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F24 Reliability and failures

 
Old 01-05-2019, 01:42 PM
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Can you side one instance of F24 failure because of piston sideloading? I doubt it. The 99mm stroke and 1.5 rod/stroke ratios aren't particularly onerous. Honda does use that weird FRM cylinder construction on the S2000 which dramatically limits piston options. Stroking limits usually center around supporting the piston at the bottom of the stroke, clearing the rod on the side of the cylinder bore, clearing the crank counterweights, how small a compression height can be built into the piston (especially FI/nitrous pistons that have thick crowns) and reduced crank strength because there is less overlap between the main and rod journals. The last is a bigger issue on longer cranks.

Using closed deck steel liners and a modern piston this should be a non-issue. It also gives the option of using abradable coatings. IPL's kit uses FRM compatible pistons...but it still shouldn't be a problem on an NA engine. If you are using FI and E85 I imagine IPL would recommend sleeves.

The Inline Pro 2.4L uses a custom CP piston that is FRM compatible. The Carillo/CP catalog lists all the off-the-shelf F22 pistons as sleeve required. The ILP kit includes the crank, rods, and pistons. It doesn't specify stroke, rod length, or compression height, all of which could have been custom.

As I understand it, the reason the AP2 had a lower rev limit was breathing. While the head is arguably the best on a sport compact (high flowing, big valves, roller camshaft when others are flat tappet) A 2.4L running the same engine speed is going to need 12% more air than a 2.153L. Add 10% to the revs and it is now 22%. Use those steel liners to go to an 89mm bore. and it's over 25% more. That's where the power is: burning more air.

Without more air, it is just moving the power band to lower engine speeds. Many (most?) racing classes have lots of rules to equalize power. Actual chassis dyno numbers are now very popular. Before that, it was very stringent rules; a few years ago half the top Spec Miata finishers at the SCCA runoffs were disqualified because of a rule interpretation of engine machining around the valve guide. Another year the winning Spec Racer Ford was disqualified because of the packing material he used in his muffler.

The kit is relatively inexpensive for parts, but it is part of a complete engine rebuild. What works for any specific owner is going to depend on what they are looking for, what they want to spend, and what rules they are racing under. If I was going that far, I'd spend the extra $1600 and sleeve the block ending future FRM issues, making future sleeve replacement easier, and allowing a larger bore. ILP can do the sleeving, their price is $1595, but shipping is required.

But to get 12% more power the engine needs 12% more air. Figure out what power curve you want, what rules you run under, and what you want to spend. then give IPL or 4P a call and see what they recommend.

For more fun on the track, a sequential gearbox with a Motec or equivalent ECU that allowed no-clutch no lift upshifts and no clutch auto-blip downshifts might be more fun. Left foot braking and perfect downshifts every time. Quaife even has one with helical gears so there isn't a gear whine on the street. Long Road Racing offers that as an option for their Global MX-5 Cup cars.
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Old 01-05-2019, 01:44 PM
  #32  
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Originally Posted by Scigheras View Post
This is correct, the block is the limiting factor because of higher piston speeds caused by a longer stroke.
Not what I was saying. Piston speed can be a limiting factor at some point but not the main issue with the typical stroker package. Check this article from super street regarding rod/stroke ratio. This is the gist of why ballade decided to add deck height to the block, allowing a longer rod and less load pressing into the sidewall.

Rod to Stroke Ratio - Tech - Honda Tuning Magazine

To the poster above... I think we're talking about 2 different things primarily. You're concerned that a stroker engine would be limited in power at upper RPM's due to lack of airflow from the head. I was refuting your assumption of "The bottom end shouldn't have a problem". Maybe for a short period of time it wouldn't be a problem but I do believe the theory of sidewall loading to have some weight here. I think it would be a factor in longevity and make it not desirable to rev a 2.4 to the 9 or 10k you are assuming is safe here. I have a stock car and have only assembled simpler engines than these so I don't exactly have the experience to back this one entirely. However, engineers that are way smarter and more experienced than me do give consideration to rod/stroke ratios when designing an engine so I don't think we can throw it out entirely. I just won't be able to provide a proof for you, in this particular instance. The theory makes sense and I have heard of even stock engine bores being out of round slightly due to sidewall loading. I'm sure components could be designed for the head to flow and make power at those RPM's but I'm not sure the bottom end would be "reliable".
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Old 01-05-2019, 09:26 PM
  #33  
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^^^ You are correct. DavidNJ is over analyzing for fun and lacks some experience with this motor specifically so for him its all application in theory. Square peg doesn't fit into a round hole. Side loading is the primary issue/roadblock when it comes to revs on the F engine specifically, top end breathing from the head is not when you change the cam profile to best match the rpm you want to rev to, within reason. Simply put.
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Old 01-06-2019, 02:29 AM
  #34  
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Originally Posted by Jub View Post
Not what I was saying. Piston speed can be a limiting factor at some point but not the main issue with the typical stroker package. Check this article from super street regarding rod/stroke ratio. This is the gist of why ballade decided to add deck height to the block, allowing a longer rod and less load pressing into the sidewall.

Rod to Stroke Ratio - Tech - Honda Tuning Magazine
Thanks for clarifying, I thought I understood it but now I understand it better Good article. So the limiting factor is the bottom end because of higher piston/cylinder sidewall loading, caused by the longer stroke and shorter rods.

Originally Posted by DavidNJ View Post
Can you side one instance of F24 failure because of piston sideloading? I doubt it.
I cannot for the F24 but there is lots of anecdotal evidence on here of F22's failing that were revved to 9k. The same reasoning applies. For example https://www.s2ki.com/forums/s2000-mo...22c-9k-766676/
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Old 02-21-2019, 07:13 AM
  #35  
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So reading through some of these comments about side load, I decided to sleeve my block for 2 reasons. 1 being exactly that, the extra sideload on the side of the lower portion of the cylinder wall, and 2 well I bought a bare block that had really bad scoring. So it was either sleeves or Bore out FRM sleeves. I decided on steel Darton dry sleeves. I posted in another thread that I was finished with the build/install here is your interested in checking it out.
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Old 02-21-2019, 09:58 AM
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Originally Posted by Ajval79 View Post
So reading through some of these comments about side load, I decided to sleeve my block for 2 reasons. 1 being exactly that, the extra sideload on the side of the lower portion of the cylinder wall, and 2 well I bought a bare block that had really bad scoring. So it was either sleeves or Bore out FRM sleeves. I decided on steel Darton dry sleeves. I posted in another thread that I was finished with the build/install here is your interested in checking it out.
What size bore did you go with? Road racers have done 89mm, drag racers 90mm

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Old 02-21-2019, 10:49 AM
  #37  
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Originally Posted by DavidNJ View Post
What size bore did you go with? Road racers have done 89mm, drag racers 90mm
Well my car is mainly a street car and I kept with stock bore of 87MM. The car runs great so far I have about 300 miles on the block and I’m scheduled to get tuned next Friday.
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