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Quote:

Originally Posted by abones (Post 4089744)

Refering to the above few posts only, I don't want to derail this thread, but on a N/A motor you can exceed 100% cyl filling/ volume qiuckest by choosing the right valve event timing matched with a free flowing exhaust header to scavange the the spent fumes and at higher RPMs get better volumetric effecincy. (this is taking for granted the intake side is up to snuff). No need to hold the exhaust valve open so long in a boosted motor as the boost pressure will assist in exhausting the cyl. at the same time you don't want to blow raw mixture out either. each motor motor will require it's own combination.

Now back to the regularly programmed discussion. FWIW.

So its almost like your generic off the shelf supercharger cams, with an additional 10-12 degrees of exhaust duration, may or may not be warranted, depending on the exhaust ports capabilities to purge the spent charge?

Ive always been under the understanding, that too much overlap on a supercharger cam, will allow boost pressure to escape out the exhaust valve. BUT, I have seen some guys use 110LSA cams with blowers in big marine stuff. I wonder, if the compressor can support the loss of boost (big enough blower to be able to spin a little faster to make up for the loss), will running a 110LSA cam, aid in some additional cooling of the exhaust valves, but pushing some intake charge over them during overlap? Or am i thinking crazy?

Quote:

Originally Posted by MILD THUNDER (Post 4089765)

That would seem to work if you needed the cooling but Idealy (what I have found to work well on my blower set ups in the past) is add a slight bit more intake duration then exhaust, don't hang the Exhaust open to long ATDC like a N/A. and the term I like to use is "I keep the boost in the motor" again Head and Port and Chamber "WORK" Is critical and also the "Quench" lots of dyno testing to get what you are after.

I personally would not run a 110 LSA unless you plan on running the motor at a specific rpm range, most commonly too narrow of a
power band for all round pleasure boating use, and for me with my wet header exhaust why chance the reversion. JUST MY OPPINION.

Let me throw something else out there. We have discussed port size of the intake runner, intake pressures, flow, velocity etc. We know we like a nice intake/port match for a smooth transition, some intakes have plenum wedges/dividers.Good air speed and flow. Basically anything here, to aid in cylinder filling.

What happens, on a roots blown setup, when you add a intercooler between the compressor, and the intake manifold? Obviously it cools the air. But what about a restriction of airflow?

Also, we know a roots pushes the charge towards one side of the blower, and throw a delta opening in the mix, discharging air over a localized spot of the intercooler core. How much of that core surface area, is actually a working area?

most standard 60 deg twist blowers don,t have a delta opening but are open all the way through.on another note my whipple 8.3s have a delta opening as do most high helix superchargers.

Quote:

Originally Posted by MILD THUNDER (Post 4090122)

Gotta say it's pressure over flow.. Because cold pressurized air is better than warm air flowing better obviuosly. I think with the blower, the intercooler restriction is overcome because it is based on pressure ?

Quote:

Originally Posted by mcprodesign (Post 4089550)

Al these numbers are swell but a N A motor can only make so much pressure without being supercharged. take for inistance a pro stock Car. They have this huge air scoop and the thing has like a 6 in hole in the front. The biggeer the " air box" the more volume and increase in flow. it does not make boost . It can only take a few pounds of pressure ( in the airbox) because anything more does nothing. I think it's like 4 pounds of pressure or something. In this type of instance a pressurised "air box" or air scoop has the Carberators mounted inside the air box. This creats Air pressure and fuel pressure. Kinda like supercharging. But only like 4 pounds

You did not get what I was showing.

Forget the #'s.

The air we live in is under psi. 14.7 at sea level. To make it easier for people to see/compute pressure differential from sea level, we reference it as 0psi.

So, NA your engine is seeing pressurized air. All engines are seeing pressurized air.

So, what I was inferring, was, why do you have to drastically change port sizes when adding some more psi over atmospheric ? Especially if you are not greatly expanding it with heat or etc.

ok. I missed that. And I agree.
Also I think If you add boost ( Pressure) the port that needs attention is exhaust . Raising exhaust ports gets it out faster. But NA intake porting is key. ( i think). I learn every day. and thanks. Life without learning is no good and it cost a lot more :lolhit:

Quote:

Originally Posted by SB (Post 4090707)

Higher pressure gives the air higher density and bigger flowresistance.
The combined volume in the intake parts works as a pressure accumulator that helps in keeping the useful pressure up in to the intake valve.

