Grimmspeed Intake without airbox lid?
 

I've got a Grimmspeed intake on my 13 BRZ with HKS front pipe and Tanabe Concept G cat-back.


When I run the intake without the airbox lid the car actually seems more powerful (and sounds better). My intake temps (IAT) go up to the 140s (F) with the lid OFF versus ~90s with the lid ON as shown by my Torque Pro App with OBD2. I'm running the stock unmodified snorkel and stock tune.


Could I actually be making more power WITHOUT the lid and hotter intake temps or is this in my head?

Pic of lid removed

"Hot air intake"

If anything you should be making less power due to the higher intake temps.

With an intake and no tune, gains are very minimal.. in the range of 1-2hp if any at all.

The biggest thing I notice is the throttle response with the lid ON shows hesitation. Is it possible that opening the lid gives the filter immediate access to air (albeit HOT air) and helps in this regard?

I know it does seem strange!

Not sure which page, but Grimmspeed discussed having the box lid on and off.
http://www.ft86club.com/forums/showthread.php?t=78902

Heat is the enemy, your engine is more efficient with cooler air.

Avtually, you gain with an intake and NO tuning.
You make the afr leaner and you gain some hp

If you tune there is less gain from the intake compared to the stock intake, you actually gain from the tune itself

I remember a dyno plot for a XBrand of header a while back that had a similar intake installed on the car. They then took the lid off and the car made another 4-5hp on the dyno with the fan going of course. I'll try and dig it up later today.

i ran it with the lid off for a few months. you're right it does sound great but doesn't make much more power that way. i put it back on when i was having AFR problems (this may also have been from over-oiling the filter). better to just buy an intake that was designed for open box like blitz or k&n

A full intake with lowered restriction from both the tube and the box and filter makes less power than even a drop in filter? Do you have any info to back this up, because we have an extremely long R&D thread that shows the opposite of this.


Yup, it's not on that thread, but rather the research and development thread (much much longer with a compilation of over 140 dyno pulls with everything from prototypes to competitor intakes, to drop in filters, to repeatable gains with the snorkel trimming).

But the gist of it was: I don't think that we ran without the lid, or without the box, we removed the snorkel from the system. In this circumstance the AITs raised and the power production was back down to about stock level. I'll explain why in the next reply.

Hot air is less dense, so its power potential is lower. You're seeing a 50 degree delta between lid on and lid off. Putting science aside and strictly looking at ECU strategy you are definitely making less power because the ECU is pulling timing. The reduction in timing to prevent knock on these high compression engines has a more substantial impact on power production than air density. I can safely say that through both testing (which we've posted) and experience that you are definitely not making more power with the higher intake temps.

But for a "fun" engineering side note: The engine can be more efficient with higher intake temperatures as fuel atomizes better. I think there is a fairly recent chevy malibu which under cruising conditions heats up the intake air to slightly increase fuel economy. I believe it does not maintain this change during wide open throttle, as what we just discussed about power production is true. Just something to look into if people are interested in learning something.

I know that this is what people continually recite over and over on forums, and to some extent it is true. However, as we've shown time and time again we made power without changing the AFR, as our intake maintains nearly identical MAF characteristics. The increase in power is from a decrease in restriction, not from leaning out AFRs. Drop in filters tend to modify the AFRs to be leaner as we've shown and will do exactly what you've described as the car adjusts the AFRs over time.

I hope I've sufficiently answered your questions in my replies. What you're experiencing with "throttle response" is most likely an increase in noise from removing the lid. The engine certainly isn't starved for air as the entrance in the snorkel is more than ample enough to support the airflow needs these cars have, and then some.

The situation someone mentioned where they removed the lid on the dyno is both realistic and unrealistic for a couple reasons. Obviously it's unrealistic because you cant drive around with your hood open, but you could drive around with it completely off. It has some realism though because the air intake temperatures on a dyno will get out of control fast without an adequate time to cool off as there are very few dynos that can replicate the type of airflow through the front of the car at speed. This increase in power likely wasn't a result of mass of air that was now available, but rather the temperature of it measured at the MAF.

Hopefully this helps. You're obviously free to do what you'd like. If you like the way it looks, or think it sounds cool, but it certainly isn't helping produce more power, and the metric of "throttle response" is not something that can be modified in this way.

Chase
Engineering

your intake do lean the afr at least on low rpm as shown in your own dyno graph though

In that transition at low RPMs, I'll agree that it did. However, there is absolutely zero power to be gained from that brief "leanness."

If leaning the AFRs is how it allegedly makes power, and there is absolutely zero gain in that region, but gains where the AFR matches, is your claim still accurate?

Chase
Engineering

Thanks for the informative reply, Chase. Must be in my head then!

:thanks: