Naturally Aspirated Buildup of F20C
07-13-2001, 11:33 AM
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Naturally Aspirated Buildup of F20C
Hey all, I just picked up the new issue of Sport Compact Car and it has a good article on the build up of naturally aspirated Honda engines used in drag racing. A lot of what was mentioned in the article can be applied to street motors.
So, here are some thoughts from the article on building up an F20C. I'd appreciate any comments on them.
Increasing displacement:
Apparently the 2.2l Prelude engine can be pushed out to 2.6l with the correct bore and stroke, and the 1.8l B18 series can be pushed out to 2.4l. This is some enormous displacement increases, signifying that it may be possible to push the F20C out beyond the 2200cc that Mugen has already managed.
One critical aspect of stroking the F20C is the peak piston speed. This speed can be slowed by changing the rod to stroke ratio. This can be done by welding in a spacer between the top of the block and the head, and subsequently changing to a stroker crank and longer rods.
Problems I foresee:
1) Dealing with the special cylinder liners. These would need to be removed and replaced with steel cylinder liners.
2) Will the taller engine (due to the spacer) interfere with the S2000's hood?
3) How much would making a new crankshaft of suitable quality cost? Is the crank the same as that in the new K engine series to alleviate costs?
Better flow through the engine:
This relates to removing or re-engineering stock bottlenecks to air flow through the engine.
1) Air box. Much backyard and tuner R&D is being done in this respect to get a cool fresh air charge into the engine.
2) Intake manifold. There most probably is some restriction in here. Things like a new intake plenum (easiest way is to design it out of sheetmetal.), velocity stacks and a bigger throttle body (perhaps even individual throttle bodies) would be the way to go here. Developing this area would probably consist of a lot of trial and error, but some good gains could be accomplished.
3) The cylinder head. Certainly an excellent design to start with, but some hand finishing of the valve seats would be beneficial. Perhaps a reshaping of the cylinder heads into a clover leaf design may also be beneficial. I don't know enough about head design to comment further.
4) The cam shafts. Considerable hp could probably be unleashed here. Not only on the big cam profiles, but also using the low rpm profiles. By exagerating the stock assymetric low-rpm valve openings (used to induce a swirl in the intake mixture) perhaps even greater low and midrange torque can be extracted from the engine.
5) The exhaust. Much R&D has already been accomplished here, but there may still be interesting designs to try.
6) Engine management. To provide optimum fueling to the tuned motor, some kind of programmable engine management would need to be installed.
7) Raising the rev limit. Consideration should be given to raising the revlimit to 10,000rpm. The 10% increase in rpm, if optimised, will boost horsepower, and allow 10% lower gearing to be installed in the final drive while maintaining speed in gears.
I believe that there is a lot of hidden hp in the F20C, we just have to systematically and logically hunt it out.
I would imagine a fully stroked and built F20C could make in excess of 320hp at the crank on pump gas, and perhaps a stock stroked F20C could make north of 280hp at the crank.
To me, this would be a more interesting route to follow than a supercharger or turbo.
So, here are some thoughts from the article on building up an F20C. I'd appreciate any comments on them.
Increasing displacement:
Apparently the 2.2l Prelude engine can be pushed out to 2.6l with the correct bore and stroke, and the 1.8l B18 series can be pushed out to 2.4l. This is some enormous displacement increases, signifying that it may be possible to push the F20C out beyond the 2200cc that Mugen has already managed.
One critical aspect of stroking the F20C is the peak piston speed. This speed can be slowed by changing the rod to stroke ratio. This can be done by welding in a spacer between the top of the block and the head, and subsequently changing to a stroker crank and longer rods.
Problems I foresee:
1) Dealing with the special cylinder liners. These would need to be removed and replaced with steel cylinder liners.
2) Will the taller engine (due to the spacer) interfere with the S2000's hood?
3) How much would making a new crankshaft of suitable quality cost? Is the crank the same as that in the new K engine series to alleviate costs?
Better flow through the engine:
This relates to removing or re-engineering stock bottlenecks to air flow through the engine.
1) Air box. Much backyard and tuner R&D is being done in this respect to get a cool fresh air charge into the engine.
