bluegas68

This whole thread here (https://www.s2ki.com/forums/index.php?showtopic=427926) got me thinking. What actually are the limiting factors of making a 9K AP2? The most obvious is the rev limiter, but thats electronically controlled. Im looking for the mechanical limits. Im just wondering if you did the valve spring/ keeper ungrade to avoid floating the valves, is that pretty much it (other than moving the redline up to 9 from 8). Is the concern that the bottom end cannot take these revs? Anoter argument is that "Ok, so you make it rev to 9, but you arent making anymore power after 8ish anyway.", but does anyone know that for sure? After all, if the limiter kicks in how can you really measure power after the fact? It FEELS like it pulls all the way up 8 and then the limiter just gets in the way. However, if the limiter was not set at 8 , would it continue to go another 1K and still pull as strong, as in maybe Honda was just covering their ass by lowering the redline onthe AP2. I have located 2 clusters, but unless I can really get it to 9 and it be better and beneficial, then I wont bother. I dont wanna be no poser...all show and no go. What do you guys think/ know?

Lionheart

It's also about the distance the pistons travel each second, they have a limit too.

One of the reasons the redline was lowered by about a thousand revs on F22 because of the increased 0.2L displacement..

__redruM

The Ecu could be reprogramed or replaced (not sure which) to allow a higher rev limit. But only experimentation will tell you what the highest safe redline is. There was another thread floating around titled something like RIP AP1, from a 3-2 mis-shift. The AP2 might have the extra room for a reason.

The main difference between the AP1 and the AP2 is the bottom end. Honda certainly didn't weaken the head to drop the redline. They lengthened the stroke. You might have to do something in the bottom end as well to raise the redline. Though I do believe that some AP2 owners are running a 9k redline, just not sure what they did to get there.

bluegas68

Is the displacement increase due to a bore increase or a stroke increase? Does that matter (if its one or the other i.e. 2 engines with indentical bores should be able to rev the same even if the stroke on one is longer, or only one with larger actual piston will not be able to rev as high)? Then would the limiting factor simply be stronger or lighter or both connecting rods. I know there is a magic number, but not sure of the formula, just wondering how close Honda actually made the tolerances. As in F1, im sure those engines are larger than 2.2 and they rev WAY HIGHER than 8K.

bluegas68

I thought that was usually from valve float and/or the keepers giving way (which they have upgrades for)

DaveOnLI

F22 has increased stroke and therefore has higher piston speeds. There are a few people that have AP2 engines running AP1 ECUs which take them to 9000 RPM. However the power does drop off somewhere after 8000 and does not continue to climb to 9000.

bluegas68

Could that drop in power be because of ECU parameters differing (mapping, timing, etc.) from 2.0 to 2.2? I hope you guys dont think im second guessing everything you say, im just trying to find out as much as possible...thanks to all for you input!

vishnus11

Although, I agree with the fact that Honda had to drop the fuel cutoff from 9200 to 8200 due to the increased stroke, the drop didn't have to be that significant. There's a thread floating around on acurazine.com which details the production cars with the highest piston speeds. Of course the AP1 S2000 is at the top with something like 4795 ft/sec. However, the AP2 exhibits a lower piston speed, and I don't see why it does. If anything, it should have a similar piston speed to the AP1, which would put the fuel cutoff somewhere between 8200 and 9200rpm.

I believe that this is one of the reasons why Hondata felt confident in bumping up the fuel cutoff of the AP2 from 8200 to 8500rpm. 8500rpm on the 2.2 would probably produce similar piston speeds to 9200rpm on the AP1.

My advice would be to figure out what rpm in the AP2, gives the same piston speeds as in the AP1, and then bump the redline up to or around this area, and then adjust the fuel/air maps to compensate.

Or just get Hondata.

MULDER

We have been this route before...

https://www.s2ki.com/forums/index.php?showt...hl=piston+speed

If you wanted to rev to 9K, you should have bought an Ap1.

suprfunguy

I do know for sure that the AP2 doesn't make any more power after 8200 RPM. In fact, if you change the car to rev past 8200 RPM (by using an older ECU or stand alone management) the power continues to drop all to way to 9K.

Here's a link to our "Dyno Day" where we tested two AP2s. Allegheny Club Dyno TestMine had a Comptech Supercharger installed the other had light mods with an AEM stand alone set to 9K RPM. Since I was plannig to run an AEM unit (set to 9K) with my supercharger, I was very interested in the result. However, after the dyno runs on the stock car, I can't see any "dyno" proven benefit in doing so...