Is there such thing as too high compression?

**ekslut** · 21-02-2005 05:17 PM

I have just got myself a B16A and coz I dont know how many km's it has done I am looking at rebuilding it now so I can get my engine reliable and I can trust it. When I rebuild it I want to do some mild power upgrades for now, and because of all the effort involved in changing pistons, I want to run some higher compression pistons now, so that in the future when I get some agressive cams (eg. Toda stage 2 or 3), my pistons will work perfectly with them.

So now my question is; On a stock or near stock setup, if I run high compression forged pistons (eg. 12:1) Will my engine cope with this or not? I plan on using a microtech to control it all.

**McChook** · 21-02-2005 05:51 PM

In short - ther eis such thing as too much compression, but 12:1 isn't a problem

Also - Toda Bs have the same low lobes as Toda Cs - Cs have the biggest VTEC lobe, so don't bother with Bs, its either As or Cs....

Take a few thou off the cylinder head when ya do the pistons, you'll get a bit more compression out of that. Cmopression is basically immediate horsepower.

Depending on how long you take, I'd get a Hondata S100 - for $350, they are the biggest bargain you'll get, and work just as well (if not better) than the mircotechs

The man to speak to BTW is Dyno Dave, and he lurks the forums, I am sure he'll see the thread shortly

**ProECU** · 21-02-2005 07:09 PM

you need to decide on cam selection prior to deciding on pistons & compression setups.

In a B16A, the swept volume is low, so to raise compression you need (this is a must) a large piston dome and low cylinder head cc volume.
As an example, 7.5cc piston dome & 41.7cc chamber with zero deck heaght clearance will net you 12.5-1 static CRatio.

Cam selection will govern valve relief depths and hence effect compression. Personally I disagree with McChook on the Cam issue. I'd stay away from C cams for that simple reason.

On the compression for a b16, the larger the dome needed to raise compression, the worse the flame propogation to the exhause valves. This also increases chances of pre-ignition. So you'll see, larger cams = larger dome for higher compression = not always a good thing.

Choose wisely, research properly before hand. Biggger isnt always better & JDM isnt always better.

Good luck

**BLKCRX** · 21-02-2005 07:23 PM

McChook hit it on the money... high comp 12.5 or 13:1 with a set of toda C's and it will be as good as you can get... piston design comes into the play also with regards to valve area and different manufactures have different valve seat area's... which is why some pistons are better than others…but you can also cheat and change the shape of your valves

Iv tuned many toda a's b's and c's on b16 b18 and b20's and the c's love compression. Remember boost on an engine is like increasing the compression

boost = power

compression = power

Its all about how its harnessed, designed and tuned.

PS remember how the engine built, tolerances and clearances and ring gap, along with many other factors can also make all the difference between a good and dud engine.

Regards James

**tinkerbell** · 21-02-2005 07:27 PM

if going B16A try to use a bigger bore (84mm) to improve the flame front problems of such small combustion chambers...

yeah, i agree with ProECU - B16A is not a good candidate for high compression work, B18C is good, but B20VTEC is better, if you are going to go to the trouble of building the bottom end, start with the biggest displacement you can

BTW - "reliable" and "high compression" usually dont go hand in hand with "I have just got myself a B16A"

**ProECU** · 21-02-2005 07:49 PM

Originally Posted by BLKCRX

boost = power
compression = power
Regards James

James, its not boost that makes power dude.

Why do u think turbos make less gains as psi increases? Think about that one and post back.

In any event, I wouldnt go much past 13-1 CR on our street fuel for daily use.

**BLKCRX** · 21-02-2005 08:00 PM

Boost does make power

its compressed air, but like everything there are rules regulations, limitations and efficiency. But this isn’t a boosted questioned.

Back to NA

13:1 (Ish!!!!!!! ) is great fun on the street for a built NA car, but good fuel and a careful driver who doesn’t go around trashing his car on the street is a must also.

Regards James

**ekslut** · 21-02-2005 08:29 PM

hmmm...many things to think about. By the way I forgot to mention, this car is mainly going to be used on track (sprints and the such). It will not be a street car and about all the street use it will see is the trip to PI, Winton, or Sandown.

But from the sounds of things running some higher comp pistons with near standard internals should be fine, if I choose to do that. But when I do upgrade Toda C's are the cams to use?

I would like to stay 1600cc's so when I go to track I can stay in the under 1600cc class, so increasing to 1800 or B20VTEC is out of the question.

Im mainly at the moment trying to get the engine in good condition so I can trust it and it be reliable. But I dont like doing things twice. So thats why I want to try and get the bottom end sorted now while I am rebuilding it, and when I have a bit more cash in about 6 - 12 months, then get the good cams/cam gear/valve springs/retainers.

I am just trying to work out which pistons I should use. Like what compression, size, and brand. Just trying to learn as much as possible so I can make the best decision that I can.

**PhatSol** · 21-02-2005 11:14 PM

Originally Posted by BLKCRX

...and a careful driver who doesn’t go around trashing his car on the street is a must also.

Just curious, what is the diffrence between hard street use and hard track use? I thought the track work would be tougher on the car than any street driving?

**pgclee** · 22-02-2005 02:59 AM

street use - Do not always trash your car

Track use - Always Hit's the rev limits...

haha...!

13.1:1 compression is too high to any street car...High compression doesn't mean that your car will be freakin fast as well...The Figure is impressive, but it's all up to the Final tuning...i use to have 13.1:1 compression and droped to 12.5:1 compression...at least it sound MORE LIKE a normal car....muahahaha...

**tinkerbell** · 22-02-2005 09:19 AM

Originally Posted by ekslut

But from the sounds of things running some higher comp pistons with near standard internals should be fine, if I choose to do that. But when I do upgrade Toda C's are the cams to use?

i am sorry, i dont understand what this means?!?

if you change the pistons you are changing the internals.

the pistons ARE part of the internals.

**BLKCRX** · 22-02-2005 09:26 AM

If you wanta stay 1600cc, stick with the 81mm bore or 81.5 ( after u hone the block for new pistons )
Chuck in a set of eagle rods.... not the worlds greatest rod's but they will hold 9500rpm and rev all day if installed correctly...and there better than stock. Use correct sized bearings and a good machine shop who builds Honda engines and you should be sweet.

See if the rules and regulations tell you which fuel you can use.. I know all the GTP car's that I tune that race on TV in the Pro Car series last year all had to use BP ultimate fuel.... but also in the GTP your not allowed 2 hardly modify anything...apart from ECU/Intake/Exhaust but if your allowed 2 use lets say ELF-LMS or Sunoco supreme fuel then look for 13.5+ comp ratio.

Springs and Retainers = Toda
Cam Gears = Toda
Cams = Toda

Talk to Adrian from Advan in Sydney/Silverwater for all your Toda equipment, he might be a little more expensive than importing your self, but you get local support and help support the local Australia industry !!

Should be a nice fast rev’ing engine, might also pay to play with fhy wheel combo’s and harmonic balancer to help the engine rev, along with a nice intake setup / exhaust setup.

Long live the b16 engine

I love my 400kw+ b16 engine

Regards James