F23 NA build

[Jarrett]

OK, this is just me posting about a possible setup that I gathered from PirateMcFred's setup on H-T. Correct me if I'm wrong but his setup used H-series pistons on a F23 rotating assembly and had to do serious modification to the combustion chamber in order to clear the additional 0.040" of compression height of the piston. Now, others on that forum talk about the ability to use K-series and F20C pistons on top of the F23 rotating assemblies because both of them incorporate the same compression height. So it would seem an easy choice from here for those who want to do an F23 build to chose the pistons with the compression ratio they wanted. Only I'm almost positive that the F23 and K20/F20C don't share the same combustion chamber volume. Does anyone know what this value is?

Basically, here is my interest in this swap:
It's a cheaper engine to begin with than H22
It has VTEC
It has the ability to easily accept an H22 head later down the road

I'm not going to argue that it's better in such and such aspects, blah, blah. that's all driving styles and application hooplah. I do think this could be the basis for a cheap swap that allowed the user to run very high compression(due to the selection of aftermarket K20/F20C pistons), and the biggest selling point, the ability to easily accept an H22 head later down the road.

Where are my flaws in this design? I know there's got to be some. For instance a new header purchase would be a necessity. I also have no idea about the IACV/FIV/or MAP sensor mounting on this intake. Would it just be a rewiring issue. As far as OBD-1 converting goes, reuse your F22 distributor and run a remapped P28. I'm probably not going to attempt this anytime soon unless I accidentally happen upon an F23 VTEC so basically this is just to keep it going between me and Glory. Your move.

[HondaFan81]

Hit me on AIM (Accord EX SE) if you want to throw around different engine combinations. I would need info on the F20C/K20 engine from you as I don't have that, nor have cared to find out just yet.

Also, why do you care about combustion chamber volume...or are you more interested in valve clearance and piston-to-head clearance issues?? If you indeed care about combustion chamber volume, then you are indirectly saying you are worried about compression ratio...is this really the case?

[Jarrett]

I wanted the combustion chamber volume just to know the exact compression ratio. The K20/F20C pistons advertise their compression ratios based on the K20/F20C combustion chamber volume and stroke. Both of those values are changed and that compression ratio number no longer has any validity in this setup. Not worried though. Just want to know because if I were to tune around a certain compression ratio, I'd need to know what that was.

[gloryaccordy]

The "VTEC" on the F23 doesn't really count IMO...I think they shut down one of the 2 cylinder valves for better fuel economy.

That said, the best and easiest route is probably just getting custom pistons made. I'm not even sure companies do regrinds on those cams (although I don't see why they wouldn't). I think an H23 with a milled head, cams and cam gears would give you the best non-H22 run for your money. Find some 88+mm pistons and you'll be even more in the money. Good luck with whatever route you choose.

[uslspct]

Forget the F23 head. But I think I'm might go with the F23 bottom end.
I wouldn't consider what he did to make the pistons fit serious modifications. His build was exactly the budget build we need around here. Less money than a H22 swap and more power. But I read more about the K20 pistons at one point and I believe somone said they wouldn't fit, I don't remember why and I can't find that post right now. But here's a guy with RSX pistons in a F22 bottom end with a H22 head click me fucker! So...

Look at his dynos comparing to other setups. His powerband is awesome. Here's a quote from him "The Hybrid curve is almost parallel to a stock h23 just about 20ft/lbs and 20whp more across the board."
And another that sums up everything: "But in all honesty the way I built my bottom end is, of course, less than ideal. I took calculated risks when using parts that I had lying around. I could have sprung for custom forged pistons and put them in the stock F23 block to get 12:1 CR but I got the same compression with a bore and hone and some H22 pistons. I am not necessarily advocating building your only form of transportation EXACTLY the way I did, 12:1 CR is not for everyone, but at least knowing that you have options is nice.
Mainly I posted this build and dyno to show that you can take your F motor and swap a more aftermarket friendly/higher performance head for rather cheap and with elevated compression and minor bolt-ons that you can not only make power, but actually compete with H22 swapped cars."
Brilliant!

