Cold air intake system for 496 engines can add 8-12% HP.
10-31-2006, 10:36 PM
#1
Cold air intake system for 496 engines can add 8-12% HP.
This is a long post but I am really excited to have an affordable product that really does something for all the 496 owners out there.
You may know that some 496 owners who have checked their manifold air temp with a scanner have seen high temperatures that can easily cost them 8-12% of the rated HP. Usually we are trying to add to the rated HP, but getting back lost HP is just as beneficial.
The math is simple. An engine rated at @ 77F (SAE) will only make 88% of its rated HP if air temperature entering the engine is 150F. You have to add 460 to each temperature because the equation is for absolute temperatures.
Density ratio = (77+460)/(150+460) = 0.88
Under these conditions a 496 Mag HO rated at 425 HP would only make 375 HP, a loss of 50 HP. Even at 125F the loss is 35 HP. As a side note the Mercury application manual specifies 176F as maximum allowable engine compartment temperature.
I suspect that this air temperature problem is more widespread than we know. It's only because you can throw a scanner on an EFI engine that we are aware of it at all. A simple test, described in the thread on minimum air vents, is to run with your hatch up a couple inches and see if you get more RPM. If you do then you need more cold air.
The answer is obvious; get cold air directly to the engine intake. Air density increases and you get the power back. BUT... you must design the intake so that it is no more restrictive to air flow than the original flame arrester, otherwise you sacrifice some of your air density gains to pressure losses.
We just tested the design pictured below against the stock flame arrester with the following results:
Configuration CFM @ 1.5" Hg
Stock flame arrester on throttle body 769
Cold air intake on throttle body 783
Cold air intake with water resistant filter wrap 767
These results show that our cold air intake is no more restrictive than the stock flame arrester, so air density gains will not be lost to increased pressure loss through the system. This means that gains of 35-50 HP are realistic based on the temperatures noted above.
I designed this universal cold air intake for OSO member Dave(Nordicflame). I don't know of any more cost effective way to add 35-50 HP to these engines. It's cheaper than hood scoops and preserves the sunpad for your lady friends. The air box can be assembled for either stbd or port. You have to shape the walls of the air box to match the sides of your boat under the gunnels. Single engines get a section of straight tube to reach the gunnel.
The second drawing shows how the air box tucks in beside the heat exchanger on the 496. You need a minimum of 9" from the throttle body to the bulkhead for the air box to fit.
The last drawing shows how the kit can be fitted to common engine compartment layouts. The assumption is that the air box location is close to the engine compartment vents on the side deck and gets first stab at the cold air entering there. I know that not all boats have vents in this area but if you need to add vents this is the best location to do it.
Final point; for the best air flow I brought the tube directly to the throttle body and this prevents the use of the stock plastic engine cover. You either have to trim it to clear the tube or replace it with a custom engine cowling that does not overhang the throttle body. If there is enough interest in this product we will tool up for a custom engine cover that integrates nicely with the cold air kit and maybe doesn't look as wild as some of the ones I have seen in Hot Boat lately.
Price...we are thinking $499.00, which is about $100 more than a car kit. We have to make this system stronger to take the pounding in a boat and it has to be polished aluminum not black plastic.
OK everybody, I look forward to hearing your comments.
Thanks,
Tom
You may know that some 496 owners who have checked their manifold air temp with a scanner have seen high temperatures that can easily cost them 8-12% of the rated HP. Usually we are trying to add to the rated HP, but getting back lost HP is just as beneficial.
The math is simple. An engine rated at @ 77F (SAE) will only make 88% of its rated HP if air temperature entering the engine is 150F. You have to add 460 to each temperature because the equation is for absolute temperatures.
Density ratio = (77+460)/(150+460) = 0.88
Under these conditions a 496 Mag HO rated at 425 HP would only make 375 HP, a loss of 50 HP. Even at 125F the loss is 35 HP. As a side note the Mercury application manual specifies 176F as maximum allowable engine compartment temperature.
I suspect that this air temperature problem is more widespread than we know. It's only because you can throw a scanner on an EFI engine that we are aware of it at all. A simple test, described in the thread on minimum air vents, is to run with your hatch up a couple inches and see if you get more RPM. If you do then you need more cold air.
The answer is obvious; get cold air directly to the engine intake. Air density increases and you get the power back. BUT... you must design the intake so that it is no more restrictive to air flow than the original flame arrester, otherwise you sacrifice some of your air density gains to pressure losses.
We just tested the design pictured below against the stock flame arrester with the following results:
Configuration CFM @ 1.5" Hg
Stock flame arrester on throttle body 769
Cold air intake on throttle body 783
Cold air intake with water resistant filter wrap 767
These results show that our cold air intake is no more restrictive than the stock flame arrester, so air density gains will not be lost to increased pressure loss through the system. This means that gains of 35-50 HP are realistic based on the temperatures noted above.
I designed this universal cold air intake for OSO member Dave(Nordicflame). I don't know of any more cost effective way to add 35-50 HP to these engines. It's cheaper than hood scoops and preserves the sunpad for your lady friends. The air box can be assembled for either stbd or port. You have to shape the walls of the air box to match the sides of your boat under the gunnels. Single engines get a section of straight tube to reach the gunnel.
The second drawing shows how the air box tucks in beside the heat exchanger on the 496. You need a minimum of 9" from the throttle body to the bulkhead for the air box to fit.
The last drawing shows how the kit can be fitted to common engine compartment layouts. The assumption is that the air box location is close to the engine compartment vents on the side deck and gets first stab at the cold air entering there. I know that not all boats have vents in this area but if you need to add vents this is the best location to do it.
Final point; for the best air flow I brought the tube directly to the throttle body and this prevents the use of the stock plastic engine cover. You either have to trim it to clear the tube or replace it with a custom engine cowling that does not overhang the throttle body. If there is enough interest in this product we will tool up for a custom engine cover that integrates nicely with the cold air kit and maybe doesn't look as wild as some of the ones I have seen in Hot Boat lately.
Price...we are thinking $499.00, which is about $100 more than a car kit. We have to make this system stronger to take the pounding in a boat and it has to be polished aluminum not black plastic.
OK everybody, I look forward to hearing your comments.
Thanks,
Tom
11-01-2006, 08:06 AM
#2
Registered
Re: Cold air intake system for 496 engines can add 8-12% HP.
To the top.
This piece appears to be typical of Tomcat - well thought out and worthy for many to use.
Good job Tomcat!
This piece appears to be typical of Tomcat - well thought out and worthy for many to use.
Good job Tomcat!
11-01-2006, 10:39 AM
#3
Registered
Re: Cold air intake system for 496 engines can add 8-12% HP.
This is a good idea. My friends and I have been thinking about this topic alot. The problem is every boat is different and has to be customized for every model of boat and engine configuration. I have a 236 Baja with side air intake on both sides. My engine is a BBC with aftermarket Holley MPI. It would need a air hat of some sort to connect to the tube. Does your product have 4" tubing?
Do you think it is nessessary to seal off the air intake or could it just be placed next to it?
Thanks,
Jeff
Do you think it is nessessary to seal off the air intake or could it just be placed next to it?
Thanks,
Jeff
11-01-2006, 12:51 PM
#4
Re: Cold air intake system for 496 engines can add 8-12% HP.
The typical BBC single carb layout is the next one on the drawing board.
Yes, you need a "hat" and yes the tube is 4" diameter.There are a variety of hats on the market and we need to find the best one because that sudden transition is important to the overall pressure loss. On a stock BBC like a 454 around 400 HP we can use the same tube dia and air filter, but for higher HP applications I suspect we may need bigger tube and air filter. Only time on the flow bench will tell.
Trimming the air box to match the side of your boat is a custom operation but once we have a template for a particular model we could offer that as a specific kit. Sealing the top and sides of the air box to the side of the boat near the vent is important and we will provide rubber weatherstripping to do so. There are slots in the bottom of the air box to get rid of water that may splash in the vent.
