4AGZE head skimming

[Ben Wilson]

Not this one, but here is a virgin smallport head I've got in the shed:

[ohms]

Was thinking about seeing how many GG;s can be liberated with the sc12, so was planning high comp, cams, intercooling, big pulley and toluene injection. Coul;d be a bit of an animal in street terms.

[YLD-16L]

Just thinking out loudly, assuming that those Singh grooves do make an improvement to the mixing of the air/fuel through increased turbulence. Is it possible that the angle/position of the groove could have varying results (I assume it would)?

At the moment the grooves essentially position on either side of the dome (0 = dome) like this --0-- but would it be possible to generate more "mixing" by having the grooves angled like this /0/ to create a "swirling" turbulence?? Or even two grooves each side that are angled??

Just talking out my arse but thought I'd put it out there

[Ben Wilson]

I thought about that, but I was worried I'd get a nice spiral of gas with a hole in the middle where the spark plug is. I'm working on the theory that getting the most turbulent mix near the spark plug should be a good thing.

[YLD-16L]

Good point Ben.

Still be nice to have the time to try a few different methods and compare the results one day - maybe when I retire

[jezza323]

are you concerned about getting hot spot detonation with the grooves in the combustion chamber?

[Ben Wilson]

Not really, the edges aren't that sharp. I've seen aftermarket pistons with much sharper edges on the valve cutouts. It's not really apparent in the photos, but I went over the 'points' with a fine file and rounded them all off as well just in case.

[Roundy]

that is fairly intriguing read to say the least...tho nothing is proven, it sounds good in theory!

any plans for a comparison

[Ben Wilson]

Sure - Anyone willing to build an 11.5:1 motor and see if it survives with standard management?

[kingmick]

Not really, the edges aren't that sharp. I've seen aftermarket pistons with much sharper edges on the valve cutouts. It's not really apparent in the photos, but I went over the 'points' with a fine file and rounded them all off as well just in case.

Sharp edges only till the builders that know what they are doing blend the pistons! Takes time to hand blend them and you need to know the tricks for extra special but for run of the mill it isnt hard, Just do as its said, blend!

[kingmick]

Sure - Anyone willing to build an 11.5:1 motor and see if it survives with standard management?

If you run pulp, the stock ecu runs plenty rich so 11.5 in a properly setup chamber would be no problem, unless you had wild cams, on stock cams and pulp at worst you would only need to knock a little timing out of it.

[Ben Wilson]

That's what I'm hoping - I'm 90% sure it will be OK on 98. Once I'm happy with it, I'll try it on 91 and see if the grooves do any good.

[nick.parker]

Hi,
This link is from the website of the place I work (Orbital Australia) http://www.orbeng.com.au/orbital/dir.../technical.htm

Not to belittle at all what you are talking about, I think pretty much all the benefits you are talking about with these grooves are easily and consistently achieved with direct injection, be it air assisted (as in where I work) or high pressure direct injection as in automotive OEMs.

Air assited direct injection basically achieves excellent atomisation with relatively low injection pressures, using high (actually quite low < 200kpA differential ) pressure air to blast some 'pre metered' (via convential-ish injector) fuel into the combustion chamber, sometimes special pistion designs are used to direct the air fuel mix to a certain area. Another advantage is control exactly when the mix passes the spark plug.

At low loads, by having an ignitable afr near the spark plug ('stratified charge') the rest of the cyl sort of doesn't matter and you can run as lean as say 60:1.

Using Air Assisted DI, I have seen a few two stroke idle stably at full throttle just by using a low amount of fuel and very careful injection timing etc...its great stuff.

And presumably you have seen/read of the new breed of HPDI (high pressure direction injection) cars coming out than run turbo boost and 10:1 compression .....

Cheers, Nick

[oldcorollas]

stratified charge ftw!!!!!!

[Ben Wilson]

Nick - cool stuff, are you going to donate the hardware?

Doesn't it have an inherent problem with the injector taking up valuable head real estate?