So, I think I'm going with the f23 bottom end for the longest stroke possible. And figure out a way to rev a little past redline. If 2point6 can rev his bottom end H22 with a 98mm stroke, why not the F23. More research here I come...

And I've accepted that unless I go with the H22 head, a custom header will have to be made.

[gloryaccordy]

The main, if only issue with revving an F like an H is the rod bearing issue. Here's my theory as to why they spin...you rev the F higher, there's more side to side loading. Eventually, if you spin the assembly fast enough, the side load gets to the point that it overcomes the oil that's supposed to be there, and the rod basically "grabs" the crank, making the bearings come off the rod/cap...plus since the F cranks aren't as balanced they flex/vibrate more...

I guess if you can get the crank knife edged, but more importantly BALANCED there shouldn't be a problem. You are going to be cutting it very close though if you plan to run to 8000RPM regularly. I think the engine with the highest piston speeds on the market is the M3 motor...and that has an 87x91mm bore x stroke. The piston speeds at 8,000RPM on a 97mm crank will be in the F1 league...get some good bearings, a heavy duty oil pump, baffled oil pan and pray for the best...

[Jarrett]

If such is true about the F23 head then I gues that is not a viable option. But I can get an F23 bottom end and do the same and instead of swapping it and waiting for a H22 head, I could just keep it in the garage. So I guess I'm stock for a little longer.

Uslspct, in your post you say the guy has a K20 pistons in a F22 bottom end. He actually has an F23 bottom end, which is what I would want to run. And as far as revving it that high, as Glory pointed out, the two weak links are going to be rods and bearing oiling. Aftermarket forged rods(if available) and a TOGA oil pump should fix this issue though.

Cisco, I still haven't found the combustion chamber volumes that I was looking for but I'll let you know when I do.

[gloryaccordy]

It's not the rods themselves, it's the rod bearings. Perhaps lightweight rods and pistons will help fix that...

[uslspct]

I believe the K20 CC volume is the same or very close to the same as the F22. But those pistons are for 11:0, pirate dropped in 10:0 pistons and still had a crazy high comp ratio.
And of course I would use stronger and hopefully lighter weight pistons and rods. But the rod bearings are smaller than the rest.
Edit: You're right. When you stair at numbers and letters all day they start to blur. So it can be done then.

[Jarrett]

They wouldn't work because they would smack the head. The compression height is too tall for a H22 piston on F23 rotating assembly to work properly. Hence K20/F20C pistons which share the same compression height.

Glory, I've talked to amny F23 owners who feel the rods are a weak link in their bottom ends. There are substantially thinner than all other F/H rods, thus less clamping for on the bearing(also due to a short diameter as well). If it weren't for the rod, the bearing wouldn't be a problem. And even still, it's not really a problem per se. Just something keeping you from revving the car to high heaven.

[westsideaccord]

first off I have an f23 with bad bearing(s) lol got it for free from a friends 99 or 2000 accord dont remember, the engine sits in the trunk of my parts car!
Secondly, I thought the single cam v-tec was still vtec, just not DOHC so it doesnt provide the same power!?? I will find a link on vtec soch, dohc vtec and I-vtec one moment!

[uslspct]

Allright now figure out if F20B pistons will go in the F22 bottom end. A slightly different comp height, but less so than the h22a4 pistons in f23. I believe the piston dome should be the same as 11:0 prelude pistons. But what about using a thicker headgasket to correct any part of the piston getting to close to the head? Or messing with the F22 CC like Pirate did to make his h22a4 pistons work. And I think one number is off on the F20B specs, because I calculate it to be .02" out of the head. Rod length must not be 5.709"

[westsideaccord]

This is from Wikipedia.org not me lol! (EDITED)

