Calculate Your Compression Ratio

Рет қаралды 284,088

Күн бұрын

This is everything you need to do to calculate your compression ratio. No foolin'. Every equation and process demonstrated. Find all your variables. Know your exact compression ratio in every cylinder. This is how you do it.
Just because your service manual says your car is 7.8:1 or 8.5:1 compression doesn't mean that it is. Whenever there are casting irregularities, variations in piston height, parts that have been machined, non-OE parts, or changes to your head gasket selection, your compression ratio WILL change. It's highly probable that you're only CLOSE to spec if you've never touched your engine at all since it was "born", and that it doesn't MATCH spec. Even if it did, how would you know? This.
5 variables.
V1 Swept Volume
V2 Deck Volume
V3 Piston-to-deck clearance
V4 Piston dish cc's
V5 Head combustion chamber cc's
The ratio math:
V1+V2+V3+V4+V5 = volume of combustion chamber at BDC
V2+V3+V4+V5 = volume of combustion chamber at TDC
The ratio is...
(V1+V2+V3+V4+V5) ÷ (V2+V3+V4+V5) : (V2+V3+V4+V5) ÷ (V2+V3+V4+V5)
or
BDC ÷ TDC : TDC ÷ TDC
First you fill in the variables, then you calculate volumes, then you add the volumes, then you reduce the ratio (fraction). It's that easy.
Here are your magic numbers:
0.7854 = Pi quartered to the ten thousandth
16.387 = number of cc's in a cubic inch.
If you divide any number in cc's by 16.387 it gives you inches. If you multiply any number in cubic inches by 16.387 it gives you cc's.
Quartering pi lets you use the calculation:
BORE x BORE x STROKE x .7854 = volume of a cylinder
instead of...
π x (BORE ÷ 2) x (BORE ÷ 2) x STROKE = volume of a cylinder
Either way is right. You get the same result if you calculate pi to the ten thousandth. While I apologize for all the math, no I don't. I'm really not sorry. You actually clicked here for it whether you realize it or not. This is ALL the math, the tests, and the whole process to calculate your cylinder volumes and compression individually even if you don't know any of your variables yet. All of my numbers are present for those who want to calculate out the last 3 cylinders out of curiosity just to see how it affects cylinder volumes and compression ratios from one cylinder to the next. Why would I do that for you? Why would I deprive you of that practice?
Just assume that all 4 of my combustion chambers are 41.75 ml if you do this.
Clicking like share and subscribe helps a channel grow. It also motivates me. Don't sweat the camera. It's enough to know that so many of you care about what I'm doing here. From the bottom of my atmospheric dump, I thank you all! This gift horse's teeth are all over the place, but he sometimes poops gold nuggets.
PS: Use ATF for your piston dish volume tests, not alcohol. Of course it's better just to use the spec sheet included with your pistons... but not everyone gets that luxury. Water is just fine for head combustion chamber tests. Dry and re-oil all parts that water touches.
Dynamic Compression Calculator: www.wallaceracing.com/dynamic-...

Пікірлер: 216

@TheCarPassionChannel 3 жыл бұрын

Thank you for this, I knew the math with the volumes but it really helps to see all the measuring techniques executed!

@DENicholsAutoBravado 9 жыл бұрын

When measuring your chamber size, accounting for the space below your valves, "...use gravity from whatever planet your from." Thanks for the humor! Even if humor was missing, I'd still watch, but these little goodies help.

@jasonedge2309 10 жыл бұрын

Caboose definitely deserves some wet food. Thanks for ur time and energy Jafro. Glad to see you're back at it. Best production automotive videos on KZfaq as far as I'm concerned.

@brianwilson2247 10 жыл бұрын

Fantastic work Jafro, I'm not an engine builder by any means but i did stay at a holiday inn express last night!

@marklowe7431 5 жыл бұрын

I have contacted youtube and demanded they allow multiple thumbs up just for your channel. I've learned a lot here. Very practical and detailed.

@pgrens 10 жыл бұрын

Glad to see you're back, Jafro! Also happy to hear that the repair came in under what you anticipated. Hoisting a cold one in your direction!

@poojadharankar5949 5 жыл бұрын

I haven't seen any perfect videos like this on KZfaq ..Thanks for your level of deep explanation..Thanks a lot..

