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engine specs, head cc, HG thickness for D15A2

Discussion in 'Civic and CRX - EW' started by itjstagame, Jan 23, 2008.

  1. itjstagame

    itjstagame New Member

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    Ok, I've decided that I really want to drive the car and can't hold out for a cheap EFI engine and I really don't want to deal with converting the fuel system at this time.

    So I'm still going to look for a manual tranny, but want to rebuild my D15A2 ('87 DX). It pretty much just needs the head put back on and I'm done, but while it's off I was wondering about some modifications.

    I'm trying for MPG and I've been wanting to try Somender's Grooves (SOMENDER-SINGH.com - Home) and with the head off is the best time. Now I was worried how I'd lean out the fuel mixture to take advantage of this since I had a carb and started thinking, I should just deck the head and increase compression ratio.

    I saw one site that said CR was at 9.2:1 by default, but I can't find info on CC of heads, thickness of HG (and if there are thinner ones available) and how far one can mill before they run into trouble.

    I realize that these engines are all interference already and don't want to increase my worry, but this engine will spend very little time above 3000 rpms and probably not much above 2000 rpms either. At what point will I have gone too far and have issues with the timing belt being too loose, etc? Should I just shave .050" and see what I get?

    Thanks for the info.
     
  2. Celerity

    Celerity Well-Known Member

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    This guy is a quack. I couldn't see enough about what he was actually doing to critique the process / invention / whatever.... but he, he is a nutjob.
     
  3. Celerity

    Celerity Well-Known Member

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    I didn't know you were looking for stuff. I will have lots of FI stuff leftover shortly, and the parts ARE available for cheap. I'm not ready with my parts yet, but if you give me a few weeks (I'll be away at school all next week) I can have a care package setup.

    Shaving .050 over is what I had done (well, I went .060), with a valve angle grind, OS valves and NO porting / polishing, the result was amazing. Since my head is back this time, I can't find the ".060" etching in the head anymore. So it's gotta be down a tenth. I'll keep everyone posted with the project.

    at .060 I ran low octane without problems. Also, don't assume you'll never be over 3000 rpm. If you car can do 2000 rpm it can do 8000 or so RPMs.
     
  4. itjstagame

    itjstagame New Member

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    Sweet! Yes I'm new to the board and haven't caught up on active projects, etc yet. As for parts available cheap, I've only been looking for a week or so. I don't mind the wiring stuff for EFI, I'm pretty good with that, I just didn't want to deal with the gas tank, fuel pump and fuel line for FI.

    As is I'm just looking for MPG so if I can raise compression and get every bit I can out of the carb it'll be fine.

    You're saying you have the 12v motor I have and aren't pinging with .060"? As for valves, etc, the reason the head is off is because the exhaust valves were bent already. They were replaced already the head just wasn't put all back together. I'm not sure if they didn't any porting or angle grinds etc, I haven't actually examined the head closely yet (I have no garage and it's really cold outside ;) ).

    Anyway Singh is crazy and the site is laid out like any other fake technology trying to steal your money, except his info is free. I've never really tried reading the site myself, just seen discussion on the idea in forums etc, I just included the link because it seemed the source reference. The idea is trying to get a more complete burn in the clyinder (which Hondas probably already do anyway, I'll have to look at how the CC looks and decide if I want to do something). Basically you can see burn marks/residue on pistons after thousands of miles of service and can tell that the whole piston is not the same color and that part of the piston isn't receiving the flame front. This seems to work best on small block chevies since their 2 valve set up has a very small almost flat CC for half the chamber and then the other half is bigger and has the valves. This flat area has trouble getting the flame front and what people do is add small, narrow, slits into the head to direct the air charge from this area and toward the spark plug as the charge compresses.

    It's interesting and seems worth a try to me.

    Hearing that you're not pinging makes me wonder how much more I can shave off :D. I'd like to be right on the edge of pinging and will use higher octane if I have to. Any idea if there are thinner HG available? I already have a new one the previous owner bought so I'll probably use that, just trying to find info. As well, after your mill of the head, are you worried about the cam gear lining up or maybe being off time? Are you using adjustable gears?
     