Quote:

Originally Posted by Don Johnson (Post 4089075)

My experience on a blown motor is put the best flowing heads your budget can afford. The more the heads flow, the less boost required to achieve your HP goals. I have upgraded heads on motors where everything remained the same except head port size/flow and experienced that boost went down at higher RPM and HP went up proportionally. That said, I agree that under most circumstances you cannot overhead a blown motor in a boat application unless the motor has an seriously undersized blower (blower is too small for the displacement). All componants do need to compliment and support each other.

Quote:

Originally Posted by MILD THUNDER (Post 4088474)

Good info guys. All valid points. Thanks for participating!

I've got an old vintage book here, written by Jim Davis, back when he was at B&M, and they were in development with their supercharger systems.. Long before all the cool cylinder heads were available like now. They did alot of back to back testing on some stuff. They took a typical 8:1 454 chevy engine, with GM oval port heads (2.06/1.72 valves), installed a 420 Mega Blower, with around 10lbs of boost, and a blower cam. The engine made around 626HP at 6000RPM. They then removed the GM oval port heads, and installed stock GM Rectangle port heads (2.19/1.88 exhaust valves), with no other changes. The engine made 718HP at 6000RPM.

I know this is dinosaur stuff, but I thought it had some interesting information.

I am really enjoying this thread/discussion. As I am working on my project for the last few years, some of you already know I am rebuilding some tall deck/4. 3/8" stroke x 4.50" bore, 557cid Roots Blown (TBS 14-71's) engines with inner coolers, Daytona Ignition system, and 5" tubular, dry stack, racing headers. A few years ago I was on this forum trying to make a decision on some AFR heads.

I'm the guy with the quest for a smooth idling engine even as it idles in neutral, and with long, in gear, 1-hour idling periods. So, it was around that time a few years ago that I ordered some AFR CNC ported 335 heads from Bob Madara of Marine Kinetics who is a true professional and very intelligent stand up guy. Since that time, I had decided to have the cylinders of the blocks bored to 4.600" bringing the CID from 557cid now to 582". Also, to complicate things further, I have also (since that time) decided to swap out my TBS 1471's for some Whipple 5.0L Superchargers.

So, the question is (again, sorry), even though my heads are the (brand new) Factory CNC ported AFR 335 heads, I am wondering now, if these AFR 335's are the correct size, i. e. too small for an engine with NOT just a Roots style supercharger, but now (most likely) a Whipple 5.0L supercharged engine???----of which by the way is extremely throttle responsive and makes lots of torque from off idle all the way up the RPM band. Should I now move up to the AFR 357 CNC ported heads? (I can always sell the other AFR 335 heads)-----or I am I in too much of a "gray area" or trying to split hairs to call it that close between the 2 head sizes for 582cid, 3500-4500rpm cruising range and @5800-6000rpm WOT---??? (fresh water/Great Lakes region). I think the Whipple will help much with my desired smooth idling quests----thankfully I have not ordered the cams from Bob yet. He will be getting a phone call from me about some of this stuff anyway, in the mean time it's fun to discuss.

Mild T, I am not trying to hijack your thread. I always like your input on discussions and I think it is completely appropriate for the discussion at hand. Anyone feel free to chime in---just looking for some input here and make it fun and interesting for everyone, thanx.

Quote:

Originally Posted by KAAMA (Post 4138120)

You will love the Whipple 5L deal. I have these on my motors with 39 pitch props and they are so well mannered, never die and idle without any surge, especially compared to my old boat motors, roots/carb deal. You will also love the power the 5 L makes compared to a roots deal. Big improvement in mid range and top end power.

You are very likely giving up some power with the smaller CC heads, that said I do not think it will be huge. The smaller CC heads will work and not cause any issues short of maybe having to slow down the blower enough if you want to run pump gas. With your CID motor it is damn near impossible to not make at least 1,100 HP on pump gas with the 5L Whipple unless you cam it way wrong....