Oversized Fit Pistons

Per Feb Fastrack:

https://www.apexspeed.com/forums/att...id=83529&stc=1

I just called HPD and spoke wth Vinnie. He said inventory shows over 150 complete Fit crate engines and no shortage of blocks that he knows of. Blocks sell for $800. Also spoke with Steve and Logan Knapp and they said they have had no supply issue with Fit blocks, parts, or complete engines.

The whole point of the Fit was to switch to a modern engine with a steady, long term parts supply to avoid rules creep. HPD holds sufficient inventory to honor their end of that agreement.

Not sure why we need this rule.

Here we go...I'd love to hear the reasoning behind this. Without any further justification I'm a strong no.

We can't start doing this to the Honda unless there are unobtanium parts, why I don't believe is even close to reality.

Edit:

P.S.: 0.25 mm = 0.010”. On the Kent, 0.005” oversizedpistons are allowed. What’s the performance advantage of allowing 0.010”oversized on the Honda?

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Originally Posted by Will Velkoff

P.S.: 0.25 mm = 0.010”. On the Kent, 0.005” oversizedpistons are allowed. What’s the performance advantage of allowing 0.010”oversized on the Honda?

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The performance advantage of .005 or .010 oversized pistons is debatable. On paper it may show something but in reality, it's my opinion that .005 doesn't mean anything. That said, I have .005 pistons in my Kent, and I don't know anyone who wants 'all the power' going with the std piston.

The advantage isn't the issue as I see it. It's the perception of an advantage. As we saw with the Kent, everyone will go with the oversized piston and that will be the new std baseline. It solves nothing and just brings us back to the same problem. In this case, it seems like a problem that doesn't exist.

Sure would be nice to slip in a justification line in the Fastrack release between the letter reference line and the approved rule change. Tell members why, and what this solves. Very possible I am missing it, but I don't see a reason for opening the rules creep door.

The rule proposal is because the bore tolerance is so tight that if you do any damage to the cylinder wall, you go overbore with refinishing the bores. The same problem would occur if your engine gets a lot of time on. You cannot re-ring and refinish your bores without becoming illegal.

So .....the result is that your entire engine becomes junk. If you allow an insignificant overbore, then everything can be saved with the purchase of a set of pistons and rings and the labor to install.

While the Honda-haters can say "screw the bastards that run Honda engines, they deserve it", the reality is that if you run a Honda, this rule will be a significant cost savings for you at some time in your racing life. Why would or should a FF competitor be required to spend $5K to replace his engine core, when he could spend half or less to repair his engine? The DIY type will probably spend 10% to repair instead of replace.

Please don't confuse knee-jerk "screw you" politics with the economics of protecting racers who have already invested heavily in the class. This rule proposal is not rule creep. This would just be a common sense rule to allow low-cost repair or refurbishing.

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Originally Posted by reidhazelton

Per Feb Fastrack: ....


Not sure why we need this rule.

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Because some idiot thinks they're going to either save money or get a competitive advantage by reboring & going to oversized pistons. Mathematically it's about 0.7% more volume, or about 10.5 cc's. The extra 2/3 of tablespoon of displacement might mean something if it wasn't for the fact that that extra air still has to get pulled through an opening a little smaller than a half-dollar coin.

I don't really care either way on this rule, because I overall I think it's a waste of money given the availability of cheaper alternatives. It's like going with an adjustable fuel pressure regulator for any reason other than having one less potential failure item buried inside the fuel cell, or that year everyone went crazy on fancy "ram air" intakes (as if that acutally works below 180mph).

The only way you're going to get significantly past the 115hp barrier with these engines is to cheat. Period. It's not like the Kents that you can massage to 120HP if you don't mind spending gobs of money & having an engine with a lifespan measurable in minutes. Even then you'd have to cheat the right way because of the air restrictor. If I were a tech inspector I'd look for restrictor plate bypasses, lightened flywheels / crankshafts, and ECU tweaks. The ECU tweaks in and of themselves won't really do anything to boost real performance, but if somebody did some weird head, cam, or piston mods there might be gains to be had & the ECU would be the easiest protest to toss them out on.