@allryze4me 10 жыл бұрын

Wow man that was some impressive mind boggling information. I had to pause and rewind this video so many to actually concentrate and understand what was happening. Great job man... Keep it up.

@TGsrao1989 7 жыл бұрын

if it were possible to give more than one like for a video, this would be it! Extremely brilliant explanation! Textbook perfect!

@gergorian 10 жыл бұрын

YAY! So happy to see you back in action Jafro. Cant wait for the next video already.

@lpngcf266 7 жыл бұрын

Your work ethic is out of this world! Brilliant!!

@IanOberhotlzer 9 жыл бұрын

Thanks for being so informative, comprehensive and easy to follow. Very helpful! Thanks for passing it on!

@uprise51 10 жыл бұрын

Thank for all your hard work. Your videos have kept me thinking positive while being deployed and glad you can continue making videos

@Jafromobile 10 жыл бұрын

Thank you Jeffery! I know these videos mean a lot to many... and some of the very best messages I receive come from our men in uniform. The positive energy I receive is what keeps me going, too! Thank you for your service!

@HeimoVN 10 жыл бұрын

Glad to see you back in action jafro!

@timmcneil1536 10 жыл бұрын

Glad to see you back in action Jafro.

@kentashockney 10 жыл бұрын

Awsome videos! Very happy your back!

@Benjay1975 10 жыл бұрын

Jafro - great video, glad you got your camera back mate :)

@coc7711 5 жыл бұрын

im not a mechanic and i love this kind of KNOWLEDGE sharing videos like what he did. but i wanna know what is the reason why some DISLIKE this video?are there something wrong with the calculation?can someone please give me a reason.

@connorpalmer356 6 жыл бұрын

Very Very Very helpful! one of my favorites on youtube - keep up your amazing content

@izumimarcelo 10 жыл бұрын

I just wake up with my android KZfaq notification and was forced to watch this. Really good video. Nice math bro. Keep the good work.

@TheTremayne1 10 жыл бұрын

Hey Jafro, Im glad everything is ok now an you got your camera all fix. Love you videos as always. Keep it up.

@johnh1001 8 жыл бұрын

GOOD DAY ALL : I'm a technician in the aerospace industry from Toronto Ontario Canada , I've seen the video . If you'd also like to calculate you're compression pressure is goes like this . To-days atmospheric pressure (ie 14.6 psi times you're compression ratio ie 9.5 :1 = 138.7 psi . Each day there will be a slight difference in compression pressure . If you live at sea level you'l have the highest compression pressure , if you live in "Denver Colorado" you might want some nice 11.5 :1 pistons to off set the atmospheric problem . Bye Bye all and have a nice day ! ! !

@markphilpot4981 5 жыл бұрын

Say hello to the new math whiz! Enjoyed the video because I am a math major and I like these type things. Do I or will I remember it? No. That’s why you take notes. That way you have examples and even descriptions of things. Maybe your memory is infallible. Good for you! Mine isn’t so I take notes! You do what you have to to get where you want!👍🏻😊

@anthonywendt5834 3 жыл бұрын

I always revisit this video for reference. Thanks Jafro!

@BenGallou 3 жыл бұрын

Cristal clear. Wonderful video (as always)

@jimmyjet07 7 жыл бұрын

Thanks for demystifying this for me. Very helpful!

@mechguy83 10 жыл бұрын

Ahhh, a new Jafromobile Video my memorial weekend is now complete...

@gustserve323 7 жыл бұрын

Sir another great video! Thank you

@grngs1 6 жыл бұрын

VERY informative! You seem to know math very well, smart dude you are!! Thanks for the vid.

@madunwerkstatt3093 4 жыл бұрын

Just came across your video about calculating compression ratio. I usually did direct measurements to total cylinder volume plus sweep volume using burette filled with low viscosity oil such as ATF or 0w-20 oil. Oil poured through spark plug hole on both TDC and BDC. Yes it's messy, but more convenient (at least for me).

@phishitaac 10 жыл бұрын

thnx for all your hard work!!!

@TGsrao1989 7 жыл бұрын

if it were possible to give more than one like for a video, this would be it! Extremely brilliant explanation! Textbook perfect! pi*r*r*h!

@DJUniK 10 жыл бұрын

Glad to see you back with your amazing videos... Keep up the great work Jafro!!

