so far so good, thanks
seems my needle polishing is on the right way. Plugs in nice light brown shade. Idle a tad erratic. Could my CR of 9.5 be too little for 266 cam?

off to Hungary in my Mini in a month!

[jaydee]

I'd say 10:1 is better, but leave it as it is for now, dont warry about lumpy idle, just set idle speed at 1k rpm then check with headlights and driving lamps on if the engine can idle.

[klivins]

thanks jaydee for your help. The Sunshine now has passed MOT and is fully roadworthy. Still, I do not like idle. And yet to do some trial and error tuning for my megajolt map...
May be someone have seen an online crush course for megajolt tuning?
Cheers!

[jaydee]

Mabye on autosportlabs.org you can find something.
How lumpy is the idle? bear in mind the 266 has a slightly broken idle charateristic, which i think you can smooth out trying 10° advance at idle and a tad richer (in some cases leaner) mixture, it is a trial and error, i think if you spend some time on it you can get it to idle smooth like a kitten. Personally i wouldnt bother that much with it and spend the time fine tuning the advance curve to get the most out of it when engine is under load.

[klivins]

at last found local helping and understanding soul - in Technical Faculty of University labs they have a rolling road thingy where they are keen to try both SU carb and megajolt. I call it a win win situation as Im paying only 20 lats (25 quid) per session never mind how long it is!

[klivins]

http://dl.dropbox.co...6671/RR0001.pdf
results of my rolling road session. The guy was helping, but completely useless for SU... All we did was tried my 2 needles what I tried to profile one leaner, one richer. His lambda thing showed engine running way too rich, although spark plugs colour were a tad on the lean side. Another strange thing the power and torque graph shows sharp rise at about 3900 rpms (we tested up to 4000 only) but on one go the effect was missing.
Any comments would be greatly appreciated!

[klivins]

bump

anyone with experience and/or knowledge in rolling road techniques please have a look in a pdf in above post, and please give some comments

[klivins]

still feel of bumping the thread. Would be happy if someone with knowledge in rolling road could give come comments regarding the diagram above.

[jaydee]

http://dl.dropbox.co...6671/RR0001.pdf
results of my rolling road session. The guy was helping, but completely useless for SU... All we did was tried my 2 needles what I tried to profile one leaner, one richer. His lambda thing showed engine running way too rich, although spark plugs colour were a tad on the lean side. Another strange thing the power and torque graph shows sharp rise at about 3900 rpms (we tested up to 4000 only) but on one go the effect was missing.
Any comments would be greatly appreciated!

Oh mate i was sure i had replied, but it seems like i dont...
Often see that about 14:1 AFR on the NGK and unleaded fuel give the spark plug a greyish colour..anyway the sensor will need to be nice warm and give the engine a good trash to clean up chambers and exhausts off the choke deposits that could affect readings.
Dont be shy at test up to 6k rpm in 3rd and in top gear..(as long as the car is well secured it wont jump off the rollers!)
At a guess idle mixture is too rich, i'd be reprofiling another needle, prefiling carefully the first 6 stations for cruising and then the other are a guess for full throttle runs.
I look for 0.9 lambda which is a good compromise for performace, i find that a value near 1.0 is good for power and fuel consumpion too, but always lack a bit of midrage torque and pull. Obviousely you can have both worlds, and i prefer a much torquey setting..
The HS4 is too little and the strange raise at 3.9k rpm has probably a connection..
Could even be something ingition related, IIRC you have the megajolt which makes things easier (if no megajolt you should check the timing curve with a timing gun, disconnect vacuum take-off and accelerate slowly from 1.5k rpm up to 4 k rpm, take note of the advance at each 500 rpm and draw the curve)
I find that 10° at 1000rpm then 20° at about 2000/2500 rpm then up to 32° at 3500/4000 rpm is a good curve to try for a torquey engine, but that depends also on how much advance the engine can take and the type of fuel you use. Higher octane fuel allow you to use a more aggressive advance curve. Also a very high max advance is not always good for performance, and poor unleaded fuel is not good for a max advance of more than 30°.

[klivins]

cheers, much appreciated!