Steve A.K.A RAMPAGE

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

audacity

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???

jdnca1

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

audacity

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....

Steve A.K.A RAMPAGE

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

audacity

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.

jdnca1

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.

liquid lounge

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

jdnca1

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.

Cord

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.