@Ronke01 10 жыл бұрын

Here's a like for caboose man, glad you're back so quick!

@JAracer21 10 жыл бұрын

so glad ur back

@tiitsaul 10 жыл бұрын

You are the best Jafro!

@reynorizky627 8 жыл бұрын

Finally i understand how to calculate this thing. Because graham bell does not give you any picture why i should count this or that hehe. Thanks a lot man!

@hadriansmith6400 9 жыл бұрын

I got a Honda Super blackbird and all the things you have done I will try on the bike's engine. I spoke to an old man who used to tune exhausts for formula one cars in the old days. He said that they would make the headers out of copper pipe because it was easy to cut. Fit a long length to each cylinder. Start the engine and shine a strobe light down the pipe. Where the light shone on the pulse from the cylinder, they would know where to cut the pipe. They would measure the distance using a long piece of wire which they would slide inside the pipe to the pulse.

@Jafromobile 9 жыл бұрын

Hadrian Smith Wow, that is a really awesome trial-and-error shortcut that saves an awful lot of math. That old man was a wise old man with a timing light.

@thirtytwoslim 10 жыл бұрын

Jafro, great video very informative, I have been watching your videos for years and always enjoy them. I just completed my first year for my mechanical engineering degree and can appreciate all the work you put in blueprinting engines. I have seen this method done with the use of a thin bead of Vaseline cream around the circumference of the bore to seal the plexiglass to the cylinder head. Would that method have any benefit over this one or is it just unneeded? Im about to start doing something similar to my engine once I finish up with oil clearances

@Jafromobile 10 жыл бұрын

It's not just used as a means of sticking down the plexiglass. It fills the gap around the rings and prevents your test fluid from leaking down through the oil holes for the piston skirts that are behind the rings. kinduv like the stopper in a bathtub. If you use a viscous test fluid (unlike me and my lazy self), it won't drain fast enough to affect your measurements. A tenth of a CC in piston volume would barely dent the final compression numbers. I doubt I leaked that much alcohol, but I'm pretty sure that more than that evaporated. Alcohol is not what you want to use for this test, I was simply verifying an already-known number. Where the vaseline test comes in REAL handy is when you've made changes to the pistons yourself, like cutting new fly cuts, polishing, or ceramic coating. Those techniques aren't part of the original piston's spec sheet unless they were done by the manufacturer, and in cases where they're not, you would need the most accurate means of measuring it. You'd use Vaseline and a non-evaporating test medium.

@zx8401ztv 10 жыл бұрын

Great you have your beloved camera back :-)) All your calculations wizzed past my brain at lightspeed, although i could see where your were going with it. I did think you did the head volume oddly, a large hole in the plastic and syringe the measured fluid in untill no air is present, thats how ive allways understood it. Perhaps i was confused........ thats normal lol :-))

@billroddick6981 3 жыл бұрын

Nice video; thanks so much!

@phizzalo 10 жыл бұрын

Nice work in explaining compression Jafro :) My 64/63 build motor iam sure is high compression and only runs well on 93oct. I am still new at tunning but looking forward to see what it does at the track.

@tonkatoytruck 10 жыл бұрын

I really enjoy your videos. The wealth of knowledge is reason enough but the quality of the editing and narration is of equal depth. So, I have started to research some editing programs that do not cost to much but are feature packed. The few I have test drove do not have more than 2X FF and seemed to want to cut the resolution in half upon import. Any suggestions for a program that works on Win7?

@russell76531 10 жыл бұрын

awesome work happy to see u got your camera fixed :)

@killrroyale 10 жыл бұрын

ouch!!!!! my brain hurts... glad to see your up and running again.

@facundolopez7346 6 жыл бұрын

awesome stuff!!!! thanks for sharing!

@realityperformance5216 8 жыл бұрын

gidday Jafromobile How did I not find your channel sooner. cane with good timing though as I'm about to embark on the all mighty RB30/25Det-3.3lt Stroker. now to see how many of your bids I can watch before sleepy byes. Thanks Nate.

@Jafromobile 8 жыл бұрын

+Reality Performance You're still awake, aren't you?

@realityperformance5216 8 жыл бұрын

+Jafromobile yes yes I am. 99% of your vids are all over KZfaq that other youtubers have put up. BUT. There is not one single video that has ANYTHING close to your am out of detail. Your good mate. love the ya vids. now to delete all the other videos I have saved from other people and reload them with yours. keep up the good work.

