Experts: Runner length and volume?
 

I was reading some comments about using the 500EFI intake on larger displacement engines. Guys found the power to fall off after 5000 RPM on a 540. Is this because the runner is too long or too small? I also see that sheet metal tunnel ram intakes can now be ordered with "long" runners.

The small and dangerous amount of information that I have says runner volume has to go up with cylinder displacement. The runners in the 500EFI intake appear to narrow quite a bit where the crossed runners touch.

I have also read that runner length determines the time it takes for the pulse from the closed intake valve to travel to the plenum and back to the valve again, where that pressure pulse can help fill the cylinder when the valve opens again, a kind of acoustic supercharging. Therefore runner length has to be coordinated with cam timing and engine RPM range.

Any rules of thumb for runner length vs RPM range? For example sheet metal tunnel rams for drag racing often have runners about 6" long and are being used on engines that reach 8000 RPM. What should runner length be if maximum RPM is 6000 RPM? If I say that the port in the head is 4" would this get you close?

8000/6000 X 10" = 13.3

13.3 - 4 = 9.3"

Re: Experts: Runner length and volume?
 

Tom: Not sure how expert I am having designed a couple of intake manifolds but I can give you the formula for calculating optimum runner length.

L= ^ ((ECD x .25 x V x 2) divided by (RPM x RV)) - 1/2D

Where:
L = runner length
V= velocity of air ( use 1250ft./sec)
RV= reflective value ( pulse number -use 4th wave= RV=4)
D= intake runner diameter
ECD= effective cam duration= 720-(adv.intk. duration - 25)

This should give you a length in inches which includes valve to plenum.
Hope this helps
Ray @ Raylar

Re: Experts: Runner length and volume?
 

F1 engines rev to over 18000, and have short intake runners. The runner length is variable, but is generally short. These engines don't make any power at lower rpms, and have relatively narrow power bands.

Re: Experts: Runner length and volume?
 

Drag racing engines such as pro-stock (not nitro) have relativley narrow powerbands complemented with a 5 speed gearbox. F1 cars have a 6 or 7 speed gearbox. Runner length has to be optimized with rpm range and thus is a compromise. Ford and others have designed variable length intake runners to increase the powerband range.

Re: Experts: Runner length and volume?
 

GPM,looks like you used this post to show off those BIG HP NUMBERS!!(I'd do the same thing :D :D ). Now that you teased us with that wild dyno sheet,you might as well hijack this thread and give us details,Smitty

Re: Experts: Runner length and volume?
 

I'm not trying to show off, I know there are other people out there doing a lot better,
I run a tunnel ram.

Re: Experts: Runner length and volume?
 

Gpm,I wasn't trying to slam you or anything,your dyno numbers were outright AWESOME and i'm sure ALOT of us,including tomcat who started this thread,are eager to hear your combo!!!PLEASE re- post them and tell us about your combo,even if you start your own thread,We all (including myself) have turned tomcats threads into 4 pages before :D ,i'm pretty sure he likes to get as much publicity on his supercooler as possible :D , We want details,specs,etc,Smitty

Re: Experts: Runner length and volume?
 

Ray,
Do you factor the back of the valve to the flange?
Bob

Re: Experts: Runner length and volume?
 

dayummmm!!! :eek: :D :D

Re: Experts: Runner length and volume?
 

GPM,what kind of fuel injection are you running,what are you controlling it with,who programmed it?What are you running for a innercooler and what kind of plumbing are you using to get air into intake,can you post a pic? I am upgrading my heads this winter and am looking for induction ideas to replace my 502 mag intake and fuel injection. I am running m-3sc on 540 blowing thru stock 502 mpi intake. What size injectors are you running and what kind of fuel pumps? What kind of hull are you running this in and what kind of drives? How good does it idle,are you running dry exhaust? Thanks,Smitty

Re: Experts: Runner length and volume?
 

Home made system, Fast computer, tune it myself with laptop, I run the M5 system,160lb injectors,weldon 2345 pump, 26 cat, I get 6 to 8 hours out of an XR, working on a different drive, idels between 900 and 1000 in neutral 650 -700 in gear, where ever I set the iac. Wet exhaust. Holley sells a single four marine efi intake I think it goes for around 450, Holley, Force fuel inj, Kinsler, just to name a few, sell 2000 cfm throttle bodies. I would check the manifold for flow before bolting it on. I would want the manifold to outflow the head, no matter what the application. There's a picture of the motor on Procharger.com marine modified.

