Thank you for confirming (via dyno) something I've been working on in the conceptual stage, namely the effect of intake cross-sectional area on intake charge velocity, and its' effects on horsepower at various RPM levels.
This is more than velocity/flow. This test also shows the impact on runner diameter and the strength of the pulse waves being diminished as the cross sectional area increases. Super super interesting.
i read a reasearch paper stating that a bellmouth shaped like the valve cuts (3 angles ) but not full bell mouthed , not rounded over , gave the best flow. thatd be interesting to see also.
I'm loving all the data you are producing. And the road speed instead of time as an X demention is messing with mysilly selfff. It's a happy little shifty loop de loop.
Really nice channel! After i watched your video i scrub my airbox out ofmy civic ej9 and made the air intake hole bigger with sandpaper... plus bigger airintakte in stock airbox and k&n filter.. it goesreally good now! But was so god damn loud now cause i had no holes for the resonance box.. after i drilled one into the air intake the noise sounds legal under 3000rpm:D
About what I expected to see with the 40mm, more midrange due to increased velocity, but less top end due to restriction of flow. Would be interested to see a test of the tapered versions with different rates of taper. Im sure there is a text book somewhere that has a formula that would allow you to work the ideal rate of taper for a given flow and velocity...but this is more fun!
Will definitely do something trying different tapers in the future. Since the 51-62 was the only one that had a power gain without a loss somewhere else. At very least will bore my normal intake out with a more aggressive taper.
I’ve read before in university research studies on the subject of taper angles that 3 and 7 degrees is the best, 7 being the best over all and 3 close behind it. Angles close to them either side had drastic changes like what we’ve seen in the intake length tests
Man this is my favorite channel even though I have no love for the 4age lol. I know on my rx7 I was able to find a good bit of power using taper exhaust runners. Now I know the pulse is much stronger in a rotary but I'd love to see what it does with this.
Tanx and congratulations for sharing all these videos! I'd like to suggest a comparison between wasted spark and full sequential ignition, keeping same timing map and voltage and energy output. If you find it interesting I may help you to do it.
I'm curious what you know about tuning. All I know is with intake design there certain frequencies that can be targeted. Frequencies corresponding to engine RPM and how pressure waves are created at every valve event. Would love to here your thoughts on the topic!
nice vid, thanks for putting it up. in essence, for your application there was very little downside of going larger, especially if the application lets you stay in the upper rev range. Ive been doing some work with sr20ve engines but would love to have the dyno access to do what you are doing
I just bought a 75mm length velocity stack and with your informational video. Now i know why i got more acceleration on my 150cc motorcycle. once i got pass at 8.5k rpm the engine just suddenly gains extra power and reaches redline much faster at 5th gear, although my top speed is just 147kmh but hey my bike weighs 135kg and I am 67kg. its a great win in that situation.
@@stoosee no, it is a chinese bike skygo knight 150(carbureted) . But its already upgraded with an 8 stage Racing CDI, 7.0 lift camshaft, 30mm flat carb, stage 2 exhaust manifold, modified pipe and a semi dome piston.
@@zainrei4917 i have mio sporty, engine specs are 59mm chromebore mtrt bigvalve 30/25 regrind cams 28mm carb cvt set: sun df rrgs pulley straight 8g flyball 1500rpm center spring 1200 clutch spring modified torque drive for more top end 17s rim i need to change exhaust cause cause my current pipe doesn't fit to my engine spec
I'm not sure if its a velocity thing from the taper. thinking maybe airflow. since can clearly see the smaller diameter runners bottle neck at a certain rpm. the 51 and my normal intake are just hitting it right up top
@@Garage4age True, but in all my cylinder head experiments, a 1.1:1 taper has produced best intake velocity at the valve, and best cylinder filling (and best power curve on the dyno). Love your videos!
