How restrictive is the stock TPI airbox/lid?
04-17-2002, 08:07 PM
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Car: '87 IROC
Engine: LT1 350
Transmission: 700-R4
How restrictive is the stock TPI airbox/lid?
I have a well modded LT1 in my IROC, and for now I'm using a stock TPI airbox with K&N's and the bottoms cut off for air to get in through the grill. Will a Cold Air Induction yield better results for me? And what CAI kit should I look into, with the intake sitting a good few inches lower than the stock TPI setup (Speed Density).
BTW, I do have very good flowing heads,exhaust, LPE 219 cam, and a 58mm TB. So this motor can breathe!
BTW, I do have very good flowing heads,exhaust, LPE 219 cam, and a 58mm TB. So this motor can breathe!
04-18-2002, 01:46 AM
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How restrictive is the stock TPI airbox/lid?
And what CAI kit should I look into, with the intake sitting a good few inches lower than the stock TPI setup (Speed Density).
Some stainless steel 3" exhuast tubing should polish out real Nice, a few Rubber Elbows from your local plumbing store and your Golden.
04-18-2002, 08:28 AM
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Car: 04 GTO
Engine: LS1
Transmission: M12 T56
I still to this day have not seen any back to back testing of the stock filter set-up vs. something different. There have been more than a few folks running 11s and beyond with it though. So apparently it's not 'that' restrictive.
Since it's so easy to switch from one set-up to the other, why not do some testing to see if the stock airbox is holding you back at all. Thats the only way you'll actually know.
Since it's so easy to switch from one set-up to the other, why not do some testing to see if the stock airbox is holding you back at all. Thats the only way you'll actually know.
04-18-2002, 09:56 AM
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Car: '87 IROC
Engine: LT1 350
Transmission: 700-R4
That's what I found extremely weird. TPI thirdgens have been around for at least 17 years and no one has done anything to improve the air flow. The Fourth gen lid is basically the same as the thirdgens and ALL fourthgenners dump that thing for a good CAI kit, and it nets 'em a couple tenths in the quarter too! Even the C5 vettes and LS1 F-bodies dump the stock lid. And to not see any tests on the Thirdgen Camaro lid, leaves me kinda scratching my head. I guess what i'll have to do is get myself a spare lid, cut it in half the long way, remove any support walls, or silencers in the damn thing, and seal it back together and drive my car that way to see if I pick up some top end. It really leaves me scrathing my head as to why no one's tried a CAI kit in a thirdgen yet...maybe cuz the stock TPI only flows well to 4500 so no one tried to really force more air into it?
04-18-2002, 11:39 AM
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Car: 04 GTO
Engine: LS1
Transmission: M12 T56
Originally posted by Markolc
It really leaves me scrathing my head as to why no one's tried a CAI kit in a thirdgen yet...maybe cuz the stock TPI only flows well to 4500 so no one tried to really force more air into it?
It really leaves me scrathing my head as to why no one's tried a CAI kit in a thirdgen yet...maybe cuz the stock TPI only flows well to 4500 so no one tried to really force more air into it?
If you want to make CAI, go for it. Just please get some back to back track testing or dyno numbers to show us the gain. Their is no bigger liar than the butt dyno.
And the thirdgen camaro intake has nothing in common with any LT1 cars intake. And the LS1 lid is restrictive mostly b/c of the stupid silencers GM built into it. The thirdgen camaro duct has no such restrictions. The only thing you can really help is to remove the wall at the outlet of the snorkels.
Last edited by Ed Maher; 04-18-2002 at 12:41 PM.
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04-18-2002, 01:00 PM
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Car: 2005 Subaru STI
Engine: 153ci of Turbo Power!
Transmission: 6-Speed
Well...
Mike Davis doesn't participate on the boards so his data doesn't "get around" that much. But, he DID do a dyno run comparing a custom 3" air induction setup to the stock Y-Airbox. This was on his hot-cammed ZZ4 with fully ported TPI (and I believe a 2" siamesed base). Guess what ... the TPI airbox won. I don't know how ... but, that's his data.
Tim
Mike Davis doesn't participate on the boards so his data doesn't "get around" that much. But, he DID do a dyno run comparing a custom 3" air induction setup to the stock Y-Airbox. This was on his hot-cammed ZZ4 with fully ported TPI (and I believe a 2" siamesed base). Guess what ... the TPI airbox won. I don't know how ... but, that's his data.