VTEC (standing for Variable valve Timing and lift Electronic Control) is a system developed by Honda Motor Co., Ltd. to improve the combustion efficiency of its internal combustion engines throughout the RPM range. This was the first system of its kind and eventually led to different types of variable valve timing and lift control systems that were later designed by other manufacturers (ie. VVT-i from Toyota or VANOS from BMW)
Introduction to VTEC
In the regular four-stroke automobile engine, the intake and exhaust valves are actuated by lobes on a camshaft. The shape of the lobes determines the timing, lift and duration of each valve. Timing refers to when a valve is opened or closed with respect to the combustion cycle. Lift refers to how much the valve is opened. Duration refers to how long the valve is kept open. Due to the behavior of the gases (air and fuel mixture) before and after combustion, which have physical limitations on their flow, as well as their interaction with the ignition spark, the optimal valve timing, lift and duration settings under low RPM engine operations are very different from those under high RPM. Optimal low RPM valve timing, lift and duration settings would result in insufficient fuel and air at high rpm, thus greatly limiting engine power output. Conversely, optimal high rpm valve timing, lift and duration settings would result in very rough low RPM operation and difficult idling. The ideal engine would have fully variable valve timing, lift and duration, in which the valves would always open at exactly the right point, lift high enough & stay open just the right amount of time for the engine speed in use.

In practice, such a perfectly adjustable system is complex and expensive to implement and is therefore found only in costly experimental and limited production engines. The vast majority of modern automobile engines operate with a fixed camshaft profile that represents a compromise between low RPM smoothness and high RPM power output. And since the average automobile engine spends most of its time running in the low RPM region, there is typically more emphasis on low RPM smoothness at the expense of high RPM output. Performance-tuned engines have cam profiles that are optimized more towards high RPM operation, where the greatest power can be obtained. But this means that low speed operation is compromised. Anyone who has heard a racing car or a highly-tuned hot rod sitting at idle will note that the engine sounds like it is barely capable of running at that speed.

DOHC VTEC
Honda's VTEC system is a simple and fairly elegant method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations. Instead of only one cam lobe actuating each valve, there are two - one optimized for low RPM smoothness & fuel efficiency and one to maximize high RPM power output. Switching between the two cam lobes is controlled by the engine's management computer. As engine RPM increases, a locking pin is pushed by oil pressure to bind the high RPM cam follower for operation. From this point on, the valve opens and closes according to the high-speed profile, which opens the valve further and for a longer time. The VTEC system was originally introduced as a DOHC system in the 1989 Honda Integra sold in Japan, which used a 160 hp (119 kW) variant of the B16A engine. The US market saw the first VTEC system with the introduction of the 1990 Acura NSX, which used a DOHC V6. The DOHC VTEC system has high and low RPM cam lobe profiles on both the intake and exhaust valve camshafts. This resulted in the most power gain at high RPMs and DOHC VTEC engines were thus used in the highest performance Honda automobiles. In contrast to the SOHC implementation which switches between cam profiles seamlessly, when the DOHC version switches cams there is a definite change in the engine note.

[edit]
SOHC VTEC
As popularity and marketing value of the VTEC system grew, Honda applied the system to SOHC engines, which shares a common camshaft for both intake and exhaust valves. The trade-off is that SOHC engines only benefit from the VTEC mechanism on the intake valves. This is because in the SOHC engine, the spark plugs need to be inserted at an angle to clear the camshaft, and in the SOHC motor, the spark plug tubes are situated between the two exhaust valves, making VTEC on the exhaust impossible.

[edit]
SOHC VTEC-E
Honda's next version of VTEC, VTEC-E, was used in a slightly different way; instead of optimising performance at high RPMs, it was used to increase efficiency at low RPMs. At low RPMs, only one of the two intake valves is allowed to open, increasing the fuel/air mixture's swirl in the cylinder and thus allowing a very lean mixture to be used. As the engine's speed increases, both valves are needed to supply sufficient mixture, and thus a sliding pin as in the regular VTEC is used to connect both valves together and start the second one moving too.

In North American markets, VTEC-E can be found in Honda's most fuel efficient cars, including the 1992-1995 Civic VX and 1996-2000 Civic HX.

