SLP Ultra Z ram air hood vs. SS ram air hood...

[Josh '95 Z28 A4]

Well until I read the responses to my last post about a ram air hood for my '95 Z, I thought I wanted the factory SS ram air hood. But judging from that picture that Barry 94 Formula posted of the Camaro with the Ultra Z hood, I think that one looks just as sweet. Now Hyper also mentioned how the SS is like a fancy looking cold air induction whereas the SLP hood is a functional ram air. Does that in any way give the SLP hood an edge in performance gains? How do both hoods compare with the SLP cold air intake?

[Injuneer]

Both the standard "SS" hood and the "Ultra Z" hood (similar to a WS6 hood as far as air flow) will be pulling "cool" air from above the hood. This air will probably be cooler than the air pulled in from an "under the bumper" intake, since the air close to the pavement is heated by the pavement. The black asphalt at a drag strip can easilly top 140degF on a sunny summer day.

The next question is how good is the air flow into the opening in the hood. Again, my gut feel says the leading edge location of the UltraZ/WS6 style hood will have the edge. As the air starts to flow over the hood, a slow moving, low pressure "boundary layer" builds up, isolating the hood scoop from high velocity/high pressure air flow. In theory the NACA duct opening shape peals away this boundary layer, and allow high pressure air to enter the scoop. The SS hood is sort of a "raised" NACA profile, but who knows how effective it is. Pro Stock racers have to put the scoop at least a foot above the hood to get the best flow.

Then there is the actual amount of "pressure boost" that the hood can provide at high speeds. Using the concept of "velocity head" it can be shown that at 100MPH, a forward facing scoop will see a pressure boost of about 0.18psi, or a little more than 1% of normal barometric pressure. How much of that pressure is "recovered" by the scoop is a function of the shape and efficiency of the openings, and it is unlikely that there is any more than a 1% pressure gain (= 1% HP gain) at 100MPH. That's a maximum potential of 3HP on a stock engine. Since velocity head is proportional to the square of the speed, at 50MPH, that gain drops to 1/4 of the gain at 100MPH, or only 0.75HP.

The Ultra Z/WS6 hood is a fairly direct shot into the air filter. There are two baffles to knock water out, so this costs pressure loss. But past the baffles its a straight shot. For the SS hood, I suspect they still use the baffles (not sure though) and then the air ducts turn the air 180-degrees to get it to the front of the engine, then another 180-deg to get it into the throttle body. This has got to loose pressure. So again, the Ultra Z/WS6 hood seems to have the edge.

I'd say the Ultra Z/WS6 style hood offers a small edge over the SS. Whether this is a big enough difference to overcome one's preference on "appearance" is up to the individual.

Since my car is not street driven, I have cut out the baffles, and opened up the air box to the max, deleted the MAF sensor (I run speed-density) and use the Fernco 3" sewer pipe connector... got to be as straight a shot as possible - and it makes a nice place to spray 275HP of nitrous .

[wolfdogs]

agree 1,000% with Injuneer here.. . the Ultra Z hood is much more efficient than the ss hood......... much more.

[Joe 1320]

Yep... total agreement with Fred. Even in the looks dept., the Ultra Z hood offers a little more exclusivity.

Fred's calculations on the ram air effect are pretty close. Ever notice that the last LT1 Vettes were rated at 300 HP, yet the same configuration in an f-body (WS6) is 305 HP? Same filter configuration, but the WS6 has the openings in the hood for the ram air, while the Vette takes it's air from underhood. At speed, the gain isn't much, but at least it is a gain.

[Injuneer]

SLP has always had a couple of their "development" cars at the GM High Tech Performance, and SLP Day events at Englishtown. These cars are generally Z28's with the UltraZ style hood. That would seem to indicate what SLP thinks is best.

[Hyper94uznj]

If somebody will host for me I have a couple pictures of my Ultra Z hood, as long as you don't mins seeing the car up on barstool size jackstands.

[Joe 1320]

Originally posted by Hyper94uznj
If somebody will host for me I have a couple pictures of my Ultra Z hood, as long as you don't mins seeing the car up on barstool size jackstands.

Sign up for this: http://www.imagestation.com/

You'll even be able to hot link the pics. It's free and you'll be up and posting in minutes.

[ChrisL]

Originally posted by Injuneer
That would seem to indicate what SLP thinks is best.

the UltraZ is at etown often because SLP Performance Parts is in Toms River, and SLP Engineering is in Troy, Michigan.

SLP Engineering has had their cars down for the annual SLP CAD event, but not for the GMHTP shootouts.

Dont forget, though they share the same owner, and the letters "SLP".... SLP Eng and SLP PP are seperate operating companies. Engineering doesnt market much at race events since their products are not primarily for racing.

[Injuneer]

Originally posted by Hyper94uznj
If somebody will host for me I have a couple pictures of my Ultra Z hood, as long as you don't mins seeing the car up on barstool size jackstands.

sign up with Central Jersey Camaro/Firebird Owners, and Jim Hogan will give you space on fbody.com.

Not sure I understand the point on the post about the difference between SLP PP and SLP Engineering. The hoods are done in Toms River. A couple of our "club" cars have been used by the Toms River facility to develop and install prototype hoods. CJC/FO's Diane Walczac had her car used for the LS1 Ram Air HO hood, and the car was exhibited for two years at SLP Day with the hood. I know I vave seen SLP cars at GMHTP over the past 4 years. Not in displays, but racing. We (CJC/FO) originated and then co-sponsored the "Fastest Stock Suspension F-Body" events at E'town in 2001, and SLP was a major sponsor, and brought their cars.

[ChrisL]

Originally posted by Injuneer
sign up with Central Jersey Camaro/Firebird Owners, and Jim Hogan will give you space on fbody.com.

Not sure I understand the point on the post about the difference between SLP PP and SLP Engineering. The hoods are done in Toms River. A couple of our "club" cars have been used by the Toms River facility to develop and install prototype hoods. CJC/FO's Diane Walczac had her car used for the LS1 Ram Air HO hood, and the car was exhibited for two years at SLP Day with the hood. I know I vave seen SLP cars at GMHTP over the past 4 years. Not in displays, but racing. We (CJC/FO) originated and then co-sponsored the "Fastest Stock Suspension F-Body" events at E'town in 2001, and SLP was a major sponsor, and brought their cars.

no big deal, just sayin.... The SS, Firehawk, GTX, etc, hoods arent done in NJ. They are done in Michigan. The SLP HO hood for Firebirds and the UltraZ Camaro hoods are done in NJ.

[TimeLord]

Hello !!!

[Kevin - Blown 95 TA]

Now, that's what I call a SIGNATURE !!