PassionRE

True....But not always a ton of duration. MOST DEFINATELY!!!! Effective drag race engines ,with the exception of 1/4 mile asphalt motors require, the most violent power delivery possible. This ensures peak acceleration, no bog, and the ability to carry gear and tire. This is made possible by the highest possible blowdown pressures at just prior to rated pipe tuned length rpm.....preferrably you want the max blowdown pressures(blowdown pressure by design at desired peak hp output rpm)..to happen approx. 150-300 rpm after tuned length rpm. Blowdown pressures are the regulated by the ratio of transfer total area vs. ex total area...not just the difference in duration heights. The main reason for choosing duration vs. area wisely is effective displacement.(degrees of power stroke before the exhaust port opens). Every 2 cycle engine has a max HP capability based on displacement and rpm where effective displacement is concerned. If you exceed the exhaust duration to the point that effective duration efficiency rpm is exceeded (based on displacment/rpm )you will lose some power, but most importantly, you will lose the abiliity to violently carry gear and tire. You may still make good hp numbers, but the the tq. numbers will suffer badly.....and you just gave up 3 bike lengths in an actual race. The one exception to this is the use of "fly weight riders", or for that matter any means of less drag coefficient whether it be bike/rider package weight, or operation enviroment drag ...such as deep sand vs. asphault ... this changes everything...every engine has to be designed specifically for the intended enviroment, and package weight and tuned length of the pipe...these are the main concerns where duration is considered. 1/4 milers have the room to stretch their legs so big over-rev past rated tuned lenghth of the pipe is less constrictive. The opposite is true in deep sand ,with "normal "size riiders. Big top end motors will get killed by big tq. number engines at near the same peak hp ratings....thus "violent power delivery" saves the day. As far as duration numbers are concerned on transfers and exhaust ports, the most effficient design will vary on casting constraints, displacement, proper tuned length/max rated efficiency of your port layout, not to mention compressiion ratio and combustion efficiency. Every exhaust port and transfer for that matter , regardless of shape and duration, has an exact rpm of peak efficiency. The trick is to know exactly where it is in the design process...even a dyno cannot reveal this most critical information. Using the tuned length spec of the expansion chamber as the guideline , and then matching the max efficiency rpm of transfer and exhaust ports (using desired compression ratio), to falll extremely close to this number, is going to tell you where to set the durations at. And to throw one more wrench in the gears....miss the proper area/duration calculations on the transfer ports and you've just decreased the effects that your expansion chamber was designed around. There is NO magic exhaust/transfer,blowdown duration numbers that are predictable across the board for a variety of engines with even slightly different displacements,strokes,peak HP rated rpms, or intended uses and enviroments. Each engine is a case by case delema if earth shattering performance is the goal. If you take all of these factors in consideration, and a few more not mentioned, in advance< YES, the PERFECT numbers can be calculated.....Bottom line .....absolutely rediculous calculations are required from the very beginning of the build....Jim

Thanks Brad, it's been a long time coming but PRE is my only focus now. I can now devote all my time to my builds and my first love, R&D. Over the last few years my backlogs have become overwhelming, and my turn around times have been less than desired. The day job ,and 50+ hours a week on builds, was about to kill me...Im too old for that much load. SO, screw the day job, Im finnally doing what I do best ....fulltime. After I get over the hump in backload, Ill be much faster on return times, Ill be able to further develop the latest in technology, along with new products for the serious Banshee gear head. Thanks for everyones support over the years, my best is yet to come....Jim

A decent port job, a set of practically any brand pipes and a few smartass comments to get him to line up...Jim

If your idle speed is very stable on the PE-1's the jetting is close enough to launch. UNLESS your over-geared and/or over paddled. What primary's and sprockets are you running? How much do you weigh? The only other thing that comes to mind is a fractured woodruff key, or winding resistance in your stator...that will throw the timing off bigtime....Jim

Hey, watch out ..Ill report you to the admin..LOL HELL YEA!!!!...CANT WAIT

By the time you get a decent crank(10mill) its more than $300.00 difference. I wouldnt even consider using these un-named cranks that are floating around currently...not to mention the TDR or Vito's junk. A Twister crank with TZ drive side bearing would be the minimum in quality that should used on a build thats going to exceed 100HP. Your asking for a disaster on a 10 mill build otherwise. The 4 mill builds are way more forgiving than 10 mills when it comes to crank life..Jim

usually...but not always biggest potential=10mill biggest bang for the buck=4mill

What alky carbs do you have? You have quite a hodge-podge build there my friend...no offense intended. 7mill Cub is a building block for one really intense engine...even stock they are pretty impressive. Single carb makes life easier, BUT at a cost...as in HP. T-5 is probabaly the best 70ish HP 350 duner pipe on the planet...but not a good match for the Cub. You probably should define your permanent direction for the bikes intended use and make adjustments to your supporting hardware on hand to get you where you want to be...Jim