Re: Experts: Runner length and volume?
 

Thanks Ray, that helps get in the range. What prompted the question was also using tunnel rams on boats. Most of the cast or sheet metal tunnel rams are for high RPM. I'm looking at the edelbrock catalog and the Victor Ram 2-R is rated for 4500-8500 RPM!! The runners look about 6". Sheet metal intakes for drag racing the runners are 4-5". It looks to me llike a runner in the 8-9" range would be better for say 6000 RPM max. Makes for a high intake unless you can cross the runners somehow. This is easier to do on symmetrical port heads like the 496. What runner length did you end up with and what Max RPM were you aiming for?

GPM: Very impressive numbers; what octane do you run? Others with EFI and the datalogging ability have noticed the intake temps. If I remember right Turbojack sees 150F after a short run using a 504 intercooler. When he converts to the Rtech supercooler we will have a back to back comparison.

Re: Experts: Runner length and volume?
 

Kennywould, asked me to post this, he runs it on a 564 n/a motor very successful.

Re: Experts: Runner length and volume?
 

TC, I'm running the 648 cooler, according to data logger I'm seeing 125 to 127 air temp at the engine, both on the dyno and after a mile and a half race. I run 94 octane pump gas with nos booster when I'm going to 15 lbs of boost. If you are going to run the 504 you have to modify the inlet and outlet water for more flow, it still dosen't work as well as the 648.

Re: Experts: Runner length and volume?
 

-GPM
Thanks for putting up the pics, stock merc manifold off of 502, which I was told by some motor guru at a boat show , don't even scratch that manifold! Well I guess I did a little more than scratch this one! It's been ported, divders were cut down so the runners are 7", fuel rail & manifold modified to accept larger injectors, the plenum is completely handmade, 105mm throttle bodies. Thanks to the help of some backyard gearheads, works pretty nice. :D :D

Re: Experts: Runner length and volume?
 

Pretty impresive handy work on that intake!!

Re: Experts: Runner length and volume?
 

Kenney: Nice job of opening up and reworking a 502MPI intake for big flow! I like to see that kind of creativity! and ingennuity! Tom, our BigPower 496 manifold has big 13" runners and a big plenum, it flows 98% of headflow and our head flows 360cfm @.600 lift, so we were pretty happy with the results. The best part of the results were that the stock 496 Ho with our cam heads and manifold is making 546ft/lbs of torque at 2500rpms, 610 ft/lbs at 4100 rpms and still making 541 ft/lbs at 5200 rpms. Nothing like big long runners and high velocity intake port s to make torque like a diesel!
Bob; to answer your question, no We just used the valve seat as our measuring point.
Great Post Tom, lots of info flowing here!
Ray @ Raylar

Re: Experts: Runner length and volume?
 

Thanks Artic, Raylar I appreciate that. We thought that the design of the stock plenum and the height of the intake into the plenum wasn't very impressive! There was plenty of talk in one of the boat mags about cutting the tops off the intake 1/2" to set them level in the plenum, but it seemed that the problem with that, the flat tops on the runners and the size of the stock throttle bodies weren't cutting it! It's not easy to see on that pic but I cut down the dividers just past the intake bolts, about 5" and opened up the tops which I guess you still have 12" runners in the manifold alone but the top 5" is siamesed and I think they really help feed each other. I removed as much of the metal I could inside the bottom 7" of the runners, opened those up nicely. I never flowed the intake but I can tell you it made a heck of a difference! The plenum was a design as you go, I took some criticism from some about it but there again it seems to work well! I don't know for sure but I think there is a dyno sheet laying around here somewhere, see if I can dig up some numbers.

Re: Experts: Runner length and volume?
 

Is there any opinion on tapered runners? Some tunnel rams have them and it seems to make sense to have more plenum volume available with the taper allowing the velocities to be higher just before the charge enters the head. On my NA 598" solid roller motor I have been contemplating going to a tunnel ram and have heard some nice gains may be there if the manifold is fit properly to the motor's RPM's. Does Hogan or any of the other custom manifold manufacturers do this with the shape of the runners?

Craig

Re: Experts: Runner length and volume?
 

