short runner VS> long runners(Who's right
 

After reading the article in Family & performance boating,I was all set to try the kit from Boost Power that is supposed to give a 65hp. increase, on HP500EFI engines.One part of this upgrade are spacers that the article says lengthens the intake runners,which is supposed to help boost hp.(as well as cool intake).
But on the Arizona Speed & Marine website they have a intake manifold WITH shortened runners that they claim helps to boost hp.
So who in the hell is correct here???????Any Ideas?
Thanks
Steve

yes...keep in mind that the runners are doing totally different tasks here...efi engines only use them for air. NOT to atomize fuel. they work for the most part just the opposite of each other...most of the prodution efi runners are too long....made for more torque and mid range....cam selection and reversion have a VERY large effect here....i did some runner work and testing for the old 502 MPI mag engines....O what fun!...pain in my ass really! but, paid off in the end....AZ has it go'n on for the most part....did this help???

Longer runners will boost HP in a drag racing application, shorter runners boost TQ. I know this holds true for carb applications, not sure with EFI set-ups. However, in most instances you need to be turning the motor very hard to notice the difference ~~at least 6,000 rpm.....I'm guessing here with the EFI set-up......but I don't think @5200 rpm you'll notice much of a differece;)

the testing we did showed 25 hp by playing with runner length...

r u saying all drag racing applications???

ps...please don't listen to the cars guys....

Joe;
thanks for the reply,but damn I guess i'm awfully dense here.
If you have the same 500 efi engine and one company says that by shortening the intake runners you gain hp. and the other claims by lengthening the intake runners you increase hp. who's right????
Steve

easy!!BOTH....at what rpm or hp average over a rpm range...just to say"increase hp!" is so very lame! trust me even WE (ford) play games with this....O-yeah,,,we play with runners and plentums too!!! you can always call me if ya want help.

Audacity;

I'm saying, I agree that changing runner length will have an impact on power, where its made, etc, but typically the effects on HP won't be noticed until the motor is turning hard. However, I do not know much about EFI...my only real experience has been with carb applications.

I'm curious as to where the extra power was found when the runner length was played with to find the extra power....leaving everything else alone. Was it in the mid range or top end with a longer runner?

ps.. I like your BOTH response because it is so true with all the variables introduced.
:)

I have to laugh almost everytime a new EFI trinket comes on the market for a boat. I have yet to see the new Boostpower 65HP Wonder [just add this to the 25hp airfilter, the 30hp throttle body, the 25hp ECM re-map.....WOW!! 145hp!!!] Lengthening the runners on a dry flow/wet flow manifolds shifts peak power levels down the RPM scale,generating more torque at a given, but lower RPM level. Carb/tunnel ram set-ups are designed to suspened large quanities of fuel, if you feel this is an exception. Isolating the plenum from engine heat would probably this trinkets' best attribute [a big disadvantage of a dry flow manifold], but I doubt it would make much diffrence because of the already existing high ambient heat present in most boat engine compartments. Save your money, or get creative with increased air circulation under the hatch as EFI motors are even more affected by heat than carbs. Take Care

Well said liquid;

Yes I was referring to a Tunnel ram set-up.

While EFI is pretty sweet, I have yet to see a system that can make more power than a well tuned carb.:rolleyes: :cool:

Now, I forget if ASM were the original designers of that intake or if it was Lingenfelter. My guess would be that either one of those would be able to help.

"trust me even WE (ford) play games with this....":D
easy Joe:D :D
going to nooner?

Intake length longer = lower rpm torque peak.
Intake length shorter = higher rpm torque peak.

We used to run a Hilborn style injector on an alky motor V8 dirt sprint. We would use the injector horn length(s) to tune for a particular track. This follows thru to 2 strokes, dirtbikes, drag motors, or anything else you want to mention.

Like was mentioned earlier, tunnel rams are for high rpm and are long runners. The runner length is not optimal, but is such so that they are STRAIGHTER, and do not induce the suspended atomized fuel to slam out of the airflow as it makes a "turn" in a conventional intake. Straight keeps the fuel in the airflow. Long just happens to be the only way to keep them straight.

hey guys

Im running a Holley tunnel ram with fuel injection and it mid ranges as good as my blower did. The misunderstanding with tunnel rams is that drag racers use them with extremely wild cams that make power at unrealistic rpm for boats. The tunnel ram has long equal lenth runners, perfect for making torque.

Here is a picture

You know, there's another board member that's running a fuel injected tunnel ram on a Fountain too! Man, what a small world! :D

Good point JSV;

I'm running a Dart tunnel ram on a 632" Merlin, 2X775 Race Demons, motor makes big torque in the mid range and idles at 650rpm in gear. Cam is solid roller 280/288 @.050 115 centerline.

How do you like your holley injection...I almost went that route, but holley was not comfortable with it in my app 2 yrs ago and is was expensive.


:eek:

the theory behind a long runner or tunnel ram is: as a very high velocity is achieved (somewhere close to the SOS) the mass will gain a greater momentum and with PROPER cam timing, you can actually build a small amount of pressure prior to the valve. obviously reversion (cam timing plays apart also) is tuned with runner length as well. someone talked of suspending more AF??...a better example of that would be a carb spacer, which would increase plenum volume and supply a different pulse wave.

jdnca 1


I am using a Haltech system. It works great and laptop programable.