2) Intake manifold. There most probably is some restriction in here. Things like a new intake plenum (easiest way is to design it out of sheetmetal.), velocity stacks and a bigger throttle body (perhaps even individual throttle bodies) would be the way to go here. Developing this area would probably consist of a lot of trial and error, but some good gains could be accomplished.
3) The cylinder head. Certainly an excellent design to start with, but some hand finishing of the valve seats would be beneficial. Perhaps a reshaping of the cylinder heads into a clover leaf design may also be beneficial. I don't know enough about head design to comment further.
4) The cam shafts. Considerable hp could probably be unleashed here. Not only on the big cam profiles, but also using the low rpm profiles. By exagerating the stock assymetric low-rpm valve openings (used to induce a swirl in the intake mixture) perhaps even greater low and midrange torque can be extracted from the engine.
5) The exhaust. Much R&D has already been accomplished here, but there may still be interesting designs to try.
6) Engine management. To provide optimum fueling to the tuned motor, some kind of programmable engine management would need to be installed.
7) Raising the rev limit. Consideration should be given to raising the revlimit to 10,000rpm. The 10% increase in rpm, if optimised, will boost horsepower, and allow 10% lower gearing to be installed in the final drive while maintaining speed in gears.
I believe that there is a lot of hidden hp in the F20C, we just have to systematically and logically hunt it out.
I would imagine a fully stroked and built F20C could make in excess of 320hp at the crank on pump gas, and perhaps a stock stroked F20C could make north of 280hp at the crank.
To me, this would be a more interesting route to follow than a supercharger or turbo.
07-13-2001, 12:54 PM
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interesting perhaps, but it would cost so much that only properly sponsored racers would be able to afford it. Remember word is the crank alone is $5000 on the mugen stroker kit.
Then you add custom rods, deck plates, machine work of the block, etc etc... not to mention who knows how many cranks and rod combination you'd have to do inorder to get it right. Cost would just be way out of reach for most. With a turbo kit at say $5-$6k, that all of a sudden seem like very cheap.
-Shing
Then you add custom rods, deck plates, machine work of the block, etc etc... not to mention who knows how many cranks and rod combination you'd have to do inorder to get it right. Cost would just be way out of reach for most. With a turbo kit at say $5-$6k, that all of a sudden seem like very cheap.
-Shing
07-13-2001, 01:09 PM
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Regarding higher RPM, the boost in HP will only happen if engine torque doesn't fall faster than RPM rises. I've seen ads, Spoon I think, that say our piston weights could be drastically reduced. That, and some really exotic valve springs, could allow safe faster piston speed. On cams, I'd be concerned about streetability. There's only so much lumpy idle I'd put up with.
I agree the whole stock intake design is a bit of a mystery to me. I can see it is tuned for resonances but it looks like overkill and it lacks a cold air inlet.
UL and others have pointed out how rich our cars run. I get tons of soot on the exhaust tips. Seems like too much margin of safety. But if THAT is what keeps cylinder #4 from burning up then a bored TB (leaner mixture) may not be such a slick idea.
I agree the whole stock intake design is a bit of a mystery to me. I can see it is tuned for resonances but it looks like overkill and it lacks a cold air inlet.
UL and others have pointed out how rich our cars run. I get tons of soot on the exhaust tips. Seems like too much margin of safety. But if THAT is what keeps cylinder #4 from burning up then a bored TB (leaner mixture) may not be such a slick idea.
07-13-2001, 01:11 PM
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Ah, yes, Mr. Kojima's piece on NA engines. Frankly, one of the more disappointing pieces of work I've seen from him (not trying to be overly critical, Mike's a great guy and conrtibutes many positive things). I think the problem is that he only had part of the picture. There is so much "massaging" of the rules in Import Pro-Stock that what the tuners told him may not be the whole story, and as a good journalist, he can't really speculate on rumors, etc. For example, if these engines are truly only getting 260 wheel hp, then they're no better than a stock bore/stroke B20 VTEC conversion with a good head and cams and stronger bottom end parts. In reality, 2.0 liters in a drag racing configuration should be able to exceed 330-340 crank hp, or over 300 to the wheels.