I've been running the same engines in my cars since I had them blueprinted in April of 2014 (mostly to have them broken in already for the pro series). I sent the one that was the weaker of the two on a leakdown (and it wasn't by much) back to the builder to get dyno-tested in early 2017. It was the same HP as it was in 2014. That engine is the one I won the the last ARRC in. The sister car blew up its engine at VIR after the driver plugged both radiators with grass. We dropped a $400 junkyard motor in it and it was just as strong as the blueprinted engine it replaced.

I'm seriously thinking of just stocking up on a couple of junkers, testing them & freshening them up where needed. I bet I could have two or three ready to swap out at need for less than the cost of a crate motor & the best part is they'll already be broken in.

Meanwhile my competition will be spending money on overbores or wasting time agonizing over rule changes instead of making their cars handle or doing some cardio. ;)

Quote:

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Originally Posted by problemchild

The rule proposal is because the bore tolerance is so tight that if you do any damage to the cylinder wall, you go overbore with refinishing the bores. The same problem would occur if your engine gets a lot of time on. You cannot re-ring and refinish your bores without becoming illegal.

So .....the result is that your entire engine becomes junk. If you allow an insignificant overbore, then everything can be saved with the purchase of a set of pistons and rings and the labor to install.

While the Honda-haters can say "screw the bastards that run Honda engines, they deserve it", the reality is that if you run a Honda, this rule will be a significant cost savings for you at some time in your racing life. Why would or should a FF competitor be required to spend $5K to replace his engine core, when he could spend half or less to repair his engine? The DIY type will probably spend 10% to repair instead of replace.

Please don't confuse knee-jerk "screw you" politics with the economics of protecting racers who have already invested heavily in the class. This rule proposal is not rule creep. This would just be a common sense rule to allow low-cost repair or refurbishing.

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Greg - $5k is a false number. That's not even the cost of a crate engine so I have no idea where you found that number. Must be like $15k Kent rebuilds. A block is $800. Elite uses them often and has no supply issues. How much does it cost to machine and bore a block, and install new pistons?

If it's not rules creep, how many Kents are built with std pistons? Everyone I know goes right for hte .005 over pistons and then we are right back at the beginning.


This has nothing to do with 'Honda Haters', and is just more ad hominum reasoning that distracts from constructive debate.

Quote:

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Originally Posted by problemchild

Please don't confuse knee-jerk "screw you" politics with the economics of protecting racers who have already invested heavily in the class. This rule proposal is not rule creep. This would just be a common sense rule to allow low-cost repair or refurbishing.

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Yep.

If you could still achieve the same BMEP and you were making 115-ish HP the displacement increase doesn't even equal 1 additional HP. The lap time delta is so insignificant, I'd want my competitors spending their money on that, because no matter how big their budget, that's less money and time they have to spend elsewhere on things that would make a bigger difference.

$5K is a realistic number.
$3500 + tax + shipping across the country
So it's $4200 for some ..... $4500 for others .... $5K for others

It is a lot more money than a pkg of pistons and rings + tax + shipping.

Typical SCCA BS. Nosybody ignorant people with no skin in the game influencing other ignorant people with no skin in the game to make racers with skin in the game spend more money.

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Originally Posted by problemchild

Typical SCCA BS. Nosybody ignorant people with no skin in the game influencing other ignorant people with no skin in the game to make racers with skin in the game spend more money.

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Now that would be great for a bumper sticker or T-shirt!

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Originally Posted by problemchild

Typical SCCA BS. Nosybody ignorant people with no skin in the game influencing other ignorant people with no skin in the game to make racers with skin in the game spend more money.

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Didn't that request come from somebody with skin in the game? (Sandy at QS)

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Originally Posted by Daryl DeArman

Didn't that request come from somebody with skin in the game? (Sandy at QS)

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Yes, Sandy has been complaining for years that his customers could not just throw new pistons in damaged engines. It's people who parked their cars years ago that find it a problem. Not unlike FF side pods or FB.

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Originally Posted by problemchild

Yes, Sandy has been complaining for years that his customers could not just throw new pistons in damaged engines. It's people who parked their cars years ago that find it a problem. Not unlike FF side pods or FB.

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Gotcha.

