THE ROVER SD1 FORUM

rod baker · SD1 User Joined: 10 Feb 2008 Posts: 37

hi all my sdi 3500 wistles from inside the intake some where had it apart cleaned it all out and now it idles well but still a whistle at gentl acceleration any more or less throttle and it changes pitch and fades away
any ideas thanks
rod

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1982 sd1 se 3500 runs reasonable lots of electrical gremlins was real cheap and lots of fun

Lehto · Posted: Sat Feb 23, 2008 4:32 pm Post subject:

Its the throttle body. Have you polished it? My 200 started doing it also when i polished the throttle body.

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Owner of 3 Rovers and 1 MG.

rod baker · SD1 User Joined: 10 Feb 2008 Posts: 37

i am not sure what is doing it, but it does sound like it coming from inside
it has had alot of work done to it but just what i do no know.
Rod

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1982 sd1 se 3500 runs reasonable lots of electrical gremlins was real cheap and lots of fun

ramon alban · Posted: Sun Feb 24, 2008 1:54 pm Post subject: Re: interesting

rod baker wrote:

i am not sure what is doing it, but it does sound like it coming from inside
it has had alot of work done to it but just what i do no know.
Rod

Hello Rod, Lehto's suggestion is worthy of investigation.

If your throttle assy has a throttle stop try adjusting it a tad and compensating the slight increase in idle speed with the idle speed adjuster.

Some Rover manuals (not the Twin Plenum) call for a specified gap of a few thou' between the throttle disc and the throttle body, to prevent the disc binding in the tunnel.

Clearly the high vacuum at idle is the energy source of the whistle.

If you are sure there are no external airleaks into the plenum, you could safely ignore it and just sing along in tune with the music.

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Ramon

Lehto · Posted: Sun Feb 24, 2008 2:00 pm Post subject:

I think the polished throttle does it because the surface roughness nolonger makes small turbulences and the throttle body starts working like a whistle. But I dont care about the sound... its just bit wierd because people sometimes start asking if theres a turbo.

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Owner of 3 Rovers and 1 MG.

rod baker · SD1 User Joined: 10 Feb 2008 Posts: 37

yeah im hearing you all my major concern is its possible that its something that will fail its not whistling at idle does it under gentle acceleration only
rod

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1982 sd1 se 3500 runs reasonable lots of electrical gremlins was real cheap and lots of fun

ramon alban · Posted: Sun Feb 24, 2008 4:24 pm Post subject: Re: annoying whistle

rod baker wrote:

yeah im hearing you all my major concern is its possible that its something that will fail its not whistling at idle does it under gentle acceleration only
rod

Yup, my misunderstanding there - sorry about that!

So tuneful under mild acceleration???

May still indicate something going on in the tunnel, or the inlet pipe or the AFM as the air flow reaches a particular speed to set up the audible resonance, OR the mild airflow affects an external air leak somehow.

The big problem is tracking it down whilst its happening??? SO:

Set he car on axle rear stands, place the wife in the driving seat and pretend to drive under gentle acceleration whilst you investigate what is actually going on in the engine bay. Wriggle all the pipes/tubes, adjust settings see if you can change/stop the resonance. ALSO is it really a whistle or a damaging whine??

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Ramon

rod baker · SD1 User Joined: 10 Feb 2008 Posts: 37

i have had it on my hoist and played with it tweaking the throttle will bring about the whistle and its definately a whistle not a grind
if i pull off the intake between airflow meter and throttle body it changes pitch but i can not find it .
it always seems on the other side or under the manifold which makes me wonder if it from inside the throttle body
rod

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1982 sd1 se 3500 runs reasonable lots of electrical gremlins was real cheap and lots of fun

KwS · Posted: Mon Feb 25, 2008 12:06 pm Post subject:

do you use a pod/cone filter of sorts? Mine whistles now that i put one of them on, but didnt do it with the stock intake.

Apparently its something to do with the air being pulled through the small gap as the throttle plate opens...?

ramon alban · Posted: Mon Feb 25, 2008 5:51 pm Post subject: Re: re whistle

rod baker wrote:

i have had it on my hoist and played with it tweaking the throttle will bring about the whistle and its definately a whistle not a grind

Now this is beginning to look (or sound) like being on the horns of a dilemma.

You have clearly eliminated everything but found nothing.

In which case some lateral thinking based upon your description.

if i pull off the intake between airflow meter and throttle body it changes pitch but i can not find it .

This means the engine continues to run with the inlet pipe removed??
Now thats interesting!! presumably only at idle because obviously the AFM Flap cannot signal the ECU if it does not deflect.

But the whistle is still there?

it always seems on the other side or under the manifold which makes me wonder if it from inside the throttle body

Clearly that is the case so how deep into the manifold to look?

1 the metal to metal joint between the plenum and the trumpet housing.

2 likewise between the trumpet housing and the inlet manifold.

3 overrun valve - if fitted being held slightly open with debris.

4 the idle air gallery has some minor restriction causing the resonance.

5 The EAV or one of its pipes has a similar intrusion

6 likewise the one way valve between the plenum chamber and the brake vacuum pipe.

7 A minute split in one of the plenum pipes.

After that lot - I would have to say i'm fresh out of ideas so it will definitely be an education to find out the actualitaire when you eventuality track it down.

Then of course you might be forced to take the view that if its only a whistle and not a grind, does it matter??

Enquiring minds need to know!

Ramon

rod baker · SD1 User Joined: 10 Feb 2008 Posts: 37

just a couple of things to note that i thought not relevant but that were mention last post
with air duct removed from throttle body mine still runs but a lil rough as do not have a flapper any more i have an intake air temp sensor mounted in a 12 inch length of exhaust pipe and i am running a mega squirt ecu which has a map sensor .
i am contemplating stripping down the throttle body and and giveing a lite sand blasting in side and out to improve looks and tosea if i can change minor flow character istics to eliminate the whistle i will while i am there remove intake completely and replace all gaskets.
now i have heard reference to intake trumpets i have had the plenum of and there were none there which is where i thought they were.
can some one educate me here
and i apoligise about all the posts but i am determined to get her all up and working .and as it was someone else toy and they have fiddled with it a lot its hard to know what is done .
thanks all

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1982 sd1 se 3500 runs reasonable lots of electrical gremlins was real cheap and lots of fun