N/A to FI: AFAccord's 10:1 Comp Turbo F23 Build Thread/Restoration

Sonnick

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9.5 CR sounds good. I've even seen people going 10:1 and just using less boost. I know this has been shunned previously, but I heard that it's more efficient to have a decent piston CR while using less boost. You are getting all forged parts, so I'm under the impression that they will hold most of what you can throw at it. Plus, you're not looking to make 700whp. With some nice lift on the turbo cam, (Bisi has one cut for turbo btw, I believe it's Level 2.1 but you probably already know that) 9.5 or 10:1 and 6-7lbs I could see you making 240-250 for your 'low boost' setting, and 300+ on 10-12lbs of boost.
 

AFAccord

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Yeah, it all depends on the turbo size I go with, but with a higher static compression, I shouldn't have to throw too much boost at it to get the results I want. Many people don't realize that it's Honda's well designed combustion chambers and quench areas that let us run higher static compression and more timing than other manufacturers. That's why you see so many 11 and 12+ compression boosted K-series guys running around with very little problem.

I've done lots of research into Bisi's turbo cams recently, but have yet to call him. Originally, his only available turbo cam (1.2) wasn't worth it's weight, but his 2.4 and 3.6 cams are now the best performing turbo cams out there.

My original goals were based upon using stock F23 rods, but now I might ask a bit more out of it for high boost. Once it's well broken in, I might like to hit a little over 400whp on the dyno, then back it down to 360 or so for my high boost setting. :)
 
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AFAccord

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Today while perusing the forums, I came across an interesting theorem from a respected SOHC mind regarding the effects of static compression in a forced induction build. Have a look if you don't mind the read.

In order to even begin a proper discusion of this topic, there are some basics that need to be understood and some other concepts that need to be squashed because they just make you sound like an idiot. (You being generally plural, not you specifically, OP.)

Firstly, what engines are we going to talk about? All engines? An "Ideal" engine? D-series? B? K? Ford SVO? BMW F1?

Secondly, let us dispense with the term "boost." It means jack all scientifically and only confuses several well defined scientific concepts that you should be learning in order to make heads and tails of what is actually going on in a turbocharged internal combustion reciprocating piston engine. Instead of "boost" we need to use terms like pressure (relative or absolute!) and CFM, as those two things are interelated but dependant on the size of the compressor of a turbocharger in use on the engine.

Thirdly, "high" and "low" compression are relative terms, and until someone states what the mid-point is, we are just being vague which further clouds discussion. Also, one has to consider the effects of the entire induction system and intake cycle in order to account for at least some of the factors pertaining to what is more commonly known as dynamic compression ratio, and much more specifically related to as Volumetric Efficiency (VE). For example, I think anything under 10:1 SCR (S being Static) is low. Some think that is way too high for any seriously boosted engine. I think anything lower in most cases is criminally insane.

Fourth, let us realize that almost all of this discussion is going to have to be theoretical. None of us have the money to build two engines almost identically or at the very least use two sets of custom pistons and a lot of dyno time in order to settle a lot of this in an engine format that we are familiar enough with to be satisfied with the results. The difficulty of this test is how to create a combustion chamber design that is easily manipulated into having vastly different compression ratios while still maintaining equivalent quench properties so that the effects of quench are not mistaken for the effects of combustion chamber volume in the same style of engine. To this end, I would propose actually using a Y8 head for experimentation. I dislike the ports, but, that is mostly irrelavent to our inquiries. (I just know someone is gonna say "hey, I thought you didn't like the Y8 head.") I think this head is ideal because it exhibits very good inherent quench, a compact, efficient combustion chamber, and will make a very good top side for our combustoin chamber. Having built in quench pads in a stock head also allows us to change the volume of the chamber very significantly while still maintaining very good, consistent quench pads on the pistons. Many would suggest using vitaras as a test base, but, if we were to conduct these tests scientifically, we would need a custom piston built to match the Vitara's quench pads with a much smaller dish, or possibly even a flat piston. It would be better, scientificly, to have two sets of custom, forged pistons made, from the same materials and with the same quench pad configurations. This would eliminate any material differences and possible effects of heat transfer and possible tuning differences based on non-consitent material and piston design. The pistons would be made to have a compression height equal to the deck, and a stock MLS headgasket would be used in both builds to ensure consistent quench distance, thus keeping squish very consistent. The rest of the engines would be blueprinted to the same speficications. Now, we'd have two engines build as similarly as possible with almost all characteristics of them being exactly the same except for the dish of the pistons, and, necessarily, the piston weight, though the weight would have an almost negligable effect on the results of testing. The engines would then be installed into an engine dyno, broken in and tuned using the same absolute pressure (very important as I will explain later) and same BSFC (if possible, and further explaination to follow). Tuning to the same PSI is almost correct, and tuning to the same AFR would cover up some very fundemental differences. Doing things this way at first would show us the characteristics of the combustion chamber itself, it's effect on how it spools the turboand how much power is made where in the working range of the engin. After this is done, each engine would then be tuned to it's own maximum potential, regardless of absolute pressure and BSFC, until the engine is destroyed. (I told you this would be expensive.) This should show the limit of the larger and small chambers and give us a very good idea of some general parameters that can be applied to "large chamber" builds and "small chamber" builds.