@AllaBader01 10 жыл бұрын

thanks ,we'r waiting for next video .

@stupidsmartmonkey 10 жыл бұрын

Exceptional Vid!

@crtinkering7323 7 жыл бұрын

nice drawing at the end!

@jimjones9642 6 жыл бұрын

Now u need to show em how to get the corrected compression ratio.......... Awsome video fer sure

@Jafromobile 6 жыл бұрын

There's a link to a dynamic compression calculator in my description. Of course you need to know your valve timing events within a degree, but that's also why it's linked in my DOHC valve timing video. ;) That equation is far beyond the attention span of a KZfaq video. lol! The people who made it to the end of this one might appreciate it, though. :)

@WilbertRamos777 9 жыл бұрын

Awesome man i like ur vids u explain everything very good that's real cool

@DJDevon3 10 жыл бұрын

Welcome back. Glad you got your camera all fixed up. How's it working since the repair? If you're happy, we're happy. Glad to see you're back to normal. :)

@Jafromobile 10 жыл бұрын

It's working great! Some of the footage I shot shows the failure occurring and I'm sure it's evident in this video... but all the new footage is VERY clean. I like it! I'm hard at work on the next one.

@MaxWorldTech 10 жыл бұрын

More Caboose cameos! Great videos as always. One day I'll have my own garage and be able to do some engine building. But for now... I'll just be a broke college kid doing his work outside in a parking lot.

@Svarogperformance 8 жыл бұрын

awesome explanation thank you

@jackass123455 9 жыл бұрын

if you engine is already completly assembled is there a way to roughly calculate the cr. by say using a syringe to fill the combustion chamber with something like atf at TDC the amount of fluid entered would then be the total combustion chamber i know what my piston dish vloume is so i could subtrack that from the value i get to get the cylinder head volume. and then the swept volume being known would be able to give you the CR no? obviously not as accurate as a pre assembly check but doable right?

@Tims13ful 6 жыл бұрын

What about your dynamic compression ratio by adding inlet timing and boost pressure to the equation?

@DJDevon3 10 жыл бұрын

I thought you said cylinder bores are slightly tapered. Wouldn't that slightly affect the volume calculations you're doing or do your previous bore measurements already factor that in?

@Jafromobile 10 жыл бұрын

Yep. Slightly. Just like you said. We're talking slightly to the ten thousandth of an inch, so anything happening at the tenth position will remain completely un-affected. Egg and taper would play a negligible affect on static compression ratios if the engine is actually capable of running.

@oogie-boogie 8 жыл бұрын

soooo i have a question for ya,,i had a motor that had 300 psi on a compression test,,i know thats crazy comp,,but it ran looks a beast,,so what kinda deck hight and other stuff would u need for that?

@melchvanleeuwen2166 9 жыл бұрын

God damn you post some usefull stuff! Thanks for your video's

@markdailey864 8 жыл бұрын

great job breaking it down

@cj062989 10 жыл бұрын

Glad to see Jafromobile is in full force

@bluebulk 10 жыл бұрын

thank you. your awesome!

@Bunkers101 10 жыл бұрын

A lot of info in this vid, Thanks. =D

@angelcuriel4257 5 жыл бұрын

Super smart about engines

@scsmooth1 10 жыл бұрын

Welcome back Jafromobile.

@cheechooj 10 жыл бұрын

Nice volume tutorial, any chance you can teach me some differential equations?

@vjsingh592 4 жыл бұрын

Awesome.

@brianbvachek3219 2 жыл бұрын

Jafro, so many of us study your videos as if it were the ultimate religion. (-well, it basically is) hahaha Thank you for all the time and effort you put in to make these videos!! Hopefully we’ll see you at the next dsm shootout in ohio!! 🤘🏻

@tonkatoytruck 10 жыл бұрын

I was glad to see you got your camera back. Looks like you hardly missed a beat. Just wondering why you left the compression so high on a turbo motor?

