Frankenstein H23A prelude Si conversion

[PreDaToRPrelude]

Read some of your msgs, and it seems like u guys DO know ur stuff (preludes kick ass) hehe. Recently, i converted my Si 2.3l keeping the bottom end whilst mounting a 2.2l DOHC VTEC head w/VTEC pistons. Luck was on my side when the whole thing was complete andi managed to start the engine, however the stock H22A VTEC ecu kept limiting itself out at 6500rpm. I knew something was definitely wrong as a mate of mine's prelude redlines at 8500rpm (stock). I tried various chips including a SPOON chipset, but that didn't seem to work. Finally, when i came to the KS chipset the rev limit jumped to a monstrous 9000rpm, however there seems to be lack of power towards the bottom end and some slight backfire. Anyone have any suggestions as to why it is doing this? (A last word of note, my Si seemed to be quicker)

[lewd43]

first off, i think the swapping on the vtec pistons into the h23 block is the problem with your low end, i know that the block is where torque is made and the head is where horsepower is made. I dont know what the specs on the vtec pistons are or what the h23 pistons specs are either, but if they are smaller which i believe they are, i think you might be experiencing "blow-by" (air passing the piston and losing compression in the chamber) which could cause some performance problems, i'd say put the h23 pistons back in and see what happens. One tech question, how did you solve the oil supply issue for when vtec kicks in, i have a 4th gen se prelude(h23) and i was thinking about doing this, turbo, or jdm swap

[cullude]

first off, i think the swapping on the vtec pistons into the h23 block is the problem with your low end, i know that the block is where torque is made and the head is where horsepower is made. I dont know what the specs on the vtec pistons are or what the h23 pistons specs are either, but if they are smaller which i believe they are, i think you might be experiencing "blow-by" (air passing the piston and losing compression in the chamber) which could cause some performance problems, i'd say put the h23 pistons back in and see what happens. One tech question, how did you solve the oil supply issue for when vtec kicks in, i have a 4th gen se prelude(h23) and i was thinking about doing this, turbo, or jdm swap

The size that would cause a blow-by is the only thing that is the same on those two pistons (87mm). The diffrence between the h22 and h23 piston is that h23 is a dished piston (less compression) and on an h22 piston the dish is reversed (more compression), also the distance from the wrist pin to top of the pistons is about .05" different on those two pistons. If you are using h22 pistons with rods, there is also about .05" diffrence in length between the wrist pin and bottom of the rod. Now, if you would try to put h22 pistons with rods into an h23 block with h23 crank, your piston would come up about .1" above the deck and probobly hit your valves, unless you used a thicker head gasket which I don't think would be too safe. What you would have to do is replace the crank also so your stroke would lower and bring the piston to TDC a little lower. Ok I'll stop now....Good luck to whoever is doing a swap like that... Later...John.

[SilverLude001]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by PreDaToRPrelude:
however the stock H22A VTEC ecu kept limiting itself out at 6500rpm. I knew something was definitely wrong as a mate of mine's prelude redlines at 8500rpm (stock). [/quote]

dude no stock prelude revs to 8500

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by PreDaToRPrelude: Finally, when i came to the KS chipset the rev limit jumped to a monstrous 9000rpm, however there seems to be lack of power towards the bottom end and some slight backfire.[/quote]

9000 rpm on a stock head would soon cause valves to float

2001 Satin Silver Prelude