Tim
04-18-2002, 03:21 PM
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Car: 1988 Vette; 1988 IROC Z-28
Engine: 350cid; 305cid
Transmission: 700R/4; 700R/4
Axle/Gears: 2.59; 2.77
On a static dyno pull even the fan won't simulate a 1/4mi pass. You can see the O2 sensor readings drop near the traps (if you don't have it maxed out).
I didn't do back to back with the IROC (not so methodical back then) but tarp speed with the Vette went up about .5mph (5hp) from the ram-air over an open lid (similar to the IROC cut air boxes). Those numbers were normalized for weather conditions so are valid from week to week.
Just get some 4" dia flex Al tubing at Home Depot (4' is more than enough), form it to fit inside the cut air boxes (use A/C tape to make it air tight), run each down behind the cross piece in front of the radiator and out behind the fogs. There have been several posts here on how to form "scoops" down there, but I left mine open and just anchored them under the fog light hold downs. It's an interesting project, only costs a few $$ and can easilly be reversed. You will likely notice it pull a little harder in the 2nd 1/8 mi.
I didn't do back to back with the IROC (not so methodical back then) but tarp speed with the Vette went up about .5mph (5hp) from the ram-air over an open lid (similar to the IROC cut air boxes). Those numbers were normalized for weather conditions so are valid from week to week.
Just get some 4" dia flex Al tubing at Home Depot (4' is more than enough), form it to fit inside the cut air boxes (use A/C tape to make it air tight), run each down behind the cross piece in front of the radiator and out behind the fogs. There have been several posts here on how to form "scoops" down there, but I left mine open and just anchored them under the fog light hold downs. It's an interesting project, only costs a few $$ and can easilly be reversed. You will likely notice it pull a little harder in the 2nd 1/8 mi.
04-18-2002, 03:42 PM
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Car: 04 GTO
Engine: LS1
Transmission: M12 T56
Thanks tim. Did he borrow the 'desert nomad' special edition cold air kit, or did he make his own 
OK folks, the chips are on the table. An 11.9 car showed more power on the dyno w/ the stock airbox than w/ a custom cold air kit. It's not that hard to believe, even though it might be slightly pinched cros sectionally v.s a custom tubing set-up, it is a MUCH shorter and MUCH more direct path for the air to take to the TB. Turns are just as evil as loss of cross section when it comes to flow.
OK folks, the chips are on the table. An 11.9 car showed more power on the dyno w/ the stock airbox than w/ a custom cold air kit. It's not that hard to believe, even though it might be slightly pinched cros sectionally v.s a custom tubing set-up, it is a MUCH shorter and MUCH more direct path for the air to take to the TB. Turns are just as evil as loss of cross section when it comes to flow.
04-18-2002, 05:04 PM
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Car: 2005 Subaru STI
Engine: 153ci of Turbo Power!
Transmission: 6-Speed
Ed,
I think you basically hit the nail on the head. The stock airbox directs air RIGHT INTO the throttle body. Very nice. I have a custom 4" CAI that I will be testing once I get my car back together. I'll do back to back testing at the strip and look at mph. Just need to get this dam thing back together
t
I think you basically hit the nail on the head. The stock airbox directs air RIGHT INTO the throttle body. Very nice. I have a custom 4" CAI that I will be testing once I get my car back together. I'll do back to back testing at the strip and look at mph. Just need to get this dam thing back together
t
04-19-2002, 08:02 AM
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Car: 90 IROC
Engine: 406
Transmission: GMPP 93/4L60
Axle/Gears: 9 bolt 3.27
After my 406 swap I wondered how much the factory box was holding me back. I have K&NS with the buttom of the box cut off. So I replaced it with a 4" rubber boot at the tb, fit my 58mm pretty good, it was about 4" long, and stuck one of those K&n cone filters on it.
On a dynojet both setups made the same power. I know the cone would be sucking hot under hood air. But this test was done on a cool engine with the hood open, just to see if there was power to be had ditching the factory setup. On the street with the hood closed IM sure the results would have been different.
On a dynojet both setups made the same power. I know the cone would be sucking hot under hood air. But this test was done on a cool engine with the hood open, just to see if there was power to be had ditching the factory setup. On the street with the hood closed IM sure the results would have been different.