Funny how for years we have had to throw away perfectly good kent blocks forcing us to buy new blocks because we only allowed 5 over. SCCA didn't care what the cost was to us yet when the gate keeper to SCCA wants a change they get it. Ivey was make to jump threw hoops to get every engine builder involved and even then it was an uphill battle to reduce costs for the Kent.
If this is about economics to keep the cost down the the rule should apply to the Kent as well. Since there is no advantage to 10 over bore i would think that the Honda's wouldn't object because whats good for one is good for the other.
It maybe time create a Honda class since they have driven most of the Fords out of SCCA with mostly Honda's at the runoff's.
Formula Ford is thriving in vintage Problem is all the older ford power cars have no place in the game so they are being parked.

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Originally Posted by Latebraker

If this is about economics to keep the cost down the the rule should apply to the Kent as well. Since there is no advantage to 10 over bore i would think that the Honda's wouldn't object because whats good for one is good for the other.

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Why would Honda drivers object to that? Most that I know, just want the biggest most competitive fields possible.

Of course, there are some differences, as kent blocks can be resleeved, and don't become illegal when worn, scored or otherwise. I don't know all the specifics of either engine, but finding feasible solutions to keep costs down for either engine benefits everybody involved. That is much better for this fine class than saying, we cannot do it, so screw them too!

Quote:

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Originally Posted by problemchild

$5K is a realistic number.
$3500 + tax + shipping across the country
So it's $4200 for some ..... $4500 for others .... $5K for others

It is a lot more money than a pkg of pistons and rings + tax + shipping.

Typical SCCA BS. Nosybody ignorant people with no skin in the game influencing other ignorant people with no skin in the game to make racers with skin in the game spend more money.

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Oranges and apples. A block is $800, not $5000. Does it cost $22k for an engine if you decide to buy the whole car?

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Originally Posted by Daryl DeArman

If you could still achieve the same BMEP and you were making 115-ish HP the displacement increase doesn't even equal 1 additional HP. The lap time delta is so insignificant, I'd want my competitors spending their money on that, because no matter how big their budget, that's less money and time they have to spend elsewhere on things that would make a bigger difference.

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I agree, however that has not proven true with the Kent engine and allowing .005 pistons. Everyone just goes for the .005s and that's the new standard. It's not unreasonable to assume the same would happen here.

Quote:

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Originally Posted by problemchild

Why would Honda drivers object to that? Most that I know, just want the biggest most competitive fields possible.

Of course, there are some differences, as kent blocks can be resleeved, and don't become illegal when worn, scored or otherwise. I don't know all the specifics of either engine, but finding feasible solutions to keep costs down for either engine benefits everybody involved. That is much better for this fine class than saying, we cannot do it, so screw them too!

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Right, we both want the same thing but have different views on what this does to that goal.

As I said, with the Kent the .005 is the standard now, so it didn't do anything to save cost except for the first rebuild after the rules change if someone had cylinders that were worn beyond tolerance. It's logical the same will happen here. I don't see this as keeping costs down.

A new block is $800. Done.

A new set of pistons? Not sure on the price. Add to that the cost to bore/hon the block. Rings are moot as they are required in both scenarios.

Depending the piston cost, there isn't much savings - maybe a few hundred bucks after and that's only on the first rebuild as most if not all will go to the .010 piston as most did with the Kent. Yes, it's an assumption that people will opt for the larger piston, but it's a logical one based on history.

Quote:

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Originally Posted by Latebraker

Funny how for years we have had to throw away perfectly good kent blocks forcing us to buy new blocks because we only allowed 5 over. SCCA didn't care what the cost was to us yet when the gate keeper to SCCA wants a change they get it. Ivey was make to jump threw hoops to get every engine builder involved and even then it was an uphill battle to reduce costs for the Kent.
If this is about economics to keep the cost down the the rule should apply to the Kent as well. Since there is no advantage to 10 over bore i would think that the Honda's wouldn't object because whats good for one is good for the other.
It maybe time create a Honda class since they have driven most of the Fords out of SCCA with mostly Honda's at the runoff's.
Formula Ford is thriving in vintage Problem is all the older ford power cars have no place in the game so they are being parked.

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I understand your point. I have no issue with the .010 piston for the Honda, I'd feel the same if it was a .005. It's the creep that bothers me.