@@dragonhealer7588 Yeh not saying you are wrong. this thing proves me wrong every time i think i've figured it out. so now i just test stuff and if it works it works. My normal intake does have a small amount of taper in it. the bellmouth is very similar to whats used on these tests. so the 51mm vs normal intake runs in this vid is a good comparison, the normal intake hangs on a bit longer. although the tapered runner maybe acting bit shorter, even though overall length same. at some stage i will bore the normal intake out with a more aggressive taper, see if it does the same as the 51-62. getting the sweet spot may require a few attempts.
Hi, very great videos, I think probably unique because never saw so much work documented in this way. Hope you will never get bored and will continue to do this! What is the diameter of the throttle bodies that you're using? Also the diameter is measured at the end/beginning of the body itself or at the butterfly? (sometimes for example it's maybe 38 - 40 mm but the butterfly inside is like 36mm, so I don't know what diameter it's considered really)
The intake air resonance (= cyl fill = power) is related to the intake duct volume (it behaves as an air spring). If you test options with same duct volume (e.g. 165x51 ; 120x60; 140x55; etc etc) you should be able to sweep wave and friction effects at same air inertia (air kinetic energy) levels.
Can you do more dialed test on reducing diameter "taper" runners? Like higher reduction in diameter per distance and lower, what effects will it have? Like 50-45 reduction in 200mm length vs 70-45mm reduction in 200mm, and like 70-45 in 100 mm(steeper angle), you know? Something like that would be greatly appreciated.
Hey, Yes I want to figure out what will work best after seeing what the big 51-62 did. Just need to figure out an easy way to do a fair test. in the meantime my normal intake has a small taper out to either 54mm or 56mm will have to measure to be sure. so the 51mm straight vs normal vs the 51-62 from these tests is worth a look for comparison
@@Garage4age sounds clever to me. Because what I noticed is that straight pipes give that resonance "supercharging" ram effect, torque climbs, then it gets to opposition and destroys it and makes torque dip in the rev range. So nice taper would yield perfect results from low down to up top. Also won't you think tapering down to lower diameter (let's say 45) give more on lower rpm torque?
@@gedas3419 Going down to smaller diameter like you suggest may work. longer the pipe, more restriction. So a short section 45mm may not pose a restriction at high rpm like the 200mm length in this test. should be worth a try!
Need a pressure valve to control air volume , too much air good at hi rpm but Low to mid is bad , German technology already tell us , most of the modern car with pressure control manifold to compensate the needs from engine
can you test throttle body "spacer" it has grooves that makes better air/fuel mix, i am a little skeptical about it but when i put full gas pedal on low rpm and let it to rise(3000-4500) when i start to release gas pedal from 100% to 85-80% i regularly feel increase of power, explanation would be that butterfly is too opened for some rpm and if release it, it starts to make some turbulence that helps to mix air/fuel
@1979Olitsch it would, that's exactly what most if not all production cars do these days, not seamlessly ofc. but with 2 runner lengths adjusted with flaps.
Cylinder 1 should have the shortest trumpet working along making each trumpet longer until the 4th cylinder is at full length. Cylinder 3/4 will always have more fuel sprayed into the itb than cylinder 1/2 it won't be much but it's enough to cause a flat spot or lack of power with equal length trumpets due to atmospheric pressure. The theory is cylinder 1 has the shortest trumpet and cylinder 4 the longest. We studied this and documented all data for Motorsport with the engine sat transverse like your motor you should try this and see how it works.
