Air Induction and Power Loss

[Mikelly]

So yesterday I spent from 0900 until almost 1PM at EB3's Dyno.  They use a Superflow Autodyn30 (  http://www.superflow.com/Dynamometers/Chassis/auto_dyn30.php  ) and we did multiple tests looking at our tune with FAST.  First thing we noticed is that the Air Hat and filter combo I was using was KILLING power... To the tune of 70 WHEEL HP and 80# ft. of torque.. KPA was down to 86 and our calculation showed that to be about 12inches of vacuum.  This unit was choking the motor badly.

 

Ignore the graphics in this image and just focus on the air hat and ducting. 

 

Moved to this air hat and gained 50% of the power back without doing anything other than adding additional fuel back into the mix, and by reducing our vacuum by about 4 inches:

 

 

That unit sits almost and inch taller and isn't as restrictive.  However, we still were losing 35HP and 40# torque from our previous baseline... And still pulling over 8 inches of vacuum. 

 

Here are the part numbers for these particular units from Spectra Products:

http://www.summitracing.com/parts/spe-9849/overview/

 

http://www.summitracing.com/parts/spe-98499/overview/

 

So what we're going to do is use the filter assembly base/Filter/lid from our old air box and let the motor draw the air in.  We looked at log temps under hood at the last event (got to love the FAST system) and we didn't see air temps at speed above 100 degrees.  Further testing on the dyno showed this to be the best solution for this application at the moment.  During testing we had extremely high humidity and air temps in the shop were in the upper 80s.   Again, with the air heating up due to the motor, temps were around 100 degrees at the inlet.

 

While we were testing we also studied the time it takes the car to go from 2-6K rpm during the tests we did.  I was floored when we saw that the above air intakes slowed that process with the worst offender by almost a second.  That gang is real world performance on a roadrace car, with SECONDS being left on the table.  The motor was getting choked down so badly that it simply couldn't accelerate quickly enough.  This is HUGE.

 

Figured I would share the experience and hopefully someone can learn from my mistake.  This weekend while I'm at the track I am going to play around with AFRs a little and read the plugs.  We have the car fat and safe in the upper 1/4 of the power band, so we are leaving a little power on the table.  Half way through the first day I'll see how that is going and adjust accordingly. 

 

Mike

Edited June 29, 2013 by Mikelly

[T-Bone028]

Mike to clarify; was the 70 hp loss based on the original spectre Air-Hat/filter combo versus no air-filter/hat? And then 35 hp loss with the less restrictive/taller spectre Air-Hat/Filter combo versus no air-filter/hat?

[jhm]

Thx for posting your results, Mike.....I'm using that exact same low-profile air plenum, and will now definitely need to rethink my intake system!!  Would appreciate it if you could keep this thread going as you continue to experiment with different setups.

r/John

[Mikelly]

The 70hp loss was with the low profile unit. No loss was with no air filter on it at all. Based on feedback from the shop owner who runs NHRA 10.5 inch class at 230mph, we are going with the least restrictive option.

[randy 77zt]

Nascar style cowl induction system?

[rsicard]

The 70hp loss was with the low profile unit. No loss was with no air filter on it at all. Based on feedback from the shop owner who runs NHRA 10.5 inch class at 230mph, we are going with the least restrictive option.

The dyno testing revealed that even the 4 inch plenum elbow STILL provided restriction?  What are the possible options other than NOTHING on top of the throttle body?  I have that 4 inch spectre elbow on my 383 stroker and your testing on the dyno has provided some insight into the air restriction.  This is going to  be a somewhat complicated situation to resolve.  What did that fellow doing the testing suggest for air intake?  Cut a hole in the hood, put a forward facing scoop over the large hole in the hood and a large circular air filter on top of the throttle body joined to the hole in the hood?  Or a large plenum from the throttle body up through the hole in the hood and then what??  Please advise.  Thanks.

[rsicard]

The 70hp loss was with the low profile unit. No loss was with no air filter on it at all. Based on feedback from the shop owner who runs NHRA 10.5 inch class at 230mph, we are going with the least restrictive option.

How about this solution, use a dual/elbow plenum made by Spectre and 4 inch tubes on either side up through the radiator support 4 inch hole to a funnel that attaches to the 4 inch air intake tube.  Spectre makes a 4 inch inline filter that can fit in series with the intake tubes going to the dual/elbow plenum on top of the throttle body.  In order to test this configuration, two LARGE squirrel cage blowers would need to be placed in front of each air intake funnel on each side of the front grille to simulate the car at air/speed on the track.  Yes there will be loss of intake air at lower speeds, and more intake air at higher vehicle speeds and more horsepower/torque.  Those are the trade-offs.

[Mikelly]

He told me that I would be better ducting with the ram air style setup I had previously with the big sealed box and ducts to the front of the car.   He also recommended ducting a custom box to an opening in the hood or something similar.  I'll be selling BOTH of those Spectra Air Hats if anyone wants one! 

 

Issue there is now with the hood vents I can't use it.  This is driving me closer and closer to 100% commitment in getting that LS1 built and in the car. 

 

And for those reading and wondering, this is the same dyno I've done all the tests on with this 383 stroker.  22 test runs over 3 different days between 2011-2013.

 

Mike

Edited June 29, 2013 by Mikelly

[rsicard]

Funnel, larger than duct size, the Ram Air from in front of the radiator support into two four inch ducts that end up in the throat of the throttle body.  There will be positive pressure at speed funneled into the two four inch ducts.  Use the rigid 4 inch ducts and elbows as they are less restrictive to flow than the flexible ducts.  Much thought given to this design.  No protrusions through the hood that increase overall drag negating the increase in power.  Going through the hood is more complicated.  