What we have seen, is when a larger piston is allowed, that is what becomes the standard. If you have .005 pistons, and need to sleeve a block once it's worn, you put .005s back in and not the std piston - or that's what most did when the Ford was the common engine in nationals. So allowing a larger piston just gets most people back to the same place, but we now have rules creep.

Reid, I just do not think you believe that logic may prevail.

+ 0.005" pistons in a Kent are a "must have" if you're serious about having the same horsepower as everyone else; ie: a material improvement in power as a result of unintended consequences. it's my sense +0.010" pistons in an alternate engine is nothing more than a blatant attempt to improve performance and the end to any reasonable claim of parity !!

Art
artesmith@earthlink.net

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Originally Posted by Art Smith

+ 0.005" pistons in a Kent are a "must have" if you're serious about having the same horsepower as everyone else;

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I didn't realize any Kents had the same horsepower as everyone else ;)

I understand it's all the small stuff that adds up to big stuff and you can't show up to a gun fight with a knife. However, the full potential of a std bore Kent vs a +.005" bore Kent equates to what difference? The guy will increase his amortized costs of engine overhauls by x but come across the scales 15# heavy? So many other things that make a bigger difference that aren't given the same attention.

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Originally Posted by reidhazelton

I understand your point. I have no issue with the .010 piston for the Honda, I'd feel the same if it was a .005. It's the creep that bothers me.

What we have seen, is when a larger piston is allowed, that is what becomes the standard. If you have .005 pistons, and need to sleeve a block once it's worn, you put .005s back in and not the std piston - or that's what most did when the Ford was the common engine in nationals. So allowing a larger piston just gets most people back to the same place, but we now have rules creep.

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Wasn't the Honda allowed because you could buy a brand new crate long block for $3500. I would think a rebuild with new pistons would cost more than $3500 closer to $5-6000. Isn't the Honda suppose run 2-3 times longer between rebuilds than the kent if that is true seems to me they are still further ahead financially than a kent owner so why not buy a new long block from Honda.
If the bigger bore isn't a performance advantage there is no reason for wanting to save a tired bottom end when new ones are available for less than a rebuild.

As I take another sip of coffee and then let out a little chuckle for only myself to hear. ;)

+0.005" oversized pistons for Kents has been proven to be extremely poor policy. the alleged cost saving
for a few competitors avoiding sleeving worn-out cylinders required the entire competitive Kent community to
rebuild their engines AND purchase new forged pistons from a sole source provider. +0.010" oversized pistons
for the alternate engine is even worse policy!! the alleged cost saving for a few competitors that have worn
out their cylinders or abused their engines will require the entire alternate engine community to have their
engine rebuilt AND purchase new pistons. AND the +0.010" pistons will shatter all appearances of
competitive balance adversely impacting competitors running Kent AND subjecting the whole FF community
to another divisive round of arguing about restrictor sizes............... the only people who benefit from this
proposed change will be the engine builders servicing the alternate engine market; BAD idea !!!

Art
artesmith@earthlink.net

Having only raced in Formula Ford for 3 years, I’m quite sure many of you have more first hand experience with this sort of thing in FF as it pertains to the Kent over the last few decades. Being the case, I’ve heard/learned from various members of our community, I can see some of both sides.

However, over the years I have competed in many spec series or series that require strict/limited engine rules. From karting to cars. EVERY time some small change is approved, it will set a new standard for a blueprinted engine. Yes it may save a few people from replacing an engine block. But now every engine that gets blueprinted by one of the pro builders will have to have these larger pistons. Well, at least the competitive community will demand it. Even if the HP benefit is negligible. It will be the new norm. Why would anyone pay for a $2500 blueprint with standard pistons, if they could just pay $3100 for the blueprint to be done all the way. (Just throwing out potential differences). Everyone who opts for a blue print will opt for the larger pistons. If anything, this will also create another possible performance advantage that a blueprinted engine has over a crate or junk yard motor, creating even more demand. Now who wins in this scenario in the big picture? The engine builder/supplier of course. Since I’m newer to FF, maybe this class is different, but I seriously doubt it.

in talking to a few long time formula car racers over the last year, the conversation of Kent vs Fit has come up a few times. Most of the time I’m always asked why I run a Kent. My typical response is that I believe the Kent is just as fast, it races like a real race car(no rev limiter, and it doesnt make financial sense for me to switch. On the last one, they always look at me like I have two heads. Then I hear about these $7500 rebuilds a number of other builders charge. While I can’t speak to this personally, I’ve heard numerous stories from people all over the country in their experience with various builders. If my only option was to pay $7500 for a rebuild, I’d put both my Kents up for sale next week.. The consensus of all of the conversations always comes back to the fact that if $7500 rebuilds hadn’t become the norm, many many more drivers would still have and race Kents competitively.