Sorry you had trouble Bill. Between a communication problem on my part and two unsuccessfull shipping attempts from my inept parts supplier, you ended up with a disaster on your hands. On two seperate occasions I thought that whole situation was under control just to be lied to by people I spend a shitload of money with every year...again Im very sorry for your troubles. Wiseco's accuracy is incredible ,any given piston is within .0002 of another of the same size in the modern CNC era. I have a designated micrometer for each size range specifically calibrated for Wiseco products. I can maintain a specified finish bore trueness approx. 8 times better than Yamaha ever did on Banshee engines from the factory...without ever even seeing the piston thats going to be used....Jim

Check into HPTuners and see if your vehicle is supported...... WORTH EVERY PENNY!!!!! It will allow YOU to build the tune, not a lame canned tune... Im pushing 500CHP on pump gas on my 08' Solstice GXP 2.0L DI.. WITH A LITTLE HELP FROM A GARRETT GT-30!! 32MPG OFF THE GAS.... SEEYA' ON THE GAS...JIM

What format engine, IF or OOF?

Yes, we cant wait to get more track feedback, so far its been very good. On another note,one thing not covered much in these conversations is heat release. Some bigger HP cubs, on inframes especially, can make great dyno numbers but the motors are so heat saturated by half track that they are losing power. We can change pipes in pre-production to match exit velocity to displacement and control the rate at which we are letting the heat out. If you let it out too fast, lower HP, if you let it out too slow- "heat soak"-which means even more loss in hp. HP must be made earlier than most drag engines are designed for. Compromised traction is never an answer, Therefore load the engine as hard as possible with tire and gear while still being able to maintain minimal rpm drop going into 4th gear. THIS battle plan has worked best for us. BUT, it requires TORQUE to do this. This set-up doesn't produce the fastest MPH runs, but it will produce the fastest ET runs, which is what counts. Some of the very fastest 300ft engines are outrun by 350ft. Just the way it works, but who cares, 300ft. is what we were after.....Jim

Thanks, the physics demands what they look like, they have to be this big this long etc. to work as well as they do. But I guess when you get the design right on the head, "BADASS" is accurate in EVERY aspect....Jim

excellent!!!!....good match

Yea, its a shame they dont take better care of that track. Most people are not familiar with that track because it's a 500ft run. But,they have a tremendous turnout for some "who brought the horsepower" type racing. I just wish our local tracks had the turnouts those guys get out there. I have to build totally different engines for that particular track. It's not only a tough track to ride on, its a tough track to build for as well. Andrew is a great guy, he's just taking offense to comments on the track I think being talked about as some" hole in wall" nothing track. For its "type" of track it's a premier event. That track is a really good "feedback" track from a builders standpoint. 97-98 mph runs in the ruts?....geeeesh...those guys have the balls, thats for sure....Jim

Top graph shows Sniper +10.12HP & +6.58 lbs/tq. OVER Shearer inframe....Jim

SAME ENGINE ON BOTH PIPES INDEPENDANTLY TESTED AND TUNED BY LONNIE AND ED EUBANKS(SANDTRAX PERFORMANCE) WHILE GARY AND I STOOD TO THE SIDE AND WATCHED PIPES TESTED WITH A 421 CUB WITH NEAR STOCK PORT DURATIONS. (well within the margins of accuracy of standard castings for port timing as normally recieved from CP Industries) ALTHOUGH THIS CUB CYLINDER IS SLIGHTLY LESS EFFICIENT THAN MY MOST CURRENTLY AVAILABLE DESIGNS ,IT IS A VERY GOOD REPRESENTATION OF CUBS BEING SUPPLIED BY VARIOUS BUILDERS IN TIME/AREA AND PORT EFFICINCY RANGES. PIPES WERE ACTUALLY DEVELOPED ON MY HIGHEST END RMS DRAG PORTING THAT UNTIL RECENTLYWASN'T AVAILABLE TO THE GENERAL PUBLIC. UNFORTUNATELY, I DIDN'T HAVE A RMS CUB ENGINE AVAILABLE FOR DYNO TESTING OF THE FINAL STAMPED VERSION WHEN WE RECIEVED OUR STAMPINGS. BUT, WE WERE PLEASANTLY SUPRISED BY THE RESULTS WITH ALL THINGS CONSIDERED. SNIPER ASSASSIN INFRAMES ON GASOLINE 421 CUB DYNO SHEET HERE IS A DYNO SHEET OF GAS VS. METHANOL ON THE SAME ENGINE BOTH RUNS ON SNIPER ASSASSIN INFRAMES. THIS TESTING IS INCOMPLETE DUE TO THAT NO ADJUSTMENTS WERE MADE TO IGNITION TIMING OVER THE GAS TUNING SESSION. ALSO, WE WERE UNDER DIFFICULT TIME RESTRAINTS AND DIDN'T ADJUST FOR PROPER COMBUSTION WHICH IS NEEDED FOR A ACCURATE METHANOL TEST. THIS ENGINE WAS ON LOAN AND I WAS CAUTIOUS ON THESE RUNS FOR THE FEAR OF DAMAGING THE ENGINE. HIGHER TORQUE READINGS ARE A CERTAINTY WITH PROPER IGNITION TIMING, SQUISH VELOCITY, FLAME DURATION, AND FLAME SPEED CORRECTION. THE RESULTS LOOK PROMISING TOUGH CONSIDERING THE STATE OF TUNE.

