15 replies to this topic

[strebblo]

I've done a search but not turned up anything relevant.

I've put the original (to this engine anyway) carb back on (a HIF38) and removed the old HS4 (from my old 998). It's a hell of a lot better than the old HS4, but I've noticed a whistling noise from it at about 3/4 pedal travel. If you put your foot down totally, it goes, but lift your foot up again slightly and the noise returns.

I had the same noise with the old HS4 (but it was very knackered so not surprised), except that was about 1/2 way through the pedal travel and you lost power if you stay in that part of the rev range. I don't think this is the case with the HIF38.

Does anyone know what the noise is, or what it indicates?

Just to sum up & try to avoid confusion -

The tempororary knackered carb = HS4, now off.
The original newer carb= HIF38 now on the engine, a late 1275.

Thanks chaps...

[Bungle]

could it be a air leak ?

[strebblo]

Oh yeah, that was the other thing!

On the HS4, it was just old and very cr@p, so I sort of suspected it to be leaking air in, but not so much on the HIF.

What I forgot, was to say there's a hole on the RH side (throttle link side) above the throttle link, just under the dashpot. It's obviously doing something, because if I put my finger on it, the engine dies, and if not, it runs ok.

Wossit for?!!!

[Big_Adam]

If you fitted a cone filter .... or did you go with the replacement?

Well with a cone you get a massive amount of noise. I used to be able to do the Darth Vader sound with the throttle.

edit

Hole you say? Little hole (2-3mm ish) or big hole (6-7mm)?

Edited by Big_Adam, 26 November 2007 - 05:09 PM.

[strebblo]

I know what you mean about the noise. I've now gone from the round K&N replacement element, to the JR cone (only because I didn't try to fit the elbow from HS4 to HIF38) which does make a nice noise, but it's not the same. As I say, I had the same type of whistle from the HS4, on both engines, that sound moved with the carb, and is now in a different place with the HIF now in place.

Think turbo diesel at high revs (for a diesel anyway) and thats the sound.

Hole - Yeah, 5-6mm or so. Not a crack type of hole - it's machined and look like itshould be there, but if it's for a breather hose there's no protruding brass tube like you get on all the other carb hose attatchments.

Does that make sense.... if so, that's a first for me

[strebblo]

This will just be easier witha photo won't it?! Give me 5 minutes, and I'll be back...

[strebblo]

ere go - huge'normous pictures:

 carb_hole1.jpg   229.43K   13 downloads

 carb_hole2.jpg   67.69K   12 downloads

[strebblo]

So can anyone tell me what the hole is? HBOL is not at all helpful here, nor is the SU HIF pdf I have - but it's not the full manual.

I don't think the hole below and behind that is anything either, but if anyoe can tell me about that too that would be useful. Thanks.

[strebblo]

"Boing!" Said strebblo...
The others just turned around and stared at his outburst.

Here's where you all chime in: ....

[Big_Adam]

Not a clue,

Well you got a breather, you got fuel and a overflow fuel pipe.

.....

I'd block the holw up. Bit of resin, take the dashpot off and block one end with some tape, drop of resin down the hole then wait for it to set.

Thats if it goes straight into the carb as a vac feed.

[Matt]

i do have one of those on mine.. but its blocked (i.e it looks like it came from the factory blocked)

[strebblo]

Thanks guys - much appreciated. I'd just love to know what it was for, as it came with the engine and although it runs fine with it open, if I block it wiv me finger, it dies when idling.

Out of interest does anyone have this connected to something - is it a gas/emissions sampling inlet?

[Matt]

bung a blob of bluetac on it and try and start the car. see if it idles to start...

[strebblo]

Worth a go I guess. It's sooo annoying that it isn't mentioned in the manual. I guess I'll need an SU manual to find it really.

[Bristolboy]

I have the same noise on my 998, it sounds more like a turbo whistling, (non turbo)

sorry i can't help, but when you find out what it is, could you let me know please, ta


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