Ok the final figures have finally come in. After much debate about the whole Endyn drama, we've finally tabulated the true compression that we are running on our integra vs. the ADVERTISED compression that we originally purchased from Endyn.

Misc. info - using the Weisco part numbers for the pistons, we contacted Weisco and got the piston dome displacement figures from them for our application. We were assured that the part no coincide with the pistons sold to Larry from Endyn (small discrepencies may occur as Larry does final sanding of the piston dome, so final CR may be slightly affected).

Engine specs - B20B with ITR head, pistons are 0.005" in the hole, stock Honda headgasket, RW (advertized) 12:1cr pistons, stock ITR valves, head is NOT spot faced.

Here goes:

=============================================

Swept Volume - (84.5 / 2)^2 x pi x 89.0mm / 1000 x 4 = 1996.4263
Piston Dome Displacement - 7.4500cc x 4 = 29.8000
Combustion chamber volume - 42.7000 x 4 = 170.8000
Headgasket volume (incl. piston to deck height) - (84.5 / 2)^2 x pi x 0.8890 / 1000 x 4 = 19.9418 (0.030" + 0.005" = 0.8890mm)

Compression Ratio = (volume at BDC) / (volume at TDC) =

(Swept Volume - Piston Dome Displ. + Comb. Chamber volume + Headgasket volume (incl. piston to deck height)) / (Comb. Chamber volume + Headgasket volume (incl. piston to deck height) - Piston dome displacement)

= 2157.3681 / 160.9418 = 13.40145:1 Compression!!!!

=========================================

So there you have it. The pistons we purchased that were suppose to be 12:1cr are infact 13.40:1cr. No complaints however, as they definately perform as advertised. What is amazing though is that we are running 92-octane daily driven and it doesn't ping at all. Base timing is at 12deg BTDC.

Thought this would be worth mentioning.





[Modified by G3-TEG, 4:36 PM 10/26/2001]

 

interesting

 

So the chambers are not opened up to match the bore? Or are they?

Maybe Endyn quotes CR with the chambers opened up?

Its good that you got the results you were looking for (dyno wise)...but Id be upset if I didnt receive the pistons I ordered.

 

Will running 12 degree timing really hurt performance?
Will it be better to run 12.0CR but at let say 16 degree timing?

I always wonder what is the trade off between higher compression and retarded timing. Should I go higher compression but more retarded timing, or lower compression and higher timing?

 

I have the Endyn 81.5mm pistons in my ITR block with stock headgasket.

Will I be higher or lower CR than you?

I can't do math.

 

Ok, I'm bored, heres the math:

81.5 RW pistons in an LS/VTEC (itr head)

Swept Volume - 1857.1847
Piston Dome displacement - 29.8000

Everything else the same as above but 81.5mm bore.

2018.12 / 160.942 = 12.539:1 compression.

Keep in mind this is an LS block so it has 2mm higher stroke (89mm).

 

You bring up a very good point. I'm contemplating the same thing. Anyone have
any input on this?[


[Modified by G3-TEG, 5:26 PM 10/26/2001]

 

The significant figures in your equations are off.

-Kamil, who's taking the state EIt exam tomorrow and knows his sig figs.

 

yeah I do but I already stated it here:
http://ferrari.colowatch.com/php/sho...sb=5&o=0&part=
http://ferrari.colowatch.com/php/sho...sts&Main=33315


-----------------

sgt ran 17 degrees BTDC with 12.5:1 on a Bosch pump, I forget the injector sizing but I assume it was 310 cc/min and he was looking for 380's , and a J&S Safeguard.

I think it would be prudent to run 12 degrees BTDC timing as a starting point without a J&S Safeguard.

 

310cc rated at 43psi pushed to 65psi
J&S never picked up anything.
17 deg btdc

 

If you don't mind me asking, what was yoru target A/F ratio when you ran 17deg BTDC? Stock ITR ignition maps?

 

bah, im running the same **** with an ITR head milled 26 thou and i ping going up hill in 5th gear at 80mph on 95-96 octane mixture.


my guess was 12.6:1 compression on my build...but if you are right...what am i running like 14:1 now?

 

Whats your ignition map and target A/F look like? I spent a good 7-8hours on the dyno (Import Specialty Automotive - http://www.c-speedracing.com/isa.html) with Hondata.