My rebuilds cost no where near $7500. Even when replacing lots of hard parts. It is possible and very doable. And I have to honestly say I don’t know that I’ve competed against another Kent by a different engine builder that was as fast. I’ve raced against a few Kent’s built by the same builder that were just as fast if not faster than mine. But none by other builders. I’m sure there are plenty out there, my point is that I feel I still get a great product for a lot less money. So as a newbie (sort of), I have to ask, what really killed the Kent? Most agree....the $7500 rebuild is specifically what killed it.

That said, I would just be careful what you wish for. You need to take a serious look at any rule proposed by vendors and not competitors. Doesn’t mean there’s always a bad intention, sometimes just the opposite, but it just needs to be looked at closely and from all angles. I don’t have a Honda, and I also think there IS currently extreme parity between legal examples of both engines ... now. If you guys with Hondas want to pay more for a new benchmark on every engine going forward, have at it. My only concern would be that both engines are treated equally with any rules adjustment. (But I’d really rather not have to go buy bigger pistons myself to keep things fair)

I have little doubt that the main reasoning for allowing this change comes from the best intentions, to save money. But in the end, my firm belief is that it will do just the opposite. It will save a few some money, but in the long run, it will cost more competitors more money on more engines, and create the potential for disparity between Honda engines when their currently appears to be little or none.

I was doing some machining yesterday and the image of 10 thou was reinforced in my mind. We are talking about

1/100th of 1 inch.

Nobody else is going to have to rebuild anything to keep pace. Very good kents will still have their advantage. Weenies who parked their cars can leave their cars parked. Honda haters can still hate Hondas. FF racers who want to race with lots of nicely matched cars can still race FF. Honda engine builders who choose to maximize their bores to start their life, will still need to replace blocks or crate engines when they become illegal (as currently). Nothing that happens on the track will change.

The only ones getting any benefit are people who started with crate engines or wrecker engines (with original-sized bores) who will now have more life with less expensive repairs.

There will be no significant advantage. Just like the street car driver, the racer can now repair his engine rather than replace it. It is a cost-saving repair. That is the whole point of oversize pistons. They are not sold in an HPD Performance catalog, but over the counter at a Honda dealer, in the same way as you buy .010" oversize engine bearings so that you can turn the crank instead of replacing it. All the 1/100" oversized piston specs are included in the Honda FIT service manual as part of the repair process.

This is not a technical matter. This is a political matter, driven by people looking to punish Honda users.
Hopefully, common sense will prevail.

One definition of an oxymoron might well be putting the words "hopefully common sense will prevail" in a sentence about anything regarding racing...…

We can only hope Greg is right but I'm not holding my breath.....

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Originally Posted by problemchild

I was doing some machining yesterday and the image of 10 thou was reinforced in my mind. We are talking about

1/100th of 1 inch.

Nobody else is going to have to rebuild anything to keep pace. Very good kents will still have their advantage. Weenies who parked their cars can leave their cars parked. Honda haters can still hate Hondas. FF racers who want to race with lots of nicely matched cars can still race FF. Honda engine builders who choose to maximize their bores to start their life, will still need to replace blocks or crate engines when they become illegal (as currently). Nothing that happens on the track will change.

The only ones getting any benefit are people who started with crate engines or wrecker engines (with original-sized bores) who will now have more life with less expensive repairs.

There will be no significant advantage. Just like the street car driver, the racer can now repair his engine rather than replace it. It is a cost-saving repair. That is the whole point of oversize pistons. They are not sold in an HPD Performance catalog, but over the counter at a Honda dealer, in the same way as you buy .010" oversize engine bearings so that you can turn the crank instead of replacing it. All the 1/100" oversized piston specs are included in the Honda FIT service manual as part of the repair process.