Yes, you need a "hat" and yes the tube is 4" diameter.There are a variety of hats on the market and we need to find the best one because that sudden transition is important to the overall pressure loss. On a stock BBC like a 454 around 400 HP we can use the same tube dia and air filter, but for higher HP applications I suspect we may need bigger tube and air filter. Only time on the flow bench will tell.
Trimming the air box to match the side of your boat is a custom operation but once we have a template for a particular model we could offer that as a specific kit. Sealing the top and sides of the air box to the side of the boat near the vent is important and we will provide rubber weatherstripping to do so. There are slots in the bottom of the air box to get rid of water that may splash in the vent.
11-01-2006, 01:45 PM
#5
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Re: Cold air intake system for 496 engines can add 8-12% HP.
Tom
Your application for this is very similar to what I did 15 years ago with my '81 Grand Prix. I remove the 6 cyl and dropped a 375hp 350 with NOS (500hp) into the car. The major problem I had was the headers heating up the underhood temps and causing a loss of power. I resolved this by creating a shroud around the air cover and running twin 3" air inlet hoses from in front of the rad. There was a noticable (1/2 sec) improvement in performance at the track. FYI street tires at 18lbs, we ran a best time of 12.08, corrected from zero reaction).
What a great idea!
Trev
Your application for this is very similar to what I did 15 years ago with my '81 Grand Prix. I remove the 6 cyl and dropped a 375hp 350 with NOS (500hp) into the car. The major problem I had was the headers heating up the underhood temps and causing a loss of power. I resolved this by creating a shroud around the air cover and running twin 3" air inlet hoses from in front of the rad. There was a noticable (1/2 sec) improvement in performance at the track. FYI street tires at 18lbs, we ran a best time of 12.08, corrected from zero reaction).
What a great idea!
Trev
11-01-2006, 06:47 PM
#6
Registered
Re: Cold air intake system for 496 engines can add 8-12% HP.
I brought this up on another board and asked about how an innercooler would work on a non-supercharged engine. The general consensus was the air restriction of the innercooler would offset the cooler air and somehow venting outside air would be a better idea.
I was actually considering buying a 4" turbo hose kit and making something that would go directly to an outside vent from the intake on my 502 mag. But, my main concern was keeping the flame arrestor and keeping water out.
Tomcat great thinking outside the box!
I was actually considering buying a 4" turbo hose kit and making something that would go directly to an outside vent from the intake on my 502 mag. But, my main concern was keeping the flame arrestor and keeping water out.
Tomcat great thinking outside the box!
Last edited by onesickpantera; 11-01-2006 at 06:50 PM.
11-01-2006, 06:48 PM
#7
Registered
Re: Cold air intake system for 496 engines can add 8-12% HP.
Hi Tomcat I Was Told You Are The Man To Talk To
I Have A 598 Bbc I'm Putting A M4 Pro-charger On It This Winter What Carb And Cam Would U Run In Something Like This I'm Looking For 1100hp Thank You Dennis
I Have A 598 Bbc I'm Putting A M4 Pro-charger On It This Winter What Carb And Cam Would U Run In Something Like This I'm Looking For 1100hp Thank You Dennis
11-02-2006, 10:21 AM
#10
Re: Cold air intake system for 496 engines can add 8-12% HP.
The ideal setup is what you see on Fountains.
If you are above the rubrail you won't normally pick up water, but anybody that races with a forward facing scoop knows that you eventually get water in the scoop. With scoops placed above the engine this can be a problem. A forward facing vent on the side deck can take in water without hosing down the engine.
We are investigating different styles of add-on vents. Nordicflame is adding vents to his boat. I don't have a picture but I'll ask him to post one.
If you are above the rubrail you won't normally pick up water, but anybody that races with a forward facing scoop knows that you eventually get water in the scoop. With scoops placed above the engine this can be a problem. A forward facing vent on the side deck can take in water without hosing down the engine.
We are investigating different styles of add-on vents. Nordicflame is adding vents to his boat. I don't have a picture but I'll ask him to post one.
