dallasstars

Hey everyone! Kinda newish here, so I hope I'm on the right forum. Anyway I have a 2006 Acura TL with a 3.2L (j32a3) engine and a 5 speed automatic BDGA type transmission. I'm getting ready to swap engines and I'm going to get a 3.5L (j35a5) and mill down the heads to raise compression from 10:1 to hopefully around 13:1, I would think I could use 93 octane gas and get somewhere close to that compression, w/ head studs installed. I was using a compression calculator but I can't find the piston volume numbers for either engine honestly. That's my major problem to figuring out the static compression ratio. Has anyone ever milled down their cylinder heads on a j32a3 or j35 engine before to see how much compression they could get out of the engine? Thanx, -Jonathan

619rcr

13:1 is rediculously high even for 93... maybe e85 with bigger injectors and someone who knows how to tune. 11.5 might be more realistic.

dallasstars

My 3.2L(j32a3) is 11:1 and it runs on 91 octane great. I was thinking I could at least get 12.5:1 on 93. These Honda engines are great with compression (especially being all aluminum and having aluminum heads and knock sensor). But the real question is what can I get away with with 93 octane? I'm curious if anyone has milled there heads down before to achieve higher compression on these J-series engines. Some 3.2L Honda engines come stock with 11.2:1 compression. I think they reccommend premium 91 octane for that also.

Jackass

NOTE: I have no idea what I am talking about here regarding first hand experience nor knowledge. Just adding some thoughts and questions.

I don't recall reading any threads over the years with people doing work with the goal to increase compression. Most were looking to reduce compression since they were boosting or spraying. Are you planning to make other adjustments to take advantage of it? A tune? Different fuel maps? Spark timing? I mean what is your goal here? Or you are just playing and seeing what happens?

619rcr

10 sec google search and post skim:
https://acurazine.com/forums/3g-tl-p...mplete-897606/

dallasstars

Well, that will be my goal in the end. I'm taking out my j32a3, I will get 9.2:1 compression pistons for that and valvetrain and everything for a centrifigural supercharger, Eventually. Probably next year sometime. The j32a3 is whats in my 06 TL currently. I'm needing an engine swap, my car has 311,000 milles and almost 150,000 on this engine. I'm going to purchase a j35a5 for now, to swap into the car while the j32a3 is out on the engine stand. The j35a5 I want to mill the heads down and spray 150-200 max after filing down the piston rings, but nitrous loves compression from what I understand. It's not like forced induction they say. My j32a3 runs in 91 octane and it's 11:1 compression. The j35a5 is stock @ 10:1 compression. I was going to try to get somewhere close to 12.3 or 12.5:1 compression and run 93 octane. Would I need a good tune for that? I have pre-cat deletes already(straight pipes cominig off the engine). Any info would be greatly appreicated. Def gonna check piston to valve clearance before assembly but I'd like to hear if anyone has raised compression and ran 93 octane in a J-series that is.

619rcr

Did you read any of the first post?

excerpts:

dallasstars

Oh damn, I completely missed that. Thanks man, a lot of valuable info but that guy went crazy and had to buy a new head and cams and dyno test and all that. I just want to make a simple adjustment and squeeze a little more compression out of it before I drop it in my Acura and then I might put a little spray on it. No cams and all that stuff. That thread is very very helpful. I didn't see where he said he was running 93 octane but I imagine @ 12:1 compression he is. He wasn't running E85 I don't think. I already have a nice exhaust and I might get the 3.7L intake if it's bigger than the j35a5 intake. Then just ported runners and a tune I guess is all I would need. Raising the compression should save me some more gas honestly. Sounds like cylinder heads milled 40 thousandths is where I'll find 12:1, I can deal with that. I think I'll get away with 93 octane on that. Thank you again for making sure I didn't miss that post. Totally didn't even see it and that's pretty much the answer to my question. lol

csmeance

With the stock compression ratio and 93 octane, I notice power being pulled in hot conditions in FL. Heat/detonation will be a large enemy with even higher compression. Without doing cams and other internal work, getting gains are not going to be really possible.

dallasstars

I see, I live in western Pennsylvania where its always freezing cold.(Except for 4 months out of the year. lol) But help me figure this out guys, I gotta swap engines. My engine is lagging coming up on 225,000 mi. I want to do something a little better than whats in there already. I know they sell pistons to make 12.3:1 compression for J-series. I was just thinking that maybe I could mill down the heads(reasonably, not past the service limit mark) to maybe get 12:1 or 12.3:1 comp out of it. Maybe swap in a j35 crank or j37 crank for a little extra umph. Not trying to go real crazy but I'd like to bump Comp ratio up a little, without a bunch of drastic things to do. I understand I can't mill the cyl. heads down too much because it will throw off timing from bank 1 to bank 2.(maybe adjustable timing gears??) I AM going to add a a little bit of spray later on down the road, and I already have pre-cat deletes and a J-pipe on the exhaust. Trying to be budget friendly here. Can i put a 3.7L crank in a j32a3 or just a 3.5L crank? Or I could just swap in a j35a5 and try to mill the heads down a little from there. I believe the j35a5 is 10:1 compression, the j32a3 is 11:1 compression. I feel like 12:1 on 93 octane in an all aluminum Honda is doable.

619rcr

You can do j35 or j37 crank with matching rods. Just know that j37 crank & rods with j32/35 89mm bore is 3.6L. Don't limit yourself to thinking compression is only achieved by milling the heads. Different pistons, crankshaft stroke, block machining and head gasket thickness also changes things around.
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To give you an example several years ago I built a roughly 11.2:1 static compression motor with +1mm oversized +10cc dome pistons, .004 shaved off the head, .004 shaved off the block, and thick .051 head gasket. It was tuned to run 100 shot of nos on pump 91 at 900ft elevation. But, now I live in a roughly 3k elevation environment and drive it NA only. I recently purchased a .040 head gasket, to bring it closer to 11.5:1 static compression. This should counteract some of the compression loss from the higher elevation.