  5. Celerity

    Celerity Well-Known Member

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    I have an adjustable gear, and the tensioner is good for some play to keep the belt on and stable.

    And Free information is worth exactly that, when it comes to this crazy cat.

    Also, be careful with this compression. I've done LOTS of homework, and I'm an experienced engine builder. There is a fine good chance my design won't work. (I'm thinking it'll be like 14.x:1 compression) Some cars today run that kind of compression, but heads (Like the Mazda MS series) use high static compression with higher turbo compressions, but they also use a diesel-inspired injection system that runs 1600psi (Yes, SIXTEEN HUNDRED PSI) injectors, and lots of retard to make it work. If you put too much compression in, too much combustibles (fuel and air) you can see your pistons and valves lock up like they hit steel.

    I had a Supra that ran ultra high compression, and it wasn't pleasant to feed that beast. This time around I'm using Suzuki dual throttle setup with 52mm throttle bodies, re-angled fuel injectors, and starting with a 45 pound fuel delivery. Even though I have NO CLUE what 45 pound injectors will fit, how I'll get vacuum, when to open or close the intake valve or for how long.

    The math begins.
     
  6. itjstagame

    itjstagame New Member

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    really shaving only 0.060" you think you've raised the compression that much? Or did you deck the
    block too?

    I thought you said it was running on 87 at .060, that can't be true at 14:1 compression, that's crazy. I only want a little bit, like 10-11:1.

    Do you have measurements on the cc of the combustion chambers and if the pistons are level with the deck at TDC or how far they're off in either direction? And is this the same head as me, 12v SOHC?

    I'd like to start working numbers too.
     
  7. Celerity

    Celerity Well-Known Member

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    Oh no no ... .060 won't bring you up to 14ish. I think I am at 14ish NOW with the head being decked for a 2nd time. And this I'm only basing on my experience with my Supra, which I had to give to Airjockie because I couldn't feed that monster AVGAS like it wanted.

    Pics of my head are in my build thread in the multimedia forum. I have NOT done the measurements on the new setup yet.
     
  8. itjstagame

    itjstagame New Member

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    Wow sweet, I'll look up your thread. That's a lot to mill off, do you know how close the water jacket is? I don't want to cut into it. Sounds like it's quite far away.
     
  9. Celerity

    Celerity Well-Known Member

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    Oh yeah ! It's definately not near the water paths. No factory machines things within a mm of the outer shell of the device itself.
     
  10. itjstagame

    itjstagame New Member

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    Celerity: So your car was a first gen Si, right? Is that the same block and probably same stuff as mine?

    How much did you calculate your compression to be at .060" milled and do you think it'd still run fine on 87 if it were carbed instead of FI?

    I'm just trying to decide how much I should mill on my DX, if yours really ran fine on 87 then I want to go a bit more, .065-.070, any suggestions?

    I found out NAPA will do it for $60, I just need to remove the camshaft, so I just want to get it done and installed and drive (even if that's driving with the automatic for a while....).
     
  11. Celerity

    Celerity Well-Known Member

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    Yeah, mine is first gen, but the 86-87 Sis were different than older ones. If you're carbbed, then you'll need to put more fuel than air in it for higher compression, and that fuel should have more C8 molecules (Higher "Octane") to push the oxygen out of the air. Also depends on your elevation.

    And yeah, if you trust NAPA to make a precision plane, then go for it. I didn't trust my locals, so I went to a performance shop for mine - and them do the 3 angle grind as well. that grind is what really made the difference. Then I ran the cleanest fuels I could to make everything work.

    Finally, watch that cam shaft, be VERY CAREFUL because they break easily. When you're loosening up, be twice as tolerant of the loosening pattern and torque specs. Most engine manuals give you sigma 1 precision, go with the best you can (take the time to calibrate your torque wrench and shoot for sigma 3 (99% accuracy))
     
  12. D15Beater

    D15Beater HNFTuning

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