Opinions on prechamber swapping, and ceramic coatings

[RabbitJockey]

I've mostly finished what i had set out to do with my rabbit project, so this year i plan to build my car port into a garage (i've been working out in the elements all these years.)  so my old mk1 jetta coupe project is now on my mind, because it will then be moved into the garage to finally finish it.

it's a mechanical 1.6td, and the prechambers have cracks, i will probably end up just swapping the prechambers in from another head that i have, assuming that those ones are still good.  How ever i was also considering installing aaz prechambers, or even prechambers from any other engine, im just looking to get a large prechamber hole, and possibly drop compression a little.  Im not swapping to an aaz head since i have already ported this one and spent the money to have new valves installed.  But i just wondered what input anyone would have on doing this, aaz prechamber is not much larger that i'd worry about hitting a water jacket, i have the measurements at home that i can post later.

the downside to the solid lifter head is that i must run the stock cam as no one offers an aftermarket solid lifter cam... but this is what i have at this point.

the second thing i was considering was to have the pistons and cylinder head ceramic coated increase efficiency and durability.  On the head i was wondering what everyones thoughts and opinions would be on ceramic coating the face of the head in the cylinder, and also the inside of the prechamber, but only the aluminum, not the prechamber itself because that has been done before and it was reported that it smoked white, i think on these engines the prechamber needs to get hot for them to combust and run properly.

[theman53]

I did find a mfg of an aftermarket cam but it is 500 usd I think. also I would just coat the face of the precup as doing the aluminum in the head will probably make it worse. It wouldn't allow for the precup to let the heat into the head for the coolant to take it away. I would just coat the face of the head and the precup part, everything that shows with a head gasket on.
If the aaz precup fits I would go that route. porting mine made it even bigger than the aaz and the jury is still out on how it will hold up. also if the face is the same for the aaz precup it should be the same size iirc, the difference I thought was in the volume on the inside. 32mm face is what most 1.6 were and iirc all aaz, some 1.6 had a 30mm face.

[RabbitJockey]

after doing some reading on old threads, dave from passenger performance had experimented a lot with ceramic coatings, and found the only things worth coating are the pistons and exhaust valves.... i think coating the exhaust ports exhaust manifold and the inside of the turbo housing would also really improve spool up and efficiency, but im not getting in to all that, if anything i'll just coat the pistons, how ever honestly, 1.6td pistons come with a ceramic coating from the factory, im sure the aftermarket stuff is better, and its not really that expensive to get done, but i may not do any coatings.

as for the prechambers, i forgot to get in to that last night, but my heads which are true td and have the marking on the prechamber, are both 30mm on the flange(largest diameter)  aaz is 32mm i believe,  the aaz smaller diameter is also bigger than the 1.6td chamber but not by much, less than 2mm and the height is the same, so its not any scary amount of material that would be removed.

[RabbitJockey]

http://www.powerstrokenation.com/forums/20-6-9-7-3l-idi-diesels-83-93-model-years/134208-pre-cup-size-fuel-charge-ratio-request-review-ideas-2.html

this was an interesting thread i was reading on that forum, they're discussing modifying the prechambers and seem to conclude its not important, they do have the same type of prechamber as us, but they are also not making much power considering the cc rate of their pumps and the displacement of those engines

guys states that he makes 2.4rwhp per cc of his injection pump, which is 120cc.  so hes making 288rwhp with 120cc on a 7.3l v8, so for a vw which is half the cylinders, it would be around 144whp with 120cc, 120cc on a vw idi can make around 200whp i believe.  but maybe that is pretty good considering the amount of drive train losses on a truck that big, and the fact that they can not rev nearly as high.

[libbydiesel]

 

I did find a mfg of an aftermarket cam but it is 500 usd I think. also I would just coat the face of the precup as doing the aluminum in the head will probably make it worse. It wouldn't allow for the precup to let the heat into the head for the coolant to take it away.

The only reason heat needs to be taken away from the head is that it migrates out of the combustion chamber into the head and the metal in the head has limits regarding how hot it can get.  Anything that keeps heat IN the combustion chamber and out of the metal of the head will benefit both engine efficiency and longevity.  All of that said, I don't know what all is worth doing regarding ceramic coatings.

[RabbitJockey]

those were my thoughts, like i said i have a spare cracked head(crack from prechamber to a valve) with what appear to be good prechambers... i'll pop them out and check, i will just use these as long as they are not cracked, and stick up from the deck slightly... the head they are going in, as well as the head they are coming out of have both been cut so there is a chance that they could sit below deck...

[theman53]

I did find a mfg of an aftermarket cam but it is 500 usd I think. also I would just coat the face of the precup as doing the aluminum in the head will probably make it worse. It wouldn't allow for the precup to let the heat into the head for the coolant to take it away.

The only reason heat needs to be taken away from the head is that it migrates out of the combustion chamber into the head and the metal in the head has limits regarding how hot it can get.  Anything that keeps heat IN the combustion chamber and out of the metal of the head will benefit both engine efficiency and longevity.  All of that said, I don't know what all is worth doing regarding ceramic coatings.

It reflects a little heat but not all. Basically, I think it would head soak the precup and then not let it leave if you coated the entire thing. Maybe not. My engine still gets hot, it just take a while

[RabbitJockey]

so it seems in this article, they built this gm idi and ceramic coated the prechamber the way i was thinking, but also went a step further and ceramic coated the outside of the prechamber where it makes contact with the head.  which is pretty smart, and as steve menedez pointed out it would probably require clearancing before pressing the chamber back in.  It'd be nice if we could get a hold of the guys from this article and see how much of a difference they have noticed from this modification, and what experimentation has led them to this method. 

I don't know if this article discusses it, but i've been reading a lot of idi forums, and they all seem to believe in keeping the stock compression ratio to work with the prechamber properly.


http://www.maxxtorque.com/2008/10/the-best-ever-65-chevy-diesel-rebuild.html

[RabbitJockey]

[theman53]

Being a press fit I don't think any of it would stay on.

[Jetmugg]

Watching with interest, for sure.  I'm already noodling around ideas for my next AAZ head.  I'll be shooting for 250HP from my 1.5 Franken setup.  That will be my "Phase 3" setup (hoping for 150 mph+ at Bonneville)

Head porting is definitely on the plan.  I like what Lucas did with the porting on his pre-chambers.  I'm certainly open to ceramic coating(s) if they will help.  In the meantime, it will be interesting to see if the guy from the article shares any additional info.

Steve.