Hi. I have avoided running different length trumpets, as would have to run a different tune per cylinder. A lot of people have asked to see it, so may do it at some point. but cant see the advantage, based on the testing I've done
A larger bellmouth should be equal to a slightly longer stack, but a good bellmouth will increase the effective rpm that you get power gains from. Almost all of the gains that you see are specific to a rpm because it's mostly tuning the frequency for a specific speed For instance look at the design of the factory pro superflare velocity stack design compared to there normal one. You can also try using 2 longer stacks tuned for say mid rpm and 2 shorter stacks for high rpm power, oems use that mix alot. Depends if you are looking for peak power or lifting the whole power curve
In my other video where I tested length and some different bellmouths. the bellmouth pipes act like a shorter pipe. If adjusted the pipe so the effective length is the same, the power curve will look the same, no bellmouth vs bellmouth. But the bellmouth pipe will start to beat the non bellmouth once airflow demand increases. judging from what i've found so far, and ignoring the complexity. A 2 stage setup running a small diameter runner in the correct length at lower rpm's then switching to a big diameter pipe for the high rpm would give the best overall gain
@@Garage4age yep newer Yamaha r6 motorcycles have electronically variable stacks. They have 2 different positions. It causes a 500rpm or so area in the meat of the power band to be down on power during the switch tho. Most other motorcycle manufacturers haven't switched to similar systems because of complexity and they don't feel it was worth the gains. Suzuki still uses 2 longer stacks on 2 cylinders and 2 shorter on the other 2. There is calculations you can run to determine the optimal length, depending on where you where in the rpms you want the power gains, but testing is always good. You are right about bellmouth needing to be longer, I realized when I looked at the factory pro superflares again vs the normal ones. From your testing, it looks like your stock motors design is tuned rather well for your motor. Yamahas factory stacks use the taper you tested, aftermarket typically uses a large bell mouth.rounding the edge of the bellmouth is done on designs I have seen also. I don't recall if you tested it yet, but I would think a bellmouth with a taper would be best. Just gotta get the length perfect. I'll have to rewatch the older video, I would think the airflow demands of your motor would be high enough at the top of the rpms to benefit from a bellmouth
The different length trumpets should be good for smoothing out the powerband. kinda trading power in one place for another. Bit of a pain to tune as have to tune individual cylinders. i could blend 2 of the dyno graphs together from all the tests i have done to show what 2 long and 2 short would do. so not really worth doing it physically. The last runners in this video are tapered. 51-62mm, they are also the only thing that has beating my normal intake without loosing power somewhere else. said normal intake is far from stock (these engines dont even have itb's stock) and also has a taper in it, but less aggressive taper than 51-62. has an elliptical bellmouth. probably some better pics of it in my other vids
Nice, I dont think the 51mm is too large though. I would prefer the nicer power curve with that extra up top. Don't like the peaks and dips that the 40 and 45mm's create. but its possible the step down is doing something funny to produce them.
@@Garage4age what size is the runner after the throttle/before the port? Had a play there? I know when I looked into ITB for my SR20VE I gave up, because the only options that would've provided a nice linear power curve were BMW 52mm+.
@@NicPerichon it used to have blacktop 4age throttles with 47mm throttle plates. and manifold to suit. it ran the same trumpet setup as current but the 100mm section between throttle and top half of trumpet/bellmouth had slightly more taper due to smaller throttle size. the power curve was identical when switched to the bmw 52mm throttles. so they are oversized maybe yes. but the bmw throttles do sit a bit further from the head, so its not as big of a change as it sounds. but still had zero effect so havent bothered revisiting it
Variable is cool and have attempted something in the past. But there is a lot of complexity and engineering feats to overcome for little gain. Going by the tests i did on length in my other video the longer runner beat the shorter ones almost everywhere. Almost looks like variable diameter would be better than length
Cool. Love your style. One note tho, I know it's a pain and takes time but you really should re-map every time you change An item. just to see which would be better.
I do at least one run before the runs you see in the vids, to correct afr if required. ignition advance is kept the same. but end of the day, since its alpha n tuned. if goes richer = power loss. leaner= power increase. there are of course a few exceptions to this.
@@Garage4age it's rather pointless, as the torque does not change enough, even with very bad a/f ratios. Afr is important for emissions, engine health ( especially for force induction) and economy, but as is stands for torque, from ~9:1 to ~16:1 is pretty much the same. What's important, is the good enough atomisation and homogeneous mixture, but second to the volumetric efficiency tho..
