Whistling Intake

[LS1-450]

Since adding Weind intake & AFR 205 heads, my intake has been making a whistling sound when accelerating. Is this a sign of restrictive air flow? A/F ration is 12.8/12.9:1 through RPM range under WOT. Therefore, thought everything to be OK. Could there be a few HP lost to a restrictive filter?

Additional info.: Engine is a 99 LS1. Filter is a cone (MAC) 5.75" diameter @ the base, 5" diameter @ the top, & 5" long. Has a reverse cone in the end . Recorded 310 RWHP @ 5,400 RPM on a Mustang dyno. I think this would be about 365 RWHP on a dynojet. I don't know why the dyno operator shut her down @ 5,600 RPM as she was still making HP. Would like to have seen it run to @ least 6,000RPM.

Please comment. Thank-you.

[LS1-450]

Just found a filter good for up to 600 HP thay alows 1250 CFM of air flow. Bought it to replace the filter mentioned above. Am intersted to hear comments about the current set up. The numbers seem OK to me, but, the whistling has to be indicating a restriction. Thanks again.

[gnomee]

I have a 98 ls1 with no mods other than Aluminum flywheel and a K&N air filter and I got 313 RWHP and 322 FTLBS Tourque. Sounds like the dyno guy knows what he is doing. On my first run I ran it to 6000 and my HP took a nose dive at about 5,400. Anything past that was less. I'm not sure what you mean about mustang dyno. I thought a dyno was a dyno. My buddy ran his Mustang right after me on the same Dyno. I didn't see the guy change programs or anything on the computer.

[Zboner]

i just thought that noise was because the sound baffels were gone?

[LS1-450]

I have a 98 ls1 with no mods other than Aluminum flywheel and a K&N air filter and I got 313 RWHP and 322 FTLBS Tourque. Sounds like the dyno guy knows what he is doing. On my first run I ran it to 6000 and my HP took a nose dive at about 5,400. Anything past that was less. I'm not sure what you mean about mustang dyno. I thought a dyno was a dyno. My buddy ran his Mustang right after me on the same Dyno. I didn't see the guy change programs or anything on the computer.


There are two types of dynos that I know of. A Dynojet & a Mustang. Dynojet dyno's routinely produce numbers about 19% higher than a Mustang dyno. Can't speak for how that dyno was set up, but, the operator has done something to balance out the difference. Have never seen that before. I know guys who won't have their car run on a Mustang dyno because of the difference.

Anyway, with the heads & intake, my car should be in the 360-370 RWHP range. For example; you are bone stock w/a filter change & are @ 313RWHP.
Add the 205 heads flowing close to 280-300 CFM each compare to stock around 150 CFM each. This should produce numbers in the 370RWHP range shown. Only difference is the dyno. The heads are also the reason that my car builds power through 6,200 RPM. The dyno guy confirmed the difference between the Dynojet & a Mustang.

I think we can agree that with heads my car should make @ least 50 to 75 HP more than yours. The difference is in the dyno. The 12.8/12.9 A/F numbers are very good for producing safe power. Therefore, it's not a tuning issue. It must be the dyno.

[LS1-450]

i just thought that noise was because the sound baffels were gone?


Good point. Maybe that was adding to the sound. The whistling sound caused me to look into the effect of intake restrictions. Found that increasing the volumetric efficiency of the engine allows the engine to build more power with less work. Further, was suggested that the best chance to to build power & increase the engines VE on the intake side of things is to keep the intake restriction (pressure drop) @ or below 10 inches of water. Ran the numbers on my throttle body @ found it to be creating an 18 inches of water pressure drop. The MAF was creating a 24 inches of water pressure drop. If the filter that was whistling was rated @ 700CFM, then it was creating a 20 inches of water pressure drop. I have since ordered or modified parts so that none of the parts create more than a 10 inches of water pressure drop. Parts include an 1,100 CFM throttle body, 1,250 CFM filter, & I ported the MAF connectors (opening went from 72MM to 80MM).

We will see whether or not this was worth the effort & if the whistling was enhanced from having no sound baffles. I'll re-post after the TB & filter arrive. Throttle response is also an issue.

Thanks for the comments

[Zboner]

thats what i have just heard :think:

[LS1-450]

thats what i have just heard :think:

I don't have any experience with this intake manifold. What I meant was it will also be interesting to see if the sound baffling thing added to the whistling noise.

[Zboner]

i think that it would

[LS1-450]

OK, New filter, ported MAF, & throttle body installed. Throttle response is better. Whistles from about 10% through 25% throttle. Above 25%, whistle is gone. So, the removed sound baffling is causing the whistling (thanks Zboner). Thus far, have only gone to about 60% throttle. Wide band is showing good A/F ratios. After driving for a while will go WOT to see how the ECU reacts to the less restricted air flow @ MAX load. Am expecting for the A/F ration to be a bit leaner until the ECU adjusts to the change. Hopefully this will be the case.