[edit]
3-Stage VTEC
Honda also introduced a 3-stage VTEC system in select markets, which combines the features of both SOHC VTEC and SOHC VTEC-E. At low speeds, only one intake valve is used. At medium speeds, two are used. At high speeds, the engine switches to a high-speed cam profile as in regular VTEC. Thus, both low-speed economy and high-speed efficiency and power are improved.

[edit]
i-VTEC
i-VTEC introduced continuously variable camshaft phasing on the intake cam of DOHC VTEC engines. The technology first appeared on Honda's K-series four cylinder engine family in 2002. Valve lift and duration are still limited to distinct low and high rpm profiles, but the intake camshaft is now capable of advancing between 25 and 50 degrees (depending upon engine configuration) during operation. Phase changes are implemented by a computer controlled, oil driven adjustable cam gear. Phasing is determined by a combination of engine load and rpm, ranging from fully retarded at idle to maximum advance at full throttle and low rpms. The effect is further optimization of torque output, especially at low and midrange RPMs.

In 2004, Honda introduced an i-VTEC V6 (an update of the venerable J-series), but in this case, i-VTEC had nothing do to with cam phasing. Instead, i-VTEC referred to Honda's cylinder deactivation technology which closes the valves on one bank of (3) cylinders during light load and low speed (below 80 mph) operation. The technology was originally introduced to the US on the Honda Odyssey, and can now be found on the Honda Accord Hybrid and the 2006 Honda Pilot. An additional version of i-VTEC was introduced on the 2006 Honda Civic's R-series four cylinder engine. This implementation uses very small valve lifts at low rpm and light loads, in combination with large throttle openings (modulated by a drive-by-wire throttle system), to improve fuel economy by reducing pumping losses.

With the continued introduction of vastly different i-VTEC systems, one may assume that the term is now a catch all for creative valve control technologies from Honda.

[Jarrett]

Allright now figure out if F20B pistons will go in the F22 bottom end. A slightly different comp height, but less so than the h22a4 pistons in f23. I believe the piston dome should be the same as 11:0 prelude pistons. But what about using a thicker headgasket to correct any part of the piston getting to close to the head? Or messing with the F22 CC like Pirate did to make his h22a4 pistons work. And I think one number is off on the F20B specs, because I calculate it to be .02" out of the head. Rod length must not be 5.709"

If you want factory pistons on an F22 bottom end, I've been looking into H22 pistons on this setup. I think my research and math indicates that it should be fine to clear the head. An H22 block would have to be used to to an 87mm bore. A resleeved F22 block could be used but that no longer respects the boundaries of a budget. As far as user a thicker headgasket to clear pistons, what's the point of bumping up compression only to lower it? And also about messing with the combustion chamber to fit a certain piston, the whole point of this project is to rebuild an engine with all factory parts so it stays cheap. That sir, isn't. And also in regards to the F20B rod. It is in fact 5.709". The compression height on that same piston is equal to that of the H22 as well so basically it's an 85mm bore version of the H22 piston. I suppose you could use F20B pistons(good luck finding those) on a F22 bottom end in a F22 block and still have a 2.2L.

[uslspct]

If you want factory pistons on an F22 bottom end, I've been looking into H22 pistons on this setup. I think my research and math indicates that it should be fine to clear the head. An H22 block would have to be used to to an 87mm bore. A resleeved F22 block could be used but that no longer respects the boundaries of a budget. As far as user a thicker headgasket to clear pistons, what's the point of bumping up compression only to lower it? And also about messing with the combustion chamber to fit a certain piston, the whole point of this project is to rebuild an engine with all factory parts so it stays cheap. That sir, isn't. And also in regards to the F20B rod. It is in fact 5.709". The compression height on that same piston is equal to that of the H22 as well so basically it's an 85mm bore version of the H22 piston. I suppose you could use F20B pistons(good luck finding those) on a F22 bottom end in a F22 block and still have a 2.2L.

If the H22 pistons would clear the head then I think the F20B pistons should also, but I don't think they would. 0.02" I believe is now out of the block. But using 11:0 domed pistons would bump the comp to like 12.5-6, but I could add a thicker headgasket to lower the comp ratio to an acceptable level.