Open lid?

[KILLSHOTS]

Hey guys,

Marc seems to feel that there is no real benefit to going with an open air filter lid. I certainly trust Marc, but I also know that there are a lot of you guys who run them. I can't really imagine the stock vented lid being a bottleneck. What are your thoughts?

[Kevin]

I have an open lid, no idea if it helps or not

[PhillipsLT5]

I have a open lid, Locobob did a dyno test some years back, seem to remember SLP Claw being the best HP

[GOLDCYLON]

I have an open lid as well.

[Karl]

It's free and it increases the surface area that the engine can suck in fresh air.

Goldcylon, do you have a link or the dyno numbers to share?

[GOLDCYLON]

It's free and it increases the surface area that the engine can suck in fresh air.

Goldcylon, do you have a link or the dyno numbers to share?


yes this is what locobob posted up over at Corvette forum many years ago.

locobob

Here is the old post from the CF. Results for peak HP were within margin of error but notice the average HP and Torque numbers show a small gain.

Today myself and forum member/dyno owner TJ Wong set out to find the truth regarding C4 air intakes. We dyno tested 3 different air intakes on my Lingenfelter 368cid LT5. Tested today were: stock with paper element, stock with K&N element and a cut lid, and finally SLP's "claw" tri-cone filter design. All dyno pulls were made with starting coolant temps at 195 degrees F. Here are the results.

Stock with paper, two identical pulls: 477rwhp. Avg. peak HP 477

Stock with K&N and cut lid, three pulls: 471, 475, 480rwhp. Avg. peak HP 475.3

SLP tri-cone "claw", three pulls: 477, 478, 481rwhp. Avg. peak HP 478.7
It would appear that the naysayers are mostly correct about C4 air intakes, not much to be gained here. Both Tom and I were rather suprised with the results. We had expected to see some small but visible gains with the cut-lid and SLP, instead we got a bunch of tests with peak numbers being basically the same or well within normal dyno pull to pull variation. The SLP unit does seem to have a small advantage over the others but suprisingly it's in mid range power not peak (see dyno graph average power #'s).

Sorry folks the image of the Dyno Graph is NLA

[Karl]

Seems odd with the k&n and cut lid combo the horsepower started low and kept climbing. I like the 480 number...seems more realistic. If it made 480 once it can make 480 again.

[KILLSHOTS]

I think my theory on the C4 in general has always been that the bottleneck is the filter itself, not the lid. In essence, open the lid more and the air still gets held up at the filter itself. Since we can't really increase the flow through the filter (a K&N doesn't flow better than a clean stock filter, for instance) I question whether we really increase airflow by a worthwhile margin by going from a vented lid to a full-open lid. That said, I'm totally open to being shown otherwise and I would definitely switch to an open lid for a few HP and better breathing characteristics overall.

Has anybody ever noticed a difference in intake noise when switching from stock to open? Maybe that would indicate a difference in airflow.

[Karl]

Yes there is a obvious sucking/suction noise when the throttle is opened.

[PhillipsLT5]

All I hear is LT5 music