Drift Tengoku — September 2004 · Page 250

Monday, August 16, 2004

The ‘back-turbo’ sound…

What mechanism produces it?

Drift… [heading fragment]

(4)

Secrets of those fascinating operating sounds

August issue

The back-turbo sound…

…airflow

5

The sound comes from…

Air with nowhere to go…

…hits the turbo blades, making a sound! [Previous issue's wording, challenged and clarified in this article.]

There are drawbacks too…

4007

The back-turbo sound becomes louder

C

What mechanism produces it?

…you know!

Load on the turbo… [fragment]

20

Recirculation-valve method

Additional explanation about this

…to [isolated fragment]

CW

Last month's page about fascinating operating sounds drew a large response, which makes us…

PARAGH

…very happy. However, the item ‘What mechanism produces the back-turbo sound?’…

…apparently lacked sufficient explanation. We received several comments…

…or inconvenienced, we sincerely apologize. We will take care to avoid this…

…received several corrections, so we clarify it here. To anyone who was confused…

EL9170

Part 1

…in the future.

About the mechanism producing back-turbo sound [historical correction article]

‘Our explanation certainly was insufficient…’

From the editors

‘I object to the explanation of what causes the sound!’

NEKO

Mr. Kaneko's…

‘…we apologize!’

The blowback and blade-interference noises described in August…

…are not necessarily wrong, but they are results…

…but the underlying cause is separate. Without explaining it…

…comment

Kaneko seems to be right. I think HKS, who explained it to us, said the same thing…

We apparently missed that point while listening. Sorry. We asked again and offer this correction.

‘The turbo's rotation stabilizes when it does work—that is, moves air. The original recirculation valve…’ [HKS explanation as published]

The article attributes the back-turbo sound to abnormally high turbo speed [historical explanation as published].

…the explanation is incomplete, isn't it? [Reader's critique.]

…is said [fragment]

‘…creates airflow in the intake pipe even with the throttle closed, letting the turbo perform a minimum…’

‘…amount of work and stabilize its rotation. What exactly makes the sound?’

…releasing the accelerator and closing the throttle makes the intake pipe's interior…

If the factory recirculation valve's return path to the air cleaner is closed off…

Air is supplied…

Abnormally high rotational speed

‘…because several factors interact, identifying just one…’

‘…a particular sound is hard to state categorically. However, the turbo's…’

The turbo does work by sending air, and that…

…becomes a closed space with no airflow .

‘…abnormal rotation is certainly the underlying cause…’

‘…not otherwise. Last month, when we wrote “the sound of air hitting the turbo,” we meant…’

…the turbo has no air to send, so the blades…

…the resistance disappears. Without resistance it whirs up to high speed… [reader's explanation as published].

…does not overspeed, they say. But when the throttle closes and no air enters… .

Shu-ta-ta-ta…

‘…in different words, I suppose…’

‘…the sound it produces. Kaneko and we were trying to describe the same phenomenon…’

‘The resulting sound is produced by the air and turbo inside the intake pipe…’

…increases. If you block a vacuum-cleaner or hair-dryer outlet, the motor… [historical analogy as published].

…the motor speeds up, doesn't it? The same principle, says the reader…

Do you understand now? However, the fact that it isn't good for the turbo…

‘…that's what happened.’ — Araki, HKS .

Abnormally high turbo speed causes…

…air-cutting noise, and when the throttle opens again, blowback noise…

‘…becomes more likely.’ [Shaft-wobble sentence continuation.]

‘…the warning that this is bad for the turbo is true; shaft wobble…’

What you do to produce the sound may be described correctly, but…

…is produced.

I think you understand things by learning the underlying principle.

Conclusion

Conclusion: the sound's cause was abnormally high turbo-blade speed! [Article's historical conclusion, translated as written.]

Part 2: canceling the RB engine's factory recirculation valve [historical modification discussion].

tre

Sg:

4

Paty

0

A2X

ASS

Soy

1

Nessspe

5

urdo

Tocls

Fos

lrert

2

Name [fragment]

‘Exactly as you pointed out! Everyone, be careful!’

From the editors

…will make many people misunderstand!

Insufficient explanation…

Koriyama, Fukushima

Email from…

Yukki

Yukki is right. Our explanation of this…

…was insufficient. Let us explain properly.

First look at photo 1: the factory RB intake pipe. You can see two hoses entering it…

…by hose. As Yukki says, this section is steel, and the two pipes are welded together with a steel ring…

…you can see. The thick hose goes to the recirculation valve, while the thin hose is the blow…

About page 67 of August's ‘How to Disable the Factory Recirculation Valve’…

…a comment about the RB engine: cap the pipe, remove… [reader's critique; fragmented wording].

…and joined as one. Remove one and the other comes away too. ‘What do we do here?’…

…is the issue you pointed out.

…remove it and seal with a plate. With that explanation, a reader might think, ‘I just need to cap…’

…it,’ or ‘remove it.’ Then the question becomes, ‘What about the return…’

The usual method shown in photo 2 inserts an aluminum plate in the factory recirculation-valve path to disable it, and… [historical description].

…cut the rubber hose and cap the opening. This disables recirculation without changing the air-cleaner-side piping… [historical description].

…pipe?’ Editors, your explanation is lacking! [Reader's critique.]

…there isn't enough explanation! Why didn't you say what to do with the return piping to the air cleaner?

…function. Photo 3 also shows inserting a plastic-bottle cap and clamping it tightly [historical improvised method].

…inexpensive, so perhaps recommended [historical editorial opinion].

…write that? Readers may remove the steel return piping too, or…

Modifying the steel pipe entering the intake is difficult, so the article suggests leaving it unchanged.

If this hose assembly is removed, the point where the recirculation hose enters the intake…

If the blowby hose remains functional, the article says the internal engine pressure won't increase in the way Yukki warns about.

…those who remove it may also affect the blowby return to the air cleaner…

…cap it. Those who cap it may be fine, but…

…says, sealing the blowby hose outlet is bad for the engine. You're right to point that out.

…is capped, and the blowby side can be connected through a catch tank using a new hose. As Yukki… [historical description].

…because they are combined on the RB, that also means the exhaust-side cam…

…cover nipple) is capped too. On the air-cleaner side…

…future issues.

We learned a lot from this. Thank you, Yukki. We'll use this experience when creating…

…cap with a suitable bolt. Then the engine becomes a vacuum… .

…condition, beginning oil-related trouble . You should explain it properly…

Conclusion

Turbo side

…wouldn't that be better? [critique fragment]

…may be removed, but keep the blowby hose functional!

The hose from the factory recirculation valve…

Air cleaner

This method confines the work to the top of the engine…

Cut the piping and insert a plastic-bottle cap or C-size battery to disable it; secure with cable ties or a hose clamp [historical improvised method described in the magazine].

This is where the two pipes…

…but…

…so it is simple and commonly used, says the article. The photo uses both an aluminum plate and a cap…

…either one can disable the recirculation…

Blowby hose

…are joined

…[wording incomplete; continuation elsewhere].

The two pipes are welded together. If the factory piping is removed…

2

…function [historical description].

1 [photo marker]

…remove this; cap the recirculation…

…side, while the blowby side…

…must be connected to the engine with a new hose.

…the 29 version matches the RB engine's…

This is a cap sold by HKS…

…fits the recirculation valve exactly [caption continuation].

To the recirculation valve

…must be reconnected [historical description; sentence fragments].

…valve. Two cost ¥1,050 [historical price].

248