This is not a technical matter. This is a political matter, driven by people looking to punish Honda users.
Hopefully, common sense will prevail.

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All other things being equal, .010 overbore calculates to almost 1 HP increase. To me, this is significant. The perceived advantage by most racers is even more real. Allowing oversized pistons is a BAD idea. But since I have no confidence in the SCCA rules change system, I will just deal with whatever is decided by those in control. Thank you Sir, may I have another.......

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Originally Posted by Michael Rand

One definition of an oxymoron might well be putting the words "hopefully common sense will prevail" in a sentence about anything regarding racing...…

We can only hope Greg is right but I'm not holding my breath.....

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History is the best predictor of the future.

.010 will be the standard, as has happened with the Kent.

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Originally Posted by problemchild

Weenies who parked their cars can leave their cars parked. Honda haters can still hate Hondas.

This is not a technical matter. This is a political matter, driven by people looking to punish Honda users.
Hopefully, common sense will prevail.

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You need to find reality and come off your half baked conspiracy theories and thinly veiled ad hominum attacks at anyone who has a different point of view, which is your normal go-to move on apexspeed. It's getting old. Apparently you didn't get the message from your 30-day timeout.

How does it punish Hondas to enforce the rules as are and not allow a larger piston? Someone being against a rule change that is an advantage is not punishment, it's equality. The rule is in effect - so your 'punishment' claim makes zero sense. If it was rejected, then maybe you could claim that conspiracy.

You're right. Racing is not about optimizing everything, everywhere you can to get an advantage. No one will spend money to get 1hp more than the next guy because racers are all sane and logical people who are happy to leave speed on the bench in the shop. Races in FF or F1600 are never decided by close margins, like .001 of a second, so what's .010" on some pistons? Oh wait...these close finishes happen nearly every F1600 race. Silly me, I forgot.

Signed,
Weenie

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Originally Posted by jchracer

All other things being equal, .010 overbore calculates to almost 1 HP increase. To me, this is significant. The perceived advantage by most racers is even more real. Allowing oversized pistons is a BAD idea. But since I have no confidence in the SCCA rules change system, I will just deal with whatever is decided by those in control. Thank you Sir, may I have another.......

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Originally Posted by reidhazelton

History is the best predictor of the future.

.010 will be the standard, as has happened with the Kent.

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Doesn't this quote below from a previous poster answer your argument eliminating the possible 1 HP increase listed above? Isn't the air the current limiting factor anyways at this point with the restrictor?

"Because some idiot thinks they're going to either save money or get a competitive advantage by reboring & going to oversized pistons. Mathematically it's about 0.7% more volume, or about 10.5 cc's. The extra 2/3 of tablespoon of displacement might mean something if it wasn't for the fact that that extra air still has to get pulled through an opening a little smaller than a half-dollar coin."

Quote:

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Originally Posted by Steve Bamford

Doesn't this quote below from a previous poster answer your argument eliminating the possible 1 HP increase listed above? Isn't the air the current limiting factor anyways at this point with the restrictor?

"Because some idiot thinks they're going to either save money or get a competitive advantage by reboring & going to oversized pistons. Mathematically it's about 0.7% more volume, or about 10.5 cc's. The extra 2/3 of tablespoon of displacement might mean something if it wasn't for the fact that that extra air still has to get pulled through an opening a little smaller than a half-dollar coin."

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If that is true, why have any restriction on displacement on any engine with a restrictor?

The carb throats on a Kent function the same way, so how do .005 pistons make more power?

The Honda needs a smaller restrictor, in general, anyways.

Let the Kent run a 0.010" over piston too. I mean, if this is really about saving money, then what should Kent people do when 0.005" bores are worn out?

Boring an engine out not only increase its volume, but on most motors will increase compression also.

Bore away Honda, I am happy with my Kents.

Ed

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Originally Posted by reidhazelton

If that is true, why have any restriction on displacement on any engine with a restrictor?

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Now you are taking this to the extreme Reid. We are not talking about unlimited displacement.