Dave, I lost my hard-drive a few weeks ago but I managed to find this one video clip of Gary (Sniper Racing Products) on his Passion 421 Cub. This is what traction and the ability to pull tire and gear will do for a 421cc Cub. Gary's bike is light, but he's not. Rider/bike combo weights are pretty close on this run. Both Bikes are Cubs with OOF pipes. The run itself is actually a bad run for Gary, but the fact that it is such a bad run really is what makes it so impressive. Gary bogs out immediately and recovers well. We rejetted later to eliminate the bog, and actually did the very first real-runs on the Sniper OOF's later that day. Just wish I had video of the runs later that day, impressive is an understatement. This run is with Shearer OOF's. We were just messing around for tuning purpouses, not a real scientific track by no means, but a blast just the same....Jim Gary's Cub run

Weve been running at Tulsa's new track, hopefully they will say in business, support can be lacking at times. last time we ran Gary took everything. We also run at Whitefield, the true test of any drag quad. yes Dave, you can NEVER decide on the side of tire slip and expect to have a winner. As Tom Turner said to me personally," you cant break world records with compromised traction". he should know, he held the world record 400cc 1/4 record for 14 years. If your are built and tuned and set up properly you will have a 300 ft drag bike. Who cares what happens at 325ft, the race is already over. the main problem is that MOST 400cc bikes wont carry that gear. Goes back to that power UNDER the curve. Top end tuning is useless in high drag coefficient enviroments. On another note Dave, hows that 10mill engine coming along? Gary and I are anxious to hear feedback on the Sniper OOF hybrids....Jim

Either of these choices will require port alteration unless your going for the TURD motif...especially the big bore. Dont waste your time on the big bore or the Vito's crank, you'll wish you had that cash later down the road when your just disgusted with the outcome or torn down constantly. OEM jugs with sound porting and a quality 4 mill long rod have the capability of outrunning even some built 421 Cubs if your builder stays away from wives tales and uses real science instead....Jim

If your in a position of only being to do one or the other at this time, go for the over-ride. Once your on meth and tuned properly, you wont be able to shift that engine anyway due to the high loads on the trans gears. You'll probably need to upgrade to a lock-up eventually after meth, clutches wont handle the stress...gee...the fun, or is the addiction of HP, just never ends! Meth makes power earlier, higher torque numbers, and will >>>>>>> carry a "lot" more gear and tire.<<<<<always a good thing...Jim

Joe, not sure if the wife took the wrong number or what, Ive left 2 messages for you...PM your correct # and Ill call you tomorrow. Yes Joe and Cody, I will have the proper modifications to the base Sniper to work correctly on both your engines very soon!! Due to the smaller displacement than the original design criteria, minor changes are being made to sync in on all my drag and dune/drag OEM series cylinders! This mod change will also work excellent on F.A.S.T drag series stock OEM cylinders as well. Joe , just imagine all the hit of the CPI and and an extra 800 rpm, not to mention all the added horses. Cody,you can expect just sick power everywhere over where your at currently.

Yea Yea, I was just lucky to get it mocked up before Gary caught me in my underwear that morning... He was a little ancy to get the photo's shot that morning......for good reason though. I thought the pics turned out pretty good for a amateur. As for tuning pipe to pipe. One thing to remember, at least from where I am in opinions on this matter, the pipe changes themselves within themselves IS a tune change. This holds true to alot of just normal bolt on stuff. The only way to verify performance accurately is to tune for whatever you can get out of the engine with each set of pipes tested. And thats just tuning for power output. Many opinions exist on gearing and tire selection as well...thats for sure. Seems everytime Gary and I show up with 16 paddle Ripppers on our 421Cubs....everyone has to blurt out "sure you guys brought enough tire?" Then as usual, we procede to show them we made the right choice...LOL...Jim

Save money and do it once. Buy the VF3's and never look back. Excellent response and good to 120 HP if you ever upgrade to Cubs whatever down the road. Earlier VF's are good performers but tend to let loose of screws. Plus if your porting is out of sync with your pipes, they can get warped from the added heat. Just keep an eye on your reeds through occasional inspection. Lower compression engines tend to raise exhaust temps and turn more RPM. Therefore the reeds take a beating. Although the natural frequency of standard VF reed petals is above 10K, they don't like much more RPM than 9500RPM.They tend to crack on the edges with excessive RPM..Jim