It pinged prior to tuning on a stock JDM P30 map - 92 octane.

 

G3-TEG: A correction to be noted if you used an ITR head.

if you go to the Speedvision World Challenge GT website, they have specs in the rule book for the Integra Type R. The rule book has the stock specs the competitors must adhere to precisely or else they are penalised. The Type R head volume (Combustion Chamber Volume) is specified at 45.5 cc.

In the example you gave at Honda Tech.com, you actually used the b16a head volume of 42.7 cc I believe.

So if you were to recalculate your CR:

Compression Ratio = (Volume at BDC) / (Volume at TDC) =

[Swept Volume - Piston Dome Displ. + Comb. Chamber Volume + Headgasket Volume (including Piston to Deck Height)] / [Comb. Chamber Volume +
Headgasket Volume (including Piston to Deck Height Clearance) - Piston Dome Displacement]

The Parts:

Endyn RW High Compression Pistons: (Piston Dome Displacement +7.45 cc, bore 84.5mm)

B18C5 Head Volume 45.5 cc

B20b Block honed to 84.5mm bore, 89mm stroke

Deck Height : 0.127 mm (0.005")

Headgasket Thickness: 0.76 mm (0.030")

Metric Conversions:
1 inch = 25.4 mm

1mm = 0.1 cm

----

Swept Volume - [(84.5 x 84.5 x pi )/ 100] x (89/10) = 1996 cc

Piston Dome Displacement - +7.45 cc x 4 = 29.8 cc

Combustion Chamber Volume - 45.5 cc x 4 = 182 cc

Headgasket Volume (incl. piston to deck height) -
[(84.5 x 84.5 x pi) /100] x [(0.76 + 0.127) / 10] = 19.9 cc

Compression Ratio =

(1996 - 29.8 + 182 + 19.9) / (182 + 19.9 - 29.8)

= 2168.1 / 172.1 = 12.6:1 CR not 13.4:1

I put the method of calculation in our FAQ section at our website with a credit and thanks to you. I learned a lot by going through the exercise. Thanks for raising the issue.

cheers





[Modified by Michael Delaney, 1:53 AM 11/8/2001]

 

so smart mike, so smart.

 

He's like rainman.

Lets hit the blackjack table

 

I'll take those as backhanded compliments from the peanut gallery...

 

Mike D,
Always glad to see someone pays attention to detail. I would love to have you on my racing crew. keep up your good eyes
ADAM

 

I would imagine running higher compression by retarding the timing wouldn't gain any more power than the stock setup, maby less being that it takes more energy to compress the air/fuel that much more. But I don't know.

 

Thank you for double checking my calculations. However, can you please explain where the extra 2.8cc's comes from for the ITR head?

The B16A and B18C5 are exactly the same castings - PR3. The p/p of the ITR head is in the bowls therefore the combustion chambers are not touched. The only difference in the B16A and B18C5 head inside the chamber would be the intake valves themselves. Those alone would not account for 2.8cc's if any at all.

Pleaes double check the source of the information.

 

i just have a little questions.... i was wondering what the hell is going on with larry saying he have pistons thats 14:1 compression ratio for the public, which we can run 93 gas on those kind of compression??? is that really true? if it is how the hell would that work?

 

"Fast complete burn by pushing the mix exhaustward makes better thermodynamic efficency which makes power....forget CR it's a red herring. (I mean 17.4:1 CR in an all out race engine is not conventional or textbook is it?)"

"Compactness will influence the rate of burn. Taking the charcoal analogy, the tighter you pack it in, the more "contact area" you achieve. Naturally there will be a point by which you are packing it too tight and that I believe, will be influenced by other factors. If you don't use your squish area to confine the charge enough, you'll not be able to make the chamber work. In other words, there is a "best" size for any given shape and it's dependent on many things. But the key is the shape-size balance."

or check the article posted by michael delaney on TOO's site.


http://ferrari.colowatch.com/php/sho...sb=5&o=0&part=

 

I don't believe it is possable. Short of changing the chemical makeup of gas, or changing the laws of physics that is. Gas becomes unstable when you compress it. Theres no way to get around that without changing its makeup(adding octane).

 

i would also like to know where the 2.8cc's came from.. i've always known cc volume of b16 and itr's to be identical..

 

i beleive larry knows whats up, but some of the stuff he say it just hard to beleive.