@@TheSilviu8x yep I have a video showing how little change in power there is within a afr window. If is within a certain range I generally don't bother correcting afr for most tests. But yeah if it's a final tune needs to be right for other reasons
would need to do a whole new build to get it up to this ones spec, different pistons etc. I do have a near stock 20v in another car i may do some testing on though
The 51-62 mm is the best scenario in this video, but isn't the removal of the air filter contributing a part of this gain? Do you have an estimate, or have you measured in the past the gain of removing the air filter on your engine setup?
@@Garage4age Impressive, especially in such setup that removing the filter makes no difference! I assume your filter is foam based? Have you also tested any fuel additives?
You are correct. IMO the big tapered runners are the best. No losses anywhere whilst having a gain right up top. I will try to replicated the steeper taper angle on my normal intake
@@Garage4age I’ve been making carby intakes from pvc tapered 50-75mm with a bell mouth 120mm long. Would you like to try these if I send you them ? I could also lengthen them to your normal 185 or 205 so you can see if added length could possibly be better with a taper compared to your already tested straight sections.
@@Garage4age no worries, I’m making more of different lengths over the week end so I’ll get some done in those sizes so you can see exactly what they’ll be. I’ve just been researching the yoshimura double velocity stack, very interesting with mixed results. From what I’ve read a 1mm gap difference between the velocity stacks make or break the gains so for you to test it would probably take to much time setting up and trialing. Love your channel man, I’ve learnt so much and confirmed so many ideas from all your experimenting. Me and my mate were doing similar sort of tests with ic piping and intercoolers but for now everything has had to stop, your channel pushes me to get back to doing it again.
so inlet surface for 2 inlet valves is (pi*D*h)*2 = 1947mm2. Inlet surface of a trumpet is pi*d*d/4. So inlet trumpet should be at least : 1947=pi*d*d/4, so D should be 49mm minimal. Usually should be 10% higher. 1947*1.1=pi*d*d/4 --> D=approx 52mm
remember its only a 1600cc. Also the difference between 40mm and 51mm at peak power is over 10% That's a big difference from just a bit of pipe 200mm long in a different diameter.
@@Liveforeever Pretty hard to say. things like cam size and overlap will likely have an effect. The exhaust side can have a big impact on how things work also. but in a perfect world i would assume the 10% would carry over, if everything is relative to the engine size.
Yeah half the reason i made this video. But tbh I had never tired downsizing the runners so was curious. From what i can tell, big gain down in the low/mid range people have got with smaller diameter runners, is fixing a reversion issues by speeding up the air coming in, so the exhaust gas cant get back in the cylinder. my engine i fixed the issue on the exhaust side. which doesn't result in the big loss in power at high rpm. Its very common on these engines to have a big power dip at 4-5000rpm after installing big cams.
@@africankat1 BMW throttles. it used to have blacktop throttles with 47mm plates. Power wasnt any different going to the 52's but stuck with them for a few reasons.
This isn’t ideal because your dealing with air transfer over a drop off in the back of the runners. Anything over a 7 degree angle will cause air to tumble so of course at high rpm the size difference the power loss will be greatly exaggerated on smaller runners. You’d have to different runners every time with a proper transistion. You used pipe with the smallest lip on the last run so of course it worked.
It actually doesn't matter as much as you would think. the runners at the end actually have a worse transition that the normal baseline run. Its pretty clear the smaller runners are running out of airflow, even if there is some small "tumble" effect. to fix the transition. would have to modify and fill all the way down into port, but then wouldn't really be apples to apples test anyway.
@@Garage4age in another video, with the 3D printed velocity stacks, it looked like you solved it with the tapered intake. Having the small end gasket matched to the intake on the head. Both Intake and exhaust runner length make a difference too, which I’m currently trying to wrap my head around all the math.
I’ve basically got to build intake with longer runners and bigger plenum and have shorter shorter extractor? runners so can get the best of both worlds
@@ajisw_324 yeah, this engine will make the same power on 47mm throttle plates, but any smaller no. Ive kept the 52mm ones on there for other reasons, even though they are slightly large
@@Garage4age well then i remember ducati v4 use 52mm throttle body aswell, 81mm piston same with 4age. Make 215 HP on crank. Yeah i think that's not too big
