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Unnatural Aspiration part 3


stony

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So what did you see that makes you say 17 degrees was as far as you could go? I have never had any issues with cometic. I have always surfaced both the head and block to the recommended 60 ra. My car hasn't really seen any street duty yet though. its lived thru 100 gallons of fuel on the dyno and about 100 passes so at most 60 miles ;> 

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So what did you see that makes you say 17 degrees was as far as you could go? I have never had any issues with cometic. I have always surfaced both the head and block to the recommended 60 ra. My car hasn't really seen any street duty yet though. its lived thru 100 gallons of fuel on the dyno and about 100 passes so at most 60 miles ;> 

 

It wasnt gaining much more power on the dyno with additional timing, i could have ran another couple degrees but the gains had dropped off alot. it made 760whp on 30psi.

 

Mine was surfaced at the recommended 50RA as well it lasted quite a while, just stating that the Apexi gasket is far better in terms of cylinder sealing around the combustion chamber. It has a full fire ring around the cylinder and seals all the layers together instead of just some raised unsealed edges like the Cometic. Just letting you know as i know you make alot of power and use Nitrous. 

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Cool thanks for the heads up. Last time I checked, cometic had a head gasket that had a ring around the combustion chamber also. I haven't really started shopping yet. I suspect my compression ratio was pretty low on the combo that I had before. One of the squish areas was removed from the head and it had a 1.2 millimeter head gasket in it. That may have been why I could go so far on timing. Changing things up a little bit this year shaving .5 millimeter off the head and going with a 1 millimeter head gasket. looking to make a little bit more torque off the turbo in the lower end.

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Yeah i saw they have a new line out, but i don't think they have an application for the RB26 yet. 

 

If i remember our phone conversation right, you were able to go really far with timing?? Or was the above a typo?

 

My compression is really low, its about 7.8. I'm running a 1.5mm gasket as when i initially built this motor it had really tight Piston to Valve clearance. (.050) with a 1.2mm gasket, i opted for the thicker 1.5mm so its currently .060.

 

I never did get an exact measurement on quench clearance but i assume its close to what it should be as the block and head had been milled and the pistons hang out some, its got to be close to the .040 standard.

 

How much torque where you making?

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Mine look very similar to yours but mine don't have valve reliefs. same dome look etc, just no reliefs.

 

What pistons are you running? I like the reliefs, probably why i have such tight Piston to valve clearance. 

 

 

EDIT, after some research i assume your running Tomei pistons, are those 2618 alloy? 

Edited by flatrate
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They are older HKS pistons. But looking around they are still making the same design.

 

Still find it curious that you didn't get the same gains I did in timing. Really starting to wonder if my timing is not indicating correctly. especially since at 18 degrees it was too retarded to put any boost to it. I had to get it past 18 degrees before it would make a full pass on the dyno without breaking up. I did have to change the CAS sensor gear in the cam. I installed it 180 degrees out but that was fixed by rephrasing the coils to match the firing order. But verifyed mech timing it show correctly.

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yeah i had taken a couple degrees out on the dyno just to see if it was going to net a huge loss ( just wanted to make sure i was safe) 2 degrees pulled and it lost 30 hp. Put 3 degrees back in (so only 1 more than i originally had and it made 37 more horsepower. so i gained 7 horsepower with that 1 degree, which is worthy but the gain was cut in half compared to each additional one prior. i thought it was making good power as it was so i just keep it at 17.. but im sure i could get away with a few more if i wanted to push it, but its a street car :)

 

i have locked timing with the EMS and checked with a timing light for any timing wonder, just free revving the engine, and it does retard itself 1 or 2 degrees when i rev the engine around never advances, always retards. so i suppose my actual numbers could be retarded by a degree or 2 but i havent actually checked during a run on the dyno.

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  • 1 month later...

Well motor is almost back together. Hope to have it fully assembled in a week or 2 and ready to go back in the car. just waiting on rings, Head gasket, and getting head back from machinist after the valve job. 

 

The CXracing pan needed a little trimming and the bracket the oil pickup mounts to was way off. BUT it looks like it will hold significantly more oil then the stock rb20 pan i was running before. Also has really good welds and from i can tell some pretty good baffling. 

 

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New billet wheel in the T88-34D

 

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