Converting an L8T hood to a functional L5P intake (functional hood scoop).

[Crazy Canuck]

12 hours ago, 64BAwagon said:

The 2024 L8T air intake setup is light years ahead of anything GM has previously produced on a gas truck. Before I got my SG3 I had wondered how efficient the gas intake system was. During my 4k trip I monitored air intake temp regularly. City and highway both towing and non towing and found the IAT to be within 1 degree of ambient temp in all situations. To me that indicates air intake efficiency I have never seen before in a stock setup. After seeing this I abandoned any thoughts of working on improvements.  As a comparison. My 2005 LLY Dmax when stock and no mods always showed at least 20 degrees higher than ambient at highway speeds, in traffic sometimes 30-50 degrees higher. After modifying the airbox and adding a ducting kit for more outside air I was able to improve it but never got it anywhere near the numbers on this gas intake. 

I believe that trying to use the diesel setup on the hood scoop could end up disrupting the gas airflow and might actually pack air where you dont want it on the gasser. I admit I had the same thoughts on making that intake on the hood operative but after spitballing it in my head I didnt think I could get any positive results from it. 

I think the only reason that trim piece exists on the gas trucks is because GM needed something to occupy that space on the non diesel applications. Rather than create two hood designs they used the same piece blocked off.  

Not doubting what you are saying but It would be interesting to see an apples to apples comparison with a '20+ diesel vs the L8T for IAT.  I wouldn't think GM would add the cost of the scoop/plumbing if it wasn't a benefit.  The bean counters would have eliminated it otherwise or they would all be just for show.

[Epsilon Plus]

The nature of the design is really that good on the L8T though. Isolated from everything else, in its own sealed air "tray" at the leading edge of the hood, direct shot to the sealed air box. 

 

I think the scoop is for the demand of extra air needed to feed the 900+lb tq of the big D. Also because it's a sales gimmick in a very competitive market. Gas trucks are mostly fleet purchases. Cost savings on the hood stuff over 100s of thousands of trucks is a big deal and fleets don't care that it's not there.

[64BAwagon]

10 hours ago, Crazy Canuck said:

Not doubting what you are saying but It would be interesting to see an apples to apples comparison with a '20+ diesel vs the L8T for IAT.  I wouldn't think GM would add the cost of the scoop/plumbing if it wasn't a benefit.  The bean counters would have eliminated it otherwise or they would all be just for show.

Just out of curiosity I would also like to see the flow ratings on the diesel vs gas. I assume (probably shouldnt) that the CFM capacity of the L8T intake is sufficient for its maximum requirements. I am glad to see the air temps are at or very near ambient but flow numbers (which I doubt we will ever have access to) would tell the whole story. 

No matter, this setup is way ahead of any of the other GM trucks I have owned or worked on.

 

@Epsilon Plus  I am seeing a lot more gas engine HD trucks in the RV world than I ever saw before. In the past it was dominated by the diesel. Now I am seeing a lot more gas engines. I had a number of people ask me about my truck and the gas engine. Based on my conversations a lot of people are growing tired of the DEF, cost, low reliability and complexity of the modern diesels

Edited April 16, 2024 by 64BAwagon

[Epsilon Plus]

I think money might saved on the vent with some elbow grease. If you look close between the closed and open on the back, it looks like the closed could be an overlay fastened to an open one. Might try to chop mine up with a Dremel or blade in the front to open it vs spending over $150 on essentially what I have already. If I mess it up, oh well I needed to get one anyway.

 

 

 

 

Those bolts listed are outrageous at $10-14 each and some sites say unavailable. I'm going to try some Amazon ones that are a touch shorter. GM uses zinc M6x1.0x30mm. I got like 20 of them dog nose with the washer on them like stock for peanuts in comparison, although they are M6x1.0x25mm. Also the nut retainer things they screw into. So far with the bolts/nuts, hood blanket, push pins, air box, and front duct cover thing I'm into it $206.05 with 15% off and everything but the Amazon bolts/nuts shipped to a dealer to avoid the massive shipping costs on the various discount sites. The scapped OEM version of this posted by newdude lists for $800+. 