@Jafromobile 10 жыл бұрын

I didn't leave it that way... I intentionally maintained a previous engine builder's selection in order to keep it this way. It was intentional. A high compression engine makes more torque, more power than a lower compression engine under the same circumstances. It comes at a cost of losing stability in your fuel source, so you've gotta be on your toes with your tune. Little problems there can lead to big failures, so I will be on my toes tuning-wise, with white knuckles, enjoying all the extra torque steer and tire smoke. ;)

@jamesbarratt593 5 жыл бұрын

I feel shattered now. Mind blown. Steam coming out of my ears. Only it all makes kinda sense. Mk2 jag next week is going to be even more fun.

@sjcwindsurf 4 жыл бұрын

Love the vids. you flashed a screenshot of a blueprinting spreadsheet...can you make that template available to us!?

@petrocksgarage 10 жыл бұрын

Where did you get the dial gauges & stands? I’m prepping to do a rear differential rebuild, and I can’t find good yet inexpensive dial gauges or stands to measure the back-lash. Thanks...

@thirtytwoslim 10 жыл бұрын

It's hard to find decent precision measuring equipment for a good price, you really do get what you pay for. Honestly you're best bet is to try and find a reputable seller on eBay and try and get some quality used precision equipment. Theres some really good deals on there, I bought a whole set of Starett micrometers and vernier callipers for really cheap on a bid. I had them checked at our shop and they were all smack on when referencing to gauge blocks. The stand you can go with pretty much anything as long as its magnetic and is sturdy, I think I paid 20 bucks at a local shop and its great. Im not jafro but thought I'd shed some light on some recent personal experience.

@Jafromobile 10 жыл бұрын

Like thirtytwoslim said, it is difficult to get them cheap. I also opted to buy some of my tools on ebay, and you really do have a chance of ending up with junk when you do that. My dial bore gauge isn't perfect, but I know why and I can work around it to keep everything accurate. Older stuff is better than the newer stuff. MSC tools is a great place to find what you're looking for. In addition, the stands... what I show here are 2 harbor freight magnetic bases combined into one magical tool. They have the vise-grip style clamping base with the gooseneck thing in that kit, and if you un-screw the stand, you can screw the gooseneck thing right into the base. I use it more than any of my other stands. The part with all the rods and clamps... is so cheap on that model that slightly over-torquing them strips out the fasteners. Again, reinforcing that the old stuff works better than the new stuff. I've been through several of those stands because of junk fasteners... but the gooseneck thing is awesome. It takes a fraction of the time and effort to set up. You just have to buy both kits to make it.

@gasparini76 3 жыл бұрын

What I don't get, is what are you going to do with the compression ratio later? Where the outcome is going to be used? Considering that I don't know how to tune an engine having EFI...

@jonathanbailey8376 8 жыл бұрын

great vids!!!!

@PHUSII 4 жыл бұрын

a lot of information here!

@SkylineDriver5 Жыл бұрын

Jaffro what is the best compression to run for a daily 600hp-ish evo IX on 91 octane?

@darkptnet 9 жыл бұрын

by the way, do you know eisntein?

@stoneyswolf 3 ай бұрын

Thank God for online compression calculator's.

@GordonWG1 9 жыл бұрын

I've made these comments on another similar video, but may be of help to some here. First, check out on-line chemist/laboratory suppliers for cheap burettes - makes it much easier for CCing. Use a long piece of plexi', or similar material, for the plate as you can do an entire head at the same time - don't forget to align the holes correctly. Some prefer to drill a couple of larger holes that match a couple of the bolt drillings, dropping a couple of the bolts into these will align the plate and prevent movement. Use a syringe with a small opening to run a small bead around the chamber/bore to seal it - I've seen some 'professionals' use thick smears that can make CC's difference as the plate is held off the sealing surface - you just need enough to seal. You will get a much more accurate figure for the piston's bowl or protrusion by using a DTI and lowering it in the bore a known amount and taking the relevalent swept volume from the total figure - especially useful if any part of the piston is above the deck at TDC. A little food colouring will make the fluid much easier to see - handy if the lighting or your eyesight isn't the best. Bore wear wil affect the actual swept volume - may be significant in some instances Can't recall the other point.

@Liamv4696 2 ай бұрын

Ever considered doing a dynamic compression ratio video?

@randyhigginbotham961 8 жыл бұрын

I've only subscribed to one other person on KZfaq. Nice job. I will search your videos but want to know how to pick performance parts to build a twincharged 4 cylinder engine.