Tomcat,
Runner lengths can be tunned for either HP or torque. Once the engine size, rpm, and camshaft have been decided, the the tuning lengths can be computed. It is common for me to supply header sizes to my drag customers and header and intake sizes to my circle track customers. This type of tunning will optimize the entire air and fuel path both in and out of the engine. Moderate gain's can be had by doing this.

Undersizing plenum area and runner size is just as bad as oversizing. Properly matching volume to CID needs at specific rpm ranges will increase the RAM effect on an NA engine and greatly increase the effiecentcy.

Tapered runners are the way to go. The key is what is the correct transistion.

Chris

Re: Experts: Runner length and volume?
 

Tomcat,
This may help also....some of us hang out on this site www.speedtalk.com There is always good hard core facts on this site from some of the best in the industry. Don Terrell is an ex-cup guy and knows alot of people.

Chris

Re: Experts: Runner length and volume?
 

Chris,
Do you guys make custom intake manifolds? If so I would be interested in hearing your opinion about what gains could be expected on my motor with a custom designed manifold. I know it won't be cheap, but what is with this sport?

Craig

Re: Experts: Runner length and volume?
 

Craig,
No we take care of the bottom end. I would go with CFE or Wilson. Both know there stuff. If you go with CFE, I know Scott, tell him Chris from Stef's called and he will take care of you.

Chris

Re: Experts: Runner length and volume?
 

Thanks Chris!

Re: Experts: Runner length and volume?
 

Found this laying around, don't know if you will be able to read it.

Re: Experts: Runner length and volume?
 

Thats why I keep you around, information, just a closet full! :D

Re: Experts: Runner length and volume?
 

GPM,
What are the particulars on that motor? I am assuming that is the motor with the modified intake manifold. Is he running a stock oil pump? We run a stock low volume oil pump on our 468" in our 66 Vette and that is about where the oil pressure is with 10W30 Mobil 1. :drink:

Craig

Re: Experts: Runner length and volume?
 

Better ask Kennywould,it was a while ago, I just dialed in the EFI.

Re: Experts: Runner length and volume?
 

Kennywould,you also made impressive dyno numbers(really close to what my 540 made on dyno with m-3 procharger at 6 psi boost). Fill us in on your combo(.050 duration,cam specs,compression,injector size,exhaust etc). Are you using mefi3 controller,who did your program for you. Did you use progressive linkage on your throttle bodies or do they open at same time. Are you using a stock tps on just one of them to tell computer info? Are you using merc iac motor and map sensor mounted to your custom top half?How much fuel presure/injector size?I am learning a little more every time someonetells about these fuel injected combos!
GPM,does the fast controller come with a base program that you tweak with laptop on the dyno at different settings and pulls or do you have to start at square one and create a program and make 100's of trial and error pulls on the dyno? Are you running somekind of exhaust sensor that modifys fuel curve (o2 wide band or something). I'm gunshy of getting a different fuel injection and trying to get program right while test driving boat under boost on water(one lean run and its all over!). Obviously you must have to start out fat and sloowly lean it down until its still making safe power,ive kind of done this already with factory fuel injection on my boat with blown 540 by slowly stepping up base timing and adjusting boost referenced fuel presure.Do you run a flat given fuel presure and make adjustments to your pulse width with your set-up or are you raising fuel presure with boost? I hate the boost refernced set-up on my boat,it's too rich at part throttle boost and i'm definately going to run bigger injectors in whatever fuel injection i run next year and use the two bar map sensor to tell computer to adjust fuel curve,i'm currently doing both and its NOT precise. Thanks for any info,I haven't been able to get any exact answers from the "fuel injection experts" other than multiple reprograms of my controller,Smitty

Re: Experts: Runner length and volume?
 

-Craig
Motor 564 cu, hand ported bb2 xtra heads, 300/308solid roller, 9:1, stroker crank, home grown intake & plenum. I think after several pulls with no oil cooler, the oil pressure is going to drop, usually running straight 40w :cool:

Re: Experts: Runner length and volume?
 

I figured you would have questions :D , at .050 272/280, 748 lift, only one throttle body has the TPS, its progressive, 55lb injectors, if I remember correctly somehwere around 42/44 on fuel psi, jeeez have to keep some secrets, your the first to see that intake :eek: , I ran down a new 275 Baja with a blower on it and passed him with my 272, he wasn't real happy agout it! Gpm does my tuning :rolleyes:

Re: Experts: Runner length and volume?
 