Cord,


JSV is my home computer. I should have said something

Is it worth shortening the runners on a 502mag MPI without having the runners extrude honed as ASM does. I fiqure about 3/4" but need to do more checking and measuring. I have access to machine shop to shorten runners easily and the cost is right! ASM wants to much $ but if I can do the shortening myself and it would help well why not? We are just cleaning up a 502 and while it is apart now would be the time. We were not planning on changing the cam at this time. Has stock Hyd roller cam.

Thanks

Drew,

You might look up the tec article Hot Boat Mag did on the 502 a while back.

Thanks Turbo that is exactly what I plan to do but just wondered if anyone had tried some of these at home and if so were there any gains. Motor already has good exhaust system and air cleaner with adjustable fuel regulator. ASM reprogramed ECU when exhaust was added. Had roller rockers installed a while back as the stock pivot ball rockers were showing signs of HIGH temperatures. Mainly just freshening up the heads as it pulled an intake manifold gasket in and started using oil big time. Also had some valve sealing issues so we pulled the heads. Glad we did the head gaskets were going to go next.

I have some plans but they are on the back burner untill I can afford a fully programable system.

I built one of these engines w/ 625+ tq and 530+hp and it's still in service w/over 400 hours of hard runn'n!...and he didn't even follow my instructions on service and runn'n the damn thing!

Some interesting information here. What's actually going on in the runners that makes length important anyway?

I remember from many different sources that long runners are for boosting torque at low RPM, but I dimly recall a few other things:

- plenum volume also involved, there's a plenum "boost" too

- a long column of air is harder to start moving, so no good at high RPM when you have little time

- acoustics has something to do with it

When the valve slams shut a pressure wave travels back up the runner to the plenum or atmosphere, and part of this pressure reflects back down the runner. At a given RPM, the runner length will be such that the reflected wave arrives at the valve just as it is opening for the next intake event. This is how headers work too? Resonance is what some people call it; same thing that makes a pipe organ work.

Lingenfelter did the development work for Mercury. At the same time he developed his own "stealth" manifold. Think of the Mercury manifold but increase the volume of the plenum and extend the runners inside the plenum with extra tubing and a bellmouth inlet for each runner. This manifold made 600 ftlbs of torque with peanut port heads at a ridiculously low RPM. High RPM HP was limited. I think you can still buy it from Accel.

Turbo I hear you man. Programmable is why I am hesitant to make to much change.

Audacity any particulars on the motor would be appriciated. Was this a full mod as for upgrade to 2.25" intakes, cam change ect.

Tomcat I wish I had a dyno in my garage to play with! A lot of variables come in to play and I think the 502 is a pretty good package but we always want more.

basically...very loose with that word!!LOL...runner length should be based on the speed of sound and as you all know that air will move from the hi pressure zone to the low...the more inertia it has (air is compressible) the more you cram/ram into the cylinder, hence the tunnel ram. so yes tomcat, you are on the right track for a carb engine...some of the rules change for EFI's only because there are different variables now...

i'm not really to sure about how i feel about telling people "how to" build up that engine...i designed and built a throttle body...i'll thell ya there is nothing in that unless you relly get out of hand and make 600+hp and hi rpms...i like to clip mine @5500..i'll tell you cam timing is VERY important to this engine (as with all) as will as the idle seq....i wanted a big cam hi hp engine to idle at 710-730 exactly ALL the time...it took a TON of dial in work, but it can be done. i'll tell ya if you think you will see something with a upgrade in flame arestor,,,just take yours off and look for a change...i've yet to see a EFI backfire a flame out the TB. personally there is more to gain (hp speaking) by taking off the EFI....have fun!

Thanks Audacity and I hear you load and clear but had to ask. You pretty much answered my question as to what it would take $ wise and time. Not looking to build that kind of HP just looking for some gains and keep the EFI while it is apart. If I want to go BIG HP I will go carb as I can tune those myself and cam selection to get it to idle is not as touchy as with EFI. I can probably get what information I need from printed articles. Thanks again.

drew,,,call my home later tonight...your engine is apart u say???
my # 517 540 1278
i'll give ya some tips!...no ecm changes either!

Thanks Audacity you are on. Motor is apart and I will call.

Andy

call my cell after 9 at 734 635 1697...sorry i fell asleep yesterday!

Joe,and everyone else,thanks for all the info.Made for some VERY interesting reading.And just what kinda tips ya got there Joe????Might need them in the future.
Steve

none that are free!!LOL

i don't even have time for my pleasue boat!
:rolleyes:

raceboats are fun but stressful at the same time!

Audacity what time zone you in. I am on the west coast if you didn't notice. Hate to call you at 9 only now it's midnight! I can imagine what kind of tips I would get then much less the cost. :D

Andy

Joe
I hear what you're saying on time,here it is the 3rd week of June and I've only been out twice.....
Steve

don't get me wrong...i on a boat EVERY weekend....spen 3 weeks in key west til the 7th of jan every year!....then rac'n takes over. this year is BLOWING by!