@Jafromobile 8 жыл бұрын

+Randy Higginbotham No spoilers, but go look at the Eaton supercharger and plenum on a 3800 Pontiac/Buick. Great minds think alike.

@davidmccleary734 10 жыл бұрын

Nice video! DSM's are one of the few things that can make me do math these days :P So Im curious since your total combustion chamber volume is 565.2596 cc's if you multiply that by 4 that gives a total of 2261.0384. Does that mean you have a 2.2 liter engine? Or is displacement based solely on the measurement of V1?

@Jafromobile 10 жыл бұрын

Yes, the displacement is based solely on V1. You got it!

@josiah7068 10 жыл бұрын

Ok thanks for the headache and nose bleed to much thinking for me I hate thinking but great vid

@kylemilford5968 9 жыл бұрын

I will admit, I did not finish the calculations for each cylinder, However given the cylinder specs you provided, Would that mean your total CC would be in the ballpart of 2261cc rather then the 1997cc factory claims? Or would the 1997 be the CC of the block itself, Not including the 47cc claimed head combustion area?

@Jafromobile 9 жыл бұрын

Kyle Milford The advertised displacement is the swept volume. :)

@Foxstang4life 9 жыл бұрын

Holy shite there's a cat in the door !! Very impressed and im guessing he likes fancy feast salmon or ocean whitefish?

@exe16 10 жыл бұрын

Jafro, I heard that some cranks are offset from the cylinder bores a few milimeters to improve the leverage of the force applied by the combustion, just like piston pins. When that happens, the crank's stroke is not necessarily the same that is swept. Do you know if there's any offset at all at the crank of 4G63's?

@Jafromobile 10 жыл бұрын

Interesting. I don't know if they do? I've never heard anything about that before applying to a 4g63 so I'm inclined to say they don't... but I really don't know for sure? I don't think I even have the equipment necessary to measure that?

@carlosschechter3310 10 жыл бұрын

Bruno, foque em se formar....

@xpoohx105 9 жыл бұрын

Hopefully I watched the video right. Would there be any merits in terms of chasing the last few horsepower from a relatively small displacement engine in doing a second round of machine work trying to chase down near perfect values? As I understand it one of the major goals of a blueprinted race engine is achieving consistent values on each cylinder.

@Jafromobile 9 жыл бұрын

xpoohx105 That is indeed one of the goals of blueprinting. What you can't perfect, you can often tune around. You need to know where the differences are in order to do that. So if there are any variations, there are multiple approaches to dealing with them, and machining is only one of them. If given the opportunity to perfect each value and match all cylinders equally, all it does is simplify the tune. I think my Hyundai will be a prime example of this, because of the age, wear, and condition of its worn-out re-used parts, there's only so much I'm willing to machine. It would better me to start over. But the work I did dialed it in a hell of a lot closer than where it was. I'm continuing to use the un-even, worn out rings and bores to my advantage. It's how I've managed to run 22 PSI through this thing at 10:1 compression without blowing it apart. It's set up intentionally loose, and in a well-overbored out-of-spec block for a simple reason. Because it works. Sometimes a blueprint just shows you what you need to fix. Sometimes the blueprint simply demonstrates why certain things work when they shouldn't, or when everyone else says they shouldn't. Is there merit in making every value match across all cylinders? Yes. Absolutely. Especially when your time and money resources are endless. But match spec? Nah. Not so much. Sometimes you should even avoid it. Either way, you can tune around it, matching everything just makes it that much easier to tune.

@TurboMitsubishi 10 жыл бұрын

That's pretty close to 10:1, what turbo and fuel are you going with on this build Jefro?

@konkoookon 10 жыл бұрын

thank you.

@joelkarch3538 2 жыл бұрын

wow its like watchin bill ni the sicence guy on engine degreaser!! im not that smart butt i would like to learn.nice job to all involved!!!

@Liamv4696 10 жыл бұрын

Hey Jafro, my 4G93T engine came stock as an 1,834cc engine with 9.5:1 comp ratio pistons, the engine was rebuilt with 8:1 comp ratio pistons, theoretically this increases the displacement, but is it by a measurable amount? or is it only a tiny amount. not expecting you to do any math, just your opinion :)

@Jafromobile 10 жыл бұрын

Swept volume is all that's used to calculate displacement. Even when the dish of the piston changes, the bore and stroke are all that's used to calculate swept volume. Imagine that the top and bottom of the swept cylinder are in the shape of the top of the piston. The cylinder in-between stays the same volume because the bottom and top of the cylinder are the same.

