I would say yes, smoothing the combustion chamber can definitely help reduce hot spots, which can reduce pre-ignition, which can help suppress detonation.

The amount you change the compression ratio based on head shaving has to do with the volume of your combustion chamber in the head, which sounds like it could have been increased a little during the deburring. This might lower your compression ratio a tad. Many race machinists pipette out the head to calculate compression ratios incredibly accurately.

If you actually LOSE power at higher boost at the same AFR and slightly lower ignition timing, then you very well might be detonating. If it increases less per psi than earlier increases, that can simply mean you are at the limit and starting to choke something. It could be the turbo's limit.

If you try for more power on E85, watch your injector duty cycle. Don't let it go above ~80%. If it does especially if the temps are warm that day, time for bigger injectors.

 

Unless you go nuts, you will not lose more than 0.1 points of static compression ratio by doing a full smooth-out of the chambers, including a LOT of smoothing. You can see how far I went in my cylinder head P&P thread and that was ~1cc per chamber. Nothing to worry about, there.

The other part of that is that Hyundai left nasty corners in the chamber that gather solid carbon gunk. Clearing that out can't but help reduce hot spots.

 

I love mentally challenging conversations like this! Wakes up my brain from "work mode" which is akin to "sleep mode" ROFL.

 

*laughs*

I'm with you! I run around posting the way I do to spur thought-provoking conversations. I can pick up tips and tricks all over the place!

 

I completely agree with you dmdicks. I hate to butt in on an awesome read, but I am so curious about E85. I think we should have a thread for it. With maths and lots of it. lol.

I'm looking to boost 10-12 psi, which is cutting a little close on stock internals. This leads me to E85, which would prevent me from detonating and also cool down the EGT. The only thing I'm concerned about is my Injector size and Pump size. Currently, the turbo build is going to keep the stock FPR and rail. Would this need to be changed with E85? Keyword Need, because I'd rather keep my engine from blowing up sooner rather than later.

My injectors are 440cc, which I'm assuming would need to be larger for the conversion. I'm thinking 600cc.

 

lazyshot -
You need to figure out your expected power after modification or your power goals. rceng.com has some great calculators. I use 0.55 lb/bhp-hr as a brake specific fuel consumption for gasoline on a turbo motor. Take your gasoline requirements and multiply them by 1.4 to figure out E85 injector size (with a little headroom).

 

Thank you all so very much for the replies! Didn't expect to get this many! So it looks like I will be shaving the head, I might make it clear to the machinist that I intend to run a turbo setup in the future so that he may leave me slightly more head room. However, I've seen some amazing NA setups and maybe just going for the max compression ratio I can get out of the head would be a good idea as well. I'll strongly consider the E85 conversion if I do decide to go for a turbo, it sounds like a good move.

Once again, thank you all very much and if there is any more to add, feel free to let me know!

 

"Actually, twice the fuel would be 100% more. dmdicks is right, 30% is about right."

- that's based on my experience. isn't 18% duty cycle against 35% duty cycle on injectors roughly twice the fuel needed for the same AFR?

 

Duty cycle is dependant on both pulsewidth and engine speed.