Compression

[Christ]

K, so I'm building a D16A1... I'll use whatever stock parts I can, but I wanna make about 10.5:1 compression, w/o using a bunch of aftermarket parts... I don't plan on racing this engine, just street driving w/ more pep.. so what stock parts should I use?

I'll get the block/head milled IF I HAVE TO.. I'd rather not.

Also, what's the highest comp I can run on pump gas? (87/89 Octane) W/o hardcore ECU tuning?

[FrodoGT]

probably around 10.5

[Christ]

wow.. was that a typo? cuz that's perfect... Iwanna run 10.5:1

so any idea what parts I should use? I'll go hybrid if I have to, w/ B series pistons etc... I just dun wanna mill the block, other than boring it.. I wanna get a better r/s ratio too... and more low-end, so more displacement is necessary

[FrodoGT]

Yeha i mean the stock b16 runs 10.2, and ive seen people go higher, but it usually requires some tuning to get any longevity out of the engine on pump gas (91-93). I think if you can get it between 10.2 and 10.5 youll be fine. People go higher with stock parts all the time, i mean hell for like 30 bucks a piston you can get it to almost 12:1.

[Christ]

Can I mod the y8 head gasket to fit on the A1? I've been told (haven't actually looked, they're not in stock at local parts stores) that the only difference is one bolt... maybe the water/oil passages are off? I mean, if it's a pita, I won't use it.. but i dunno as yet.

k, question now... will it run (reliably) for at least 60k?

Tuning isn't really an issue, if by tuning we're talking about ECU tuning... I can do that... I can chip/serial my own ECU, I have a small laptop that's perfect w/ linux for Chrome software (or my own homebrew) so I can constantly monitor the ECU and sensors... I can keep hours of running tabs on the engine controls... etc. I can tune on the fly if I need to, although that will take significantly more work... no more money tho. I wanna have this engine built by spring tho... hopefully. Shit, actually, screw the laptop I have a cell phone w/ linux that's perfect for ECU management. I'm a hardware hacker... and I can build engines, but not for the best performance so far.. I've always been a turbo guy... I wanna build something all motor, and try my best to get great mileage doing it. (30+)

So... if I do the calculations to get 10.5:1 out of this engine, how hard will it be to tune it for 87 octane?

[FrodoGT]

Harder than 91 fo sho' lol

[Christ]

lol that doesn't tell me much... but thx for the help originally :P like I said, I'm picking up the motor at christmas weekend, and I'll be building it in the trunk of my car lol.. can't have it in the house, and dad's barn is too far away, so I'll pretty much be building it in the trunk.. so long as I don't really care about the interior, (I don't) of the trunk, I'll just be somewhat careful about getting oil and such all over it.

When the day comes to actually finish it, I'll be going back to my dad's house, b/c I plan on putting it in at the same time.

[kris]

Bore your cylinders .5 over, and use pm7/p29 pistons, leave the deck and head alone, and you'll be sitting pretty at 11.5:1 If you can really tune as well as you say you can, you should be fine on pump gas.

[turtlecrxsi]

Originally Posted by kris

Bore your cylinders .5 over, and use pm7/p29 pistons, leave the deck and head alone, and you'll be sitting pretty at 11.5:1 If you can really tune as well as you say you can, you should be fine on pump gas.

That's what my first d16a6 had done to it with some other goodies... until it blew up

[Christ]

Kris, are you sure about that comp ratio w/ stock rods and a 43.8cc head? That's what the A1's head is, I'm pretty sure... also, piston shape is a major concern for me... as I want the entire combustion mixture as close to the center of the chamber as possible, so either true flat tops (only valve reliefs, no dome) or a small dish in the middle from the valve reliefs in is necessary.

I'd like to achieve a combustion shape of a small football laying on it's side, if I can, as that will create optimal burn and the best natural detonation resistance (not taking into account the Octane of the fuel).

The basic idea here is to make as much power as possible in the 1-5k range... (normal driving) I don't care if the engine revs up to 8k or not... since it never goes there anyway. As a matter of fact, when I do the ECU, I'm setting the fuel cutoff @ 7k flat, b/c I can do 80 in 2nd gear @ 7k... that's plenty enough for a street car.

[kris]

If the A1 head is 43.8cc and not 38cc, then it will drop it to 9.3:1

[Christ]

yeah, see, therein lies the problem... it's 43.8 CC, and 212mm deck height.. I was thinking about seeing if I could use F series rods, to get the extra length, on a D16 crank, that also makes around 1.7:1 R/S, which is close to "optimal"

The F23A rods are 141mm, F20B rods are 145 mm... both BE bores are 48, and it's the same process for the wrist pins as the B16A rod mod..

That would get the piston back up there in the atmosphere somewhere... the next problem is adequate quench area, which the A1 really doesn't have... none of the DOHC D-series have it.. so head welding or milling is a necessity to get the "flat spots", then having/finding pistons that mirror those same spots to "push" the mixture into the center of the combustion chamber for "free octane" as it's commonly referred to... having the whole mixture densely compressed creates more detonation resistance... obviously.

To add to the troubles, I'm thinking about going w/ LP instead of Gas... since it's alternative and cleaner, not to mention cheaper in most cases, for automotive grade LP, and tends to net better overall economy/efficiency...

Lemme know what you think about all this... and any ideas you have are welcome, I'm not going to shoot anything down w/o checking it out first.

Same to anyone else, even if you're a newb.. sometimes a fresh idea is what's necessary to get the "wheels moving" on a project.