With respect to your comments Rob, you've got the piston speed issue a bit muddled. Average piston speed is solely a function of stroke length and rpm. Changing rod/stroke ratio can alter peak piston speed slightly, but in fact, a longer rod will increase piston speed through the middle of the stroke and decrease it near the top. You do tend to have a better acceleration profile with longer rods and jerk (change in rate of acceleration) is better too. However, no matter how long your rods, if you go to a longer stroke, piston speeds and accelerations increase - and that's typically not desirable. I'm not a particularly big fan of stroke increases on a high revving engine. Bore? Hell yeah, within reason.
Overall though, I think you're on the right track. Experimentation, R&D and trial and error are what it will take, plus some $$$.
UL
With respect to your comments Rob, you've got the piston speed issue a bit muddled. Average piston speed is solely a function of stroke length and rpm. Changing rod/stroke ratio can alter peak piston speed slightly, but in fact, a longer rod will increase piston speed through the middle of the stroke and decrease it near the top. You do tend to have a better acceleration profile with longer rods and jerk (change in rate of acceleration) is better too. However, no matter how long your rods, if you go to a longer stroke, piston speeds and accelerations increase - and that's typically not desirable. I'm not a particularly big fan of stroke increases on a high revving engine. Bore? Hell yeah, within reason.
Overall though, I think you're on the right track. Experimentation, R&D and trial and error are what it will take, plus some $$$.
UL
07-13-2001, 05:19 PM
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FYI:
spoon's pistons are almost half the weight (631.64 grams vs. 361.05) of stock pistons, with increased compression to 12.19:1 from JDM stock's 11.68 to 1. add to their titanium valve springs and their reworked valves, plus the headwork, head gasket (thinner), cams, and all the jazz they do to the engine, spoon's F20C is a completely different animal from the factory with a much higher redline. it takes more than 40 hours of master technician work for the engine rework to be done. mugen takes a completely different approach from a different perspective, of course. but i think if you want to build up your engine the NA way, then spoon offers something no other s2000 tuners do (at least, not to the public anyway). also, spoon uses their own flowbench to do the headwork, and they have their own engine dyno (similar to what you see at mugen's facility) to test their products, except spoon is a much smaller outfit.
[begin my plug]
i'm going to keep saying this for a long time: spoon as a company, from ichishima-san down to the junior technicians, sell parts so they can race, not the other way around. you won't find a more hard core, dedicated, and maybe even a little crazy bunch of people who loves nothing but to make a honda civic, integra, or s2000 a few hundred pounds lighter, add a few thousand RPMs of higher redline, and add as much power as possible from what's available. to say that i believe in spoon's abilities is an understatement, but after driving around the s2000 for over a year now, i can slowly begin to appreciate and understand their fanaticism about racing hondas on a circuit (NOT, i repeat, NOT in a straight line). my only wish is that they would hire someone, ahem, like me who has more of a business oriented view towards all of this. all the supply problems, the inventory problems, and all the distribution problems facing spoon are classic cases of a management team in need of the services of a good MBA (ahem, like yours truly
) who would love to jump in and make spoon as famous worldwide as any other big brands and fix all those problems with technology, management, marketing, and sales skills. 
[/end plug]
you can buy a fully prepped spoon F20C for around $13K or so plus shipping, with just about everything i mentioned above. of course you'll want to get spoon's header, exhaust, and ECU to go with that if you do go that route.
anyone crazy enough to do this?
spoon's pistons are almost half the weight (631.64 grams vs. 361.05) of stock pistons, with increased compression to 12.19:1 from JDM stock's 11.68 to 1. add to their titanium valve springs and their reworked valves, plus the headwork, head gasket (thinner), cams, and all the jazz they do to the engine, spoon's F20C is a completely different animal from the factory with a much higher redline. it takes more than 40 hours of master technician work for the engine rework to be done. mugen takes a completely different approach from a different perspective, of course. but i think if you want to build up your engine the NA way, then spoon offers something no other s2000 tuners do (at least, not to the public anyway). also, spoon uses their own flowbench to do the headwork, and they have their own engine dyno (similar to what you see at mugen's facility) to test their products, except spoon is a much smaller outfit.