 

If I can mod my stock hood vent, get the airbox to sync up and collect the main and upper duct I could get this done for half of that potentially. 

 

Stay tuned.

 

 

Edit: After looking at my vent from the front up close I think it would be too much work to cut clean. Sickening to spend $112 + shipping on a new one but it is what it is. 

 

Edited April 16, 2024 by Epsilon Plus

[Epsilon Plus]

Found a lower duct. Out of stock everywhere except a single dealer (tons of dealers around here). However, I doubt they have this "in stock" on the shelf. It let me order it though even though dealers less than 10 miles away it would not. GM parts research and ordering is such a laborious and confusing mess.

 

 

Edit: I'll be darned. Was on the shelf I guess. Got a ready for pickup email lol. Dunno why they would have that laying around, but there ya go.

 

After some tail chasing and gathering from 3 different sources, I've got everything ordered. Beyond what may be required to mod the airbox to TB connection, and relying on those ducts coming with the insulators and drain plug attached, I'm all in right now at $598.21. Compare that to the unreleased GM version at a discounters listed price of $809.68 pre shipping ($995 MSRP). If I can get this all to work I'll post a list of exact parts needed for the full swap.

 

$600 isn't chump change to spend on a non-performance adding intake but at least I won't be embarrassed by the Toyota-like giant fake hood scoop any longer (barring that all this works!).

Edited April 16, 2024 by Epsilon Plus

[Epsilon Plus]

After an annoying process involving GM corporate and phantom missing parts I finally have all the things I need to keep going. Upon brief inspection it looks like the diesel airbox might be a direct swap for the gas one. That has me considering returning the GM box and getting an S&B dry to eliminate the Hemholtz resonator. I can't imagine the throttle bodies are in the same spot though and the aftermarket intakes have solid formed tubes. It might involve cutting and making a custom silicone intake tube like I thought I had to do anyway. So, on third thought, if this is drop in, I'll stay with GM.

 

Stay tuned for results and a complete part numbers needed list if this all works out. Looks promising though.

[Epsilon Plus]

Front intake feed tube is different.

 

Gas is ~6.25x3" OD

 

Diesel is ~4.5x2.75" OD

 

When newdude mentioned a separate box PN for the cancelled gas intake kit, a larger lower opening to match the stock gas feed tube was probably it. Everything else like MAF placement and bellows looks to line up though.

 

The saga continues...  84670713 Intermediate Intake Air Duct ordered. Should be the last part.

 

Edited June 8, 2024 by Epsilon Plus

[Pryme]

The one thing that will be nice when you get this done is not having water spraying up onto the windshield while raining or after washing the truck. 
 

I use my leaf blower on high after washing the truck to blow out the fake scoop throughly 

[bruceb58]

I am not sure I see the point of doing this other than seeing if it can be done or not. 

[Another JR]

1 hour ago, bruceb58 said:

I am not sure I see the point of doing this other than seeing if it can be done or not. 

Ssshhhh!  We don’t say that here.  

[Epsilon Plus]

Good idea to get this ~$15.00 hood insulator sent to a dealer for pickup or get killed on shipping: 

 

 

On a side note, crazy how cheap it is. There's singular bolts (that I substituted with Amazon stuff) that GM charges more for.

Edited June 9, 2024 by Epsilon Plus

[gemarsh]

47 minutes ago, Epsilon Plus said:

Good idea to get this ~$15.00 hood insulator sent to a dealer for pickup or get killed on shipping: 

 

 

On a side note, crazy how cheap it is. There's singular bolts (that I substituted with Amazon stuff) that GM charges more for.

Lucky you got it. It wasn't long ago that was some trucks had it omitted due to supply line issues. 

[Epsilon Plus]

The bones underneath. Almost done, just waiting on that front feed pipe to drop the box in and finish it all up.

 

[BCGM]

Is this basically turning the air flow into a RAM Air type of delivery which was popular on muscle cars when I was a teen .   Oh its got RAM Air !  Question . Did RAM Air add Horsepower . 

 

[Ben Jardine]

Love this thread i been fallowing along . Cant wait to see finished product and some updates