Issues with this test:
1. Cam. Finding a cam (or cams) that will provide a wide powerband (I would suggest from 2500-9000RPM) is difficult. I would suggest a Bisimoto 2.x or 3.x cam. I am sure Bisi would love to help out with something like this.
2. Turbo. Finding a turbo that can stretch the limits of a custom build and yet still spool earlier enough to help determine the effects of compression on spooling a turbo.
3. Manifold. There aren't many manifolds on the market that I particularly like. I would suggest having Bisi design a custom piece and then having two made. Bisi and John at Hytech are the only two people I know of that could handle that kind of thing. I would rather not have to run into a manifold limiting the engines, and I certainly don't know enough to design something like that.

My suppositions based on what I have researched:
The "small chamber" engine will produce more power everywhere, spool the turbo faster, and accelerate faster than the large chamber head, up to a point where the chamber reaches maximum capacity, and cannot be filled anymore, providing an actual limit to how much A/F mix can be burned, and therefore imposing a power limit for whatever fuel is chosen for the test. Various fuels could be used in the test before the final maximum power tests in order to find a fuel that would best showcase the chamber. (I don't care what fuel it is, and would take some testing. Or we could choose something commonly available and go with that as a standard, but then we might run into an octane limit, not a chamber limit. Even though the chambers will have very good quench, pump gas may not actually allow for a full testing of the chambers' limits.)

Once the small chamber's physical limits are reach, so that no matter how much the pressure is turned up, the engine won't fit any more air/fuel, the large chamber will start to shine. It will be able to engulf more mix, and thus, make more power. However, the difference in chamber volume will make it accelerate slower at lower RPMs and higher towards the end of the engine's working range.

It is also my belief that the smaller chamber will "work better" on pump fuels, meaning that the engine will accelerate faster at all RPMs as the engine will produce much more average torque and will require less time to fill the engine. Also, I predict that the smaller chamber engine will exhibit lower BSFC, meaning it will be overall more efficient. This will be better for any kind of car driven on the street. (My opinion.)

The larger chamber engine will most certainly be better for drag racing and highway pulls. It will be less efficient, and not accelerate as well until later in the engine's working range.

Then we can further complicate things like trying to pair a large chamber engine with a smaller turbo, a small chamber engine with a larger turbo, etc. But, we don't have the money to do any of this stuff, so, IONO. It's fun to think about and discuss, but hard to determine.


There's always the possibility that I have interpreted this completely wrong, but what I gathered from reading over this post a few times, is that my previously stated philosophy (albiet somewhat ignorant and lacking in supporting factual information) on compression and boost might not be so far from the truth.

IMO, going down to 9 flat from stock would provide no perceptible benefits to tuning, and going any lower (8.5 or less) is only ideal for a car that sees high rpms and lots of boost from a large compressor.

...this is just my opinion as to what is necessary for a fun, reliable street car. Ideally, I think Bisi's longer rods (better r/s) and an 8.8 piston would be awesome to throw lots of boost at and spin up to 8k...

...Since I don't plan to run the engine up to maybe 6500rpm, I'll gladly take a bit more compression to provide a little more low-end and responsiveness. :driving:

I guess we'll see how this all pans out once everything is assembled and tuned...:boink:
 

AFAccord

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I want to remove most of the vacuum nipples from my F23 IM, just to clean up things since I will be using a vacuum manifold. So I picked up a few 5/16" stainless plugs, a 5/16" tap and a titanium 17/64" drill bit over my lunch break. Hopefully tonight I'll have an opportunity to cut off one of them nipples, drill, tap and plug it. If all goes well, I'll do the rest, though I'm sure I'll need at least one larger plug and tap, maybe two for the larger connections. The only connections I think I'll need is the brake booster and a small outlet for the boost/vac gauge. Everything else should be able to route off the vacuum manifold, unless I'm forgetting something that needs to see boost.

photo1-1.jpg
 

Russianred

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Blow-off Valve ;) But it's not necessary to have it on the IM. If you use an electronic boost controller such as greddy, the vacuum line off it needs to see boost at the IM. In this case, not the boost controlling system itself, but the additional vacuum line off the unit which is T-ed in to the fuel pressure regulator vacuum line, which essentially ends up at the IM.

But awesome idea bro, I plan to do the same, probably going to ask you later for where you got the plugs!
 
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x5carl3tMurd3rx

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your right to assume that a higher compression turbo build will make more efficient power because it will. the main reason people go low compression is because unless you have a good tuner a high SCR engine that will see boost will also need to see a higher octane fuel that may not be readily available. Plus the everyday forum taught enthusiasts are usually scared of the idea of a high SCR turbo build cause 90% of people on forums say that its a bad thing.
 

Russianred

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:147703263745b138a51

Looks great bro.

In the second pic, are you tuning out that little valve that's mounted on the plenum and going in to the port you blocked off? What's it for anyways? I know it's part of the EVAP system, but what exactly does it do and what happens if you delete it?

:hide:

Where did you get those plugs too - locally?
 
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x5carl3tMurd3rx

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damn that looks clean. Quality work man. I dunno why I haven't already but I'm subscribing to this ****. Really excited to see the outcome of this.
 
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