@LOWPR0FiL3 4 жыл бұрын

bloodly hell. if my camera came in a box and wrap up like that i would take it back.

@RICKAFIX 10 жыл бұрын

welcome back Jafro...where the amazing tunes? thanks.. that was great

@Jafromobile 10 жыл бұрын

My math teacher didn't come with a porn soundtrack, but he was young and pretty popular. 'pretty sure some of the ladies in class wish he did... but I find it a bit distracting when I'm doing math. ;) Thanks for staying tuned in over the years!

@criticalmass181 9 жыл бұрын

Awesome stuff. I was wondering, though????? Do you have an explanatory video on tuned exhausts? I have a V4 engine, and the exhaust plumbing (4 into 1) is insane, in the name of neatness. I was going to fill the whole lot with water, then divide it by 4, to get a singular volume. Do you have anything on here to shed some light? Great work...

@Jafromobile 9 жыл бұрын

That's exactly how you'd want to do it. Tuned exhausts would normally go through the liquid displacement test runner-by-runner during assembly, and a tuned exhaust would be sized according to displacement and intake port volumes if you're trying to maximize the flow per-runner, but the liquid displacement test and a notepad is the best way to do it short of flowbench time spent matching the flow rates to the rest of the head ports. Us turbo guys have it easy, we do it based off of manifold pressure and turbo exhaust housing sizing. NA setups benefit more from tuned exhaust runners than the boosted crowd. I should have done a liquid displacement test on the head I ported, but it's going back in the car in about 10 minutes. :\

@criticalmass181 9 жыл бұрын

Just to clarify something, ...no...the Ducati, on my profile is, as obvious, a V twin. This is for my V4 Honda. It's great to get some affirmation from you. You're on the ball, to say the least, and I value your opinion. As i'm sure you're aware, it can be hard to find someone to 'bounce off', when you're trying to figure something out. And, hey....if you smear your finger over a bar of soap, and touch the water, when doing your head displacement, it'll break the surface tension of the water. May help...... Thanks again.

@Zakowski1983 9 жыл бұрын

Excellent video , have you ever done NA setups ? using the 4G63 engine

@Jafromobile 9 жыл бұрын

Nope. Started with a 420A, then a D15B7, then turbo 4g63 and never looked back. No offense to the NA cars, I just couldn't do another NA motor after I experienced boost.

@Zakowski1983 9 жыл бұрын

***** do you have an email address i can send you some information on i am doing a build for a ford pinto engine and it would be great for information sharing :)

@breadbaconcheese 10 жыл бұрын

cant wait for next viiiiiiiiiiiidddd :D hahahahah

@gurkanakburu5353 7 жыл бұрын

Sorry I can not figure out what you did in V3 would you help me? My piston diameter 83 mm piston height 0.1 mm how can I do ?

@Jafromobile 7 жыл бұрын

83mm x 83mm x .1mm x .7854 = 541 cubic millimeters. A cubic centimeter is 10x10x10mm or 1,000 mm. So your V3 layer is .54106206 cc's. ;)

@GereDJ2 7 жыл бұрын

Q: Would/could variations in piston height to deck affect a smooth idle even though only a tiny difference in compression? Also, I be willing to bet 80% of supposedly trained and experienced auto mechanics don't have the first clue about this process.

@Jafromobile 7 жыл бұрын

You might be right about that. Yes, it could very slightly affect compression ratios, but not enough to feel any difference over the other harmonics generated by the firing order. Without 4 wideband o2 sensors and per-injector tuning, you'd be splitting hairs chasing after it. There should be less than a few thousandths of an inch of variance in the piston height which would barely affect the numbers in comparison to things like the crushed head gasket which is around .030" on average. The hole in the gasket is bigger than the bore, too.

@chrissraceporting7055 6 жыл бұрын

How have you gone with the felpro head gaskets

@Jafromobile 6 жыл бұрын

It's what's currently on my Hyundai. That car is 9.875:1 compression and it's logged two 31 PSI 3rd gear pulls with no issues. I'm running the crap out of it and it's taking all I can throw at it so far... this many years later.