i was driving around last night and i noticed for the first time that there is this noise as the secondary turbo comes on. its hard to describe the sound but it sounds kinda like BOOOOOOOOOOOOP except in a more "air sucking" sort of way. its not that long either. like i said, hard to describe. do any of your sequential people get he same sound (or a sound) when the second turbo kicks in? thanks!

 

I had had two FD's and none of them made that noise. The time that I could hear the turbos was because they were bad. Are you losing power? Do you have a boost gague?

 

i'm just wondering if the noise is just the second turbo kicking in cuz it happens right when it does. there was a thread a while back on my dynochart that shows a fluttering top end that people are attributing to ignition (for which i just picked up some new plugs to go in) but i don't think that's it. it doesn't feel like i'm losing any power other than the brief drop between the turbos (10-8-10). i have a boost gauge and boost appears to be holding steady though i haven't tried it out on a big clear straight so i could look at the boost gauge more.

 

I think that's just the noise u hear when the 2nd turbo comes online, because i also hear a noise.. it's probably normal.. don't worry about it if your boost is holding up..

 

its probably the VTEC kickin in....

 

VTEC BABY! my engine sound goes from lawn mower to weed whacker!

 

I get a similar noise, although its not just the secondary, I can hear it whenever the turbos spool up. Kind of a whiny sound, its not very noticeable but I can definitely hear it.

 

no, its not a whiney sound. i hear the whistling of the turbos all the time as they spin but this is a littlem momentary sound when the second turbo kick in. it lasts a fraction of a second kinda like someone farting.

 

I'd give the vacuum lines a good looking over - maybe you split one or it popped off?

Cheers,
Dave

http://go.to/rx7

 

My car farts fire!......

 

Just teasin" Hop you find the prob.Doesn't sound major if yur not noticing any boost decline.Maybe a loose hose....G

 

sounds like it may be the CHARGE RELEIF VALVE - it opens like a BLOW OFF VALVE during transition to allow the second turbo to spool up quicker, check that the discharge hose has not come loose from the airbox.

 

I hear a whistling sound, from the passenger's side of the dash prior to switchover. At first I thought it was the Power FC Commander beeping, but I don't think it's equipped with a beep speaker? I don't see or feel any boost lag, in fact the boost production is terrific. Just wondering if it's the J-spec twins wastegate solenoid duty cycles doing their thing? As you know the J-spec twins don't have pills to control boost. There's a solenoid that opens and closes the wastegate to bleed boost for boost control (which is controlled beautifully by the Power FC electronics, BTW). I have the Greddy Airinx dual intakes which is pretty noisy. Perhaps the whistling is coming from the intake? The groaning noise is probably the air pump...

 

Neokai - Are you certain of the RPM at which this noise happens? Are you sure it isn't at 2700 rpm? Do you have an aftermarket intake?

If it happens more at 2700 than 4500 and more under medium throttle rather than WOT - well then you are hearing the airpump releif valve - which has been dubbed the "moo fart". Sort a burbly "mooo".

It is normal. You can mulffle it.

If it is at WOT on the second turbo (4-5K rpm) then I'm stumped, and would like to hear any additional info you can provide on it.

 

I'm getting a moo fart noise after letting off a hard launch or a full throttle. After that, I can't even boost up pass 7lbs, like all my powers are gone, then it comes back after awhile... maybe it's my custom intake, cause the clamps are really loose..

 

neokai, its normal. I never heard it inside the car but when I dyno'd and stood next to it with the hood open I could. As someone said, its the CRV.

 

WOW this thread sure came back from the dead PS I gave the same CRV answer two months ago

 

it's the CRV CLOSING, not opening

 

During PRESPOOL it (the CRV) is open to dump pressure from the second turbo, as it is being fed exhaust by the Turbo Prespool Valve (TPV). ( the TPS is the primary means of BOOST control in Primary Turbo mode) The Charge Control Valve (CCV) is closed throughout primary turbo operation. Then during transition the CRV (and TPV) closes while the Turbo Control Valve (TCV) opens, this hapens just slightly before (about 1/2 sec) the CCV opens, in order to SURGE the turbo up to aprox 120,000 rpm (about 20-25% over normal operating speed) so it can instantly provide full boost when the CCV does open. This split second delay between the TCV opening and the CCV opening is what accounts for the 2psi dip in the Stock boost (10-8-10) pattern. The OPEN TCV robs some exhaust energy from the primary turbo before the secondary is providing Boost. With all these valve/flow changes happening is it any wonder there can be some strange wooshing & whistling noises during transition?

93BlackFD you are probably correct, from re-reading the description NEOAKI gave he is probably hearing the CRV CLOSE!. I hear a kind of farty whistle from 3.5>4k, from the CRV as the TPV vents exhaust to the secondary turbo to control primary boost.

 

TPV you can't hear

 

Savian - that is really a seperate thread - but it depending on how you are driving it could be normal - or else you have something wrong (I'm so helpful)

If you bring your RPM past 4500 and then let it go down, but not below 3000 or so, then you will still be in Twin turbo mode. If you let the RPM drop below 3000 the ECU resets to the primary turbo only. At 3300 rpm in 4th on both turbos it can take a long time to build full boost.

Once you know about this, it's pretty easy to adjust your shifting patterns.

 

Shouldn't really be able to hear the CRV close either, unlsess maybe it isn't connected to the airbox, or the valve is going bad. ???

 

I was recently testing my CRV; it was out of the car but still connected to the two larger hoses. With a vacuum applied to the small nipple (valve open), I blew into one of the large hoses (air came out the other one), then while I was blowing I removed the vacuum, thus closing the valve. The sound it made was very similar to what neokai described.