Hypergear Turbochargers and High flow Services Development thread

[GTScotT]

Hey man going to be going to wsid on Sunday for the off street meet if you want to come should be good also no rush like wednesday nights cause it during the day

You should be in the 12s easy just try and get good rubber

yo, that sounds pretty good. I'll start seeing if I can make it.

How much will the day cost? Is it like weds nights where its $50?

[SimonR32]

Is that all!!

I hope i prove you guys wrong!! hahah

I guess you cant defy physics

What did you end up doing?

I think I raced you at one stage, you had the gopro on brake light? Should have been on the front of the car

[GTScotT]

Hey man going to be going to wsid on Sunday for the off street meet if you want to come should be good also no rush like wednesday nights cause it during the day

You should be in the 12s easy just try and get good rubber

Made the calls and cant make it for sunday man. Car has no rego and i got no one available to sign the UVP and take it down.

Let me know when you wanna go for a Wednesday night instead.

[Lithium]

If it needs to go to over 8000rpm it is pretty bad, sounds like it takes a while to come on in first gear but hard to tell. What blow off valve is that?

[hy_rpm]

Made the calls and cant make it for sunday man. Car has no rego and i got no one available to sign the UVP and take it down.

Let me know when you wanna go for a Wednesday night instead.

No worries man and yeah it's only $50 it's better on a Sunday as it from the morning so no rush cause it after work and they have it on Sunday once a month

[dori33]

should try swapping the diff for a auto 4.3 should help keep it in boost threshold

[copycutter]

If it needs to go to over 8000rpm it is pretty bad, sounds like it takes a while to come on in first gear but hard to tell. What blow off valve is that?

Lith if you mean Hanaldo's car I'm pretty sure it's no bov. That noise is reversion. Had the same thing setup on my car with a G3 and the old "coke can bov gasket" mod for giggles.

[Lithium]

Was wondering if that was it, sounded that way. Be very interesting to see if the performance improved without it compressor stalling on every shift....

[Lithium]

Was wondering if that was it, sounded that way. Be very interesting to see if the performance improved without it compressor stalling on every shift....

[copycutter]

Well if it would stop raining up here I could post up a video of between gear lag to youtube with the gopro

[GTScotT]

you think running no bov can have that drastic an effect? mine doesnt have one.. something I am missing you think?

[Lithium]

I don't know for sure, I am not enough of an animal to do that to a turbo so haven't tried the difference but I am picking there is a lot of deceleration when that happens. That will definitely be costing response, how much I don't know... but when you consider how much effort goes into improving response (manifold design, ball bearings, wheel design etc) by increasing the rate the rotating mass can accelerate it seems a bit redundant if you are actively decelerating it again by shutting the door on the pump whenever you aren't at full noise. The fact the surge noise goes away is because the compressor has slowed down enough that it is no longer surging when flowing down a path which will accept less air than the lowest surge line even mapped... Which can only mean the compressor must be back to cruise equivalent rpm at best.

If that is right, the turbo will be spinning slower than if you just cruised at set rpm then stepped on it... I don't know for sure but I would expect the response lost to be measureable.

[copycutter]

That was well written. I've read that the sound is generated not by the compressor "chopping" the air to create the fluttering noise, but rather the sound of air cavitating back and forth between the throttle body and the compressor when the throttle is snapped shut. If this is true then the sound may not be due to the forceful slowing of the compressor back to idle but rather just the supersonic pressure differential waves bouncing back and forth until the compressor spins down enough for the sound to not be audible itself. I don't know if this is true or whether your theory is true. I guess you'd need to run the test back to back on the same setup and time it to be exact.

[Lithium]

That is close enough to my theory to roll with.

Ever brake boosted? Ie, roll along at a set rpm - lean on the throttle and lean on the brake, just enough to stop the car from accelerating so to load up the engine enough to bring up boost without accelerating away... good for rolling races etc.

Try brake boosting in 4th gear (or whatever gear is safe for the rpm and conditions) then letting off the gas, see if it surges. Now go as low as possible before it doesn't surge when you back off the throttle - between engine rpm and the gauge pressure you are running at that point to not surge you should be able to get an idea of how much lower the shaft speed is relative to the engine rpm and gauge pressure you would have been running at 7000+rpm and full boost.

After that, then consider the amount of rpm the engine will be spinning at in the next gear and how quick the turbo would need to be spinning (relative to the "minimum surge" test) to supply the target boost pressure at those engine rpm and how much acceleration it would need to do to get there. I haven't, and can't do that test - so I'm not sure what to expect but I'd be surprised if you needed to go much (or at all) over 2000rpm/2psi to make surge against a closed throttle audible.

[GTScotT]

both posts are reason enough for me to try it.

I have a stock S14 bov at home that I will look into refitting. Hope it can hold 20psi tho..

[copycutter]

I think I've experienced compressor surge before, at least as I understand it. It feels and sounds totally different to backing off the throttle for the "zututu" fluttering sound effect.

Sometimes when rolling off heavy load and mid rpms with decent boost and no bov (from memory) the turbo kind of accelerates and decelerates in a semi violent and unstable way. It's very noticeable and totally different to snapping a throttle shut without a blow off valve.

[copycutter]

Like this effect I mean

Edit: Done some more reading and maybe both conditions are technically surge from an engineering point of view. Not sure, but I always regarded compressor surge as a rather substantial instability to a compressor's behaviour, and the "fluttering" more as reversion/cavitation.

[Lithium]

The types of surge you are describing are just far less violent surge than if you close the throttle. I know how you are looking at it, but it seems a bit like serious denial or something - surely you can see it is the same thing, just a very extreme version.

With a turbo there is no solid barrier to provide compression, it relies on aerodynamics to create a higher pressure down stream of the compressor - and assumes that the design of the overall system will ensure that whatever is downstream of the compressor will "accept" enough air to allow air to flow through and out the compressor to allow it to pass more air through it. If whatever is down stream doesn't flow enough at a given pressure you get a bit of a surge noise, which can get as bad as shown in that clip - depending on how bad it is will essentially cause how abrupt the noise is.

In the case of closing a throttle it isn't so much that downstream of the compressor isn't allowing enough air out of it to work right, there is NO airflow out of it. This pushes the compressor HARD into its surge line, the pressure ratio will be enormous and the flow will be miniscule - the compressor will have no option but to try and go to an rpm which matches that flow rate, and quickly. The only reprieve is the engine isn't pumping at full load and therefore trying to keep the turbo pumping back up again - it will just decelerate under an extreme surge condition until it is no longer surging... make it no less surgey, it just at least has an out.

[LANDSCRIBBLE]

i have a BOV on my car and its pretty much the same as martin's car in terms of gear change turbo response.

[copycutter]

Ok that makes sense, they are the same, except there's just difference in the rate of decel between the two surge types and so the forces the compressor is being exposed to are different.

Back to your above "minimum surge" test. What does it mean if surge is audibly induced at 2000rpm/2psi? Does it somehow indicate the gap in shaft speed the turbo has to make up if you went from 3rd to 4th at full noise?