[Mikelly]

Yes, assuming you have the space under-hood.  By the way, according to the tuner, the flexible hose is HORRIBLE and causes more issues than most people are aware. 

 

 

Mike

Edited July 1, 2013 by Mikelly

[Mikelly]

How about this solution, use a dual/elbow plenum made by Spectre and 4 inch tubes on either side up through the radiator support 4 inch hole to a funnel that attaches to the 4 inch air intake tube.  Spectre makes a 4 inch inline filter that can fit in series with the intake tubes going to the dual/elbow plenum on top of the throttle body.  In order to test this configuration, two LARGE squirrel cage blowers would need to be placed in front of each air intake funnel on each side of the front grille to simulate the car at air/speed on the track.  Yes there will be loss of intake air at lower speeds, and more intake air at higher vehicle speeds and more horsepower/torque.  Those are the trade-offs.

 

You might find this hard to believe, but I also have that setup and it looks restrictive.  Yes, that's right.. I have FIVE different cold air intake setups...  Note of them are suitable for the job.

[TimZ]

Yes, assuming you have the space under-hood.  By the way, according to the tuner, the flexible hose is HORRIBLE and causes more issues than most people are aware. 

 

 

Mike

Yes, it is.  

On that note, did you try just the hat with no hose connected to it?  I'm wondering if the hose is the problem in the first place.  It's that accordion crap that f's up the airflow, and in your second pic it looks like it does a pretty sharp bend after the air filter.  You can get hose that is smooth on the inside, but you can't bend it as sharply (which is what you probably want anyway).  Or you could just fashion a hard piece from mandrel bent aluminum tubing (use the largest radius you can get away with) and use smooth straight hose sections to connect it to the motor and the filter can probably just slip onto the end.

 

Also, unless you have some kind of weird sensor scaling, 86kPa is more like 6 inHg of vacuum, which is still way too much.

Edited July 1, 2013 by TimZ

[rsicard]

You might find this hard to believe, but I also have that setup and it looks restrictive.  Yes, that's right.. I have FIVE different cold air intake setups...  Note of them are suitable for the job.

Yes, it is REALLY hard to believe that a dual 4 inch plenum with smooth tubes feeding it does NOT have more volume than open throttle body with no hat at all at speed.  At low vehicle speed a small fraction of loss of horsepower/TQ is not that serious.  When at speed with RAM air effect into the dual plenum, should yield more volume past the throttle body than the vehicle sitting still and no hat on the throttle body.  The vehicle aero resistance at speed becomes the primary factor retarding acceleration.

[RebekahsZ]

None of the "ram air/cold air" effects that you fellas are talking about will show up at the dyno unless you have an 8' wide 150mph fan - gonna have to go to the track to test that. That would take a pretty big time commitment. And you couldn't test hp directly-just ETs (lots of confounding variables). Would cowl induction kill your aero plan? That provides increased air pressure as cold air piles up at the base of the windshield but has unlimited flow (zero restriction), plus you can keep your best air cleaner base as proven by the dyno?

[rsicard]

It was already suggested to simulate ram air flow.  It would have to be tested at the track or in a wind tunnel.  How much more positive is airflow at the base of the windshield versus that which is taken  at the front grille opening?  Has this been instrumented to see what the difference is?  NASCAR sprint cup cars use the air intake at the base of the windshield.  Has NASCAR mandated that intake air CANNOT be had at the front of the car?  More questions than answers.  Put an absolute pressure sensor in the two locations and instrument log the differences at speed down a 10K foot runway for comparison.  See which location has more relative pressure readings.  Aircraft put the pitot tube out in the airstream, NOT at the base of the windshield.

[NewZed]

Seems like you could split the intake system out from the ram air effect.  Nobody builds a flow bench for intake systems?  You could test the pleated hose, the hats, and combinations, with no dyno expense.

 

A shop vac and a sensor could at least rank the various combinations.

 

 

Sensor, manometer... whatever works.

Edited July 1, 2013 by NewZed

[RebekahsZ]

I'm just trying to keep it simple.

[Mikelly]

Tim, Unfortunately We indeed DID test the larger unit without the piping. The loss of power was the same as with the piping. The thought is the "carb style" efi intake/Tbody style are horrible for a setup like that.

My fitment issues boil down to getting around the strut bar. Maybe I need to spend more time revamping that as well, as I sort the other issues out.

I appreciate the comments from the group here. THIS is why I wanted to share this info.
 

Yes, it is.
On that note, did you try just the hat with no hose connected to it? I'm wondering if the hose is the problem in the first place. It's that accordion crap that f's up the airflow, and in your second pic it looks like it does a pretty sharp bend after the air filter. You can get hose that is smooth on the inside, but you can't bend it as sharply (which is what you probably want anyway). Or you could just fashion a hard piece from mandrel bent aluminum tubing (use the largest radius you can get away with) and use smooth straight hose sections to connect it to the motor and the filter can probably just slip onto the end.

Also, unless you have some kind of weird sensor scaling, 86kPa is more like 6 inHg of vacuum, which is still way too much.

Edited July 2, 2013 by Mikelly

[Mikelly]

BTW, I stopped by Pepboys yesterday and bought one of these (Yes air intake setup #6):

 

http://www.jegs.com/i/Spectre/865/47622/10002/-1?parentProductId=

 

I figured the top being filter material can only help the situation.  Car is loaded up and ready to depart to VIR this afternoon.  I'll report back over the course of the next two days.  We will be playing with AFRs and timing throughout the coming days if all goes well!

Mike

[peej410]

The filter top may help or hurt. Hard to say because you are EFI most carbs dont like the filter top because it disturbs airflow. Howd you make out at the track today?