[begin my plug]
i'm going to keep saying this for a long time: spoon as a company, from ichishima-san down to the junior technicians, sell parts so they can race, not the other way around. you won't find a more hard core, dedicated, and maybe even a little crazy bunch of people who loves nothing but to make a honda civic, integra, or s2000 a few hundred pounds lighter, add a few thousand RPMs of higher redline, and add as much power as possible from what's available. to say that i believe in spoon's abilities is an understatement, but after driving around the s2000 for over a year now, i can slowly begin to appreciate and understand their fanaticism about racing hondas on a circuit (NOT, i repeat, NOT in a straight line). my only wish is that they would hire someone, ahem, like me who has more of a business oriented view towards all of this. all the supply problems, the inventory problems, and all the distribution problems facing spoon are classic cases of a management team in need of the services of a good MBA (ahem, like yours truly
) who would love to jump in and make spoon as famous worldwide as any other big brands and fix all those problems with technology, management, marketing, and sales skills. [/end plug]
you can buy a fully prepped spoon F20C for around $13K or so plus shipping, with just about everything i mentioned above. of course you'll want to get spoon's header, exhaust, and ECU to go with that if you do go that route.
anyone crazy enough to do this?
07-13-2001, 07:50 PM
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No thanks. $13,000 is simply too much for what you get. Spoon's work is good quality, but they simply haven't gotten enough power out of past examples of engines I've seen for me to be willing to outlay that kind of dough. Their B-series "crate" engines were very disappointing on the dyno, as are their b-series cams. And I walked away from one on the road course too in my old car (NA B18C).
I think the big problem is that the Japanese suppliers, for whatever reason, have decided to stake out a very high price area. Unfortunately, their results are rarely much better, if at all, than "lesser" tuners.
Let me give you some examples of what I think it should cost to build a good F20C (assuming certain parts come out, which I think they will).
1. Bottom end - rods and crank are fine. I'd repalce the rod bolts ($120) though. Piston manufacturers, many of whom do pistons for high level race series are a dime a dozen world wide, and Spoon probably uses one of them. Since Spoon hasn't done anything special to the quench areas of the piston, their primary goal appears to be less weight and more compression. A custom designed, one off set, with proper coatings, would cost you about $800-$1000 max. Do a run of 5 or 10 sets and that price drops dramatically.
2. Cams - Toda. Nuff said. Not Jun, nor Spoon, nor Crower have matched Toda in performance _and_ quality on past Honda engines. Inital price? About $1500, but it will drop. And Toda races F3000 and the like too and they sell a lot of parts.
3. Headwork - $1200 investment for R&D (unless you want to wait). After that, call it $1000-$1500 depending on parts (valves, springs, retainers - ti retainers cost about $10 each in small quantities). I think the some of the best cylinder head porters in the world are in the U.S., but Britain might be better - their motorsports industry is soooo good. Guess where all the best NA touring car engines are built?
4. Intake manifold - $2000 for ITBs. That's a one off price for a custom adaptor. Price would drop in quantity.
5. Engine management - $2500
6. Install/tuning - $2000
That's about a total of $10k-11k for an engine with management and ITBs (not necessarily recommended for street use), somethign you don't get in the Spoon package. Stick with a prep'd intake manifold and you'd knock $1000-$1500 off the price. Go with a modded stock ECU and you'd save another $1000 or more. Otherwise, you should get additional power. And this is for largely one off parts. Do a few of these and the costs go down quite a bit. This is not to knock Spoon (or Mugen) as both companies are high quality, but sometimes a bit overhyped here in the U.S. Drop the price on the Spoon crate engine to $7-8k with core exchange and I'd be interested. The only other way I'd consider buying a Spoon engine is if I were competing in a spec series. same for Mugen. Otherwise, there is more power to be had with your own development program. All IMHO of course, but for $13k I want a lot more than valvetrain, bottom end and cams. The security of a developed package is nice, but not for me. Having gone through the development process and reaped the rewards, I'll go that route (albeit slowly).