I think you are taking the information provided by another poster that I reposted out of context. If numbers are listed are correct you are taking a 1500 cc engine & increasing to 1510.5 cc, do I have that correct? If so you have increased the area by .00695. You are not allowing more air in based on the restrictor correct? If so then math doesn’t add to up to 1 hp increase even if you added air, which you are not. I thought air was an important factor in combustion, Maybe I am totally wrong here which I will except.

.

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Originally Posted by jharvey

The Honda needs a smaller restrictor, in general, anyways.

Let the Kent run a 0.010" over piston too. I mean, if this is really about saving money, then what should Kent people do when 0.005" bores are worn out?

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Finally, someone with sense (which is rare, certainly not common)!

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Originally Posted by Steve Bamford

Now you taking this to the extreme Reid. We are not talking about unlimited displacement.

I think you are taking the information provided by another poster that I reposted out of context. If numbers are listed are correct you are taking a 1500 cc engine & increasing to 1510.5 cc, do I have that correct? If so you have increased the area by .00695. You are not allowing more air in based on the restrictor correct? If so then math doesn’t add to up to 1 hp increase even if you added air, which you are not. I thought air was an important factor in combustion, Maybe I am totally wrong here which I will except.

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The extreme was the intent to show a logic flaw that the claim displacement does not matter on restricted engines. We both agree it does matter, we just disagree on how much increase is acceptable. I saw zero, some say .010. The curve is not as follows:
.005 - no effect.
.010 - no effect.
.015 - no effect.
.020 - no effect.
.025 - no effect......
.125 - 20 more hp.

It's not a question of if it makes a increase in power, but how much of an increase matters and is acceptable. I still say 0 given any increase will be the new standard.

An internal combustion (4-stroke in this case) engine doesn't quite work like that in relation to a restrictor. On the intake stroke a vacuum is created. That vacuum pulls air, not passively allow it to pass the restrictor. There is a force acting on it. If the volume on the vacuum end is increased, there is a larger vacuum force created, and will pull harder through the restrictor. The same is true if you look a the opposite in a pressure force.

Allow me to try an analogy. Take a drinking straw. That will be the restrictor. Blow/suck through it. Now, empty your lungs and give that thing a big pull. More air traveled through that straw, yet being the same size straw, right? Same idea here.

Like I said, the performance increase is debatable for sure. I understand that. But, no racer I know calls up their engine builder and says 'give me a moderate amount of horsepower, just what's reasonable'. We all say give me the most I can get and some! Given very similar rules in the past, we can assume history will repeat. This will only save money on the first rebuild for those with damaged cylinder walls, and maybe the savings there will be $500. Yet, this will likely (again, given history) require .010" to be the new standard.

The Kent is that historical lesson. After the rule for .005" came into effect, it saved me from sleeving my engine on a rebuild. Cool. That's a plus. But, two rebuilds later when the bores were worn too large, and it needed to be sleeved, .005 pistons were put back in. And if .010" pistons were allowed in the Kent, it's even more likely no one will go with standard pistons.

Performance increase debate aside, my concern is the perception. (Yes, I understand this thread perpetuates this but I feel it's more than perception.) Take for sale threads as a data point. Why do people list '.005"+' pistons as a positive attribute when selling an engine. Because people see that as an advantage.

I have nothing against the Honda other than how Honda (HPD) pushed it in as 'a few guys who work for HPD and put a Honda in a DB1 because we love FF, while those guys had zero HPD support". It's a great engine, and once you're in one life is much better and cheaper. My issue with this rule is it will not result in what the well-intended rule makers hoped. There is no reason to think this situation will be different than with any other oversized piston allowance.

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Originally Posted by Steve Bamford

Now you taking this to the extreme Reid. We are not talking about unlimited displacement.

I think you are taking the information provided by another poster that I reposted out of context. If numbers are listed are correct you are taking a 1500 cc engine & increasing to 1510.5 cc, do I have that correct? If so you have increased the area by .00695. You are not allowing more air in based on the restrictor correct? If so then math doesn’t add to up to 1 hp increase even if you added air, which you are not. I thought air was an important factor in combustion, Maybe I am totally wrong here which I will except.

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The flow rate (and hence the HP) through the restrictor will be proportional to the increase in displacement of the engine with the overbore (roughly 0.6%). The restrictors do not "cap" the flow rate as many people think.....it's a fluid dynamics thing....