bansheeqc Posted July 21, 2008 Report Posted July 21, 2008 This week-end, I port my piston on my stock crank drag banshee. I enlarge the window to fit with my cylinder intake. On my Trailtech vapor, i saw a gain of approx 800 rpm after the piston windowing (11300 rpm actually) . I do a couple of pass on the track and my bike ran good, but need more fuel. I change the jetting, I jump 165 to 175 (keihin aa jet) and my bike run very good on the track. I tested my compression and my compression as droped to 155 lbs both cylinder (before, i'm at 190). My questions: it's possible, it's just the piston window retarding my engine before? it's normal to gain rpm? it's normal to need rejetting and it's normal to drop off the compression like this??? I actually run t5 on this bike, put i think to try my shearer inframe from my stroker. I think with this rpm range, the motor, run great with this pipe. Quote
bansheeqc Posted July 22, 2008 Author Report Posted July 22, 2008 any as try this or any answear? Quote
jbooker82 Posted July 29, 2008 Report Posted July 29, 2008 Bigger ports = less velocity so your probably not getting as much air in to the motor. Or the skirt broke and that caused the compression drop. Most people dont opean the windows of the pistons up because it weakens the skirts. There is no way your turning 11300 rpm with T5's Quote
okbeast Posted July 29, 2008 Report Posted July 29, 2008 Bigger ports = less velocity so your probably not getting as much air in to the motor. Or the skirt broke and that caused the compression drop. Most people dont opean the windows of the pistons up because it weakens the skirts. There is no way your turning 11300 rpm with T5's I'd mostly agree on not hitting 113XX with T-5's unless there is some wicked porting or some phenomenon inside ur motor. As for bigger ports not getting you as much air you can't really say that b/c a bigger port will allow more volume in, it's kind of a trade off, but I'm not sure where the breakover point would be. Quote
shanYE west Posted July 29, 2008 Report Posted July 29, 2008 with the bigger ports you'd loose velocity. Since your loosing velocity you'd pick up less of a fuel charge and would cause the need for bigger jets.. I'm not a builder.. but thats my experience with it. I've had a few motors done and the motors with the bigger intake ports always used bigger jetting. :shrug: Quote
bansheeqc Posted July 30, 2008 Author Report Posted July 30, 2008 I solve my compression probleme. My compression tester as a probleme. I'm actually at 180 psi both cylinder. My bike are now jetted 185 and run very hard. Yes my engine rev at 11300 with supreme gaz+nitromethane , but drop a 10800 with avgaz 100LL. I try shearer this weekend, and, my max rev it's at 11500 rpm (shearer inframe). But with T5 pipe, my bike do best run. My motor as some big port and are dynoed at 80 hp on gas. I probably try alky next week-end. jbooker82: Bigger ports = less velocity so your probably not getting as much air in to the motor. Or the skirt broke and that caused the compression drop. Most people dont opean the windows of the pistons up because it weakens the skirts. There is no way your turning 11300 rpm with T5's It's common to broke the skirt of the piston with larger piston hole?, I dont know a lot about piston window, but i'm thinking all builder open this window... Quote
shanYE west Posted July 30, 2008 Report Posted July 30, 2008 I solve my compression probleme. My compression tester as a probleme. I'm actually at 180 psi both cylinder. My bike are now jetted 185 and run very hard. Yes my engine rev at 11300 with supreme gaz+nitromethane , but drop a 10800 with avgaz 100LL. I try shearer this weekend, and, my max rev it's at 11500 rpm (shearer inframe). But with T5 pipe, my bike do best run. My motor as some big port and are dynoed at 80 hp on gas. I probably try alky next week-end. jbooker82: Bigger ports = less velocity so your probably not getting as much air in to the motor. Or the skirt broke and that caused the compression drop. Most people dont opean the windows of the pistons up because it weakens the skirts. There is no way your turning 11300 rpm with T5's It's common to broke the skirt of the piston with larger piston hole?, I dont know a lot about piston window, but i'm thinking all builder open this window... Take a picture and show us what your working with.. are you talking about piston windows or the main intake ports of the cylinder?? I'm kinda confuesed now... 80hp on a stock motor with T-5's? Quote
flotek Posted July 30, 2008 Report Posted July 30, 2008 well i build banshees for living and i cant see that A your not making 80 true rwhp horsepower or hitting a true 11,300 rpms by use of a stock stroke and just toomey T5 exhaust and adding large windows to the pistons can start the charge a little sooner giving slightly better lowend response but your not getting any big gain or hp increase ,it will crack and is no benefit ,large intakes reduce velocity and dont always benefit the other portwork .theres a relationship that must be kept Quote
bansheeqc Posted July 31, 2008 Author Report Posted July 31, 2008 lol, it's not just my piston ported, but my cylinder also It's on my stock stroke dag bike, with heavy ported cylinders. but my piston are stock, and i decided to port the window of my piston to match my intake port on my cylinder. Quote
okbeast Posted July 31, 2008 Report Posted July 31, 2008 lol, it's not just my piston ported, but my cylinder also It's on my stock stroke dag bike, with heavy ported cylinders. but my piston are stock, and i decided to port the window of my piston to match my intake port on my cylinder. yeah we get it. there's still no way you're hitting 11,3xx with T-5's. Send Snopicynskarooski or w/e the hell his name is a message and see if he has any dyno charts with T-5's, I highly doubt any of those bikes hit that high of RPM. Quote
bansheeqc Posted August 1, 2008 Author Report Posted August 1, 2008 i think it's high for T5, but my vapor show 11300 with t5 and 11500 with shearer. If shear show 12000 rpm, i think my vapor it's not correct, but at 11500 i think it's okay..Why my vapor could not show the real rpm with t5, but the real with shear?? Quote
flotek Posted August 1, 2008 Report Posted August 1, 2008 lol, it's not just my piston ported, but my cylinder also It's on my stock stroke dag bike, with heavy ported cylinders. but my piston are stock, and i decided to port the window of my piston to match my intake port on my cylinder. okay ,fair enough .. but lets see the dyno graph plot to prove this cause i have never seen toomey t5 pipes hit that high and pull at 11,300+ rpms ,the exotic port is one thing but the exhaust pipe has a given effective rpm range and the exhaust must match the port durations and layout . toomey pipes are not known to make much over 9,000 rpms without signing off so we would love to see this shown Quote
dajogejr Posted August 1, 2008 Report Posted August 1, 2008 And a Shearer pipe only making 200 RPM more than a Toomey? Ah...no. Here's a 4 mil cub cylinder with T5 pipes and stock carbs. Now I fully understand that bigger carbs would increase the RPM on this motor (my motor back in 06, before I got shearers and 35 PWK)....but you can't tell me T5s on a stock cylinder even with good porting are gonna pull that far...(the broken line is with a bad flywheel, magnets busted up, btw.) Quote
bbcmudtruck Posted August 1, 2008 Report Posted August 1, 2008 Snopicynskarooski :yelrotflmao: Thats a cool dyno read out with the broken flywheel too. Quote
bansheeqc Posted August 1, 2008 Author Report Posted August 1, 2008 but why my vapor show 10xxx before and 11xxx after? Why i gain rpm with windowed my piston? Same engine,same pipe,same gas... Quote
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