Of course, Richard, should you choose to purchase one of these engines, I will of course be first in line asking for a test drive :-)
UL
I think the big problem is that the Japanese suppliers, for whatever reason, have decided to stake out a very high price area. Unfortunately, their results are rarely much better, if at all, than "lesser" tuners.
Let me give you some examples of what I think it should cost to build a good F20C (assuming certain parts come out, which I think they will).
1. Bottom end - rods and crank are fine. I'd repalce the rod bolts ($120) though. Piston manufacturers, many of whom do pistons for high level race series are a dime a dozen world wide, and Spoon probably uses one of them. Since Spoon hasn't done anything special to the quench areas of the piston, their primary goal appears to be less weight and more compression. A custom designed, one off set, with proper coatings, would cost you about $800-$1000 max. Do a run of 5 or 10 sets and that price drops dramatically.
2. Cams - Toda. Nuff said. Not Jun, nor Spoon, nor Crower have matched Toda in performance _and_ quality on past Honda engines. Inital price? About $1500, but it will drop. And Toda races F3000 and the like too and they sell a lot of parts.
3. Headwork - $1200 investment for R&D (unless you want to wait). After that, call it $1000-$1500 depending on parts (valves, springs, retainers - ti retainers cost about $10 each in small quantities). I think the some of the best cylinder head porters in the world are in the U.S., but Britain might be better - their motorsports industry is soooo good. Guess where all the best NA touring car engines are built?
4. Intake manifold - $2000 for ITBs. That's a one off price for a custom adaptor. Price would drop in quantity.
5. Engine management - $2500
6. Install/tuning - $2000
That's about a total of $10k-11k for an engine with management and ITBs (not necessarily recommended for street use), somethign you don't get in the Spoon package. Stick with a prep'd intake manifold and you'd knock $1000-$1500 off the price. Go with a modded stock ECU and you'd save another $1000 or more. Otherwise, you should get additional power. And this is for largely one off parts. Do a few of these and the costs go down quite a bit. This is not to knock Spoon (or Mugen) as both companies are high quality, but sometimes a bit overhyped here in the U.S. Drop the price on the Spoon crate engine to $7-8k with core exchange and I'd be interested. The only other way I'd consider buying a Spoon engine is if I were competing in a spec series. same for Mugen. Otherwise, there is more power to be had with your own development program. All IMHO of course, but for $13k I want a lot more than valvetrain, bottom end and cams. The security of a developed package is nice, but not for me. Having gone through the development process and reaped the rewards, I'll go that route (albeit slowly).
Of course, Richard, should you choose to purchase one of these engines, I will of course be first in line asking for a test drive :-)
UL
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07-13-2001, 09:00 PM
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Hey Richard ... I wonder if you've applied to Spoon about your innovative ideas? I'm sure they can put good talent to good use. You should forward a long transcript with an attachment of your resume in Japanese and see what the results generate, you never know ... This might just be the thing to get you outta unemployment.
07-14-2001, 01:16 AM
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Hey guys
Im curious, if you were to do a full and complete engine package as was mentioned above... How much Horsepower and TQ are we talking???
Just curious.... my mind likes numbers even though they arent necessary
thanks
Im curious, if you were to do a full and complete engine package as was mentioned above... How much Horsepower and TQ are we talking???
Just curious.... my mind likes numbers even though they arent necessary
thanks
07-14-2001, 10:43 AM
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Marco, that really depends, but 300 crank hp isn't unreasonable and 320 would be a good goal if you retain stock displacement.
If you assume that peak power is made somewhere between 9k and 10k rpm, then torque at that level would need to be around 165-170 lbs-ft. Peak torque would be somewhat higher, in the 180-190 lbs-ft range.
Keep in mind that 2.0 liters with more restrictions than ours have made as much or more power in the past, so it really isn't anything new to get 300 hp.
UL
If you assume that peak power is made somewhere between 9k and 10k rpm, then torque at that level would need to be around 165-170 lbs-ft. Peak torque would be somewhat higher, in the 180-190 lbs-ft range.
Keep in mind that 2.0 liters with more restrictions than ours have made as much or more power in the past, so it really isn't anything new to get 300 hp.
UL