Smitty, that's a lot of questions, the Fast system has a base program, but you would have to set it up for your combo. Put in your cid,4,6, or 8 cylinder, 1,2 or 3 bar map, injector size, timing 50 degrees for bbc. You have a wide band o2 option, helps a lot, it can add or subtract fuel. You have to set up A/F ratios, timing map, accelleration maps, most of it can be done with power on,motor off.I always run a boost referenced regulater, 43 lbs at idle, most injectors are rated there. Once you get a program together, fire it up, let the fun begin. Start with the idle work your way through the maps, starting with fuel,sometimes it's a pain in the ass, as you get the maps closer you start making data logs and fine tune. It takes a while and I don't type fast enough to explain it all, I've been at it for almost 15 years now, I like EFI because I can run big cams, big heads, make decent power, and still idle around 1000 rpms or less. My wife unloads ands loads the boat, I can tow skiers,and go out and run over 140, all in the same day. TC. didn't mean to hog the thread, I think I'm doing good with the tunnel rams and EFI, but really don't have anything to compare to.

Re: Experts: Runner length and volume?
 

Is intake runner length more critical on a carb motor than an injected motor? It seems it would be more critical on a motor with a wet manifold to promote optimum fuel atomization where with an injected motor that is done with higher fuel pressure and the injector. Is anyone familiar with the old school trumpet type of Kinsler or Hilborne systems? Most of these were mechanical fuel injection, but they can now be used for EFI. I know they sold different length trumpets for tuning purposes. I love the look of those systems!!

Craig

Re: Experts: Runner length and volume?
 

Don't know much about the systems, seems it would be hard to keep consistant, Chief Engines had one for sale, and I've seen them on Racingjunk.com.

Re: Experts: Runner length and volume?
 

Craig,
Kinsler is developing a 3 piece EFI stack injection system that was scheduled to be introduced the first of this year. It features short and long runner configurations with 2.5/2.9/3.0 throttle diameters, depending on the application. If you need more info let me know.
Bob

Re: Experts: Runner length and volume?
 

Bob,
That system would be awesome, not only in performance but in esthetics!! I'll bet Kinsler will want upwards of $12,000 for that package! I wonder if it will be coast guard approved for use in a closed engine compartment? :p If my memory serves me correctly I believe Merc used a system similar to this on the class 1 race motor. It was a solid roller 499" 12.8:1 compression big chief head motor. Made around 900 HP at 6800 RPM!!

Re: Experts: Runner length and volume?
 

I see you mentioned you have a 272,i would asume thats a baja? Now youv'e really got my attention because thats what i have too and ive been trying to find someone who has dyno numbers on their motor compared to their top speed. When i built my 540 to replace my 502 i was expecting to see 750-800hp,my 540 made 630hp at 5200 and 697ft lbs torque peak. My boat went 2 mph SLOWER than it did with the 502(76vs 78). Since then i added timing and boost and boat runs 83.5-84mph with normal load(4 people/3/4 tk gas)and best of 85.1 (all gps speeds). What kind of speed on gps are you getting out of your boat with your 770 hp and at what rpm,if its not too much to ask :D ,i should be able to compare my speed at 630hp to your speed at 770hp and factor exactly how much hp i'm currently making to achieve my current speeds,thanks,Smitty
PS KENNYWOULD,did John Force notice his spare cam missing out of his parts trailer :eek: ,THAT IS HUMUNGOUS!!!!!
Tomcat,sorry we aren't really talking about runner length but some good stuffs coming out!!

Re: Experts: Runner length and volume?
 

Good thread!

Re: Experts: Runner length and volume?
 

On the question about taper in the runners. Runners should taper approximatly 2% per inch of runner length from the opening towards the valve on a constant smooth basis if possible. This will increase velocity and the ram effect. As for which benefits more, runner redirection is more critical in a wet( carburated) manifold, because when wet air changes direction(curves) it will let more fuel drop out of suspension. Remember fuel (heavier) and air don't weigh the same and hence change directions at different speeds. The runner length determines where the rpm power band of a manifold will be and the taper helps develop the speed of the charge.
Ray @ Raylar

Re: Experts: Runner length and volume?
 

Raylar,
Have you sent that block yet!!!!!

Chris