Over 5 PSI on idle. Blow through charger
Turbo Mini Forums

Hi all

Am having a few issues with the final part of my rebuild. I have checked the pressure of the charge from the blower at idle and its sitting at over 5 PSI which is causing the fuel to blow back and not make it into the block. So the only way at the moment of having the engine to run is by removing the pipe above the I/c so the charge blows to atmosphere. i did get it to run for about 10 seconds with it all connected up before it just stalled. It sounded truly amazing!!

So any thoughts? Got a fuel pressure regulator en-route. Should have arrived last week but never did. Would this sort it? Guess i need to bleed off the boost at idle.

Any thoughts/ideas would be a great help

Thanks

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You might want to look at your pulley ratios... If making 5psi at idle, you'll be overspeeding the bugger by a long-way at 3/4 revs.

what sort of blow off valve are you using Jonny?
in theory, with the throttle plate shut (as it is at idle) there should be a vacuum in the inlet manifold, which will hold the DV open, thus venting the boost. then you press the throttle the charger will create boost in the inlet manifold, shutting the DV

If you've got the pulley ratios correct, it sounds like perhaps the spring in your DV is too strong and not opening fully at idle.

Are you using the sealed turbo carb? If so, then you definately need a rising rate fuel pressure reg for it to run properly.

Mr. Prawn, the friendly Crustacean- slowly making steps towards forced induction.

I'm going to be using an SSQV in my blow through build, as it works on equalising a pressure difference, rather than neding a vacuum source to pull it open. As a result, it can open fully with very little vacuum, and also will not leak boost even at it's weakest setting.

Mr. Prawn, the friendly Crustacean- slowly making steps towards forced induction.

Thanks for the help guys.

Im using a Bailey VTA type dump valve. When the pipe is removed from the I/C it revs very freely and is very responsive but connect it all up and it fires the fuel out a pipe at the side of the sealed turbo valve (pipe was removed at this point. Think its an oveflow pipe bit)!

The pulley im using is the same size as the one supplied in kit from my old VMax setup. It is a very short belt with no tensioner.

All running through a megajolt kit on v-power.

feature=mhum

You need some sort of actuated valve to divert boost under idle and part throttle conditions.

A normal turbo style dump valve will struggle with the air volume IMO.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Can you tell if the DV is opening at all on idle? is it venting anything/making a release type noise?

A guy from holland has done what you're trying to do, and he found that a forge 007p recirc valve was able to cope with the flow and stop boost rising completely, although he said it was a nightmare finding the right spring tension to allow it to open fully on idle, yet not be forced open at full boost. This is why I'm using an SSQV, as it eliminates the need for accurate spring setup in a piston type DV

Mr. Prawn, the friendly Crustacean- slowly making steps towards forced induction.

Are you sure that the SSQV will open under idle conditions?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I bloody well hope so, that's what I've been led to believe anyway. I was under the impression that due to the 2 chamber design, it tries to equalise the pressure in both chambers, meaning if there's vacuum in the inlet manifold, it should try to equalise the pressure on the charge side.

http://www.streetunit.com/v/vspfiles/photo...agrams_1-3.giff

if it fails, I'll have to try a forge and adjust spring tension I guess.

Edited by Prawn on 5th Oct, 2009.

Mr. Prawn, the friendly Crustacean- slowly making steps towards forced induction.

Looks to me as if that will seal at vaccum. Good for turbo, not for supercharger.

The blurb on the HKS site says it will hold closed at vacuum, which is when you need it open.

Edited by Paul S on 5th Oct, 2009.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

hmmmmmm. bugger. I was so sure that was going to work!

Ignore my above ramblings about the SSQV then!

Mr. Prawn, the friendly Crustacean- slowly making steps towards forced induction.

This is the sort of thing that I would use:

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Or buy a complete intake tube from a Ford thunderbird / Ford SuperCoupe, chop out the valve part, complete with actuator, and use that...

They are cheap as french fries to buy over here.

ssqv's are not open at idle. they cant be. theyre designed to work on cars with mas airflow meters, which if the valve is open under any curcumstance than dumping boost it will mess up the fueling and the engine will cut out. they operate in a similar way to a normal dump valve, with a very light (~1psi) pressure releif valve after the dump valve (if that makes sence) lol

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

What about this?

www.pettitracing.co.uk/supercharger.html

www.pettitracing.co.uk/images/bypass_valve.jpg

But is this a dump valve?

feature=mhum