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Discussion Starter #1
ive started a new build. and have a few questions on compression for the power i wanna make.
first of all im finding it hard to find a set of pistons in the compression area that i want.
im wanting either 9.5:1 or 10:1 but seem to only be finding 9:1 and 10.5:1
ive emailed arias to see what they have or can do for me.

now is 10.5:1 to much?
it will be going in a darton sleeved block and the goal is to hit the 600whp mark with a PTE 6262.
i have a good flowing head with stock sized valves aswell.
im just not wanting super low compression like my vitara build which obv it wont be near that with any normal forged piston. but i pulled the 8.5:1 pistons out because i didnt want that low in this build.

any info would be great from the guys that are in this territory.
 

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Considering people boost Type-R engines everyday should say something since there well over 10:5:1 comp.

Tune and Tune and there are people running comps in the 12s without issues.

How solid your bottom end and what kind of tune/tuner you have will dictate how much comp you could push out of it in the long run.
 

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Discussion Starter #3
Considering people boost Type-R engines everyday should say something since there well over 10:5:1 comp.

Tune and Tune and there are people running comps in the 12s without issues.

How solid your bottom end and what kind of tune/tuner you have will dictate how much comp you could push out of it in the long run.
yeah but the type r motors prolly arent at 30psi on a larger turbo either.
i have great trust in the tuner but dont want to choose a high compression that will hurt me in the long run
 

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yeah but the type r motors prolly arent at 30psi on a larger turbo either.
i have great trust in the tuner but dont want to choose a high compression that will hurt me in the long run
Like I said stock bottom end will not hold as much boost.

And know matter what a low comp engine in the long run will be able to handle alot more boost with lets say the same Turbo is on the same engine with the same set-ups, one built high comp the other built with low comp.
 

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my dd has 1800 ftlbs of torque
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what bout 10.5 comp with thicker hg
or 9.1 with shaved head giggity
 

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Discussion Starter #8 (Edited)
u want 600whp on a SOHC? go big or go home

its not like ur gonna run the vehicle on pump gas, so the skys the limit
very well put danz.
it will be on 118oct so i mine as well get the 10.5:1?

and instead of making another thread.
what would be a good P2W clearance on these?
 

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If you go 10.5 with a big turbo pumping a lot of air, you will need a real good inter cooler and real good fuel to avoid detonation.

Personally I would run the lower comp pistons then deck the block and shave the head to get good quench pads and tight piston to head, like maybe 0.030" piston to head. What comp would that give you.

You also need to find out what piston to valve you will get as that might require notching the pistons for valve clearance.

Also if you have a good port job, probably the chambers where opened up a bit and that loses a bit of comp.

Bottom line, you need to know chamber ccs for your head as modified and effective dome size of pistons after valve notches made right.

Then do the sums to see which dome suits and if the supplier can tweak that for you at a reasonable cost.

10:1, cool IAT, good quench and 118 octane should be good I think.

It also depends on the cam a lot. Do you know where the inlet valve closes.
 

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Discussion Starter #10
If you go 10.5 with a big turbo pumping a lot of air, you will need a real good inter cooler and real good fuel to avoid detonation.

Personally I would run the lower comp pistons then deck the block and shave the head to get good quench pads and tight piston to head, like maybe 0.030" piston to head. What comp would that give you.

You also need to find out what piston to valve you will get as that might require notching the pistons for valve clearance.

Also if you have a good port job, probably the chambers where opened up a bit and that loses a bit of comp.

Bottom line, you need to know chamber ccs for your head as modified and effective dome size of pistons after valve notches made right.

Then do the sums to see which dome suits and if the supplier can tweak that for you at a reasonable cost.

10:1, cool IAT, good quench and 118 octane should be good I think.

It also depends on the cam a lot. Do you know where the inlet valve closes.
oh goodness.
i do not know where the inlet valve closes.
i am running the 59500 cam. in a y8 head. with y8 gear that is adjusted to correct the timing with the z6 cam in the y8 head.
i am running a go-autoworks FMIC its pretty big and did great with the last setup. while tuning on a mid 80 degree day IAT never got over 100 degrees.

a lot of what your talking about is way more technical then i can understand to be honest. but your saying i shouldnt go 10.5:1 and go ahead and run 10:1 compression?
 

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Discussion Starter #12
This is similar to my build i have 10:1 wisecos if you google d16 flat tops you will see a site selling them
thanks man.
so i know they make them for sure now. but i will only order from a site sponser on here.
 

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The later the inlet valve closes, the less the charge is compressed as the piston is further up the bore when compression starts.

I looked for a couple of hours but I can't find specs on that cam.

You can measure with a degree wheel and a feeler gauge.

Set the degree wheel and pointer to TDC, turn the engine, when the valve lash is slack put a very thin feeler gauge into the #1 inlet valve gap, turn the engine in direction of rotation until the rocker arm jambs the feeler gauge, keepturning until the rocker arm starts to lose its grip and you can pull the feeler gauge with a bit of a tug. Read the degree wheel for intake closing point, well really a degree or two after it.

The later the inlet valve closes, the more compression you can get away with, all other things being equal.
 

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With what I think is probably a big cam, 118 octane and what has shown to be a real good inter cooler, I think you will get away with 10.5
 

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The 59500 cam isn't really all that huge. It's around the same size of a delta 272 cam from what I know of them. I believe it has more intake duration than exhaust duration and a lift of .450?? . A bisi special grind (3.6 or bigger) would proably suite you better. Your going to have crazy high dynamic pressures all at once with that cam/compression/turbo.
 

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I'm surprised that nobody has asked this yet, but what is this car going to be used for? I'm assuming it's going to be a drag-only car since 600whp is pretty impractical for street use.

If that's the case, you'll be able to make more power with less compression and more boost. Without getting too technical, this approach gives you more control over the cylinder pressure characteristics of the engine so you can deter knocking better than you could with a high-compression setup. However, you will have a very peaky torque curve that will probably suck for getting groceries.
 
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