04-19-2002, 05:58 PM
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Car: 04 GTO
Engine: LS1
Transmission: M12 T56
Originally posted by MikeS
Only Camaros so far, anybody got info applying to a Firebird? I know, I know, I should just go do it myself..
Only Camaros so far, anybody got info applying to a Firebird? I know, I know, I should just go do it myself..
04-20-2002, 10:30 PM
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Car: 88 IROC
Engine: 5.7 RamJet
Transmission: T56
Axle/Gears: Dana44 4.10
Originally posted by Ed Maher
Well the firebird ducts are always going to be long and bent so you might as well make it with big smooth tubing.
Well the firebird ducts are always going to be long and bent so you might as well make it with big smooth tubing.
After the car is on the road I'll try some back to back 1/4 runs with stock setup, a K&N cone filter that just goes on the TB, and a custom CAI/Ram Air that I am working out for my 86 'bird.
04-21-2002, 10:55 PM
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One Firebirds I think the older TPI's air box isn't as good as the newer I think 88 and up for the TPIs. Make a CAI with like a 85-87 but the others I wouldn't mess with. I tried a cone filter in my 89 Formula and saw that it ran alot smoother but the car didn't pull through the gears as much, which I would guess loss of power. I think I'm just going to get a stock KN filter and drill a few moree holes in the box and it will be good from there. I don't got the time or money to do a dual Y setup yet, especially with the MAF senor and the goddam battery in the way.
04-22-2002, 01:45 AM
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Car: 1987 Trans Am GTA
Engine: Miniram'd 383, 24X LS1 PCM
Transmission: TH700R4, 4200 stall
Axle/Gears: 9", 4.33:1
Here is a description of what I am playing with for my MAF equipped GTA. It is utilizing the stock 88 and up Pontiac ducting with a 9" conical K&N on the end of it instead of the stock air box. Well, here is a copy of my description of what I am doing from that other thread:
Laterzzz,
Matt
I have an open element filter on my GTA right now that lives where the stock airbox used to be and it works well. I can certainly hear it from time to time. I added some 4" metal dryer ducting from Home Depot that pulls air off the air damn and that seemed to help a bit too.
I am currently having a friend weld a metal box together (8"x10"x8" with an open bottom) that will live where the stock air box used to. I have already used a 3" hole saw to drill four holes to cut open most of the battery tray on that right side and I have moved the ducting I made to direct the air up through that open area (instead of going up through the inner fender area and around the battery tray which adds unwanted turns). So the plan is to seal my 9" conical K&N open element in the box that I am having made and the ducting will pull the air off the air damn and pressurize it at speed making it a 'Ram Air' setup of sorts as well as a CAI. I suspect that the way I had it with the ducting coming off the air damn area just aimed at the K&N conical filter was working quite well as the filter had a nice round spot on it where it was much dirtier than the rest of it corresponding to where the duct was aimed. But this setup should be much better.
The only thing I would like to work on in the future is making the 'air box' that I am having made more useful on the inside for directing the flow - like make it NOT a box....lol. My plain box idea may provide somewhat of a gain in pressure for the engine to get it's air from, and really seal it so it won't get any hot air from under the hood, but it really won't be a true 'ram air'....
I am currently having a friend weld a metal box together (8"x10"x8" with an open bottom) that will live where the stock air box used to. I have already used a 3" hole saw to drill four holes to cut open most of the battery tray on that right side and I have moved the ducting I made to direct the air up through that open area (instead of going up through the inner fender area and around the battery tray which adds unwanted turns). So the plan is to seal my 9" conical K&N open element in the box that I am having made and the ducting will pull the air off the air damn and pressurize it at speed making it a 'Ram Air' setup of sorts as well as a CAI. I suspect that the way I had it with the ducting coming off the air damn area just aimed at the K&N conical filter was working quite well as the filter had a nice round spot on it where it was much dirtier than the rest of it corresponding to where the duct was aimed. But this setup should be much better.
The only thing I would like to work on in the future is making the 'air box' that I am having made more useful on the inside for directing the flow - like make it NOT a box....lol. My plain box idea may provide somewhat of a gain in pressure for the engine to get it's air from, and really seal it so it won't get any hot air from under the hood, but it really won't be a true 'ram air'....
Matt
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